Sample records for ice cover based

  1. Reconstructing lake ice cover in subarctic lakes using a diatom-based inference model

    NASA Astrophysics Data System (ADS)

    Weckström, Jan; Hanhijärvi, Sami; Forsström, Laura; Kuusisto, Esko; Korhola, Atte

    2014-03-01

    A new quantitative diatom-based lake ice cover inference model was developed to reconstruct past ice cover histories and applied to four subarctic lakes. The used ice cover model is based on a calculated melting degree day value of +130 and a freezing degree day value of -30 for each lake. The reconstructed Holocene ice cover duration histories show similar trends to the independently reconstructed regional air temperature history. The ice cover duration was around 7 days shorter than the average ice cover duration during the warmer early Holocene (approximately 10 to 6.5 calibrated kyr B.P.) and around 3-5 days longer during the cool Little Ice Age (approximately 500 to 100 calibrated yr B.P.). Although the recent climate warming is represented by only 2-3 samples in the sediment series, these show a rising trend in the prolonged ice-free periods of up to 2 days. Diatom-based ice cover inference models can provide a powerful tool to reconstruct past ice cover histories in remote and sensitive areas where no measured data are available.

  2. Astrobiology of Antarctic ice Covered Lakes

    NASA Astrophysics Data System (ADS)

    Doran, P. T.; Fritsen, C. H.

    2005-12-01

    Antarctica contains a number of permanently ice-covered lakes which have often been used as analogs of purported lakes on Mars in the past. Antarctic subglacial lakes, such as Lake Vostok, have also been viewed as excellent analogs for an ice covered ocean on the Jovian moon Europa, and to a lesser extend on Mars. Lakes in the McMurdo Dry Valleys of East Antarctica have ice covers that range from 3 to 20 meters thick. Water salinities range from fresh to hypersaline. The thinner ice-covered lakes have a well-documented ecology that relies on the limited available nutrients and the small amount of light energy that penetrates the ice covers. The thickest ice-covered lake (Lake Vida in Victoria Valley) has a brine beneath 20 m of ice that is 7 times sea water and maintains a temperature below -10 degrees Celsius. This lake is vastly different from the thinner ice-covered lakes in that there is no communication with the atmosphere. The permanent ice cover is so thick, that summer melt waters can not access the sub-ice brine and so the ice grows from the top up, as well as from the bottom down. Brine trapped beneath the ice is believed to be ancient, stranded thousands of years ago when the ice grew thick enough to isolate it from the surface. We view Lake Vida as an excellent analog for the last aquatic ecosystem to have existed on Mars under a planetary cooling. If, as evidence is now increasingly supporting, standing bodies of water existed on Mars in the past, their fate under a cooling would be to go through a stage of permanent ice cover establishment, followed by a thickening of that ice cover until the final stage just prior to a cold extinction would be a Lake Vida-like lake. If dust storms or mass movements covered these ancient lakes, remnants may well be in existence in the subsurface today. A NASA Astrobiology Science and Technology for Exploring Planets (ASTEP) project will drill the Lake Vida ice cover and access the brine and sediments beneath in

  3. Modeling ocean wave propagation under sea ice covers

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Shen, Hayley H.; Cheng, Sukun

    2015-02-01

    Operational ocean wave models need to work globally, yet current ocean wave models can only treat ice-covered regions crudely. The purpose of this paper is to provide a brief overview of ice effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea ice can be classified as: landfast ice zone, shear zone, and the marginal ice zone. All ice covers attenuate wave energy. Only long swells can penetrate deep into an ice cover. Being closest to open water, wave propagation in the marginal ice zone is the most complex to model. The physical appearance of sea ice in the marginal ice zone varies. Grease ice, pancake ice, brash ice, floe aggregates, and continuous ice sheet may be found in this zone at different times and locations. These types of ice are formed under different thermal-mechanical forcing. There are three classic models that describe wave propagation through an idealized ice cover: mass loading, thin elastic plate, and viscous layer models. From physical arguments we may conjecture that mass loading model is suitable for disjoint aggregates of ice floes much smaller than the wavelength, thin elastic plate model is suitable for a continuous ice sheet, and the viscous layer model is suitable for grease ice. For different sea ice types we may need different wave ice interaction models. A recently proposed viscoelastic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various ice covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea ice types, previous wave ice interaction models, wave attenuation mechanisms, the methods to calculate wave reflection and transmission between different ice covers, and the effect of ice floe breaking on shaping the sea ice morphology

  4. Leads in Arctic pack ice enable early phytoplankton blooms below snow-covered sea ice

    PubMed Central

    Assmy, Philipp; Fernández-Méndez, Mar; Duarte, Pedro; Meyer, Amelie; Randelhoff, Achim; Mundy, Christopher J.; Olsen, Lasse M.; Kauko, Hanna M.; Bailey, Allison; Chierici, Melissa; Cohen, Lana; Doulgeris, Anthony P.; Ehn, Jens K.; Fransson, Agneta; Gerland, Sebastian; Hop, Haakon; Hudson, Stephen R.; Hughes, Nick; Itkin, Polona; Johnsen, Geir; King, Jennifer A.; Koch, Boris P.; Koenig, Zoe; Kwasniewski, Slawomir; Laney, Samuel R.; Nicolaus, Marcel; Pavlov, Alexey K.; Polashenski, Christopher M.; Provost, Christine; Rösel, Anja; Sandbu, Marthe; Spreen, Gunnar; Smedsrud, Lars H.; Sundfjord, Arild; Taskjelle, Torbjørn; Tatarek, Agnieszka; Wiktor, Jozef; Wagner, Penelope M.; Wold, Anette; Steen, Harald; Granskog, Mats A.

    2017-01-01

    The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms beneath ponded sea ice during summer, indicating that satellite-based Arctic annual primary production estimates may be significantly underestimated. Here we present a unique time-series of a phytoplankton spring bloom observed beneath snow-covered Arctic pack ice. The bloom, dominated by the haptophyte algae Phaeocystis pouchetii, caused near depletion of the surface nitrate inventory and a decline in dissolved inorganic carbon by 16 ± 6 g C m−2. Ocean circulation characteristics in the area indicated that the bloom developed in situ despite the snow-covered sea ice. Leads in the dynamic ice cover provided added sunlight necessary to initiate and sustain the bloom. Phytoplankton blooms beneath snow-covered ice might become more common and widespread in the future Arctic Ocean with frequent lead formation due to thinner and more dynamic sea ice despite projected increases in high-Arctic snowfall. This could alter productivity, marine food webs and carbon sequestration in the Arctic Ocean. PMID:28102329

  5. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    DTIC Science & Technology

    2013-09-30

    Sea Ice , and the Ice Albedo Feedback in a...COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Sunlight, Sea Ice , and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover 5a...during a period when incident solar irradiance is large increasing solar heat input to the ice . Seasonal sea ice typically has a smaller albedo

  6. Arctic multiyear ice classification and summer ice cover using passive microwave satellite data

    NASA Technical Reports Server (NTRS)

    Comiso, J. C.

    1990-01-01

    Passive microwave data collected by Nimbus 7 were used to classify and monitor the Arctic multilayer sea ice cover. Sea ice concentration maps during several summer minima are analyzed to obtain estimates of ice floes that survived summer, and the results are compared with multiyear-ice concentrations derived from these data by using an algorithm that assumes a certain emissivity for multiyear ice. The multiyear ice cover inferred from the winter data was found to be about 25 to 40 percent less than the summer ice-cover minimum, indicating that the multiyear ice cover in winter is inadequately represented by the passive microwave winter data and that a significant fraction of the Arctic multiyear ice floes exhibits a first-year ice signature.

  7. Flow structure at an ice-covered river confluence

    NASA Astrophysics Data System (ADS)

    Martel, Nancy; Biron, Pascale; Buffin-Bélanger, Thomas

    2017-04-01

    River confluences are known to exhibit complex relationships between flow structure, sediment transport and bed-form development. Flow structure at these sites is influenced by the junction angle, the momentum flux ratio (Mr) and bed morphology. In cold regions where an ice cover is present for most of the winter period, the flow structure is also likely affected by the roughness effect of the ice. However, very few studies have examined the impact of an ice cover on the flow structure at a confluence. The aims of this study are (1) to describe the evolution of an ice cover at a river confluence and (2) to characterize and compare the flow structure at a river confluence with and without an ice cover. The field site is a medium-sized confluence (around 40 m wide) between the Mit is and Neigette Rivers in the Bas-Saint-Laurent region, Quebec (Canada). The confluence was selected because a thick ice cover is present for most of the winter allowing for safe field work. Two winter field campaigns were conducted in 2015 and 2016 to obtain ice cover measurements in addition to hydraulic and morphological measurements. Daily monitoring of the evolution of the ice cover was made with a Reconyx camera. Velocity profiles were collected with an acoustic Doppler current profiler (ADCP) to reconstruct the three-dimensional flow structure. Time series of photographs allow the evolution of the ice cover to be mapped, linking the processes leading to the formation of the primary ice cover for each year. The time series suggests that these processes are closely related with both confluence flow zones and hydro-climatic conditions. Results on the thickness of the ice cover from in situ measurements reveal that the ice thickness tends to be thinner at the center of the confluence where high turbulent exchanges take place. Velocity measurements reveal that the ice cover affects velocity profiles by moving the highest velocities towards the center of the profiles. A spatio

  8. Arctic multiyear ice classification and summer ice cover using passive microwave satellite data

    NASA Astrophysics Data System (ADS)

    Comiso, J. C.

    1990-08-01

    The ability to classify and monitor Arctic multiyear sea ice cover using multispectral passive microwave data is studied. Sea ice concentration maps during several summer minima have been analyzed to obtain estimates of ice surviving the summer. The results are compared with multiyear ice concentrations derived from data the following winter, using an algorithm that assumes a certain emissivity for multiyear ice. The multiyear ice cover inferred from the winter data is approximately 25 to 40% less than the summer ice cover minimum, suggesting that even during winter when the emissivity of sea ice is most stable, passive microwave data may account for only a fraction of the total multiyear ice cover. The difference of about 2×106 km2 is considerably more than estimates of advection through Fram Strait during the intervening period. It appears that as in the Antarctic, some multiyear ice floes in the Arctic, especially those near the summer marginal ice zone, have first-year ice or intermediate signatures in the subsequent winter. A likely mechanism for this is the intrusion of seawater into the snow-ice interface, which often occurs near the marginal ice zone or in areas where snow load is heavy. Spatial variations in melt and melt ponding effects also contribute to the complexity of the microwave emissivity of multiyear ice. Hence the multiyear ice data should be studied in conjunction with the previous summer ice data to obtain a more complete characterization of the state of the Arctic ice cover. The total extent and actual areas of the summertime Arctic pack ice were estimated to be 8.4×106 km2 and 6.2×106 km2, respectively, and exhibit small interannual variability during the years 1979 through 1985, suggesting a relatively stable ice cover.

  9. Evaporation of ice in planetary atmospheres - Ice-covered rivers on Mars

    NASA Technical Reports Server (NTRS)

    Wallace, D.; Sagan, C.

    1979-01-01

    The existence of ice covered rivers on Mars is considered. It is noted that the evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. It is determined that even with a mean Martian insolation rate above the ice of approximately 10 to the -8th g per sq cm/sec, a flowing channel of liquid water will be covered by ice which evaporates sufficiently slowly that the water below can flow for hundreds of kilometers even with modest discharges. Evaporation rates are calculated for a range of frictional velocities, atmospheric pressures, and insolations and it is suggested that some subset of observed Martian channels may have formed as ice-choked rivers. Finally, the exobiological implications of ice covered channels or lakes on Mars are discussed.

  10. Water quality observations of ice-covered, stagnant, eutrophic water bodies and analysis of influence of ice-covered period on water quality

    NASA Astrophysics Data System (ADS)

    sugihara, K.; Nakatsugawa, M.

    2013-12-01

    The water quality characteristics of ice-covered, stagnant, eutrophic water bodies have not been clarified because of insufficient observations. It has been pointed out that climate change has been shortening the duration of ice-cover; however, the influence of climate change on water quality has not been clarified. This study clarifies the water quality characteristics of stagnant, eutrophic water bodies that freeze in winter, based on our surveys and simulations, and examines how climate change may influence those characteristics. We made fixed-point observation using self-registering equipment and vertical water sampling. Self-registering equipment measured water temperature and dissolved oxygen(DO).vertical water sampling analyzed biological oxygen demand(BOD), total nitrogen(T-N), nitrate nitrogen(NO3-N), nitrite nitrogen(NO2-N), ammonium nitrogen(NH4-N), total phosphorus(TP), orthophosphoric phosphorus(PO4-P) and chlorophyll-a(Chl-a). The survey found that climate-change-related increases in water temperature were suppressed by ice covering the water area, which also blocked oxygen supply. It was also clarified that the bottom sediment consumed oxygen and turned the water layers anaerobic beginning from the bottom layer, and that nutrient salts eluted from the bottom sediment. The eluted nutrient salts were stored in the water body until the ice melted. The ice-covered period of water bodies has been shortening, a finding based on the analysis of weather and water quality data from 1998 to 2008. Climate change was surveyed as having caused decreases in nutrient salts concentration because of the shortened ice-covered period. However, BOD in spring showed a tendency to increase because of the proliferation of phytoplankton that was promoted by the climate-change-related increase in water temperature. To forecast the water quality by using these findings, particularly the influence of climate change, we constructed a water quality simulation model that

  11. The Relationship Between Arctic Sea Ice Albedo and the Geophysical Parameters of the Ice Cover

    NASA Astrophysics Data System (ADS)

    Riihelä, A.

    2015-12-01

    The Arctic sea ice cover is thinning and retreating. Remote sensing observations have also shown that the mean albedo of the remaining ice cover is decreasing on decadal time scales, albeit with significant annual variability (Riihelä et al., 2013, Pistone et al., 2014). Attribution of the albedo decrease between its different drivers, such as decreasing ice concentration and enhanced surface melt of the ice, remains an important research question for the forecasting of future conditions of the ice cover. A necessary step towards this goal is understanding the relationships between Arctic sea ice albedo and the geophysical parameters of the ice cover. Particularly the question of the relationship between sea ice albedo and ice age is both interesting and not widely studied. The recent changes in the Arctic sea ice zone have led to a substantial decrease of its multi-year sea ice, as old ice melts and is replaced by first-year ice during the next freezing season. It is generally known that younger sea ice tends to have a lower albedo than older ice because of several reasons, such as wetter snow cover and enhanced melt ponding. However, the quantitative correlation between sea ice age and sea ice albedo has not been extensively studied to date, excepting in-situ measurement based studies which are, by necessity, focused on a limited area of the Arctic Ocean (Perovich and Polashenski, 2012).In this study, I analyze the dependencies of Arctic sea ice albedo relative to the geophysical parameters of the ice field. I use remote sensing datasets such as the CM SAF CLARA-A1 (Karlsson et al., 2013) and the NASA MeaSUREs (Anderson et al., 2014) as data sources for the analysis. The studied period is 1982-2009. The datasets are spatiotemporally collocated and analysed. The changes in sea ice albedo as a function of sea ice age are presented for the whole Arctic Ocean and for potentially interesting marginal sea cases. This allows us to see if the the albedo of the older sea

  12. Sensitivity of Great Lakes Ice Cover to Air Temperature

    NASA Astrophysics Data System (ADS)

    Austin, J. A.; Titze, D.

    2016-12-01

    Ice cover is shown to exhibit a strong linear sensitivity to air temperature. Upwards of 70% of ice cover variability on all of the Great Lakes can be explained in terms of air temperature, alone, and nearly 90% of ice cover variability can be explained in some lakes. Ice cover sensitivity to air temperature is high, and a difference in seasonally-averaged (Dec-May) air temperature on the order of 1°C to 2°C can be the difference between a low-ice year and a moderate- to high- ice year. The total amount of seasonal ice cover is most influenced by air temperatures during the meteorological winter, contemporaneous with the time of ice formation. Air temperature conditions during the pre-winter conditioning period and during the spring melting period were found to have less of an impact on seasonal ice cover. This is likely due to the fact that there is a negative feedback mechanism when heat loss goes toward cooling the lake, but a positive feedback mechanism when heat loss goes toward ice formation. Ice cover sensitivity relationships were compared between shallow coastal regions of the Great Lakes and similarly shallow smaller, inland lakes. It was found that the sensitivity to air temperature is similar between these coastal regions and smaller lakes, but that the absolute amount of ice that forms varies significantly between small lakes and the Great Lakes, and amongst the Great Lakes themselves. The Lake Superior application of the ROMS three-dimensional hydrodynamic numerical model verifies a deterministic linear relationship between air temperature and ice cover, which is also strongest around the period of ice formation. When the Lake Superior bathymetry is experimentally adjusted by a constant vertical multiplier, average lake depth is shown to have a nonlinear relationship with seasonal ice cover, and this nonlinearity may be associated with a nonlinear increase in the lake-wide volume of the surface mixed layer.

  13. Integrated approach using multi-platform sensors for enhanced high-resolution daily ice cover product

    NASA Astrophysics Data System (ADS)

    Bonev, George; Gladkova, Irina; Grossberg, Michael; Romanov, Peter; Helfrich, Sean

    2016-09-01

    The ultimate objective of this work is to improve characterization of the ice cover distribution in the polar areas, to improve sea ice mapping and to develop a new automated real-time high spatial resolution multi-sensor ice extent and ice edge product for use in operational applications. Despite a large number of currently available automated satellite-based sea ice extent datasets, analysts at the National Ice Center tend to rely on original satellite imagery (provided by satellite optical, passive microwave and active microwave sensors) mainly because the automated products derived from satellite optical data have gaps in the area coverage due to clouds and darkness, passive microwave products have poor spatial resolution, automated ice identifications based on radar data are not quite reliable due to a considerable difficulty in discriminating between the ice cover and rough ice-free ocean surface due to winds. We have developed a multisensor algorithm that first extracts maximum information on the sea ice cover from imaging instruments VIIRS and MODIS, including regions covered by thin, semitransparent clouds, then supplements the output by the microwave measurements and finally aggregates the results into a cloud gap free daily product. This ability to identify ice cover underneath thin clouds, which is usually masked out by traditional cloud detection algorithms, allows for expansion of the effective coverage of the sea ice maps and thus more accurate and detailed delineation of the ice edge. We have also developed a web-based monitoring system that allows comparison of our daily ice extent product with the several other independent operational daily products.

  14. Is Ice-Rafted Sediment in a North Pole Marine Record Evidence for Perennial Sea-ice Cover?

    NASA Technical Reports Server (NTRS)

    Tremblay, L.B.; Schmidt, G.A.; Pfirman, S.; Newton, R.; DeRepentigny, P.

    2015-01-01

    Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (approximately 88 degrees N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards. However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present. We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with other land and marine records.

  15. Were lakes on early Mars perennially were ice-covered?

    NASA Astrophysics Data System (ADS)

    Sumner, D. Y.; Rivera-Hernandez, F.; Mackey, T. J.

    2016-12-01

    Paleo-lake deposits indicate that Mars once sustained liquid water, supporting the idea of an early "wet and warm" Mars. However, liquid water can be sustained under ice in cold conditions as demonstrated by perennially ice-covered lakes (PICLs) in Antarctica. If martian lakes were ice-covered, the global climate on early Mars could have been much colder and dryer than if the atmosphere was in equilibrium with long-lived open water lakes. Modern PICLs on Earth have diagnostic sedimentary features. Unlike open water lakes that are dominated by mud, and drop stones or tills if icebergs are present, previous studies determined that deposits in PICLs can include coarser grains that are transported onto the ice cover, where they absorb solar radiation, melt through the ice and are deposited with lacustrine muds. In Lake Hoare, Antarctica, these coarse grains form conical sand mounds and ridges. Our observations of ice-covered lakes Joyce, Fryxell, Vanda and Hoare, Antarctica suggest that the distributions of grains depend significantly on ice characteristics. Deposits in these lakes contain moderately well to moderately sorted medium to very coarse sand grains, which preferentially melt through the ice whereas granules and larger grains remain on the ice surface. Similarly, high albedo grains are concentrated on the ice surface, whereas low albedo grains melt deeper into the ice, demonstrating a segregation of grains due to ice-sediment interactions. In addition, ice cover thickness may determine the spatial distribution of sand deposited in PICLs. Localized sand mounds and ridges composed of moderately sorted sand are common in PICLs with rough ice covers greater than 3 m thick. In contrast, lakes with smooth and thinner ice have disseminated sand grains and laterally extensive sand layers but may not have sand mounds. At Gale Crater, Mars, the Murray formation consists of sandy lacustrine mudstones, but the depositional process for the sand is unknown. The presence of

  16. Microbiota within the perennial ice cover of Lake Vida, Antarctica.

    PubMed

    Mosier, Annika C; Murray, Alison E; Fritsen, Christian H

    2007-02-01

    Lake Vida, located in the McMurdo Dry Valleys, Antarctica, is an 'ice-sealed' lake with approximately 19 m of ice covering a highly saline water column (approximately 245 ppt). The lower portions of the ice cover and the lake beneath have been isolated from the atmosphere and land for circa 2800 years. Analysis of microbial assemblages within the perennial ice cover of the lake revealed a diverse array of bacteria and eukarya. Bacterial and eukaryal denaturing gradient gel electrophoresis phylotype profile similarities were low (<59%) between all of the depths compared (five depths spanning 11 m of the ice cover), with the greatest differences occurring between surface and deep ice. The majority of bacterial 16S rRNA gene sequences in the surface ice were related to Actinobacteria (42%) while Gammaproteobacteria (52%) dominated the deep ice community. Comparisons of assemblage composition suggest differences in ice habitability and organismal origin in the upper and lower portions of ice cover. Specifically, the upper ice cover microbiota likely reflect the modern day transport and colonization of biota from the terrestrial landscape, whereas assemblages in the deeper ice are more likely to be persistent remnant biota that originated from the ancient liquid water column of the lake that froze.

  17. The structure of internal stresses in the uncompacted ice cover

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sukhorukov, K.K.

    1995-12-31

    Interactions between engineering structures and sea ice cover are associated with an inhomogeneous space/time field of internal stresses. Field measurements (e.g., Coon, 1989; Tucker, 1992) have revealed considerable local stresses depending on the regional stress field and ice structure. These stresses appear in different time and space scales and depend on rheologic properties of the ice. To estimate properly the stressed state a knowledge of a connection between internal stress components in various regions of the ice cover is necessary. To develop reliable algorithms for estimates of ice action on engineering structures new experimental data are required to take intomore » account both microscale (comparable with local ice inhomogeneities) and small-scale (kilometers) inhomogeneities of the ice cover. Studies of compacted ice (concentration N is nearly 1) are mostly important. This paper deals with the small-scale spatial distribution of internal stresses in the interaction zone between the ice covers of various concentrations and icebergs. The experimental conditions model a situation of the interaction between a wide structure and the ice cover. Field data on a drifting ice were collected during the Russian-US experiment in Antarctica WEDDELL-I in 1992.« less

  18. Is ice-rafted sediment in a North Pole marine record evidence for perennial sea-ice cover?

    PubMed

    Tremblay, L B; Schmidt, G A; Pfirman, S; Newton, R; DeRepentigny, P

    2015-10-13

    Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (≈88° N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards (Krylov et al. 2008 Paleoceanography 23, PA1S06. (doi:10.1029/2007PA001497); Darby 2008 Paleoceanography 23, PA1S07. (doi:10.1029/2007PA001479)). However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present (Polyak et al. 2010 Quaternary Science Reviews 29, 1757-1778. (doi:10.1016/j.quascirev.2010.02.010)). We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with

  19. Ice cover affects the growth of a stream-dwelling fish.

    PubMed

    Watz, Johan; Bergman, Eva; Piccolo, John J; Greenberg, Larry

    2016-05-01

    Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.

  20. Impacts of the Variability of Ice Types on the Decline of the Arctic Perennial Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2005-01-01

    The observed rapid decline in the Arctic perennial ice cover is one of the most remarkable signal of change in the Arctic region. Updated data now show an even higher rate of decline of 9.8% per decade than the previous report of 8.9% per decade mainly because of abnormally low values in the last 4 years. To gain insights into this decline, the variability of the second year ice, which is the relatively thin component of the perennial ice cover, and other ice types is studied. The perennial ice cover in the 1990s was observed to be highly variable which might have led to higher production of second year ice and may in part explain the observed ice thinning during the period and triggered further decline. The passive microwave signature of second year ice is also studied and results show that while the signature is different from that of the older multiyear ice, it is surprisingly more similar to that of first year ice. This in part explains why previous estimates of the area of multiyear ice during the winter period are considerably lower than the area of the perennial ice cover during the preceding summer. Four distinct clusters representing radiometrically different types have been identified using multi-channel cluster analysis of passive microwave data. Data from two of these clusters, postulated to come from second year and older multiyear ice regions are also shown to have average thicknesses of 2.4 and 4.1 m, respectively, indicating that the passive microwave data may contain some ice thickness information that can be utilized for mass balance studies. The yearly anomaly maps indicate high gains of first year ice cover in the Arctic during the last decade which means higher production of second year ice and fraction of this type in the declining perennial ice cover. While not the only cause, the rapid decline in the perennial ice cover is in part caused by the increasing fractional component of the thinner second year ice cover that is very vulnerable to

  1. Formation and character of an ancient 19-m ice cover and underlying trapped brine in an "ice-sealed" east Antarctic lake.

    PubMed

    Doran, Peter T; Fritsen, Christian H; McKay, Christopher P; Priscu, John C; Adams, Edward E

    2003-01-07

    Lake Vida, one of the largest lakes in the McMurdo Dry Valleys of Antarctica, was previously believed to be shallow (<10 m) and frozen to its bed year-round. New ice-core analysis and temperature data show that beneath 19 m of ice is a water column composed of a NaCl brine with a salinity seven times that of seawater that remains liquid below -10 degrees C. The ice cover thickens at both its base and surface, sealing concentrated brine beneath. The ice cover is stabilized by a negative feedback between ice growth and the freezing-point depression of the brine. The ice cover contains frozen microbial mats throughout that are viable after thawing and has a history that extends to at least 2,800 (14)C years B.P., suggesting that the brine has been isolated from the atmosphere for as long. To our knowledge, Lake Vida has the thickest subaerial lake ice cover recorded and may represent a previously undiscovered end-member lacustrine ecosystem on Earth.

  2. Impact of wave mixing on the sea ice cover

    NASA Astrophysics Data System (ADS)

    Rynders, Stefanie; Aksenov, Yevgeny; Madec, Gurvan; Nurser, George; Feltham, Daniel

    2017-04-01

    As information on surface waves in ice-covered regions becomes available in ice-ocean models, there is an opportunity to model wave-related processes more accurate. Breaking waves cause mixing of the upper water column and present mixing schemes in ocean models take this into account through surface roughness. A commonly used approach is to calculate surface roughness from significant wave height, parameterised from wind speed. We present results from simulations using modelled significant wave height instead, which accounts for the presence of sea ice and the effect of swell. The simulations use the NEMO ocean model coupled to the CICE sea ice model, with wave information from the ECWAM model of the European Centre for Medium-Range Weather Forecasts (ECMWF). The new waves-in-ice module allows waves to propagate in sea ice and attenuates waves according to multiple scattering and non-elastic losses. It is found that in the simulations with wave mixing the mixed layer depth (MLD) under ice cover is reduced, since the parameterisation from wind speed overestimates wave height in the ice-covered regions. The MLD change, in turn, affects sea ice concentration and ice thickness. In the Arctic, reduced MLD in winter translates into increased ice thicknesses overall, with higher increases in the Western Arctic and decreases along the Siberian coast. In summer, shallowing of the mixed layer results in more heat accumulating in the surface ocean, increasing ice melting. In the Southern Ocean the meridional gradient in ice thickness and concentration is increased. We argue that coupling waves with sea ice - ocean models can reduce negative biases in sea ice cover, affecting the distribution of nutrients and, thus, biological productivity and ecosystems. This coupling will become more important in the future, when wave heights in a large part of the Arctic are expected to increase due to sea ice retreat and a larger wave fetch. Therefore, wave mixing constitutes a possible

  3. A Changing Arctic Sea Ice Cover and the Partitioning of Solar Radiation

    NASA Astrophysics Data System (ADS)

    Perovich, D. K.; Light, B.; Polashenski, C.; Nghiem, S. V.

    2010-12-01

    Certain recent changes in the Arctic sea ice cover are well established. There has been a reduction in sea ice extent, an overall thinning of the ice cover, reduced prevalence of perennial ice with accompanying increases in seasonal ice, and a lengthening of the summer melt season. Here we explore the effects of these changes on the partitioning of solar energy between reflection to the atmosphere, absorption within the ice, and transmission to the ocean. The physical changes in the ice cover result in less light reflected and more light absorbed in the ice and transmitted to the ocean. These changes directly affect the heat and mass balance of the ice as well as the amount of light available for photosynthesis within and beneath the ice cover. The central driver is that seasonal ice covers tend to have lower albedo than perennial ice throughout the melt season, permitting more light to penetrate into the ice and ocean. The enhanced light penetration increases the amount of internal melting of the ice and the heat content of the upper ocean. The physical changes in the ice cover mentioned above have affected both the amount and the timing of the photosynthetically active radiation (PAR) transmitted into the ice and ocean, increasing transmitted PAR, particularly in the spring. A comparison of the partitioning of solar irradiance and PAR for both historical and recent ice conditions will be presented.

  4. Arctic ice cover, ice thickness and tipping points.

    PubMed

    Wadhams, Peter

    2012-02-01

    We summarize the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent had been shrinking at a relatively modest rate of 3-4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million km(2). Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that the trends towards retreat and thinning will inevitably lead to an eventual loss of all ice in summer, which can be described as a 'tipping point' in that the former situation, of an Arctic covered with mainly multi-year ice, cannot be retrieved.

  5. Formation and character of an ancient 19-m ice cover and underlying trapped brine in an “ice-sealed” east Antarctic lake

    PubMed Central

    Doran, Peter T.; Fritsen, Christian H.; McKay, Christopher P.; Priscu, John C.; Adams, Edward E.

    2003-01-01

    Lake Vida, one of the largest lakes in the McMurdo Dry Valleys of Antarctica, was previously believed to be shallow (<10 m) and frozen to its bed year-round. New ice-core analysis and temperature data show that beneath 19 m of ice is a water column composed of a NaCl brine with a salinity seven times that of seawater that remains liquid below −10°C. The ice cover thickens at both its base and surface, sealing concentrated brine beneath. The ice cover is stabilized by a negative feedback between ice growth and the freezing-point depression of the brine. The ice cover contains frozen microbial mats throughout that are viable after thawing and has a history that extends to at least 2,800 14C years B.P., suggesting that the brine has been isolated from the atmosphere for as long. To our knowledge, Lake Vida has the thickest subaerial lake ice cover recorded and may represent a previously undiscovered end-member lacustrine ecosystem on Earth. PMID:12518052

  6. Variability and Anomalous Trends in the Global Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2012-01-01

    The advent of satellite data came fortuitously at a time when the global sea ice cover has been changing rapidly and new techniques are needed to accurately assess the true state and characteristics of the global sea ice cover. The extent of the sea ice in the Northern Hemisphere has been declining by about -4% per decade for the period 1979 to 2011 but for the period from 1996 to 2010, the rate of decline became even more negative at -8% per decade, indicating an acceleration in the decline. More intriguing is the drastically declining perennial sea ice area, which is the ice that survives the summer melt and observed to be retreating at the rate of -14% per decade during the 1979 to 2012 period. Although a slight recovery occurred in the last three years from an abrupt decline in 2007, the perennial ice extent was almost as low as in 2007 in 2011. The multiyear ice, which is the thick component of the perennial ice and regarded as the mainstay of the Arctic sea ice cover is declining at an even higher rate of -19% per decade. The more rapid decline of the extent of this thicker ice type means that the volume of the ice is also declining making the survival of the Arctic ice in summer highly questionable. The slight recovery in 2008, 2009 and 2010 for the perennial ice in summer was likely associated with an apparent cycle in the time series with a period of about 8 years. Results of analysis of concurrent MODIS and AMSR-E data in summer also provide some evidence of more extensive summer melt and meltponding in 2007 and 2011 than in other years. Meanwhile, the Antarctic sea ice cover, as observed by the same set of satellite data, is showing an unexpected and counter intuitive increase of about 1 % per decade over the same period. Although a strong decline in ice extent is apparent in the Bellingshausen/ Amundsen Seas region, such decline is more than compensated by increases in the extent of the sea ice cover in the Ross Sea region. The results of analysis of

  7. Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Simmons, G. M. Jr; McKay, C. P.; Wharton RA, J. r. (Principal Investigator)

    1989-01-01

    Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3-5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30-60 years. Therefore, the lake environment responds to changes on a 10-100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.

  8. Large Decadal Decline of the Arctic Multiyear Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2012-01-01

    The perennial ice area was drastically reduced to 38% of its climatological average in 2007 but recovered slightly in 2008, 2009, and 2010 with the areas being 10%, 24%, and 11% higher than in 2007, respectively. However, trends in extent and area remained strongly negative at -12.2% and -13.5% decade (sup -1), respectively. The thick component of the perennial ice, called multiyear ice, as detected by satellite data during the winters of 1979-2011 was studied, and results reveal that the multiyear ice extent and area are declining at an even more rapid rate of -15.1% and -17.2% decade(sup -1), respectively, with a record low value in 2008 followed by higher values in 2009, 2010, and 2011. Such a high rate in the decline of the thick component of the Arctic ice cover means a reduction in the average ice thickness and an even more vulnerable perennial ice cover. The decline of the multiyear ice area from 2007 to 2008 was not as strong as that of the perennial ice area from 2006 to 2007, suggesting a strong role of second-year ice melt in the latter. The sea ice cover is shown to be strongly correlated with surface temperature, which is increasing at about 3 times the global average in the Arctic but appears weakly correlated with the Arctic Oscillation (AO), which controls the atmospheric circulation in the region. An 8-9-yr cycle is apparent in the multiyear ice record, which could explain, in part, the slight recovery in the last 3 yr.

  9. Large Decadal Decline of the Arctic Multiyear Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2011-01-01

    The perennial ice area was drastically reduced to 38% of its climatological average in 2007 but recovered somewhat in 2008, 2009 and 2010 with the areas being 10%, 24%, and 11% higher than in 2007, respectively. However, the trends in the extent and area remain strongly negative at -12.2% and -13.5 %/decade, respectively. The thick component of the perennial ice, called multiyear ice, as detected by satellite data in the winters of 1979 to 2011 was studied and results reveal that the multiyear ice extent and area are declining at an even more rapid rate of -15.1% and -17.2 % per decade, respectively, with record low value in 2008 followed by higher values in 2009, 2010 and 2011. Such high rate in the decline of the thick component of the Arctic ice cover means a reduction in average ice thickness and an even more vulnerable perennial ice cover. The decline of the multiyear ice area from 2007 to 2008 was not as strong as that of the perennial ice area from 2006 to 2007 suggesting a strong role of second year ice melt in the latter. The sea ice cover is shown to be strongly correlated with surface temperature which is increasing at about three times global average in the Arctic but appears weakly correlated with the AO which controls the dynamics of the region. An 8 to 9-year cycle is apparent in the multiyear ice record which could explain in part the slight recovery in the last three years.

  10. Ice-cover effects on competitive interactions between two fish species.

    PubMed

    Helland, Ingeborg P; Finstad, Anders G; Forseth, Torbjørn; Hesthagen, Trygve; Ugedal, Ola

    2011-05-01

    1. Variations in the strength of ecological interactions between seasons have received little attention, despite an increased focus on climate alterations on ecosystems. Particularly, the winter situation is often neglected when studying competitive interactions. In northern temperate freshwaters, winter implies low temperatures and reduced food availability, but also strong reduction in ambient light because of ice and snow cover. Here, we study how brown trout [Salmo trutta (L.)] respond to variations in ice-cover duration and competition with Arctic charr [Salvelinus alpinus (L.)], by linking laboratory-derived physiological performance and field data on variation in abundance among and within natural brown trout populations. 2. Both Arctic charr and brown trout reduced resting metabolic rate under simulated ice-cover (darkness) in the laboratory, compared to no ice (6-h daylight). However, in contrast to brown trout, Arctic charr was able to obtain positive growth rate in darkness and had higher food intake in tank experiments than brown trout. Arctic charr also performed better (lower energy loss) under simulated ice-cover in a semi-natural environment with natural food supply. 3. When comparing brown trout biomass across 190 Norwegian lakes along a climate gradient, longer ice-covered duration decreased the biomass only in lakes where brown trout lived together with Arctic charr. We were not able to detect any effect of ice-cover on brown trout biomass in lakes where brown trout was the only fish species. 4. Similarly, a 25-year time series from a lake with both brown trout and Arctic charr showed that brown trout population growth rate depended on the interaction between ice breakup date and Arctic charr abundance. High charr abundance was correlated with low trout population growth rate only in combination with long winters. 5. In conclusion, the two species differed in performance under ice, and the observed outcome of competition in natural populations

  11. An automated approach for mapping persistent ice and snow cover over high latitude regions

    USGS Publications Warehouse

    Selkowitz, David J.; Forster, Richard R.

    2016-01-01

    We developed an automated approach for mapping persistent ice and snow cover (glaciers and perennial snowfields) from Landsat TM and ETM+ data across a variety of topography, glacier types, and climatic conditions at high latitudes (above ~65°N). Our approach exploits all available Landsat scenes acquired during the late summer (1 August–15 September) over a multi-year period and employs an automated cloud masking algorithm optimized for snow and ice covered mountainous environments. Pixels from individual Landsat scenes were classified as snow/ice covered or snow/ice free based on the Normalized Difference Snow Index (NDSI), and pixels consistently identified as snow/ice covered over a five-year period were classified as persistent ice and snow cover. The same NDSI and ratio of snow/ice-covered days to total days thresholds applied consistently across eight study regions resulted in persistent ice and snow cover maps that agreed closely in most areas with glacier area mapped for the Randolph Glacier Inventory (RGI), with a mean accuracy (agreement with the RGI) of 0.96, a mean precision (user’s accuracy of the snow/ice cover class) of 0.92, a mean recall (producer’s accuracy of the snow/ice cover class) of 0.86, and a mean F-score (a measure that considers both precision and recall) of 0.88. We also compared results from our approach to glacier area mapped from high spatial resolution imagery at four study regions and found similar results. Accuracy was lowest in regions with substantial areas of debris-covered glacier ice, suggesting that manual editing would still be required in these regions to achieve reasonable results. The similarity of our results to those from the RGI as well as glacier area mapped from high spatial resolution imagery suggests it should be possible to apply this approach across large regions to produce updated 30-m resolution maps of persistent ice and snow cover. In the short term, automated PISC maps can be used to rapidly

  12. In-lake carbon dioxide concentration patterns in four distinct phases in relation to ice cover dynamics

    NASA Astrophysics Data System (ADS)

    Denfeld, B. A.; Wallin, M.; Sahlee, E.; Sobek, S.; Kokic, J.; Chmiel, H.; Weyhenmeyer, G. A.

    2014-12-01

    Global carbon dioxide (CO2) emission estimates from inland waters include emissions at ice melt that are based on simple assumptions rather than evidence. To account for CO2 accumulation below ice and potential emissions into the atmosphere at ice melt we combined continuous CO2 concentrations with spatial CO2 sampling in an ice-covered small boreal lake. From early ice cover to ice melt, our continuous surface water CO2 concentration measurements at 2 m depth showed a temporal development in four distinct phases: In early winter, CO2 accumulated continuously below ice, most likely due to biological in-lake and catchment inputs. Thereafter, in late winter, CO2 concentrations remained rather constant below ice, as catchment inputs were minimized and vertical mixing of hypolimnetic water was cut off. As ice melt began, surface water CO2 concentrations were rapidly changing, showing two distinct peaks, the first one reflecting horizontal mixing of CO2 from surface and catchment waters, the second one reflecting deep water mixing. We detected that 83% of the CO2 accumulated in the water during ice cover left the lake at ice melt which corresponded to one third of the total CO2 storage. Our results imply that CO2 emissions at ice melt must be accurately integrated into annual CO2 emission estimates from inland waters. If up-scaling approaches assume that CO2 accumulates linearly under ice and at ice melt all CO2 accumulated during ice cover period leaves the lake again, present estimates may overestimate CO2 emissions from small ice covered lakes. Likewise, neglecting CO2 spring outbursts will result in an underestimation of CO2 emissions from small ice covered lakes.

  13. Trends and variability in summer sea ice cover in the Canadian Arctic based on the Canadian Ice Service Digital Archive, 1960-2008 and 1968-2008

    NASA Astrophysics Data System (ADS)

    Tivy, Adrienne; Howell, Stephen E. L.; Alt, Bea; McCourt, Steve; Chagnon, Richard; Crocker, Greg; Carrieres, Tom; Yackel, John J.

    2011-03-01

    The Canadian Ice Service Digital Archive (CISDA) is a compilation of weekly ice charts covering Canadian waters from the early 1960s to present. The main sources of uncertainty in the database are reviewed and the data are validated for use in climate studies before trends and variability in summer averaged sea ice cover are investigated. These data revealed that between 1968 and 2008, summer sea ice cover has decreased by 11.3% ± 2.6% decade-1 in Hudson Bay, 2.9% ± 1.2% decade-1 in the Canadian Arctic Archipelago (CAA), 8.9% ± 3.1% decade-1 in Baffin Bay, and 5.2% ± 2.4% decade-1 in the Beaufort Sea with no significant reductions in multiyear ice. Reductions in sea ice cover are linked to increases in early summer surface air temperature (SAT); significant increases in SAT were observed in every season and they are consistently greater than the pan-Arctic change by up to ˜0.2°C decade-1. Within the CAA and Baffin Bay, the El Niño-Southern Oscillation index correlates well with multiyear ice coverage (positive) and first-year ice coverage (negative) suggesting that El Niño episodes precede summers with more multiyear ice and less first-year ice. Extending the trend calculations back to 1960 along the major shipping routes revealed significant decreases in summer sea ice coverage ranging between 11% and 15% decade-1 along the route through Hudson Bay and 6% and 10% decade-1 along the southern route of the Northwest Passage, the latter is linked to increases in SAT. Between 1960 and 2008, no significant trends were found along the northern western Parry Channel route of the Northwest Passage.

  14. Microbial life under ice: Metagenome diversity and in situ activity of Verrucomicrobia in seasonally ice-covered lakes.

    PubMed

    Tran, Patricia; Ramachandran, Arthi; Khawasek, Ola; Beisner, Beatrix E; Rautio, Milla; Huot, Yannick; Walsh, David A

    2018-06-19

    Northern lakes are ice-covered for a large part of the year, yet our understanding of microbial diversity and activity during winter lags behind that of the ice-free period. In this study, we investigated under-ice diversity and metabolism of Verrucomicrobia in seasonally ice-covered lakes in temperate and boreal regions of Quebec, Canada using 16S rRNA sequencing, metagenomics and metatranscriptomics. Verrucomicrobia, particularly the V1, V3 and V4 subdivisions, were abundant during ice-covered periods. A diversity of Verrucomicrobia genomes were reconstructed from Quebec lake metagenomes. Several genomes were associated with the ice-covered period and were represented in winter metatranscriptomes, supporting the notion that Verrucomicrobia are metabolically active under ice. Verrucomicrobia transcriptome analysis revealed a range of metabolisms potentially occurring under ice, including carbohydrate degradation, glycolate utilization, scavenging of chlorophyll degradation products, and urea use. Genes for aerobic sulfur and hydrogen oxidation were expressed, suggesting chemolithotrophy may be an adaptation to conditions where labile carbon may be limited. The expression of genes for flagella biosynthesis and chemotaxis was detected, suggesting Verrucomicrobia may be actively sensing and responding to winter nutrient pulses, such as phytoplankton blooms. These results increase our understanding on the diversity and metabolic processes occurring under ice in northern lakes ecosystems. This article is protected by copyright. All rights reserved. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  15. Estimation of composite hydraulic resistance in ice-covered alluvial streams

    NASA Astrophysics Data System (ADS)

    Ghareh Aghaji Zare, Soheil; Moore, Stephanie A.; Rennie, Colin D.; Seidou, Ousmane; Ahmari, Habib; Malenchak, Jarrod

    2016-02-01

    Formation, propagation, and recession of ice cover introduce a dynamic boundary layer to the top of rivers during northern winters. Ice cover affects water velocity magnitude and distribution, water level and consequently conveyance capacity of the river. In this research, total resistance, i.e., "composite resistance," is studied for a 4 month period including stable ice cover, breakup, and open water stages in Lower Nelson River (LNR), northern Manitoba, Canada. Flow and ice characteristics such as water velocity and depth and ice thickness and condition were measured continuously using acoustic techniques. An Acoustic Doppler Current Profiler (ADCP) and Shallow Water Ice Profiling Sonar (SWIPS) were installed simultaneously on a bottom mount and deployed for this purpose. Total resistance to the flow and boundary roughness are estimated using measured bulk hydraulic parameters. A novel method is developed to calculate composite resistance directly from measured under ice velocity profiles. The results of this method are compared to the measured total resistance and to the calculated composite resistance using formulae available in literature. The new technique is demonstrated to compare favorably to measured total resistance and to outperform previously available methods.

  16. Observations of the Sea Ice Cover Using Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Kwok, Ronald

    1995-01-01

    The fringes observed in repeat pass interferograms are expressions of surface relief and relative displacements. The limiting condition in the application of spaceborne radar interferometry to the remote sensing of the sea ice cover is the large magnitude of motion between repeat passes. The translation and rotation of ice floes tend to decorrelate the observations rendering radar interferometry ineffective. In our study, we have located three images in the high Arctic during a period when there was negligible motion between repeat observations. The fringes obtained from these images show a wealth of information about the sea ice cover which is important in atmosphere-ice interactions and sea ice mechanics. These measurements provide the first detailed remote sensing view of the sea ice cover. Ridges can be observed and their heights estimated if the interferometric baseline allows. We have observed ridges with heights greater than 4m. The variability in the phase measurements over an area provides an indication of the large scale roughness. Relative centimetric displacements between rigid ice floes have been observed. We illustrate these observations with examples extracted from the interferograms formed from this set of ERS-1 SAR images.

  17. Evaporation of ice in planetary atmospheres: Ice-covered rivers on Mars

    NASA Technical Reports Server (NTRS)

    Wallace, D.; Sagan, C.

    1978-01-01

    The evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. The thickness of the ice is governed principally by the solar flux which penetrates the ice layer and then is conducted back to the surface. Evaporation from the surface is governed by wind and free convection. In the absence of wind, eddy diffusion is caused by the lower density of water vapor in comparison to the density of the Martian atmosphere. For mean martian insolations, the evaporation rate above the ice is approximately 10 to the minus 8th power gm/sq cm/s. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as ice-chocked rivers. Typical equilibrium thicknesses of such ice covers are approximately 10m to 30 m; typical surface temperatures are 210 to 235 K.

  18. Sea ice in the Baltic Sea - revisiting BASIS ice, a historical data set covering the period 1960/1961-1978/1979

    NASA Astrophysics Data System (ADS)

    Löptien, U.; Dietze, H.

    2014-12-01

    The Baltic Sea is a seasonally ice-covered, marginal sea in central northern Europe. It is an essential waterway connecting highly industrialised countries. Because ship traffic is intermittently hindered by sea ice, the local weather services have been monitoring sea ice conditions for decades. In the present study we revisit a historical monitoring data set, covering the winters 1960/1961 to 1978/1979. This data set, dubbed Data Bank for Baltic Sea Ice and Sea Surface Temperatures (BASIS) ice, is based on hand-drawn maps that were collected and then digitised in 1981 in a joint project of the Finnish Institute of Marine Research (today the Finnish Meteorological Institute (FMI)) and the Swedish Meteorological and Hydrological Institute (SMHI). BASIS ice was designed for storage on punch cards and all ice information is encoded by five digits. This makes the data hard to access. Here we present a post-processed product based on the original five-digit code. Specifically, we convert to standard ice quantities (including information on ice types), which we distribute in the current and free Network Common Data Format (NetCDF). Our post-processed data set will help to assess numerical ice models and provide easy-to-access unique historical reference material for sea ice in the Baltic Sea. In addition we provide statistics showcasing the data quality. The website http://www.baltic-ocean.org hosts the post-processed data and the conversion code. The data are also archived at the Data Publisher for Earth & Environmental Science, PANGAEA (doi:10.1594/PANGAEA.832353).

  19. The seasonal cycle of snow cover, sea ice and surface albedo

    NASA Technical Reports Server (NTRS)

    Robock, A.

    1980-01-01

    The paper examines satellite data used to construct mean snow cover caps for the Northern Hemisphere. The zonally averaged snow cover from these maps is used to calculate the seasonal cycle of zonally averaged surface albedo. The effects of meltwater on the surface, solar zenith angle, and cloudiness are parameterized and included in the calculations of snow and ice albedo. The data allows a calculation of surface albedo for any land or ocean 10 deg latitude band as a function of surface temperature ice and snow cover; the correct determination of the ice boundary is more important than the snow boundary for accurately simulating the ice and snow albedo feedback.

  20. Changes in sea ice cover and ice sheet extent at the Yermak Plateau during the last 160 ka - Reconstructions from biomarker records

    NASA Astrophysics Data System (ADS)

    Kremer, A.; Stein, R.; Fahl, K.; Ji, Z.; Yang, Z.; Wiers, S.; Matthiessen, J.; Forwick, M.; Löwemark, L.; O'Regan, M.; Chen, J.; Snowball, I.

    2018-02-01

    The Yermak Plateau is located north of Svalbard at the entrance to the Arctic Ocean, i.e. in an area highly sensitive to climate change. A multi proxy approach was carried out on Core PS92/039-2 to study glacial-interglacial environmental changes at the northern Barents Sea margin during the last 160 ka. The main emphasis was on the reconstruction of sea ice cover, based on the sea ice proxy IP25 and the related phytoplankton - sea ice index PIP25. Sea ice was present most of the time but showed significant temporal variability decisively affected by movements of the Svalbard Barents Sea Ice Sheet. For the first time, we prove the occurrence of seasonal sea ice at the eastern Yermak Plateau during glacial intervals, probably steered by a major northward advance of the ice sheet and the formation of a coastal polynya in front of it. Maximum accumulation of terrigenous organic carbon, IP25 and the phytoplankton biomarkers (brassicasterol, dinosterol, HBI III) can be correlated to distinct deglaciation events. More severe, but variable sea ice cover prevailed at the Yermak Plateau during interglacials. The general proximity to the sea ice margin is further indicated by biomarker (GDGT) - based sea surface temperatures below 2.5 °C.

  1. Evidence for Holocene centennial variability in sea ice cover based on IP25 biomarker reconstruction in the southern Kara Sea (Arctic Ocean)

    NASA Astrophysics Data System (ADS)

    Hörner, Tanja; Stein, Rüdiger; Fahl, Kirsten

    2017-10-01

    The Holocene is characterized by the late Holocene cooling trend as well as by internal short-term centennial fluctuations. Because Arctic sea ice acts as a significant component (amplifier) within the climate system, investigating its past long- and short-term variability and controlling processes is beneficial for future climate predictions. This study presents the first biomarker-based (IP25 and PIP25) sea ice reconstruction from the Kara Sea (core BP00-07/7), covering the last 8 ka. These biomarker proxies reflect conspicuous short-term sea ice variability during the last 6.5 ka that is identified unprecedentedly in the source region of Arctic sea ice by means of a direct sea ice indicator. Prominent peaks of extensive sea ice cover occurred at 3, 2, 1.3 and 0.3 ka. Spectral analysis of the IP25 record revealed 400- and 950-year cycles. These periodicities may be related to the Arctic/North Atlantic Oscillation, but probably also to internal climate system fluctuations. This demonstrates that sea ice belongs to a complex system that more likely depends on multiple internal forcing.

  2. Surfacing behavior and gas release of the physostome sprat (Sprattus sprattus) in ice-free and ice-covered waters.

    PubMed

    Solberg, Ingrid; Kaartvedt, Stein

    2014-01-01

    Upward-facing echosounders that provided continuous, long-term measurements were applied to address the surfacing behavior and gas release of the physostome sprat ( Sprattus sprattus ) throughout an entire winter in a 150-m-deep Norwegian fjord. During ice-free conditions, the sprat surfaced and released gas bubbles at night with an estimated surfacing rate of 3.5 times per fish day -1 . The vertical swimming speeds during surfacing were considerably higher (~10 times) than during diel vertical migrations, especially when returning from the surface, and particularly when the fjord was not ice covered. The sprat released gas a few hours after surfacing, suggesting that the sprat gulped atmospheric air during its excursions to the surface. While the surface activity increased after the fjord became ice covered, the records of gas release decreased sharply. The under-ice fish then displayed a behavior interpreted as "searching for the surface" by repeatedly ascending toward the ice, apparently with limited success of filling the swim bladder. This interpretation was supported by lower acoustic target strength in ice-covered waters. The frequent surfacing behavior demonstrated in this study indicates that gulping of atmospheric air is an important element in the life of sprat. While at least part of the population endured overwintering in the ice-covered habitat, ice covering may constrain those physostome fishes that lack a gas-generating gland in ways that remain to be established.

  3. Abrupt Decline in the Arctic Winter Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2007-01-01

    Maximum ice extents in the Arctic in 2005 and 2006 have been observed to be significantly lower (by about 6%) than the average of those of previous years starting in 1979. Since the winter maxima had been relatively stable with the trend being only about -1.5% per decade (compared to about -10% per decade for the perennial ice area), this is a significant development since signals from greenhouse warming are expected to be most prominent in winter. Negative ice anomalies are shown to be dominant in 2005 and 2006 especially in the Arctic basin and correlated with winds and surface temperature anomalies during the same period. Progressively increasing winter temperatures in the central Arctic starting in 1997 is observed with significantly higher rates of increase in 2005 and 2006. The Atlantic Oscillation (AO) indices correlate weakly with the sea ice and surface temperature anomaly data but may explain the recent shift in the perennial ice cover towards the western region. Results suggest that the trend in winter ice is finally in the process of catching up with that of the summer ice cover.

  4. Automated detection of ice cliffs within supraglacial debris cover

    NASA Astrophysics Data System (ADS)

    Herreid, Sam; Pellicciotti, Francesca

    2018-05-01

    Ice cliffs within a supraglacial debris cover have been identified as a source for high ablation relative to the surrounding debris-covered area. Due to their small relative size and steep orientation, ice cliffs are difficult to detect using nadir-looking space borne sensors. The method presented here uses surface slopes calculated from digital elevation model (DEM) data to map ice cliff geometry and produce an ice cliff probability map. Surface slope thresholds, which can be sensitive to geographic location and/or data quality, are selected automatically. The method also attempts to include area at the (often narrowing) ends of ice cliffs which could otherwise be neglected due to signal saturation in surface slope data. The method was calibrated in the eastern Alaska Range, Alaska, USA, against a control ice cliff dataset derived from high-resolution visible and thermal data. Using the same input parameter set that performed best in Alaska, the method was tested against ice cliffs manually mapped in the Khumbu Himal, Nepal. Our results suggest the method can accommodate different glaciological settings and different DEM data sources without a data intensive (high-resolution, multi-data source) recalibration.

  5. Variability and trends in the Arctic Sea ice cover: Results from different techniques

    NASA Astrophysics Data System (ADS)

    Comiso, Josefino C.; Meier, Walter N.; Gersten, Robert

    2017-08-01

    Variability and trend studies of sea ice in the Arctic have been conducted using products derived from the same raw passive microwave data but by different groups using different algorithms. This study provides consistency assessment of four of the leading products, namely, Goddard Bootstrap (SB2), Goddard NASA Team (NT1), EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI-SAF 1.2), and Hadley HadISST 2.2 data in evaluating variability and trends in the Arctic sea ice cover. All four provide generally similar ice patterns but significant disagreements in ice concentration distributions especially in the marginal ice zone and adjacent regions in winter and meltponded areas in summer. The discrepancies are primarily due to different ways the four techniques account for occurrences of new ice and meltponding. However, results show that the different products generally provide consistent and similar representation of the state of the Arctic sea ice cover. Hadley and NT1 data usually provide the highest and lowest monthly ice extents, respectively. The Hadley data also show the lowest trends in ice extent and ice area at -3.88%/decade and -4.37%/decade, respectively, compared to an average of -4.36%/decade and -4.57%/decade for all four. Trend maps also show similar spatial distribution for all four with the largest negative trends occurring at the Kara/Barents Sea and Beaufort Sea regions, where sea ice has been retreating the fastest. The good agreement of the trends especially with updated data provides strong confidence in the quantification of the rate of decline in the Arctic sea ice cover.Plain Language SummaryThe declining Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, especially in the summer, has been the center of attention in recent years. Reports on the sea <span class="hlt">ice</span> <span class="hlt">cover</span> have been provided by different institutions using basically the same set of satellite data but different techniques for estimating key parameters such as <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26342133','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26342133"><span>Winter severity determines functional trait composition of phytoplankton in seasonally <span class="hlt">ice-covered</span> lakes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Özkundakci, Deniz; Gsell, Alena S; Hintze, Thomas; Täuscher, Helgard; Adrian, Rita</p> <p>2016-01-01</p> <p>How climate change will affect the community dynamics and functionality of lake ecosystems during winter is still little understood. This is also true for phytoplankton in seasonally <span class="hlt">ice-covered</span> temperate lakes which are particularly vulnerable to the presence or absence of <span class="hlt">ice</span>. We examined changes in pelagic phytoplankton winter community structure in a north temperate lake (Müggelsee, Germany), <span class="hlt">covering</span> 18 winters between 1995 and 2013. We tested how phytoplankton taxa composition varied along a winter-severity gradient and to what extent winter severity shaped the functional trait composition of overwintering phytoplankton communities using multivariate statistical analyses and a functional trait-<span class="hlt">based</span> approach. We hypothesized that overwintering phytoplankton communities are dominated by taxa with trait combinations corresponding to the prevailing winter water column conditions, using <span class="hlt">ice</span> thickness measurements as a winter-severity indicator. Winter severity had little effect on univariate diversity indicators (taxon richness and evenness), but a strong relationship was found between the phytoplankton community structure and winter severity when taxon trait identity was taken into account. Species responses to winter severity were mediated by the key functional traits: motility, nutritional mode, and the ability to form resting stages. Accordingly, one or the other of two functional groups dominated the phytoplankton biomass during mild winters (i.e., thin or no <span class="hlt">ice</span> <span class="hlt">cover</span>; phototrophic taxa) or severe winters (i.e., thick <span class="hlt">ice</span> <span class="hlt">cover</span>; exclusively motile taxa). <span class="hlt">Based</span> on predicted milder winters for temperate regions and a reduction in <span class="hlt">ice-cover</span> durations, phytoplankton communities during winter can be expected to comprise taxa that have a relative advantage when the water column is well mixed (i.e., need not be motile) and light is less limiting (i.e., need not be mixotrophic). A potential implication of this result is that winter severity promotes different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ESSDD...7..419L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ESSDD...7..419L"><span>Sea <span class="hlt">ice</span> in the Baltic Sea - revisiting BASIS <span class="hlt">ice</span>, a~historical data set <span class="hlt">covering</span> the period 1960/1961-1978/1979</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Löptien, U.; Dietze, H.</p> <p>2014-06-01</p> <p>The Baltic Sea is a seasonally <span class="hlt">ice-covered</span>, marginal sea, situated in central northern Europe. It is an essential waterway connecting highly industrialised countries. Because ship traffic is intermittently hindered by sea <span class="hlt">ice</span>, the local weather services have been monitoring sea <span class="hlt">ice</span> conditions for decades. In the present study we revisit a historical monitoring data set, <span class="hlt">covering</span> the winters 1960/1961. This data set, dubbed Data Bank for Baltic Sea <span class="hlt">Ice</span> and Sea Surface Temperatures (BASIS) <span class="hlt">ice</span>, is <span class="hlt">based</span> on hand-drawn maps that were collected and then digitised 1981 in a joint project of the Finnish Institute of Marine Research (today Finish Meteorological Institute (FMI)) and the Swedish Meteorological and Hydrological Institute (SMHI). BASIS <span class="hlt">ice</span> was designed for storage on punch cards and all <span class="hlt">ice</span> information is encoded by five digits. This makes the data hard to access. Here we present a post-processed product <span class="hlt">based</span> on the original five-digit code. Specifically, we convert to standard <span class="hlt">ice</span> quantities (including information on <span class="hlt">ice</span> types), which we distribute in the current and free Network Common Data Format (NetCDF). Our post-processed data set will help to assess numerical <span class="hlt">ice</span> models and provide easy-to-access unique historical reference material for sea <span class="hlt">ice</span> in the Baltic Sea. In addition we provide statistics showcasing the data quality. The website <a href="www.baltic-ocean.org"target="_blank">www.baltic-ocean.org<a/> hosts the post-prossed data and the conversion code. The data are also archived at the Data Publisher for Earth & Environmental Science PANGEA (<a href="http://dx.doi.org/"target="_blank">doi:10.1594/PANGEA.832353<a/>).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C43D..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C43D..01R"><span>NASA <span class="hlt">Ice</span>Bridge: Scientific Insights from Airborne Surveys of the Polar Sea <span class="hlt">Ice</span> <span class="hlt">Covers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richter-Menge, J.; Farrell, S. L.</p> <p>2015-12-01</p> <p>The NASA Operation <span class="hlt">Ice</span>Bridge (OIB) airborne sea <span class="hlt">ice</span> surveys are designed to continue a valuable series of sea <span class="hlt">ice</span> thickness measurements by bridging the gap between NASA's <span class="hlt">Ice</span>, Cloud and Land Elevation Satellite (ICESat), which operated from 2003 to 2009, and ICESat-2, which is scheduled for launch in 2017. Initiated in 2009, OIB has conducted campaigns over the western Arctic Ocean (March/April) and Southern Oceans (October/November) on an annual basis when the thickness of sea <span class="hlt">ice</span> <span class="hlt">cover</span> is nearing its maximum. More recently, a series of Arctic surveys have also collected observations in the late summer, at the end of the melt season. The Airborne Topographic Mapper (ATM) laser altimeter is one of OIB's primary sensors, in combination with the Digital Mapping System digital camera, a Ku-band radar altimeter, a frequency-modulated continuous-wave (FMCW) snow radar, and a KT-19 infrared radiation pyrometer. Data from the campaigns are available to the research community at: http://nsidc.org/data/icebridge/. This presentation will summarize the spatial and temporal extent of the OIB campaigns and their complementary role in linking in situ and satellite measurements, advancing observations of sea <span class="hlt">ice</span> processes across all length scales. Key scientific insights gained on the state of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> will be highlighted, including snow depth, <span class="hlt">ice</span> thickness, surface roughness and morphology, and melt pond evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080045474','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080045474"><span>Physical and Radiative Characteristic and Long-term Variability of the Okhotsk Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nishio, Fumihiko; Comiso, Josefino C.; Gersten, Robert; Nakayama, Masashige; Ukita, Jinro; Gasiewski, Al; Stanko, Boba; Naoki, Kazuhiro</p> <p>2008-01-01</p> <p>Much of what we know about the large scale characteristics of the Okhotsk Sea <span class="hlt">ice</span> <span class="hlt">cover</span> has been provided by <span class="hlt">ice</span> concentration maps derived from passive microwave data. To understand what satellite data represent in a highly divergent and rapidly changing environment like the Okhotsk Sea, we take advantage of concurrent satellite, aircraft, and ship data acquired on 7 February and characterized the sea <span class="hlt">ice</span> <span class="hlt">cover</span> at different scales from meters to hundreds of kilometers. Through comparative analysis of surface features using co-registered data from visible, infrared and microwave channels we evaluated the general radiative and physical characteristics of the <span class="hlt">ice</span> <span class="hlt">cover</span> as well as quantify the distribution of different <span class="hlt">ice</span> types in the region. <span class="hlt">Ice</span> concentration maps from AMSR-E using the standard sets of channels, and also only the 89 GHz channel for optimal resolution, are compared with aircraft and high resolution visible data and while the standard set provides consistent results, the 89 GHz provides the means to observe mesoscale patterns and some unique features of the <span class="hlt">ice</span> <span class="hlt">cover</span>. Analysis of MODIS data reveals that thick <span class="hlt">ice</span> types represents about 37% of the <span class="hlt">ice</span> <span class="hlt">cover</span> indicating that young and new <span class="hlt">ice</span> types represent a large fraction of the <span class="hlt">ice</span> <span class="hlt">cover</span> that averages about 90% <span class="hlt">ice</span> concentration according to passive microwave data. These results are used to interpret historical data that indicate that the Okhotsk Sea <span class="hlt">ice</span> extent and area are declining at a rapid rate of about -9% and -12 % per decade, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=67183&Lab=NCER&keyword=climate+AND+change+AND+colorado+AND+effects&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=67183&Lab=NCER&keyword=climate+AND+change+AND+colorado+AND+effects&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>POTENTIAL CLIMATE WARMING EFFECTS ON <span class="hlt">ICE</span> <span class="hlt">COVERS</span> OF SMALL LAKES IN THE CONTIGUOUS U.S. (R824801)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p><h2>Abstract</h2><p>To simulate effects of projected climate change on <span class="hlt">ice</span> <span class="hlt">covers</span> of small lakes in the northern contiguous U.S., a process-<span class="hlt">based</span> simulation model is applied. This winter <span class="hlt">ice</span>/snow <span class="hlt">cover</span> model is associated with a deterministic, one-dimensional year-round water tem...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.C41C0990P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.C41C0990P"><span>Assessing, understanding, and conveying the state of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perovich, D. K.; Richter-Menge, J. A.; Rigor, I.; Parkinson, C. L.; Weatherly, J. W.; Nghiem, S. V.; Proshutinsky, A.; Overland, J. E.</p> <p>2003-12-01</p> <p>Recent studies indicate that the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is undergoing significant climate-induced changes, affecting both its extent and thickness. Satellite-derived estimates of Arctic sea <span class="hlt">ice</span> extent suggest a reduction of about 3% per decade since 1978. <span class="hlt">Ice</span> thickness data from submarines suggest a net thinning of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> since 1958. Changes (including oscillatory changes) in atmospheric circulation and the thermohaline properties of the upper ocean have also been observed. These changes impact not only the Arctic, but the global climate system and are likely accelerated by such processes as the <span class="hlt">ice</span>-albedo feedback. It is important to continue and expand long-term observations of these changes to (a) improve the fundamental understanding of the role of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the global climate system and (b) use the changes in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> as an early indicator of climate change. This is a formidable task that spans a range of temporal and spatial scales. Fortunately, there are numerous tools that can be brought to bear on this task, including satellite remote sensing, autonomous buoys, ocean moorings, field campaigns and numerical models. We suggest the integrated and coordinated use of these tools during the International Polar Year to monitor the state of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> and investigate its governing processes. For example, satellite remote sensing provides the large-scale snapshots of such basic parameters as <span class="hlt">ice</span> distribution, melt zone, and cloud fraction at intervals of half a day to a week. Buoys and moorings can contribute high temporal resolution and can measure parameters currently unavailable from space including <span class="hlt">ice</span> thickness, internal <span class="hlt">ice</span> temperature, and ocean temperature and salinity. Field campaigns can be used to explore, in detail, the processes that govern the <span class="hlt">ice</span> <span class="hlt">cover</span>. Numerical models can be used to assess the character of the changes in the <span class="hlt">ice</span> <span class="hlt">cover</span> and predict their impacts on the rest of the climate system. This work</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.C41C0992L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.C41C0992L"><span>The Role of Laboratory-<span class="hlt">Based</span> Studies of the Physical and Biological Properties of Sea <span class="hlt">Ice</span> in Supporting the Observation and Modeling of <span class="hlt">Ice</span> <span class="hlt">Covered</span> Seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Light, B.; Krembs, C.</p> <p>2003-12-01</p> <p>Laboratory-<span class="hlt">based</span> studies of the physical and biological properties of sea <span class="hlt">ice</span> are an essential link between high latitude field observations and existing numerical models. Such studies promote improved understanding of climatic variability and its impact on sea <span class="hlt">ice</span> and the structure of <span class="hlt">ice</span>-dependent marine ecosystems. Controlled laboratory experiments can help identify feedback mechanisms between physical and biological processes and their response to climate fluctuations. Climatically sensitive processes occurring between sea <span class="hlt">ice</span> and the atmosphere and sea <span class="hlt">ice</span> and the ocean determine surface radiative energy fluxes and the transfer of nutrients and mass across these boundaries. High temporally and spatially resolved analyses of sea <span class="hlt">ice</span> under controlled environmental conditions lend insight to the physics that drive these transfer processes. Techniques such as optical probing, thin section photography, and microscopy can be used to conduct experiments on natural sea <span class="hlt">ice</span> core samples and laboratory-grown <span class="hlt">ice</span>. Such experiments yield insight on small scale processes from the microscopic to the meter scale and can be powerful interdisciplinary tools for education and model parameterization development. Examples of laboratory investigations by the authors include observation of the response of sea <span class="hlt">ice</span> microstructure to changes in temperature, assessment of the relationships between <span class="hlt">ice</span> structure and the partitioning of solar radiation by first-year sea <span class="hlt">ice</span> <span class="hlt">covers</span>, observation of pore evolution and interfacial structure, and quantification of the production and impact of microbial metabolic products on the mechanical, optical, and textural characteristics of sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910064G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910064G"><span>Multi-decadal evolution of <span class="hlt">ice</span>/snow <span class="hlt">covers</span> in the Mont-Blanc massif (France)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guillet, Grégoire; Ravanel, Ludovic</p> <p>2017-04-01</p> <p>Dynamics and evolution of the major glaciers of the Mont-Blanc massif have been vastly studied since the XXth century. <span class="hlt">Ice</span>/snow <span class="hlt">covers</span> on steep rock faces as part of the cryosphere however remain poorly studied with only qualitative descriptions existing. The study of <span class="hlt">ice</span>/snow <span class="hlt">covers</span> is primordial to further understand permafrost degradation throughout the Mont-Blanc massif and to improve safety and prevention for mountain sports practitioners. This study focuses on quantifying the evolution of <span class="hlt">ice</span>/snow <span class="hlt">covers</span> surface during the past century using a specially developed monoplotting tool using Bayesian statistics and Markov Chain Monte Carlo algorithms. Combining digital elevation models and photographs <span class="hlt">covering</span> a time-span of 110 years, we calculated the <span class="hlt">ice</span>/snow <span class="hlt">cover</span> surface for 3 study sites — North faces of the Tour Ronde (3792 m a.s.l.) and the Grandes Jorasses (4208 m a.s.l.) and Triangle du Tacul (3970 m a.s.l.) — and deduced the evolution of their area throughout the XXth century. First results are showing several increase/decrease periods. The first decrease in <span class="hlt">ice</span>/snow <span class="hlt">cover</span> surface occurs between the 1940's and the 1950's. It is followed by an increase up to the 1980's. Since then, <span class="hlt">ice</span>/snow <span class="hlt">covers</span> show a general decrease in surface which is faster since the 2010's. Furthermore, the gain/loss during the increase/decrease periods varies with the considered <span class="hlt">ice</span>/snow <span class="hlt">cover</span>, making it an interesting cryospheric entity of its own.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.1406T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.1406T"><span>An Examination of the Sea <span class="hlt">Ice</span> Rheology for Seasonal <span class="hlt">Ice</span> Zones <span class="hlt">Based</span> on <span class="hlt">Ice</span> Drift and Thickness Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toyota, Takenobu; Kimura, Noriaki</p> <p>2018-02-01</p> <p>The validity of the sea <span class="hlt">ice</span> rheological model formulated by Hibler (1979), which is widely used in present numerical sea <span class="hlt">ice</span> models, is examined for the Sea of Okhotsk as an example of the seasonal <span class="hlt">ice</span> zone (SIZ), <span class="hlt">based</span> on satellite-derived sea <span class="hlt">ice</span> velocity, concentration and thickness. Our focus was the formulation of the yield curve, the shape of which can be estimated from <span class="hlt">ice</span> drift pattern <span class="hlt">based</span> on the energy equation of deformation, while the strength of the <span class="hlt">ice</span> <span class="hlt">cover</span> that determines its magnitude was evaluated using <span class="hlt">ice</span> concentration and thickness data. <span class="hlt">Ice</span> drift was obtained with a grid spacing of 37.5 km from the AMSR-E 89 GHz brightness temperature using a maximum cross-correlation method. The <span class="hlt">ice</span> thickness was obtained with a spatial resolution of 100 m from a regression of the PALSAR backscatter coefficients with <span class="hlt">ice</span> thickness. To assess scale dependence, the <span class="hlt">ice</span> drift data derived from a coastal radar <span class="hlt">covering</span> a 70 km range in the southernmost Sea of Okhotsk were similarly analyzed. The results obtained were mostly consistent with Hibler's formulation that was <span class="hlt">based</span> on the Arctic Ocean on both scales with no dependence on a time scale, and justify the treatment of sea <span class="hlt">ice</span> as a plastic material, with an elliptical shaped yield curve to some extent. However, it also highlights the difficulty in parameterizing sub-grid scale ridging in the model because grid scale <span class="hlt">ice</span> velocities reduce the deformation magnitude by half due to the large variation of the deformation field in the SIZ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070038189','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070038189"><span>Physical and Radiative Characteristics and Long Term Variability of the Okhotsk Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nishio, Fumihiko; Comiso, Josefino C.; Gersten, Robert; Nakayama, Masashige; Ukita, Jinro; Gasiewski, Al; Stanko, Boba; Naoki, Kazuhiro</p> <p>2007-01-01</p> <p>Much of what we know about the large scale characteristics of the Okhotsk Sea <span class="hlt">ice</span> <span class="hlt">cover</span> comes from <span class="hlt">ice</span> concentration maps derived from passive microwave data. To understand what these satellite data represents in a highly divergent and rapidly changing environment like the Okhotsk Sea, we analyzed concurrent satellite, aircraft, and ship data and characterized the sea <span class="hlt">ice</span> <span class="hlt">cover</span> at different scales from meters to tens of kilometers. Through comparative analysis of surface features using co-registered data from visible, infrared and microwave channels we evaluated how the general radiative and physical characteristics of the <span class="hlt">ice</span> <span class="hlt">cover</span> changes as well as quantify the distribution of different <span class="hlt">ice</span> types in the region. <span class="hlt">Ice</span> concentration maps from AMSR-E using the standard sets of channels, and also only the 89 GHz channel for optimal resolution, are compared with aircraft and high resolution visible data and while the standard set provides consistent results, the 89 GHz provides the means to observe mesoscale patterns and some unique features of the <span class="hlt">ice</span> <span class="hlt">cover</span>. Analysis of MODIS data reveals that thick <span class="hlt">ice</span> types represents about 37% of the <span class="hlt">ice</span> <span class="hlt">cover</span> indicating that young and new <span class="hlt">ice</span> represent a large fraction of the lice <span class="hlt">cover</span> that averages about 90% <span class="hlt">ice</span> concentration, according to passive microwave data. A rapid decline of -9% and -12 % per decade is observed suggesting warming signals but further studies are required because of aforementioned characteristics and because the length of the <span class="hlt">ice</span> season is decreasing by only 2 to 4 days per decade.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29784952','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29784952"><span>Vanishing river <span class="hlt">ice</span> <span class="hlt">cover</span> in the lower part of the Danube basin - signs of a changing climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ionita, M; Badaluta, C -A; Scholz, P; Chelcea, S</p> <p>2018-05-21</p> <p>Many of the world's largest rivers in the extra tropics are <span class="hlt">covered</span> with <span class="hlt">ice</span> during the cold season, and in the Northern Hemisphere approximately 60% of the rivers experience significant seasonal effects of river <span class="hlt">ice</span>. Here we present an observational data set of the <span class="hlt">ice</span> <span class="hlt">cover</span> regime for the lower part of the Danube River which spans over the period 1837-2016, and its the longest one on record over this area. The results in this study emphasize the strong impact of climate change on the occurrence of <span class="hlt">ice</span> regime especially in the second part of the 20 th century. The number of <span class="hlt">ice</span> <span class="hlt">cover</span> days has decreased considerably (~28days/century) mainly due to an increase in the winter mean temperature. In a long-term context, <span class="hlt">based</span> on documentary evidences, we show that the <span class="hlt">ice</span> <span class="hlt">cover</span> occurrence rate was relatively small throughout the Medieval Warm Period (MWP), while the highest occurrence rates were found during the Maunder Minimum and Dalton Minimum periods. We conclude that the river <span class="hlt">ice</span> regime can be used as a proxy for the winter temperature over the analyzed region and as an indicator of climate-change related impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15.3331N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15.3331N"><span>CO2 flux over young and snow-<span class="hlt">covered</span> Arctic pack <span class="hlt">ice</span> in winter and spring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nomura, Daiki; Granskog, Mats A.; Fransson, Agneta; Chierici, Melissa; Silyakova, Anna; Ohshima, Kay I.; Cohen, Lana; Delille, Bruno; Hudson, Stephen R.; Dieckmann, Gerhard S.</p> <p>2018-06-01</p> <p>Rare CO2 flux measurements from Arctic pack <span class="hlt">ice</span> show that two types of <span class="hlt">ice</span> contribute to the release of CO2 from the <span class="hlt">ice</span> to the atmosphere during winter and spring: young, thin <span class="hlt">ice</span> with a thin layer of snow and older (several weeks), thicker <span class="hlt">ice</span> with thick snow <span class="hlt">cover</span>. Young, thin sea <span class="hlt">ice</span> is characterized by high salinity and high porosity, and snow-<span class="hlt">covered</span> thick <span class="hlt">ice</span> remains relatively warm ( > -7.5 °C) due to the insulating snow <span class="hlt">cover</span> despite air temperatures as low as -40 °C. Therefore, brine volume fractions of these two <span class="hlt">ice</span> types are high enough to provide favorable conditions for gas exchange between sea <span class="hlt">ice</span> and the atmosphere even in mid-winter. Although the potential CO2 flux from sea <span class="hlt">ice</span> decreased due to the presence of the snow, the snow surface is still a CO2 source to the atmosphere for low snow density and thin snow conditions. We found that young sea <span class="hlt">ice</span> that is formed in leads without snow <span class="hlt">cover</span> produces CO2 fluxes an order of magnitude higher than those in snow-<span class="hlt">covered</span> older <span class="hlt">ice</span> (+1.0 ± 0.6 mmol C m-2 day-1 for young <span class="hlt">ice</span> and +0.2 ± 0.2 mmol C m-2 day-1 for older <span class="hlt">ice</span>).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611965L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611965L"><span>The influence of supraglacial debris <span class="hlt">cover</span> variability on de-<span class="hlt">icing</span> processes - examples from Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lukas, Sven; Benn, Douglas I.; Boston, Clare M.; Hawkins, Jack; Lehane, Niall E.; Lovell, Harold; Rooke, Michael</p> <p>2014-05-01</p> <p>Extensive supraglacial debris <span class="hlt">covers</span> are widespread near the margins of many cold-<span class="hlt">based</span> and polythermal surging and non-surging glaciers in Svalbard. Despite their importance for current glacier dynamics and a detailed understanding of how they will affect the de-<span class="hlt">icing</span> of <span class="hlt">ice</span>-marginal areas, little work has been carried out to shed light on the sedimentary processes operating in these debris <span class="hlt">covers</span>. We here present data from five different forelands in Svalbard. In all five cases, surfaces within the debris <span class="hlt">cover</span> can be regarded as stable where debris <span class="hlt">cover</span> thickness exceeds that of the active layer; vegetation development and absence of buried <span class="hlt">ice</span> exposures at the surface support this conclusion, although test pits and geophysical investigations have revealed the presence of buried <span class="hlt">ice</span> at greater depths (> 1-3 m). These findings imply that even seemingly stable surfaces at present will be subject to change by de-<span class="hlt">icing</span> in the future. Factors and processes that contribute towards a switch from temporarily stable to unstable conditions have been identified as: 1. The proximity to englacial or supraglacial meltwater channels. These channels enlarge due to thermo-erosion, which can lead to the eventual collapse of tunnel roofs and the sudden generation of linear instabilities in the system. Along such channels, ablation is enhanced compared to adjacent debris-<span class="hlt">covered</span> <span class="hlt">ice</span>, and continued thermo-erosion continuously exposes new areas of buried <span class="hlt">ice</span> at the surface. This works in conjunction with 2. Debris flows that occur on all sloping ground and transfer material from stable to less stable (sloping) locations within the debris <span class="hlt">cover</span> and eventually into supraglacial channels, from where material is then removed from the system. Several generations of debris flows have been identified in all five debris <span class="hlt">covers</span>, strongly suggesting that these processes are episodic and that the loci of these processes switch. This in turn indicates that transfer of material by debris flows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC23J..05A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC23J..05A"><span>Reduced Duration of <span class="hlt">Ice</span> <span class="hlt">Cover</span> in Swedish Lakes and Rivers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>AghaKouchak, A.; Hallerback, S. A. M.; Stensen, K.; David, G.; Persson, M.</p> <p>2016-12-01</p> <p>The worlds freshwater systems are one of the most altered ecosystems on earth. Climate change introduces additional stresses on such systems, and this study presents an example of such change in an investigation of <span class="hlt">ice</span> <span class="hlt">cover</span> duration in Swedish lakes and rivers. In situ observations from over 750 lakes and rivers in Sweden were analyzed, with some records dating back to the beginning of the 18th century. Results show that <span class="hlt">ice</span> duration significantly decreased over the last century. Change in <span class="hlt">ice</span> duration is affected by later freeze as well as (more dominantly) earlier breakup dates. Additionally, since the late 1980's there has been an increase of extreme events, meaning years with extremely short duration of <span class="hlt">ice</span> <span class="hlt">cover</span>. The affect of temperature on the system was also examined. Using 113 years of temperature data, we empirically show how temperature changes affect the <span class="hlt">ice</span> duration in lakes at different latitudes as well as dependent on lake area, volume and depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012TCry....6.1435G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012TCry....6.1435G"><span>Ground penetrating radar detection of subsnow slush on <span class="hlt">ice-covered</span> lakes in interior Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gusmeroli, A.; Grosse, G.</p> <p>2012-12-01</p> <p>Lakes are abundant throughout the pan-Arctic region. For many of these lakes <span class="hlt">ice</span> <span class="hlt">cover</span> lasts for up to two thirds of the year. The frozen <span class="hlt">cover</span> allows human access to these lakes, which are therefore used for many subsistence and recreational activities, including water harvesting, fishing, and skiing. Safe traveling condition onto lakes may be compromised, however, when, after significant snowfall, the weight of the snow acts on the <span class="hlt">ice</span> and causes liquid water to spill through weak spots and overflow at the snow-<span class="hlt">ice</span> interface. Since visual detection of subsnow slush is almost impossible our understanding on overflow processes is still very limited and geophysical methods that allow water and slush detection are desirable. In this study we demonstrate that a commercially available, lightweight 1 GHz, ground penetrating radar system can detect and map extent and intensity of overflow. The strength of radar reflections from wet snow-<span class="hlt">ice</span> interfaces are at least twice as much in strength than returns from dry snow-<span class="hlt">ice</span> interface. The presence of overflow also affects the quality of radar returns from the <span class="hlt">base</span> of the lake <span class="hlt">ice</span>. During dry conditions we were able to profile <span class="hlt">ice</span> thickness of up to 1 m, conversely, we did not retrieve any <span class="hlt">ice</span>-water returns in areas affected by overflow.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43J..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43J..05S"><span>Integrating Observations and Models to Better Understand a Changing Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J. C.</p> <p>2017-12-01</p> <p>TThe loss of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has captured the world's attention. While much attention has been paid to the summer <span class="hlt">ice</span> loss, changes are not limited to summer. The last few winters have seen record low sea <span class="hlt">ice</span> extents, with 2017 marking the 3rdyear in a row with a new record low for the winter maximum extent. More surprising is the number of consecutive months between January 2016 through April 2017 with <span class="hlt">ice</span> extent anomalies more than 2 standard deviations below the 1981-2010 mean. Additionally, October 2016 through April 2017 saw 7 consecutive months with record low extents, something that had not happened before in the last 4 decades of satellite observations. As larger parts of the Arctic Ocean become <span class="hlt">ice</span>-free in summer, regional seas gradually transition from a perennial to a seasonal <span class="hlt">ice</span> <span class="hlt">cover</span>. The Barents Sea is already only seasonally <span class="hlt">ice</span> <span class="hlt">covered</span>, whereas the Kara Sea has recently lost most of its summer <span class="hlt">ice</span> and is thereby starting to become a seasonally <span class="hlt">ice</span> <span class="hlt">covered</span> region. These changes serve as harbinger for what's to come for other Arctic seas. Given the rapid pace of change, there is an urgent need to improve our understanding of the drivers behind Arctic sea <span class="hlt">ice</span> loss, the implications of this <span class="hlt">ice</span> loss and to predict future changes to better inform policy makers. Climate models play a fundamental role in helping us synthesize the complex elements of the Arctic sea <span class="hlt">ice</span> system yet generally fail to simulate key features of the sea <span class="hlt">ice</span> system and the pace of sea <span class="hlt">ice</span> loss. Nevertheless, modeling advances continue to provide better means of diagnosing sea <span class="hlt">ice</span> change, and new insights are likely to be gained with model output from the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The CMIP6 Sea-<span class="hlt">Ice</span> Model Intercomparison Project (SIMIP) aim is to better understand biases and errors in sea <span class="hlt">ice</span> simulations so that we can improve our understanding of the likely future evolution of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> and its impacts on global climate. To</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840066094&hterms=growth+pole&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgrowth%2Bpole','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840066094&hterms=growth+pole&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgrowth%2Bpole"><span>Concentration gradients and growth/decay characteristics of the seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, J. C.; Zwally, H. J.</p> <p>1984-01-01</p> <p>The characteristics of sea <span class="hlt">ice</span> <span class="hlt">cover</span> in both hemispheres are analyzed and compared. The areal sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the entire polar regions and in various geographical sectors is quantified for various concentration intervals and is analyzed in a consistent manner. Radial profiles of brightness temperatures from the poles across the marginal zone are also evaluated at different transects along regular longitudinal intervals during different times of the year. These radial profiles provide statistical information about the <span class="hlt">ice</span> concentration gradients and the rates at which the <span class="hlt">ice</span> edge advances or retreats during a complete annual cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1203F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1203F"><span>Fragmentation and melting of the seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feltham, D. L.; Bateson, A.; Schroeder, D.; Ridley, J. K.; Aksenov, Y.</p> <p>2017-12-01</p> <p>Recent years have seen a rapid reduction in the summer extent of Arctic sea <span class="hlt">ice</span>. This trend has implications for navigation, oil exploration, wildlife, and local communities. Furthermore the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> impacts the exchange of heat and momentum between the ocean and atmosphere with significant teleconnections across the climate system, particularly mid to low latitudes in the Northern Hemisphere. The treatment of melting and break-up processes of the seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> within climate models is currently limited. In particular floes are assumed to have a uniform size which does not evolve with time. Observations suggest however that floe sizes can be modelled as truncated power law distributions, with different exponents for smaller and larger floes. This study aims to examine factors controlling the floe size distribution in the seasonal and marginal <span class="hlt">ice</span> zone. This includes lateral melting, wave induced break-up of floes, and the feedback between floe size and the mixed ocean layer. These results are then used to quantify the proximate mechanisms of seasonal sea <span class="hlt">ice</span> reduction in a sea ice—ocean mixed layer model. Observations are used to assess and calibrate the model. The impacts of introducing these processes to the model will be discussed and the preliminary results of sensitivity and feedback studies will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013QSRv...79..122D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013QSRv...79..122D"><span>Reconstructing past sea <span class="hlt">ice</span> <span class="hlt">cover</span> of the Northern Hemisphere from dinocyst assemblages: status of the approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Vernal, Anne; Rochon, André; Fréchette, Bianca; Henry, Maryse; Radi, Taoufik; Solignac, Sandrine</p> <p>2013-11-01</p> <p>Dinocysts occur in a wide range of environmental conditions, including polar areas. We review here their use for the reconstruction of paleo sea <span class="hlt">ice</span> <span class="hlt">cover</span> in such environments. In the Arctic Ocean and subarctic seas characterized by dense sea <span class="hlt">ice</span> <span class="hlt">cover</span>, Islandinium minutum, Islandinium? cezare, Echinidinium karaense, Polykrikos sp. var. Arctic, Spiniferites elongatus-frigidus and Impagidinium pallidum are common and often occur with more cosmopolitan taxa such as Operculodinium centrocarpum sensu Wall & Dale, cyst of Pentapharsodinium dalei and Brigantedinium spp. Canonical correspondence analyses conducted on dinocyst assemblages illustrate relationships with sea surface parameters such as salinity, temperature, and sea <span class="hlt">ice</span> <span class="hlt">cover</span>. The application of the modern analogue technique permits quantitative reconstruction of past sea <span class="hlt">ice</span> <span class="hlt">cover</span>, which is expressed in terms of seasonal extent of sea <span class="hlt">ice</span> <span class="hlt">cover</span> (months per year with more than 50% of sea <span class="hlt">ice</span> concentration) or mean annual sea <span class="hlt">ice</span> concentration (in tenths). The accuracy of reconstructions or root mean square error of prediction (RMSEP) is ±1.1 over 10, which corresponds to perennial sea <span class="hlt">ice</span>. Such an error is close to the interannual variability (standard deviation) of observed sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Mismatch between the time interval of instrumental data used as reference (1953-2000) and the time interval represented by dinocyst populations in surface sediment samples, which may <span class="hlt">cover</span> decades if not centuries, is another source of error. Despite uncertainties, dinocyst assemblages are useful for making quantitative reconstruction of seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C41A0425S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C41A0425S"><span>Precipitation Impacts of a Shrinking Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J. C.; Frei, A.; Gong, G.; Ghatak, D.; Robinson, D. A.; Kindig, D.</p> <p>2009-12-01</p> <p>Since the beginning of the modern satellite record in October 1978, the extent of Arctic sea <span class="hlt">ice</span> has declined in all months, with the strongest downward trend at the end of the melt season in September. Recently the September trends have accelerated. Through 2001, the extent of September sea <span class="hlt">ice</span> was decreasing at a rate of -7 per cent per decade. By 2006, the rate of decrease had risen to -8.9 per cent per decade. In September 2007, Arctic sea <span class="hlt">ice</span> extent fell to its lowest level recorded, 23 per cent below the previous record set in 2005, boosting the downward trend to -10.7 per cent per decade. <span class="hlt">Ice</span> extent in September 2008 was the second lowest in the satellite record. Including 2008, the trend in September sea <span class="hlt">ice</span> extent stands at -11.8 percent per decade. Compared to the 1970s, September <span class="hlt">ice</span> extent has retreated by 40 per cent. Summer 2009 looks to repeat the anomalously low <span class="hlt">ice</span> conditions that characterized the last couple of years. Scientists have long expected that a shrinking Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> will lead to strong warming of the overlying atmosphere, and as a result, affect atmospheric circulation and precipitation patterns. Recent results show clear evidence of Arctic warming linked to declining <span class="hlt">ice</span> extent, yet observational evidence for responses of atmospheric circulation and precipitation patterns is just beginning to emerge. Rising air temperatures should lead to an increase in the moisture holding capacity of the atmosphere, with the potential to impact autumn precipitation. Although climate models predict a hemispheric wide decrease in snow <span class="hlt">cover</span> as atmospheric concentrations of GHGs increase, increased precipitation, particular in autumn and winter may result as the Arctic transitions towards a seasonally <span class="hlt">ice</span> free state. In this study we use atmospheric reanalysis data and a cyclone tracking algorithm to investigate the influence of recent extreme <span class="hlt">ice</span> loss years on precipitation patterns in the Arctic and the Northern Hemisphere. Results show</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980237537','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980237537"><span>Spatial Distribution of Trends and Seasonality in the Hemispheric Sea <span class="hlt">Ice</span> <span class="hlt">Covers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gloersen, P.; Parkinson, C. L.; Cavalieri, D. J.; Cosmiso, J. C.; Zwally, H. J.</p> <p>1998-01-01</p> <p>We extend earlier analyses of a 9-year sea <span class="hlt">ice</span> data set that described the local seasonal and trend variations in each of the hemispheric sea <span class="hlt">ice</span> <span class="hlt">covers</span> to the recently merged 18.2-year sea <span class="hlt">ice</span> record from four satellite instruments. The seasonal cycle characteristics remain essentially the same as for the shorter time series, but the local trends are markedly different, in some cases reversing sign. The sign reversal reflects the lack of a consistent long-term trend and could be the result of localized long-term oscillations in the hemispheric sea <span class="hlt">ice</span> <span class="hlt">covers</span>. By combining the separate hemispheric sea <span class="hlt">ice</span> records into a global one, we have shown that there are statistically significant net decreases in the sea <span class="hlt">ice</span> coverage on a global scale. The change in the global sea <span class="hlt">ice</span> extent, is -0.01 +/- 0.003 x 10(exp 6) sq km per decade. The decrease in the areal coverage of the sea <span class="hlt">ice</span> is only slightly smaller, so that the difference in the two, the open water within the packs, has no statistically significant change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018IzAOP..54...65I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018IzAOP..54...65I"><span>The Effect of Seasonal Variability of Atlantic Water on the Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, V. V.; Repina, I. A.</p> <p>2018-01-01</p> <p>Under the influence of global warming, the sea <span class="hlt">ice</span> in the Arctic Ocean (AO) is expected to reduce with a transition toward a seasonal <span class="hlt">ice</span> <span class="hlt">cover</span> by the end of this century. A comparison of climate-model predictions with measurements shows that the actual rate of <span class="hlt">ice</span> <span class="hlt">cover</span> decay in the AO is higher than the predicted one. This paper argues that the rapid shrinking of the Arctic summer <span class="hlt">ice</span> <span class="hlt">cover</span> is due to its increased seasonality, while seasonal oscillations of the Atlantic origin water temperature create favorable conditions for the formation of negative anomalies in the <span class="hlt">ice-cover</span> area in winter. The basis for this hypothesis is the fundamental possibility of the activation of positive feedback provided by a specific feature of the seasonal cycle of the inflowing Atlantic origin water and the peaking of temperature in the Nansen Basin in midwinter. The recently accelerated reduction in the summer <span class="hlt">ice</span> <span class="hlt">cover</span> in the AO leads to an increased accumulation of heat in the upper ocean layer during the summer season. The extra heat content of the upper ocean layer favors prerequisite conditions for winter thermohaline convection and the transfer of heat from the Atlantic water (AW) layer to the <span class="hlt">ice</span> <span class="hlt">cover</span>. This, in turn, contributes to further <span class="hlt">ice</span> thinning and a decrease in <span class="hlt">ice</span> concentration, accelerated melting in summer, and a greater accumulation of heat in the ocean by the end of the following summer. An important role is played by the seasonal variability of the temperature of AW, which forms on the border between the North European and Arctic basins. The phase of seasonal oscillation changes while the AW is moving through the Nansen Basin. As a result, the timing of temperature peak shifts from summer to winter, additionally contributing to enhanced <span class="hlt">ice</span> melting in winter. The formulated theoretical concept is substantiated by a simplified mathematical model and comparison with observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170009008&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsea','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170009008&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsea"><span>Variability and Trends in the Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span>: Results from Different Techniques</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Meier, Walter N.; Gersten, Robert</p> <p>2017-01-01</p> <p>Variability and trend studies of sea <span class="hlt">ice</span> in the Arctic have been conducted using products derived from the same raw passive microwave data but by different groups using different algorithms. This study provides consistency assessment of four of the leading products, namely, Goddard Bootstrap (SB2), Goddard NASA Team (NT1), EUMETSAT Ocean and Sea <span class="hlt">Ice</span> Satellite Application Facility (OSI-SAF 1.2), and Hadley HadISST 2.2 data in evaluating variability and trends in the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>. All four provide generally similar <span class="hlt">ice</span> patterns but significant disagreements in <span class="hlt">ice</span> concentration distributions especially in the marginal <span class="hlt">ice</span> zone and adjacent regions in winter and meltponded areas in summer. The discrepancies are primarily due to different ways the four techniques account for occurrences of new <span class="hlt">ice</span> and meltponding. However, results show that the different products generally provide consistent and similar representation of the state of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Hadley and NT1 data usually provide the highest and lowest monthly <span class="hlt">ice</span> extents, respectively. The Hadley data also show the lowest trends in <span class="hlt">ice</span> extent and <span class="hlt">ice</span> area at negative 3.88 percent decade and negative 4.37 percent decade, respectively, compared to an average of negative 4.36 percent decade and negative 4.57 percent decade for all four. Trend maps also show similar spatial distribution for all four with the largest negative trends occurring at the Kara/Barents Sea and Beaufort Sea regions, where sea <span class="hlt">ice</span> has been retreating the fastest. The good agreement of the trends especially with updated data provides strong confidence in the quantification of the rate of decline in the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19475938','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19475938"><span>Composition and biodegradation of a synthetic oil spilled on the perennial <span class="hlt">ice</span> <span class="hlt">cover</span> of Lake Fryxell, Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jaraula, Caroline M B; Kenig, Fabien; Doran, Peter T; Priscu, John C; Welch, Kathleen A</p> <p>2009-04-15</p> <p>A helicopter crashed in January 2003 on the 5 m-thick perennial <span class="hlt">ice</span> <span class="hlt">cover</span> of Lake Fryxell, spilling synthetic turbine oil Aeroshell 500. Molecular compositions of the oils were analyzed by gas chromatography-mass spectrometry and compared to the composition of contaminants in <span class="hlt">ice</span>, meltwater, and sediments collected a year after the accident. Aeroshell 500 is <span class="hlt">based</span> on C20-C33 Pentaerythritol triesters (PET) with C5-C10 fatty acids susbstituents and contain a number of antioxidant additives, such as tricresyl phosphates. Biodegradation of this oil in the <span class="hlt">ice</span> <span class="hlt">cover</span> occurs when sediments are present PETs with short fatty acids substituents are preferentially degraded, whereas long chain fatty acids seem to hinder esters from hydrolysis by esterase derived from the microbial assemblage. It remains to be seen if the microbial ecosystem can degrade tricresyl phosphates. These more recalcitrant PET species and tricresyl phosphates are likely to persist and comprise the contaminants that may eventually cross the <span class="hlt">ice</span> <span class="hlt">cover</span> to reach the pristine lake water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.nsf.gov/pubs/2005/nsf0539/nsf0539_5.pdf','USGSPUBS'); return false;" href="http://www.nsf.gov/pubs/2005/nsf0539/nsf0539_5.pdf"><span>Correlated declines in Pacific arctic snow and sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stone, Robert P.; Douglas, David C.; Belchansky, Gennady I.; Drobot, Sheldon</p> <p>2005-01-01</p> <p>Simulations of future climate suggest that global warming will reduce Arctic snow and <span class="hlt">ice</span> <span class="hlt">cover</span>, resulting in decreased surface albedo (reflectivity). Lowering of the surface albedo leads to further warming by increasing solar absorption at the surface. This phenomenon is referred to as “temperature–albedo feedback.” Anticipation of such a feedback is one reason why scientists look to the Arctic for early indications of global warming. Much of the Arctic has warmed significantly. Northern Hemisphere snow <span class="hlt">cover</span> has decreased, and sea <span class="hlt">ice</span> has diminished in area and thickness. As reported in the Arctic Climate Impact Assessment in 2004, the trends are considered to be outside the range of natural variability, implicating global warming as an underlying cause. Changing climatic conditions in the high northern latitudes have influenced biogeochemical cycles on a broad scale. Warming has already affected the sea <span class="hlt">ice</span>, the tundra, the plants, the animals, and the indigenous populations that depend on them. Changing annual cycles of snow and sea <span class="hlt">ice</span> also affect sources and sinks of important greenhouse gases (such as carbon dioxide and methane), further complicating feedbacks involving the global budgets of these important constituents. For instance, thawing permafrost increases the extent of tundra wetlands and lakes, releasing greater amounts of methane into the atmosphere. Variable sea <span class="hlt">ice</span> <span class="hlt">cover</span> may affect the hemispheric carbon budget by altering the ocean–atmosphere exchange of carbon dioxide. There is growing concern that amplification of global warming in the Arctic will have far-reaching effects on lower latitude climate through these feedback mechanisms. Despite the diverse and convincing observational evidence that the Arctic environment is changing, it remains unclear whether these changes are anthropogenically forced or result from natural variations of the climate system. A better understanding of what controls the seasonal distributions of snow and <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015207','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015207"><span>Regional Changes in the Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> and <span class="hlt">Ice</span> Production in the Antarctic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.</p> <p>2011-01-01</p> <p>Coastal polynyas around the Antarctic continent have been regarded as sea <span class="hlt">ice</span> factories because of high <span class="hlt">ice</span> production rates in these regions. The observation of a positive trend in the extent of Antarctic sea <span class="hlt">ice</span> during the satellite era has been intriguing in light of the observed rapid decline of the <span class="hlt">ice</span> extent in the Arctic. The results of analysis of the time series of passive microwave data indicate large regional variability with the trends being strongly positive in the Ross Sea, strongly negative in the Bellingshausen/Amundsen Seas and close to zero in the other regions. The atmospheric circulation in the Antarctic is controlled mainly by the Southern Annular Mode (SAM) and the marginal <span class="hlt">ice</span> zone around the continent shows an alternating pattern of advance and retreat suggesting the presence of a propagating wave (called Antarctic Circumpolar Wave) around the circumpolar region. The results of analysis of the passive microwave data suggest that the positive trend in the Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> could be caused primarily by enhanced <span class="hlt">ice</span> production in the Ross Sea that may be associated with more persistent and larger coastal polynyas in the region. Over the Ross Sea shelf, analysis of sea <span class="hlt">ice</span> drift data from 1992 to 2008 yields a positive rate-of-increase in the net <span class="hlt">ice</span> export of about 30,000 km2 per year. For a characteristic <span class="hlt">ice</span> thickness of 0.6 m, this yields a volume transport of about 20 km3/year, which is almost identical, within error bars, to our estimate of the trend in <span class="hlt">ice</span> production. In addition to the possibility of changes in SAM, modeling studies have also indicated that the ozone hole may have a role in that it causes the deepening of the lows in the western Antarctic region thereby causing strong winds to occur offthe Ross-<span class="hlt">ice</span> shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25786966','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25786966"><span>Treatment of <span class="hlt">ice</span> <span class="hlt">cover</span> and other thin elastic layers with the parabolic equation method.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Collins, Michael D</p> <p>2015-03-01</p> <p>The parabolic equation method is extended to handle problems involving <span class="hlt">ice</span> <span class="hlt">cover</span> and other thin elastic layers. Parabolic equation solutions are <span class="hlt">based</span> on rational approximations that are designed using accuracy constraints to ensure that the propagating modes are handled properly and stability constrains to ensure that the non-propagating modes are annihilated. The non-propagating modes are especially problematic for problems involving thin elastic layers. It is demonstrated that stable results may be obtained for such problems by using rotated rational approximations [Milinazzo, Zala, and Brooke, J. Acoust. Soc. Am. 101, 760-766 (1997)] and generalizations of these approximations. The approach is applied to problems involving <span class="hlt">ice</span> <span class="hlt">cover</span> with variable thickness and sediment layers that taper to zero thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8068J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8068J"><span>Sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in the Nordic Seas and the sensitivity to Atlantic water temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jensen, Mari F.; Nisancioglu, Kerim H.; Spall, Michael A.</p> <p>2017-04-01</p> <p>Changes in the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. However, with its proximity to the warm Atlantic water, how a sea-<span class="hlt">ice</span> <span class="hlt">cover</span> can persist in the Nordic Seas is not well understood. In this study, we apply an eddy-resolving configuration of the Massachusetts Institute of Technology general circulation model with an idealized topography to study the presence of sea <span class="hlt">ice</span> in a Nordic Seas-like domain. We assume an infinite amount of warm Atlantic water present in the south by restoring the southern area to constant temperatures. The sea-surface temperatures are restored toward cold, atmospheric temperatures, and as a result, sea <span class="hlt">ice</span> is present in the interior of the domain. However, the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in the margins of the Nordic Seas, an area with a warm, cyclonic boundary current, is sensitive to the amount of heat entering the domain, i.e., the restoring temperature in the south. When the temperature of the warm, cyclonic boundary current is high, the margins are free of sea <span class="hlt">ice</span> and heat is released to the atmosphere. We show that with a small reduction in the temperature of the incoming Atlantic water, the Nordic Seas-like domain is fully <span class="hlt">covered</span> in sea <span class="hlt">ice</span>. Warm water is still entering the Nordic Seas, however, this happens at depths below a cold, fresh surface layer produced by melted sea <span class="hlt">ice</span>. Consequently, the heat release to the atmosphere is reduced along with the eddy heat fluxes. Results suggest a threshold value in the amount of heat entering the Nordic Seas before the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> disappears in the margins. We study the sensitivity of this threshold to changes in atmospheric temperatures and vertical diffusivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMTP..58..641T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMTP..58..641T"><span>Behavior of a semi-infinite <span class="hlt">ice</span> <span class="hlt">cover</span> under periodic dynamic impact</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tkacheva, L. A.</p> <p>2017-07-01</p> <p>Oscillations of a semi-infinite <span class="hlt">ice</span> <span class="hlt">cover</span> in an ideal incompressible liquid of finite depth under local time-periodic axisymmetric load are considered. The <span class="hlt">ice</span> <span class="hlt">cover</span> is simulated by a thin elastic plate of constant thickness. An analytical solution of the problem is obtained using the Wiener-Hopf method. The asymptotic behavior of the amplitudes of oscillations of the plate and the liquid in the far field is studied. It is shown that the propagation of waves in the far field is uneven: in some directions, the waves propagate with a significantly greater amplitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..180V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..180V"><span>Geophysical Investigations of Habitability in <span class="hlt">Ice-Covered</span> Ocean Worlds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vance, Steven D.; Panning, Mark P.; Stähler, Simon; Cammarano, Fabio; Bills, Bruce G.; Tobie, Gabriel; Kamata, Shunichi; Kedar, Sharon; Sotin, Christophe; Pike, William T.; Lorenz, Ralph; Huang, Hsin-Hua; Jackson, Jennifer M.; Banerdt, Bruce</p> <p>2018-01-01</p> <p>Geophysical measurements can reveal the structures and thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. We explore the variability and correlation of these parameters using 1-D internal structure models. We invoke thermodynamic consistency using available thermodynamics of aqueous MgSO4, NaCl (as seawater), and NH3; pure water <span class="hlt">ice</span> phases I, II, III, V, and VI; silicates; and any metallic core that may be present. Model results suggest, for Europa, that combinations of geophysical parameters might be used to distinguish an oxidized ocean dominated by MgSO4 from a more reduced ocean dominated by NaCl. In contrast with Jupiter's icy ocean moons, Titan and Enceladus have low-density rocky interiors, with minimal or no metallic core. The low-density rocky core of Enceladus may comprise hydrated minerals or anhydrous minerals with high porosity. <fi>Cassini</fi> gravity data for Titan indicate a high tidal potential Love number (k2>0.6), which requires a dense internal ocean (ρocean>1,200 kg m-3) and icy lithosphere thinner than 100 km. In that case, Titan may have little or no high-pressure <span class="hlt">ice</span>, or a surprisingly deep water-rock interface more than 500 km below the surface, <span class="hlt">covered</span> only by <span class="hlt">ice</span> VI. Ganymede's water-rock interface is the deepest among known ocean worlds, at around 800 km. Its ocean may contain multiple phases of high-pressure <span class="hlt">ice</span>, which will become buoyant if the ocean is sufficiently salty. Callisto's interior structure may be intermediate to those of Titan and Europa, with a water-rock interface 250 km below the surface <span class="hlt">covered</span> by <span class="hlt">ice</span> V but not <span class="hlt">ice</span> VI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRC..119.2327A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRC..119.2327A"><span>Implications of fractured Arctic perennial <span class="hlt">ice</span> <span class="hlt">cover</span> on thermodynamic and dynamic sea <span class="hlt">ice</span> processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asplin, Matthew G.; Scharien, Randall; Else, Brent; Howell, Stephen; Barber, David G.; Papakyriakou, Tim; Prinsenberg, Simon</p> <p>2014-04-01</p> <p>Decline of the Arctic summer minimum sea <span class="hlt">ice</span> extent is characterized by large expanses of open water in the Siberian, Laptev, Chukchi, and Beaufort Seas, and introduces large fetch distances in the Arctic Ocean. Long waves can propagate deep into the pack <span class="hlt">ice</span>, thereby causing flexural swell and failure of the sea <span class="hlt">ice</span>. This process shifts the floe size diameter distribution smaller, increases floe surface area, and thereby affects sea <span class="hlt">ice</span> dynamic and thermodynamic processes. The results of Radarsat-2 imagery analysis show that a flexural fracture event which occurred in the Beaufort Sea region on 6 September 2009 affected ˜40,000 km2. Open water fractional area in the area affected initially decreased from 3.7% to 2.7%, but later increased to ˜20% following wind-forced divergence of the <span class="hlt">ice</span> pack. Energy available for lateral melting was assessed by estimating the change in energy entrainment from longwave and shortwave radiation in the mixed-layer of the ocean following flexural fracture. 11.54 MJ m-2 of additional energy for lateral melting of <span class="hlt">ice</span> floes was identified in affected areas. The impact of this process in future Arctic sea <span class="hlt">ice</span> melt seasons was assessed using estimations of earlier occurrences of fracture during the melt season, and is discussed in context with ocean heat fluxes, atmospheric mixing of the ocean mixed layer, and declining sea <span class="hlt">ice</span> <span class="hlt">cover</span>. We conclude that this process is an important positive feedback to Arctic sea <span class="hlt">ice</span> loss, and timing of initiation is critical in how it affects sea <span class="hlt">ice</span> thermodynamic and dynamic processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.6395N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.6395N"><span>Measured and Modelled Tidal Circulation Under <span class="hlt">Ice</span> <span class="hlt">Covered</span> Van Mijenforden</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nilsen, F.</p> <p></p> <p>The observation and model area Van Mijenfjorden is situated at the west coast of Spits- bergen. An area of 533 km2 makes it the second largest fjord on Spitsbergen and the distance from the head to the mouth of the fjord is approximately 70 km. An 8.5km long and 1km wide island, Akseløya, is lying across the fjord mouth and blocking exchanges between the fjord and the coastal water masses outside. The sound Aksel- sundet on the northern side of the island is 1km wide and has a sill at 34m depth. On the southern side an islet, Mariaholmen, is between two sounds that are 200m wide and 2m deep, and 500m wide and 12m deep. Strong tidal currents exist in these sounds. Van Mijenfjorden has special <span class="hlt">ice</span> conditions in that Akseløya almost closes the fjord, and comparatively little <span class="hlt">ice</span> comes in from west. On the other hand, there are periods with fast <span class="hlt">ice</span> in the fjord inside Akseløya longer than in other places, as the sea waves have little chance to break up fast <span class="hlt">ice</span> here, or delay <span class="hlt">ice</span> formation in autumn/winter. Van Mijenfjorden is often separated into two basins by a sill at 30m depth. The inner basin is typical 5km wide and has a maximum depth of 80m, while the outer basin is on average 10 km wide and has a maximum depth of 115m. Hydrographic measurements have been conducted since 1958 and up to the present. Through the last decade, The University Courses on Svalbard (UNIS) has used this fjord as a laboratory for their student excursions, in connection to courses in air-<span class="hlt">ice</span>- ocean interaction and master programs, and build up an oceanographic data <span class="hlt">base</span>. In this work, focus is put on the wintertime situation and the circulation under an <span class="hlt">ice</span> <span class="hlt">covered</span> fjord. Measurements show a mean cyclonic circulation pattern in the outer basin with tidal oscillation (mainly M2) superposed on this mean vector. A three- dimensional sigma layered numerical model called Bergen Ocean Model (BOM) was used to simulate the circulation in Van Mijenfjorden with only tidal forcing. The four most</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>Satellite microwave and in situ observations of the Weddell Sea <span class="hlt">ice</span> <span class="hlt">cover</span> and its marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, J. C.; Sullivan, C. W.</p> <p>1986-01-01</p> <p>The radiative and physical characteristics of the Weddell Sea <span class="hlt">ice</span> <span class="hlt">cover</span> and its marginal <span class="hlt">ice</span> zone are analyzed using multichannel satellite passive microwave data and ship and helicopter observations obtained during the 1983 Antarctic Marine Ecosystem Research. Winter and spring brightness temperatures are examined; spatial variability in the brightness temperatures of consolidated <span class="hlt">ice</span> in winter and spring cyclic increases and decrease in brightness temperatures of consolidated <span class="hlt">ice</span> with an amplitude of 50 K at 37 GHz and 20 K at 18 GHz are observed. The roles of variations in air temperature and surface characteristics in the variability of spring brightness temperatures are investigated. <span class="hlt">Ice</span> concentrations are derived using the frequency and polarization techniques, and the data are compared with the helicopter and ship observations. Temporal changes in the <span class="hlt">ice</span> margin structure and the mass balance of fresh water and of biological features of the marginal <span class="hlt">ice</span> zone are studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170000316','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170000316"><span><span class="hlt">Ice-Covered</span> Lakes in Gale Crater Mars: The Cold and Wet Hypothesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kling, A. M.; Haberle, R. M.; Mckay, C. P.; Bristow, T. F.</p> <p>2016-01-01</p> <p>Recent geological discoveries from the Mars Science Laboratory provide evidence that Gale crater may have intermittently hosted a fluvio-lacustine environment during the Hesperian, with individual lakes lasting for a period of tens to hundreds of thousands of years. (Grotzinger et al., Science, 350 (6257), 2015). Estimates of the CO2 content of the atmosphere at the time the Gale sediments formed are far less than needed by any climate model to warm early Mars (Bristow et al., Geology, submitted), given the low solar energy input available at Mars 3.5 Gya. We have therefore explored the possibility that the lakes in Gale during the Hesperian were perennially <span class="hlt">covered</span> with <span class="hlt">ice</span> using the Antarctic Lakes as an analog. Using our best estimate for the annual mean surface temperature at Gale at this time (approx. 230K) we computed the thickness of an <span class="hlt">ice-covered</span> lake. These thickness range from 10-30 meters depending on the ablation rate and <span class="hlt">ice</span> transparency and would likely inhibit sediments from entering the lake. Thus, a first conclusion is that the <span class="hlt">ice</span> must not be too cold. Raising the mean temperature to 245K is challenging, but not quite as hard as reaching 273K. We found that a mean annual temperature of 245K <span class="hlt">ice</span> thicknesses range from 3-10 meters. These values are comparable to the range of those for the Antarctic lakes (3-6 m), and are not implausible. And they are not so thick that sediments cannot penetrate the <span class="hlt">ice</span>. For the <span class="hlt">ice-covered</span> lake hypothesis to work, however, a melt water source is needed. This could come from subaqueous melting of a glacial dam in contact with the lakes (as is the case for Lake Untersee) or from seasonal melt water from nearby glaciers (as is the case for the Dry Valley lakes). More work is needed to better assess these possibilities. However, the main advantage of the <span class="hlt">ice-covered</span> lake model (and the main reason we pursued it) is that it relaxes the requirement for a long-lived active hydrological cycle involving rainfall and runoff</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020842','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020842"><span>Evidence of deep circulation in two perennially <span class="hlt">ice-covered</span> Antarctic lakes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tyler, S.W.; Cook, P.G.; Butt, A.Z.; Thomas, J.M.; Doran, P.T.; Lyons, W.B.</p> <p>1998-01-01</p> <p>The perennial <span class="hlt">ice</span> <span class="hlt">covers</span> found on many of the lakes in the McMurdo Dry Valley region of the Antarctic have been postulated to severely limit mixing and convective turnover of these unique lakes. In this work, we utilize chlorofluorocarbon (CFC) concentration profiles from Lakes Hoare and Fryxell in the McMurdo Dry Valley to determine the extent of deep vertical mixing occurring over the last 50 years. Near the <span class="hlt">ice</span>-water interface, CFC concentrations in both lakes were well above saturation, in accordance with atmospheric gas supersaturations resulting from freezing under the perennial <span class="hlt">ice</span> <span class="hlt">covers</span>. Evidence of mixing throughout the water column at Lake Hoare was confirmed by the presence of CFCs throughout the water column and suggests vertical mixing times of 20-30 years. In Lake Fryxell, CFC-11, CFC-12, and CFC-113 were found in the upper water column; however, degradation of CFC-11 and CFC-12 in the anoxic bottom waters appears to be occurring with CFC-113 only present in these bottom waters. The presence of CFC-113 in the bottom waters, in conjunction with previous work detecting tritium in these waters, strongly argues for the presence of convective mixing in Lake Fryxell. The evidence for deep mixing in these lakes may be an important, yet overlooked, phenomenon in the limnology of perennially <span class="hlt">ice-covered</span> lakes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1113700S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1113700S"><span>Nature and History of Cenozoic Polar <span class="hlt">Ice</span> <span class="hlt">Covers</span>: The Case of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spielhagen, R.; Thiede, J.</p> <p>2009-04-01</p> <p>The nature of the modern climate System is characterized by steep temperature gradients between the tropical and polar climatic zones and finds its most spectacular expression in the formation of <span class="hlt">ice</span> caps in high Northern and Southern latitudes. While polar regions of Planet Earth have been glaciated repeatedly in the long course of their geological history, the Cenozoic transition from a „greenhouse" to an „icehouse" has in fact produced a unique climatic scenario with bipolar glacation, different from all previous glacial events. The Greenland <span class="hlt">ice</span> sheet is a remainder of the Northern Hemisphere last glacial maximum <span class="hlt">ice</span> sheets and represents hence a spectacular anomaly. Geological records from Tertiary and Quaternary terrestrial and oceanic sections have documented the presence of <span class="hlt">ice</span> caps and sea <span class="hlt">ice</span> <span class="hlt">covers</span> both on the Southern as well on the Northern hemisphere since Eocene times, aqpprox. 45 Mio. years ago. While this was well known in the case of Antarctica already for some time, previous ideas about the origin of Northern hemisphere glaciation during Pliocene times (approx. 2-3 Mio. years ago) have been superceded by the dramatic findings of coarse, terrigenous <span class="hlt">ice</span> rafted detritus in Eocene sediments from Lomonosov Ridge (close to the North Pole) apparently slightly older than the oldest Antarctic records of <span class="hlt">ice</span> rafting.The histories of the onset of Cenozoic glaciation in high Northern and Southern latitudes remain enigmatic and are presently subjects of international geological drilling projects, with prospects to reveal some of their secrets over the coming decades. By virtue of the physical porperties of <span class="hlt">ice</span> and the processes controlling the dynamics of the turn-over of the <span class="hlt">ice</span>-sheets only young records of glacial <span class="hlt">ice</span> caps on Antarctica and on Greemnland have been preserved, on Greenland with <span class="hlt">ice</span> probably not older than a few hundred thousand years, on Antarctica potentially as old as 1.5-2 Mio. years. Deep-sea cores with their records od <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28851908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28851908"><span>Arctic Ocean sea <span class="hlt">ice</span> <span class="hlt">cover</span> during the penultimate glacial and the last interglacial.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stein, Ruediger; Fahl, Kirsten; Gierz, Paul; Niessen, Frank; Lohmann, Gerrit</p> <p>2017-08-29</p> <p>Coinciding with global warming, Arctic sea <span class="hlt">ice</span> has rapidly decreased during the last four decades and climate scenarios suggest that sea <span class="hlt">ice</span> may completely disappear during summer within the next about 50-100 years. Here we produce Arctic sea <span class="hlt">ice</span> biomarker proxy records for the penultimate glacial (Marine Isotope Stage 6) and the subsequent last interglacial (Marine Isotope Stage 5e). The latter is a time interval when the high latitudes were significantly warmer than today. We document that even under such warmer climate conditions, sea <span class="hlt">ice</span> existed in the central Arctic Ocean during summer, whereas sea <span class="hlt">ice</span> was significantly reduced along the Barents Sea continental margin influenced by Atlantic Water inflow. Our proxy reconstruction of the last interglacial sea <span class="hlt">ice</span> <span class="hlt">cover</span> is supported by climate simulations, although some proxy data/model inconsistencies still exist. During late Marine Isotope Stage 6, polynya-type conditions occurred off the major <span class="hlt">ice</span> sheets along the northern Barents and East Siberian continental margins, contradicting a giant Marine Isotope Stage 6 <span class="hlt">ice</span> shelf that <span class="hlt">covered</span> the entire Arctic Ocean.Coinciding with global warming, Arctic sea <span class="hlt">ice</span> has rapidly decreased during the last four decades. Here, using biomarker records, the authors show that permanent sea <span class="hlt">ice</span> was still present in the central Arctic Ocean during the last interglacial, when high latitudes were warmer than present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H13N..09G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H13N..09G"><span>Heating the <span class="hlt">Ice-Covered</span> Lakes of the McMurdo Dry Valleys, Antarctica - Decadal Trends in Heat Content, <span class="hlt">Ice</span> Thickness, and Heat Exchange</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gooseff, M. N.; Priscu, J. C.; Doran, P. T.; Chiuchiolo, A.; Obryk, M.</p> <p>2014-12-01</p> <p>Lakes integrate landscape processes and climate conditions. Most of the permanently <span class="hlt">ice-covered</span> lakes in the McMurdo Dry Valleys, Antarctica are closed basin, receiving glacial melt water from streams for 10-12 weeks per year. Lake levels rise during the austral summer are balanced by sublimation of <span class="hlt">ice</span> <span class="hlt">covers</span> (year-round) and evaporation of open water moats (summer only). Vertical profiles of water temperature have been measured in three lakes in Taylor Valley since 1988. Up to 2002, lake levels were dropping, <span class="hlt">ice</span> <span class="hlt">covers</span> were thickening, and total heat contents were decreasing. These lakes have been gaining heat since the mid-2000s, at rates as high as 19.5x1014 cal/decade). Since 2002, lake levels have risen substantially (as much as 2.5 m), and <span class="hlt">ice</span> <span class="hlt">covers</span> have thinned (1.5 m on average). Analyses of lake <span class="hlt">ice</span> thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from latent heat released when <span class="hlt">ice-covers</span> form during the winter. An aditional source of heat to the lakes is water inflows from streams and direct glacieal melt. Mean lake temperatures in the past few years have stabilized or cooled, despite increases in lake level and total heat content, suggesting increased direct inflow of meltwater from glaciers. These results indicate that McMurdo Dry Valley lakes are sensitive indicators of climate processes in this polar desert landscape and demonstrate the importance of long-term data sets when addressing the effects of climate on ecosystem processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C41B0347M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C41B0347M"><span>Multi-Decadal Comparison between Clean-<span class="hlt">Ice</span> and Debris-<span class="hlt">Covered</span> Glaciers in the Eastern Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurer, J. M.; Rupper, S.</p> <p>2014-12-01</p> <p>Himalayan glaciers are important natural resources and climatic indicators. Many of these glaciers have debris-<span class="hlt">covered</span> ablation zones, while others are mostly clean <span class="hlt">ice</span>. Regarding glacier dynamics, it is expected that debris-<span class="hlt">covered</span> glaciers will respond differently to atmospheric warming compared to clean <span class="hlt">ice</span> glaciers. In the Bhutanese Himalaya, there are (1) north flowing clean-<span class="hlt">ice</span> glaciers with high velocities, likely with large amounts of basal sliding, and (2) south flowing debris-<span class="hlt">covered</span> glaciers with slow velocities, thermokarst features, and influenced more by the Indian Summer Monsoon. This region, therefore, is ideal for comparing the dynamical response of clean-<span class="hlt">ice</span> versus debris-<span class="hlt">covered</span> glaciers to climatic change. In particular, previous studies have suggested the north flowing glaciers are likely adjusting more dynamically (i.e. retreating) in response to climate variations, while the south flowing glaciers are likely experiencing downwasting, with stagnant termini locations. We test this hypothesis by assessing glacier changes over three decades in the Bhutan region using a newly-developed workflow to extract DEMs and orthorectified imagery from both 1976 historical spy satellite images and 2006 ASTER images. DEM differencing for both debris-<span class="hlt">covered</span> and clean glaciers allows for quantification of glacier surface elevation changes, while orthorectified imagery allows for measuring changes in glacier termini. The same stereo-matching, denoising, and georeferencing methodology is used on both datasets to ensure consistency, while the three decade timespan allows for a better signal to noise ratio compared to studies performed on shorter timescales. The results of these analyses highlight the similarities and differences in the decadal response of clean-<span class="hlt">ice</span> and debris-<span class="hlt">covered</span> glaciers to climatic change, and provide insights into the complex dynamics of debris-<span class="hlt">covered</span> glaciers in the monsoonal Himalayas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810332R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810332R"><span>Trends in annual minimum exposed snow and <span class="hlt">ice</span> <span class="hlt">cover</span> in High Mountain Asia from MODIS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rittger, Karl; Brodzik, Mary J.; Painter, Thomas H.; Racoviteanu, Adina; Armstrong, Richard; Dozier, Jeff</p> <p>2016-04-01</p> <p>Though a relatively short record on climatological scales, data from the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000-2014 can be used to evaluate changes in the cryosphere and provide a robust baseline for future observations from space. We use the MODIS Snow <span class="hlt">Covered</span> Area and Grain size (MODSCAG) algorithm, <span class="hlt">based</span> on spectral mixture analysis, to estimate daily fractional snow and <span class="hlt">ice</span> <span class="hlt">cover</span> and the MODICE Persistent <span class="hlt">Ice</span> (MODICE) algorithm to estimate the annual minimum snow and <span class="hlt">ice</span> fraction (fSCA) for each year from 2000 to 2014 in High Mountain Asia. We have found that MODSCAG performs better than other algorithms, such as the Normalized Difference Index (NDSI), at detecting snow. We use MODICE because it minimizes false positives (compared to maximum extents), for example, when bright soils or clouds are incorrectly classified as snow, a common problem with optical satellite snow mapping. We analyze changes in area using the annual MODICE maps of minimum snow and <span class="hlt">ice</span> <span class="hlt">cover</span> for over 15,000 individual glaciers as defined by the Randolph Glacier Inventory (RGI) Version 5, focusing on the Amu Darya, Syr Darya, Upper Indus, Ganges, and Brahmaputra River basins. For each glacier with an area of at least 1 km2 as defined by RGI, we sum the total minimum snow and <span class="hlt">ice</span> <span class="hlt">covered</span> area for each year from 2000 to 2014 and estimate the trends in area loss or gain. We find the largest loss in annual minimum snow and <span class="hlt">ice</span> extent for 2000-2014 in the Brahmaputra and Ganges with 57% and 40%, respectively, of analyzed glaciers with significant losses (p-value<0.05). In the Upper Indus River basin, we see both gains and losses in minimum snow and <span class="hlt">ice</span> extent, but more glaciers with losses than gains. Our analysis shows that a smaller proportion of glaciers in the Amu Darya and Syr Darya are experiencing significant changes in minimum snow and <span class="hlt">ice</span> extent (3.5% and 12.2%), possibly because more of the glaciers in this region are smaller than 1 km2 than in the Indus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12208033','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12208033"><span>Influence of <span class="hlt">ice</span> and snow <span class="hlt">covers</span> on the UV exposure of terrestrial microbial communities: dosimetric studies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cockell, Charles S; Rettberg, Petra; Horneck, Gerda; Wynn-Williams, David D; Scherer, Kerstin; Gugg-Helminger, Anton</p> <p>2002-08-01</p> <p>Bacillus subtilis spore biological dosimeters and electronic dosimeters were used to investigate the exposure of terrestrial microbial communities in micro-habitats <span class="hlt">covered</span> by snow and <span class="hlt">ice</span> in Antarctica. The melting of snow <span class="hlt">covers</span> of between 5- and 15-cm thickness, depending on age and heterogeneity, could increase B. subtilis spore inactivation by up to an order of magnitude, a relative increase twice that caused by a 50% ozone depletion. Within the snow-pack at depths of less than approximately 3 cm snow algae could receive two to three times the DNA-weighted irradiance they would receive on bare ground. At the edge of the snow-pack, warming of low albedo soils resulted in the formation of overhangs that provided transient UV protection to thawed and growing microbial communities on the soils underneath. In shallow aquatic habitats, thin layers of heterogeneous <span class="hlt">ice</span> of a few millimetres thickness were found to reduce DNA-weighted irradiances by up to 55% compared to full-sky values with equivalent DNA-weighted diffuse attenuation coefficients (K(DNA)) of >200 m(-1). A 2-mm snow-encrusted <span class="hlt">ice</span> <span class="hlt">cover</span> on a pond was equivalent to 10 cm of <span class="hlt">ice</span> on a perennially <span class="hlt">ice</span> <span class="hlt">covered</span> lake. <span class="hlt">Ice</span> <span class="hlt">covers</span> also had the effect of stabilizing the UV exposure, which was often subject to rapid variations of up to 33% of the mean value caused by wind-rippling of the water surface. These data show that changing <span class="hlt">ice</span> and snow <span class="hlt">covers</span> cause relative changes in microbial UV exposure at least as great as those caused by changing ozone column abundance. Copyright 2002 Elsevier Science B.V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.3301J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.3301J"><span>The interaction between sea <span class="hlt">ice</span> and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jensen, Mari F.; Nilsson, Johan; Nisancioglu, Kerim H.</p> <p>2016-11-01</p> <p>Changes in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. In this study, we develop a simple conceptual model to examine how interactions between sea <span class="hlt">ice</span> and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea <span class="hlt">ice</span> <span class="hlt">covered</span> and salinity stratified Nordic Seas, and consists of a sea <span class="hlt">ice</span> component and a two-layer ocean. The sea <span class="hlt">ice</span> thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea <span class="hlt">ice</span> export. Whether sea <span class="hlt">ice</span> stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the diapycnal flow. In a system where the diapycnal flow increases with density differences, the sea <span class="hlt">ice</span> acts as a positive feedback on a freshwater perturbation. If the diapycnal flow decreases with density differences, the sea <span class="hlt">ice</span> acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea <span class="hlt">ice</span>. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea <span class="hlt">ice</span>. Generally, the unstable state is reached before the vertical density difference disappears, and the temperature of the deep ocean do not need to increase as much as previously thought to provoke abrupt changes in sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060038062&hterms=flower&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dflower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060038062&hterms=flower&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dflower"><span>(abstract) A Polarimetric Model for Effects of Brine Infiltrated Snow <span class="hlt">Cover</span> and Frost Flowers on Sea <span class="hlt">Ice</span> Backscatter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, S. V.; Kwok, R.; Yueh, S. H.</p> <p>1995-01-01</p> <p>A polarimetric scattering model is developed to study effects of snow <span class="hlt">cover</span> and frost flowers with brine infiltration on thin sea <span class="hlt">ice</span>. Leads containing thin sea <span class="hlt">ice</span> in the Artic icepack are important to heat exchange with the atmosphere and salt flux into the upper ocean. Surface characteristics of thin sea <span class="hlt">ice</span> in leads are dominated by the formation of frost flowers with high salinity. In many cases, the thin sea <span class="hlt">ice</span> layer is <span class="hlt">covered</span> by snow, which wicks up brine from sea <span class="hlt">ice</span> due to capillary force. Snow and frost flowers have a significant impact on polarimetric signatures of thin <span class="hlt">ice</span>, which needs to be studied for accessing the retrieval of geophysical parameters such as <span class="hlt">ice</span> thickness. Frost flowers or snow layer is modeled with a heterogeneous mixture consisting of randomly oriented ellipsoids and brine infiltration in an air background. <span class="hlt">Ice</span> crystals are characterized with three different axial lengths to depict the nonspherical shape. Under the <span class="hlt">covering</span> multispecies medium, the columinar sea-<span class="hlt">ice</span> layer is an inhomogeneous anisotropic medium composed of ellipsoidal brine inclusions preferentially oriented in the vertical direction in an <span class="hlt">ice</span> background. The underlying medium is homogeneous sea water. This configuration is described with layered inhomogeneous media containing multiple species of scatterers. The species are allowed to have different size, shape, and permittivity. The strong permittivity fluctuation theory is extended to account for the multispecies in the derivation of effective permittivities with distributions of scatterer orientations characterized by Eulerian rotation angles. Polarimetric backscattering coefficients are obtained consistently with the same physical description used in the effective permittivity calculation. The mulitspecies model allows the inclusion of high-permittivity species to study effects of brine infiltrated snow <span class="hlt">cover</span> and frost flowers on thin <span class="hlt">ice</span>. The results suggest that the frost <span class="hlt">cover</span> with a rough interface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..228...54F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..228...54F"><span>Formation of lobate debris aprons on Mars: Assessment of regional <span class="hlt">ice</span> sheet collapse and debris-<span class="hlt">cover</span> armoring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fastook, James L.; Head, James W.; Marchant, David R.</p> <p>2014-01-01</p> <p>Lobate debris aprons (LDA) are lobate-shaped aprons surrounding scarps and isolated massifs that are concentrated in the vicinity of the northern Dichotomy Boundary on Mars. LDAs have been interpreted as (1) <span class="hlt">ice</span>-cemented talus aprons undergoing viscous flow, (2) local debris-<span class="hlt">covered</span> alpine-like glaciers, or (3) remnants of the collapse of a regional retreating <span class="hlt">ice</span> sheet. We investigate the plausibility that LDAs are remnants of a more extensive regional <span class="hlt">ice</span> sheet by modeling this process. We find that as a regional <span class="hlt">ice</span> sheet collapses, the surface drops below cliff and massif bedrock margins, exposing bedrock and regolith, and initiating debris deposition on the surface of a cold-<span class="hlt">based</span> glacier. Reduced sublimation due to debris-<span class="hlt">cover</span> armoring of the proto-LDA surface produces a surface slope and consequent <span class="hlt">ice</span> flow that carries the armoring debris away from the rock outcrops. As collapse and <span class="hlt">ice</span> retreat continue the debris train eventually reaches the substrate surface at the front of the glacier, leaving the entire LDA armored by debris <span class="hlt">cover</span>. Using a simplified <span class="hlt">ice</span> flow model we are able to characterize the temperature and sublimation rate that would be necessary to produce LDAs with a wide range of specified lateral extents and thicknesses. We then apply this method to a database of documented LDA parameters (height, lateral extent) from the Dichotomy Boundary region, and assess the implications for predicted climate conditions during their formation and the range of formation times implied by the model. We find that for the population examined here, typical temperatures are in the range of -85 to -40 °C and typical sublimation rates lie in the range of 6-14 mm/a. Lobate debris apron formation times (from the point of bedrock exposure to complete debris <span class="hlt">cover</span>) cluster near 400-500 ka. These results show that LDA length and thickness characteristics are consistent with climate conditions and a formation scenario typical of the collapse of a regional retreating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171595','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171595"><span>Impact Studies of a 2 C Global Warming on the Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.</p> <p>2004-01-01</p> <p>The possible impact of an increase in global temperatures of about 2 C, as may be caused by a doubling of atmospheric CO2, is studied using historical satellite records of surface temperatures and sea <span class="hlt">ice</span> from late 1970s to 2003. Updated satellite data indicate that the perennial <span class="hlt">ice</span> continued to decline at an even faster rate of 9.2 % per decade than previously reported while concurrently, the surface temperatures have steadily been going up in most places except for some parts of northern Russia. Surface temperature is shown to be highly correlated with sea <span class="hlt">ice</span> concentration in the seasonal sea <span class="hlt">ice</span> regions. Results of regression analysis indicates that for every 1 C increase in temperature, the perennial <span class="hlt">ice</span> area decreases by about 1.48 x 10(exp 6) square kilometers with the correlation coefficient being significant but only -0.57. Arctic warming is estimated to be about 0.46 C per decade on average in the Arctic but is shown to be off center with respect to the North Pole, and is prominent mainly in the Western Arctic and North America. The length of melt has been increasing by 13 days per decade over sea <span class="hlt">ice</span> <span class="hlt">covered</span> areas suggesting a thinning in the <span class="hlt">ice</span> <span class="hlt">cover</span>. The length of melt also increased by 5 days per decade over Greenland, 7 days per decade over the permafrost areas of North America but practically no change in Eurasia. Statistically derived projections indicate that the perennial sea <span class="hlt">ice</span> <span class="hlt">cover</span> would decline considerably in 2025, 2035, and 2060 when temperatures are predicted by models to reach the 2 C global increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930032582&hterms=Storm+Japan&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DStorm%2BJapan','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930032582&hterms=Storm+Japan&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DStorm%2BJapan"><span>The effect of severe storms on the <span class="hlt">ice</span> <span class="hlt">cover</span> of the northern Tatarskiy Strait</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin, Seelye; Munoz, Esther; Drucker, Robert</p> <p>1992-01-01</p> <p>Passive microwave images from the Special Sensor Microwave Imager are used to study the volume of <span class="hlt">ice</span> and sea-bottom water in the Japan Sea as affected by winds and severe storms. The data set comprises brightness temperatures gridded on a polar stereographic projection, and the processing is accomplished with a linear algorithm by Cavalieri et al. (1983) <span class="hlt">based</span> on the vertically polarized 37-GHz channel. The expressions for calculating heat fluxes and downwelling radiation are given, and <span class="hlt">ice-cover</span> fluctuations are correlated with severe storm events. The storms generate large transient polynya that occur simultaneously with the strongest heat fluxes, and severe storms are found to contribute about 25 percent of the annual introduction of 25 cu km of <span class="hlt">ice</span> in the region. The <span class="hlt">ice</span> production could lead to the renewal of enough sea-bottom water to account for the C-14 data provided, and the generation of Japan Sea bottom water is found to vary directly with storm activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.......50T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.......50T"><span>Quantitative calibration of remote mountain lake sediments as climatic recorders of <span class="hlt">ice-cover</span> duration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, R.; Price, D.</p> <p>2003-04-01</p> <p>Using a thermal degree modelling approach <span class="hlt">ice</span> <span class="hlt">cover</span> duration on European mountain lakes is found to be very sensitive to temperature change. For example our thermal degree model (which incorporates a weather generator) predicts a 100 day shortening in <span class="hlt">ice-cover</span> duration for a 3 degree Centigrade temperature rise for north facing catchments at elevations of 1200m in the southern Alps, and 1500m in the Pyrenees. 30% higher sensitivities (130d/3oC) are found for the more maritime lakes of Scotland, while lakes in NW Finland, in a more continental setting, have only half the sensitivity (50d/3oC). A pan European data set of the species abundance of 252 diatom taxa in 462 mountain and sub Arctic lakes has been compiled. Taxonomic harmonisation is <span class="hlt">based</span> on a team effort carried out as an integral part of the AL:PE, CHILL and EMERGE projects. Transfer functions have been created relating <span class="hlt">ice-cover</span> duration to diatom species composition <span class="hlt">based</span> on a weighted averaging - partial least squares (WA-PLS) approach. Cross validation was used to test the transfer functions. The pan European data set yields an R-squared of 0.73, an R-squared(jack) of 0.58, and an RMSEP error of 23 days. A regional, northern Scandinavian transect, (151 lakes, 122 taxa) yields an R-squared(jack) of 0.50, and an RMSEP of 9 days. The pan European database displays greatest skill when reconstructing winter or spring temperatures. This contrasts with the summer temperatures normally studied when using local elevation gradients. The northern Scandinavian transect has a remarkably low winter RMSEP of 0.73 oC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160012483','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160012483"><span>Modeling the Thickness of Perennial <span class="hlt">Ice</span> <span class="hlt">Covers</span> on Stratified Lakes of the Taylor Valley, Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Obryk, M. K.; Doran, P. T.; Hicks, J. A.; McKay, C. P.; Priscu, J. C.</p> <p>2016-01-01</p> <p>A one-dimensional <span class="hlt">ice</span> <span class="hlt">cover</span> model was developed to predict and constrain drivers of long term <span class="hlt">ice</span> thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 years (between 1996 and 2012) of <span class="hlt">ice</span> thickness changes for west lobe of Lake Bonney (average <span class="hlt">ice</span> thickness = 3.53 m; RMSE = 0.09 m, n = 118) and Lake Fryxell (average <span class="hlt">ice</span> thickness = 4.22 m; RMSE = 0.21 m, n = 128). Long-term <span class="hlt">ice</span> thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate <span class="hlt">ice</span> thickness change depending on the predominant climatic trend (temperature cooling or warming). As such, shallow (< 20 m deep water columns) perennially <span class="hlt">ice-covered</span> lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term <span class="hlt">ice</span> thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11A0352L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11A0352L"><span>Radon and radium in the <span class="hlt">ice-covered</span> Arctic Ocean, and what they reveal about gas exchange in the sea <span class="hlt">ice</span> zone.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loose, B.; Kelly, R. P.; Bigdeli, A.; Moran, S. B.</p> <p>2014-12-01</p> <p>The polar sea <span class="hlt">ice</span> zones are regions of high primary productivity and interior water mass formation. Consequently, the seasonal sea <span class="hlt">ice</span> cycle appears important to both the solubility and biological carbon pumps. To estimate net CO2 transfer in the sea <span class="hlt">ice</span> zone, we require accurate estimates of the air-sea gas transfer velocity. In the open ocean, the gas transfer velocity is driven by wind, waves and bubbles - all of which are strongly altered by the presence of sea <span class="hlt">ice</span>, making it difficult to translate open ocean estimates of gas transfer to the <span class="hlt">ice</span> zone. In this study, we present profiles of 222Rn and 226Ra throughout the mixed-layer and euphotic zone. Profiles were collected spanning a range of sea <span class="hlt">ice</span> <span class="hlt">cover</span> conditions from 40 to 100%. The profiles of Rn/Ra can be used to estimate the gas transfer velocity, but the 3.8 day half-life of 222Rn implies that mixed layer radon will have a memory of the past ~20 days of gas exchange forcing, which may include a range of sea <span class="hlt">ice</span> <span class="hlt">cover</span> conditions. Here, we compare individual estimates of the gas transfer velocity to the turbulent forcing conditions constrained from shipboard and regional reanalysis data to more appropriately capture the time history upper ocean Rn/Ra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25712272','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25712272"><span><span class="hlt">Ice</span> <span class="hlt">cover</span> extent drives phytoplankton and bacterial community structure in a large north-temperate lake: implications for a warming climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beall, B F N; Twiss, M R; Smith, D E; Oyserman, B O; Rozmarynowycz, M J; Binding, C E; Bourbonniere, R A; Bullerjahn, G S; Palmer, M E; Reavie, E D; Waters, Lcdr M K; Woityra, Lcdr W C; McKay, R M L</p> <p>2016-06-01</p> <p>Mid-winter limnological surveys of Lake Erie captured extremes in <span class="hlt">ice</span> extent ranging from expansive <span class="hlt">ice</span> <span class="hlt">cover</span> in 2010 and 2011 to nearly <span class="hlt">ice</span>-free waters in 2012. Consistent with a warming climate, <span class="hlt">ice</span> <span class="hlt">cover</span> on the Great Lakes is in decline, thus the <span class="hlt">ice</span>-free condition encountered may foreshadow the lakes future winter state. Here, we show that pronounced changes in annual <span class="hlt">ice</span> <span class="hlt">cover</span> are accompanied by equally important shifts in phytoplankton and bacterial community structure. Expansive <span class="hlt">ice</span> <span class="hlt">cover</span> supported phytoplankton blooms of filamentous diatoms. By comparison, <span class="hlt">ice</span> free conditions promoted the growth of smaller sized cells that attained lower total biomass. We propose that isothermal mixing and elevated turbidity in the absence of <span class="hlt">ice</span> <span class="hlt">cover</span> resulted in light limitation of the phytoplankton during winter. Additional insights into microbial community dynamics were gleaned from short 16S rRNA tag (Itag) Illumina sequencing. UniFrac analysis of Itag sequences showed clear separation of microbial communities related to presence or absence of <span class="hlt">ice</span> <span class="hlt">cover</span>. Whereas the ecological implications of the changing bacterial community are unclear at this time, it is likely that the observed shift from a phytoplankton community dominated by filamentous diatoms to smaller cells will have far reaching ecosystem effects including food web disruptions. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JHyd..521...46K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JHyd..521...46K"><span>Separating snow, clean and debris <span class="hlt">covered</span> <span class="hlt">ice</span> in the Upper Indus Basin, Hindukush-Karakoram-Himalayas, using Landsat images between 1998 and 2002</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, Asif; Naz, Bibi S.; Bowling, Laura C.</p> <p>2015-02-01</p> <p>The Hindukush Karakoram Himalayan mountains contain some of the largest glaciers of the world, and supply melt water from perennial snow and glaciers to the Upper Indus Basin (UIB) upstream of Tarbela dam, which constitutes greater than 80% of the annual flows, and caters to the needs of millions of people in the Indus Basin. It is therefore important to study the response of perennial snow and glaciers in the UIB under changing climatic conditions, using improved hydrological modeling, glacier mass balance, and observations of glacier responses. However, the available glacier inventories and datasets only provide total perennial-snow and glacier <span class="hlt">cover</span> areas, despite the fact that snow, clean <span class="hlt">ice</span> and debris <span class="hlt">covered</span> <span class="hlt">ice</span> have different melt rates and densities. This distinction is vital for improved hydrological modeling and mass balance studies. This study, therefore, presents a separated perennial snow and glacier inventory (perennial snow-<span class="hlt">cover</span> on steep slopes, perennial snow-<span class="hlt">covered</span> <span class="hlt">ice</span>, clean and debris <span class="hlt">covered</span> <span class="hlt">ice</span>) <span class="hlt">based</span> on a semi-automated method that combines Landsat images and surface slope information in a supervised maximum likelihood classification to map distinct glacier zones, followed by manual post processing. The accuracy of the presented inventory falls well within the accuracy limits of available snow and glacier inventory products. For the entire UIB, estimates of perennial and/or seasonal snow on steep slopes, snow-<span class="hlt">covered</span> <span class="hlt">ice</span>, clean and debris <span class="hlt">covered</span> <span class="hlt">ice</span> zones are 7238 ± 724, 5226 ± 522, 4695 ± 469 and 2126 ± 212 km2 respectively. Thus total snow and glacier <span class="hlt">cover</span> is 19,285 ± 1928 km2, out of which 12,075 ± 1207 km2 is glacier <span class="hlt">cover</span> (excluding steep slope snow-<span class="hlt">cover</span>). Equilibrium Line Altitude (ELA) estimates <span class="hlt">based</span> on the Snow Line Elevation (SLE) in various watersheds range between 4800 and 5500 m, while the Accumulation Area Ratio (AAR) ranges between 7% and 80%. 0 °C isotherms during peak ablation months (July and August) range</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601317','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601317"><span>Atmospheric Profiles, Clouds, and the Evolution of Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Beaufort and Chukchi Seas Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p><span class="hlt">Cover</span> in the Beaufort and Chukchi Seas Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys Axel...how changes in sea <span class="hlt">ice</span> and sea surface conditions in the SIZ affect changes in cloud properties and <span class="hlt">cover</span> . • Determine the role additional atmospheric...REPORT TYPE 3. DATES <span class="hlt">COVERED</span> 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Atmospheric Profiles, Clouds, and the Evolution of Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5351862','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5351862"><span><span class="hlt">Ice-cover</span> is the principal driver of ecological change in High Arctic lakes and ponds</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Griffiths, Katherine; Michelutti, Neal; Sugar, Madeline; Douglas, Marianne S. V.; Smol, John P.</p> <p>2017-01-01</p> <p>Recent climate change has been especially pronounced in the High Arctic, however, the responses of aquatic biota, such as diatoms, can be modified by site-specific environmental characteristics. To assess if climate-mediated <span class="hlt">ice</span> <span class="hlt">cover</span> changes affect the diatom response to climate, we used paleolimnological techniques to examine shifts in diatom assemblages from ten High Arctic lakes and ponds from Ellesmere Island and nearby Pim Island (Nunavut, Canada). The sites were divided a priori into four groups (“warm”, “cool”, “cold”, and “oasis”) <span class="hlt">based</span> on local elevation and microclimatic differences that result in differing lengths of the <span class="hlt">ice</span>-free season, as well as about three decades of personal observations. We characterized the species changes as a shift from Condition 1 (i.e. a generally low diversity, predominantly epipelic and epilithic diatom assemblage) to Condition 2 (i.e. a typically more diverse and ecologically complex assemblage with an increasing proportion of epiphytic species). This shift from Condition 1 to Condition 2 was a consistent pattern recorded across the sites that experienced a change in <span class="hlt">ice</span> <span class="hlt">cover</span> with warming. The “warm” sites are amongst the first to lose their <span class="hlt">ice</span> <span class="hlt">covers</span> in summer and recorded the earliest and highest magnitude changes. The “cool” sites also exhibited a shift from Condition 1 to Condition 2, but, as predicted, the timing of the response lagged the “warm” sites. Meanwhile some of the “cold” sites, which until recently still retained an <span class="hlt">ice</span> raft in summer, only exhibited this shift in the upper-most sediments. The warmer “oasis” ponds likely supported aquatic vegetation throughout their records. Consequently, the diatoms of the “oasis” sites were characterized as high-diversity, Condition 2 assemblages throughout the record. Our results support the hypothesis that the length of the <span class="hlt">ice</span>-free season is the principal driver of diatom assemblage responses to climate in the High Arctic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28296897','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28296897"><span><span class="hlt">Ice-cover</span> is the principal driver of ecological change in High Arctic lakes and ponds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Griffiths, Katherine; Michelutti, Neal; Sugar, Madeline; Douglas, Marianne S V; Smol, John P</p> <p>2017-01-01</p> <p>Recent climate change has been especially pronounced in the High Arctic, however, the responses of aquatic biota, such as diatoms, can be modified by site-specific environmental characteristics. To assess if climate-mediated <span class="hlt">ice</span> <span class="hlt">cover</span> changes affect the diatom response to climate, we used paleolimnological techniques to examine shifts in diatom assemblages from ten High Arctic lakes and ponds from Ellesmere Island and nearby Pim Island (Nunavut, Canada). The sites were divided a priori into four groups ("warm", "cool", "cold", and "oasis") <span class="hlt">based</span> on local elevation and microclimatic differences that result in differing lengths of the <span class="hlt">ice</span>-free season, as well as about three decades of personal observations. We characterized the species changes as a shift from Condition 1 (i.e. a generally low diversity, predominantly epipelic and epilithic diatom assemblage) to Condition 2 (i.e. a typically more diverse and ecologically complex assemblage with an increasing proportion of epiphytic species). This shift from Condition 1 to Condition 2 was a consistent pattern recorded across the sites that experienced a change in <span class="hlt">ice</span> <span class="hlt">cover</span> with warming. The "warm" sites are amongst the first to lose their <span class="hlt">ice</span> <span class="hlt">covers</span> in summer and recorded the earliest and highest magnitude changes. The "cool" sites also exhibited a shift from Condition 1 to Condition 2, but, as predicted, the timing of the response lagged the "warm" sites. Meanwhile some of the "cold" sites, which until recently still retained an <span class="hlt">ice</span> raft in summer, only exhibited this shift in the upper-most sediments. The warmer "oasis" ponds likely supported aquatic vegetation throughout their records. Consequently, the diatoms of the "oasis" sites were characterized as high-diversity, Condition 2 assemblages throughout the record. Our results support the hypothesis that the length of the <span class="hlt">ice</span>-free season is the principal driver of diatom assemblage responses to climate in the High Arctic, largely driven by the establishment of new</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPRS..117..126S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPRS..117..126S"><span>Automated mapping of persistent <span class="hlt">ice</span> and snow <span class="hlt">cover</span> across the western U.S. with Landsat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Selkowitz, David J.; Forster, Richard R.</p> <p>2016-07-01</p> <p>We implemented an automated approach for mapping persistent <span class="hlt">ice</span> and snow <span class="hlt">cover</span> (PISC) across the conterminous western U.S. using all available Landsat TM and ETM+ scenes acquired during the late summer/early fall period between 2010 and 2014. Two separate validation approaches indicate this dataset provides a more accurate representation of glacial <span class="hlt">ice</span> and perennial snow <span class="hlt">cover</span> for the region than either the U.S. glacier database derived from US Geological Survey (USGS) Digital Raster Graphics (DRG) maps (<span class="hlt">based</span> on aerial photography primarily from the 1960s-1980s) or the National Land <span class="hlt">Cover</span> Database 2011 perennial <span class="hlt">ice</span> and snow <span class="hlt">cover</span> class. Our 2010-2014 Landsat-derived dataset indicates 28% less glacier and perennial snow <span class="hlt">cover</span> than the USGS DRG dataset. There are larger differences between the datasets in some regions, such as the Rocky Mountains of Northwest Wyoming and Southwest Montana, where the Landsat dataset indicates 54% less PISC area. Analysis of Landsat scenes from 1987-1988 and 2008-2010 for three regions using a more conventional, semi-automated approach indicates substantial decreases in glaciers and perennial snow <span class="hlt">cover</span> that correlate with differences between PISC mapped by the USGS DRG dataset and the automated Landsat-derived dataset. This suggests that most of the differences in PISC between the USGS DRG and the Landsat-derived dataset can be attributed to decreases in PISC, as opposed to differences between mapping techniques. While the dataset produced by the automated Landsat mapping approach is not designed to serve as a conventional glacier inventory that provides glacier outlines and attribute information, it allows for an updated estimate of PISC for the conterminous U.S. as well as for smaller regions. Additionally, the new dataset highlights areas where decreases in PISC have been most significant over the past 25-50 years.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70182762','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70182762"><span>Automated mapping of persistent <span class="hlt">ice</span> and snow <span class="hlt">cover</span> across the western U.S. with Landsat</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Selkowitz, David J.; Forster, Richard R.</p> <p>2016-01-01</p> <p>We implemented an automated approach for mapping persistent <span class="hlt">ice</span> and snow <span class="hlt">cover</span> (PISC) across the conterminous western U.S. using all available Landsat TM and ETM+ scenes acquired during the late summer/early fall period between 2010 and 2014. Two separate validation approaches indicate this dataset provides a more accurate representation of glacial <span class="hlt">ice</span> and perennial snow <span class="hlt">cover</span> for the region than either the U.S. glacier database derived from US Geological Survey (USGS) Digital Raster Graphics (DRG) maps (<span class="hlt">based</span> on aerial photography primarily from the 1960s–1980s) or the National Land <span class="hlt">Cover</span> Database 2011 perennial <span class="hlt">ice</span> and snow <span class="hlt">cover</span> class. Our 2010–2014 Landsat-derived dataset indicates 28% less glacier and perennial snow <span class="hlt">cover</span> than the USGS DRG dataset. There are larger differences between the datasets in some regions, such as the Rocky Mountains of Northwest Wyoming and Southwest Montana, where the Landsat dataset indicates 54% less PISC area. Analysis of Landsat scenes from 1987–1988 and 2008–2010 for three regions using a more conventional, semi-automated approach indicates substantial decreases in glaciers and perennial snow <span class="hlt">cover</span> that correlate with differences between PISC mapped by the USGS DRG dataset and the automated Landsat-derived dataset. This suggests that most of the differences in PISC between the USGS DRG and the Landsat-derived dataset can be attributed to decreases in PISC, as opposed to differences between mapping techniques. While the dataset produced by the automated Landsat mapping approach is not designed to serve as a conventional glacier inventory that provides glacier outlines and attribute information, it allows for an updated estimate of PISC for the conterminous U.S. as well as for smaller regions. Additionally, the new dataset highlights areas where decreases in PISC have been most significant over the past 25–50 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JHyDy..30..336W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JHyDy..30..336W"><span>Revisit submergence of <span class="hlt">ice</span> blocks in front of <span class="hlt">ice</span> cover—an experimental study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Jun; Wu, Yi-fan; Sui, Jueyi</p> <p>2018-04-01</p> <p>The present paper studies the stabilities of <span class="hlt">ice</span> blocks in front of an <span class="hlt">ice</span> <span class="hlt">cover</span> <span class="hlt">based</span> on experiments carried out in laboratory by using four types of <span class="hlt">ice</span> blocks with different dimensions. The forces acting on the <span class="hlt">ice</span> blocks in front of the <span class="hlt">ice</span> <span class="hlt">cover</span> are analyzed. The critical criteria for the entrainment of <span class="hlt">ice</span> blocks in front of the <span class="hlt">ice</span> <span class="hlt">cover</span> are established by considering the drag force caused by the flowing water, the collision force, and the hydraulic pressure force. Formula for determining whether or not an <span class="hlt">ice</span> block will be entrained under the <span class="hlt">ice</span> <span class="hlt">cover</span> is derived. All three dimensions of the <span class="hlt">ice</span> block are considered in the proposed formula. The velocities calculated by using the developed formula are compared with those of calculated by other formulas proposed by other researchers, as well as the measured flow velocities for the entrainment of <span class="hlt">ice</span> blocks in laboratory. The fitting values obtained by using the derived formula agree well with the experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..433P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..433P"><span>The Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> of 2016: a year of record-low highs and higher-than-expected lows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petty, Alek A.; Stroeve, Julienne C.; Holland, Paul R.; Boisvert, Linette N.; Bliss, Angela C.; Kimura, Noriaki; Meier, Walter N.</p> <p>2018-02-01</p> <p>The Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> of 2016 was highly noteworthy, as it featured record low monthly sea <span class="hlt">ice</span> extents at the start of the year but a summer (September) extent that was higher than expected by most seasonal forecasts. Here we explore the 2016 Arctic sea <span class="hlt">ice</span> state in terms of its monthly sea <span class="hlt">ice</span> <span class="hlt">cover</span>, placing this in the context of the sea <span class="hlt">ice</span> conditions observed since 2000. We demonstrate the sensitivity of monthly Arctic sea <span class="hlt">ice</span> extent and area estimates, in terms of their magnitude and annual rankings, to the <span class="hlt">ice</span> concentration input data (using two widely used datasets) and to the averaging methodology used to convert concentration to extent (daily or monthly extent calculations). We use estimates of sea <span class="hlt">ice</span> area over sea <span class="hlt">ice</span> extent to analyse the relative "compactness" of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, highlighting anomalously low compactness in the summer of 2016 which contributed to the higher-than-expected September <span class="hlt">ice</span> extent. Two cyclones that entered the Arctic Ocean during August appear to have driven this low-concentration/compactness <span class="hlt">ice</span> <span class="hlt">cover</span> but were not sufficient to cause more widespread melt-out and a new record-low September <span class="hlt">ice</span> extent. We use concentration budgets to explore the regions and processes (thermodynamics/dynamics) contributing to the monthly 2016 extent/area estimates highlighting, amongst other things, rapid <span class="hlt">ice</span> intensification across the central eastern Arctic through September. Two different products show significant early melt onset across the Arctic Ocean in 2016, including record-early melt onset in the North Atlantic sector of the Arctic. Our results also show record-late 2016 freeze-up in the central Arctic, North Atlantic and the Alaskan Arctic sector in particular, associated with strong sea surface temperature anomalies that appeared shortly after the 2016 minimum (October onwards). We explore the implications of this low summer <span class="hlt">ice</span> compactness for seasonal forecasting, suggesting that sea <span class="hlt">ice</span> area could be a more reliable</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26064653','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26064653"><span>Extreme ecological response of a seabird community to unprecedented sea <span class="hlt">ice</span> <span class="hlt">cover</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barbraud, Christophe; Delord, Karine; Weimerskirch, Henri</p> <p>2015-05-01</p> <p>Climate change has been predicted to reduce Antarctic sea <span class="hlt">ice</span> but, instead, sea <span class="hlt">ice</span> surrounding Antarctica has expanded over the past 30 years, albeit with contrasted regional changes. Here we report a recent extreme event in sea <span class="hlt">ice</span> conditions in East Antarctica and investigate its consequences on a seabird community. In early 2014, the Dumont d'Urville Sea experienced the highest magnitude sea <span class="hlt">ice</span> <span class="hlt">cover</span> (76.8%) event on record (1982-2013: range 11.3-65.3%; mean±95% confidence interval: 27.7% (23.1-32.2%)). Catastrophic effects were detected in the breeding output of all sympatric seabird species, with a total failure for two species. These results provide a new view crucial to predictive models of species abundance and distribution as to how extreme sea <span class="hlt">ice</span> events might impact an entire community of top predators in polar marine ecosystems in a context of expanding sea <span class="hlt">ice</span> in eastern Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070034825','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070034825"><span>Trends in the Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> Using Enhanced and Compatible AMSR-E, SSM/I and SMMR Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Nishio, Fumihiko</p> <p>2007-01-01</p> <p>Arguably, the most remarkable manifestation of change in the polar regions is the rapid decline (of about -10 %/decade) in the Arctic perennial <span class="hlt">ice</span> <span class="hlt">cover</span>. Changes in the global sea <span class="hlt">ice</span> <span class="hlt">cover</span>, however, are more modest, being slightly positive in the Southern Hemisphere and slightly negative in the Northern Hemisphere, the significance of which has not been adequately assessed because of unknown errors in the satellite historical data. We take advantage of the recent and more accurate AMSR-E data to evaluate the true seasonal and interannual variability of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, assess the accuracy of historical data, and determine the real trend. Consistently derived <span class="hlt">ice</span> concentrations from AMSR-E, SSM/I, and SMMR data were analyzed and a slight bias is observed between AMSR-E and SSM/I data mainly because of differences in resolution. Analysis of the combine SMMR, SSM/I and AMSR-E data set, with the bias corrected, shows that the trends in extent and area of sea <span class="hlt">ice</span> in the Arctic region is -3.4 +/- 0.2 and -4.0 +/- 0.2 % per decade, respectively, while the corresponding values for the Antarctic region is 0.9 +/- 0.2 and 1.7 .+/- 0.3 % per decade. The higher resolution of the AMSR-E provides an improved determination of the location of the <span class="hlt">ice</span> edge while the SSM/I data show an <span class="hlt">ice</span> edge about 6 to 12 km further away from the <span class="hlt">ice</span> pack. Although the current record of AMSR-E is less than 5 years, the data can be utilized in combination with historical data for more accurate determination of the variability and trends in the <span class="hlt">ice</span> <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50..423C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50..423C"><span>An interannual link between Arctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and the North Atlantic Oscillation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caian, Mihaela; Koenigk, Torben; Döscher, Ralf; Devasthale, Abhay</p> <p>2018-01-01</p> <p>This work investigates links between Arctic surface variability and the phases of the winter (DJF) North Atlantic Oscillation (NAO) on interannual time-scales. The analysis is <span class="hlt">based</span> on ERA-reanalysis and model data from the EC-Earth global climate model. Our study emphasizes a mode of sea-<span class="hlt">ice</span> <span class="hlt">cover</span> variability that leads the NAO index by 1 year. The mechanism of this leading is <span class="hlt">based</span> on persistent surface forcing by quasi-stationary meridional thermal gradients. Associated thermal winds lead a slow adjustment of the pressure in the following winter, which in turn feeds-back on the propagation of sea-<span class="hlt">ice</span> anomalies. The pattern of the sea-<span class="hlt">ice</span> mode leading NAO has positive anomalies over key areas of South-Davis Strait-Labrador Sea, the Barents Sea and the Laptev-Ohkostsk seas, associated to a high pressure anomaly over the Canadian Archipelago-Baffin Bay and the Laptev-East-Siberian seas. These anomalies create a quasi-annular, quasi-steady, positive gradient of sea-<span class="hlt">ice</span> anomalies about coastal line (when leading the positive NAO phase) and force a cyclonic vorticity anomaly over the Arctic in the following winter. During recent decades in spite of slight shifts in the modes' spectral properties, the same leading mechanism remains valid. Encouraging, actual models appear to reproduce the same mechanism leading model's NAO, relative to model areas of persistent surface forcing. This indicates that the link between sea-<span class="hlt">ice</span> and NAO could be exploited as a potential skill-source for multi-year prediction by addressing the key problem of initializing the phase of the NAO/AO (Arctic Oscillation).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70168450','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70168450"><span>Evidence for an <span class="hlt">ice</span> shelf <span class="hlt">covering</span> the central Arctic Ocean during the penultimate glaciation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jakobsson, Martin; Nilsson, Johan; Anderson, Leif G.; Backman, Jan; Bjork, Goran; Cronin, Thomas M.; Kirchner, Nina; Koshurnikov, Andrey; Mayer, Larry; Noormets, Riko; O'Regan, Matthew; Stranne, Christian; Ananiev, Roman; Macho, Natalia Barrientos; Cherniykh, Dennis; Coxall, Helen; Eriksson, Bjorn; Floden, Tom; Gemery, Laura; Gustafsson, Orjan; Jerram, Kevin; Johansson, Carina; Khortov, Alexey; Mohammad, Rezwan; Semiletov, Igor</p> <p>2016-01-01</p> <p>The hypothesis of a km-thick <span class="hlt">ice</span> shelf <span class="hlt">covering</span> the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating <span class="hlt">ice</span> shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of <span class="hlt">ice</span> shelves should, however, exist where <span class="hlt">ice</span> grounded along their flow paths. Here we present new evidence of <span class="hlt">ice</span>-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an <span class="hlt">ice</span> shelf extending over the entire central Arctic Ocean during at least one previous <span class="hlt">ice</span> age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean <span class="hlt">ice</span> shelf dated to marine isotope stage 6 (~140 ka). Bathymetric highs were likely critical in the <span class="hlt">ice</span>-shelf development by acting as pinning points where stabilizing <span class="hlt">ice</span> rises formed, thereby providing sufficient back stress to allow <span class="hlt">ice</span> shelf thickening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4735638','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4735638"><span>Evidence for an <span class="hlt">ice</span> shelf <span class="hlt">covering</span> the central Arctic Ocean during the penultimate glaciation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jakobsson, Martin; Nilsson, Johan; Anderson, Leif; Backman, Jan; Björk, Göran; Cronin, Thomas M.; Kirchner, Nina; Koshurnikov, Andrey; Mayer, Larry; Noormets, Riko; O'Regan, Matthew; Stranne, Christian; Ananiev, Roman; Barrientos Macho, Natalia; Cherniykh, Denis; Coxall, Helen; Eriksson, Björn; Flodén, Tom; Gemery, Laura; Gustafsson, Örjan; Jerram, Kevin; Johansson, Carina; Khortov, Alexey; Mohammad, Rezwan; Semiletov, Igor</p> <p>2016-01-01</p> <p>The hypothesis of a km-thick <span class="hlt">ice</span> shelf <span class="hlt">covering</span> the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating <span class="hlt">ice</span> shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of <span class="hlt">ice</span> shelves should, however, exist where <span class="hlt">ice</span> grounded along their flow paths. Here we present new evidence of <span class="hlt">ice</span>-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an <span class="hlt">ice</span> shelf extending over the entire central Arctic Ocean during at least one previous <span class="hlt">ice</span> age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean <span class="hlt">ice</span> shelf dated to marine isotope stage 6 (∼140 ka). Bathymetric highs were likely critical in the <span class="hlt">ice</span>-shelf development by acting as pinning points where stabilizing <span class="hlt">ice</span> rises formed, thereby providing sufficient back stress to allow <span class="hlt">ice</span> shelf thickening. PMID:26778247</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28276129','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28276129"><span>Niche specialization of bacteria in permanently <span class="hlt">ice-covered</span> lakes of the McMurdo Dry Valleys, Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kwon, Miye; Kim, Mincheol; Takacs-Vesbach, Cristina; Lee, Jaejin; Hong, Soon Gyu; Kim, Sang Jong; Priscu, John C; Kim, Ok-Sun</p> <p>2017-06-01</p> <p>Perennially <span class="hlt">ice-covered</span> lakes in the McMurdo Dry Valleys, Antarctica, are chemically stratified with depth and have distinct biological gradients. Despite long-term research on these unique environments, data on the structure of the microbial communities in the water columns of these lakes are scarce. Here, we examined bacterial diversity in five <span class="hlt">ice-covered</span> Antarctic lakes by 16S rRNA gene-<span class="hlt">based</span> pyrosequencing. Distinct communities were present in each lake, reflecting the unique biogeochemical characteristics of these environments. Further, certain bacterial lineages were confined exclusively to specific depths within each lake. For example, candidate division WM88 occurred solely at a depth of 15 m in Lake Fryxell, whereas unknown lineages of Chlorobi were found only at a depth of 18 m in Lake Miers, and two distinct classes of Firmicutes inhabited East and West Lobe Bonney at depths of 30 m. Redundancy analysis revealed that community variation of bacterioplankton could be explained by the distinct conditions of each lake and depth; in particular, assemblages from layers beneath the chemocline had biogeochemical associations that differed from those in the upper layers. These patterns of community composition may represent bacterial adaptations to the extreme and unique biogeochemical gradients of <span class="hlt">ice-covered</span> lakes in the McMurdo Dry Valleys. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.9548T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.9548T"><span>Biogeochemical Impact of Snow <span class="hlt">Cover</span> and Cyclonic Intrusions on the Winter Weddell Sea <span class="hlt">Ice</span> Pack</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tison, J.-L.; Schwegmann, S.; Dieckmann, G.; Rintala, J.-M.; Meyer, H.; Moreau, S.; Vancoppenolle, M.; Nomura, D.; Engberg, S.; Blomster, L. J.; Hendrickx, S.; Uhlig, C.; Luhtanen, A.-M.; de Jong, J.; Janssens, J.; Carnat, G.; Zhou, J.; Delille, B.</p> <p>2017-12-01</p> <p>Sea <span class="hlt">ice</span> is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack <span class="hlt">ice</span> in the Weddell Sea (R. V. Polarstern AWECS cruise, June-August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea <span class="hlt">ice</span> <span class="hlt">cover</span> due to the combined effects of deep snow and frequent warm cyclones events penetrating southward from the open Southern Ocean. These conditions were favorable to high <span class="hlt">ice</span> permeability and cyclic events of brine movements within the sea <span class="hlt">ice</span> <span class="hlt">cover</span> (brine tubes), favoring relatively high chlorophyll-a (Chl-a) concentrations. We discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions. Large-scale sea <span class="hlt">ice</span> model simulations also suggest a context of increasingly deep snow, warm <span class="hlt">ice</span>, and large brine fractions across the three observational years, despite the fact that the model is forced with a snowfall climatology. This lends support to the claim that more severe Antarctic sea <span class="hlt">ice</span> conditions, characterized by a longer <span class="hlt">ice</span> season, thicker, and more concentrated <span class="hlt">ice</span> are sufficient to increase the snow depth and, somehow counterintuitively, to warm the <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.U13C0068D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.U13C0068D"><span>Reemergence of sea <span class="hlt">ice</span> <span class="hlt">cover</span> anomalies and the role of the sea <span class="hlt">ice</span>-albedo feedback in CCSM simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deweaver, E. T.</p> <p>2008-12-01</p> <p>The dramatic sea <span class="hlt">ice</span> decline of 2007 and lack of recovery in 2008 raise the question of a "tipping point" for Arctic sea <span class="hlt">ice</span>, beyond which the transition to a seasonal sea <span class="hlt">ice</span> state becomes abrupt and irreversible. The tipping point is essentially a "memory catastrophe", in which a dramatic loss of sea <span class="hlt">ice</span> in one summer is "remembered" in reduced <span class="hlt">ice</span> thickness over the winter season and leads to a comparably dramatic loss the following summer. The dominant contributor to this memory is presumably the sea <span class="hlt">ice</span> - albedo feedback (SIAF), in which excess insolation absorbed due to low summer <span class="hlt">ice</span> <span class="hlt">cover</span> leads to a shorter <span class="hlt">ice</span> growth season and hence thinner <span class="hlt">ice</span>. While these dynamics are clearly important, they are difficult to quantify given the lack of long-term observations in the Arctic and the suddenness of the recent loss. Alternatively, we attempt to quantify the contribution of the SIAF to the year-to-year memory of sea <span class="hlt">ice</span> <span class="hlt">cover</span> anomalies in simulations of the NCAR Community Climate System Model (CCSM) under 20th century conditions. Lagged autocorrelation plots of sea <span class="hlt">ice</span> area anomalies show that anomalies in one year tend to "reemerge" in the following year. Further experiments using a slab ocean model (SOM) are used to assess the contribution of oceanic processes to the year-to-year reemergence. This contribution is substantial, particularly in the winter season, and includes memory due to the standard mixed layer reemergence mechanism and low-frequency ocean heat transport anomalies. The contribution of the SIAF to persistence in the SOM experiment is determined through additional experiments in which the SIAF is disabled by fixing surface albedo to its climatological value regardless of sea <span class="hlt">ice</span> concentration anomalies. SIAF causes a 50% increase in the magnitude of the anomalies but a relatively small increase in their persistence. Persistence is not dramatically increased because the enhancement of shortwave flux anomalies by SIAF is compensated by stronger</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.481...61C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.481...61C"><span>Seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> during the warm Pliocene: Evidence from the Iceland Sea (ODP Site 907)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clotten, Caroline; Stein, Ruediger; Fahl, Kirsten; De Schepper, Stijn</p> <p>2018-01-01</p> <p>Sea <span class="hlt">ice</span> is a critical component in the Arctic and global climate system, yet little is known about its extent and variability during past warm intervals, such as the Pliocene (5.33-2.58 Ma). Here, we present the first multi-proxy (IP25, sterols, alkenones, palynology) sea <span class="hlt">ice</span> reconstructions for the Late Pliocene Iceland Sea (ODP Site 907). Our interpretation of a seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> with occasional <span class="hlt">ice</span>-free intervals between 3.50-3.00 Ma is supported by reconstructed alkenone-<span class="hlt">based</span> summer sea surface temperatures. As evidenced from brassicasterol and dinosterol, primary productivity was low between 3.50 and 3.00 Ma and the site experienced generally oligotrophic conditions. The East Greenland Current (and East Icelandic Current) may have transported sea <span class="hlt">ice</span> into the Iceland Sea and/or brought cooler and fresher waters favoring local sea <span class="hlt">ice</span> formation. Between 3.00 and 2.40 Ma, the Iceland Sea is mainly sea <span class="hlt">ice</span>-free, but seasonal sea <span class="hlt">ice</span> occurred between 2.81 and 2.74 Ma. Sea <span class="hlt">ice</span> extending into the Iceland Sea at this time may have acted as a positive feedback for the build-up of the Greenland <span class="hlt">Ice</span> Sheet (GIS), which underwent a major expansion ∼2.75 Ma. Thereafter, most likely a stable sea <span class="hlt">ice</span> edge developed close to Greenland, possibly changing together with the expansion and retreat of the GIS and affecting the productivity in the Iceland Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=67181&keyword=LAKE+AND+ICE&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=67181&keyword=LAKE+AND+ICE&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>SIMULATED CLIMATE CHANGE EFFECTS ON DISSOLVED OXYGEN CHARACTERISTICS IN <span class="hlt">ICE-COVERED</span> LAKES. (R824801)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A deterministic, one-dimensional model is presented which simulates daily dissolved oxygen (DO) profiles and associated water temperatures, <span class="hlt">ice</span> <span class="hlt">covers</span> and snow <span class="hlt">covers</span> for dimictic and polymictic lakes of the temperate zone. The lake parameters required as model input are surface ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C21C0702N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C21C0702N"><span>The cloud-radiative processes and its modulation by sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and stability as derived from a merged C3M Data product.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nag, B.</p> <p>2016-12-01</p> <p>The polar regions of the world constitute an important sector in the global energy balance. Among other effects responsible for the change in the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> like ocean circulation and <span class="hlt">ice</span>-albedo feedback, the cloud-radiation feedback also plays a vital role in modulation of the Arctic environment. However the annual cycle of the clouds is very poorly represented in current global circulation models. This study aims to take advantage of a merged C3M data (CALIPSO, CloudSat, CERES, and MODIS) product from the NASA's A-Train Series to explore the sea-<span class="hlt">ice</span> and atmospheric conditions in the Arctic on a spatial coverage spanning 70N to 80N. This study is aimed at the interactions or the feedbacks processes among sea-<span class="hlt">ice</span>, clouds and the atmosphere. Using a composite approach <span class="hlt">based</span> on a classification due to surface type, it is found that limitation of the water vapour influx from the surface due to change in phase at the surface featuring open oceans or marginal sea-<span class="hlt">ice</span> <span class="hlt">cover</span> to complete sea-<span class="hlt">ice</span> <span class="hlt">cover</span> is a major determinant in the modulation of the atmospheric moisture and its impacts. The impact of the cloud-radiative effects in the Arctic is found to vary with sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and seasonally. The effect of the marginal sea-<span class="hlt">ice</span> <span class="hlt">cover</span> becomes more and more pronounced in the winter. The seasonal variation of the dependence of the atmospheric moisture on the surface and the subsequent feedback effects is controlled by the atmospheric stability measured as a difference between the potential temperature at the surface and the 700hPa level. It is found that a stronger stability <span class="hlt">cover</span> in the winter is responsible for the longwave cloud radiative feedback in winter which is missing during the summer. A regional analysis of the same suggests that most of the depiction of the variations observed is contributed from the North Atlantic region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17636293','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17636293"><span>The contribution of <span class="hlt">ice</span> <span class="hlt">cover</span> to sediment resuspension in a shallow temperate lake: possible effects of climate change on internal nutrient loading.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Niemistö, Juha P; Horppila, Jukka</p> <p>2007-01-01</p> <p>The effect of <span class="hlt">ice</span> <span class="hlt">cover</span> on sediment resuspension and internal total P (Tot-P) loading was studied in the northern temperate Kirkkojärvi basin in Finland. The gross sedimentation and resuspension rates were estimated with sediment traps during <span class="hlt">ice-cover</span> and <span class="hlt">ice</span>-free periods. After <span class="hlt">ice</span> break, the average gross sedimentation rate increased from 1.4 to 30.0 g dw m(-2) d(-1). Resuspension calculations showed clearly higher values after <span class="hlt">ice</span> break as well. Under <span class="hlt">ice</span> <span class="hlt">cover</span>, resuspension ranged from 50 to 78% of the gross sedimentation while during the <span class="hlt">ice</span>-free period it constituted from 87 to 97% of the gross sedimentation. Consequently, the average resuspension rate increased from 1.0 g dw m(-2) d(-1) under <span class="hlt">ice-cover</span> to 27.0 g dw m(-2) d(-1) after thaw, indicating the strong effect of <span class="hlt">ice</span> <span class="hlt">cover</span> on sediment resuspension. To estimate the potential effect of climate change on internal P loading caused by resuspension we compared the Tot-P loading calculations between the present climate and the climate with doubled atmospheric CO2 concentration relative to the present day values (<span class="hlt">ice</span> <span class="hlt">cover</span> reduced from current 165 to 105 d). The annual load increased from 7.4 to 9.4 g m(-2). In conclusion, the annual internal Tot-P loading caused by resuspension will increase by 28% in the Kirkkojärvi basin if the 2xCO2 climate scenario comes true.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17164851','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17164851"><span>Polarization of 'water-skies' above arctic open waters: how polynyas in the <span class="hlt">ice-cover</span> can be visually detected from a distance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hegedüs, Ramón; Akesson, Susanne; Horváth, Gábor</p> <p>2007-01-01</p> <p>The foggy sky above a white <span class="hlt">ice-cover</span> and a dark water surface (permanent polynya or temporary lead) is white and dark gray, phenomena called the '<span class="hlt">ice</span>-sky' and the 'water-sky,' respectively. Captains of icebreaker ships used to search for not-directly-visible open waters remotely on the basis of the water sky. Animals depending on open waters in the Arctic region may also detect not-directly-visible waters from a distance by means of the water sky. Since the polarization of <span class="hlt">ice</span>-skies and water-skies has not, to our knowledge, been studied before, we measured the polarization patterns of water-skies above polynyas in the arctic <span class="hlt">ice-cover</span> during the Beringia 2005 Swedish polar research expedition to the North Pole region. We show that there are statistically significant differences in the angle of polarization between the water-sky and the <span class="hlt">ice</span>-sky. This polarization phenomenon could help biological and man-made sensors to detect open waters not directly visible from a distance. However, the threshold of polarization-<span class="hlt">based</span> detection would be rather low, because the degree of linear polarization of light radiated by water-skies and <span class="hlt">ice</span>-skies is not higher than 10%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41B1208W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41B1208W"><span>Determining Distributed Ablation over Dirty <span class="hlt">Ice</span> Areas of Debris-<span class="hlt">covered</span> Glaciers Using a UAV-SfM Approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woodget, A.; Fyffe, C. L.; Kirkbride, M. P.; Deline, P.; Westoby, M.; Brock, B. W.</p> <p>2017-12-01</p> <p>Dirty <span class="hlt">ice</span> areas (where debris <span class="hlt">cover</span> is discontinuous) are often found on debris-<span class="hlt">covered</span> glaciers above the limit of continuous debris and are important because they are areas of high melt and have been recognized as the locus of the identified upglacier increase in debris <span class="hlt">cover</span>. The modelling of glacial ablation in areas of dirty <span class="hlt">ice</span> is in its infancy and is currently restricted to theoretical studies. Glacial ablation is traditionally determined at point locations using stakes drilled into the <span class="hlt">ice</span>. However, in areas of dirty <span class="hlt">ice</span>, ablation is highly spatially variable, since debris a few centimetres thick is near the threshold between enhancing and reducing ablation. As a result, it is very difficult to ascertain if point ablation measurements are representative of ablation of the area surrounding the stake - making these measurements unsuitable for the validation of models of dirty <span class="hlt">ice</span> ablation. This paper aims to quantify distributed ablation and its relationship to essential dirty <span class="hlt">ice</span> characteristics with a view to informing the construction of dirty <span class="hlt">ice</span> melt models. A novel approach to determine distributed ablation is presented which uses repeat aerial imagery acquired from a UAV (Unmanned Aerial Vehicle), processed using SfM (Structure from Motion) techniques, on an area of dirty <span class="hlt">ice</span> on Miage Glacier, Italian Alps. A spatially continuous ablation map is presented, along with a correlation to the local debris characteristics. Furthermore, methods are developed which link ground truth data on the percentage debris <span class="hlt">cover</span>, albedo and clast depth to the UAV imagery, allowing these characteristics to be determined for the entire study area, and used as model inputs. For example, debris thickness is determined through a field relationship with clast size, which is then correlated with image texture and point cloud roughness metrics derived from the UAV imagery. Finally, we evaluate the potential of our novel approach to lead to improved modelling of dirty <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16826993','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16826993"><span>Trends in sea <span class="hlt">ice</span> <span class="hlt">cover</span> within habitats used by bowhead whales in the western Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moore, Sue E; Laidre, Kristin L</p> <p>2006-06-01</p> <p>We examined trends in sea <span class="hlt">ice</span> <span class="hlt">cover</span> between 1979 and 2002 in four months (March, June, September, and November) for four large (approximately 100,000 km2) and 12 small (approximately 10,000 km2) regions of the western Arctic in habitats used by bowhead whales (Balaena mysticetus). Variation in open water with year was significant in all months except March, but interactions between region and year were not. Open water increased in both large and small regions, but trends were weak with least-squares regression accounting for < or =34% of the total variation. In large regions, positive trends in open water were strongest in September. Linear fits were poor, however, even in the East Siberian, Chukchi, and Beaufort seas, where basin-scale analyses have emphasized dramatic sea <span class="hlt">ice</span> loss. Small regions also showed weak positive trends in open water and strong interannual variability. Open water increased consistently in five small regions where bowhead whales have been observed feeding or where oceanographic models predict prey entrainment, including: (1) June, along the northern Chukotka coast, near Wrangel Island, and along the Beaufort slope; (2) September, near Wrangel Island, the Barrow Arc, and the Chukchi Borderland; and (3) November, along the Barrow Arc. Conversely, there was very little consistent change in sea <span class="hlt">ice</span> <span class="hlt">cover</span> in four small regions considered winter refugia for bowhead whales in the northern Bering Sea, nor in two small regions that include the primary springtime migration corridor in the Chukchi Sea. The effects of sea <span class="hlt">ice</span> <span class="hlt">cover</span> on bowhead whale prey availability are unknown but can be modeled via production and advection pathways. Our conceptual model suggests that reductions in sea <span class="hlt">ice</span> <span class="hlt">cover</span> will increase prey availability along both pathways for this population. This analysis elucidates the variability inherent in the western Arctic marine ecosystem at scales relevant to bowhead whales and contrasts basin-scale depictions of extreme sea <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS31B1256L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS31B1256L"><span>The Effects of Freezing, Melting and Partial <span class="hlt">Ice</span> <span class="hlt">Cover</span> on Gas Transport in Laboratory Seawater Experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loose, B.; McGillis, W.; Schlosser, P.; Perovich, D.; Takahashi, T.</p> <p>2008-12-01</p> <p>Sea <span class="hlt">ice</span> physico-chemical processes affect gas dynamics, which may be relevant to polar ocean budgets of climatically-active gases. We used SF6 and O2 as inert gas tracers in a tank experiment to observe the transport of gases between water, <span class="hlt">ice</span> and air during freezing/melting and partial <span class="hlt">ice</span> <span class="hlt">cover</span>. The results show that during <span class="hlt">ice</span> growth, the rejection of O2 and SF6 was greater than the rejection of salt per unit of ambient concentration in seawater. Unconsolidated <span class="hlt">ice</span> crystal growth produced an increase in dissolved O2 concentration, indicating that the water-air gradient may favor gas evasion during the early stages of sea-<span class="hlt">ice</span> formation. Measurements of the gas transfer velocity (k), using SF6 and O2 during conditions of partial <span class="hlt">ice</span> <span class="hlt">cover</span> exceed the proportionality between the fraction of open water and k determined between 0% and 100% open water conditions. At 15% open water, k equals 35% of k during <span class="hlt">ice</span>-free conditions, indicating the importance of under-<span class="hlt">ice</span> turbulence for gas exchange. In our experiments most of this turbulence was produced by pumps installed for circulation of the water in the tank to avoid density stratification. Varying the turbulent kinetic energy (TKE) delivered to the water by these pumps produced a correspondent variation in k. Measurements of TKE using particle velocimetry suggest that turbulence in the <span class="hlt">ice</span>-water boundary layer dominated the convection driven by heat loss through the open water, and the magnitude of net TKE production was similar to that measured beneath drifting <span class="hlt">ice</span> in the field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B33K0614C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B33K0614C"><span>Carbon and hydrogen isotopic systematics of dissolved methane in small seasonally <span class="hlt">ice-covered</span> lakes near the margin of the Greenland <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cadieux, S. B.; White, J. R.; Pratt, L. M.; Peng, Y.; Young, S. A.</p> <p>2013-12-01</p> <p>Northern lakes contribute from 6-16% of annual methane inputs to Earth's atmosphere, yet little is known about the seasonal biogeochemistry of CH4 cycling, particularly for lakes in the Arctic. Studies during <span class="hlt">ice</span>-free conditions have been conducted in Alaskan, Swedish and Siberian lakes. However, there is little information on CH4 cycling under <span class="hlt">ice-covered</span> conditions, and few stable isotopic measurements, which can help elucidate production and consumption pathways. In order to better understand methane dynamics of <span class="hlt">ice-covered</span> Arctic lakes, 4 small lakes (surface area <1 km2) within a narrow valley extending from the Russells Glacier to Søndre Strømfjord in Southwestern Greenland were examined during summer stratification and winter <span class="hlt">ice-cover</span>. Lakes in the study area are <span class="hlt">ice-covered</span> from mid-September to mid-June. In both seasons, variations in the concentrations and isotopic composition of methane with depth were related to redox fluctuations. During late winter under~2 m of <span class="hlt">ice</span>, the entire water column was anoxic with wide variation in methane concentrationsand isotopic composition from lake to lake. In three of the lakes, CH4 concentrations and δ13C were relatively stable over the depth of the water column, averaging from 120 to 480μM, with δ13CH4 values from -56‰ to -66‰, respectively. Methane concentrations in the other lake increased with depth from <1 μM below the <span class="hlt">ice</span> to 800 μM at the sediment/water interface, while δ13C decreased by 30‰ from -30‰ to -70‰ over this depth. In all the lakes, δ13C of sediment porewater was lighter than the overlying water by at least 10‰. The δD-CH4 in the water column ranged from -370‰ to -50‰, exhibiting covariance with δ13C consistent with significant methanotrophic activity. In the sediment, δD-CH4 values ranged from -330‰ to -275‰, and were inversely correlated with δ13C. We will present detailed information on redox dynamics as a controlling factor in methane cycling, and explore the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C42B..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C42B..06R"><span>Response of Debris-<span class="hlt">Covered</span> and Clean-<span class="hlt">Ice</span> Glaciers to Climate Change from Observations and Modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rupper, S.; Maurer, J. M.; Schaefer, J. M.; Roe, G.; Huybers, K. M.</p> <p>2017-12-01</p> <p>Debris-<span class="hlt">covered</span> glaciers form a significant percentage of the glacier area and volume in many mountainous regions of the world, and respond differently to climatic forcings as compared to clean-<span class="hlt">ice</span> glaciers. In particular, debris-<span class="hlt">covered</span> glaciers tend to downwaste with very little retreat, while clean-<span class="hlt">ice</span> glaciers simultaneously thin and retreat. This difference has posed a significant challenge to quantifying glacier sensitivity to climate change, modeling glacier response to future climate change, and assessing the impacts of recent and future glacier changes on mountain environments and downstream populations. In this study, we evaluate observations of the geodetic mass balance and thinning profiles of 1000 glaciers across the Himalayas from 1975 to 2016. We use this large sampling of glacier changes over multiple decades to provide a robust statistical comparison of mass loss for clean-<span class="hlt">ice</span> versus debris-<span class="hlt">covered</span> glaciers over a period relevant to glacier dynamics. In addition, we force a glacier model with a series of climate change scenarios, and compare the modeled results to the observations. We essentially ask the question, "Are our theoretical expectations consistent with the observations?" Our observations show both clean-<span class="hlt">ice</span> and debris-<span class="hlt">covered</span> glaciers, regionally averaged, thinned in a similar pattern for the first 25-year observation period. For the more recent 15-year period, clean <span class="hlt">ice</span> glaciers show significantly steepened thinning gradients across the surface, while debris-<span class="hlt">covered</span> glaciers have continued to thin more uniformaly across the surface. Our preliminary model results generally agree with these observations, and suggest that both glacier types are expected to have a thinning phase followed by a retreat phase, but that the timing of the retreat phase is much later for debris-<span class="hlt">covered</span> glaciers. Thus, these early results suggest these two glacier types are dynamically very similar, but are currently in different phases of response to recent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.U42A0010M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.U42A0010M"><span>The Rapidly Diminishing Arctic <span class="hlt">ice</span> <span class="hlt">Cover</span> and its Potential Impact on Navy Operational Considerations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muench, R. D.; Conlon, D.; Lamb, D.</p> <p>2001-12-01</p> <p>Observations made from U.S. Navy Fleet submarines during the 1990s have revealed a dramatic decrease in thickness, when compared to historical values, of the central Arctic Ocean pack <span class="hlt">ice</span> <span class="hlt">cover</span>. Estimates of this decrease have been as high as 40%. Remote sensing observations have shown a coincident decrease in the areal extent of the pack. The areal decrease has been especially apparent during winter. The overall loss of <span class="hlt">ice</span> appears to have accelerated over the past decade, raising the possibility that the Northwest Passage and the Northern Sea Route may become seasonally navigable on a regular basis in the coming decade. The <span class="hlt">ice</span> loss has been most evident in the peripheral seas and continental shelf areas. For example, during winter 2000-2001 the Bering Sea was effectively <span class="hlt">ice</span>-free, with strong and immediate impacts on the surrounding indigenous populations. Lessening of the peripheral pack <span class="hlt">ice</span> <span class="hlt">cover</span> will presumably, lead to accelerated development of the resource-rich regions that surround the deep, central Arctic Ocean basin. This raises potential issues with respect to national security and commercial interests, and has implicit strategic concerns for the Navy. The timeline for a significantly navigable Arctic may extend decades into the future; however, operational requirements must be identified in the nearer term to ensure that the necessary capabilities exist when future Arctic missions do present themselves. A first step is to improve the understanding of the coupled atmosphere/<span class="hlt">ice</span>/ocean system. Current environmental measurement and prediction, including Arctic weather and <span class="hlt">ice</span> prediction, shallow water acoustic performance prediction, dynamic ocean environmental changes and data to support navigation is inadequate to support sustained naval operations in the Arctic. A new focus on data collection is required in order to measure, map, monitor and model Arctic weather, <span class="hlt">ice</span> and oceanographic conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/1012990','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/1012990"><span>Variations in the Arctic's multiyear sea <span class="hlt">ice</span> <span class="hlt">cover</span>: A neural network analysis of SMMR-SSM/I data, 1979-2004</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Belchansky, G.I.; Douglas, David C.; Eremeev, V.A.; Platonov, Nikita G.</p> <p>2005-01-01</p> <p>A 26-year (1979-2004) observational record of January multiyear sea <span class="hlt">ice</span> distributions, derived from neural network analysis of SMMR-SSM/I passive microwave satellite data, reveals dense and persistent <span class="hlt">cover</span> in the central Arctic basin surrounded by expansive regions of highly fluctuating interannual <span class="hlt">cover</span>. Following a decade of quasi equilibrium, precipitous declines in multiyear <span class="hlt">ice</span> area commenced in 1989 when the Arctic Oscillation shifted to a pronounced positive phase. Although extensive survival of first-year <span class="hlt">ice</span> during autumn 1996 fully replenished the area of multiyear <span class="hlt">ice</span>, a subsequent and accelerated decline returned the depletion to record lows. The most dramatic multiyear sea <span class="hlt">ice</span> declines occurred in the East Siberian, Chukchi, and Beaufort Seas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28378830','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28378830"><span>Possible connections of the opposite trends in Arctic and Antarctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A; Zhou, Mingyu; Lenschow, Donald H; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua</p> <p>2017-04-05</p> <p>Sea <span class="hlt">ice</span> is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-<span class="hlt">ice</span> concentration is evident in recent years, whereas Antarctic sea-<span class="hlt">ice</span> concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-<span class="hlt">ice</span> concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-<span class="hlt">ice</span> concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-<span class="hlt">ice</span> concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-<span class="hlt">ice</span> concentration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381096','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381096"><span>Possible connections of the opposite trends in Arctic and Antarctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A.; Zhou, Mingyu; Lenschow, Donald H.; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua</p> <p>2017-01-01</p> <p>Sea <span class="hlt">ice</span> is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-<span class="hlt">ice</span> concentration is evident in recent years, whereas Antarctic sea-<span class="hlt">ice</span> concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-<span class="hlt">ice</span> concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-<span class="hlt">ice</span> concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-<span class="hlt">ice</span> concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-<span class="hlt">ice</span> concentration. PMID:28378830</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSHE54B1584J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSHE54B1584J"><span>The interaction between sea <span class="hlt">ice</span> and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea-<span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jensen, M. F.; Nilsson, J.; Nisancioglu, K. H.</p> <p>2016-02-01</p> <p>In this study, we develop a simple conceptual model to examine how interactions between sea <span class="hlt">ice</span> and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea-<span class="hlt">ice</span> <span class="hlt">covered</span> and salinity stratified ocean, and consists of a sea-<span class="hlt">ice</span> component and a two-layer ocean; a cold, fresh surface layer above a warmer, more saline layer. The sea-<span class="hlt">ice</span> thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea-<span class="hlt">ice</span> export. Whether sea <span class="hlt">ice</span> stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the vertical mixing. In a system where the vertical diffusivity is constant, the sea <span class="hlt">ice</span> acts as a positive feedback on a freshwater perturbation. If the vertical diffusivity is derived from a constant mixing energy constraint, the sea <span class="hlt">ice</span> acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea <span class="hlt">ice</span>. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea <span class="hlt">ice</span>. Generally, the unstable state is reached before the vertical density difference disappears, and small changes in temperature and freshwater inputs can provoke abrupt changes in sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740014858','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740014858"><span>Results of the US contribution to the joint US/USSR Bering Sea experiment. [atmospheric circulation and sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Campbell, W. J.; Chang, T. C.; Fowler, M. G.; Gloersen, P.; Kuhn, P. M.; Ramseier, R. O.; Ross, D. B.; Stambach, G.; Webster, W. J., Jr.; Wilheit, T. T.</p> <p>1974-01-01</p> <p>The atmospheric circulation which occurred during the Bering Sea Experiment, 15 February to 10 March 1973, in and around the experiment area is analyzed and related to the macroscale morphology and dynamics of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. The <span class="hlt">ice</span> <span class="hlt">cover</span> was very complex in structure, being made up of five <span class="hlt">ice</span> types, and underwent strong dynamic activity. Synoptic analyses show that an optimum variety of weather situations occurred during the experiment: an initial strong anticyclonic period (6 days), followed by a period of strong cyclonic activity (6 days), followed by weak anticyclonic activity (3 days), and finally a period of weak cyclonic activity (4 days). The data of the mesoscale test areas observed on the four sea <span class="hlt">ice</span> option flights, and ship weather, and drift data give a detailed description of mesoscale <span class="hlt">ice</span> dynamics which correlates well with the macroscale view: anticyclonic activity advects the <span class="hlt">ice</span> southward with strong <span class="hlt">ice</span> divergence and a regular lead and polynya pattern; cyclonic activity advects the <span class="hlt">ice</span> northward with <span class="hlt">ice</span> convergence, or slight divergence, and a random lead and polynya pattern.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.8557L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.8557L"><span>Rollover of Apparent Wave Attenuation in <span class="hlt">Ice</span> <span class="hlt">Covered</span> Seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Jingkai; Kohout, Alison L.; Doble, Martin J.; Wadhams, Peter; Guan, Changlong; Shen, Hayley H.</p> <p>2017-11-01</p> <p>Wave attenuation from two field experiments in the <span class="hlt">ice-covered</span> Southern Ocean is examined. Instead of monotonically increasing with shorter waves, the measured apparent attenuation rate peaks at an intermediate wave period. This "rollover" phenomenon has been postulated as the result of wind input and nonlinear energy transfer between wave frequencies. Using WAVEWATCH III®, we first validate the model results with available buoy data, then use the model data to analyze the apparent wave attenuation. With the choice of source parameterizations used in this study, it is shown that rollover of the apparent attenuation exists when wind input and nonlinear transfer are present, independent of the different wave attenuation models used. The period of rollover increases with increasing distance between buoys. Furthermore, the apparent attenuation for shorter waves drops with increasing separation between buoys or increasing wind input. These phenomena are direct consequences of the wind input and nonlinear energy transfer, which offset the damping caused by the intervening <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3020R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3020R"><span>Determining the <span class="hlt">ice</span> seasons severity during 1982-2015 using the <span class="hlt">ice</span> extents sum as a new characteristic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rjazin, Jevgeni; Pärn, Ove</p> <p>2016-04-01</p> <p>Sea <span class="hlt">ice</span> is a key climate factor and it restricts considerably the winter navigation in sever seasons on the Baltic Sea. So determining <span class="hlt">ice</span> conditions severity and describing <span class="hlt">ice</span> <span class="hlt">cover</span> behaviour at severe seasons interests scientists, engineers and navigation managers. The present study is carried out to determine the <span class="hlt">ice</span> seasons severity degree <span class="hlt">basing</span> on the <span class="hlt">ice</span> seasons 1982 to 2015. A new integrative characteristic is introduced to describe the <span class="hlt">ice</span> season severity. It is the sum of <span class="hlt">ice</span> extents of the <span class="hlt">ice</span> season id est the daily <span class="hlt">ice</span> extents of the season are summed. The commonly used procedure to determine the <span class="hlt">ice</span> season severity degree by the maximal <span class="hlt">ice</span> extent is in this research compared to the new characteristic values. The remote sensing data on the <span class="hlt">ice</span> concentrations on the Baltic Sea published in the European Copernicus Programme are used to obtain the severity characteristic values. The <span class="hlt">ice</span> extents are calculated on these <span class="hlt">ice</span> concentration data. Both the maximal <span class="hlt">ice</span> extent of the season and a newly introduced characteristic - the <span class="hlt">ice</span> extents sum are used to classify the winters with respect of severity. The most severe winter of the reviewed period is 1986/87. Also the <span class="hlt">ice</span> seasons 1981/82, 1984/85, 1985/86, 1995/96 and 2002/03 are classified as severe. Only three seasons of this list are severe by both the criteria. They are 1984/85, 1985/86 and 1986/87. We interpret this coincidence as the evidence of enough-during extensive <span class="hlt">ice</span> <span class="hlt">cover</span> in these three seasons. In several winters, for example 2010/11 <span class="hlt">ice</span> <span class="hlt">cover</span> extended enough for some time, but did not endure. At few other <span class="hlt">ice</span> seasons as 2002/03 the Baltic Sea was <span class="hlt">ice-covered</span> in moderate extent, but the <span class="hlt">ice</span> <span class="hlt">cover</span> stayed long time. At 11 winters the <span class="hlt">ice</span> extents sum differed considerably (> 10%) from the maximal <span class="hlt">ice</span> extent. These winters yield one third of the studied <span class="hlt">ice</span> seasons. The maximal <span class="hlt">ice</span> extent of the season is simple to use and enables to reconstruct the <span class="hlt">ice</span> <span class="hlt">cover</span> history and to predict maximal <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27458438','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27458438"><span>Unanticipated Geochemical and Microbial Community Structure under Seasonal <span class="hlt">Ice</span> <span class="hlt">Cover</span> in a Dilute, Dimictic Arctic Lake.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schütte, Ursel M E; Cadieux, Sarah B; Hemmerich, Chris; Pratt, Lisa M; White, Jeffrey R</p> <p>2016-01-01</p> <p>Despite most lakes in the Arctic being perennially or seasonally frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under <span class="hlt">ice</span> <span class="hlt">cover</span>. We assessed the vertical microbial community distribution and geochemical composition in early spring under <span class="hlt">ice</span> in a seasonally <span class="hlt">ice-covered</span> lake in southwest Greenland using amplicon-<span class="hlt">based</span> sequencing that targeted 16S rRNA genes and using a combination of field and laboratory aqueous geochemical methods. Microbial communities changed consistently with changes in geochemistry. Composition of the abundant members responded strongly to redox conditions, shifting downward from a predominantly heterotrophic aerobic community in the suboxic waters to a heterotrophic anaerobic community in the anoxic waters. Operational taxonomic units (OTUs) of Sporichthyaceae, Comamonadaceae, and the SAR11 Clade had higher relative abundances above the oxycline and OTUs within the genus Methylobacter, the phylum Lentisphaerae, and purple sulfur bacteria (PSB) below the oxycline. Notably, a 13-fold increase in sulfide at the oxycline was reflected in an increase and change in community composition of potential sulfur oxidizers. Purple non-sulfur bacteria were present above the oxycline and green sulfur bacteria and PSB coexisted below the oxycline, however, PSB were most abundant. For the first time we show the importance of PSB as potential sulfur oxidizers in an Arctic dimictic lake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271"><span>Decreasing cloud <span class="hlt">cover</span> drives the recent mass loss on the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hofer, Stefan; Tedstone, Andrew J.; Fettweis, Xavier; Bamber, Jonathan L.</p> <p>2017-01-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud <span class="hlt">cover</span> enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud <span class="hlt">cover</span> decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud <span class="hlt">cover</span>, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud <span class="hlt">cover</span> is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation. PMID:28782014</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28782014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28782014"><span>Decreasing cloud <span class="hlt">cover</span> drives the recent mass loss on the Greenland <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofer, Stefan; Tedstone, Andrew J; Fettweis, Xavier; Bamber, Jonathan L</p> <p>2017-06-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud <span class="hlt">cover</span> enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud <span class="hlt">cover</span> decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud <span class="hlt">cover</span>, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud <span class="hlt">cover</span> is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C21C0631S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C21C0631S"><span>Lake <span class="hlt">Ice</span> <span class="hlt">Cover</span> of Shallow Lakes and Climate Interactions in Arctic Regions (1950-2011): SAR Data Analysis and Numerical Modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Surdu, C.; Duguay, C.; Brown, L.; Fernàndez-Prieto, D.; Samuelsson, P.</p> <p>2012-12-01</p> <p>Lake <span class="hlt">ice</span> <span class="hlt">cover</span> is highly correlated with climatic conditions and has, therefore, been demonstrated to be an essential indicator of climate variability and change. Recent studies have shown that the duration of the lake <span class="hlt">ice</span> <span class="hlt">cover</span> has decreased, mainly as a consequence of earlier thaw dates in many parts of the Northern Hemisphere over the last 50 years, mainly as a feedback to increased winter and spring air temperature. In response to projected air temperature and winter precipitation changes by climate models until the end of the 21st century, the timing, duration, and thickness of <span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic lakes are expected to be impacted. This, in turn, will likely alter the energy, water, and bio-geochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that fully freeze to the bottom at the time of maximum winter <span class="hlt">ice</span> thickness since thinner <span class="hlt">ice</span> <span class="hlt">covers</span> are predicted to develop. Shallow thermokarst lakes of the coastal plain of northern Alaska, and of other similar Arctic regions, have likely been experiencing changes in seasonal <span class="hlt">ice</span> phenology and thickness over the last few decades but these have not yet been comprehensively documented. Analysis of a 20-year time series of ERS-1/2 synthetic aperture radar (SAR) data and numerical lake <span class="hlt">ice</span> modeling were employed to determine the response of <span class="hlt">ice</span> <span class="hlt">cover</span> (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last three decades. New downscaled data specific to the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre Regional Atmospheric Climate Model (RCA4) was used to drive the Canadian Lake <span class="hlt">Ice</span> Model (CLIMo) for the period 1950-2011. In order to assess and integrate the SAR-derived observed changes into a longer historical context, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAr42.3.1765W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAr42.3.1765W"><span>Snow <span class="hlt">Cover</span> Mapping and <span class="hlt">Ice</span> Avalanche Monitoring from the Satellite Data of the Sentinels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, S.; Yang, B.; Zhou, Y.; Wang, F.; Zhang, R.; Zhao, Q.</p> <p>2018-04-01</p> <p>In order to monitor <span class="hlt">ice</span> avalanches efficiently under disaster emergency conditions, a snow <span class="hlt">cover</span> mapping method <span class="hlt">based</span> on the satellite data of the Sentinels is proposed, in which the coherence and backscattering coefficient image of Synthetic Aperture Radar (SAR) data (Sentinel-1) is combined with the atmospheric correction result of multispectral data (Sentinel-2). The coherence image of the Sentinel-1 data could be segmented by a certain threshold to map snow <span class="hlt">cover</span>, with the water bodies extracted from the backscattering coefficient image and removed from the coherence segment result. A snow confidence map from Sentinel-2 was used to map the snow <span class="hlt">cover</span>, in which the confidence values of the snow <span class="hlt">cover</span> were relatively high. The method can make full use of the acquired SAR image and multispectral image under emergency conditions, and the application potential of Sentinel data in the field of snow <span class="hlt">cover</span> mapping is exploited. The monitoring frequency can be ensured because the areas obscured by thick clouds are remedied in the monitoring results. The Kappa coefficient of the monitoring results is 0.946, and the data processing time is less than 2 h, which meet the requirements of disaster emergency monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11543521','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11543521"><span>Sedimentology and geochemistry of a perennially <span class="hlt">ice-covered</span> epishelf lake in Bunger Hills Oasis, East Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T</p> <p>2000-01-01</p> <p>A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially <span class="hlt">ice-covered</span> (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier <span class="hlt">ice</span> surrounding the sediment is sublimated at the surface and replaced by accumulating <span class="hlt">ice</span> from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment <span class="hlt">cover</span>. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment <span class="hlt">cover</span> indicate that the west end has formed only over the last century. Our results indicate that the southern <span class="hlt">ice</span> edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO24A2918F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO24A2918F"><span>Simulating hydrodynamics and <span class="hlt">ice</span> <span class="hlt">cover</span> in Lake Erie using an unstructured grid model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujisaki-Manome, A.; Wang, J.</p> <p>2016-02-01</p> <p>An unstructured grid Finite-Volume Coastal Ocean Model (FVCOM) is applied to Lake Erie to simulate seasonal <span class="hlt">ice</span> <span class="hlt">cover</span>. The model is coupled with an unstructured-grid, finite-volume version of the Los Alamos Sea <span class="hlt">Ice</span> Model (UG-CICE). We replaced the original 2-time-step Euler forward scheme in time integration by the central difference (i.e., leapfrog) scheme to assure a neutrally inertial stability. The modified version of FVCOM coupled with the <span class="hlt">ice</span> model is applied to the shallow freshwater lake in this study using unstructured grids to represent the complicated coastline in the Laurentian Great Lakes and refining the spatial resolution locally. We conducted multi-year simulations in Lake Erie from 2002 to 2013. The results were compared with the observed <span class="hlt">ice</span> extent, water surface temperature, <span class="hlt">ice</span> thickness, currents, and water temperature profiles. Seasonal and interannual variation of <span class="hlt">ice</span> extent and water temperature was captured reasonably, while the modeled thermocline was somewhat diffusive. The modeled <span class="hlt">ice</span> thickness tends to be systematically thinner than the observed values. The modeled lake currents compared well with measurements obtained from an Acoustic Doppler Current Profiler located in the deep part of the lake, whereas the simulated currents deviated from measurements near the surface, possibly due to the model's inability to reproduce the sharp thermocline during the summer and the lack of detailed representation of offshore wind fields in the interpolated meteorological forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PolSc..11...72R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PolSc..11...72R"><span>Plankton assembly in an ultra-oligotrophic Antarctic lake over the summer transition from the <span class="hlt">ice-cover</span> to <span class="hlt">ice</span>-free period: A size spectra approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rochera, Carlos; Quesada, Antonio; Toro, Manuel; Rico, Eugenio; Camacho, Antonio</p> <p>2017-03-01</p> <p>Lakes from the Antarctic maritime region experience climate change as a main stressor capable of modifying their plankton community structure and function, essentially because summer temperatures are commonly over the freezing point and the lake's <span class="hlt">ice</span> cap thaws. This study was conducted in such seasonally <span class="hlt">ice-covered</span> lake (Lake Limnopolar, Byers Peninsula, Livingston Is., Antarctica), which exhibits a microbial dominated pelagic food web. An important feature is also the occurrence of benthic mosses (Drepanocladus longifolius) <span class="hlt">covering</span> the lake bottom. Plankton dynamics were investigated during the <span class="hlt">ice</span>-thawing transition to the summer maximum. Both bacterioplankton and viral-like particles were higher near the lake's bottom, suggesting a benthic support. When the lake was under dim conditions because of the snow-and-<span class="hlt">ice</span> <span class="hlt">cover</span>, autotrophic picoplankters dominated at deep layers. The taxa-specific photopigments indicated dominance of picocyanobacteria among them when the light availability was lower. By contrast, larger and less edible phytoplankton dominated at the onset of the <span class="hlt">ice</span> melting. The plankton size spectra were fitted to the continuous model of Pareto distribution. Spectra evolved similarly at two sampled depths, in surface and near the bottom, with slopes increasing until mid-January. However, slopes were less steep (i.e., size classes more uniformly distributed) at the bottom, thus denoting a more efficient utilization of resources. These findings suggest that microbial loop pathways in the lake are efficiently channelized during some periods to the metazoan production (mainly the copepod Boeckella poppei). Our results point to that trophic interactions may still occur in these lakes despite environmental harshness. This results of interest in a framework of increasing temperatures that may reduce the climatic restrictions and therefore stimulate biotic interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2033D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2033D"><span><span class="hlt">Ice</span> bridges and ridges in the Maxwell-EB sea <span class="hlt">ice</span> rheology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dansereau, Véronique; Weiss, Jérôme; Saramito, Pierre; Lattes, Philippe; Coche, Edmond</p> <p>2017-09-01</p> <p>This paper presents a first implementation of a new rheological model for sea <span class="hlt">ice</span> on geophysical scales. This continuum model, called Maxwell elasto-brittle (Maxwell-EB), is <span class="hlt">based</span> on a Maxwell constitutive law, a progressive damage mechanism that is coupled to both the elastic modulus and apparent viscosity of the <span class="hlt">ice</span> <span class="hlt">cover</span> and a Mohr-Coulomb damage criterion that allows for pure (uniaxial and biaxial) tensile strength. The model is tested on the basis of its capability to reproduce the complex mechanical and dynamical behaviour of sea <span class="hlt">ice</span> drifting through a narrow passage. Idealized as well as realistic simulations of the flow of <span class="hlt">ice</span> through Nares Strait are presented. These demonstrate that the model reproduces the formation of stable <span class="hlt">ice</span> bridges as well as the stoppage of the flow, a phenomenon occurring within numerous channels of the Arctic. In agreement with observations, the model captures the propagation of damage along narrow arch-like kinematic features, the discontinuities in the velocity field across these features dividing the <span class="hlt">ice</span> <span class="hlt">cover</span> into floes, the strong spatial localization of the thickest, ridged <span class="hlt">ice</span>, the presence of landfast <span class="hlt">ice</span> in bays and fjords and the opening of polynyas downstream of the strait. The model represents various dynamical behaviours linked to an overall weakening of the <span class="hlt">ice</span> <span class="hlt">cover</span> and to the shorter lifespan of <span class="hlt">ice</span> bridges, with implications in terms of increased <span class="hlt">ice</span> export through narrow outflow pathways of the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918654J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918654J"><span>The possibility of a tipping point in the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, and associated early-warning signals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jastamin Steene, Rebekka</p> <p>2017-04-01</p> <p>As the Arctic sea <span class="hlt">ice</span> has become one of the primer indicators of global climate change, with a seemingly accelerated loss in both <span class="hlt">ice</span> extent and volume the latest decades, the existence of a tipping point related to the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has been widely debated. Several observed and potential abrupt transitions in the climate system may be interpreted as bifurcations in randomly driven dynamical systems. This means that a system approaching a bifurcation point shifts from one stable state to another, and we say that the system is subject to a critical transition. As the equilibrium states become unstable in the vicinity of a bifurcation point the characteristic relaxation times increases, and the system is said to experience a "critical slowing down". This makes it plausible to observe so called early-warning signals (EWS) when approaching a critical transition. In the Arctic non-linear mechanisms like the temperature response of the <span class="hlt">ice</span>-albedo feedback can potentially cause a sudden shift to an <span class="hlt">ice</span>-free Arctic Ocean. Using bifurcation theory and potential analyses we examine time series of observational data of the Arctic sea <span class="hlt">ice</span>, investigating the possibility of multiple states in the behavior of the <span class="hlt">ice</span> <span class="hlt">cover</span>. We further debate whether a shift between states is irreversible, and whether it can be preluded by early-warning signals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21637255','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21637255"><span>A dynamic early East Antarctic <span class="hlt">Ice</span> Sheet suggested by <span class="hlt">ice-covered</span> fjord landscapes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Young, Duncan A; Wright, Andrew P; Roberts, Jason L; Warner, Roland C; Young, Neal W; Greenbaum, Jamin S; Schroeder, Dustin M; Holt, John W; Sugden, David E; Blankenship, Donald D; van Ommen, Tas D; Siegert, Martin J</p> <p>2011-06-02</p> <p>The first Cenozoic <span class="hlt">ice</span> sheets initiated in Antarctica from the Gamburtsev Subglacial Mountains and other highlands as a result of rapid global cooling ∼34 million years ago. In the subsequent 20 million years, at a time of declining atmospheric carbon dioxide concentrations and an evolving Antarctic circumpolar current, sedimentary sequence interpretation and numerical modelling suggest that cyclical periods of <span class="hlt">ice</span>-sheet expansion to the continental margin, followed by retreat to the subglacial highlands, occurred up to thirty times. These fluctuations were paced by orbital changes and were a major influence on global sea levels. <span class="hlt">Ice</span>-sheet models show that the nature of such oscillations is critically dependent on the pattern and extent of Antarctic topographic lowlands. Here we show that the basal topography of the Aurora Subglacial Basin of East Antarctica, at present overlain by 2-4.5 km of <span class="hlt">ice</span>, is characterized by a series of well-defined topographic channels within a mountain block landscape. The identification of this fjord landscape, <span class="hlt">based</span> on new data from <span class="hlt">ice</span>-penetrating radar, provides an improved understanding of the topography of the Aurora Subglacial Basin and its surroundings, and reveals a complex surface sculpted by a succession of <span class="hlt">ice</span>-sheet configurations substantially different from today's. At different stages during its fluctuations, the edge of the East Antarctic <span class="hlt">Ice</span> Sheet lay pinned along the margins of the Aurora Subglacial Basin, the upland boundaries of which are currently above sea level and the deepest parts of which are more than 1 km below sea level. Although the timing of the channel incision remains uncertain, our results suggest that the fjord landscape was carved by at least two iceflow regimes of different scales and directions, each of which would have over-deepened existing topographic depressions, reversing valley floor slopes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29806697','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29806697"><span>The Arctic's sea <span class="hlt">ice</span> <span class="hlt">cover</span>: trends, variability, predictability, and comparisons to the Antarctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Serreze, Mark C; Meier, Walter N</p> <p>2018-05-28</p> <p>As assessed over the period of satellite observations, October 1978 to present, there are downward linear trends in Arctic sea <span class="hlt">ice</span> extent for all months, largest at the end of the melt season in September. The <span class="hlt">ice</span> <span class="hlt">cover</span> is also thinning. Downward trends in extent and thickness have been accompanied by pronounced interannual and multiyear variability, forced by both the atmosphere and ocean. As the <span class="hlt">ice</span> thins, its response to atmospheric and oceanic forcing may be changing. In support of a busier Arctic, there is a growing need to predict <span class="hlt">ice</span> conditions on a variety of time and space scales. A major challenge to providing seasonal scale predictions is the 7-10 days limit of numerical weather prediction. While a seasonally <span class="hlt">ice</span>-free Arctic Ocean is likely well within this century, there is much uncertainty in the timing. This reflects differences in climate model structure, the unknown evolution of anthropogenic forcing, and natural climate variability. In sharp contrast to the Arctic, Antarctic sea <span class="hlt">ice</span> extent, while highly variable, has increased slightly over the period of satellite observations. The reasons for this different behavior remain to be resolved, but responses to changing atmospheric circulation patterns appear to play a strong role. © 2018 New York Academy of Sciences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TMP...193.1801I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TMP...193.1801I"><span>Process of establishing a plane-wave system on <span class="hlt">ice</span> <span class="hlt">cover</span> over a dipole moving uniformly in an ideal fluid column</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Il'ichev, A. T.; Savin, A. S.</p> <p>2017-12-01</p> <p>We consider a planar evolution problem for perturbations of the <span class="hlt">ice</span> <span class="hlt">cover</span> by a dipole starting its uniform rectilinear horizontal motion in a column of an initially stationary fluid. Using asymptotic Fourier analysis, we show that at supercritical velocities, waves of two types form on the water-<span class="hlt">ice</span> interface. We describe the process of establishing these waves during the dipole motion. We assume that the fluid is ideal and incompressible and its motion is potential. The <span class="hlt">ice</span> <span class="hlt">cover</span> is modeled by the Kirchhoff-Love plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B52B..08F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B52B..08F"><span>Species interactions and response time to climate change: <span class="hlt">ice-cover</span> and terrestrial run-off shaping Arctic char and brown trout competitive asymmetries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Finstad, A. G.; Palm Helland, I.; Jonsson, B.; Forseth, T.; Foldvik, A.; Hessen, D. O.; Hendrichsen, D. K.; Berg, O. K.; Ulvan, E.; Ugedal, O.</p> <p>2011-12-01</p> <p>There has been a growing recognition that single species responses to climate change often mainly are driven by interaction with other organisms and single species studies therefore not are sufficient to recognize and project ecological climate change impacts. Here, we study how performance, relative abundance and the distribution of two common Arctic and sub-Arctic freshwater fishes (brown trout and Arctic char) are driven by competitive interactions. The interactions are modified both by direct climatic effects on temperature and <span class="hlt">ice-cover</span>, and indirectly through climate forcing of terrestrial vegetation pattern and associated carbon and nutrient run-off. We first use laboratory studies to show that Arctic char, which is the world's most northernmost distributed freshwater fish, outperform trout under low light levels and also have comparable higher growth efficiency. Corresponding to this, a combination of time series and time-for-space analyses show that <span class="hlt">ice-cover</span> duration and carbon and nutrient load mediated by catchment vegetation properties strongly affected the outcome of the competition and likely drive the species distribution pattern through competitive exclusion. In brief, while shorter <span class="hlt">ice-cover</span> period and decreased carbon load favored brown trout, increased <span class="hlt">ice-cover</span> period and increased carbon load favored Arctic char. Length of <span class="hlt">ice-covered</span> period and export of allochthonous material from catchments are major, but contrasting, climatic drivers of competitive interaction between these two freshwater lake top-predators. While projected climate change lead to decreased <span class="hlt">ice-cover</span>, corresponding increase in forest and shrub <span class="hlt">cover</span> amplify carbon and nutrient run-off. Although a likely outcome of future Arctic and sub-arctic climate scenarios are retractions of the Arctic char distribution area caused by competitive exclusion, the main drivers will act on different time scales. While <span class="hlt">ice-cover</span> will change instantaneously with increasing temperature</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050179461','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050179461"><span>Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.; Cavalieri, Donald J.</p> <p>2005-01-01</p> <p>Sea <span class="hlt">ice</span> <span class="hlt">covers</span> vast areas of the polar oceans, with <span class="hlt">ice</span> extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and <span class="hlt">ice</span> extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These <span class="hlt">ice</span> <span class="hlt">covers</span> have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea <span class="hlt">ice</span> <span class="hlt">covers</span>, and many studies suggest possible connections between the <span class="hlt">ice</span> and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased <span class="hlt">ice</span> coverage in the Arctic and increased <span class="hlt">ice</span> coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic <span class="hlt">ice</span> increases following marked decreases in the Antarctic <span class="hlt">ice</span> during the 1970s. For a detailed picture of the seasonally varying <span class="hlt">ice</span> <span class="hlt">cover</span> at the start of the 21st century, this chapter includes <span class="hlt">ice</span> concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar <span class="hlt">ice</span> <span class="hlt">covers</span> from the 1970s through 2003.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ECSS..194..205B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ECSS..194..205B"><span>Circulation and fjord-shelf exchange during the <span class="hlt">ice-covered</span> period in Young Sound-Tyrolerfjord, Northeast Greenland (74°N)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boone, W.; Rysgaard, S.; Kirillov, S.; Dmitrenko, I.; Bendtsen, J.; Mortensen, J.; Meire, L.; Petrusevich, V.; Barber, D. G.</p> <p>2017-07-01</p> <p>Fjords around Greenland connect the Greenland <span class="hlt">Ice</span> Sheet to the ocean and their hydrography and circulation are determined by the interplay between atmospheric forcing, runoff, topography, fjord-shelf exchange, tides, waves, and seasonal growth and melt of sea <span class="hlt">ice</span>. Limited knowledge exists on circulation in high-Arctic fjords, particularly those not impacted by tidewater glaciers, and especially during winter, when they are <span class="hlt">covered</span> with sea-<span class="hlt">ice</span> and freshwater input is low. Here, we present and analyze seasonal observations of circulation, hydrography and cross-sill exchange of the Young Sound-Tyrolerfjord system (74°N) in Northeast Greenland. Distinct seasonal circulation phases are identified and related to polynya activity, meltwater and inflow of coastal water masses. Renewal of basin water in the fjord is a relatively slow process that modifies the fjord water masses on a seasonal timescale. By the end of winter, there is two-layer circulation, with outflow in the upper 45 m and inflow extending down to approximately 150 m. Tidal analysis showed that tidal currents above the sill were almost barotropic and dominated by the M2 tidal constituent (0.26 m s-1), and that residual currents (∼0.02 m s-1) were relatively small during the <span class="hlt">ice-covered</span> period. Tidal pumping, a tidally driven fjord-shelf exchange mechanism, drives a salt flux that is estimated to range between 145 kg s-1 and 603 kg s-1. Extrapolation of these values over the <span class="hlt">ice-covered</span> period indicates that tidal pumping is likely a major source of dense water and driver of fjord circulation during the <span class="hlt">ice-covered</span> period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5573L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5573L"><span>Temporal variatiions of Sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Baltic Sea derived from operational sea <span class="hlt">ice</span> products used in NWP.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lange, Martin; Paul, Gerhard; Potthast, Roland</p> <p>2014-05-01</p> <p>Sea <span class="hlt">ice</span> <span class="hlt">cover</span> is a crucial parameter for surface fluxes of heat and moisture over water areas. The isolating effect and the much higher albedo strongly reduces the turbulent exchange of heat and moisture from the surface to the atmosphere and allows for cold and dry air mass flow with strong impact on the stability of the whole boundary layer and consequently cloud formation as well as precipitation in the downstream regions. Numerical weather centers as, ECMWF, MetoFrance or DWD use external products to initialize SST and sea <span class="hlt">ice</span> <span class="hlt">cover</span> in their NWP models. To the knowledge of the author there are mainly two global sea <span class="hlt">ice</span> products well established with operational availability, one from NOAA NCEP that combines measurements with satellite data, and the other from OSI-SAF derived from SSMI/S sensors. The latter one is used in the Ostia product. DWD additionally uses a regional product for the Baltic Sea provided by the national center for shipping and hydrografie which combines observations from ships (and icebreakers) for the German part of the Baltic Sea and model analysis from the hydrodynamic HIROMB model of the Swedish meteorological service for the rest of the domain. The temporal evolution of the three different products are compared for a cold period in Februar 2012. Goods and bads will be presented and suggestions for a harmonization of strong day to day jumps over large areas are suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1041493','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1041493"><span>Atmospheric Profiles, Clouds and the Evolution of Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Beaufort and Chukchi Seas: Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2017-06-04</p> <p><span class="hlt">Cover</span> in the Beaufort and Chukchi Seas: Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys Axel...of the atmospheric component of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Survey project (SIZRS). Combined with oceanographic and sea <span class="hlt">ice</span> components of...indicate cumulative probabilities. Vertical lines show median errors for forecast and climatology, respectively Figure 7 Correlation coefficient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22703237','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22703237"><span>Evidence of form II RubisCO (cbbM) in a perennially <span class="hlt">ice-covered</span> Antarctic lake.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kong, Weidong; Dolhi, Jenna M; Chiuchiolo, Amy; Priscu, John; Morgan-Kiss, Rachael M</p> <p>2012-11-01</p> <p>The permanently <span class="hlt">ice-covered</span> lakes of the McMurdo Dry Valleys, Antarctica, harbor microbially dominated food webs. These organisms are adapted to a variety of unusual environmental extremes, including low temperature, low light, and permanently stratified water columns with strong chemo- and oxy-clines. Owing to the low light levels during summer caused by thick <span class="hlt">ice</span> <span class="hlt">cover</span> as well as 6 months of darkness during the polar winter, chemolithoautotrophic microorganisms could play a key role in the production of new carbon for the lake ecosystems. We used clone library sequencing and real-time quantitative PCR of the gene encoding form II Ribulose 1, 5-bisphosphate carboxylase/oxygenase to determine spatial and seasonal changes in the chemolithoautotrophic community in Lake Bonney, a 40-m-deep lake <span class="hlt">covered</span> by c. 4 m of permanent <span class="hlt">ice</span>. Our results revealed that chemolithoautotrophs harboring the cbbM gene are restricted to layers just above the chemo- and oxi-cline (≤ 15 m) in the west lobe of Lake Bonney (WLB). Our data reveal that the WLB is inhabited by a unique chemolithoautotrophic community that resides in the suboxic layers of the lake where there are ample sources of alternative electron sources such as ammonium, reduced iron and reduced biogenic sulfur species. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.C12A..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.C12A..01A"><span>Turbulent Surface Flux Measurements over Snow-<span class="hlt">Covered</span> Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreas, E. L.; Fairall, C. W.; Grachev, A. A.; Guest, P. S.; Jordan, R. E.; Persson, P. G.</p> <p>2006-12-01</p> <p>Our group has used eddy correlation to make over 10,000 hours of measurements of the turbulent momentum and heat fluxes over snow-<span class="hlt">covered</span> sea <span class="hlt">ice</span> in both the Arctic and the Antarctic. Polar sea <span class="hlt">ice</span> is an ideal site for studying fundamental processes for turbulent exchange over snow. Both our Arctic and Antarctic sites---in the Beaufort Gyre and deep into the Weddell Sea, respectively---were expansive, flat areas with continuous snow <span class="hlt">cover</span>; and both were at least 300 km from any topography that might have complicated the atmospheric flow. In this presentation, we will review our measurements of the turbulent fluxes of momentum and sensible and latent heat. In particular, we will describe our experiences making turbulence instruments work in the fairly harsh polar, marine boundary layer. For instance, several of our Arctic sites were remote from our main camp and ran unattended for a week at a time. Besides simply making flux measurements, we have been using the data to develop a bulk flux algorithm and to study fundamental turbulence processes in the atmospheric surface layer. The bulk flux algorithm predicts the turbulent surface fluxes from mean meteorological quantities and, thus, will find use in data analyses and models. For example, components of the algorithm are already embedded in our one- dimensional mass and energy budget model SNTHERM. Our fundamental turbulence studies have included deducing new scaling regimes in the stable boundary layer; examining the Monin-Obukhov similarity functions, especially in stable stratification; and evaluating the von Kármán constant with the largest atmospheric data set ever applied to such a study. During this presentation, we will highlight some of this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GMD....10.3105P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GMD....10.3105P"><span>Sea-<span class="hlt">ice</span> evaluation of NEMO-Nordic 1.0: a NEMO-LIM3.6-<span class="hlt">based</span> ocean-sea-<span class="hlt">ice</span> model setup for the North Sea and Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pemberton, Per; Löptien, Ulrike; Hordoir, Robinson; Höglund, Anders; Schimanke, Semjon; Axell, Lars; Haapala, Jari</p> <p>2017-08-01</p> <p>The Baltic Sea is a seasonally <span class="hlt">ice-covered</span> marginal sea in northern Europe with intense wintertime ship traffic and a sensitive ecosystem. Understanding and modeling the evolution of the sea-<span class="hlt">ice</span> pack is important for climate effect studies and forecasting purposes. Here we present and evaluate the sea-<span class="hlt">ice</span> component of a new NEMO-LIM3.6-<span class="hlt">based</span> ocean-sea-<span class="hlt">ice</span> setup for the North Sea and Baltic Sea region (NEMO-Nordic). The setup includes a new depth-<span class="hlt">based</span> fast-<span class="hlt">ice</span> parametrization for the Baltic Sea. The evaluation focuses on long-term statistics, from a 45-year long hindcast, although short-term daily performance is also briefly evaluated. We show that NEMO-Nordic is well suited for simulating the mean sea-<span class="hlt">ice</span> extent, concentration, and thickness as compared to the best available observational data set. The variability of the annual maximum Baltic Sea <span class="hlt">ice</span> extent is well in line with the observations, but the 1961-2006 trend is underestimated. Capturing the correct <span class="hlt">ice</span> thickness distribution is more challenging. <span class="hlt">Based</span> on the simulated <span class="hlt">ice</span> thickness distribution we estimate the undeformed and deformed <span class="hlt">ice</span> thickness and concentration in the Baltic Sea, which compares reasonably well with observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413548D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413548D"><span>Response of <span class="hlt">ice</span> <span class="hlt">cover</span> on shallow Arctic lakes to contemporary climate conditions: Numerical modeling and remote sensing data analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duguay, C.; Surdu, C.; Brown, L.; Samuelsson, P.</p> <p>2012-04-01</p> <p>Lake <span class="hlt">ice</span> <span class="hlt">cover</span> has been shown to be a robust indicator of climate variability and change. Recent studies have demonstrated that break-up dates, in particular, have been occurring earlier in many parts of the Northern Hemisphere over the last 50 years in response to warmer climatic conditions in the winter and spring seasons. The impacts of trends in air temperature and winter precipitation over the last five decades and those projected by global climate models will affect the timing and duration of <span class="hlt">ice</span> <span class="hlt">cover</span> (and <span class="hlt">ice</span> thickness) on Arctic lakes. This will likely, in turn, have an important feedback effect on energy, water, and biogeochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that freeze to their bed in winter since thinner <span class="hlt">ice</span> <span class="hlt">covers</span> are expected to develop. Shallow lakes of the coastal plain of northern Alaska, and other similar regions of the Arctic, have likely been experiencing changes in seasonal <span class="hlt">ice</span> thickness (and phenology) over the last few decades but these have not yet been documented. This paper presents results from a numerical lake <span class="hlt">ice</span> modeling experiment and the analysis of ERS-1/2 synthetic aperture radar (SAR) data to elucidate the response of <span class="hlt">ice</span> <span class="hlt">cover</span> (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA)to climate conditions over the last three decades. New downscaled data specific for the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre regional atmospheric model (RCA4) was used to force the Canadian Lake <span class="hlt">Ice</span> Model (CLIMo) for the period 1979-2010. Output from CLIMo included freeze-up and break-up dates as well as <span class="hlt">ice</span> thickness on a daily basis. ERS-1/2 data was used to map areas of shallow lakes that freeze to bed and when this happens (timing) in winter for the period 1991</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCry....8..167S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCry....8..167S"><span>Response of <span class="hlt">ice</span> <span class="hlt">cover</span> on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950-2011): radar remote-sensing and numerical modeling data analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Surdu, C. M.; Duguay, C. R.; Brown, L. C.; Fernández Prieto, D.</p> <p>2014-01-01</p> <p>Air temperature and winter precipitation changes over the last five decades have impacted the timing, duration, and thickness of the <span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic lakes as shown by recent studies. In the case of shallow tundra lakes, many of which are less than 3 m deep, warmer climate conditions could result in thinner <span class="hlt">ice</span> <span class="hlt">covers</span> and consequently, in a smaller fraction of lakes freezing to their bed in winter. However, these changes have not yet been comprehensively documented. The analysis of a 20 yr time series of European remote sensing satellite ERS-1/2 synthetic aperture radar (SAR) data and a numerical lake <span class="hlt">ice</span> model were employed to determine the response of <span class="hlt">ice</span> <span class="hlt">cover</span> (thickness, freezing to the bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last six decades. Given the large area <span class="hlt">covered</span> by these lakes, changes in the regional climate and weather are related to regime shifts in the <span class="hlt">ice</span> <span class="hlt">cover</span> of the lakes. Analysis of available SAR data from 1991 to 2011, from a sub-region of the NSA near Barrow, shows a reduction in the fraction of lakes that freeze to the bed in late winter. This finding is in good agreement with the decrease in <span class="hlt">ice</span> thickness simulated with the Canadian Lake <span class="hlt">Ice</span> Model (CLIMo), a lower fraction of lakes frozen to the bed corresponding to a thinner <span class="hlt">ice</span> <span class="hlt">cover</span>. Observed changes of the <span class="hlt">ice</span> <span class="hlt">cover</span> show a trend toward increasing floating <span class="hlt">ice</span> fractions from 1991 to 2011, with the greatest change occurring in April, when the grounded <span class="hlt">ice</span> fraction declined by 22% (α = 0.01). Model results indicate a trend toward thinner <span class="hlt">ice</span> <span class="hlt">covers</span> by 18-22 cm (no-snow and 53% snow depth scenarios, α = 0.01) during the 1991-2011 period and by 21-38 cm (α = 0.001) from 1950 to 2011. The longer trend analysis (1950-2011) also shows a decrease in the <span class="hlt">ice</span> <span class="hlt">cover</span> duration by ~24 days consequent to later freeze-up dates by 5.9 days (α = 0.1) and earlier break-up dates by 17.7-18.6 days (α = 0.001).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/50336','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/50336"><span>Image-<span class="hlt">based</span> change estimation (<span class="hlt">ICE</span>): monitoring land use, land <span class="hlt">cover</span> and agent of change information for all lands</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Kevin Megown; Andy Lister; Paul Patterson; Tracey Frescino; Dennis Jacobs; Jeremy Webb; Nicholas Daniels; Mark Finco</p> <p>2015-01-01</p> <p>The Image-<span class="hlt">based</span> Change Estimation (<span class="hlt">ICE</span>) protocols have been designed to respond to several Agency and Department information requirements. These include provisions set forth by the 2014 Farm Bill, the Forest Service Action Plan and Strategic Plan, the 2012 Planning Rule, and the 2015 Planning Directives. <span class="hlt">ICE</span> outputs support the information needs by providing estimates...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018QSRv..181...65K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018QSRv..181...65K"><span>Constraining Quaternary <span class="hlt">ice</span> <span class="hlt">covers</span> and erosion rates using cosmogenic 26Al/10Be nuclide concentrations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knudsen, Mads Faurschou; Egholm, David Lundbek</p> <p>2018-02-01</p> <p>Paired cosmogenic nuclides are often used to constrain the exposure/burial history of landforms repeatedly <span class="hlt">covered</span> by <span class="hlt">ice</span> during the Quaternary, including tors, high-elevation surfaces, and steep alpine summits in the circum-Arctic regions. The approach generally exploits the different production rates and half-lives of 10Be and 26Al to infer past exposure/burial histories. However, the two-stage minimum-limiting exposure and burial model regularly used to interpret the nuclides ignores the effect of variable erosion rates, which potentially may bias the interpretation. In this study, we use a Monte Carlo model approach to investigate systematically how the exposure/burial and erosion history, including variable erosion and the timing of erosion events, influence concentrations of 10Be and 26Al. The results show that low 26Al/10Be ratios are not uniquely associated with prolonged burial under <span class="hlt">ice</span>, but may as well reflect <span class="hlt">ice</span> <span class="hlt">covers</span> that were limited to the coldest part of the late Pleistocene combined with recent exhumation of the sample, e.g. due to glacial plucking during the last glacial period. As an example, we simulate published 26Al/10Be data from Svalbard and show that it is possible that the steep alpine summits experienced <span class="hlt">ice</span>-free conditions during large parts of the late Pleistocene and varying amounts of glacial erosion. This scenario, which contrasts with the original interpretation of more-or-less continuous burial under non-erosive <span class="hlt">ice</span> over the last ∼1 Myr, thus challenge the conventional interpretation of such data. On the other hand, high 26Al/10Be ratios do not necessarily reflect limited burial under <span class="hlt">ice</span>, which is the common interpretation of high ratios. In fact, high 26Al/10Be ratios may also reflect extensive burial under <span class="hlt">ice</span>, combined with a change from burial under erosive <span class="hlt">ice</span>, which brought the sample close to the surface, to burial under non-erosive <span class="hlt">ice</span> at some point during the mid-Pleistocene. Importantly, by allowing for variable</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20140008940&hterms=parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dparkinson','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20140008940&hterms=parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dparkinson"><span>On the 2012 Record Low Arctic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span>: Combined Impact of Preconditioning and an August Storm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.; Comiso, Josefino C.</p> <p>2013-01-01</p> <p>A new record low Arctic sea <span class="hlt">ice</span> extent for the satellite era, 3.4 x 10(exp 6) square kilometers, was reached on 13 September 2012; and a new record low sea <span class="hlt">ice</span> area, 3.01 x 10(exp 6) square kilometers was reached on the same date. Preconditioning through decades of overall <span class="hlt">ice</span> reductions made the <span class="hlt">ice</span> pack more vulnerable to a strong storm that entered the central Arctic in early August 2012. The storm caused the separation of an expanse of 0.4 x 10(exp 6) square kilometers of <span class="hlt">ice</span> that melted in total, while its removal left the main pack more exposed to wind and waves, facilitating the main pack's further decay. Future summer storms could lead to a further acceleration of the decline in the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> and should be carefully monitored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601202','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601202"><span>Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys Coordination</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>of SIZRS are <span class="hlt">covered</span> in separate reports. Our long-term goal is to track and understand the interplay among the <span class="hlt">ice</span>, atmosphere, and ocean...OMB control number. 1. REPORT DATE 30 SEP 2013 2. REPORT TYPE 3. DATES <span class="hlt">COVERED</span> 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Seasonal <span class="hlt">Ice</span> Zone...sensing resources include MODIS visible and IR imagery, NSIDC <span class="hlt">ice</span> extent charts <span class="hlt">based</span> on a composite of passive microwave products (http://nsidc.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817868T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817868T"><span>Life under <span class="hlt">ice</span>: Investigating microbial-related biogeochemical cycles in the seasonally-<span class="hlt">covered</span> Great Lake Onego, Russia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, Camille; Ariztegui, Daniel; Victor, Frossard; Emilie, Lyautey; Marie-Elodie, Perga; Life Under Ice Scientific Team</p> <p>2016-04-01</p> <p> were also quantified in both sediment and water column. Preliminary results show that in the sediment, methanogenesis occurs below 7 cm. Above this redox boundary, methanotrophs are abundant but there activity remains enigmatic (10000 times less transcript than gene copies). <span class="hlt">Based</span> on 16S rRNA transcripts, Bacteria and Archaea seem to have their maximum activity within the first 7 cm. These data are validated by ATP measurements. The principal peaks of activity actually lie at the water sediment interface, and at the redox boundary (7cm). High-throughput sequencing of 16S rRNA genes (both from DNA and RNA) are currently being performed to gain further understanding on the main actors of these microbial processes in the sediment. Diversity analysis are also being prepared and will allow to characterize the relationship between planktonic and benthic communities in the <span class="hlt">ice-covered</span> lake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790056630&hterms=interplay&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinterplay','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790056630&hterms=interplay&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinterplay"><span>Evolution of Martian polar landscapes - Interplay of long-term variations in perennial <span class="hlt">ice</span> <span class="hlt">cover</span> and dust storm intensity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cutts, J. A.; Blasius, K. R.; Roberts, W. J.</p> <p>1979-01-01</p> <p>The discovery of a new type of Martian polar terrain, called undulating plain, is reported and the evolution of the plains and other areas of the Martian polar region is discussed in terms of the trapping of dust by the perennial <span class="hlt">ice</span> <span class="hlt">cover</span>. High-resolution Viking Orbiter 2 observations of the north polar terrain reveal perennially <span class="hlt">ice-covered</span> surfaces with low relief, wavelike, regularly spaced, parallel ridges and troughs (undulating plains) occupying areas of the polar terrain previously thought to be flat, and associated with troughs of considerable local relief which exhibit at least partial annual melting. It is proposed that the wavelike topography of the undulating plains originates from long-term periodic variations in cyclical dust precipitation at the margin of a growing or receding perennial polar cap in response to changes in insolation. The troughs are proposed to originate from areas of steep slope in the undulating terrain which have lost their perennial <span class="hlt">ice</span> <span class="hlt">cover</span> and have become incapable of trapping dust. The polar landscape thus appears to record the migrations, expansions and contractions of the Martian polar cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27250161','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27250161"><span>Elastic parabolic equation and normal mode solutions for seismo-acoustic propagation in underwater environments with <span class="hlt">ice</span> <span class="hlt">covers</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Collis, Jon M; Frank, Scott D; Metzler, Adam M; Preston, Kimberly S</p> <p>2016-05-01</p> <p>Sound propagation predictions for <span class="hlt">ice-covered</span> ocean acoustic environments do not match observational data: received levels in nature are less than expected, suggesting that the effects of the <span class="hlt">ice</span> are substantial. Effects due to elasticity in overlying <span class="hlt">ice</span> can be significant enough that low-shear approximations, such as effective complex density treatments, may not be appropriate. Building on recent elastic seafloor modeling developments, a range-dependent parabolic equation solution that treats the <span class="hlt">ice</span> as an elastic medium is presented. The solution is benchmarked against a derived elastic normal mode solution for range-independent underwater acoustic propagation. Results from both solutions accurately predict plate flexural modes that propagate in the <span class="hlt">ice</span> layer, as well as Scholte interface waves that propagate at the boundary between the water and the seafloor. The parabolic equation solution is used to model a scenario with range-dependent <span class="hlt">ice</span> thickness and a water sound speed profile similar to those observed during the 2009 <span class="hlt">Ice</span> Exercise (ICEX) in the Beaufort Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IzAOP..51..929R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IzAOP..51..929R"><span>Peculiarities of stochastic regime of Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> time evolution over 1987-2014 from microwave satellite sounding on the basis of NASA team 2 algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raev, M. D.; Sharkov, E. A.; Tikhonov, V. V.; Repina, I. A.; Komarova, N. Yu.</p> <p>2015-12-01</p> <p>The GLOBAL-RT database (DB) is composed of long-term radio heat multichannel observation data received from DMSP F08-F17 satellites; it is permanently supplemented with new data on the Earth's exploration from the space department of the Space Research Institute, Russian Academy of Sciences. Arctic <span class="hlt">ice-cover</span> areas for regions higher than 60° N latitude were calculated using the DB polar version and NASA Team 2 algorithm, which is widely used in foreign scientific literature. According to the analysis of variability of Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> during 1987-2014, 2 months were selected when the Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> was maximal (February) and minimal (September), and the average <span class="hlt">ice</span> <span class="hlt">cover</span> area was calculated for these months. Confidence intervals of the average values are in the 95-98% limits. Several approximations are derived for the time dependences of the <span class="hlt">ice-cover</span> maximum and minimum over the period under study. Regression dependences were calculated for polynomials from the first degree (linear) to sextic. It was ascertained that the minimal root-mean-square error of deviation from the approximated curve sharply decreased for the biquadratic polynomial and then varied insignificantly: from 0.5593 for the polynomial of third degree to 0.4560 for the biquadratic polynomial. Hence, the commonly used strictly linear regression with a negative time gradient for the September Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> minimum over 30 years should be considered incorrect.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013TCD.....7.3783S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013TCD.....7.3783S"><span>Response of <span class="hlt">ice</span> <span class="hlt">cover</span> on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950-2011): radar remote sensing and numerical modeling data analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Surdu, C. M.; Duguay, C. R.; Brown, L. C.; Fernández Prieto, D.</p> <p>2013-07-01</p> <p>Air temperature and winter precipitation changes over the last five decades have impacted the timing, duration, and thickness of the <span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic lakes as shown by recent studies. In the case of shallow tundra lakes, many of which are less than 3 m deep, warmer climate conditions could result in thinner <span class="hlt">ice</span> <span class="hlt">covers</span> and consequently, to a smaller fraction of lakes freezing to their bed in winter. However, these changes have not yet been comprehensively documented. The analysis of a 20 yr time series of ERS-1/2 synthetic aperture radar (SAR) data and a numerical lake <span class="hlt">ice</span> model were employed to determine the response of <span class="hlt">ice</span> <span class="hlt">cover</span> (thickness, freezing to the bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last six decades. Analysis of available SAR data from 1991-2011, from a sub-region of the NSA near Barrow, shows a reduction in the fraction of lakes that freeze to the bed in late winter. This finding is in good agreement with the decrease in <span class="hlt">ice</span> thickness simulated with the Canadian Lake <span class="hlt">Ice</span> Model (CLIMo), a lower fraction of lakes frozen to the bed corresponding to a thinner <span class="hlt">ice</span> <span class="hlt">cover</span>. Observed changes of the <span class="hlt">ice</span> <span class="hlt">cover</span> show a trend toward increasing floating <span class="hlt">ice</span> fractions from 1991 to 2011, with the greatest change occurring in April, when the grounded <span class="hlt">ice</span> fraction declined by 22% (α = 0.01). Model results indicate a trend toward thinner <span class="hlt">ice</span> <span class="hlt">covers</span> by 18-22 cm (no-snow and 53% snow depth scenarios, α = 0.01) during the 1991-2011 period and by 21-38 cm (α = 0.001) from 1950-2011. The longer trend analysis (1950-2011) also shows a decrease in the <span class="hlt">ice</span> <span class="hlt">cover</span> duration by ∼24 days consequent to later freeze-up dates by 5.9 days (α = 0.1) and earlier break-up dates by 17.7-18.6 days (α = 0.001).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P52B..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P52B..01G"><span>Small Moves, NUI. Small Moves: Beginning to Investigate Biogeochemical Exchange From the Seafloor to the Exterior of an <span class="hlt">Ice-Covered</span> Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>German, C. R.; Boetius, A.</p> <p>2017-12-01</p> <p>We present results from two recent cruises, using the new Nereid Under <span class="hlt">Ice</span> (NUI) vehicle aboard the FS Polarstern, in which we investigated biogeochemical fluxes from the deep seafloor of the Gakkel Ridge, an ultraslow spreading ridge that spans the <span class="hlt">ice-covered</span> Arctic Ocean, and the mechanisms by which biogeochemical signals might be transferred from within the underlying ocean to the overlying Arctic <span class="hlt">ice</span>. The scientific advances for this work progress hand in hand with technological capability. During a first cruise in 2014, our NUI-<span class="hlt">based</span> investigations focused on photosynthetically-driven biogeochemical cycling in the uppermost water column and how to study such processes using in situ sensing immediately at and beneath the rough topography of the overlying <span class="hlt">ice-cover</span>. For that work we relied entirely upon human-in-the-loop control of the vehicle via a single optical fiber light tether than provided real-time monitoring and control of the vehicle as it ranged laterally out under the <span class="hlt">ice</span> up to 1km distant from the ship, conducting physical, geochemical and biological surveys. Instrumentation used for that work included multibeam mapping and imaging (digital still photographs and HD video), in situ spectroscopy to study light transmission through the <span class="hlt">ice</span> and biogeochemical mapping of the ocean water column using a combination of CTD sensing, fluorometry and an in situ nitrate analyzer. Returning to the Arctic in 2016 we extended our exploration modes with NUI further, investigating for seafloor fluid flow at a shallow setting on the flanks of the Gakkel Ridge where the seabed rises from >4000m to <600m depth. In AUV mode, NUI conducted water column sensing using CTD, optical backscatter and Eh sensors and seafloor surveys using high resolution multibeam bathymetry and stereoscopic seafloor imaging. In subsequent ROV operations, NUI was used to conduct detailed investigation of seabed biological communities. This included targeted sampling of individual organisms and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC51F1065F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC51F1065F"><span>Trends in Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span>, Sea Surface Temperature, and Chlorophyll Biomass Across a Marine Distributed Biological Observatory in the Pacific Arctic Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frey, K. E.; Grebmeier, J. M.; Cooper, L. W.; Wood, C.; Panday, P. K.</p> <p>2011-12-01</p> <p>The northern Bering and Chukchi Seas in the Pacific Arctic Region (PAR) are among the most productive marine ecosystems in the world and act as important carbon sinks, particularly during May and June when seasonal sea <span class="hlt">ice</span>-associated phytoplankton blooms occur throughout the region. Recent dramatic shifts in seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> across the PAR should have profound consequences for this seasonal phytoplankton production as well as the intimately linked higher trophic levels. In order to investigate ecosystem responses to these observed recent shifts in sea <span class="hlt">ice</span> <span class="hlt">cover</span>, the development of a prototype Distributed Biological Observatory (DBO) is now underway in the PAR. The DBO is being developed as an internationally-coordinated change detection array that allows for consistent sampling and monitoring at five spatially explicit biologically productive locations across a latitudinal gradient: (1) DBO-SLP (south of St. Lawrence Island (SLI)), (2) DBO-NBS (north of SLI), (3) DBO-SCS (southern Chukchi Sea), (4) DBO-CCS (central Chukchi Sea), and (5) DBO-BCA (Barrow Canyon Arc). Standardized measurements at many of the DBO sites were made by multiple research cruises during the 2010 and 2011 pilot years, and will be expanded with the development of the DBO in coming years. In order to provide longer-term context for the changes occurring across the PAR, we utilize multi-sensor satellite data to investigate recent trends in sea <span class="hlt">ice</span> <span class="hlt">cover</span>, chlorophyll biomass, and sea surface temperatures for each of the five DBO sites, as well as a sixth long-term observational site in the Bering Strait. Satellite observations show that over the past three decades, trends in sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the PAR have been heterogeneous, with significant declines in the Chukchi Sea, slight declines in the Bering Strait region, but increases in the northern Bering Sea south of SLI. Declines in the persistence of seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Chukchi Sea and Bering Strait region are due to both earlier sea</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601318','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601318"><span>Atmospheric Profiles, Clouds, and the Evolution of Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Beaufort and Chukchi Seas Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-09-30</p> <p><span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Beaufort and Chukchi Seas Atmospheric Observations and Modeling as Part of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Surveys Axel...temperatures. These changes in turn will affect the evolution of the SIZ. An appropriate representation of this feedback loop in models is critical if we... modeling experiments as part of the atmospheric component of the Seasonal <span class="hlt">Ice</span> Zone Reconnaissance Survey project (SIZRS). We will • Determine the role</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/42670','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/42670"><span>Image-<span class="hlt">based</span> change estimation for land <span class="hlt">cover</span> and land use monitoring</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Jeremy Webb; C. Kenneth Brewer; Nicholas Daniels; Chris Maderia; Randy Hamilton; Mark Finco; Kevin A. Megown; Andrew J. Lister</p> <p>2012-01-01</p> <p>The Image-<span class="hlt">based</span> Change Estimation (<span class="hlt">ICE</span>) project resulted from the need to provide estimates and information for land <span class="hlt">cover</span> and land use change over large areas. The procedure uses Forest Inventory and Analysis (FIA) plot locations interpreted using two different dates of imagery from the National Agriculture Imagery Program (NAIP). In order to determine a suitable...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18804261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18804261"><span>SPME-GCMS study of the natural attenuation of aviation diesel spilled on the perennial <span class="hlt">ice</span> <span class="hlt">cover</span> of Lake Fryxell, Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jaraula, Caroline M B; Kenig, Fabien; Doran, Peter T; Priscu, John C; Welch, Kathleen A</p> <p>2008-12-15</p> <p>In January 2003, a helicopter crashed on the 5 m thick perennial <span class="hlt">ice</span> <span class="hlt">cover</span> of Lake Fryxell (McMurdo Dry Valleys, East Antarctica), spilling approximately 730 l of aviation diesel fuel (JP5-AN8 mixture). The molecular composition of the initial fuel was analyzed by solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS), then compared to the composition of the contaminated <span class="hlt">ice</span>, water, and sediments collected a year after the spill. Evaporation is the major agent of diesel weathering in meltpool waters and in the <span class="hlt">ice</span>. This process is facilitated by the light non-aqueous phase liquid properties of the aviation diesel and by the net upward movement of the <span class="hlt">ice</span> as a result of ablation. In contrast, in sediment-bearing <span class="hlt">ice</span>, biodegradation by both alkane- and aromatic-degraders was the prominent attenuation mechanism. The composition of the diesel contaminant in the <span class="hlt">ice</span> was also affected by the differential solubility of its constituents, some <span class="hlt">ice</span> containing water-washed diesel and some <span class="hlt">ice</span> containing exclusively relatively soluble low molecular weight aromatic hydrocarbons such as alkylbenzene and naphthalene homologues. The extent of evaporation, water washing and biodegradation between sites and at different depths in the <span class="hlt">ice</span> are evaluated on the basis of molecular ratios and the results of JP5-AN8 diesel evaporation experiment at 4 degrees C. Immediate spread of the aviation diesel was enhanced where the presence of aeolian sediments induced formations of meltpools. However, in absence of melt pools, slow spreading of the diesel is possible through the porous <span class="hlt">ice</span> and the <span class="hlt">ice</span> <span class="hlt">cover</span> aquifer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4469S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4469S"><span>Pliocene-Pleistocene changes in Arctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span>: New biomarker records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, Ruediger; Fahl, Kirsten</p> <p>2013-04-01</p> <p>Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-<span class="hlt">ice</span> conditions was developed and is <span class="hlt">based</span> on the determination of a highly branched isoprenoid with 25 carbons (IP25; Belt et al., 2007). Following this pioneer IP25 study by Belt and colleagues, several IP25 studies of marine surface sediments and sediment cores as well as sediment trap samples from northpolar areas were carried out successfully and allowed detailed reconstruction of modern and late Quaternary sea <span class="hlt">ice</span> variability in these regions (e.g., Massé et al., 2008; Müller et al., 2009, 2011; Vare et al., 2009; Belt et al., 2010; Fahl and Stein, 2012; for review see Stein et al., 2012). Here, we present new (low-resolution) biomarker records from Ocean Drilling Program (ODP) Sites 911 and 912, representing the Pliocene-Pleistocene time interval (including the interval of major intensification of Northern Hemisphere Glaciation near 2.7 Ma). These data indicate that sea <span class="hlt">ice</span> of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. In general, an increase in sea-<span class="hlt">ice</span> <span class="hlt">cover</span> seems to correlate with phases of extended late Pliocene-Pleistocene continental <span class="hlt">ice</span>-sheets. At ODP Site 912, a significant increase in sea-<span class="hlt">ice</span> extension occurred near 1.2 Ma (Stein and Fahl, 2012). Furthermore, our data support the idea that a combination of IP25 and open water, phytoplankton biomarker data ("PIP25 index"; Müller et al., 2011) may give more reliable and quantitative estimates of past sea-<span class="hlt">ice</span> <span class="hlt">cover</span> (at least for the study area). This study reveals that the novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea <span class="hlt">ice</span> studies <span class="hlt">covering</span> the entire Quaternary and motivate to carry out further detailed high-resolution research on ODP/IODP material using this proxy. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea <span class="hlt">ice</span>: IP25</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C41B0559S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C41B0559S"><span>Impact of Arctic sea-<span class="hlt">ice</span> retreat on the recent change in cloud-<span class="hlt">base</span> height during autumn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sato, K.; Inoue, J.; Kodama, Y.; Overland, J. E.</p> <p>2012-12-01</p> <p>Cloud-<span class="hlt">base</span> observations over the <span class="hlt">ice</span>-free Chukchi and Beaufort Seas in autumn were conducted using a shipboard ceilometer and radiosondes during the 1999-2010 cruises of the Japanese R/V Mirai. To understand the recent change in cloud <span class="hlt">base</span> height over the Arctic Ocean, these cloud-<span class="hlt">base</span> height data were compared with the observation data under <span class="hlt">ice-covered</span> situation during SHEBA (the Surface Heat Budget of the Arctic Ocean project in 1998). Our <span class="hlt">ice</span>-free results showed a 30 % decrease (increase) in the frequency of low clouds with a ceiling below (above) 500 m. Temperature profiles revealed that the boundary layer was well developed over the <span class="hlt">ice</span>-free ocean in the 2000s, whereas a stable layer dominated during the <span class="hlt">ice-covered</span> period in 1998. The change in surface boundary conditions likely resulted in the difference in cloud-<span class="hlt">base</span> height, although it had little impact on air temperatures in the mid- and upper troposphere. Data from the 2010 R/V Mirai cruise were investigated in detail in terms of air-sea temperature difference. This suggests that stratus cloud over the sea <span class="hlt">ice</span> has been replaced as stratocumulus clouds with low cloud fraction due to the decrease in static stability induced by the sea-<span class="hlt">ice</span> retreat. The relationship between cloud-<span class="hlt">base</span> height and air-sea temperature difference (SST-Ts) was analyzed in detail using special section data during 2010 cruise data. Stratus clouds near the sea surface were predominant under a warm advection situation, whereas stratocumulus clouds with a cloud-free layer were significant under a cold advection situation. The threshold temperature difference between sea surface and air temperatures for distinguishing the dominant cloud types was 3 K. Anomalous upward turbulent heat fluxes associated with the sea-<span class="hlt">ice</span> retreat have likely contributed to warming of the lower troposphere. Frequency distribution of the cloud-<span class="hlt">base</span> height (km) detected by a ceilometer/lidar (black bars) and radiosondes (gray bars), and profiles of potential</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS13H..02E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS13H..02E"><span>Sea-<span class="hlt">ice</span> information co-management: Planning for sustainable multiple uses of <span class="hlt">ice-covered</span> seas in a rapidly changing Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eicken, H.; Lovecraft, A. L.</p> <p>2012-12-01</p> <p>A thinner, less extensive and more mobile summer sea-<span class="hlt">ice</span> <span class="hlt">cover</span> is a major element and driver of Arctic Ocean change. Declining summer sea <span class="hlt">ice</span> presents Arctic stakeholders with substantial challenges and opportunities from the perspective of sustainable ocean use and derivation of sea-<span class="hlt">ice</span> or ecosystem services. Sea-<span class="hlt">ice</span> use by people and wildlife as well as its role as a major environmental hazard focuses the interests and concerns of indigenous hunters and Arctic coastal communities, resource managers and the maritime industry. In particular, rapid sea-<span class="hlt">ice</span> change and intensifying offshore industrial activities have raised fundamental questions as to how best to plan for and manage multiple and increasingly overlapping ocean and sea <span class="hlt">ice</span> uses. The western North American Arctic - a region that has seen some of the greatest changes in <span class="hlt">ice</span> and ocean conditions in the past three decades anywhere in the North - is the focus of our study. Specifically, we examine the important role that relevant and actionable sea-<span class="hlt">ice</span> information can play in allowing stakeholders to evaluate risks and reconcile overlapping and potentially competing interests. Our work in coastal Alaska suggests that important prerequisites to address such challenges are common values, complementary bodies of expertise (e.g., local or indigenous knowledge, engineering expertise, environmental science) and a forum for the implementation and evaluation of a sea-<span class="hlt">ice</span> data and information framework. Alongside the International Polar Year 2007-08 and an associated boost in Arctic Ocean observation programs and platforms, there has been a movement towards new governance bodies that have these qualities and can play a central role in guiding the design and optimization of Arctic observing systems. To help further the development of such forums an evaluation of the density and spatial distribution of institutions, i.e., rule sets that govern ocean use, as well as the use of scenario planning and analysis can serve as</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C23C1234W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C23C1234W"><span>Moat Development and Evolution on a Perennialy <span class="hlt">Ice-Covered</span> Lake in East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wayt, M. E.; Myers, K. F.; Doran, P.</p> <p>2017-12-01</p> <p>Lake Fryxell is a closed basin lake located in the lower end of Taylor Valley in McMurdo Dry Valleys of east Antarctica. The lake has an 4 m thick perennial <span class="hlt">ice-cover</span>, however during the austral summers an <span class="hlt">ice</span>-free moat forms around the lake margin due to increased temperatures and stream run off. Satellite imagery paired with ground-<span class="hlt">based</span> camera data from Lake Fryxell were used to determine onset of moat formation, moat duration, and total area of open water at peak formation from 2009 through 2015. Temperature data from a meteorological station on the shore of Lake Fryxell were used to correlate degree days above freezing (DDAF) with moat formation and extent. The results showed that overall, the moat was smallest in 2009-10, accounting for roughly .61% percent of the surface area of Lake Fryxell. In 2010-11 and 2011-12 moat extent increase by roughly 1% and then decreased by 4% in 2012-13. In 2013-14 the moat was at its largest, accounting for about 11% with a decrease in area of 6% the following summer. Preliminary analysis of temperature data suggest a correlation between DDAF and moat extent. Moats make up on average 9% of lake area and are likely sites of elevated primary productivity in the summer. Moats are <span class="hlt">ice</span> free which allows for unobstructed photosynthetically active radiation to penetrate the shallow water column. We hypothesize projected increases in air temperatures will lead to continued rise in lake level and larger moat areas, making it critical to understand these delicate and rapidly changing ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11F..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11F..05G"><span>Microwave Observations of Snow-<span class="hlt">Covered</span> Freshwater Lake <span class="hlt">Ice</span> obtained during the Great Lakes Winter EXperiment (GLAWEX), 2017</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunn, G. E.; Hall, D. K.; Nghiem, S. V.</p> <p>2017-12-01</p> <p>Studies observing lake <span class="hlt">ice</span> using active microwave acquisitions suggest that the dominant scattering mechanism in <span class="hlt">ice</span> is caused by double-bounce of the signal off vertical tubular bubble inclusions. Recent polarimetric SAR observations and target decomposition algorithms indicate single-bounce interactions may be the dominant source of returns, and in the absence of field observations, has been hypothesized to be the result of roughness at the <span class="hlt">ice</span>-water interface on the order of incident wavelengths. This study presents in-situ physical observations of snow-<span class="hlt">covered</span> lake <span class="hlt">ice</span> in western Michigan and Wisconsin acquired during the Great Lakes Winter EXperiment in 2017 (GLAWEX'17). In conjunction with NASA's SnowEx airborne snow campaign in Colorado (http://snow.nasa.gov), C- (Sentinel-1, RADARSAT-2) and X-band (TerraSAR-X) synthetic aperture radar (SAR) observations were acquired coincidently to surface physical snow and <span class="hlt">ice</span> observations. Small/large scale roughness features at the <span class="hlt">ice</span>-water interface are quantified through auger transects and used as an input variable in lake <span class="hlt">ice</span> backscatter models to assess the relative contributions from different scattering mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B"><span>Quantifying <span class="hlt">ice</span> cliff contribution to debris-<span class="hlt">covered</span> glacier mass balance from multiple sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brun, Fanny; Wagnon, Patrick; Berthier, Etienne; Kraaijenbrink, Philip; Immerzeel, Walter; Shea, Joseph; Vincent, Christian</p> <p>2017-04-01</p> <p><span class="hlt">Ice</span> cliffs on debris-<span class="hlt">covered</span> glaciers have been recognized as a hot spot for glacier melt. <span class="hlt">Ice</span> cliffs are steep (even sometimes overhanging) and fast evolving surface features, which make them challenging to monitor. We surveyed the topography of Changri Nup Glacier (Nepalese Himalayas, Everest region) in November 2015 and 2016 using multiple sensors: terrestrial photogrammetry, Unmanned Aerial Vehicle (UAV) photogrammetry, Pléiades stereo images and ASTER stereo images. We derived 3D point clouds and digital elevation models (DEMs) following a Structure-from-Motion (SfM) workflow for the first two sets of data to monitor surface elevation changes and calculate the associated volume loss. We derived only DEMs for the two last data sets. The derived DEMs had resolutions ranging from < 5 cm to 30 m. The derived point clouds and DEMs are used to quantify the <span class="hlt">ice</span> melt of the cliffs at different scales. The very high resolution SfM point clouds, together with the surface velocity field, will be used to calculate the volume losses of 14 individual cliffs, depending on their size, aspect or the presence of supra glacial lake. Then we will extend this analysis to the whole glacier to quantify the contribution of <span class="hlt">ice</span> cliff melt to the overall glacier mass balance, calculated with the UAV and Pléiades DEMs. This research will provide important tools to evaluate the role of <span class="hlt">ice</span> cliffs in regional mass loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA124508','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA124508"><span>Reservoir Bank Erosion Caused and Influenced by <span class="hlt">Ice</span> <span class="hlt">Cover</span>.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1982-12-01</p> <p>8 8. Bank sediment deposited on shorefast <span class="hlt">ice</span> ------------ 9 9. Sediment frozen to the bottom of <span class="hlt">ice</span> laid down onto the reservoir bed...end of November 1979 during a storm with 45-mph northwesterly winds-- 17 16. <span class="hlt">Ice</span> and shore sediment uplifted where an <span class="hlt">ice</span> pres- sure ridge intersects...restarts at breakup when the <span class="hlt">ice</span> becomes mobile; the <span class="hlt">ice</span> scrapes, shoves and scours the shore or bank, and transports sediment away. Figure 1. Narrow zone</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C13A0603O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C13A0603O"><span>Spatial Heterogeneity of <span class="hlt">Ice</span> <span class="hlt">Cover</span> Sediment and Thickness and Its Effects on Photosynthetically Active Radiation and Chlorophyll-a Distribution: Lake Bonney, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Obryk, M.; Doran, P. T.; Priscu, J. C.; Morgan-Kiss, R. M.; Siebenaler, A. G.</p> <p>2012-12-01</p> <p>The perennially <span class="hlt">ice-covered</span> lakes in the McMurdo Dry Valleys, Antarctica have been extensively studied under the Long Term Ecological Research project. But sampling has been spatially restricted due to the logistical difficulty of penetrating the 3-6 m of <span class="hlt">ice</span> <span class="hlt">cover</span>. The <span class="hlt">ice</span> <span class="hlt">covers</span> restrict wind-driven turbulence and its associated mixing of water, resulting in a unique thermal stratification and a strong vertical gradient of salinity. The permanent <span class="hlt">ice</span> <span class="hlt">covers</span> also shade the underlying water column, which, in turn, controls photosynthesis. Here, we present results of a three-dimensional record of lake processes obtained with an autonomous underwater vehicle (AUV). The AUV was deployed at West Lake Bonney, located in Taylor Valley, Dry Valleys, to further understand biogeochemical and physical properties of the Dry Valley lakes. The AUV was equipped with depth, conductivity, temperature, under water photosynthetically active radiation (PAR), turbidity, chlorophyll-and-DOM fluorescence, pH, and REDOX sensors. Measurements were taken over the course of two years in a 100 x 100 meter spaced horizontal sampling grid (and 0.2 m vertical resolution). In addition, the AUV measured <span class="hlt">ice</span> thickness and collected 200 images looking up through the <span class="hlt">ice</span>, which were used to quantify sediment distribution. Comparison with high-resolution satellite QuickBird imagery demonstrates a strong correlation between aerial sediment distribution and <span class="hlt">ice</span> <span class="hlt">cover</span> thickness. Our results are the first to show the spatial heterogeneity of lacustrine ecosystems in the McMurdo Dry Valleys, significantly improving our understanding of lake processes. Surface sediment is responsible for localized thinning of <span class="hlt">ice</span> <span class="hlt">cover</span> due to absorption of solar radiation, which in turn increases total available PAR in the water column. Higher PAR values are negatively correlated with chlorophyll-a, presenting a paradox; historically, long-term studies of PAR and chlorophyll-a have shown positive trends. We hypothesized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R"><span>Modelling the feedbacks between mass balance, <span class="hlt">ice</span> flow and debris transport to predict the response to climate change of debris-<span class="hlt">covered</span> glaciers in the Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.</p> <p>2015-11-01</p> <p>Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-<span class="hlt">ice</span> surfaces. Debris-<span class="hlt">covered</span> glaciers can persist well below the altitude that would be sustainable for clean-<span class="hlt">ice</span> glaciers, resulting in much longer timescales of mass loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-<span class="hlt">ice</span> surfaces, and yield conflicting results. We developed a numerical model that couples the flow of <span class="hlt">ice</span> and debris and includes important feedbacks between debris accumulation and glacier mass balance. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-<span class="hlt">covered</span> Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ, concealing the magnitude of mass loss when compared with estimates <span class="hlt">based</span> on glacierised area. Since the Little <span class="hlt">Ice</span> Age, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a decrease in glacier volume of 8-10% by AD2100, accompanied by dynamic and physical detachment of the debris-<span class="hlt">covered</span> tongue from the active glacier within the next 150 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-<span class="hlt">covered</span> glaciers in the Himalaya.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.1156R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.1156R"><span>Thin Sea <span class="hlt">Ice</span>, Thick Snow, and Widespread Negative Freeboard Observed During N-<span class="hlt">ICE</span>2015 North of Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rösel, Anja; Itkin, Polona; King, Jennifer; Divine, Dmitry; Wang, Caixin; Granskog, Mats A.; Krumpen, Thomas; Gerland, Sebastian</p> <p>2018-02-01</p> <p>In recent years, sea-<span class="hlt">ice</span> conditions in the Arctic Ocean changed substantially toward a younger and thinner sea-<span class="hlt">ice</span> <span class="hlt">cover</span>. To capture the scope of these changes and identify the differences between individual regions, in situ observations from expeditions are a valuable data source. We present a continuous time series of in situ measurements from the N-<span class="hlt">ICE</span>2015 expedition from January to June 2015 in the Arctic Basin north of Svalbard, comprising snow buoy and <span class="hlt">ice</span> mass balance buoy data and local and regional data gained from electromagnetic induction (EM) surveys and snow probe measurements from four distinct drifts. The observed mean snow depth of 0.53 m for April to early June is 73% above the average value of 0.30 m from historical and recent observations in this region, <span class="hlt">covering</span> the years 1955-2017. The modal total <span class="hlt">ice</span> and snow thicknesses, of 1.6 and 1.7 m measured with ground-<span class="hlt">based</span> EM and airborne EM measurements in April, May, and June 2015, respectively, lie below the values ranging from 1.8 to 2.7 m, reported in historical observations from the same region and time of year. The thick snow <span class="hlt">cover</span> slows thermodynamic growth of the underlying sea <span class="hlt">ice</span>. In combination with a thin sea-<span class="hlt">ice</span> <span class="hlt">cover</span> this leads to an imbalance between snow and <span class="hlt">ice</span> thickness, which causes widespread negative freeboard with subsequent flooding and a potential for snow-<span class="hlt">ice</span> formation. With certainty, 29% of randomly located drill holes on level <span class="hlt">ice</span> had negative freeboard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP33A2293H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP33A2293H"><span>Sea <span class="hlt">ice</span> <span class="hlt">cover</span> variability and river run-off in the western Laptev Sea (Arctic Ocean) since the last 18 ka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.</p> <p>2015-12-01</p> <p>Multi-proxy biomarker measurements were performed on two sediment cores (PS51/154, PS51/159) with the objective reconstructing sea <span class="hlt">ice</span> <span class="hlt">cover</span> (IP25, brassicasterol, dinosterol) and river-runoff (campesterol, β-sitosterol) in the western Laptev Sea over the last 18 ka with unprecedented temporal resolution. The sea <span class="hlt">ice</span> <span class="hlt">cover</span> varies distinctly during the whole time period. The absence of IP25 during 18 and 16 ka indicate that the western Laptev Sea was mostly <span class="hlt">covered</span> with permanent sea <span class="hlt">ice</span> (pack <span class="hlt">ice</span>). However, a period of temporary break-up of the permanent <span class="hlt">ice</span> coverage occurred at c. 17.2 ka (presence of IP25). Very little river-runoff occurred during this interval. Decreasing terrigenous (riverine) input and synchronous increase of marine produced organic matter around 16 ka until 7.5 ka indicate the gradual establishment of a marine environment in the western Laptev Sea related to the onset of the post-glacial transgression of the shelf. Strong river run-off and reduced sea <span class="hlt">ice</span> <span class="hlt">cover</span> characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7 - 12.9 ka). Moreover, the DIP25 Index (ratio of HBI-dienes and IP25) might document the presence of Atlantic derived water at the western Laptev Sea shelf area. A sudden return to severe sea <span class="hlt">ice</span> conditions occurred during the Younger Dryas (12.9 - 11.6 ka). This abrupt climate change was observed in the whole circum-Arctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (deep drop in terrigenous and phytoplankton biomarkers) may document the entry of a giant freshwater plume, possibly relating to the Lake Agassiz outburst at 13 ka. IP25 concentrations increase and higher values of the PIP25 Index during the last 7 ka reflect a cooling of the Laptev Sea spring season. Moreover, a short-term variability of c. 1.5 thousand years occurred during the last 12 ka, most probably following Bond Cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6895S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6895S"><span>Late Pliocene/Pleistocene changes in Arctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span>: Biomarker and dinoflagellate records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens</p> <p>2014-05-01</p> <p>Sea <span class="hlt">ice</span> is a critical component in the (global) climate system that contributes to changes in the Earth's albedo (heat reduction) and biological processes (primary productivity), as well as deep-water formation, a driving mechanism for global thermohaline circulation. Thus, understanding the processes controlling Arctic sea <span class="hlt">ice</span> variability is of overall interest and significance. Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-<span class="hlt">ice</span> conditions was developed and is <span class="hlt">based</span> on the determination of a highly-branched isoprenoid with 25 carbons (IP25; Belt et al., 2007; PIP25 when combined with open-water phytoplankton biomarkers; Müller et al., 2011). Here, we present biomarker data from Ocean Drilling Program (ODP) Sites 911 and 912, recovered from the southern Yermak Plateau and representing information of sea-<span class="hlt">ice</span> variability, changes in primary productivity and terrigenous input during the last about 3.5 Ma. As Sites 911 and 912 are close to the modern sea-<span class="hlt">ice</span> edge, their sedimentary records seem to be optimal for studying past variability in sea-<span class="hlt">ice</span> coverage and testing the applicability of IP25 and PIP25 in older sedimentary sequences. In general, our biomarker records correlate quite well with other climate and sea-<span class="hlt">ice</span> proxies (e.g., dinoflagellates, IRD, etc.). The main results can be summarized as follows: (1) The novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea <span class="hlt">ice</span> studies <span class="hlt">covering</span> at least the last 3.5 Ma, i.e., the time interval including the onset (intensification) of major Northern Hemisphere Glaciation (NHG). (2) These data indicate that sea <span class="hlt">ice</span> of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. (3) Elevated IP25/PIP25 values indicative for an extended spring sea-<span class="hlt">ice</span> <span class="hlt">cover</span>, already occurred between 3.6 and 2.9 Ma, i.e., prior to the onset of major NHG. This may suggest that sea-<span class="hlt">ice</span> and related albedo effects might</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EOSTr..90R.169P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EOSTr..90R.169P"><span>Developing and Implementing Protocols for Arctic Sea <span class="hlt">Ice</span> Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perovich, Donald K.; Gerland, Sebastian</p> <p>2009-05-01</p> <p>Arctic Surface-<span class="hlt">Based</span> Sea <span class="hlt">Ice</span> Observations: Integrated Protocols and Coordinated Data Acquisition; Tromsø, Norway, 26-27 January 2009; The Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is diminishing. Over the past several years, not only has <span class="hlt">ice</span> thinned but the extent of <span class="hlt">ice</span> at the end of summer, and hence perennial <span class="hlt">ice</span>, has declined markedly. These changes affect a wide range of issues and are important for a varied group of stakeholders, including Arctic coastal communities, policy makers, industry, the scientific community, and the public. Concerns range from the role of sea <span class="hlt">ice</span> <span class="hlt">cover</span> as an indicator and amplifier of climate change to marine transportation, resource extraction, and coastal erosion. To understand and respond to these ongoing changes, it is imperative to develop and implement consistent and robust observational protocols that can be used to describe the current state of the <span class="hlt">ice</span> <span class="hlt">cover</span> as well as future changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B33B0665M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B33B0665M"><span>Biological Diversity Comprising Microbial Structures of Antarctic <span class="hlt">Ice</span> <span class="hlt">Covered</span> Lakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matys, E. D.</p> <p>2015-12-01</p> <p>Analysis of microbial membrane lipids is a rapid and non-selective method for evaluating the composition of microbial communities. To fully realise the diagnostic potential of these lipids, we must first understand their structural diversity, biological sources, physiological functions, and pathways of preservation. Particular environmental conditions likely prompt the production of different membrane lipid structures. Antarctica's McMurdo Dry Valleys host numerous <span class="hlt">ice-covered</span> lakes with sharp chemical gradients that vary in illumination, geochemical structure, and benthic mat morphologies that are structured by nutrient availability and water chemistry. The lipid contents of these benthic mats have not received extensive study nor have the communities yet been thoroughly characterized. Accordingly, a combination of lipid biomarker and nucleic acid sequence data provides the means of assessing species diversity and environmental controls on the composition and diversity of membrane lipid assemblages. We investigated the richness and diversity of benthic microbial communities and accumulated organic matter in Lake Vanda of the McMurdo Dry Valleys. We have identified diverse glycolipids, aminolipids, and phospholipids in addition to many unknown compounds that may be specific to these particular environments. Light levels fluctuate seasonally, favoring low-light-tolerant cyanobacteria and specific lipid assemblages. Adaptations to nutrient limitations are reflected in contrasting intact polar lipid assemblages. For example, under P-limiting conditions, phospholipids are subsidiary to membrane-forming lipids that do not contain P (i.e. ornithine, betaine, and sulfolipids). The bacteriohopanepolyol (BHP) composition is dominated by bacteriohopanetetrol (BHT), a ubiquitous BHP, and 2-methylhopanoids. The relative abundance of 2-methylhopanoids is unprecedented and may reflect the unusual seasonal light regime of this polar environment. By establishing correlations</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRG..122.2409A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRG..122.2409A"><span>Late Spring Nitrate Distributions Beneath the <span class="hlt">Ice-Covered</span> Northeastern Chukchi Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arrigo, Kevin R.; Mills, Matthew M.; van Dijken, Gert L.; Lowry, Kate E.; Pickart, Robert S.; Schlitzer, Reiner</p> <p>2017-09-01</p> <p>Measurements of late springtime nutrient concentrations in Arctic waters are relatively rare due to the extensive sea <span class="hlt">ice</span> <span class="hlt">cover</span> that makes sampling difficult. During the SUBICE (Study of Under-<span class="hlt">ice</span> Blooms In the Chukchi Ecosystem) cruise in May-June 2014, an extensive survey of hydrography and prebloom concentrations of inorganic macronutrients, oxygen, particulate organic carbon and nitrogen, and chlorophyll <fi>a</fi> was conducted in the northeastern Chukchi Sea. Cold (<-1.5°C) winter water was prevalent throughout the study area, and the water column was weakly stratified. Nitrate (NO3-) concentration averaged 12.6 ± 1.92 μ<fi>M</fi> in surface waters and 14.0 ± 1.91 μ<fi>M</fi> near the bottom and was significantly correlated with salinity. The highest NO3- concentrations were associated with winter water within the Central Channel flow path. NO3- concentrations were much reduced near the northern shelf break within the upper halocline waters of the Canada Basin and along the eastern side of the shelf near the Alaskan coast. Net community production (NCP), estimated as the difference in depth-integrated NO3- content between spring (this study) and summer (historical), varied from 28 to 38 g C m-2 a-1. This is much lower than previous NCP estimates that used NO3- concentrations from the southeastern Bering Sea as a baseline. These results demonstrate the importance of using profiles of NO3- measured as close to the beginning of the spring bloom as possible when estimating local NCP. They also show that once the snow melts in spring, increased light transmission through the sea <span class="hlt">ice</span> to the waters below the <span class="hlt">ice</span> could fuel large phytoplankton blooms over a much wider area than previously known.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRG..122.1486K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRG..122.1486K"><span>Windows in Arctic sea <span class="hlt">ice</span>: Light transmission and <span class="hlt">ice</span> algae in a refrozen lead</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kauko, Hanna M.; Taskjelle, Torbjørn; Assmy, Philipp; Pavlov, Alexey K.; Mundy, C. J.; Duarte, Pedro; Fernández-Méndez, Mar; Olsen, Lasse M.; Hudson, Stephen R.; Johnsen, Geir; Elliott, Ashley; Wang, Feiyue; Granskog, Mats A.</p> <p>2017-06-01</p> <p>The Arctic Ocean is rapidly changing from thicker multiyear to thinner first-year <span class="hlt">ice</span> <span class="hlt">cover</span>, with significant consequences for radiative transfer through the <span class="hlt">ice</span> pack and light availability for algal growth. A thinner, more dynamic <span class="hlt">ice</span> <span class="hlt">cover</span> will possibly result in more frequent leads, <span class="hlt">covered</span> by newly formed <span class="hlt">ice</span> with little snow <span class="hlt">cover</span>. We studied a refrozen lead (≤0.27 m <span class="hlt">ice</span>) in drifting pack <span class="hlt">ice</span> north of Svalbard (80.5-81.8°N) in May-June 2015 during the Norwegian young sea <span class="hlt">ICE</span> expedition (N-<span class="hlt">ICE</span>2015). We measured downwelling incident and <span class="hlt">ice</span>-transmitted spectral irradiance, and colored dissolved organic matter (CDOM), particle absorption, ultraviolet (UV)-protecting mycosporine-like amino acids (MAAs), and chlorophyll a (Chl a) in melted sea <span class="hlt">ice</span> samples. We found occasionally very high MAA concentrations (up to 39 mg m-3, mean 4.5 ± 7.8 mg m-3) and MAA to Chl a ratios (up to 6.3, mean 1.2 ± 1.3). Disagreement in modeled and observed transmittance in the UV range let us conclude that MAA signatures in CDOM absorption spectra may be artifacts due to osmotic shock during <span class="hlt">ice</span> melting. Although observed PAR (photosynthetically active radiation) transmittance through the thin <span class="hlt">ice</span> was significantly higher than that of the adjacent thicker <span class="hlt">ice</span> with deep snow <span class="hlt">cover</span>, <span class="hlt">ice</span> algal standing stocks were low (≤2.31 mg Chl a m-2) and similar to the adjacent <span class="hlt">ice</span>. <span class="hlt">Ice</span> algal accumulation in the lead was possibly delayed by the low inoculum and the time needed for photoacclimation to the high-light environment. However, leads are important for phytoplankton growth by acting like windows into the water column.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040089578&hterms=Carotenoids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DCarotenoids','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040089578&hterms=Carotenoids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DCarotenoids"><span>Lipophilic pigments from the benthos of a perennially <span class="hlt">ice-covered</span> Antarctic lake</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Palmisano, A. C.; Wharton, R. A. Jr; Cronin, S. E.; Des Marais, D. J.; Wharton RA, J. r. (Principal Investigator)</p> <p>1989-01-01</p> <p>The benthos of a perennially <span class="hlt">ice-covered</span> Antarctic lake, Lake Hoare, contained three distinct 'signatures' of lipophilic pigments. Cyanobacterial mats found in the moat at the periphery of the lake were dominated by the carotenoid myxoxanthophyll; carotenoids: chlorophyll a ratios in this high light environment ranged from 3 to 6.8. Chlorophyll c and fucoxanthin, pigments typical of golden-brown algae, were found at 10 to 20 m depths where the benthos is aerobic. Anaerobic benthic sediments at 20 to 30 m depths were characterized by a third pigment signature dominated by a carotenoid, tentatively identified as alloxanthin from planktonic cryptomonads, and by phaeophytin b from senescent green algae. Pigments were not found associated with alternating organic and sediment layers. As microzooplankton grazers are absent from this closed system and transformation rates are reduced at low temperatures, the benthos beneath the lake <span class="hlt">ice</span> appears to contain a record of past phytoplankton blooms undergoing decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP23B1393S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP23B1393S"><span>High-resolution record of last post-glacial variations of sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and river discharge in the western Laptev Sea (Arctic Ocean)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, R. H.; Hörner, T.; Fahl, K.</p> <p>2014-12-01</p> <p>Here, we provide a high-resolution reconstruction of sea-<span class="hlt">ice</span> <span class="hlt">cover</span> variations in the western Laptev Sea, a crucial area in terms of sea-<span class="hlt">ice</span> production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea <span class="hlt">Ice</span> Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-<span class="hlt">ice</span> algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-<span class="hlt">ice</span> <span class="hlt">cover</span> varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of <span class="hlt">ice</span>-rafted debris (IRD) interpreted as local <span class="hlt">ice</span>-cap expansions (Taldenkova et al. 2010), and sea <span class="hlt">ice</span> <span class="hlt">cover</span> distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. ReferencesBelt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea <span class="hlt">ice</span>: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of <span class="hlt">ice</span>-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090014780&hterms=Wrf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DWrf','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090014780&hterms=Wrf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DWrf"><span>Use of Vertically Integrated <span class="hlt">Ice</span> in WRF-<span class="hlt">Based</span> Forecasts of Lightning Threat</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McCaul, E. W., jr.; Goodman, S. J.</p> <p>2008-01-01</p> <p>Previously reported methods of forecasting lightning threat using fields of graupel flux from WRF simulations are extended to include the simulated field of vertically integrated <span class="hlt">ice</span> within storms. Although the <span class="hlt">ice</span> integral shows less temporal variability than graupel flux, it provides more areal coverage, and can thus be used to create a lightning forecast that better matches the areal coverage of the lightning threat found in observations of flash extent density. A blended lightning forecast threat can be constructed that retains much of the desirable temporal sensitivity of the graupel flux method, while also incorporating the coverage benefits of the <span class="hlt">ice</span> integral method. The graupel flux and <span class="hlt">ice</span> integral fields contributing to the blended forecast are calibrated against observed lightning flash origin density data, <span class="hlt">based</span> on Lightning Mapping Array observations from a series of case studies chosen to <span class="hlt">cover</span> a wide range of flash rate conditions. Linear curve fits that pass through the origin are found to be statistically robust for the calibration procedures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA265262','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA265262"><span>Beaufort Ambient Seismo-Acoustics Beneath <span class="hlt">Ice</span> <span class="hlt">Cover</span> (BASIC)</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-05-01</p> <p>detected with a revssure trans- •-’:-r on the deep-sea floor it of sufficiently long wavelength, and also by appropriate on-<span class="hlt">ice</span> sensors . The BASIC field...exper- iment. Because of the very quiet low frequency Arctic seafloor conditions, the measurements proved to be sensor noise limited above 2 Hz. As...and tiltmeters deployed on the <span class="hlt">ice</span> (Czipott and Podney, 1989; Williams et al, 1989). These distortions of the <span class="hlt">ice</span> are either driven by the local wind</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPA53B..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPA53B..05S"><span>Using a Flying Thing in the Sky to See How Much Water is in the <span class="hlt">Cover</span> of Tiny <span class="hlt">Ice</span> Pieces in the High Places</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skiles, M.</p> <p>2016-12-01</p> <p>Groups of tiny <span class="hlt">ice</span> pieces fall from the sky in the cold times and <span class="hlt">cover</span> the high places. Later, the tiny <span class="hlt">ice</span> pieces become water that moves to the lower places, where people can use it for drinking and stuff. The time when the tiny <span class="hlt">ice</span> pieces turn to water is controlled by the sun. New tiny <span class="hlt">ice</span> pieces from the sky, which are very white and don't take up much sun, group up and grow tall. When they become dark from getting old and large, and from getting <span class="hlt">covered</span> in tiny dark bits from the sky, they take up more sun and turn to water. The more tiny dark bits, the faster they become water. Using a flying thing over the high places we can see how much water will come from the <span class="hlt">cover</span> of tiny <span class="hlt">ice</span> pieces by using ground looking things to see how tall it is, and and when it will become water by using picture taking things to see how much sun is taken up. The low places are happy to know how much water is in the high places.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1013732','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1013732"><span>Wave-<span class="hlt">Ice</span> and Air-<span class="hlt">Ice</span>-Ocean Interaction During the Chukchi Sea <span class="hlt">Ice</span> Edge Advance</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-30</p> <p>1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Wave -<span class="hlt">Ice</span> and Air-<span class="hlt">Ice</span>-Ocean Interaction During the...Chukchi Sea in the late summer have potentially changed the impact of fall storms by creating wave fields in the vicinity of the advancing <span class="hlt">ice</span> edge. A...first) wave -<span class="hlt">ice</span> interaction field experiment that adequately documents the relationship of a growing pancake <span class="hlt">ice</span> <span class="hlt">cover</span> with a time and space varying</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120003985','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120003985"><span>Seafloor Control on Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, S. V.; Clemente-Colon, P.; Rigor, I. G.; Hall, D. K.; Neumann, G.</p> <p>2011-01-01</p> <p>The seafloor has a profound role in Arctic sea <span class="hlt">ice</span> formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea <span class="hlt">ice</span> on the ocean surface. Sea <span class="hlt">ice</span> dynamics, forced by surface winds, are also guided by seafloor features in preferential directions. Here, satellite mapping of sea <span class="hlt">ice</span> together with buoy measurements are used to reveal the bathymetric control on sea <span class="hlt">ice</span> growth and dynamics. Bathymetric effects on sea <span class="hlt">ice</span> formation are clearly observed in the conformation between sea <span class="hlt">ice</span> patterns and bathymetric characteristics in the peripheral seas. Beyond local features, bathymetric control appears over extensive <span class="hlt">ice</span>-prone regions across the Arctic Ocean. The large-scale conformation between bathymetry and patterns of different synoptic sea <span class="hlt">ice</span> classes, including seasonal and perennial sea <span class="hlt">ice</span>, is identified. An implication of the bathymetric influence is that the maximum extent of the total sea <span class="hlt">ice</span> <span class="hlt">cover</span> is relatively stable, as observed by scatterometer data in the decade of the 2000s, while the minimum <span class="hlt">ice</span> extent has decreased drastically. Because of the geologic control, the sea <span class="hlt">ice</span> <span class="hlt">cover</span> can expand only as far as it reaches the seashore, the continental shelf break, or other pronounced bathymetric features in the peripheral seas. Since the seafloor does not change significantly for decades or centuries, sea <span class="hlt">ice</span> patterns can be recurrent around certain bathymetric features, which, once identified, may help improve short-term forecast and seasonal outlook of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Moreover, the seafloor can indirectly influence cloud <span class="hlt">cover</span> by its control on sea <span class="hlt">ice</span> distribution, which differentially modulates the latent heat flux through <span class="hlt">ice</span> <span class="hlt">covered</span> and open water areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC12A..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC12A..01S"><span>Towards Improving Sea <span class="hlt">Ice</span> Predictabiity: Evaluating Climate Models Against Satellite Sea <span class="hlt">Ice</span> Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J. C.</p> <p>2014-12-01</p> <p>The last four decades have seen a remarkable decline in the spatial extent of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, presenting both challenges and opportunities to Arctic residents, government agencies and industry. After the record low extent in September 2007 effort has increased to improve seasonal, decadal-scale and longer-term predictions of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Coupled global climate models (GCMs) consistently project that if greenhouse gas concentrations continue to rise, the eventual outcome will be a complete loss of the multiyear <span class="hlt">ice</span> <span class="hlt">cover</span>. However, confidence in these projections depends o HoHoweon the models ability to reproduce features of the present-day climate. Comparison between models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 5 (CMIP5) and observations of sea <span class="hlt">ice</span> extent and thickness show that (1) historical trends from 85% of the model ensemble members remain smaller than observed, and (2) spatial patterns of sea <span class="hlt">ice</span> thickness are poorly represented in most models. Part of the explanation lies with a failure of models to represent details of the mean atmospheric circulation pattern that governs the transport and spatial distribution of sea <span class="hlt">ice</span>. These results raise concerns regarding the ability of CMIP5 models to realistically represent the processes driving the decline of Arctic sea <span class="hlt">ice</span> and to project the timing of when a seasonally <span class="hlt">ice</span>-free Arctic may be realized. On shorter time-scales, seasonal sea <span class="hlt">ice</span> prediction has been challenged to predict the sea <span class="hlt">ice</span> extent from Arctic conditions a few months to a year in advance. Efforts such as the Sea <span class="hlt">Ice</span> Outlook (SIO) project, originally organized through the Study of Environmental Change (SEARCH) and now managed by the Sea <span class="hlt">Ice</span> Prediction Network project (SIPN) synthesize predictions of the September sea <span class="hlt">ice</span> extent <span class="hlt">based</span> on a variety of approaches, including heuristic, statistical and dynamical modeling. Analysis of SIO contributions reveals that when the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817638P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817638P"><span>RADARSAT-2 Polarimetry for Lake <span class="hlt">Ice</span> Mapping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, Feng; Kang, Kyung-Kuk; Duguay, Claude</p> <p>2016-04-01</p> <p>Changes in the <span class="hlt">ice</span> regime of lakes can be employed to assess long-term climate trends and variability in high latitude regions. Lake <span class="hlt">ice</span> <span class="hlt">cover</span> observations are not only useful for climate monitoring, but also for improving <span class="hlt">ice</span> and weather forecasts using numerical prediction models. In recent years, satellite remote sensing has assumed a greater role in observing lake <span class="hlt">ice</span> <span class="hlt">cover</span> for both purposes. Radar remote sensing has become an essential tool for mapping lake <span class="hlt">ice</span> at high latitudes where cloud <span class="hlt">cover</span> and polar darkness severely limits <span class="hlt">ice</span> observations from optical systems. In Canada, there is an emerging interest by government agencies to evaluate the potential of fully polarimetric synthetic aperture radar (SAR) data from RADARSAT-2 (C-band) for lake <span class="hlt">ice</span> monitoring. In this study, we processed and analyzed the polarization states and scattering mechanisms of fully polarimetric RADARSAT-2 data obtained over Great Bear Lake, Canada, to identify open water and different <span class="hlt">ice</span> types during the freeze-up and break-up periods. Polarimetric decompositions were employed to separate polarimetric measurements into basic scattering mechanisms. Entropy, anisotropy, and alpha angle were derived to characterize the scattering heterogeneity and mechanisms. <span class="hlt">Ice</span> classes were then determined <span class="hlt">based</span> on entropy and alpha angle using the unsupervised Wishart classifier and results evaluated against Landsat 8 imagery. Preliminary results suggest that the RADARSAT-2 polarimetric data offer a strong capability for identifying open water and different lake <span class="hlt">ice</span> types.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C21C0622M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C21C0622M"><span>Meteorological conditions influencing the formation of level <span class="hlt">ice</span> within the Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazur, A. K.; Krezel, A.</p> <p>2012-12-01</p> <p>The Baltic Sea is <span class="hlt">covered</span> by <span class="hlt">ice</span> every winter and on average, the <span class="hlt">ice-covered</span> area is 45% of the total area of the Baltic Sea. The beginning of <span class="hlt">ice</span> season usually starts in the end of November, <span class="hlt">ice</span> extent is the largest between mid-February and mid-March and sea <span class="hlt">ice</span> disappears completely in May. The <span class="hlt">ice</span> <span class="hlt">covered</span> areas during a typical winter are the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga. The studies of sea <span class="hlt">ice</span> in the Baltic Sea are related to two aspects: climate and marine transport. Depending on the local weather conditions during the winter different types of sea <span class="hlt">ice</span> can be formed. From the point of winter shipping it is important to locate level and deformed <span class="hlt">ice</span> areas (rafted <span class="hlt">ice</span>, ridged <span class="hlt">ice</span>, and hummocked <span class="hlt">ice</span>). Because of cloud and daylight independency as well as good spatial resolution, SAR data seems to be the most suitable source of data for sea <span class="hlt">ice</span> observation in the comparatively small area of the Baltic Sea. We used ASAR Wide Swath Mode data with spatial resolution 150 m. We analyzed data from the three winter seasons which were examples of severe, typical and mild winters. To remove the speckle effect the data were resampled to 250 m pixel size and filtred using Frost filter 5x5. To detect edges we used Sobel filter. The data were also converted into grayscale. Sea <span class="hlt">ice</span> classification was <span class="hlt">based</span> on Object-<span class="hlt">Based</span> Image Analysis (OBIA). Object-<span class="hlt">based</span> methods are not a common tool in sea <span class="hlt">ice</span> studies but they seem to accurately separate level <span class="hlt">ice</span> within the <span class="hlt">ice</span> pack. The data were segmented and classified using eCognition Developer software. Level <span class="hlt">ice</span> were classified <span class="hlt">based</span> on texture features defined by Haralick (Grey Level Co-Occurrence Matrix homogeneity, GLCM contrast, GLCM entropy and GLCM correlation). The long-term changes of the Baltic Sea <span class="hlt">ice</span> conditions have been already studied. They include date of freezing, date of break-up, sea <span class="hlt">ice</span> extent and some of work also <span class="hlt">ice</span> thickness. There is a little knowledge about the relationship of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21141043','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21141043"><span>Loss of sea <span class="hlt">ice</span> in the Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perovich, Donald K; Richter-Menge, Jacqueline A</p> <p>2009-01-01</p> <p>The Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is in decline. The areal extent of the <span class="hlt">ice</span> <span class="hlt">cover</span> has been decreasing for the past few decades at an accelerating rate. Evidence also points to a decrease in sea <span class="hlt">ice</span> thickness and a reduction in the amount of thicker perennial sea <span class="hlt">ice</span>. A general global warming trend has made the <span class="hlt">ice</span> <span class="hlt">cover</span> more vulnerable to natural fluctuations in atmospheric and oceanic forcing. The observed reduction in Arctic sea <span class="hlt">ice</span> is a consequence of both thermodynamic and dynamic processes, including such factors as preconditioning of the <span class="hlt">ice</span> <span class="hlt">cover</span>, overall warming trends, changes in cloud coverage, shifts in atmospheric circulation patterns, increased export of older <span class="hlt">ice</span> out of the Arctic, advection of ocean heat from the Pacific and North Atlantic, enhanced solar heating of the ocean, and the <span class="hlt">ice</span>-albedo feedback. The diminishing Arctic sea <span class="hlt">ice</span> is creating social, political, economic, and ecological challenges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1005076','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1005076"><span>Sunlight, Sea <span class="hlt">Ice</span>, and the <span class="hlt">Ice</span> Albedo Feedback in a Changing Artic Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-11-30</p> <p>information from the PIOMAS model [J. Zhang], melt pond coverage from MODIS [Rösel et al., 2012], and <span class="hlt">ice</span>-age estimates [Maslanik et al., 2011] to...determined from MODIS satellite data using an artificial neural network, Cryosph., 6(2), 431–446, doi:10.5194/tc- 6-431-2012. PUBLICATIONS Carmack...from MODIS , and <span class="hlt">ice</span>-age estimates to this dataset. We have used this extented dataset to build a climatology of the partitioning of solar heat between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21A0700M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21A0700M"><span>Into the Deep Black Sea: The Icefin Modular AUV for <span class="hlt">Ice-Covered</span> Ocean Exploration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meister, M. R.; Schmidt, B. E.; West, M. E.; Walker, C. C.; Buffo, J.; Spears, A.</p> <p>2015-12-01</p> <p>The Icefin autonomous underwater vehicle (AUV) was designed to enable long-range oceanographic exploration of physical and biological ocean environments in <span class="hlt">ice-covered</span> regions. The vehicle is capable of surveying under-<span class="hlt">ice</span> geometry, <span class="hlt">ice</span> and <span class="hlt">ice</span>-ocean interface properties, as well as water column conditions beneath the <span class="hlt">ice</span> interface. It was developed with both cryospheric and planetary-analog exploration in mind. The first Icefin prototype was successfully operated in Antarctica in Austral summer 2014. The vehicle was deployed through a borehole in the McMurdo <span class="hlt">Ice</span> Shelf near Black Island and successfully collected sonar, imaging, video and water column data down to 450 m depth. Icefin was developed using a modular design. Each module is designed to perform specific tasks, dependent on the mission objective. Vehicle control and data systems can be stably developed, and power modules added or subtracted for mission flexibility. Multiple sensor bays can be developed in parallel to serve multiple science objectives. This design enables the vehicle to have greater depth capability as well as improved operational simplicity compared to larger vehicles with equivalent capabilities. As opposed to those vehicles that require greater logistics and associated costs, Icefin can be deployed through boreholes drilled in the <span class="hlt">ice</span>. Thus, Icefin satisfies the demands of achieving sub-<span class="hlt">ice</span> missions while maintaining a small form factor and easy deployment necessary for repeated, low-logistical impact field programs. The current Icefin prototype is 10.5 inches in diameter by 10 feet long and weighs 240 pounds. It is comprised of two thruster modules with hovering capabilities, an oceanographic sensing module, main control module and a forward-sensing module for obstacle avoidance. The oceanographic sensing module is fitted with a side scan sonar (SSS), CT sensor, altimetry profiler and Doplar Velocity Log (DVL) with current profiling. Icefin is depth-rated to 1500 m and is equipped with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22977068','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22977068"><span>Retention of <span class="hlt">ice</span>-associated amphipods: possible consequences for an <span class="hlt">ice</span>-free Arctic Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berge, J; Varpe, O; Moline, M A; Wold, A; Renaud, P E; Daase, M; Falk-Petersen, S</p> <p>2012-12-23</p> <p>Recent studies predict that the Arctic Ocean will have <span class="hlt">ice</span>-free summers within the next 30 years. This poses a significant challenge for the marine organisms associated with the Arctic sea <span class="hlt">ice</span>, such as marine mammals and, not least, the <span class="hlt">ice</span>-associated crustaceans generally considered to spend their entire life on the underside of the Arctic sea <span class="hlt">ice</span>. <span class="hlt">Based</span> upon unique samples collected within the Arctic Ocean during the polar night, we provide a new conceptual understanding of an intimate connection between these under-<span class="hlt">ice</span> crustaceans and the deep Arctic Ocean currents. We suggest that downwards vertical migrations, followed by polewards transport in deep ocean currents, are an adaptive trait of <span class="hlt">ice</span> fauna that both increases survival during <span class="hlt">ice</span>-free periods of the year and enables re-colonization of sea <span class="hlt">ice</span> when they ascend within the Arctic Ocean. From an evolutionary perspective, this may have been an adaptation allowing success in a seasonally <span class="hlt">ice-covered</span> Arctic. Our findings may ultimately change the perception of <span class="hlt">ice</span> fauna as a biota imminently threatened by the predicted disappearance of perennial sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830045130&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmarginal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830045130&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmarginal"><span>A coupled <span class="hlt">ice</span>-ocean model of upwelling in the marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roed, L. P.; Obrien, J. J.</p> <p>1983-01-01</p> <p>A dynamical coupled <span class="hlt">ice</span>-ocean numerical model for the marginal <span class="hlt">ice</span> zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea <span class="hlt">ice</span> model has a variable <span class="hlt">ice</span> concentration and includes internal <span class="hlt">ice</span> stress. The model is forced by stresses on the air/ocean and air/<span class="hlt">ice</span> surfaces. The main coupling between the <span class="hlt">ice</span> and the ocean is in the form of an interfacial stress on the <span class="hlt">ice</span>/ocean interface. The ocean model is a linear reduced gravity model. The wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water, while the interfacial stress <span class="hlt">ice</span>/ocean is proportional to the concentration of <span class="hlt">ice</span>. A new mechanism for <span class="hlt">ice</span> edge upwelling is suggested <span class="hlt">based</span> on a geostrophic equilibrium solution for the sea <span class="hlt">ice</span> medium. The upwelling reported in previous models invoking a stationary <span class="hlt">ice</span> <span class="hlt">cover</span> is shown to be replaced by a weak downwelling due to the <span class="hlt">ice</span> motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across <span class="hlt">ice</span> edge upper ocean transport. On the basis of numerical model, an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70157131','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70157131"><span>A 600-ka Arctic sea-<span class="hlt">ice</span> record from Mendeleev Ridge <span class="hlt">based</span> on ostracodes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cronin, Thomas M.; Polyak, L.V.; Reed, D.; Kandiano, E. S.; Marzen, R. E.; Council, E. A.</p> <p>2013-01-01</p> <p>Arctic paleoceanography and sea-<span class="hlt">ice</span> history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) <span class="hlt">covers</span> several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, ∼500 ka) with an average sedimentation rate of ∼0.5 cm/ka for most of the stratigraphy (MIS 5–13). Results <span class="hlt">based</span> on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (∼400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea <span class="hlt">ice</span> occurred after MIS 11 <span class="hlt">based</span> on the distribution of an <span class="hlt">ice</span>-dwelling ostracode Acetabulastoma arcticum. Spectral analyses of the ostracode assemblages indicate sea <span class="hlt">ice</span> and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (∼22 ka) and obliquity (∼40 ka) frequencies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010026440','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010026440"><span>Observation of Sea <span class="hlt">Ice</span> Surface Thermal States Under Cloud <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, S. V.; Perovich, D. K.; Gow, A. J.; Kwok, R.; Barber, D. G.; Comiso, J. C.; Zukor, Dorothy J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Clouds interfere with the distribution of short-wave and long-wave radiations over sea <span class="hlt">ice</span>, and thereby strongly affect the surface energy balance in polar regions. To evaluate the overall effects of clouds on climatic feedback processes in the atmosphere-<span class="hlt">ice</span>-ocean system, the challenge is to observe sea <span class="hlt">ice</span> surface thermal states under both clear sky and cloudy conditions. From laboratory experiments, we show that C-band radar (transparent to clouds) backscatter is very sensitive to the surface temperature of first-year sea <span class="hlt">ice</span>. The effect of sea <span class="hlt">ice</span> surface temperature on the magnitude of backscatter change depends on the thermal regimes of sea <span class="hlt">ice</span> thermodynamic states. For the temperature range above the mirabilite (Na2SO4.10H20) crystallization point (-8.2 C), C-band data show sea <span class="hlt">ice</span> backscatter changes by 8-10 dB for incident angles from 20 to 35 deg at both horizontal and vertical polarizations. For temperatures below the mirabilite point but above the crystallization point of MgCl2.8H2O (-18.0 C), relatively strong backwater changes between 4-6 dB are observed. These backscatter changes correspond to approximately 8 C change in temperature for both cases. The backscattering mechanism is related to the temperature which determines the thermodynamic distribution of brine volume in the sea <span class="hlt">ice</span> surface layer. The backscatter is positively correlated to temperature and the process is reversible with thermodynamic variations such as diurnal insolation effects. From two different dates in May 1993 with clear and overcast conditions determined by the Advanced Very High Resolution Radiometer (AVHRR), concurrent Earth Resources Satellite 1 (ERS-1) C-band <span class="hlt">ice</span> observed with increases in backscatter over first-year sea <span class="hlt">ice</span>, and verified by increases in in-situ sea <span class="hlt">ice</span> surface temperatures measured at the Collaborative-Interdisciplinary Cryosphere Experiment (C-<span class="hlt">ICE</span>) site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026030','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026030"><span><span class="hlt">Ice</span> <span class="hlt">cover</span>, landscape setting, and geological framework of Lake Vostok, East Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Studinger, M.; Bell, R.E.; Karner, G.D.; Tikku, A.A.; Holt, J.W.; Morse, D.L.; David, L.; Richter, T.G.; Kempf, S.D.; Peters, M.E.; Blankenship, D.D.; Sweeney, R.E.; Rystrom, V.L.</p> <p>2003-01-01</p> <p>Lake Vostok, located beneath more than 4 km of <span class="hlt">ice</span> in the middle of East Antarctica, is a unique subglacial habitat and may contain microorganisms with distinct adaptations to such an extreme environment. Melting and freezing at the <span class="hlt">base</span> of the <span class="hlt">ice</span> sheet, which slowly flows across the lake, controls the flux of water, biota and sediment particles through the lake. The influx of thermal energy, however, is limited to contributions from below. Thus the geological origin of Lake Vostok is a critical boundary condition for the subglacial ecosystem. We present the first comprehensive maps of <span class="hlt">ice</span> surface, <span class="hlt">ice</span> thickness and subglacial topography around Lake Vostok. The <span class="hlt">ice</span> flow across the lake and the landscape setting are closely linked to the geological origin of Lake Vostok. Our data show that Lake Vostok is located along a major geological boundary. Magnetic and gravity data are distinct east and west of the lake, as is the roughness of the subglacial topography. The physiographic setting of the lake has important consequences for the <span class="hlt">ice</span> flow and thus the melting and freezing pattern and the lake's circulation. Lake Vostok is a tectonically controlled subglacial lake. The tectonic processes provided the space for a unique habitat and recent minor tectonic activity could have the potential to introduce small, but significant amounts of thermal energy into the lake. ?? 2002 Elsevier Science B.V. All rights reserved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21B1120W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21B1120W"><span>Autonomous <span class="hlt">Ice</span> Mass Balance Buoys for Seasonal Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whitlock, J. D.; Planck, C.; Perovich, D. K.; Parno, J. T.; Elder, B. C.; Richter-Menge, J.; Polashenski, C. M.</p> <p>2017-12-01</p> <p>The <span class="hlt">ice</span> mass-balance represents the integration of all surface and ocean heat fluxes and attributing the impact of these forcing fluxes on the <span class="hlt">ice</span> <span class="hlt">cover</span> can be accomplished by increasing temporal and spatial measurements. Mass balance information can be used to understand the ongoing changes in the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> and to improve predictions of future <span class="hlt">ice</span> conditions. Thinner seasonal <span class="hlt">ice</span> in the Arctic necessitates the deployment of Autonomous <span class="hlt">Ice</span> Mass Balance buoys (IMB's) capable of long-term, in situ data collection in both <span class="hlt">ice</span> and open ocean. Seasonal IMB's (SIMB's) are free floating IMB's that allow data collection in thick <span class="hlt">ice</span>, thin <span class="hlt">ice</span>, during times of transition, and even open water. The newest generation of SIMB aims to increase the number of reliable IMB's in the Arctic by leveraging inexpensive commercial-grade instrumentation when combined with specially developed monitoring hardware. Monitoring tasks are handled by a custom, expandable data logger that provides low-cost flexibility for integrating a large range of instrumentation. The SIMB features ultrasonic sensors for direct measurement of both snow depth and <span class="hlt">ice</span> thickness and a digital temperature chain (DTC) for temperature measurements every 2cm through both snow and <span class="hlt">ice</span>. Air temperature and pressure, along with GPS data complete the Arctic picture. Additionally, the new SIMB is more compact to maximize deployment opportunities from multiple types of platforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950024430','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950024430"><span>A laser-<span class="hlt">based</span> <span class="hlt">ice</span> shape profilometer for use in <span class="hlt">icing</span> wind tunnels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hovenac, Edward A.; Vargas, Mario</p> <p>1995-01-01</p> <p>A laser-<span class="hlt">based</span> profilometer was developed to measure the thickness and shape of <span class="hlt">ice</span> accretions on the leading edge of airfoils and other models in <span class="hlt">icing</span> wind tunnels. The instrument is a hand held device that is connected to a desk top computer with a 10 meter cable. It projects a laser line onto an <span class="hlt">ice</span> shape and used solid state cameras to detect the light scattered by the <span class="hlt">ice</span>. The instrument corrects the image for camera angle distortions, displays an outline of the <span class="hlt">ice</span> shape on the computer screen, saves the data on a disk, and can print a full scale drawing of the <span class="hlt">ice</span> shape. The profilometer has undergone extensive testing in the laboratory and in the NASA Lewis <span class="hlt">Icing</span> Research Tunnel. Results of the tests show very good agreement between profilometer measurements and known simulated <span class="hlt">ice</span> shapes and fair agreement between profilometer measurements and hand tracing techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020090884&hterms=modis+snow+cover&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodis%2Bsnow%2Bcover','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020090884&hterms=modis+snow+cover&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodis%2Bsnow%2Bcover"><span>MODIS Snow and <span class="hlt">Ice</span> Production</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, Dorthoy K.; Hoser, Paul (Technical Monitor)</p> <p>2002-01-01</p> <p>Daily, global snow <span class="hlt">cover</span> maps, and sea <span class="hlt">ice</span> <span class="hlt">cover</span> and sea <span class="hlt">ice</span> surface temperature (IST) maps are derived from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), are available at no cost through the National Snow and <span class="hlt">Ice</span> Data Center (NSIDC). Included on this CD-ROM are samples of the MODIS snow and <span class="hlt">ice</span> products. In addition, an animation, done by the Scientific Visualization studio at Goddard Space Flight Center, is also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26ES..113a2218Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26ES..113a2218Y"><span>The application of remote sensing image sea <span class="hlt">ice</span> monitoring method in Bohai Bay <span class="hlt">based</span> on C4.5 decision tree algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ye, Wei; Song, Wei</p> <p>2018-02-01</p> <p>In The Paper, the remote sensing monitoring of sea <span class="hlt">ice</span> problem was turned into a classification problem in data mining. <span class="hlt">Based</span> on the statistic of the related band data of HJ1B remote sensing images, the main bands of HJ1B images related with the reflectance of seawater and sea <span class="hlt">ice</span> were found. On the basis, the decision tree rules for sea <span class="hlt">ice</span> monitoring were constructed by the related bands found above, and then the rules were applied to Liaodong Bay area seriously <span class="hlt">covered</span> by sea <span class="hlt">ice</span> for sea <span class="hlt">ice</span> monitoring. The result proved that the method is effective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001118.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001118.html"><span>Persistent <span class="hlt">Ice</span> on Lake Superior</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p>Though North America is a full month into astronomical spring, the Great Lakes have been slow to give up on winter. As of April 22, 2014, the Great Lakes were 33.9 percent <span class="hlt">ice</span> <span class="hlt">covered</span>. The lake they call Superior dominated the pack. In the early afternoon on April 20, 2014, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of Lake Superior, which straddles the United States–Canada border. At the time Aqua passed over, the lake was 63.5 percent <span class="hlt">ice</span> <span class="hlt">covered</span>, according to the NOAA Great Lakes Environmental Research Lab (GLERL). Averaged across Lake Superior, <span class="hlt">ice</span> was 22.6 centimeters (8.9 inches) thick; it was as much as twice that thickness in some locations. GLERL researcher George Leshkevich affirmed that <span class="hlt">ice</span> <span class="hlt">cover</span> this spring is significantly above normal. For comparison, Lake Superior had 3.6 percent <span class="hlt">ice</span> <span class="hlt">cover</span> on April 20, 2013; in 2012, <span class="hlt">ice</span> was completely gone by April 12. In the last winter that <span class="hlt">ice</span> <span class="hlt">cover</span> grew so thick on Lake Superior (2009), it reached 93.7 percent on March 2 but was down to 6.7 percent by April 21. Average water temperatures on all of the Great Lakes have been rising over the past 30 to 40 years and <span class="hlt">ice</span> <span class="hlt">cover</span> has generally been shrinking. (Lake Superior <span class="hlt">ice</span> was down about 79 percent since the 1970s.) But chilled by persistent polar air masses throughout the 2013-14 winter, <span class="hlt">ice</span> <span class="hlt">cover</span> reached 88.4 percent on February 13 and 92.2 percent on March 6, 2014, the second highest level in four decades of record-keeping. Air temperatures in the Great Lakes region were well below normal for March, and the cool pattern is being reinforced along the coasts because the water is absorbing less sunlight and warming less than in typical spring conditions. The graph below, <span class="hlt">based</span> on data from Environment Canada, shows the 2014 conditions for all of the Great Lakes in mid-April compared to the past 33 years. Lake Superior <span class="hlt">ice</span> <span class="hlt">cover</span> got as high as 95.3 percent on March 19. By April 22, it was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19109440','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19109440"><span>Nonlinear threshold behavior during the loss of Arctic sea <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Eisenman, I; Wettlaufer, J S</p> <p>2009-01-06</p> <p>In light of the rapid recent retreat of Arctic sea <span class="hlt">ice</span>, a number of studies have discussed the possibility of a critical threshold (or "tipping point") beyond which the <span class="hlt">ice</span>-albedo feedback causes the <span class="hlt">ice</span> <span class="hlt">cover</span> to melt away in an irreversible process. The focus has typically been centered on the annual minimum (September) <span class="hlt">ice</span> <span class="hlt">cover</span>, which is often seen as particularly susceptible to destabilization by the <span class="hlt">ice</span>-albedo feedback. Here, we examine the central physical processes associated with the transition from <span class="hlt">ice-covered</span> to <span class="hlt">ice</span>-free Arctic Ocean conditions. We show that although the <span class="hlt">ice</span>-albedo feedback promotes the existence of multiple <span class="hlt">ice-cover</span> states, the stabilizing thermodynamic effects of sea <span class="hlt">ice</span> mitigate this when the Arctic Ocean is <span class="hlt">ice</span> <span class="hlt">covered</span> during a sufficiently large fraction of the year. These results suggest that critical threshold behavior is unlikely during the approach from current perennial sea-<span class="hlt">ice</span> conditions to seasonally <span class="hlt">ice</span>-free conditions. In a further warmed climate, however, we find that a critical threshold associated with the sudden loss of the remaining wintertime-only sea <span class="hlt">ice</span> <span class="hlt">cover</span> may be likely.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP13A2058R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP13A2058R"><span>Glacial-Geomorphological Evidence for Past <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Western Amundsen Sea Embayment of Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roberts, S. J.; Johnson, J.; Ireland, L.; Rood, D. H.; Schaefer, J. M.; Whitehouse, P. L.; Pollard, D.</p> <p>2016-12-01</p> <p>Reliable model predictions of the future evolution of the West Antarctic <span class="hlt">Ice</span> Sheet in the Amundsen Sea Embayment of Antarctica are currently hindered by a lack of data on the regional thinning history, particularly to the west of Thwaites Glacier. Our project will fill this critical gap by acquiring glacial-geological data, in particular, a high density of cosmogenic exposure ages that record <span class="hlt">ice</span> sheet changes in the western Amundsen Sea Embayment over the past 20,000 years. In 2015/6, during the first of two field seasons in the region, we collected glacial-geomorphological evidence and cosmogenic surface exposure dating samples to constrain past <span class="hlt">ice</span> <span class="hlt">cover</span> of nunataks around Mt Murphy, which are adjacent to the Pope Glacier. The presence of abundant rounded granite and gneiss cobbles perched on bedrock ridges and terraces up to 885 m asl, as well as extensive striated bedrock above this height, indicate that <span class="hlt">ice</span> was much thicker in the past. We also present preliminary results from a novel study on Turtle Rock, a key site for understanding past fluctuations of Pope Glacier. We used an unmanned aerial vehicle (UAV) to map the geomorphology of selected areas in greater detail than is currently possible from high-resolution satellite imagery, and ground-truthed the data by measuring the size, orientation and lithological composition of erratic cobbles and boulders. Combined with surface exposure dating, we will use these datasets to determine whether there were multiple phases of <span class="hlt">ice</span> overriding, and the timing of thinning of Pope Glacier since the Last Glacial Maximum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840025846&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840025846&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>Passive microwave characteristics of the Bering Sea <span class="hlt">ice</span> <span class="hlt">cover</span> during Marginal <span class="hlt">Ice</span> Zone Experiment (MIZEX) West</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, D. J.; Gloersen, P.; Wilheit, T. T.; Calhoon, C.</p> <p>1984-01-01</p> <p>Passive microwave measurements of the Bering Sea were made with the NASA CV-990 airborne laboratory during February. Microwave data were obtained with imaging and dual-polarized, fixed-beam radiometers in a range of frequencies from 10 to 183 GHz. The high resolution imagery at 92 GHz provides a particularly good description of the marginal <span class="hlt">ice</span> zone delineating regions of open water, <span class="hlt">ice</span> compactness, and <span class="hlt">ice</span>-edge structure. Analysis of the fixed-beam data shows that spectral differences increase with a decrease in <span class="hlt">ice</span> thickness. Polarization at 18 and 37 GHz distinguishes among new, young, and first-year sea <span class="hlt">ice</span> types.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMED13B0590H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMED13B0590H"><span><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby: A Program for Sustained, Classroom-<span class="hlt">Based</span> K-8 Teacher Professional Development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamilton, C.</p> <p>2009-12-01</p> <p><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby is a K-8 science program created by the education team at the Center for the Remote Sensing of <span class="hlt">Ice</span> Sheets (CReSIS), an NSF-funded science and technology center headquartered at the University of Kansas. The twenty-four hands-on activities, which constitute the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby curriculum, were developed to help students understand the role of polar <span class="hlt">ice</span> sheets in sea level rise. These activities, presented in classrooms by CReSIS' Educational Outreach Coordinator, demonstrate many of the scientific properties of <span class="hlt">ice</span>, including displacement and density. Student journals are utilized with each lesson as a strategy for improving students' science process skills. Journals also help the instructor identify misconceptions, assess comprehension, and provide students with a year-long science reference log. Pre- and post- assessments are given to both teachers and students before and after the program, providing data for evaluation and improvement of the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program. While students are actively engaged in hands-on learning about the unusual topics of <span class="hlt">ice</span> sheets, glaciers, icebergs and sea <span class="hlt">ice</span>, the CReSIS' Educational Coordinator is able to model best practices in science education, such as questioning and inquiry-<span class="hlt">based</span> methods of instruction. In this way, the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program also serves as ongoing, in-class, professional development for teachers. Teachers are also provided supplemental activities to do with their classes between CReSIS' visits to encourage additional science lessons, reinforce concepts taught in the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program, and to foster teachers' progression toward more reform-<span class="hlt">based</span> science instruction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24457629','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24457629"><span>Determining the <span class="hlt">ice</span>-binding planes of antifreeze proteins by fluorescence-<span class="hlt">based</span> <span class="hlt">ice</span> plane affinity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Basu, Koli; Garnham, Christopher P; Nishimiya, Yoshiyuki; Tsuda, Sakae; Braslavsky, Ido; Davies, Peter</p> <p>2014-01-15</p> <p>Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal <span class="hlt">ice</span> growth. AFPs bind to specific planes of <span class="hlt">ice</span> through their <span class="hlt">ice</span>-binding surfaces. Fluorescence-<span class="hlt">based</span> <span class="hlt">ice</span> plane affinity (FIPA) analysis is a modified technique used to determine the <span class="hlt">ice</span> planes to which the AFPs bind. FIPA is <span class="hlt">based</span> on the original <span class="hlt">ice</span>-etching method for determining AFP-bound <span class="hlt">ice</span>-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single <span class="hlt">ice</span> crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound <span class="hlt">ice</span> hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into <span class="hlt">ice</span>. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single <span class="hlt">ice</span> crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to <span class="hlt">ice</span> to halt its growth and why many AFP-producing organisms express multiple AFP isoforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4089408','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4089408"><span>Determining the <span class="hlt">Ice</span>-binding Planes of Antifreeze Proteins by Fluorescence-<span class="hlt">based</span> <span class="hlt">Ice</span> Plane Affinity</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Basu, Koli; Garnham, Christopher P.; Nishimiya, Yoshiyuki; Tsuda, Sakae; Braslavsky, Ido; Davies, Peter</p> <p>2014-01-01</p> <p>Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal <span class="hlt">ice</span> growth. AFPs bind to specific planes of <span class="hlt">ice</span> through their <span class="hlt">ice</span>-binding surfaces. Fluorescence-<span class="hlt">based</span> <span class="hlt">ice</span> plane affinity (FIPA) analysis is a modified technique used to determine the <span class="hlt">ice</span> planes to which the AFPs bind. FIPA is <span class="hlt">based</span> on the original <span class="hlt">ice</span>-etching method for determining AFP-bound <span class="hlt">ice</span>-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single <span class="hlt">ice</span> crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound <span class="hlt">ice</span> hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into <span class="hlt">ice</span>. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single <span class="hlt">ice</span> crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to <span class="hlt">ice</span> to halt its growth and why many AFP-producing organisms express multiple AFP isoforms. PMID:24457629</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21805086','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21805086"><span>Direct and indirect climatic drivers of biotic interactions: <span class="hlt">ice-cover</span> and carbon runoff shaping Arctic char Salvelinus alpinus and brown trout Salmo trutta competitive asymmetries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ulvan, Eva M; Finstad, Anders G; Ugedal, Ola; Berg, Ole Kristian</p> <p>2012-01-01</p> <p>One of the major challenges in ecological climate change impact science is to untangle the climatic effects on biological interactions and indirect cascading effects through different ecosystems. Here, we test for direct and indirect climatic drivers on competitive impact of Arctic char (Salvelinus alpinus L.) on brown trout (Salmo trutta L.) along a climate gradient in central Scandinavia, spanning from coastal to high-alpine environments. As a measure of competitive impact, trout food consumption was measured using (137)Cs tracer methodology both during the <span class="hlt">ice-covered</span> and <span class="hlt">ice</span>-free periods, and contrasted between lakes with or without char coexistence along the climate gradient. Variation in food consumption between lakes was best described by a linear mixed effect model including a three-way interaction between the presence/absence of Arctic char, season and Secchi depth. The latter is proxy for terrestrial dissolved organic carbon run-off, strongly governed by climatic properties of the catchment. The presence of Arctic char had a negative impact on trout food consumption. However, this effect was stronger during <span class="hlt">ice-cover</span> and in lakes receiving high carbon load from the catchment, whereas no effect of water temperature was evident. In conclusion, the length of the <span class="hlt">ice-covered</span> period and the export of allochthonous material from the catchment are likely major, but contrasting, climatic drivers of the competitive interaction between two freshwater lake top predators. While future climatic scenarios predict shorter <span class="hlt">ice-cover</span> duration, they also predict increased carbon run-off. The present study therefore emphasizes the complexity of cascading ecosystem effects in future effects of climate change on freshwater ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......122B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......122B"><span>Greenland <span class="hlt">ice</span> sheet retreat since the Little <span class="hlt">Ice</span> Age</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beitch, Marci J.</p> <p></p> <p>Late 20th century and 21st century satellite imagery of the perimeter of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) provide high resolution observations of the <span class="hlt">ice</span> sheet margins. Examining changes in <span class="hlt">ice</span> margin positions over time yield measurements of GrIS area change and rates of margin retreat. However, longer records of <span class="hlt">ice</span> sheet margin change are needed to establish more accurate predictions of the <span class="hlt">ice</span> sheet's future response to global conditions. In this study, the trimzone, the area of deglaciated terrain along the <span class="hlt">ice</span> sheet edge that lacks mature vegetation <span class="hlt">cover</span>, is used as a marker of the maximum extent of the <span class="hlt">ice</span> from its most recent major advance during the Little <span class="hlt">Ice</span> Age. We compile recently acquired Landsat ETM+ scenes <span class="hlt">covering</span> the perimeter of the GrIS on which we map area loss on land-, lake-, and marine-terminating margins. We measure an area loss of 13,327 +/- 830 km2, which corresponds to 0.8% shrinkage of the <span class="hlt">ice</span> sheet. This equates to an averaged horizontal retreat of 363 +/- 69 m across the entire GrIS margin. Mapping the areas exposed since the Little <span class="hlt">Ice</span> Age maximum, circa 1900 C.E., yields a century-scale rate of change. On average the <span class="hlt">ice</span> sheet lost an area of 120 +/- 16 km 2/yr, or retreated at a rate of 3.3 +/- 0.7 m/yr since the LIA maximum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040088835&hterms=photosynthesis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dphotosynthesis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040088835&hterms=photosynthesis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dphotosynthesis"><span>Thickness of tropical <span class="hlt">ice</span> and photosynthesis on a snowball Earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McKay, C. P.</p> <p>2000-01-01</p> <p>On a completely <span class="hlt">ice-covered</span> "snowball" Earth the thickness of <span class="hlt">ice</span> in the tropical regions would be limited by the sunlight penetrating into the <span class="hlt">ice</span> <span class="hlt">cover</span> and by the latent heat flux generated by freezing at the <span class="hlt">ice</span> bottom--the freezing rate would balance the sublimation rate from the top of the <span class="hlt">ice</span> <span class="hlt">cover</span>. Heat transfer models of the perennially <span class="hlt">ice-covered</span> Antarctic dry valley lakes applied to the snowball Earth indicate that the tropical <span class="hlt">ice</span> <span class="hlt">cover</span> would have a thickness of 10 m or less with a corresponding transmissivity of > 0.1%. This light level is adequate for photosynthesis and could explain the survival of the eukaryotic algae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11543492','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11543492"><span>Thickness of tropical <span class="hlt">ice</span> and photosynthesis on a snowball Earth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McKay, C P</p> <p>2000-07-15</p> <p>On a completely <span class="hlt">ice-covered</span> "snowball" Earth the thickness of <span class="hlt">ice</span> in the tropical regions would be limited by the sunlight penetrating into the <span class="hlt">ice</span> <span class="hlt">cover</span> and by the latent heat flux generated by freezing at the <span class="hlt">ice</span> bottom--the freezing rate would balance the sublimation rate from the top of the <span class="hlt">ice</span> <span class="hlt">cover</span>. Heat transfer models of the perennially <span class="hlt">ice-covered</span> Antarctic dry valley lakes applied to the snowball Earth indicate that the tropical <span class="hlt">ice</span> <span class="hlt">cover</span> would have a thickness of 10 m or less with a corresponding transmissivity of > 0.1%. This light level is adequate for photosynthesis and could explain the survival of the eukaryotic algae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4009872','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4009872"><span>Timescales of Growth Response of Microbial Mats to Environmental Change in an <span class="hlt">Ice-Covered</span> Antarctic Lake</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hawes, Ian; Sumner, Dawn Y.; Andersen, Dale T.; Jungblut, Anne D.; Mackey, Tyler J.</p> <p>2013-01-01</p> <p>Lake Vanda is a perennially <span class="hlt">ice-covered</span>, closed-basin lake in the McMurdo Dry Valleys, Antarctica. Laminated photosynthetic microbial mats <span class="hlt">cover</span> the floor of the lake from below the <span class="hlt">ice</span> <span class="hlt">cover</span> to >40 m depth. In recent decades, the water level of Lake Vanda has been rising, creating a “natural experiment” on development of mat communities on newly flooded substrates and the response of deeper mats to declining irradiance. Mats in recently flooded depths accumulate one lamina (~0.3 mm) per year and accrue ~0.18 µg chlorophyll-a cm−2 y−1. As they increase in thickness, vertical zonation becomes evident, with the upper 2-4 laminae forming an orange-brown zone, rich in myxoxanthophyll and dominated by intertwined Leptolyngbya trichomes. Below this, up to six phycobilin-rich green/pink-pigmented laminae form a subsurface zone, inhabited by Leptolyngbya, Oscillatoria and Phormidium morphotypes. Laminae continued to increase in thickness for several years after burial, and PAM fluorometry indicated photosynthetic potential in all pigmented laminae. At depths that have been submerged for >40 years, mats showed similar internal zonation and formed complex pinnacle structures that were only beginning to appear in shallower mats. Chlorophyll-a did not change over time and these mats appear to represent resource-limited “climax” communities. Acclimation of microbial mats to changing environmental conditions is a slow process, and our data show how legacy effects of past change persist into the modern community structure. PMID:24832656</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24832656','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24832656"><span>Timescales of growth response of microbial mats to environmental change in an <span class="hlt">ice-covered</span> antarctic lake.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hawes, Ian; Sumner, Dawn Y; Andersen, Dale T; Jungblut, Anne D; Mackey, Tyler J</p> <p>2013-01-25</p> <p>Lake Vanda is a perennially <span class="hlt">ice-covered</span>, closed-basin lake in the McMurdo Dry Valleys, Antarctica. Laminated photosynthetic microbial mats <span class="hlt">cover</span> the floor of the lake from below the <span class="hlt">ice</span> <span class="hlt">cover</span> to >40 m depth. In recent decades, the water level of Lake Vanda has been rising, creating a "natural experiment" on development of mat communities on newly flooded substrates and the response of deeper mats to declining irradiance. Mats in recently flooded depths accumulate one lamina (~0.3 mm) per year and accrue ~0.18 µg chlorophyll-a cm-2 y-1. As they increase in thickness, vertical zonation becomes evident, with the upper 2-4 laminae forming an orange-brown zone, rich in myxoxanthophyll and dominated by intertwined Leptolyngbya trichomes. Below this, up to six phycobilin-rich green/pink-pigmented laminae form a subsurface zone, inhabited by Leptolyngbya, Oscillatoria and Phormidium morphotypes. Laminae continued to increase in thickness for several years after burial, and PAM fluorometry indicated photosynthetic potential in all pigmented laminae. At depths that have been submerged for >40 years, mats showed similar internal zonation and formed complex pinnacle structures that were only beginning to appear in shallower mats. Chlorophyll-a did not change over time and these mats appear to represent resource-limited "climax" communities. Acclimation of microbial mats to changing environmental conditions is a slow process, and our data show how legacy effects of past change persist into the modern community structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000021334','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000021334"><span>Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Arctic Sea <span class="hlt">Ice</span> and Tundra</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arnold, G. Thomas; Tsay, Si-Chee; King, Michael D.; Li, Jason Y.; Soulen, Peter F.</p> <p>1999-01-01</p> <p>Angular distributions of spectral reflectance for four common arctic surfaces: snow-<span class="hlt">covered</span> sea <span class="hlt">ice</span>, melt-season sea <span class="hlt">ice</span>, snow-<span class="hlt">covered</span> tundra, and tundra shortly after snowmelt were measured using an aircraft <span class="hlt">based</span>, high angular resolution (1-degree) multispectral radiometer. Results indicate bidirectional reflectance is higher for snow-<span class="hlt">covered</span> sea <span class="hlt">ice</span> than melt-season sea <span class="hlt">ice</span> at all wavelengths between 0.47 and 2.3 pm, with the difference increasing with wavelength. Bidirectional reflectance of snow-<span class="hlt">covered</span> tundra is higher than for snow-free tundra for measurements less than 1.64 pm, with the difference decreasing with wavelength. Bidirectional reflectance patterns of all measured surfaces show maximum reflectance in the forward scattering direction of the principal plane, with identifiable specular reflection for the melt-season sea <span class="hlt">ice</span> and snow-free tundra cases. The snow-free tundra had the most significant backscatter, and the melt-season sea <span class="hlt">ice</span> the least. For sea <span class="hlt">ice</span>, bidirectional reflectance changes due to snowmelt were more significant than differences among the different types of melt-season sea <span class="hlt">ice</span>. Also the spectral-hemispherical (plane) albedo of each measured arctic surface was computed. Comparing measured nadir reflectance to albedo for sea <span class="hlt">ice</span> and snow-<span class="hlt">covered</span> tundra shows albedo underestimated 5-40%, with the largest bias at wavelengths beyond 1 pm. For snow-free tundra, nadir reflectance underestimates plane albedo by about 30-50%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41D0726M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41D0726M"><span>Characterizing Microbial Mat Morphology with Structure from Motion Techniques in <span class="hlt">Ice-Covered</span> Lake Joyce, McMurdo Dry Valleys, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mackey, T. J.; Leidman, S. Z.; Allen, B.; Hawes, I.; Lawrence, J.; Jungblut, A. D.; Krusor, M.; Coleman, L.; Sumner, D. Y.</p> <p>2015-12-01</p> <p>Structure from Motion (SFM) techniques can provide quantitative morphological documentation of otherwise inaccessible benthic ecosystems such as microbial mats in Lake Joyce, a perennially <span class="hlt">ice-covered</span> lake of the Antarctic McMurdo Dry Valleys (MDV). Microbial mats are a key ecosystem of MDV lakes, and diverse mat morphologies like pinnacles emerge from interactions among microbial behavior, mineralization, and environmental conditions. Environmental gradients can be isolated to test mat growth models, but assessment of mat morphology along these gradients is complicated by their inaccessibility: the Lake Joyce <span class="hlt">ice</span> <span class="hlt">cover</span> is 4-5 m thick, water depths containing diverse pinnacle morphologies are 9-14 m, and relevant mat features are cm-scale. In order to map mat pinnacle morphology in different sedimentary settings, we deployed drop cameras (SeaViewer and GoPro) through 29 GPS referenced drill holes clustered into six stations along a transect spanning 880 m. Once under the <span class="hlt">ice</span> <span class="hlt">cover</span>, a boom containing a second GoPro camera was unfurled and rotated to collect oblique images of the benthic mats within dm of the mat-water interface. This setup allowed imaging from all sides over a ~1.5 m diameter area of the lake bottom. Underwater lens parameters were determined for each camera in Agisoft Lens; images were reconstructed and oriented in space with the SFM software Agisoft Photoscan, using the drop camera axis of rotation as up. The reconstructions were compared to downward facing images to assess accuracy, and similar images of an object with known geometry provided a test for expected error in reconstructions. Downward facing images identify decreasing pinnacle abundance in higher sedimentation settings, and quantitative measurements of 3D reconstructions in KeckCAVES LidarViewer supplement these mat morphological facies with measurements of pinnacle height and orientation. Reconstructions also help isolate confounding variables for mat facies trends with measurements</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913097K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913097K"><span>Improved method for sea <span class="hlt">ice</span> age computation <span class="hlt">based</span> on combination of sea <span class="hlt">ice</span> drift and concentration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Korosov, Anton; Rampal, Pierre; Lavergne, Thomas; Aaboe, Signe</p> <p>2017-04-01</p> <p>Sea <span class="hlt">Ice</span> Age is one of the components of the Sea <span class="hlt">Ice</span> ECV as defined by the Global Climate Observing System (GCOS) [WMO, 2015]. It is an important climate indicator describing the sea <span class="hlt">ice</span> state in addition to sea <span class="hlt">ice</span> concentration (SIC) and thickness (SIT). The amount of old/thick <span class="hlt">ice</span> in the Arctic Ocean has been decreasing dramatically [Perovich et al. 2015]. Kwok et al. [2009] reported significant decline in the MYI share and consequent loss of thickness and therefore volume. Today, there is only one acknowledged sea <span class="hlt">ice</span> age climate data record [Tschudi, et al. 2015], <span class="hlt">based</span> on Maslanik et al. [2011] provided by National Snow and <span class="hlt">Ice</span> Data Center (NSIDC) [http://nsidc.org/data/docs/daac/nsidc0611-sea-<span class="hlt">ice</span>-age/]. The sea <span class="hlt">ice</span> age algorithm [Fowler et al., 2004] is using satellite-derived <span class="hlt">ice</span> drift for Lagrangian tracking of individual <span class="hlt">ice</span> parcels (12-km grid cells) defined by areas of sea <span class="hlt">ice</span> concentration > 15% [Maslanik et al., 2011], i.e. sea <span class="hlt">ice</span> extent, according to the NASA Team algorithm [Cavalieri et al., 1984]. This approach has several drawbacks. (1) Using sea <span class="hlt">ice</span> extent instead of sea <span class="hlt">ice</span> concentration leads to overestimation of the amount of older <span class="hlt">ice</span>. (2) The individual <span class="hlt">ice</span> parcels are not advected uniformly over (long) time. This leads to undersampling in areas of consistent <span class="hlt">ice</span> divergence. (3) The end product grid cells are assigned the age of the oldest <span class="hlt">ice</span> parcel within that cell, and the frequency distribution of the <span class="hlt">ice</span> age is not taken into account. In addition, the <span class="hlt">base</span> sea <span class="hlt">ice</span> drift product (https://nsidc.org/data/docs/daac/nsidc0116_icemotion.gd.html) is known to exhibit greatly reduced accuracy during the summer season [Sumata et al 2014, Szanyi, 2016] as it only relies on a combination of sea <span class="hlt">ice</span> drifter trajectories and wind-driven "free-drift" motion during summer. This results in a significant overestimate of old-<span class="hlt">ice</span> content, incorrect shape of the old-<span class="hlt">ice</span> pack, and lack of information about the <span class="hlt">ice</span> age distribution within the grid cells. We</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C33A0662C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C33A0662C"><span>Holocene history of North <span class="hlt">Ice</span> Cap, northwestern Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corbett, L. B.; Kelly, M. A.; Osterberg, E. C.; Axford, Y.; Bigl, M.; Roy, E. P.; Thompson, J. T.</p> <p>2013-12-01</p> <p>Although much research has focused on the past extents of the Greenland <span class="hlt">Ice</span> Sheet, less is known about the smaller <span class="hlt">ice</span> caps on Greenland and how they have evolved over time. These small <span class="hlt">ice</span> caps respond sensitively to summer temperatures and, to a lesser extent, winter precipitation, and provide valuable information about climatic conditions along the Greenland <span class="hlt">Ice</span> Sheet margins. Here, we investigate the Holocene history of North <span class="hlt">Ice</span> Cap (76°55'N 68°00'W), located in the Nunatarssuaq region near Thule, northwest Greenland. Our results are <span class="hlt">based</span> on glacial geomorphic mapping, 10Be dating, and analyses of sediment cores from a glacially fed lake. Fresh, unweathered and unvegetated boulders comprise moraines and drift that mark an extent of North <span class="hlt">Ice</span> Cap ~25 m outboard of the present <span class="hlt">ice</span> margin. It is likely that these deposits were formed during late Holocene time and we are currently employing 10Be surface exposure dating to examine this hypothesis. Just outboard of the fresh moraines and drift, boulders and bedrock show significant weathering and are <span class="hlt">covered</span> with lichen. <span class="hlt">Based</span> on glacial geomorphic mapping and detailed site investigations, including stone counts, we suggest that the weathered boulders and bedrock were once <span class="hlt">covered</span> by erosive Greenland <span class="hlt">Ice</span> Sheet flow from southeast to northwest over the Nunatarssuaq region. Five 10Be ages from the more weathered landscape only 100-200 m outboard of the modern North <span class="hlt">Ice</span> Cap margin are 52 and 53 ka (bedrock) and 16, 23, and 31 ka (boulders). These ages indicate that recent <span class="hlt">ice</span> <span class="hlt">cover</span> has likely been cold-<span class="hlt">based</span> and non-erosive, failing to remove inherited cosmogenic nuclides from previous periods of exposure, although the youngest boulder may provide a maximum limiting deglaciation age. Sediment cores collected from Delta Sø, a glacially-fed lake ~1.5 km outside of the modern North <span class="hlt">Ice</span> Cap margin, contain 130 cm of finely laminated sediments overlying coarse sands and glacial till. Radiocarbon ages from just above</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29621173','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29621173"><span>Statistical Analysis of SSMIS Sea <span class="hlt">Ice</span> Concentration Threshold at the Arctic Sea <span class="hlt">Ice</span> Edge during Summer <span class="hlt">Based</span> on MODIS and Ship-<span class="hlt">Based</span> Observational Data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ji, Qing; Li, Fei; Pang, Xiaoping; Luo, Cong</p> <p>2018-04-05</p> <p>The threshold of sea <span class="hlt">ice</span> concentration (SIC) is the basis for accurately calculating sea <span class="hlt">ice</span> extent <span class="hlt">based</span> on passive microwave (PM) remote sensing data. However, the PM SIC threshold at the sea <span class="hlt">ice</span> edge used in previous studies and released sea <span class="hlt">ice</span> products has not always been consistent. To explore the representable value of the PM SIC threshold corresponding on average to the position of the Arctic sea <span class="hlt">ice</span> edge during summer in recent years, we extracted sea <span class="hlt">ice</span> edge boundaries from the Moderate-resolution Imaging Spectroradiometer (MODIS) sea <span class="hlt">ice</span> product (MOD29 with a spatial resolution of 1 km), MODIS images (250 m), and sea <span class="hlt">ice</span> ship-<span class="hlt">based</span> observation points (1 km) during the fifth (CHINARE-2012) and sixth (CHINARE-2014) Chinese National Arctic Research Expeditions, and made an overlay and comparison analysis with PM SIC derived from Special Sensor Microwave Imager Sounder (SSMIS, with a spatial resolution of 25 km) in the summer of 2012 and 2014. Results showed that the average SSMIS SIC threshold at the Arctic sea <span class="hlt">ice</span> edge <span class="hlt">based</span> on <span class="hlt">ice</span>-water boundary lines extracted from MOD29 was 33%, which was higher than that of the commonly used 15% discriminant threshold. The average SIC threshold at sea <span class="hlt">ice</span> edge <span class="hlt">based</span> on <span class="hlt">ice</span>-water boundary lines extracted by visual interpretation from four scenes of the MODIS image was 35% when compared to the average value of 36% from the MOD29 extracted <span class="hlt">ice</span> edge pixels for the same days. The average SIC of 31% at the sea <span class="hlt">ice</span> edge points extracted from ship-<span class="hlt">based</span> observations also confirmed that choosing around 30% as the SIC threshold during summer is recommended for sea <span class="hlt">ice</span> extent calculations <span class="hlt">based</span> on SSMIS PM data. These results can provide a reference for further studying the variation of sea <span class="hlt">ice</span> under the rapidly changing Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850053019&hterms=sea+ice+albedo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsea%2Bice%2Balbedo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850053019&hterms=sea+ice+albedo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsea%2Bice%2Balbedo"><span>Summer Arctic sea <span class="hlt">ice</span> character from satellite microwave data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carsey, F. D.</p> <p>1985-01-01</p> <p>It is pointed out that Arctic sea <span class="hlt">ice</span> and its environment undergo a number of changes during the summer period. Some of these changes affect the <span class="hlt">ice</span> <span class="hlt">cover</span> properties and, in turn, their response to thermal and mechanical forcing throughout the year. The main objective of this investigation is related to the development of a method for estimating the areal coverage of exposed <span class="hlt">ice</span>, melt ponds, and leads, which are the basic surface variables determining the local surface albedo. The study is <span class="hlt">based</span> on data obtained in a field investigation conducted from Mould Bay (NWT), Nimbus 5 satellite data, and Seasat data. The investigation demonstrates that microwave data from satellites, especially microwave brightness temperature, provide good data for estimating important characteristics of summer sea <span class="hlt">ice</span> <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3654H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3654H"><span>Post-glacial variations of sea <span class="hlt">ice</span> <span class="hlt">cover</span> and river discharge in the western Laptev Sea (Arctic Ocean) - a high-resolution study over the last 18 ka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hörner, Tanja; Stein, Ruediger; Fahl, Kirsten</p> <p>2015-04-01</p> <p>Here, we provide a high-resolution reconstruction of sea-<span class="hlt">ice</span> <span class="hlt">cover</span> variations in the western Laptev Sea, a crucial area in terms of sea-<span class="hlt">ice</span> production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea <span class="hlt">Ice</span> Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-<span class="hlt">ice</span> algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-<span class="hlt">ice</span> <span class="hlt">cover</span> varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of <span class="hlt">ice</span>-rafted debris (IRD) interpreted as local <span class="hlt">ice</span>-cap expansions (Taldenkova et al. 2010), and sea <span class="hlt">ice</span> <span class="hlt">cover</span> distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea <span class="hlt">ice</span>: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of <span class="hlt">ice</span>-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3597251','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3597251"><span>Seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> as principal driver of spatial and temporal variation in depth extension and annual production of kelp in Greenland</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Krause-Jensen, Dorte; Marbà, Núria; Olesen, Birgit; Sejr, Mikael K; Christensen, Peter Bondo; Rodrigues, João; Renaud, Paul E; Balsby, Thorsten JS; Rysgaard, Søren</p> <p>2012-01-01</p> <p>We studied the depth distribution and production of kelp along the Greenland coast spanning Arctic to sub-Arctic conditions from 78 °N to 64 °N. This <span class="hlt">covers</span> a wide range of sea <span class="hlt">ice</span> conditions and water temperatures, with those presently realized in the south likely to move northwards in a warmer future. Kelp forests occurred along the entire latitudinal range, and their depth extension and production increased southwards presumably in response to longer annual <span class="hlt">ice</span>-free periods and higher water temperature. The depth limit of 10% kelp <span class="hlt">cover</span> was 9–14 m at the northernmost sites (77–78 °N) with only 94–133 <span class="hlt">ice</span>-free days per year, but extended to depths of 21–33 m further south (73 °N–64 °N) where >160 days per year were <span class="hlt">ice</span>-free, and annual production of Saccharina longicruris and S. latissima, measured as the size of the annual blade, ranged up to sevenfold among sites. The duration of the open-water period, which integrates light and temperature conditions on an annual basis, was the best predictor (relative to summer water temperature) of kelp production along the latitude gradient, explaining up to 92% of the variation in depth extension and 80% of the variation in kelp production. In a decadal time series from a high Arctic site (74 °N), inter-annual variation in sea <span class="hlt">ice</span> <span class="hlt">cover</span> also explained a major part (up to 47%) of the variation in kelp production. Both spatial and temporal data sets thereby support the prediction that northern kelps will play a larger role in the coastal marine ecosystem in a warmer future as the length of the open-water period increases. As kelps increase carbon-flow and habitat diversity, an expansion of kelp forests may exert cascading effects on the coastal Arctic ecosystem. PMID:28741817</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28741817','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28741817"><span>Seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> as principal driver of spatial and temporal variation in depth extension and annual production of kelp in Greenland.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krause-Jensen, Dorte; Marbà, Núria; Olesen, Birgit; Sejr, Mikael K; Christensen, Peter Bondo; Rodrigues, João; Renaud, Paul E; Balsby, Thorsten J S; Rysgaard, Søren</p> <p>2012-10-01</p> <p>We studied the depth distribution and production of kelp along the Greenland coast spanning Arctic to sub-Arctic conditions from 78 ºN to 64 ºN. This <span class="hlt">covers</span> a wide range of sea <span class="hlt">ice</span> conditions and water temperatures, with those presently realized in the south likely to move northwards in a warmer future. Kelp forests occurred along the entire latitudinal range, and their depth extension and production increased southwards presumably in response to longer annual <span class="hlt">ice</span>-free periods and higher water temperature. The depth limit of 10% kelp <span class="hlt">cover</span> was 9-14 m at the northernmost sites (77-78 ºN) with only 94-133 <span class="hlt">ice</span>-free days per year, but extended to depths of 21-33 m further south (73 ºN-64 ºN) where >160 days per year were <span class="hlt">ice</span>-free, and annual production of Saccharina longicruris and S. latissima, measured as the size of the annual blade, ranged up to sevenfold among sites. The duration of the open-water period, which integrates light and temperature conditions on an annual basis, was the best predictor (relative to summer water temperature) of kelp production along the latitude gradient, explaining up to 92% of the variation in depth extension and 80% of the variation in kelp production. In a decadal time series from a high Arctic site (74 ºN), inter-annual variation in sea <span class="hlt">ice</span> <span class="hlt">cover</span> also explained a major part (up to 47%) of the variation in kelp production. Both spatial and temporal data sets thereby support the prediction that northern kelps will play a larger role in the coastal marine ecosystem in a warmer future as the length of the open-water period increases. As kelps increase carbon-flow and habitat diversity, an expansion of kelp forests may exert cascading effects on the coastal Arctic ecosystem. © 2012 Blackwell Publishing Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28811530','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28811530"><span>Evidence for <span class="hlt">ice</span>-ocean albedo feedback in the Arctic Ocean shifting to a seasonal <span class="hlt">ice</span> zone.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kashiwase, Haruhiko; Ohshima, Kay I; Nihashi, Sohey; Eicken, Hajo</p> <p>2017-08-15</p> <p><span class="hlt">Ice</span>-albedo feedback due to the albedo contrast between water and <span class="hlt">ice</span> is a major factor in seasonal sea <span class="hlt">ice</span> retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal <span class="hlt">ice</span> <span class="hlt">cover</span>. However, quantitative evaluation of such feedbacks is still insufficient. Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea <span class="hlt">ice</span> retreat. Analyses of satellite data (1979-2014) and a simplified <span class="hlt">ice</span>-upper ocean coupled model reveal that divergent <span class="hlt">ice</span> motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea <span class="hlt">ice</span> anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile <span class="hlt">ice</span> <span class="hlt">cover</span>, which can partly explain the recent drastic <span class="hlt">ice</span> reduction in the Arctic Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2629232','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2629232"><span>Nonlinear threshold behavior during the loss of Arctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Eisenman, I.; Wettlaufer, J. S.</p> <p>2009-01-01</p> <p>In light of the rapid recent retreat of Arctic sea <span class="hlt">ice</span>, a number of studies have discussed the possibility of a critical threshold (or “tipping point”) beyond which the ice–albedo feedback causes the <span class="hlt">ice</span> <span class="hlt">cover</span> to melt away in an irreversible process. The focus has typically been centered on the annual minimum (September) <span class="hlt">ice</span> <span class="hlt">cover</span>, which is often seen as particularly susceptible to destabilization by the ice–albedo feedback. Here, we examine the central physical processes associated with the transition from <span class="hlt">ice-covered</span> to <span class="hlt">ice</span>-free Arctic Ocean conditions. We show that although the ice–albedo feedback promotes the existence of multiple <span class="hlt">ice-cover</span> states, the stabilizing thermodynamic effects of sea <span class="hlt">ice</span> mitigate this when the Arctic Ocean is <span class="hlt">ice</span> <span class="hlt">covered</span> during a sufficiently large fraction of the year. These results suggest that critical threshold behavior is unlikely during the approach from current perennial sea-<span class="hlt">ice</span> conditions to seasonally <span class="hlt">ice</span>-free conditions. In a further warmed climate, however, we find that a critical threshold associated with the sudden loss of the remaining wintertime-only sea <span class="hlt">ice</span> <span class="hlt">cover</span> may be likely. PMID:19109440</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C13E0656L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C13E0656L"><span>Long-Endurance, <span class="hlt">Ice</span>-capable Autonomous Seagliders</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, C. M.; Gobat, J. I.; Shilling, G.; Curry, B.</p> <p>2012-12-01</p> <p>Autonomous Seagliders capable of extended (many months) operation in <span class="hlt">ice-covered</span> waters have been developed and successfully employed as part of the US Arctic Observing Network. Seagliders operate routinely in lower-latitude oceans for periods of up to 9 months to provide persistent sampling in difficult, remote conditions, including strong boundary currents and harsh wintertime subpolar seas. The Arctic Observing Network calls for sustained occupation of key sections within the Arctic Ocean and across the critical gateways that link the Arctic to lower-latitude oceans, motivating the extension of glider technologies to permit operation in <span class="hlt">ice-covered</span> waters. When operating in open water, gliders rely on GPS for navigation and Iridium satellite phones for data and command telemetry. <span class="hlt">Ice</span> <span class="hlt">cover</span> blocks access to the sea surface and thus prevents gliders from using these critical services. When operating under <span class="hlt">ice</span>, <span class="hlt">ice</span>-capable Seagliders instead navigate by trilateration from an array of RAFOS acoustic sound sources and employ advanced autonomy to make mission-critical decisions (previously the realm of the human pilot) and identify and exploit leads in the <span class="hlt">ice</span> to allow intermittent communication through Iridium. Davis Strait, one of the two primary pathways through which Arctic waters exit into the subpolar North Atlantic, provided a convenient site for development of <span class="hlt">ice</span>-capable Seagliders at a location where the resulting measurements could greatly augment the existing observing system. Initial testing of 780 Hz RAFOS sources in Davis Strait, substantiated by the performance of the operational array, indicates effective ranges of 100-150 km in <span class="hlt">ice-covered</span> waters. Surface ducting and reflection off the <span class="hlt">ice</span> bottom significantly degrade the range from the 500+ km expected in <span class="hlt">ice</span>-free conditions. Comparisons between GPS and acoustically-derived positions collected during operations in <span class="hlt">ice</span>-free conditions suggest 1-2 km uncertainty in the acoustically-derived positions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.3986L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.3986L"><span>Long-Endurance, <span class="hlt">Ice</span>-capable Autonomous Seagliders</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Craig; Gobat, Jason; Shilling, Geoff; Curry, Beth</p> <p>2013-04-01</p> <p>Autonomous Seagliders capable of extended (many months) operation in <span class="hlt">ice-covered</span> waters have been developed and successfully employed as part of the US Arctic Observing Network. Seagliders operate routinely in lower-latitude oceans for periods of up to 9 months to provide persistent sampling in difficult, remote conditions, including strong boundary currents and harsh wintertime subpolar seas. The Arctic Observing Network calls for sustained occupation of key sections within the Arctic Ocean and across the critical gateways that link the Arctic to lower-latitude oceans, motivating the extension of glider technologies to permit operation in <span class="hlt">ice-covered</span> waters. When operating in open water, gliders rely on GPS for navigation and Iridium satellite phones for data and command telemetry. <span class="hlt">Ice</span> <span class="hlt">cover</span> blocks access to the sea surface and thus prevents gliders from using these critical services. When operating under <span class="hlt">ice</span>, <span class="hlt">ice</span>-capable Seagliders instead navigate by trilateration from an array of RAFOS acoustic sound sources and employ advanced autonomy to make mission-critical decisions (previously the realm of the human pilot) and identify and exploit leads in the <span class="hlt">ice</span> to allow intermittent communication through Iridium. Davis Strait, one of the two primary pathways through which Arctic waters exit into the subpolar North Atlantic, provided a convenient site for development of <span class="hlt">ice</span>-capable Seagliders at a location where the resulting measurements could greatly augment the existing observing system. Initial testing of 780 Hz RAFOS sources in Davis Strait, substantiated by the performance of the operational array, indicates effective ranges of 100-150 km in <span class="hlt">ice-covered</span> waters. Surface ducting and reflection off the <span class="hlt">ice</span> bottom significantly degrade the range from the 500+ km expected in <span class="hlt">ice</span>-free conditions. Comparisons between GPS and acoustically-derived positions collected during operations in <span class="hlt">ice</span>-free conditions suggest 1-2 km uncertainty in the acoustically-derived positions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA264326','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA264326"><span>The Use of Satellite Observations in <span class="hlt">Ice</span> <span class="hlt">Cover</span> Simulations</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1992-01-01</p> <p>Io rmotions have been used to map upper-level winds over polar diagnose the origins of a large area of reduced <span class="hlt">ice</span> ,,ncfl.’c regions (Turner and...was motivated by the availability of coverage in the Arctic. Also shown are November-April s-ver!,_- the multiyear <span class="hlt">ice</span> concentrations derived from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120006699','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120006699"><span>Wheel-<span class="hlt">Based</span> <span class="hlt">Ice</span> Sensors for Road Vehicles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arndt, G. Dickey; Fink, Patrick W.; Ngo, Phong H.; Carl, James R.</p> <p>2011-01-01</p> <p>Wheel-<span class="hlt">based</span> sensors for detection of <span class="hlt">ice</span> on roads and approximate measurement of the thickness of the <span class="hlt">ice</span> are under development. These sensors could be used to alert drivers to hazardous local <span class="hlt">icing</span> conditions in real time. In addition, local <span class="hlt">ice</span>-thickness measurements by these sensors could serve as guidance for the minimum amount of sand and salt required to be dispensed locally onto road surfaces to ensure safety, thereby helping road crews to utilize their total supplies of sand and salt more efficiently. Like some aircraft wing-surface <span class="hlt">ice</span> sensors described in a number of previous NASA Tech Briefs articles, the wheelbased <span class="hlt">ice</span> sensors are <span class="hlt">based</span>, variously, on measurements of changes in capacitance and/or in radio-frequency impedance as affected by <span class="hlt">ice</span> on surfaces. In the case of <span class="hlt">ice</span> on road surfaces, the measurable changes in capacitance and/or impedance are attributable to differences among the electric permittivities of air, <span class="hlt">ice</span>, water, concrete, and soil. In addition, a related phenomenon that can be useful for distinguishing between <span class="hlt">ice</span> and water is a specific transition in the permittivity of <span class="hlt">ice</span> at a temperature- dependent frequency. This feature also provides a continuous calibration of the sensor to allow for changing road conditions. Several configurations of wheel-<span class="hlt">based</span> <span class="hlt">ice</span> sensors are under consideration. For example, in a simple two-electrode capacitor configuration, one of the electrodes would be a circumferential electrode within a tire, and the ground would be used as the second electrode. Optionally, the steel belts that are already standard parts of many tires could be used as the circumferential electrodes. In another example (see figure), multiple electrodes would be embedded in rubber between the steel belt and the outer tire surface. These electrodes would be excited in alternating polarities at one or more suitable audio or radio frequencies to provide nearly continuous monitoring of the road surface under the tire. In still another</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25429795','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25429795"><span>The emergence of modern sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Arctic Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Knies, Jochen; Cabedo-Sanz, Patricia; Belt, Simon T; Baranwal, Soma; Fietz, Susanne; Rosell-Melé, Antoni</p> <p>2014-11-28</p> <p>Arctic sea <span class="hlt">ice</span> coverage is shrinking in response to global climate change and summer <span class="hlt">ice</span>-free conditions in the Arctic Ocean are predicted by the end of the century. The validity of this prediction could potentially be tested through the reconstruction of the climate of the Pliocene epoch (5.33-2.58 million years ago), an analogue of a future warmer Earth. Here we show that, in the Eurasian sector of the Arctic Ocean, <span class="hlt">ice</span>-free conditions prevailed in the early Pliocene until sea <span class="hlt">ice</span> expanded from the central Arctic Ocean for the first time ca. 4 million years ago. Amplified by a rise in topography in several regions of the Arctic and enhanced freshening of the Arctic Ocean, sea <span class="hlt">ice</span> expanded progressively in response to positive <span class="hlt">ice</span>-albedo feedback mechanisms. Sea <span class="hlt">ice</span> reached its modern winter maximum extension for the first time during the culmination of the Northern Hemisphere glaciation, ca. 2.6 million years ago.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C43D..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C43D..07S"><span>Supraglacial lakes on Himalayan debris-<span class="hlt">covered</span> glacier (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakai, A.; Fujita, K.</p> <p>2013-12-01</p> <p>Debris-<span class="hlt">covered</span> glaciers are common in many of the world's mountain ranges, including in the Himalayas. Himalayan debris-<span class="hlt">covered</span> glacier also contain abundant glacial lakes, including both proglacial and supraglacial types. We have revealed that heat absorption through supraglacial lakes was about 7 times greater than that averaged over the whole debris-<span class="hlt">covered</span> zone. The heat budget analysis elucidated that at least half of the heat absorbed through the water surface was released with water outflow from the lakes, indicating that the warm water enlarge englacial conduits and produce internal ablation. We observed some portions at debris-<span class="hlt">covered</span> area has caved at the end of melting season, and <span class="hlt">ice</span> cliff has exposed at the side of depression. Those depression has suggested that roof of expanded water channels has collapsed, leading to the formation of <span class="hlt">ice</span> cliffs and new lakes, which would accelerate the ablation of debris-<span class="hlt">covered</span> glaciers. Almost glacial lakes on the debris-<span class="hlt">covered</span> glacier are partially surrounded by <span class="hlt">ice</span> cliffs. We observed that relatively small lakes had non-calving, whereas, calving has occurred at supraglacial lakes with fetch larger than 80 m, and those lakes expand rapidly. In the Himalayas, thick sediments at the lake bottom insulates glacier <span class="hlt">ice</span> and lake water, then the lake water tends to have higher temperature (2-4 degrees C). Therefore, thermal undercutting at <span class="hlt">ice</span> cliff is important for calving processes in the glacial lake expansion. We estimated and subaqueous <span class="hlt">ice</span> melt rates during the melt and freeze seasons under simple geomorphologic conditions. In particular, we focused on valley wind-driven water currents in various fetches during the melt season. Our results demonstrate that the subaqueous <span class="hlt">ice</span> melt rate exceeds the <span class="hlt">ice</span>-cliff melt rate above the water surface when the fetch is larger than 20 m with the water temperature of 2-4 degrees C. Calculations suggest that onset of calving due to thermal undercutting is controlled by water</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..143..133H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..143..133H"><span>Post-glacial variability of sea <span class="hlt">ice</span> <span class="hlt">cover</span>, river run-off and biological production in the western Laptev Sea (Arctic Ocean) - A high-resolution biomarker study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.</p> <p>2016-07-01</p> <p>Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea <span class="hlt">ice</span> <span class="hlt">cover</span> (IP25), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly <span class="hlt">covered</span> with permanent sea <span class="hlt">ice</span>. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea <span class="hlt">ice</span> <span class="hlt">cover</span> characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7-12.9 ka). Prominent peaks of the DIP25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea <span class="hlt">ice</span> conditions with strongest <span class="hlt">ice</span>-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9-11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea <span class="hlt">ice</span> proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea <span class="hlt">ice</span> coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea <span class="hlt">ice</span> conditions on the Laptev Sea shelf under modern sea level</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=kelp&id=EJ335092','ERIC'); return false;" href="https://eric.ed.gov/?q=kelp&id=EJ335092"><span>Sea <span class="hlt">Ice</span> and Oceanographic Conditions.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Oceanus, 1986</p> <p>1986-01-01</p> <p>The coastal waters of the Beaufort Sea are <span class="hlt">covered</span> with <span class="hlt">ice</span> three-fourths of the year. These waters (during winter) are discussed by considering: consolidation of coastal <span class="hlt">ice</span>; under-<span class="hlt">ice</span> water; brine circulation; biological energy; life under the <span class="hlt">ice</span> (including kelp and larger animals); food chains; and <span class="hlt">ice</span> break-up. (JN)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1823S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1823S"><span>Mapping and assessing variability in the Antarctic marginal <span class="hlt">ice</span> zone, pack <span class="hlt">ice</span> and coastal polynyas in two sea <span class="hlt">ice</span> algorithms with implications on breeding success of snow petrels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, Julienne C.; Jenouvrier, Stephanie; Campbell, G. Garrett; Barbraud, Christophe; Delord, Karine</p> <p>2016-08-01</p> <p>Sea <span class="hlt">ice</span> variability within the marginal <span class="hlt">ice</span> zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore, mapping their spatial extent as well as seasonal and interannual variability is essential for understanding how current and future changes in these biologically active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of MIZ, consolidated pack <span class="hlt">ice</span> and coastal polynyas in the total Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> may also help to shed light on the factors contributing towards recent expansion of the Antarctic <span class="hlt">ice</span> <span class="hlt">cover</span> in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent record for assessing the proportion of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> that is <span class="hlt">covered</span> by each of these <span class="hlt">ice</span> categories. However, estimates of the amount of MIZ, consolidated pack <span class="hlt">ice</span> and polynyas depend strongly on which sea <span class="hlt">ice</span> algorithm is used. This study uses two popular passive microwave sea <span class="hlt">ice</span> algorithms, the NASA Team and Bootstrap, and applies the same thresholds to the sea <span class="hlt">ice</span> concentrations to evaluate the distribution and variability in the MIZ, the consolidated pack <span class="hlt">ice</span> and coastal polynyas. Results reveal that the seasonal cycle in the MIZ and pack <span class="hlt">ice</span> is generally similar between both algorithms, yet the NASA Team algorithm has on average twice the MIZ and half the consolidated pack <span class="hlt">ice</span> area as the Bootstrap algorithm. Trends also differ, with the Bootstrap algorithm suggesting statistically significant trends towards increased pack <span class="hlt">ice</span> area and no statistically significant trends in the MIZ. The NASA Team algorithm on the other hand indicates statistically significant positive trends in the MIZ during spring. Potential coastal polynya area and amount of broken <span class="hlt">ice</span> within the consolidated <span class="hlt">ice</span> pack are also larger in the NASA Team algorithm. The timing of maximum polynya area may differ by as much as 5 months between algorithms. These</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26132925','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26132925"><span>Hg Stable Isotope Time Trend in Ringed Seals Registers Decreasing Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> in the Alaskan Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Masbou, Jérémy; Point, David; Sonke, Jeroen E; Frappart, Frédéric; Perrot, Vincent; Amouroux, David; Richard, Pierre; Becker, Paul R</p> <p>2015-08-04</p> <p>Decadal time trends of mercury (Hg) concentrations in Arctic biota suggest that anthropogenic Hg is not the single dominant factor modulating Hg exposure to Arctic wildlife. Here, we present Hg speciation (monomethyl-Hg) and stable isotopic composition (C, N, Hg) of 53 Alaskan ringed seal liver samples <span class="hlt">covering</span> a period of 14 years (1988-2002). In vivo metabolic effects and foraging ecology explain most of the observed 1.6 ‰ variation in liver δ(202)Hg, but not Δ(199)Hg. Ringed seal habitat use and migration were the most likely factors explaining Δ(199)Hg variations. Average Δ(199)Hg in ringed seal liver samples from Barrow increased significantly from +0.38 ± 0.08‰ (±SE, n = 5) in 1988 to +0.59 ± 0.07‰ (±SE, n = 7) in 2002 (4.1 ± 1.2% per year, p < 0.001). Δ(199)Hg in marine biological tissues is thought to reflect marine Hg photochemistry before biouptake and bioaccumulation. A spatiotemporal analysis of sea <span class="hlt">ice</span> <span class="hlt">cover</span> that accounts for the habitat of ringed seals suggests that the observed increase in Δ(199)Hg may have been caused by the progressive summer sea <span class="hlt">ice</span> disappearance between 1988 and 2002. While changes in seal liver Δ(199)Hg values suggests a mild sea <span class="hlt">ice</span> control on marine MMHg breakdown, the effect is not large enough to induce measurable HgT changes in biota. This suggests that Hg trends in biota in the context of a warming Arctic are likely controlled by other processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C21A0959M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C21A0959M"><span>Affects of Changes in Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span> on Bowhead Whales and Subsistence Whaling in the Western Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moore, S.; Suydam, R.; Overland, J.; Laidre, K.; George, J.; Demaster, D.</p> <p>2004-12-01</p> <p>Global warming may disproportionately affect Arctic marine mammals and disrupt traditional subsistence hunting activities. <span class="hlt">Based</span> upon analyses of a 24-year time series (1979-2002) of satellite-derived sea <span class="hlt">ice</span> <span class="hlt">cover</span>, we identified significant positive trends in the amount of open-water in three large and five small-scale regions in the western Arctic, including habitats where bowhead whales (Balaena mysticetus) feed or are suspected to feed. Bowheads are the only mysticete whale endemic to the Arctic and a cultural keystone species for Native peoples from northwestern Alaska and Chukotka, Russia. While copepods (Calanus spp.) are a mainstay of the bowhead diet, prey sampling conducted in the offshore region of northern Chukotka and stomach contents from whales harvested offshore of the northern Alaskan coast indicate that euphausiids (Thysanoessa spp.) advected from the Bering Sea are also common prey in autumn. Early departure of sea <span class="hlt">ice</span> has been posited to control availability of zooplankton in the southeastern Bering Sea and in the Cape Bathurst polynya in the southeastern Canadian Beaufort Sea, with maximum secondary production associated with a late phytoplankton bloom in insolatoin-stratified open water. While it is unclear if declining sea-<span class="hlt">ice</span> has directly affected production or advection of bowhead prey, an extension of the open-water season increases opportunities for Native subsistence whaling in autumn. Therefore, bowhead whales may provide a nexus for simultaneous exploration of the effects sea <span class="hlt">ice</span> reduction on pagophillic marine mammals and on the social systems of the subsistence hunting community in the western Arctic. The NOAA/Alaska Fisheries Science Center and NSB/Department of Wildlife Management will investigate bowhead whale stock identity, seasonal distribution and subsistence use patterns during the International Polar Year, as an extension of research planned for 2005-06. This research is in response to recommendations from the Scientific</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940026115','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940026115"><span>The role of sea <span class="hlt">ice</span> dynamics in global climate change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hibler, William D., III</p> <p>1992-01-01</p> <p>The topics <span class="hlt">covered</span> include the following: general characteristics of sea <span class="hlt">ice</span> drift; sea <span class="hlt">ice</span> rheology; <span class="hlt">ice</span> thickness distribution; sea <span class="hlt">ice</span> thermodynamic models; equilibrium thermodynamic models; effect of internal brine pockets and snow <span class="hlt">cover</span>; model simulations of Arctic Sea <span class="hlt">ice</span>; and sensitivity of sea <span class="hlt">ice</span> models to climate change.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.3652B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.3652B"><span>The current evolution of complex high mountain debris-<span class="hlt">covered</span> glacier systems and its relation with ground <span class="hlt">ice</span> nature and distribution: the case of Rognes and Pierre Ronde area (Mont-Blanc range, France).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bosson, Jean-Baptiste; Lambiel, Christophe</p> <p>2014-05-01</p> <p>The current climate forcing, through negative glacier mass balance and rockfall intensification, is leading to the rapid burring of many small glacier systems. When the debris mantle exceeds some centimeters of thickness, the climate control on <span class="hlt">ice</span> melt is mitigated and delayed. As well, debris-<span class="hlt">covered</span> glaciers respond to climate forcing in a complex way. This situation is emphasised in high mountain environments, where topo-climatic conditions, such as cold temperatures, amount of solid precipitation, duration of snow <span class="hlt">cover</span>, nebulosity or shadow effect of rockwalls, limit the influence of rising air temperatures in the ground. Beside, due to Holocene climate history, glacier-permafrost interactions are not rare within the periglacial belt. Glacier recurrence may have removed and assimilated former <span class="hlt">ice</span>-cemented sediments, the negative mass balance may have led to the formation of <span class="hlt">ice</span>-cored rock glaciers and neopermafrost may have formed recently under cold climate conditions. Hence, in addition to sedimentary <span class="hlt">ice</span>, high mountain debris-<span class="hlt">covered</span> glacier systems can contain interstitial magmatic <span class="hlt">ice</span>. Especially because of their position at the top of alpine cascade systems and of the amount of water and (unconsolidated) sediment involved, it is important to understand and anticipate the evolution of these complex landforms. Due to the continuous and thick debris mantle and to the common existence of dead <span class="hlt">ice</span> in deglaciated areas, the current extent of debris-<span class="hlt">covered</span> glacier can be difficult to point out. Thus, the whole system, according to Little <span class="hlt">Ice</span> Age (LIA) extent, has sometimes to be investigated to understand the current response of glacier systems to the climate warming. In this context, two neighbouring sites, Rognes and Pierre Ronde systems (45°51'38''N, 6°48'40''E; 2600-3100m a.s.l), have been studied since 2011. These sites are almost completely debris-<span class="hlt">covered</span> and only few <span class="hlt">ice</span> outcrops in the upper slopes still witness the existence of former glaciers</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....12815H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....12815H"><span>Data sets for snow <span class="hlt">cover</span> monitoring and modelling from the National Snow and <span class="hlt">Ice</span> Data Center</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holm, M.; Daniels, K.; Scott, D.; McLean, B.; Weaver, R.</p> <p>2003-04-01</p> <p>A wide range of snow <span class="hlt">cover</span> monitoring and modelling data sets are pending or are currently available from the National Snow and <span class="hlt">Ice</span> Data Center (NSIDC). In-situ observations support validation experiments that enhance the accuracy of remote sensing data. In addition, remote sensing data are available in near-real time, providing coarse-resolution snow monitoring capability. Time series data beginning in 1966 are valuable for modelling efforts. NSIDC holdings include SMMR and SSM/I snow <span class="hlt">cover</span> data, MODIS snow <span class="hlt">cover</span> extent products, in-situ and satellite data collected for NASA's recent Cold Land Processes Experiment, and soon-to-be-released ASMR-E passive microwave products. The AMSR-E and MODIS sensors are part of NASA's Earth Observing System flying on the Terra and Aqua satellites Characteristics of these NSIDC-held data sets, appropriateness of products for specific applications, and data set access and availability will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060028450','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060028450"><span>Enhancing <span class="hlt">Icing</span> Training for Pilots Through Web-<span class="hlt">Based</span> Multimedia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fletcher, William; Nolan, Gary; Adanich, Emery; Bond, Thomas H.</p> <p>2006-01-01</p> <p>The Aircraft <span class="hlt">Icing</span> Project of the NASA Aviation Safety Program has developed a number of in-flight <span class="hlt">icing</span> education and training aids designed to increase pilot awareness about the hazards associated with various <span class="hlt">icing</span> conditions. The challenges and advantages of transitioning these <span class="hlt">icing</span> training materials to a Web-<span class="hlt">based</span> delivery are discussed. Innovative Web-<span class="hlt">based</span> delivery devices increased course availability to pilots and dispatchers while increasing course flexibility and utility. These courses are customizable for both self-directed and instructor-led learning. Part of our goal was to create training materials with enough flexibility to enable Web-<span class="hlt">based</span> delivery and downloadable portability while maintaining a rich visual multimedia-<span class="hlt">based</span> learning experience. Studies suggest that using visually <span class="hlt">based</span> multimedia techniques increases the effectiveness of <span class="hlt">icing</span> training materials. This paper describes these concepts, gives examples, and discusses the transitional challenges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018LPICo2085.6017L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018LPICo2085.6017L"><span><span class="hlt">Ice-Covered</span> Chemosynthetic Ecosystems: Mineral Availability and MicroBiological Accessibility (<span class="hlt">ICE</span>-MAMBA)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, P. A.; Dyar, M. D.; Sklute, E. C.; Taylor, E. C.; Mikucki, J. A.</p> <p>2018-05-01</p> <p>The <span class="hlt">ICE</span>-MAMBA project is a collaborative effort consisting of three overlapping and integrated multidisciplinary studies to examine various molecular, mineralogical and metabolic biosignatures in cold, briny discharges from Blood Falls, Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70175509','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70175509"><span>Water, <span class="hlt">ice</span> and mud: Lahars and lahar hazards at <span class="hlt">ice</span>- and snow-clad volcanoes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Waythomas, Christopher F.</p> <p>2014-01-01</p> <p>Large-volume lahars are significant hazards at <span class="hlt">ice</span> and snow <span class="hlt">covered</span> volcanoes. Hot eruptive products produced during explosive eruptions can generate a substantial volume of melt water that quickly evolves into highly mobile flows of <span class="hlt">ice</span>, sediment and water. At present it is difficult to predict the size of lahars that can form at <span class="hlt">ice</span> and snow <span class="hlt">covered</span> volcanoes due to their complex flow character and behaviour. However, advances in experiments and numerical approaches are producing new conceptual models and new methods for hazard assessment. Eruption triggered lahars that are <span class="hlt">ice</span>-dominated leave behind thin, almost unrecognizable sedimentary deposits, making them likely to be under-represented in the geological record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70018516','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70018516"><span>Effects of glacial meltwater inflows and moat freezing on mixing in an <span class="hlt">ice-covered</span> antarctic lake as interpreted from stable isotope and tritium distributions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Miller, L.G.; Aiken, G.R.</p> <p>1996-01-01</p> <p>Perennially <span class="hlt">ice-covered</span> lakes in the McMurdo Dry Valleys have risen several meters over the past two decades due to climatic warming and increased glacial meltwater inflow. To elucidate the hydrologic responses to changing climate and the effects on lake mixing processes we measured the stable isotope (??18O and ??D) and tritium concentrations of water and <span class="hlt">ice</span> samples collected in the Lake Fryxell watershed from 1987 through 1990. Stable isotope enrichment resulted from evaporation in stream and moat samples and from sublimation in surface lake-<span class="hlt">ice</span> samples. Tritium enrichment resulted from exchange with the postnuclear atmosphere in stream and moat samples. Rapid injection of tritiated water into the upper water column of the make and incorporation of this water into the <span class="hlt">ice</span> <span class="hlt">cover</span> resulted in uniformly elevated tritium contents (> 3.0 TU) in these reservoirs. Tritium was also present in deep water, suggesting that a component of bottom water was recently at the surface. During summer, melted lake <span class="hlt">ice</span> and stream water forms the moat. Water excluded from <span class="hlt">ice</span> formation during fall moat freezing (enriched in solutes and tritium, and depleted in 18O and 2H relative to water below 15-m depth) may sink as density currents to the bottom of the lake. Seasonal lake circulation, in response to climate-driven surface inflow, is therefore responsible for the distribution of both water isotopes and dissolved solutes in Lake Fryxell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814695S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814695S"><span>N-<span class="hlt">ICE</span>2015: Multi-disciplinary study of the young sea <span class="hlt">ice</span> system north of Svalbard from winter to summer.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steen, Harald; Granskog, Mats; Assmy, Philipp; Duarte, Pedro; Hudson, Stephen; Gerland, Sebastian; Spreen, Gunnar; Smedsrud, Lars H.</p> <p>2016-04-01</p> <p>The Arctic Ocean is shifting to a new regime with a thinner and smaller sea-<span class="hlt">ice</span> area <span class="hlt">cover</span>. Until now, winter sea <span class="hlt">ice</span> extent has changed less than during summer, as the heat loss to the atmosphere during autumn and winter is large enough form an <span class="hlt">ice</span> <span class="hlt">cover</span> in most regions. The insulating snow <span class="hlt">cover</span> also heavily influences the winter <span class="hlt">ice</span> growth. Consequently, the older, thicker multi-year sea <span class="hlt">ice</span> has been replace by a younger and thinner sea. These large changes in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> may have dramatic consequences for ecosystems, energy fluxes and ultimately atmospheric circulation and the Northern Hemisphere climate. To study the effects of the changing Arctic the Norwegian Polar Institute, together with national and international partners, launched from January 11 to June 24, 2015 the Norwegian Young Sea <span class="hlt">ICE</span> cruise 2015 (N-<span class="hlt">ICE</span>2015). N-<span class="hlt">ICE</span>2015 was a multi-disciplinary cruise aimed at simultaneously studying the effect of the Arctic Ocean changes in the sea <span class="hlt">ice</span>, the atmosphere, in radiation, in ecosystems. as well as water chemistry. R/V Lance was frozen into the drift <span class="hlt">ice</span> north of Svalbard at about N83 E25 and drifted passively southwards with the <span class="hlt">ice</span> until she was broken loose. When she was loose, R/V Lance was brought back north to a similar starting position. While fast in the <span class="hlt">ice</span>, she served as a living and working platform for 100 scientist and engineers from 11 countries. One aim of N-<span class="hlt">ICE</span>2015 is to present a comprehensive data-set on the first year <span class="hlt">ice</span> dominated system available for the scientific community describing the state and changes of the Arctic sea <span class="hlt">ice</span> system from freezing to melt. Analyzing the data is progressing and some first results will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JGR....9515959H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JGR....9515959H"><span>One hundred years of Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> variations as simulated by a one-dimensional, <span class="hlt">ice</span>-ocean model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hakkinen, S.; Mellor, G. L.</p> <p>1990-09-01</p> <p>A one-dimensional <span class="hlt">ice</span>-ocean model consisting of a second moment, turbulent closure, mixed layer model and a three-layer snow-<span class="hlt">ice</span> model has been applied to the simulation of Arctic <span class="hlt">ice</span> mass and mixed layer properties. The results for the climatological seasonal cycle are discussed first and include the salt and heat balance in the upper ocean. The coupled model is then applied to the period 1880-1985, using the surface air temperature fluctuations from Hansen et al. (1983) and from Wigley et al. (1981). The analysis of the simulated large variations of the Arctic <span class="hlt">ice</span> mass during this period (with similar changes in the mixed layer salinity) shows that the variability in the summer melt determines to a high degree the variability in the average <span class="hlt">ice</span> thickness. The annual oceanic heat flux from the deep ocean and the maximum freezing rate and associated nearly constant minimum surface salinity flux did not vary significantly interannually. This also implies that the oceanic influence on the Arctic <span class="hlt">ice</span> mass is minimal for the range of atmospheric variability tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009599','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009599"><span>Field and Satellite Observations of the Formation and Distribution of Arctic Atmospheric Bromine Above a Rejuvenated Sea <span class="hlt">Ice</span> <span class="hlt">Cover</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, Son V.; Rigor, Ignatius G.; Richter, Andreas; Burrows, John P.; Shepson, Paul B.; Bottenheim, Jan; Barber, David G.; Steffen, Alexandra; Latonas, Jeff; Wang, Feiyue; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20120009599'); toggleEditAbsImage('author_20120009599_show'); toggleEditAbsImage('author_20120009599_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20120009599_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20120009599_hide"></p> <p>2012-01-01</p> <p>Recent drastic reduction of the older perennial sea <span class="hlt">ice</span> in the Arctic Ocean has resulted in a vast expansion of younger and saltier seasonal sea <span class="hlt">ice</span>. This increase in the salinity of the overall <span class="hlt">ice</span> <span class="hlt">cover</span> could impact tropospheric chemical processes. Springtime perennial <span class="hlt">ice</span> extent in 2008 and 2009 broke the half-century record minimum in 2007 by about one million km2. In both years seasonal <span class="hlt">ice</span> was dominant across the Beaufort Sea extending to the Amundsen Gulf, where significant field and satellite observations of sea <span class="hlt">ice</span>, temperature, and atmospheric chemicals have been made. Measurements at the site of the Canadian Coast Guard Ship Amundsen <span class="hlt">ice</span> breaker in the Amundsen Gulf showed events of increased bromine monoxide (BrO), coupled with decreases of ozone (O3) and gaseous elemental mercury (GEM), during cold periods in March 2008. The timing of the main event of BrO, O3, and GEM changes was found to be consistent with BrO observed by satellites over an extensive area around the site. Furthermore, satellite sensors detected a doubling of atmospheric BrO in a vortex associated with a spiral rising air pattern. In spring 2009, excessive and widespread bromine explosions occurred in the same region while the regional air temperature was low and the extent of perennial <span class="hlt">ice</span> was significantly reduced compared to the case in 2008. Using satellite observations together with a Rising-Air-Parcel model, we discover a topographic control on BrO distribution such that the Alaskan North Slope and the Canadian Shield region were exposed to elevated BrO, whereas the surrounding mountains isolated the Alaskan interior from bromine intrusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CliPa...8.2079V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CliPa...8.2079V"><span>Sea-<span class="hlt">ice</span> dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-<span class="hlt">ice</span> margins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Voigt, A.; Abbot, D. S.</p> <p>2012-12-01</p> <p>The Snowball Earth bifurcation, or runaway <span class="hlt">ice</span>-albedo feedback, is defined for particular boundary conditions by a critical CO2 and a critical sea-<span class="hlt">ice</span> <span class="hlt">cover</span> (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO2, SI)*, differs greatly among climate models. Here, we study the effect of bare sea-<span class="hlt">ice</span> albedo, sea-<span class="hlt">ice</span> dynamics and ocean heat transport on (CO2, SI)* in the atmosphere-ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma) continents and solar insolation (94% of modern). In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO2, SI)* ≈ (500 ppm, 55%). Replacing the model's standard bare sea-<span class="hlt">ice</span> albedo of 0.75 by a much lower value of 0.45, we find (CO2, SI)* ≈ (204 ppm, 70%). This is consistent with previous work and results from net evaporation and local melting near the sea-<span class="hlt">ice</span> margin. When we additionally disable sea-<span class="hlt">ice</span> dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO2: (CO2, SI)* ≈ (2 ppm, 85%). Therefore, the simulation of sea-<span class="hlt">ice</span> dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO2 for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and only slightly decreases the critical CO2. For disabled sea-<span class="hlt">ice</span> dynamics, the state with 85% sea-<span class="hlt">ice</span> <span class="hlt">cover</span> is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-<span class="hlt">ice</span> <span class="hlt">cover</span> therefore is a soft Snowball state rather than a true Jormungand state. Overall, our results demonstrate that differences in sea-<span class="hlt">ice</span> dynamics schemes can be at least as important as differences in sea-<span class="hlt">ice</span> albedo for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/990526-global-simulations-ice-nucleation-ice-supersaturation-improved-cloud-scheme-community-atmosphere-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/990526-global-simulations-ice-nucleation-ice-supersaturation-improved-cloud-scheme-community-atmosphere-model"><span>Global Simulations of <span class="hlt">Ice</span> nucleation and <span class="hlt">Ice</span> Supersaturation with an Improved Cloud Scheme in the Community Atmosphere Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Gettelman, A.; Liu, Xiaohong; Ghan, Steven J.</p> <p>2010-09-28</p> <p>A process-<span class="hlt">based</span> treatment of <span class="hlt">ice</span> supersaturation and <span class="hlt">ice</span>-nucleation is implemented in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to <span class="hlt">ice</span>, (2) <span class="hlt">ice</span> nucleation by aerosol particles and (3) <span class="hlt">ice</span> cloud <span class="hlt">cover</span> consistent with <span class="hlt">ice</span> microphysics. The scheme is implemented with a 4-class 2 moment microphysics code and is used to evaluate <span class="hlt">ice</span> cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of <span class="hlt">ice</span> mass and mixed phase cloud occurrence better than previous versions of the model. Simulations indicatemore » heterogeneous freezing and contact nucleation on dust are both potentially important over remote areas of the Arctic. Cloud forcing and hence climate is sensitive to different formulations of the <span class="hlt">ice</span> microphysics. Arctic radiative fluxes are sensitive to the parameterization of <span class="hlt">ice</span> clouds. These results indicate that <span class="hlt">ice</span> clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8348W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8348W"><span>Reduced melt on debris-<span class="hlt">covered</span> glaciers: investigations from Changri Nup Glacier, Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wagnon, Patrick; Vincent, Christian; Shea, Joseph M.; Immerzeel, Walter W.; Kraaijenbrink, Philip; Shrestha, Dibas; Soruco, Alvaro; Arnaud, Yves; Brun, Fanny; Berthier, Etienne; Futi Sherpa, Sonam</p> <p>2017-04-01</p> <p>Approximately 25% of the glacierized area in the Everest region is <span class="hlt">covered</span> by debris, yet the surface mass balance of debris-<span class="hlt">covered</span> portions of these glaciers has not been measured directly. In this study, ground-<span class="hlt">based</span> measurements of surface elevation and <span class="hlt">ice</span> depth are combined with terrestrial photogrammetry, unmanned aerial vehicle (UAV) and satellite elevation models to derive the surface mass balance of the debris-<span class="hlt">covered</span> tongue of Changri Nup Glacier, located in the Everest region. Over the debris-<span class="hlt">covered</span> tongue, the mean elevation change between 2011 and 2015 is -0.93 m year-1 or -0.84 m water equivalent per year (w.e. a-1). The mean emergence velocity over this region, estimated from the total <span class="hlt">ice</span> flux through a cross section immediately above the debris-<span class="hlt">covered</span> zone, is +0.37mw.e. a-1. The debris-<span class="hlt">covered</span> portion of the glacier thus has an area averaged mass balance of -1.21+/-0.2mw.e. a-1 between 5240 and 5525 m above sea level (m a.s.l.). Surface mass balances observed on nearby debris-free glaciers suggest that the ablation is strongly reduced (by ca. 1.8mw.e. a-1) by the debris <span class="hlt">cover</span>. The insulating effect of the debris <span class="hlt">cover</span> has a larger effect on total mass loss than the enhanced <span class="hlt">ice</span> ablation due to supraglacial ponds and exposed <span class="hlt">ice</span> cliffs. This finding contradicts earlier geodetic studies and should be considered for modelling the future evolution of debris-<span class="hlt">covered</span> glaciers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930010628','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930010628"><span>Antarctic lakes (above and beneath the <span class="hlt">ice</span> sheet): Analogues for Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rice, J. W., Jr.</p> <p>1992-01-01</p> <p>The perennial <span class="hlt">ice</span> <span class="hlt">covered</span> lakes of the Antarctic are considered to be excellent analogues to lakes that once existed on Mars. Field studies of <span class="hlt">ice</span> <span class="hlt">covered</span> lakes, paleolakes, and polar beaches were conducted in the Bunger Hills Oasis, Eastern Antarctica. These studies are extended to the Dry Valleys, Western Antarctica, and the Arctic. Important distinctions were made between <span class="hlt">ice</span> <span class="hlt">covered</span> and non-<span class="hlt">ice</span> <span class="hlt">covered</span> bodies of water in terms of the geomorphic signatures produced. The most notable landforms produced by <span class="hlt">ice</span> <span class="hlt">covered</span> lakes are <span class="hlt">ice</span> shoved ridges. These features form discrete segmented ramparts of boulders and sediments pushed up along the shores of lakes and/or seas. Sub-<span class="hlt">ice</span> lakes have been discovered under the Antarctic <span class="hlt">ice</span> sheet using radio echo sounding. These lakes occur in regions of low surface slope, low surface accumulations, and low <span class="hlt">ice</span> velocity, and occupy bedrock hollows. The presence of sub-<span class="hlt">ice</span> lakes below the Martian polar caps is possible. The discovery of the Antarctic sub-<span class="hlt">ice</span> lakes raises possibilities concerning Martian lakes and exobiology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP33C1338B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP33C1338B"><span>Inception of the Laurentide <span class="hlt">Ice</span> Sheet using asynchronous coupling of a regional atmospheric model and an <span class="hlt">ice</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Birch, L.; Cronin, T.; Tziperman, E.</p> <p>2017-12-01</p> <p>The climate over the past 0.8 million years has been dominated by <span class="hlt">ice</span> ages. <span class="hlt">Ice</span> sheets have grown about every 100 kyrs, starting from warm interglacials, until they spanned continents. State-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, or the transition of Earth's climate from an interglacial to a glacial state. It has been suggested that this failure may be related to their poorly resolved local mountain topography, due to their coarse spatial resolution. We examine this idea as well as the possible role of <span class="hlt">ice</span> flow dynamics missing in GCMs. We investigate the growth of the Laurentide <span class="hlt">Ice</span> Sheet at 115 kya by focusing on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred. We use the Weather Research and Forecasting model (WRF) in a regional, cloud-resolving configuration with resolved mountain terrain to explore how quickly Baffin Island could become glaciated with the favorable yet realizable conditions of 115 kya insolation, cool summers, and wet winters. Using the model-derived mountain glacier mass balance, we force an <span class="hlt">ice</span> sheet model <span class="hlt">based</span> on the shallow-<span class="hlt">ice</span> approximation, capturing the <span class="hlt">ice</span> flow that may be critical to the spread of <span class="hlt">ice</span> sheets away from mountain <span class="hlt">ice</span> caps. The <span class="hlt">ice</span> sheet model calculates the surface area newly <span class="hlt">covered</span> by <span class="hlt">ice</span> and the change in the <span class="hlt">ice</span> surface elevation, which we then use to run WRF again. Through this type of iterated asynchronous coupling, we investigate how the regional climate responds to both larger areas of <span class="hlt">ice</span> <span class="hlt">cover</span> and changes in <span class="hlt">ice</span> surface elevation. In addition, we use the NOAH-MP Land model to characterize the importance of land processes, like refreezing. We find that initial <span class="hlt">ice</span> growth on the Penny <span class="hlt">Ice</span> Cap causes regional cooling that increases the accumulation on the Barnes <span class="hlt">Ice</span> Cap. We investigate how <span class="hlt">ice</span> and topography changes on Baffin Island may impact both the regional climate and the large-scale circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IzAOP..53.1050K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IzAOP..53.1050K"><span>The First Results of Monitoring the Formation and Destruction of the <span class="hlt">Ice</span> <span class="hlt">Cover</span> in Winter 2014-2015 on Ilmen Lake according to the Measurements of Dual-Frequency Precipitation Radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karaev, V. Yu.; Panfilova, M. A.; Titchenko, Yu. A.; Meshkov, E. M.; Balandina, G. N.; Andreeva, Z. V.</p> <p>2017-12-01</p> <p>The launch of the Dual-frequency Precipitation Radar (DPR) opens up new opportunities for studying and monitoring the land and inland waters. It is the first time radar with a swath (±65°) <span class="hlt">covering</span> regions with cold climate where waters are <span class="hlt">covered</span> with <span class="hlt">ice</span> and land with snow for prolonged periods of time has been used. It is also the first time that the remote sensing is carried out at small incidence angles (less than 19°) at two frequencies (13.6 and 35.5 GHz). The high spatial resolution (4-5 km) significantly increases the number of objects that can be studied using the new radar. Ilmen Lake is chosen as the first test object for the development of complex programs for processing and analyzing data obtained by the DPR. The problem of diagnostics of <span class="hlt">ice-cover</span> formation and destruction according to DPR data has been considered. It is shown that the dependence of the radar backscatter cross section on the incidence angle for autumn <span class="hlt">ice</span> is different from that of spring <span class="hlt">ice</span>, and can be used for classification. A comparison with scattering on the water surface has shown that, at incidence angles exceeding 10°, it is possible to discern all three types of reflecting surfaces: open water, autumn <span class="hlt">ice</span>, and spring <span class="hlt">ice</span>, under the condition of making repeated measurements to avoid possible ambiguity caused by wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1916449H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1916449H"><span>A globally complete map of supraglacial debris <span class="hlt">cover</span> and a new toolkit for debris <span class="hlt">cover</span> research</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herreid, Sam; Pellicciotti, Francesca</p> <p>2017-04-01</p> <p>A growing canon of literature is focused on resolving the processes and implications of debris <span class="hlt">cover</span> on glaciers. However, this work is often confined to a handful of glaciers that were likely selected <span class="hlt">based</span> on criteria optimizing their suitability to test a specific hypothesis or logistical ease. The role of debris <span class="hlt">cover</span> in a glacier system is likely to not go overlooked in forthcoming research, yet the magnitude of this role at a global scale has not yet been fully described. Here, we present a map of debris <span class="hlt">cover</span> for all glacierized regions on Earth including the Greenland <span class="hlt">Ice</span> Sheet using 30 m Landsat data. This dataset will begin to open a wider context to the high quality, localized findings from the debris-<span class="hlt">covered</span> glacier research community and help inform large-scale modeling efforts. A global map of debris <span class="hlt">cover</span> also facilitates analysis attempting to isolate first order geomorphological and climate controls of supraglacial debris production. Furthering the objective of expanding the inclusion of debris <span class="hlt">cover</span> in forthcoming research, we also present an under development suite of open-source, Python <span class="hlt">based</span> tools. Requiring minimal and often freely available input data, we have automated the mapping of: i) debris <span class="hlt">cover</span>, ii) <span class="hlt">ice</span> cliffs, iii) debris <span class="hlt">cover</span> evolution over the Landsat era and iv) glacier flow instabilities from altered debris structures. At the present time, debris extent is the only globally complete quantity but with the expanding repository of high quality global datasets and further tool development minimizing manual tasks and computational cost, we foresee all of these tools being applied globally in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0821P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0821P"><span>RADARSAT-2 Polarimetric Radar Imaging for Lake <span class="hlt">Ice</span> Mapping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, F.; Kang, K.; Duguay, C. R.</p> <p>2016-12-01</p> <p>Changes in lake <span class="hlt">ice</span> dates and duration are useful indicators for assessing long-term climate trends and variability in northern countries. Lake <span class="hlt">ice</span> <span class="hlt">cover</span> observations are also a valuable data source for predictions with numerical <span class="hlt">ice</span> and weather forecasting models. In recent years, satellite remote sensing has assumed a greater role in providing observations of lake <span class="hlt">ice</span> <span class="hlt">cover</span> extent for both modeling and climate monitoring purposes. Polarimetric radar imaging has become a promising tool for lake <span class="hlt">ice</span> mapping at high latitudes where meteorological conditions and polar darkness severely limit observations from optical sensors. In this study, we assessed and characterized the physical scattering mechanisms of lake <span class="hlt">ice</span> from fully polarimetric RADARSAT-2 datasets obtained over Great Bear Lake, Canada, with the intent of classifying open water and different <span class="hlt">ice</span> types during the freeze-up and break-up periods. Model-<span class="hlt">based</span> and eigen-<span class="hlt">based</span> decompositions were employed to construct the coherency matrix into deterministic scattering mechanisms. These procedures as well as basic polarimetric parameters were integrated into modified convolutional neural networks (CNN). The CNN were modified via introduction of a Markov random field into the higher iterative layers of networks for acquiring updated priors and classifying <span class="hlt">ice</span> and open water areas over the lake. We show that the selected polarimetric parameters can help with interpretation of radar-<span class="hlt">ice</span>/water interactions and can be used successfully for water-<span class="hlt">ice</span> segmentation, including different <span class="hlt">ice</span> types. As more satellite SAR sensors are being launched or planned, such as the Sentinel-1a/b series and the upcoming RADARSAT Constellation Mission, the rapid volume growth of data and their analysis require the development of robust automated algorithms. The approach developed in this study was therefore designed with the intent of moving towards fully automated mapping of lake <span class="hlt">ice</span> for consideration by <span class="hlt">ice</span> services.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V31F..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V31F..04D"><span>Pyroclastic density current dynamics and associated hazards at <span class="hlt">ice-covered</span> volcanoes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dufek, J.; Cowlyn, J.; Kennedy, B.; McAdams, J.</p> <p>2015-12-01</p> <p>Understanding the processes by which pyroclastic density currents (PDCs) are emplaced is crucial for volcanic hazard prediction and assessment. Snow and <span class="hlt">ice</span> can facilitate PDC generation by lowering the coefficient of friction and by causing secondary hydrovolcanic explosions, promoting remobilisation of proximally deposited material. Where PDCs travel over snow or <span class="hlt">ice</span>, the reduction in surface roughness and addition of steam and meltwater signficantly changes the flow dynamics, affecting PDC velocities and runout distances. Additionally, meltwater generated during transit and after the flow has come to rest presents an immediate secondary lahar hazard that can impact areas many tens of kilometers beyond the intial PDC. This, together with the fact that deposits emplaced on <span class="hlt">ice</span> are rarely preserved means that PDCs over <span class="hlt">ice</span> have been little studied despite the prevalence of summit <span class="hlt">ice</span> at many tall stratovolcanoes. At Ruapehu volcano in the North Island of New Zealand, a monolithologic welded PDC deposit with unusually rounded clasts provides textural evidence for having been transported over glacial <span class="hlt">ice</span>. Here, we present the results of high-resolution multiphase numerical PDC modeling coupled with experimentaly determined rates of water and steam production for the Ruapehu deposits in order to assess the effect of <span class="hlt">ice</span> on the Ruapehu PDC. The results suggest that the presence of <span class="hlt">ice</span> significantly modified the PDC dynamics, with implications for assessing the PDC and associated lahar hazards at Ruapehu and other glaciated volcanoes worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003146','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003146"><span>Characterizing Arctic Sea <span class="hlt">Ice</span> Topography Using High-Resolution <span class="hlt">Ice</span>Bridge Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Petty, Alek; Tsamados, Michel; Kurtz, Nathan; Farrell, Sinead; Newman, Thomas; Harbeck, Jeremy; Feltham, Daniel; Richter-Menge, Jackie</p> <p>2016-01-01</p> <p>We present an analysis of Arctic sea <span class="hlt">ice</span> topography using high resolution, three-dimensional, surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation <span class="hlt">Ice</span>Bridge mission. Surface features in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009-2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by <span class="hlt">ice</span> type to estimate the topographic variability across first-year and multi-year <span class="hlt">ice</span> regimes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010037604','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010037604"><span>Satellite Remote Sensing: Passive-Microwave Measurements of Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Satellite passive-microwave measurements of sea <span class="hlt">ice</span> have provided global or near-global sea <span class="hlt">ice</span> data for most of the period since the launch of the Nimbus 5 satellite in December 1972, and have done so with horizontal resolutions on the order of 25-50 km and a frequency of every few days. These data have been used to calculate sea <span class="hlt">ice</span> concentrations (percent areal coverages), sea <span class="hlt">ice</span> extents, the length of the sea <span class="hlt">ice</span> season, sea <span class="hlt">ice</span> temperatures, and sea <span class="hlt">ice</span> velocities, and to determine the timing of the seasonal onset of melt as well as aspects of the <span class="hlt">ice</span>-type composition of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. In each case, the calculations are <span class="hlt">based</span> on the microwave emission characteristics of sea <span class="hlt">ice</span> and the important contrasts between the microwave emissions of sea <span class="hlt">ice</span> and those of the surrounding liquid-water medium.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840008344&hterms=sea+world&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsea%2Bworld','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840008344&hterms=sea+world&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsea%2Bworld"><span>Spaceborne SAR and sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weeks, W. F.</p> <p>1983-01-01</p> <p>A number of remote sensing systems deployed in satellites to view the Earth which are successful in gathering data on the behavior of the world's snow and <span class="hlt">ice</span> <span class="hlt">covers</span> are described. Considering sea <span class="hlt">ice</span> which <span class="hlt">covers</span> over 10% of the world ocean, systems that have proven capable to collect useful data include those operating in the visible, near-infrared, infrared, and microwave frequency ranges. The microwave systems have the essential advantage in observing the <span class="hlt">ice</span> under all weather and lighting conditions. Without this capability data are lost during the long polar night and during times of storm passage, periods when <span class="hlt">ice</span> activity can be intense. The margins of the <span class="hlt">ice</span> pack, a region of particular interest, is shrouded in cloud between 80 and 90% of the time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29080011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29080011"><span>Oil spill response capabilities and technologies for <span class="hlt">ice-covered</span> Arctic marine waters: A review of recent developments and established practices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wilkinson, Jeremy; Beegle-Krause, C J; Evers, Karl-Ulrich; Hughes, Nick; Lewis, Alun; Reed, Mark; Wadhams, Peter</p> <p>2017-12-01</p> <p>Renewed political and commercial interest in the resources of the Arctic, the reduction in the extent and thickness of sea <span class="hlt">ice</span>, and the recent failings that led to the Deepwater Horizon oil spill, have prompted industry and its regulatory agencies, governments, local communities and NGOs to look at all aspects of Arctic oil spill countermeasures with fresh eyes. This paper provides an overview of present oil spill response capabilities and technologies for <span class="hlt">ice-covered</span> waters, as well as under potential future conditions driven by a changing climate. Though not an exhaustive review, we provide the key research results for oil spill response from knowledge accumulated over many decades, including significant review papers that have been prepared as well as results from recent laboratory tests, field programmes and modelling work. The three main areas <span class="hlt">covered</span> by the review are as follows: oil weathering and modelling; oil detection and monitoring; and oil spill response techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSHE14B1411P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSHE14B1411P"><span>Atmospheric form drag over Arctic sea <span class="hlt">ice</span> derived from high-resolution <span class="hlt">Ice</span>Bridge elevation data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petty, A.; Tsamados, M.; Kurtz, N. T.</p> <p>2016-02-01</p> <p>Here we present a detailed analysis of atmospheric form drag over Arctic sea <span class="hlt">ice</span>, using high resolution, three-dimensional surface elevation data from the NASA Operation <span class="hlt">Ice</span>Bridge Airborne Topographic Mapper (ATM) laser altimeter. Surface features in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> are detected using a novel feature-picking algorithm. We derive information regarding the height, spacing and orientation of unique surface features from 2009-2014 across both first-year and multiyear <span class="hlt">ice</span> regimes. The topography results are used to explicitly calculate atmospheric form drag coefficients; utilizing existing form drag parameterizations. The atmospheric form drag coefficients show strong regional variability, mainly due to variability in <span class="hlt">ice</span> type/age. The transition from a perennial to a seasonal <span class="hlt">ice</span> <span class="hlt">cover</span> therefore suggest a decrease in the atmospheric form drag coefficients over Arctic sea <span class="hlt">ice</span> in recent decades. These results are also being used to calibrate a recent form drag parameterization scheme included in the sea <span class="hlt">ice</span> model CICE, to improve the representation of form drag over Arctic sea <span class="hlt">ice</span> in global climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMIN11C1538S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMIN11C1538S"><span>The Timing of Arctic Sea <span class="hlt">Ice</span> Advance and Retreat as an Indicator of <span class="hlt">Ice</span>-Dependent Marine Mammal Habitat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stern, H. L.; Laidre, K. L.</p> <p>2013-12-01</p> <p>The Arctic is widely recognized as the front line of climate change. Arctic air temperature is rising at twice the global average rate, and the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> is shrinking and thinning, with total disappearance of summer sea <span class="hlt">ice</span> projected to occur in a matter of decades. Arctic marine mammals such as polar bears, seals, walruses, belugas, narwhals, and bowhead whales depend on the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> as an integral part of their existence. While the downward trend in sea-<span class="hlt">ice</span> extent in a given month is an often-used metric for quantifying physical changes in the <span class="hlt">ice</span> <span class="hlt">cover</span>, it is not the most relevant measure for characterizing changes in the sea-<span class="hlt">ice</span> habitat of marine mammals. Species that depend on sea <span class="hlt">ice</span> are behaviorally tied to the annual retreat of sea <span class="hlt">ice</span> in the spring and advance in the fall. Changes in the timing of the spring retreat and the fall advance are more relevant to Arctic marine species than changes in the areal sea-<span class="hlt">ice</span> coverage in a particular month of the year. Many ecologically important regions of the Arctic are essentially <span class="hlt">ice-covered</span> in winter and <span class="hlt">ice</span>-free in summer, and will probably remain so for a long time into the future. But the dates of sea-<span class="hlt">ice</span> retreat in spring and advance in fall are key indicators of climate change for <span class="hlt">ice</span>-dependent marine mammals. We use daily sea-<span class="hlt">ice</span> concentration data derived from satellite passive microwave sensors to calculate the dates of sea-<span class="hlt">ice</span> retreat in spring and advance in fall in 12 regions of the Arctic for each year from 1979 through 2013. The regions include the peripheral seas around the Arctic Ocean (Beaufort, Chukchi, East Siberian, Laptev, Kara, Barents), the Canadian Arctic Archipelago, and the marginal seas (Okhotsk, Bering, East Greenland, Baffin Bay, Hudson Bay). We find that in 11 of the 12 regions (all except the Bering Sea), sea <span class="hlt">ice</span> is retreating earlier in spring and advancing later in fall. Rates of spring retreat range from -5 to -8 days/decade, and rates of fall advance range from +5 to +9</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030062802','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030062802"><span>Satellite Snow-<span class="hlt">Cover</span> Mapping: A Brief Review</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, Dorothy K.</p> <p>1995-01-01</p> <p>Satellite snow mapping has been accomplished since 1966, initially using data from the reflective part of the electromagnetic spectrum, and now also employing data from the microwave part of the spectrum. Visible and near-infrared sensors can provide excellent spatial resolution from space enabling detailed snow mapping. When digital elevation models are also used, snow mapping can provide realistic measurements of snow extent even in mountainous areas. Passive-microwave satellite data permit global snow <span class="hlt">cover</span> to be mapped on a near-daily basis and estimates of snow depth to be made, but with relatively poor spatial resolution (approximately 25 km). Dense forest <span class="hlt">cover</span> limits both techniques and optical remote sensing is limited further by cloudcover conditions. Satellite remote sensing of snow <span class="hlt">cover</span> with imaging radars is still in the early stages of research, but shows promise at least for mapping wet or melting snow using C-band (5.3 GHz) synthetic aperture radar (SAR) data. Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) data beginning with the launch of the first EOS platform in 1998. Digital maps will be produced that will provide daily, and maximum weekly global snow, sea <span class="hlt">ice</span> and lake <span class="hlt">ice</span> <span class="hlt">cover</span> at 1-km spatial resolution. Statistics will be generated on the extent and persistence of snow or <span class="hlt">ice</span> <span class="hlt">cover</span> in each pixel for each weekly map, cloudcover permitting. It will also be possible to generate snow- and <span class="hlt">ice-cover</span> maps using MODIS data at 250- and 500-m resolution, and to study and map snow and <span class="hlt">ice</span> characteristics such as albedo. been under development. Passive-microwave data offer the potential for determining not only snow <span class="hlt">cover</span>, but snow water equivalent, depth and wetness under all sky conditions. A number of algorithms have been developed to utilize passive-microwave brightness temperatures to provide information on snow <span class="hlt">cover</span> and water equivalent. The variability of vegetative Algorithms are being developed to map global snow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCry....8.2409L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCry....8.2409L"><span><span class="hlt">Ice</span> and AIS: ship speed data and sea <span class="hlt">ice</span> forecasts in the Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Löptien, U.; Axell, L.</p> <p>2014-12-01</p> <p>The Baltic Sea is a seasonally <span class="hlt">ice-covered</span> marginal sea located in a densely populated area in northern Europe. Severe sea <span class="hlt">ice</span> conditions have the potential to hinder the intense ship traffic considerably. Thus, sea <span class="hlt">ice</span> fore- and nowcasts are regularly provided by the national weather services. Typically, the forecast comprises several <span class="hlt">ice</span> properties that are distributed as prognostic variables, but their actual usefulness is difficult to measure, and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the automatic identification system (AIS), with the respective forecasted <span class="hlt">ice</span> conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore- and nowcasts. More precisely, 62-67% of ship speed variations can be explained by the forecasted <span class="hlt">ice</span> properties when fitting a mixed-effect model. This statistical fit is <span class="hlt">based</span> on a test region in the Bothnian Sea during the severe winter 2011 and employs 15 to 25 min averages of ship speed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCD.....8.3811L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCD.....8.3811L"><span><span class="hlt">Ice</span> and AIS: ship speed data and sea <span class="hlt">ice</span> forecasts in the Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Löptien, U.; Axell, L.</p> <p>2014-07-01</p> <p>The Baltic Sea is a seasonally <span class="hlt">ice</span> <span class="hlt">covered</span> marginal sea located in a densely populated area in northern Europe. Severe sea <span class="hlt">ice</span> conditions have the potential to hinder the intense ship traffic considerably. Thus, sea <span class="hlt">ice</span> fore- and nowcasts are regularly provided by the national weather services. Typically, several <span class="hlt">ice</span> properties are allocated, but their actual usefulness is difficult to measure and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the Automatic Identification System (AIS), with the respective forecasted <span class="hlt">ice</span> conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore- and nowcasts. More precisely, 62-67% of ship speed variations can be explained by the forecasted <span class="hlt">ice</span> properties when fitting a mixed effect model. This statistical fit is <span class="hlt">based</span> on a test region in the Bothnian Bay during the severe winter 2011 and employes 15 to 25 min averages of ship speed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920040056&hterms=data+types&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddata%2Btypes','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920040056&hterms=data+types&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddata%2Btypes"><span>Effects of weather on the retrieval of sea <span class="hlt">ice</span> concentration and <span class="hlt">ice</span> type from passive microwave data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maslanik, J. A.</p> <p>1992-01-01</p> <p>Effects of wind, water vapor, and cloud liquid water on <span class="hlt">ice</span> concentration and <span class="hlt">ice</span> type calculated from passive microwave data are assessed through radiative transfer calculations and observations. These weather effects can cause overestimates in <span class="hlt">ice</span> concentration and more substantial underestimates in multi-year <span class="hlt">ice</span> percentage by decreasing polarization and by decreasing the gradient between frequencies. The effect of surface temperature and air temperature on the magnitudes of weather-related errors is small for <span class="hlt">ice</span> concentration and substantial for multiyear <span class="hlt">ice</span> percentage. The existing weather filter in the NASA Team Algorithm addresses only weather effects over open ocean; the additional use of local open-ocean tie points and an alternative weather correction for the marginal <span class="hlt">ice</span> zone can further reduce errors due to weather. <span class="hlt">Ice</span> concentrations calculated using 37 versus 18 GHz data show little difference in total <span class="hlt">ice</span> <span class="hlt">covered</span> area, but greater differences in intermediate concentration classes. Given the magnitude of weather-related errors in <span class="hlt">ice</span> classification from passive microwave data, corrections for weather effects may be necessary to detect small trends in <span class="hlt">ice</span> <span class="hlt">covered</span> area and <span class="hlt">ice</span> type for climate studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970015273','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970015273"><span>Estimating the Thickness of Sea <span class="hlt">Ice</span> Snow <span class="hlt">Cover</span> in the Weddell Sea from Passive Microwave Brightness Temperatures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arrigo, K. R.; vanDijken, G. L.; Comiso, J. C.</p> <p>1996-01-01</p> <p>Passive microwave satellite observations have frequently been used to observe changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span> and concentration. Comiso et al. showed that there may also be a direct relationship between the thickness of snow <span class="hlt">cover</span> (h(sub s)) on <span class="hlt">ice</span> and microwave emissivity at 90 GHz. Because the in situ experiment of experiment of Comiso et al. was limited to a single station, the relationship is re-examined in this paper in a more general context and using more extensive in situ microwave observations and measurements of h from the Weddell Sea 1986 and 1989 winter cruises. Good relationships were found to exist between h(sub s) sand the emissivity at 90 GHz - 10 GHz and the emissivity at 90 GHz - 18.7 GHz when the standard deviation of h(sub s) was less than 50% of the mean and when h(sub s) was less than 0.25 m. The reliance of these relationships on h(sub s) is most likely caused by the limited penetration through the snow of radiation at 90 GHz. When the algorithm was applied to the Special Sensor Microwave/Imager (SSM/I) satellite data from the Weddell Sea, the resulting mean h(sub s) agreed within 5% of the mean calculated from greater than 1400 in situ observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C51F..06G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C51F..06G"><span>Atmospherically-driven collapse of a marine-<span class="hlt">based</span> <span class="hlt">ice</span> stream</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greenwood, S. L.; Clason, C. C.</p> <p>2016-12-01</p> <p>Marine-terminating glaciers and the sectors of <span class="hlt">ice</span> sheets that are grounded below sea level are widely considered to be vulnerable to unstable retreat. The southern sector of the retreating Fennoscandian <span class="hlt">Ice</span> Sheet comprised a large, aqueous-terminating <span class="hlt">ice</span> sheet catchment grounded well below sea level throughout its deglaciation. However, the behaviour, timing of and controls upon <span class="hlt">ice</span> sheet retreat through the Baltic and Bothnian basins have thus far been inferred only indirectly from peripheral, terrestrial-<span class="hlt">based</span> geological archives. Recent acquisition of high-resolution multibeam bathymetry opens these basins up, for the first time, to direct investigation of their glacial footprint and palaeo-<span class="hlt">ice</span> sheet behaviour. Multibeam data reveal a rich glacial landform legacy of the Bothnian Sea deglaciation. A late-stage palaeo-<span class="hlt">ice</span> stream formed a narrow corridor of fast flow. Its pathway is overprinted by a vast field of basal crevasse squeeze ridges, while abundant traces of high subglacial meltwater volumes call for considerable input of surface meltwater to the subglacial system. We interpret a short-lived <span class="hlt">ice</span> stream event under high extension, precipitating large-scale hydrofracture-driven collapse of the <span class="hlt">ice</span> sheet sector under conditions of high surface melting. Experiments with a physically-<span class="hlt">based</span> numerical flowline model indicate that the rate and pattern of Bothnian Sea <span class="hlt">ice</span> stream retreat are most sensitive to surface mass balance change and crevasse propagation, while remarkably insensitive to submarine melting and sea level change. We interpret strongly atmospherically-driven retreat of this marine-<span class="hlt">based</span> <span class="hlt">ice</span> sheet sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070016598&hterms=sea+ice+albedo&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsea%2Bice%2Balbedo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070016598&hterms=sea+ice+albedo&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsea%2Bice%2Balbedo"><span>Observational Evidence of a Hemispheric-wide <span class="hlt">Ice</span>-ocean Albedo Feedback Effect on Antarctic Sea-<span class="hlt">ice</span> Decay</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nihashi, Sohey; Cavalieri, Donald J.</p> <p>2007-01-01</p> <p>The effect of <span class="hlt">ice</span>-ocean albedo feedback (a kind of <span class="hlt">ice</span>-albedo feedback) on sea-<span class="hlt">ice</span> decay is demonstrated over the Antarctic sea-<span class="hlt">ice</span> zone from an analysis of satellite-derived hemispheric sea <span class="hlt">ice</span> concentration and European Centre for Medium-Range Weather Forecasts (ERA-40) atmospheric data for the period 1979-2001. Sea <span class="hlt">ice</span> concentration in December (time of most active melt) correlates better with the meridional component of the wind-forced <span class="hlt">ice</span> drift (MID) in November (beginning of the melt season) than the MID in December. This 1 month lagged correlation is observed in most of the Antarctic sea-<span class="hlt">ice</span> <span class="hlt">covered</span> ocean. Daily time series of <span class="hlt">ice</span> , concentration show that the <span class="hlt">ice</span> concentration anomaly increases toward the time of maximum sea-<span class="hlt">ice</span> melt. These findings can be explained by the following positive feedback effect: once <span class="hlt">ice</span> concentration decreases (increases) at the beginning of the melt season, solar heating of the upper ocean through the increased (decreased) open water fraction is enhanced (reduced), leading to (suppressing) a further decrease in <span class="hlt">ice</span> concentration by the oceanic heat. Results obtained fi-om a simple <span class="hlt">ice</span>-ocean coupled model also support our interpretation of the observational results. This positive feedback mechanism explains in part the large interannual variability of the sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1615919R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1615919R"><span>Airborne and ground <span class="hlt">based</span> measurements in McMurdo Sound, Antarctica, for the validation of satellite derived <span class="hlt">ice</span> thickness</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rack, Wolfgang; Haas, Christian; Langhorne, Pat; Leonard, Greg; Price, Dan; Barnsdale, Kelvin; Soltanzadeh, Iman</p> <p>2014-05-01</p> <p>Melting and freezing processes in the <span class="hlt">ice</span> shelf cavities of the Ross and McMurdo <span class="hlt">Ice</span> Shelves significantly influence the sea <span class="hlt">ice</span> formation in McMurdo Sound. Between 2009 and 2013 we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure thickness and freeboard profiles across the <span class="hlt">ice</span> shelf and the landfast sea <span class="hlt">ice</span>, which was accompanied by extensive field validation, and coordinated with satellite altimeter overpasses. Using freeboard and thickness, the bulk density of all <span class="hlt">ice</span> types was calculated assuming hydrostatic equilibrium. Significant density steps were detected between first-year and multi-year sea <span class="hlt">ice</span>, with higher values for the younger sea <span class="hlt">ice</span>. Values are overestimated in areas with abundance of sub-<span class="hlt">ice</span> platelets because of overestimation in both <span class="hlt">ice</span> thickness and freeboard. On the <span class="hlt">ice</span> shelf, bulk <span class="hlt">ice</span> densities were sometimes higher than that of pure <span class="hlt">ice</span>, which can be explained by both the accretion of marine <span class="hlt">ice</span> and glacial sediments. For thin <span class="hlt">ice</span>, the freeboard to thickness conversion critically depends on the knowledge of snow properties. Our measurements allow tuning and validation of snow <span class="hlt">cover</span> simulations using the Weather Research Forecasting (WRF) model. The simulated snowcover is used to calculate <span class="hlt">ice</span> thickness from satellite derived freeboard. The results of our measurements, which are supported by the New Zealand Antarctic programme, draw a picture of how oceanographic processes influence the <span class="hlt">ice</span> shelf morphology and sea <span class="hlt">ice</span> formation in McMurdo Sound, and how satellite derived freeboard of ICESat and CryoSat together with information on snow <span class="hlt">cover</span> can potentially capture the signature of these processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA01786.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA01786.html"><span>Space Radar Image of Weddell Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1999-04-15</p> <p>This is the first calibrated, multi-frequency, multi-polarization spaceborne radar image of the seasonal sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in the Weddell Sea, Antarctica. The multi-channel data provide scientists with details about the <span class="hlt">ice</span> pack they cannot see any other way and indicates that the large expanse of sea-<span class="hlt">ice</span> is, in fact, comprised of many smaller rounded <span class="hlt">ice</span> floes, shown in blue-gray. These data are particularly useful in helping scientists estimate the thickness of the <span class="hlt">ice</span> <span class="hlt">cover</span> which is often extremely difficult to measure with other remote sensing systems. The extent, and especially thickness, of the polar ocean's sea-<span class="hlt">ice</span> <span class="hlt">cover</span> together have important implications for global climate by regulating the loss of heat from the ocean to the cold polar atmosphere. The image was acquired on October 3, 1994, by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour. This image is produced by overlaying three channels of radar data in the following colors: red (C-band, HH-polarization), green (L-band HV-polarization), and blue (L-band, HH-polarization). The image is oriented almost east-west with a center location of 58.2 degrees South and 21.6 degrees East. Image dimensions are 45 kilometers by 18 kilometers (28 miles by 11 miles). Most of the <span class="hlt">ice</span> <span class="hlt">cover</span> is composed of rounded, undeformed blue-gray floes, about 0.7 meters (2 feet) thick, which are surrounded by a jumble of red-tinged deformed <span class="hlt">ice</span> pieces which are up to 2 meters (7 feet) thick. The winter cycle of <span class="hlt">ice</span> growth and deformation often causes this <span class="hlt">ice</span> <span class="hlt">cover</span> to split apart, exposing open water or "leads." <span class="hlt">Ice</span> growth within these openings is rapid due to the cold, brisk Antarctic atmosphere. Different stages of new-<span class="hlt">ice</span> growth can be seen within the linear leads, resulting from continuous opening and closing. The blue lines within the leads are open water areas in new fractures which are roughened by wind. The bright red lines are an intermediate stage of new-<span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21G1186T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21G1186T"><span>There goes the sea <span class="hlt">ice</span>: following Arctic sea <span class="hlt">ice</span> parcels and their properties.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tschudi, M. A.; Tooth, M.; Meier, W.; Stewart, S.</p> <p>2017-12-01</p> <p>Arctic sea <span class="hlt">ice</span> distribution has changed considerably over the last couple of decades. Sea <span class="hlt">ice</span> extent record minimums have been observed in recent years, the distribution of <span class="hlt">ice</span> age now heavily favors younger <span class="hlt">ice</span>, and sea <span class="hlt">ice</span> is likely thinning. This new state of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has several impacts, including effects on marine life, feedback on the warming of the ocean and atmosphere, and on the future evolution of the <span class="hlt">ice</span> pack. The shift in the state of the <span class="hlt">ice</span> <span class="hlt">cover</span>, from a pack dominated by older <span class="hlt">ice</span>, to the current state of a pack with mostly young <span class="hlt">ice</span>, impacts specific properties of the <span class="hlt">ice</span> pack, and consequently the pack's response to the changing Arctic climate. For example, younger <span class="hlt">ice</span> typically contains more numerous melt ponds during the melt season, resulting in a lower albedo. First-year <span class="hlt">ice</span> is typically thinner and more fragile than multi-year <span class="hlt">ice</span>, making it more susceptible to dynamic and thermodynamic forcing. To investigate the response of the <span class="hlt">ice</span> pack to climate forcing during summertime melt, we have developed a database that tracks individual Arctic sea <span class="hlt">ice</span> parcels along with associated properties as these parcels advect during the summer. Our database tracks parcels in the Beaufort Sea, from 1985 - present, along with variables such as <span class="hlt">ice</span> surface temperature, albedo, <span class="hlt">ice</span> concentration, and convergence. We are using this database to deduce how these thousands of tracked parcels fare during summer melt, i.e. what fraction of the parcels advect through the Beaufort, and what fraction melts out? The tracked variables describe the thermodynamic and dynamic forcing on these parcels during their journey. This database will also be made available to all interested investigators, after it is published in the near future. The attached image shows the <span class="hlt">ice</span> surface temperature of all parcels (right) that advected through the Beaufort Sea region (left) in 2014.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950023826','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950023826"><span>Sea <span class="hlt">ice</span> motions in the Central Arctic pack <span class="hlt">ice</span> as inferred from AVHRR imagery</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Emery, William; Maslanik, James; Fowler, Charles</p> <p>1995-01-01</p> <p>Synoptic observations of <span class="hlt">ice</span> motion in the Arctic Basin are currently limited to those acquired by drifting buoys and, more recently, radar data from ERS-1. Buoys are not uniformly distributed throughout the Arctic, and SAR coverage is currently limited regionally and temporally due to the data volume, swath width, processing requirements, and power needs of the SAR. Additional <span class="hlt">ice</span>-motion observations that can map <span class="hlt">ice</span> responses simultaneously over large portions of the Arctic on daily to weekly time intervals are thus needed to augment the SAR and buoys data and to provide an intermediate-scale measure of <span class="hlt">ice</span> drift suitable for climatological analyses and <span class="hlt">ice</span> modeling. Principal objectives of this project were to: (1) demonstrate whether sufficient <span class="hlt">ice</span> features and <span class="hlt">ice</span> motion existed within the consolidated <span class="hlt">ice</span> pack to permit motion tracking using AVHRR imagery; (2) determine the limits imposed on AVHRR mapping by cloud <span class="hlt">cover</span>; and (3) test the applicability of AVHRR-derived motions in studies of <span class="hlt">ice</span>-atmosphere interactions. Each of these main objectives was addressed. We conclude that AVHRR data, particularly when blended with other available observations, provide a valuable data set for studying sea <span class="hlt">ice</span> processes. In a follow-on project, we are now extending this work to <span class="hlt">cover</span> larger areas and to address science questions in more detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000769.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000769.html"><span>Sea <span class="hlt">ice</span> off western Alaska</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-02-20</p> <p>On February 4, 2014 the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA’s Aqua satellite captured a true-color image of sea <span class="hlt">ice</span> off of western Alaska. In this true-color image, the snow and <span class="hlt">ice</span> <span class="hlt">covered</span> land appears bright white while the floating sea <span class="hlt">ice</span> appears a duller grayish-white. Snow over the land is drier, and reflects more light back to the instrument, accounting for the very bright color. <span class="hlt">Ice</span> overlying oceans contains more water, and increasing water decreases reflectivity of <span class="hlt">ice</span>, resulting in duller colors. Thinner <span class="hlt">ice</span> is also duller. The ocean waters are tinted with green, likely due to a combination of sediment and phytoplankton. Alaska lies to the east in this image, and Russia to the west. The Bering Strait, <span class="hlt">covered</span> with <span class="hlt">ice</span>, lies between to two. South of the Bering Strait, the waters are known as the Bering Sea. To the north lies the Chukchi Sea. The bright white island south of the Bering Strait is St. Lawrence Island. Home to just over 1200 people, the windswept island belongs to the United States, but sits closer to Russia than to Alaska. To the southeast of the island a dark area, loosely <span class="hlt">covered</span> with floating sea <span class="hlt">ice</span>, marks a persistent polynya – an area of open water surrounded by more frozen sea <span class="hlt">ice</span>. Due to the prevailing winds, which blow the sea <span class="hlt">ice</span> away from the coast in this location, the area rarely completely freezes. The <span class="hlt">ice-covered</span> areas in this image, as well as the Beaufort Sea, to the north, are critical areas for the survival of the ringed seal, a threatened species. The seals use the sea <span class="hlt">ice</span>, including <span class="hlt">ice</span> caves, to rear their young, and use the free-floating sea <span class="hlt">ice</span> for molting, raising the young and breeding. In December 2014, the National Oceanic and Atmospheric Administration (NOAA) proposed that much of this region be set aside as critical, protected habitat for the ringed seal. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760055139&hterms=sensing+drainage&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsensing%2Bdrainage','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760055139&hterms=sensing+drainage&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsensing%2Bdrainage"><span>An integrated approach to the remote sensing of floating <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Campbell, W. J.; Ramseier, R. O.; Weeks, W. F.; Gloersen, P.</p> <p>1976-01-01</p> <p>Review article on remote sensing applications to glaciology. <span class="hlt">Ice</span> parameters sensed include: <span class="hlt">ice</span> <span class="hlt">cover</span> vs open water, <span class="hlt">ice</span> thickness, distribution and morphology of <span class="hlt">ice</span> formations, vertical resolution of <span class="hlt">ice</span> thickness, <span class="hlt">ice</span> salinity (percolation and drainage of brine; flushing of <span class="hlt">ice</span> body with fresh water), first-year <span class="hlt">ice</span> and multiyear <span class="hlt">ice</span>, <span class="hlt">ice</span> growth rate and surface heat flux, divergence of <span class="hlt">ice</span> packs, snow <span class="hlt">cover</span> masking <span class="hlt">ice</span>, behavior of <span class="hlt">ice</span> shelves, icebergs, lake <span class="hlt">ice</span> and river <span class="hlt">ice</span>; time changes. Sensing techniques discussed include: satellite photographic surveys, thermal IR, passive and active microwave studies, microwave radiometry, microwave scatterometry, side-looking radar, and synthetic aperture radar. Remote sensing of large aquatic mammals and operational <span class="hlt">ice</span> forecasting are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PEPS....2....8T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PEPS....2....8T"><span>Biogeochemistry and limnology in Antarctic subglacial weathering: molecular evidence of the linkage between subglacial silica input and primary producers in a perennially <span class="hlt">ice-covered</span> lake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takano, Yoshinori; Kojima, Hisaya; Takeda, Eriko; Yokoyama, Yusuke; Fukui, Manabu</p> <p>2015-12-01</p> <p>We report a 6,000 years record of subglacial weathering and biogeochemical processes in two perennially <span class="hlt">ice-covered</span> glacial lakes at Rundvågshetta, on the Soya Coast of Lützow-Holm Bay, East Antarctica. The two lakes, Lake Maruwan Oike and Lake Maruwan-minami, are located in a channel that drains subglacial water from the <span class="hlt">base</span> of the East Antarctic <span class="hlt">ice</span> sheet. Greenish-grayish organic-rich laminations in sediment cores from the lakes indicate continuous primary production affected by the inflow of subglacial meltwater containing relict carbon, nitrogen, sulfur, and other essential nutrients. Biogenic silica, amorphous hydrated silica, and DNA-<span class="hlt">based</span> molecular signatures of sedimentary facies indicate that diatom assemblages are the dominant primary producers, supported by the input of inorganic silicon (Si) from the subglacial inflow. This study highlights the significance of subglacial water-rock interactions during physical and chemical weathering processes and the importance of such interactions for the supply of bioavailable nutrients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810011207','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810011207"><span>Oceanographic influences on the sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Sea of Okhotsk</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gratz, A. J.; Parkinson, C. L.</p> <p>1981-01-01</p> <p>Sea <span class="hlt">ice</span> conditions in the Sea of Okhotsk, as determined by satellite images from the electrically scanning microwave radiometer on board Nimbus 5, were analyzed in conjunction with the known oceanography. In particular, the sea <span class="hlt">ice</span> coverage was compared with the bottom bathymetry and the surface currents, water temperatures, and salinity. It is found that <span class="hlt">ice</span> forms first in cold, shallow, low salinity waters. Once formed, the <span class="hlt">ice</span> seems to drift in a direction approximating the Okhotsk-Kuril current system. Two basic patterns of <span class="hlt">ice</span> edge positioning which persist for significant periods were identified as a rectangular structure and a wedge structure. Each of these is strongly correlated with the bathymetry of the region and with the known current system, suggesting that convective depth and ocean currents play an important role in determining <span class="hlt">ice</span> patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.8481G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.8481G"><span>Impact of aerosol emission controls on future Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gagné, M.-Ã..; Gillett, N. P.; Fyfe, J. C.</p> <p>2015-10-01</p> <p>We examine the response of Arctic sea <span class="hlt">ice</span> to projected aerosol and aerosol precursor emission changes under the Representative Concentration Pathway (RCP) scenarios in simulations of the Canadian Earth System Model. The overall decrease in aerosol loading causes a warming, largest over the Arctic, which leads to an annual mean reduction in sea <span class="hlt">ice</span> extent of approximately 1 million km2 over the 21st century in all RCP scenarios. This accounts for approximately 25% of the simulated reduction in sea <span class="hlt">ice</span> extent in RCP 4.5, and 40% of the reduction in RCP 2.5. In RCP 4.5, the Arctic ocean is projected to become <span class="hlt">ice</span>-free during summertime in 2045, but it does not become <span class="hlt">ice</span>-free until 2057 in simulations with aerosol precursor emissions held fixed at 2000 values. Thus, while reductions in aerosol emissions have significant health and environmental benefits, their substantial contribution to projected Arctic climate change should not be overlooked.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1157M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1157M"><span>Canadian snow and sea <span class="hlt">ice</span>: historical trends and projections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mudryk, Lawrence R.; Derksen, Chris; Howell, Stephen; Laliberté, Fred; Thackeray, Chad; Sospedra-Alfonso, Reinel; Vionnet, Vincent; Kushner, Paul J.; Brown, Ross</p> <p>2018-04-01</p> <p>The Canadian Sea <span class="hlt">Ice</span> and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state of the art observational data to advance dynamical prediction, projections, and understanding of seasonal snow <span class="hlt">cover</span> and sea <span class="hlt">ice</span> in Canada and the circumpolar Arctic. Here, we present an assessment from the CanSISE Network on trends in the historical record of snow <span class="hlt">cover</span> (fraction, water equivalent) and sea <span class="hlt">ice</span> (area, concentration, type, and thickness) across Canada. We also assess projected changes in snow <span class="hlt">cover</span> and sea <span class="hlt">ice</span> likely to occur by mid-century, as simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) suite of Earth system models. The historical datasets show that the fraction of Canadian land and marine areas <span class="hlt">covered</span> by snow and <span class="hlt">ice</span> is decreasing over time, with seasonal and regional variability in the trends consistent with regional differences in surface temperature trends. In particular, summer sea <span class="hlt">ice</span> <span class="hlt">cover</span> has decreased significantly across nearly all Canadian marine regions, and the rate of multi-year <span class="hlt">ice</span> loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last 8 years. The multi-model consensus over the 2020-2050 period shows reductions in fall and spring snow <span class="hlt">cover</span> fraction and sea <span class="hlt">ice</span> concentration of 5-10 % per decade (or 15-30 % in total), with similar reductions in winter sea <span class="hlt">ice</span> concentration in both Hudson Bay and eastern Canadian waters. Peak pre-melt terrestrial snow water equivalent reductions of up to 10 % per decade (30 % in total) are projected across southern Canada.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/sciencecinema/biblio/987230','SCIGOVIMAGE-SCICINEMA'); return false;" href="http://www.osti.gov/sciencecinema/biblio/987230"><span>The Role of Snow and <span class="hlt">Ice</span> in the Climate System</span></a></p> <p><a target="_blank" href="http://www.osti.gov/sciencecinema/">ScienceCinema</a></p> <p>Barry, Roger G.</p> <p>2017-12-09</p> <p>Global snow and <span class="hlt">ice</span> <span class="hlt">cover</span> (the 'cryosphere') plays a major role in global climate and hydrology through a range of complex interactions and feedbacks, the best known of which is the <span class="hlt">ice</span> - albedo feedback. Snow and <span class="hlt">ice</span> <span class="hlt">cover</span> undergo marked seasonal and long term changes in extent and thickness. The perennial elements - the major <span class="hlt">ice</span> sheets and permafrost - play a role in present-day regional and local climate and hydrology, but the large seasonal variations in snow <span class="hlt">cover</span> and sea <span class="hlt">ice</span> are of importance on continental to hemispheric scales. The characteristics of these variations, especially in the Northern Hemisphere, and evidence for recent trends in snow and <span class="hlt">ice</span> extent are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1366350','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1366350"><span>West Antarctic <span class="hlt">Ice</span> Sheet cloud <span class="hlt">cover</span> and surface radiation budget from NASA A-Train satellites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Scott, Ryan C.; Lubin, Dan; Vogelmann, Andrew M.</p> <p></p> <p>Clouds are an essential parameter of the surface energy budget influencing the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS) response to atmospheric warming and net contribution to global sea-level rise. A four-year record of NASA A-Train cloud observations is combined with surface radiation measurements to quantify the WAIS radiation budget and constrain the three-dimensional occurrence frequency, thermodynamic phase partitioning, and surface radiative effect of clouds over West Antarctica (WA). The skill of satellite-modeled radiative fluxes is confirmed through evaluation against measurements at four Antarctic sites (WAIS Divide <span class="hlt">Ice</span> Camp, Neumayer, Syowa, and Concordia Stations). And due to perennial high-albedo snow and icemore » <span class="hlt">cover</span>, cloud infrared emission dominates over cloud solar reflection/absorption leading to a positive net all-wave cloud radiative effect (CRE) at the surface, with all monthly means and 99.15% of instantaneous CRE values exceeding zero. The annual-mean CRE at theWAIS surface is 34 W m -2, representing a significant cloud-induced warming of the <span class="hlt">ice</span> sheet. Low-level liquid-containing clouds, including thin liquid water clouds implicated in radiative contributions to surface melting, are widespread and most frequent in WA during the austral summer. Clouds warm the WAIS by 26 W m -2, in summer, on average, despite maximum offsetting shortwave CRE. Glaciated cloud systems are strongly linked to orographic forcing, with maximum incidence on the WAIS continuing downstream along the Transantarctic Mountains.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1366350-west-antarctic-ice-sheet-cloud-cover-surface-radiation-budget-from-nasa-train-satellites','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1366350-west-antarctic-ice-sheet-cloud-cover-surface-radiation-budget-from-nasa-train-satellites"><span>West Antarctic <span class="hlt">Ice</span> Sheet cloud <span class="hlt">cover</span> and surface radiation budget from NASA A-Train satellites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Scott, Ryan C.; Lubin, Dan; Vogelmann, Andrew M.; ...</p> <p>2017-04-26</p> <p>Clouds are an essential parameter of the surface energy budget influencing the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS) response to atmospheric warming and net contribution to global sea-level rise. A four-year record of NASA A-Train cloud observations is combined with surface radiation measurements to quantify the WAIS radiation budget and constrain the three-dimensional occurrence frequency, thermodynamic phase partitioning, and surface radiative effect of clouds over West Antarctica (WA). The skill of satellite-modeled radiative fluxes is confirmed through evaluation against measurements at four Antarctic sites (WAIS Divide <span class="hlt">Ice</span> Camp, Neumayer, Syowa, and Concordia Stations). And due to perennial high-albedo snow and icemore » <span class="hlt">cover</span>, cloud infrared emission dominates over cloud solar reflection/absorption leading to a positive net all-wave cloud radiative effect (CRE) at the surface, with all monthly means and 99.15% of instantaneous CRE values exceeding zero. The annual-mean CRE at theWAIS surface is 34 W m -2, representing a significant cloud-induced warming of the <span class="hlt">ice</span> sheet. Low-level liquid-containing clouds, including thin liquid water clouds implicated in radiative contributions to surface melting, are widespread and most frequent in WA during the austral summer. Clouds warm the WAIS by 26 W m -2, in summer, on average, despite maximum offsetting shortwave CRE. Glaciated cloud systems are strongly linked to orographic forcing, with maximum incidence on the WAIS continuing downstream along the Transantarctic Mountains.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C43B0754M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C43B0754M"><span>Coordinated Mapping of Sea <span class="hlt">Ice</span> Deformation Features with Autonomous Vehicles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maksym, T.; Williams, G. D.; Singh, H.; Weissling, B.; Anderson, J.; Maki, T.; Ackley, S. F.</p> <p>2016-12-01</p> <p>Decreases in summer sea <span class="hlt">ice</span> extent in the Beaufort and Chukchi Seas has lead to a transition from a largely perennial <span class="hlt">ice</span> <span class="hlt">cover</span>, to a seasonal <span class="hlt">ice</span> <span class="hlt">cover</span>. This drives shifts in sea <span class="hlt">ice</span> production, dynamics, <span class="hlt">ice</span> types, and thickness distribution. To examine how the processes driving <span class="hlt">ice</span> advance might also impact the morphology of the <span class="hlt">ice</span> <span class="hlt">cover</span>, a coordinated <span class="hlt">ice</span> mapping effort was undertaken during a field campaign in the Beaufort Sea in October, 2015. Here, we present observations of sea <span class="hlt">ice</span> draft topography from six missions of an Autonomous Underwater Vehicle run under different <span class="hlt">ice</span> types and deformation features observed during autumn freeze-up. <span class="hlt">Ice</span> surface features were also mapped during coordinated drone photogrammetric missions over each site. We present preliminary results of a comparison between sea <span class="hlt">ice</span> surface topography and <span class="hlt">ice</span> underside morphology for a range of sample <span class="hlt">ice</span> types, including hummocked multiyear <span class="hlt">ice</span>, rubble fields, young <span class="hlt">ice</span> ridges and rafts, and consolidated pancake <span class="hlt">ice</span>. These data are compared to prior observations of <span class="hlt">ice</span> morphological features from deformed Antarctic sea <span class="hlt">ice</span>. Such data will be useful for improving parameterizations of sea <span class="hlt">ice</span> redistribution during deformation, and for better constraining estimates of airborne or satellite sea <span class="hlt">ice</span> thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC44B..03T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC44B..03T"><span>Multi-decadal Arctic sea <span class="hlt">ice</span> roughness.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsamados, M.; Stroeve, J.; Kharbouche, S.; Muller, J. P., , Prof; Nolin, A. W.; Petty, A.; Haas, C.; Girard-Ardhuin, F.; Landy, J.</p> <p>2017-12-01</p> <p>The transformation of Arctic sea <span class="hlt">ice</span> from mainly perennial, multi-year <span class="hlt">ice</span> to a seasonal, first-year <span class="hlt">ice</span> is believed to have been accompanied by a reduction of the roughness of the <span class="hlt">ice</span> <span class="hlt">cover</span> surface. This smoothening effect has been shown to (i) modify the momentum and heat transfer between the atmosphere and ocean, (ii) to alter the <span class="hlt">ice</span> thickness distribution which in turn controls the snow and melt pond repartition over the <span class="hlt">ice</span> <span class="hlt">cover</span>, and (iii) to bias airborne and satellite remote sensing measurements that depend on the scattering and reflective characteristics over the sea <span class="hlt">ice</span> surface topography. We will review existing and novel remote sensing methodologies proposed to estimate sea <span class="hlt">ice</span> roughness, ranging from airborne LIDAR measurement (ie Operation <span class="hlt">Ice</span>Bridge), to backscatter coefficients from scatterometers (ASCAT, QUICKSCAT), to multi angle maging spectroradiometer (MISR), and to laser (Icesat) and radar altimeters (Envisat, Cryosat, Altika, Sentinel-3). We will show that by comparing and cross-calibrating these different products we can offer a consistent multi-mission, multi-decadal view of the declining sea <span class="hlt">ice</span> roughness. Implications for sea <span class="hlt">ice</span> physics, climate and remote sensing will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28657626','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28657626"><span>From <span class="hlt">ice</span>-binding proteins to bio-inspired antifreeze materials.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Voets, I K</p> <p>2017-07-19</p> <p><span class="hlt">Ice</span>-binding proteins (IBP) facilitate survival under extreme conditions in diverse life forms. IBPs in polar fishes block further growth of internalized environmental <span class="hlt">ice</span> and inhibit <span class="hlt">ice</span> recrystallization of accumulated internal crystals. Algae use IBPs to structure <span class="hlt">ice</span>, while <span class="hlt">ice</span> adhesion is critical for the Antarctic bacterium Marinomonas primoryensis. Successful translation of this natural cryoprotective ability into man-made materials holds great promise but is still in its infancy. This review <span class="hlt">covers</span> recent advances in the field of <span class="hlt">ice</span>-binding proteins and their synthetic analogues, highlighting fundamental insights into IBP functioning as a foundation for the knowledge-<span class="hlt">based</span> development of cheap, bio-inspired mimics through scalable production routes. Recent advances in the utilisation of IBPs and their analogues to e.g. improve cryopreservation, <span class="hlt">ice</span>-templating strategies, gas hydrate inhibition and other technologies are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JGR....98.2561H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JGR....98.2561H"><span>Sensitivity study of a dynamic thermodynamic sea <span class="hlt">ice</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holland, David M.; Mysak, Lawrence A.; Manak, Davinder K.; Oberhuber, Josef M.</p> <p>1993-02-01</p> <p>A numerical simulation of the seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Arctic Ocean and the Greenland, Iceland, and Norwegian seas is presented. The sea <span class="hlt">ice</span> model is extracted from Oberhuber's (1990) coupled sea <span class="hlt">ice</span>-mixed layer-isopycnal general circulation model and is written in spherical coordinates. The advantage of such a model over previous sea <span class="hlt">ice</span> models is that it can be easily coupled to either global atmospheric or ocean general circulation models written in spherical coordinates. In this model, the thermodynamics are a modification of that of Parkinson and Washington (1979), while the dynamics use the full Hibler (1979) viscous-plastic rheology. Monthly thermodynamic and dynamic forcing fields for the atmosphere and ocean are specified. The simulations of the seasonal cycle of <span class="hlt">ice</span> thickness, compactness, and velocity, for a control set of parameters, compare favorably with the known seasonal characteristics of these fields. A sensitivity study of the control simulation of the seasonal sea <span class="hlt">ice</span> <span class="hlt">cover</span> is presented. The sensitivity runs are carried out under three different themes, namely, numerical conditions, parameter values, and physical processes. This last theme refers to experiments in which physical processes are either newly added or completely removed from the model. Approximately 80 sensitivity runs have been performed in which a change from the control run environment has been implemented. Comparisons have been made between the control run and a particular sensitivity run <span class="hlt">based</span> on time series of the seasonal cycle of the domain-averaged <span class="hlt">ice</span> thickness, compactness, areal coverage, and kinetic energy. In addition, spatially varying fields of <span class="hlt">ice</span> thickness, compactness, velocity, and surface temperature for each season are presented for selected experiments. A brief description and discussion of the more interesting experiments are presented. The simulation of the seasonal cycle of Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is shown to be robust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870007787&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmarginal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870007787&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmarginal"><span>Microwave properties of sea <span class="hlt">ice</span> in the marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Onstott, R. G.; Larson, R. W.</p> <p>1986-01-01</p> <p>Active microwave properties of summer sea <span class="hlt">ice</span> were measured. Backscatter data were acquired at frequencies from 1 to 17 GHz, at angles from 0 to 70 deg from vertical, and with like and cross antenna polarizations. Results show that melt-water, snow thickness, snowpack morphology, snow surface roughness, <span class="hlt">ice</span> surface roughness, and deformation characteristics are the fundamental scene parameters which govern the summer sea <span class="hlt">ice</span> backscatter response. A thick, wet snow <span class="hlt">cover</span> dominates the backscatter response and masks any <span class="hlt">ice</span> sheet features below. However, snow and melt-water are not distributed uniformly and the stage of melt may also be quite variable. These nonuniformities related to <span class="hlt">ice</span> type are not necessarily well understood and produce unique microwave signature characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C41D0429L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C41D0429L"><span>Multiscale Observation System for Sea <span class="hlt">Ice</span> Drift and Deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lensu, M.; Haapala, J. J.; Heiler, I.; Karvonen, J.; Suominen, M.</p> <p>2011-12-01</p> <p> combined with SAR images gives information on how large scale <span class="hlt">ice</span> <span class="hlt">cover</span> motions manifest as local scale deformations. The research includes also <span class="hlt">ice</span> stress measurements for relating the kinematic state and modeled stresses to local scale <span class="hlt">ice</span> <span class="hlt">cover</span> stresses, and <span class="hlt">ice</span> thickness mappings with profiling sonars and EM methods. Downscaling results <span class="hlt">based</span> on four-month campaing during winter 2011 are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009QSRv...28.3101G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009QSRv...28.3101G"><span>Reconstructing the last Irish <span class="hlt">Ice</span> Sheet 2: a geomorphologically-driven model of <span class="hlt">ice</span> sheet growth, retreat and dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greenwood, Sarah L.; Clark, Chris D.</p> <p>2009-12-01</p> <p>The <span class="hlt">ice</span> sheet that once <span class="hlt">covered</span> Ireland has a long history of investigation. Much prior work focussed on localised evidence-<span class="hlt">based</span> reconstructions and <span class="hlt">ice</span>-marginal dynamics and chronologies, with less attention paid to an <span class="hlt">ice</span> sheet wide view of the first order properties of the <span class="hlt">ice</span> sheet: centres of mass, <span class="hlt">ice</span> divide structure, <span class="hlt">ice</span> flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an <span class="hlt">ice</span> sheet reconstruction yielding these fundamental <span class="hlt">ice</span> sheet properties. We present a seven stage model of <span class="hlt">ice</span> sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of <span class="hlt">ice</span> from Scotland likely coalesced with local <span class="hlt">ice</span> caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish <span class="hlt">Ice</span> Sheet was then established during <span class="hlt">ice</span> sheet growth, with a branching <span class="hlt">ice</span> divide structure whose main axis migrated up to 140 km from the west coast towards the east. <span class="hlt">Ice</span> stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. <span class="hlt">Ice</span> <span class="hlt">cover</span> is reconstructed as extending to the continental shelf break. The Irish <span class="hlt">Ice</span> Sheet became autonomous (i.e. separate from the British <span class="hlt">Ice</span> Sheet) during deglaciation and fragmented into multiple <span class="hlt">ice</span> masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the <span class="hlt">ice</span> sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the <span class="hlt">ice</span> stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940007628&hterms=sea+ice+albedo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsea%2Bice%2Balbedo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940007628&hterms=sea+ice+albedo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsea%2Bice%2Balbedo"><span>Modern shelf <span class="hlt">ice</span>, equatorial Aeolis Quadrangle, Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brakenridge, G. R.</p> <p>1993-01-01</p> <p>As part of a detailed study of the geological and geomorphological evolution of Aeolis Quadrangle, I have encountered evidence suggesting that near surface <span class="hlt">ice</span> exists at low latitudes and was formed by partial or complete freezing of an inland sea. The area of interest is centered at approximately -2 deg, 196 deg. As seen in a suite of Viking Orbiter frames obtained at a range of approximately 600 km, the plains surface at this location is very lightly cratered or uncratered, and it is thus of late Amazonian age. Extant topographic data indicate that the Amazonian plains at this location occupy a trough whose surface lies at least 1000 m below the Mars datum. A reasonable hypothesis is that quite recent surface water releases, perhaps associated with final evolution of large 'outflow chasms' to the south, but possibly from other source areas, filled this trough, that <span class="hlt">ice</span> floes formed almost immediately, and that either grounded <span class="hlt">ice</span> or an <span class="hlt">ice-covered</span> sea still persists. A reasonable hypothesis is that quite recent surface water releases, perhaps associated with final evolution of large 'outflow chasms' to the south, but possibly from other source areas, filled this trough, that <span class="hlt">ice</span> floes formed almost immediately, and that either grounded <span class="hlt">ice</span> or an <span class="hlt">ice-covered</span> sea still persists. In either case, the thin (a few meters at most) high albedo, low thermal inertia <span class="hlt">cover</span> of aeolian materials was instrumental in allowing <span class="hlt">ice</span> preservation, and at least the lower portions of this dust <span class="hlt">cover</span> may be cemented by water <span class="hlt">ice</span>. Detailed mapping using Viking stereopairs and quantitative comparisons to terrestrial shelf <span class="hlt">ice</span> geometries are underway.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870020588','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870020588"><span>Satellite-derived <span class="hlt">ice</span> data sets no. 2: Arctic monthly average microwave brightness temperatures and sea <span class="hlt">ice</span> concentrations, 1973-1976</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, C. L.; Comiso, J. C.; Zwally, H. J.</p> <p>1987-01-01</p> <p>A summary data set for four years (mid 70's) of Arctic sea <span class="hlt">ice</span> conditions is available on magnetic tape. The data include monthly and yearly averaged Nimbus 5 electrically scanning microwave radiometer (ESMR) brightness temperatures, an <span class="hlt">ice</span> concentration parameter derived from the brightness temperatures, monthly climatological surface air temperatures, and monthly climatological sea level pressures. All data matrices are applied to 293 by 293 grids that <span class="hlt">cover</span> a polar stereographic map enclosing the 50 deg N latitude circle. The grid size varies from about 32 X 32 km at the poles to about 28 X 28 km at 50 deg N. The <span class="hlt">ice</span> concentration parameter is calculated assuming that the field of view contains only open water and first-year <span class="hlt">ice</span> with an <span class="hlt">ice</span> emissivity of 0.92. To account for the presence of multiyear <span class="hlt">ice</span>, a nomogram is provided relating the <span class="hlt">ice</span> concentration parameter, the total <span class="hlt">ice</span> concentration, and the fraction of the <span class="hlt">ice</span> <span class="hlt">cover</span> which is multiyear <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030004821','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030004821"><span>ICESat: <span class="hlt">Ice</span>, Cloud and Land Elevation Satellite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, Jay; Shuman, Christopher</p> <p>2002-01-01</p> <p><span class="hlt">Ice</span> exists in the natural environment in many forms. The Earth dynamic <span class="hlt">ice</span> features shows that at high elevations and/or high latitudes,snow that falls to the ground can gradually build up tu form thick consolidated <span class="hlt">ice</span> masses called glaciers. Glaciers flow downhill under the force of gravity and can extend into areas that are too warm to support year-round snow <span class="hlt">cover</span>. The snow line, called the equilibrium line on a glacier or <span class="hlt">ice</span> sheet, separates the <span class="hlt">ice</span> areas that melt on the surface and become show free in summer (net ablation zone) from the <span class="hlt">ice</span> area that remain snow <span class="hlt">covered</span> during the entire year (net accumulation zone). Snow near the surface of a glacier that is gradually being compressed into solid <span class="hlt">ice</span> is called firm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GApFD.111..411F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GApFD.111..411F"><span>The formation of <span class="hlt">ice</span> sails</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fowler, A. C.; Mayer, C.</p> <p>2017-11-01</p> <p>Debris-<span class="hlt">covered</span> glaciers are prone to the formation of a number of supraglacial geomorphological features, and generally speaking, their upper surfaces are far from level surfaces. Some of these features are due to radiation screening or enhancing properties of the debris <span class="hlt">cover</span>, but theoretical explanations of the consequent surface forms are in their infancy. In this paper we consider a theoretical model for the formation of "<span class="hlt">ice</span> sails", which are regularly spaced bare <span class="hlt">ice</span> features which are found on debris-<span class="hlt">covered</span> glaciers in the Karakoram.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C11B..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C11B..03P"><span>Airborne radar surveys of snow depth over Antarctic sea <span class="hlt">ice</span> during Operation <span class="hlt">Ice</span>Bridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panzer, B.; Gomez-Garcia, D.; Leuschen, C.; Paden, J. D.; Gogineni, P. S.</p> <p>2012-12-01</p> <p>Over the last decade, multiple satellite-<span class="hlt">based</span> laser and radar altimeters, optimized for polar observations, have been launched with one of the major objectives being the determination of global sea <span class="hlt">ice</span> thickness and distribution [5, 6]. Estimation of sea-<span class="hlt">ice</span> thickness from these altimeters relies on freeboard measurements and the presence of snow <span class="hlt">cover</span> on sea <span class="hlt">ice</span> affects this estimate. Current means of estimating the snow depth rely on daily precipitation products and/or data from passive microwave sensors [2, 7]. Even a small uncertainty in the snow depth leads to a large uncertainty in the sea-<span class="hlt">ice</span> thickness estimate. To improve the accuracy of the sea-<span class="hlt">ice</span> thickness estimates and provide validation for measurements from satellite-<span class="hlt">based</span> sensors, the Center for Remote Sensing of <span class="hlt">Ice</span> Sheets deploys the Snow Radar as a part of NASA Operation <span class="hlt">Ice</span>Bridge. The Snow Radar is an ultra-wideband, frequency-modulated, continuous-wave radar capable of resolving snow depth on sea <span class="hlt">ice</span> from 5 cm to more than 2 meters from long-range, airborne platforms [4]. This paper will discuss the algorithm used to directly extract snow depth estimates exclusively using the Snow Radar data set by tracking both the air-snow and snow-<span class="hlt">ice</span> interfaces. Prior work in this regard used data from a laser altimeter for tracking the air-snow interface or worked under the assumption that the return from the snow-<span class="hlt">ice</span> interface was greater than that from the air-snow interface due to a larger dielectric contrast, which is not true for thick or higher loss snow <span class="hlt">cover</span> [1, 3]. This paper will also present snow depth estimates from Snow Radar data during the NASA Operation <span class="hlt">Ice</span>Bridge 2010-2011 Antarctic campaigns. In 2010, three sea <span class="hlt">ice</span> flights were flown, two in the Weddell Sea and one in the Amundsen and Bellingshausen Seas. All three flight lines were repeated in 2011, allowing an annual comparison of snow depth. In 2011, a repeat pass of an earlier flight in the Weddell Sea was flown, allowing for a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=170301','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=170301"><span>Fecal indicator bacteria persistence under natural conditions in an <span class="hlt">ice-covered</span> river.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Davenport, C V; Sparrow, E B; Gordon, R C</p> <p>1976-01-01</p> <p>Total coliform (TC), fecal coliform (FC), and fecal streptococcus (FS) survival characteristics, under natural conditions at 0 degrees C in an <span class="hlt">ice-covered</span> river, were examined during February and March 1975. The membrane filter (MF) technique was used throughout the study, and the multiple-tube (MPN) method was used in parallel on three preselected days for comparative recovery of these bacteria. Survival was studied at seven sample stations downstream from all domestic pollution sources in a 317-km reach of the river having 7.1 days mean flow time (range of 6.0 to 9.1 days). The mean indicator bacteria densities decreased continuously at successive stations in this reach and, after adjustment for dilution, the most rapid die-off was found to occur during the first 1.9 days, followed by a slower decrease. After 7.1 days, the relative survival was TC less than FC less than FS, with 8.4%, 15.7%, and 32.8% of the initial populations remaining viable, respectively. These rates are higher than previously reported and suggest that the highest survival rates for these bacteria in receiving streams can be expected at 0 degree C under <span class="hlt">ice</span> <span class="hlt">cover</span>. Additionally, the FC-FS ratio was greater than 5 at all stations, indicating that this ratio may be useable for determining the source of fecal pollution in receiving streams for greater than 7 days flow time at low water temperatures. The MPN and MF methods gave comparable results for the TC and FS at all seven sample stations, with both the direct and verified MF counts within the 95% confidence limits of the respective MPNs in most samples, but generally lower than the MPN index. Although FC recovery on membrane filters was comparable results at stations near the pollution source. However, the results became more comparable with increasing flow time. The results of this study indicate that heat shock is a major factor in suppression of the FC counts on the membrane filters at 44.5 degree C. Heat shock may be minimized by extended</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27888351','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27888351"><span>Identity, ecology and ecophysiology of planktic green algae dominating in <span class="hlt">ice-covered</span> lakes on James Ross Island (northeastern Antarctic Peninsula).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nedbalová, Linda; Mihál, Martin; Kvíderová, Jana; Procházková, Lenka; Řezanka, Tomáš; Elster, Josef</p> <p>2017-01-01</p> <p>The aim of this study was to assess the phylogenetic relationships, ecology and ecophysiological characteristics of the dominant planktic algae in <span class="hlt">ice-covered</span> lakes on James Ross Island (northeastern Antarctic Peninsula). Phylogenetic analyses of 18S rDNA together with analysis of ITS2 rDNA secondary structure and cell morphology revealed that the two strains belong to one species of the genus Monoraphidium (Chlorophyta, Sphaeropleales, Selenastraceae) that should be described as new in future. Immotile green algae are thus apparently capable to become the dominant primary producer in the extreme environment of Antarctic lakes with extensive <span class="hlt">ice-cover</span>. The strains grew in a wide temperature range, but the growth was inhibited at temperatures above 20 °C, indicating their adaptation to low temperature. Preferences for low irradiances reflected the light conditions in their original habitat. Together with relatively high growth rates (0.4-0.5 day -1 ) and unprecedently high content of polyunsaturated fatty acids (PUFA, more than 70% of total fatty acids), it makes these isolates interesting candidates for biotechnological applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170000745','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170000745"><span>The <span class="hlt">Ice-Covered</span> Lakes Hypothesis in Gale Crater: Implications for the Early Hesperian Climate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kling, Alexandre M.; Haberle, Robert M.; McKay, Christopher P.; Bristow, Thomas F.; Rivera-Hernandez, Frances</p> <p>2017-01-01</p> <p>Recent geological discoveries from the Mars Science Laboratory (MSL), including stream and lake sedimentary deposits, provide evidence that Gale crater may have intermittently hosted a fluviol-acustine environment during the Hesperian, with individual lakes lasting for a period of tens to hundreds of thousands of years. Estimates of the CO2 content of the atmosphere at the time the Gale sediments formed are far less than needed by any climate model to warm early Mars, given the low solar energy input available at Mars 3.5 Gya. We have therefore explored the possibility that the lakes in Gale during the Hesperian were perennially <span class="hlt">covered</span> with <span class="hlt">ice</span> using the Antarctic lakes as analogs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11C0923F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11C0923F"><span>Improving Arctic Sea <span class="hlt">Ice</span> Observations and Data Access to Support Advances in Sea <span class="hlt">Ice</span> Forecasting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farrell, S. L.</p> <p>2017-12-01</p> <p>The economic and strategic importance of the Arctic region is becoming apparent. One of the most striking and widely publicized changes underway is the declining sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Since sea <span class="hlt">ice</span> is a key component of the climate system, its ongoing loss has serious, and wide-ranging, socio-economic implications. Increasing year-to-year variability in the geographic location, concentration, and thickness of the Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> will pose both challenges and opportunities. The sea <span class="hlt">ice</span> research community must be engaged in sustained Arctic Observing Network (AON) initiatives so as to deliver fit-for-purpose remote sensing data products to a variety of stakeholders including Arctic communities, the weather forecasting and climate modeling communities, industry, local, regional and national governments, and policy makers. An example of engagement is the work currently underway to improve research collaborations between scientists engaged in obtaining and assessing sea <span class="hlt">ice</span> observational data and those conducting numerical modeling studies and forecasting <span class="hlt">ice</span> conditions. As part of the US AON, in collaboration with the Interagency Arctic Research Policy Committee (IARPC), we are developing a strategic framework within which observers and modelers can work towards the common goal of improved sea <span class="hlt">ice</span> forecasting. Here, we focus on sea <span class="hlt">ice</span> thickness, a key varaible of the Arctic <span class="hlt">ice</span> <span class="hlt">cover</span>. We describe multi-sensor, and blended, sea <span class="hlt">ice</span> thickness data products under development that can be leveraged to improve model initialization and validation, as well as support data assimilation exercises. We will also present the new PolarWatch initiative (polarwatch.noaa.gov) and discuss efforts to advance access to remote sensing satellite observations and improve communication with Arctic stakeholders, so as to deliver data products that best address societal needs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120015900&hterms=export&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dexport','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120015900&hterms=export&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dexport"><span>Variability and Trends in Sea <span class="hlt">Ice</span> Extent and <span class="hlt">Ice</span> Production in the Ross Sea</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino; Kwok, Ronald; Martin, Seelye; Gordon, Arnold L.</p> <p>2011-01-01</p> <p>Salt release during sea <span class="hlt">ice</span> formation in the Ross Sea coastal regions is regarded as a primary forcing for the regional generation of Antarctic Bottom Water. Passive microwave data from November 1978 through 2008 are used to examine the detailed seasonal and interannual characteristics of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> of the Ross Sea and the adjacent Bellingshausen and Amundsen seas. For this period the sea <span class="hlt">ice</span> extent in the Ross Sea shows the greatest increase of all the Antarctic seas. Variability in the <span class="hlt">ice</span> <span class="hlt">cover</span> in these regions is linked to changes in the Southern Annular Mode and secondarily to the Antarctic Circumpolar Wave. Over the Ross Sea shelf, analysis of sea <span class="hlt">ice</span> drift data from 1992 to 2008 yields a positive rate of increase in the net <span class="hlt">ice</span> export of about 30,000 sq km/yr. For a characteristic <span class="hlt">ice</span> thickness of 0.6 m, this yields a volume transport of about 20 cu km/yr, which is almost identical, within error bars, to our estimate of the trend in <span class="hlt">ice</span> production. The increase in brine rejection in the Ross Shelf Polynya associated with the estimated increase with the <span class="hlt">ice</span> production, however, is not consistent with the reported Ross Sea salinity decrease. The locally generated sea <span class="hlt">ice</span> enhancement of Ross Sea salinity may be offset by an increase of relatively low salinity of the water advected into the region from the Amundsen Sea, a consequence of increased precipitation and regional glacial <span class="hlt">ice</span> melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B31D2022S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B31D2022S"><span>Developing A Model for Lake <span class="hlt">Ice</span> Phenology Using Satellite Remote Sensing Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skoglund, S. K.; Weathers, K. C.; Norouzi, H.; Prakash, S.; Ewing, H. A.</p> <p>2017-12-01</p> <p>Many northern temperate freshwater lakes are freezing over later and thawing earlier. This shift in timing, and the resulting shorter duration of seasonal <span class="hlt">ice</span> <span class="hlt">cover</span>, is expected to impact ecological processes, negatively affecting aquatic species and the quality of water we drink. Long-term, direct observations have been used to analyze changes in <span class="hlt">ice</span> phenology, but those data are sparse relative to the number of lakes affected. Here we develop a model to utilize remote sensing data in approximating the dates of <span class="hlt">ice</span>-on and <span class="hlt">ice</span>-off for many years over a variety of lakes. Day and night surface temperatures from MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra (MYD11A1 and MOD11A1 data products) for 2002-2017 were utilized in combination with observed <span class="hlt">ice</span>-on and <span class="hlt">ice</span>-off dates of Lake Auburn, Maine, to determine the ability of MODIS data to match ground-<span class="hlt">based</span> observations. A moving average served to interpolate MODIS temperature data to fill data gaps from cloudy days. The nighttime data were used for <span class="hlt">ice</span>-off, and the daytime measurements were used for <span class="hlt">ice</span>-on predictions to avoid fluctuations between day and night <span class="hlt">ice</span>/water status. The 0˚C intercepts of those data were used to mark approximate days of <span class="hlt">ice</span>-on or <span class="hlt">ice</span>-off. This revealed that approximations for <span class="hlt">ice</span>-off dates were satisfactory (average ±8.2 days) for Lake Auburn as well as for Lake Sunapee, New Hampshire (average ±8.1 days), while approximations for Lake Auburn <span class="hlt">ice</span>-on were less accurate and showed consistently earlier-than-observed <span class="hlt">ice</span>-on dates (average -33.8 days). The comparison of observed and remotely sensed Lake Auburn <span class="hlt">ice</span> <span class="hlt">cover</span> duration showed relative agreement with a correlation coefficient of 0.46. Other remote sensing observations, such as the new GOES-R satellite, and further exploration of the <span class="hlt">ice</span> formation process can improve <span class="hlt">ice</span>-on approximation methods. The model shows promise for estimating <span class="hlt">ice</span>-on, <span class="hlt">ice</span>-off, and <span class="hlt">ice</span> <span class="hlt">cover</span> duration for northern temperate lakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C43B0393W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C43B0393W"><span>Arctic Sea <span class="hlt">Ice</span> Predictability and the Sea <span class="hlt">Ice</span> Prediction Network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiggins, H. V.; Stroeve, J. C.</p> <p>2014-12-01</p> <p>Drastic reductions in Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> have increased the demand for Arctic sea <span class="hlt">ice</span> predictions by a range of stakeholders, including local communities, resource managers, industry and the public. The science of sea-<span class="hlt">ice</span> prediction has been challenged to keep up with these developments. Efforts such as the SEARCH Sea <span class="hlt">Ice</span> Outlook (SIO; http://www.arcus.org/sipn/sea-<span class="hlt">ice</span>-outlook) and the Sea <span class="hlt">Ice</span> for Walrus Outlook have provided a forum for the international sea-<span class="hlt">ice</span> prediction and observing community to explore and compare different approaches. The SIO, originally organized by the Study of Environmental Change (SEARCH), is now managed by the new Sea <span class="hlt">Ice</span> Prediction Network (SIPN), which is building a collaborative network of scientists and stakeholders to improve arctic sea <span class="hlt">ice</span> prediction. The SIO synthesizes predictions from a variety of methods, including heuristic and from a statistical and/or dynamical model. In a recent study, SIO data from 2008 to 2013 were analyzed. The analysis revealed that in some years the predictions were very successful, in other years they were not. Years that were anomalous compared to the long-term trend have proven more difficult to predict, regardless of which method was employed. This year, in response to feedback from users and contributors to the SIO, several enhancements have been made to the SIO reports. One is to encourage contributors to provide spatial probability maps of sea <span class="hlt">ice</span> <span class="hlt">cover</span> in September and the first day each location becomes <span class="hlt">ice</span>-free; these are an example of subseasonal to seasonal, local-scale predictions. Another enhancement is a separate analysis of the modeling contributions. In the June 2014 SIO report, 10 of 28 outlooks were produced from models that explicitly simulate sea <span class="hlt">ice</span> from dynamic-thermodynamic sea <span class="hlt">ice</span> models. Half of the models included fully-coupled (atmosphere, <span class="hlt">ice</span>, and ocean) models that additionally employ data assimilation. Both of these subsets (models and coupled models with data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP24A..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP24A..07D"><span>Greenland <span class="hlt">ice</span> cores tell tales on past sea level changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahl-Jensen, D.</p> <p>2017-12-01</p> <p>All the deep <span class="hlt">ice</span> cores drilled to the <span class="hlt">base</span> of the Greenland <span class="hlt">ice</span> sheet contain <span class="hlt">ice</span> from the previous warm climate period, the Eemian 130-115 thousand years before present. This demonstrates the resilience of the Greenland <span class="hlt">ice</span> sheet to a warming of 5 oC. Studies of basal material further reveal the presence of boreal forest over Greenland before <span class="hlt">ice</span> <span class="hlt">covered</span> Greenland. Conditions for Boreal forest implies temperatures at this time has been more than 10 oC warmer than the present. To compare the paleo-behavior of the Greenland <span class="hlt">ice</span> sheet to the present in relation to sea level rise knowledge gabs include the reaction of <span class="hlt">ice</span> streams to climate changes. To address this the international EGRIP-project is drilling an <span class="hlt">ice</span> core in the center of the North East Greenland <span class="hlt">Ice</span> Stream (NEGIS). The first results will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6032336','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/6032336"><span><span class="hlt">Ice</span> electrode electrolytic cell</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Glenn, D.F.; Suciu, D.F.; Harris, T.L.; Ingram, J.C.</p> <p>1993-04-06</p> <p>This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an <span class="hlt">ice</span> layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the <span class="hlt">ice</span>. The metal is then easily removed after melting the <span class="hlt">ice</span>. In a second embodiment, the same <span class="hlt">ice-covered</span> electrode can be employed to form powdered metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/868726','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/868726"><span><span class="hlt">Ice</span> electrode electrolytic cell</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Glenn, David F.; Suciu, Dan F.; Harris, Taryl L.; Ingram, Jani C.</p> <p>1993-01-01</p> <p>This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an <span class="hlt">ice</span> layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the <span class="hlt">ice</span>. The metal is then easily removed after melting the <span class="hlt">ice</span>. In a second embodiment, the same <span class="hlt">ice-covered</span> electrode can be employed to form powdered metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5708349','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5708349"><span>From <span class="hlt">ice</span>-binding proteins to bio-inspired antifreeze materials</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Voets, I. K.</p> <p>2017-01-01</p> <p><span class="hlt">Ice</span>-binding proteins (IBP) facilitate survival under extreme conditions in diverse life forms. IBPs in polar fishes block further growth of internalized environmental <span class="hlt">ice</span> and inhibit <span class="hlt">ice</span> recrystallization of accumulated internal crystals. Algae use IBPs to structure <span class="hlt">ice</span>, while <span class="hlt">ice</span> adhesion is critical for the Antarctic bacterium Marinomonas primoryensis. Successful translation of this natural cryoprotective ability into man-made materials holds great promise but is still in its infancy. This review <span class="hlt">covers</span> recent advances in the field of <span class="hlt">ice</span>-binding proteins and their synthetic analogues, highlighting fundamental insights into IBP functioning as a foundation for the knowledge-<span class="hlt">based</span> development of cheap, bio-inspired mimics through scalable production routes. Recent advances in the utilisation of IBPs and their analogues to e.g. improve cryopreservation, <span class="hlt">ice</span>-templating strategies, gas hydrate inhibition and other technologies are presented. PMID:28657626</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19778277','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19778277"><span>Laser-induced fluorescence emission (L.I.F.E.): in situ nondestructive detection of microbial life in the <span class="hlt">ice</span> <span class="hlt">covers</span> of Antarctic lakes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Storrie-Lombardi, Michael C; Sattler, Birgit</p> <p>2009-09-01</p> <p>Laser-induced fluorescence emission (L.I.F.E.) images were obtained in situ following 532 nm excitation of cryoconite assemblages in the <span class="hlt">ice</span> <span class="hlt">covers</span> of annual and perennially frozen Antarctic lakes during the 2008 Tawani International Expedition to Schirmacher Oasis and Lake Untersee in Dronning Maud Land, Antarctica. Laser targeting of a single millimeter-scale cryoconite results in multiple neighboring excitation events secondary to <span class="hlt">ice</span>/air interface reflection and refraction in the bubbles surrounding the primary target. Laser excitation at 532 nm of cyanobacteria-dominated assemblages produced red and infrared autofluorescence activity attributed to the presence of phycoerythrin photosynthetic pigments. The method avoids destruction of individual target organisms and does not require the disruption of either the structure of the microbial community or the surrounding <span class="hlt">ice</span> matrix. L.I.F.E. survey strategies described may be of interest for orbital monitoring of photosynthetic primary productivity in polar and alpine glaciers, <span class="hlt">ice</span> sheets, snow, and lake <span class="hlt">ice</span> of Earth's cryosphere. The findings open up the possibility of searching from either a rover or from orbit for signs of life in the polar regions of Mars and the frozen regions of exoplanets in neighboring star systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.C11B0430C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.C11B0430C"><span>Mining Existing Radar Altimetry for Sea <span class="hlt">Ice</span> Freeboard and Thickness Estimates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Childers, V. A.; Brozena, J. M.</p> <p>2007-12-01</p> <p>Although satellites can easily monitor <span class="hlt">ice</span> extent and a variety of <span class="hlt">ice</span> attributes, they cannot directly measure <span class="hlt">ice</span> thickness. As a result, very few <span class="hlt">ice</span> thickness measurements exist to constrain models of Arctic climate change. We estimated sea <span class="hlt">ice</span> freeboard and thickness from X-band radar altimeter measurements collected over seven field seasons between 1992 and 1999 as part of a Naval Research Lab (NRL)-sponsored airborne geophysical survey of gravity and magnetics over the Arctic Ocean. These freeboard and thickness estimates were compared with the SCICEX <span class="hlt">ice</span> draft record and the observed thinning of the Arctic Ocean <span class="hlt">ice</span> <span class="hlt">cover</span> during the 1990's. Our initial calculations (shown here) suggest that retrieved profiles from this radar altimeter (with uncertainty of about 5 cm) are sensitive to openings in the <span class="hlt">ice</span> <span class="hlt">cover</span>. Thus, conversion of these profiles to <span class="hlt">ice</span> thickness adds an invaluable dataset for assessment of recent and future changes of Arctic climate. And, snow loading is a minor issue here as all the airborne surveys were conducted during mid- to late-summer when the <span class="hlt">ice</span> <span class="hlt">cover</span> is mostly bare. The strengths of this dataset are its small antenna footprint of ~50 m and density of spatial coverage allows for detailed characterization of the field of <span class="hlt">ice</span> thickness, and it provides surveys of regions not <span class="hlt">covered</span> by SCICEX cruises. The entire survey <span class="hlt">covers</span> more than half the Arctic Ocean. We find that the Canadian Basin sea <span class="hlt">ice</span> behavior differs from that in the Eurasian Basin and ultimately affects mean sea <span class="hlt">ice</span> thickness for each basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601069','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601069"><span>The Seasonal Evolution of Sea <span class="hlt">Ice</span> Floe Size Distribution</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>the summer breakup of the <span class="hlt">ice</span> <span class="hlt">cover</span> . Large-scale, lower resolution imagery from MODIS and other platforms will also be analyzed to determine changes...control number. 1. REPORT DATE 30 SEP 2013 2. REPORT TYPE 3. DATES <span class="hlt">COVERED</span> 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE The Seasonal Evolution...appearance and morphology of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> over and annual cycle. These photos were taken over the pack <span class="hlt">ice</span> near SHEBA in May (left) and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990064090&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DParkinsons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990064090&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DParkinsons"><span>Variability of Arctic Sea <span class="hlt">Ice</span> as Viewed from Space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>1998-01-01</p> <p>Over the past 20 years, satellite passive-microwave radiometry has provided a marvelous means for obtaining information about the variability of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> and particularly about sea <span class="hlt">ice</span> concentrations (% areal coverages) and from them <span class="hlt">ice</span> extents and the lengths of the sea <span class="hlt">ice</span> season. This ability derives from the sharp contrast between the microwave emissions of sea <span class="hlt">ice</span> versus liquid water and allows routine monitoring of the vast Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, which typically varies in extent from a minimum of about 8,000,000 sq km in September to a maximum of about 15,000,000 sq km in March, the latter value being over 1.5 times the area of either the United States or Canada. The vast Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> has many impacts, including hindering heat, mass, and y momentum exchanges between the oceans and the atmosphere, reducing the amount of solar radiation absorbed at the Earth's surface, affecting freshwater transports and ocean circulation, and serving as a vital surface for many species of polar animals. These direct impacts also lead to indirect impacts, including effects on local and perhaps global atmospheric temperatures, effects that are being examined in general circulation modeling studies, where preliminary results indicate that changes on the order of a few percent sea <span class="hlt">ice</span> concentration can lead to temperature changes of 1 K or greater even in local areas outside of the sea <span class="hlt">ice</span> region. Satellite passive-microwave data for November 1978 through December 1996 reveal marked regional and interannual variabilities in both the <span class="hlt">ice</span> extents and the lengths of the sea <span class="hlt">ice</span> season, as well as some statistically significant trends. For the north polar <span class="hlt">ice</span> <span class="hlt">cover</span> as a whole, maximum <span class="hlt">ice</span> extents varied over a range of 14,700,000 - 15,900,000 km(2), while individual regions showed much greater percentage variations, e.g., with the Greenland Sea experiencing a range of 740,000 - 1,1110,000 km(2) in its yearly maximum <span class="hlt">ice</span> coverage. Although variations from year to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012982','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012982"><span>Thickness of <span class="hlt">ice</span> on perennially frozen lakes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McKay, C.P.; Clow, G.D.; Wharton, R.A.; Squyres, S. W.</p> <p>1985-01-01</p> <p>The dry valleys of southern Victoria Land, constituting the largest <span class="hlt">ice</span>-free expanse in the Antarctic, contain numerous lakes whose perennial <span class="hlt">ice</span> <span class="hlt">cover</span> is the cause of some unique physical and biological properties 1-3. Although the depth, temperature and salinity of the liquid water varies considerably from lake to lake, the thickness of the <span class="hlt">ice</span> <span class="hlt">cover</span> is remarkably consistent1, ranging from 3.5 to 6m, which is determined primarily by the balance between conduction of energy out of the <span class="hlt">ice</span> and the release of latent heat at the <span class="hlt">ice</span>-water interface and is also affected by the transmission and absorption of sunlight. In the steady state, the release of latent heat at the <span class="hlt">ice</span> bottom is controlled by ablation from the <span class="hlt">ice</span> surface. Here we present a simple energy-balance model, using the measured ablation rate of 30 cm yr-1, which can explain the observed <span class="hlt">ice</span> thickness. ?? 1985 Nature Publishing Group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918765S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918765S"><span>Under-<span class="hlt">ice</span> melt ponds in the Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Naomi; Flocco, Daniela; Feltham, Daniel</p> <p>2017-04-01</p> <p>In the summer months, melt water from the surface of the Arctic sea <span class="hlt">ice</span> can percolate down through the <span class="hlt">ice</span> and flow out of its <span class="hlt">base</span>. This water is relatively warm and fresh compared to the ocean water beneath it, and so it floats between the <span class="hlt">ice</span> and the oceanic mixed layer, forming pools of melt water called under-<span class="hlt">ice</span> melt ponds. Double diffusion can lead to the formation of a sheet of <span class="hlt">ice</span>, which is called a false bottom, at the interface between the fresh water and the ocean. These false bottoms isolate under-<span class="hlt">ice</span> melt ponds from the ocean below, trapping the fresh water against the sea <span class="hlt">ice</span>. These ponds and false bottoms have been estimated to <span class="hlt">cover</span> between 5 and 40% of the <span class="hlt">base</span> of the sea <span class="hlt">ice</span>. [Notz et al. Journal of Geophysical Research 2003] We have developed a one-dimensional thermodynamic model of sea <span class="hlt">ice</span> underlain by an under-<span class="hlt">ice</span> melt pond and false bottom. Not only has this allowed us to simulate the evolution of under-<span class="hlt">ice</span> melt ponds over time, identifying an alternative outcome than previously observed in the field, but sensitivity studies have helped us to estimate the impact that these pools of fresh water have on the mass-balance sea <span class="hlt">ice</span>. We have also found evidence of a possible positive feedback cycle whereby increasingly less <span class="hlt">ice</span> growth is seen due to the presence of under-<span class="hlt">ice</span> melt ponds as the Arctic warms. Since the rate of basal ablation is affected by these phenomena, their presence alters the salt and freshwater fluxes from the sea <span class="hlt">ice</span> into the ocean. We have coupled our under-<span class="hlt">ice</span> melt pond model to a simple model of the oceanic mixed layer to determine how this affects mixed layer properties such as temperature, salinity, and depth. In turn, this changes the oceanic forcing reaching the sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0827C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0827C"><span>Determining River <span class="hlt">Ice</span> Displacement Using the Differential Interferometry Synthetic Aperture Radar (D-InSAR) technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, T.; Lindenschmidt, K. E.</p> <p>2016-12-01</p> <p>Monitoring river <span class="hlt">ice</span> <span class="hlt">cover</span> dynamics during the course of winter is necessary to comprehend possible negative effects of <span class="hlt">ice</span> on anthropogenic systems and natural ecosystems to provide a basis to develop mitigation measures. Due to their large scale and limited accessibility to most places along river banks, especially in northern regions, remote sensing techniques are a suitable approach for monitoring river <span class="hlt">ice</span> regimes. Additionally, determining the vertical displacements of <span class="hlt">ice</span> <span class="hlt">covers</span> due to changes in flow provides an indication of vulnerable areas to initial cracking and breakup of the <span class="hlt">ice</span> <span class="hlt">cover</span>. Such information is paramount when deciding on suitable locations for winter road crossing along rivers. A number of RADARSAT-2 (RS-2) beam modes (i.e. Wide Fine, Wide Ultra-Fine, Wide Fine Quad Polarization and Spotlight) and D-InSAR methods were examined in this research to characterize slant range and vertical displacement of <span class="hlt">ice</span> <span class="hlt">covers</span> along the Slave River in the Northwest Territories, Canada. Our results demonstrate that the RS-2 Spotlight beam mode, processed by the Multiple Aperture InSAR (MAI) method, outperformed other beam modes and conventional InSAR when characterizing spatio-temporal patterns of <span class="hlt">ice</span> surface fluctuations. For example, the MAI <span class="hlt">based</span> Spotlight differential interferogram derived from the January and February 2016 images of the Slave River Delta resulted in a slant range displacement of the <span class="hlt">ice</span> surface between -3.3 and +3.6 cm (vertical displacement between -4.3 and +4.8 cm), due to the changes in river flow and river <span class="hlt">ice</span> morphology between the two acquisition dates. It is difficult to monitor the <span class="hlt">ice</span> movement in early and late winter periods due to the loss of phase coherence and error in phase unwrapping. These findings are consistent with our river <span class="hlt">ice</span> hydraulic modelling and visual interpretation of the river <span class="hlt">ice</span> processes under different hydrometeorological conditions and river <span class="hlt">ice</span> morphology. An extension of this study is planned to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970009603','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970009603"><span>Polarimetric Signatures of Sea <span class="hlt">Ice</span>. Part 1; Theoretical Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.</p> <p>1995-01-01</p> <p>Physical, structural, and electromagnetic properties and interrelating processes in sea <span class="hlt">ice</span> are used to develop a composite model for polarimetric backscattering signatures of sea <span class="hlt">ice</span>. Physical properties of sea <span class="hlt">ice</span> constituents such as <span class="hlt">ice</span>, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea <span class="hlt">ice</span> structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea <span class="hlt">ice</span>, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea <span class="hlt">ice</span> depend on crystal sizes and brine volumes, which are affected by <span class="hlt">ice</span> growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea <span class="hlt">ice</span> signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow <span class="hlt">cover</span>, brine skim, or slush layer. <span class="hlt">Based</span> on the same set of geophysical parameters characterizing sea <span class="hlt">ice</span>, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea <span class="hlt">ice</span> polarimetric signatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA617970','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA617970"><span>The Seasonal Evolution of Sea <span class="hlt">Ice</span> Floe Size Distribution</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>summer breakup of the <span class="hlt">ice</span> <span class="hlt">cover</span> . Large-scale, lower resolution imagery from MODIS and other platforms will also be analyzed to determine changes in floe...number. 1. REPORT DATE 30 SEP 2014 2. REPORT TYPE 3. DATES <span class="hlt">COVERED</span> 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE The Seasonal Evolution of Sea...morphology of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> over and annual cycle. These photos were taken over the pack <span class="hlt">ice</span> near SHEBA in May (left) and August (right</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70170886','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70170886"><span>Climate regulates alpine lake <span class="hlt">ice</span> <span class="hlt">cover</span> phenology and aquatic ecosystem structure</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T.J.</p> <p>2016-01-01</p> <p>High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that <span class="hlt">ice</span>-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in <span class="hlt">ice</span>-off timing. In the most well-studied lake, earlier <span class="hlt">ice</span>-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost <span class="hlt">ice</span> (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA259765','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA259765"><span>Active and Passive Remote Sensing of <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-01-26</p> <p>92 4. TITLE AND SUBTITLE S. FUNDING NUMBERS Active and Passive Remote Sensing of <span class="hlt">Ice</span> NO0014-89-J-l 107 6. AUTHOR(S) 425f023-08 Prof. J.A. Kong 7... REMOTE SENSING OF <span class="hlt">ICE</span> Sponsored by: Department of the Navy Office of Naval Research Contract number: N00014-89-J-1107 Research Organization: Center for...J. A. Kong Period <span class="hlt">covered</span>: October 1, 1988 - November 30, 1992 St ACTIVE AND PASSIVE REMOTE SENSING OF <span class="hlt">ICE</span> FINAL REPORT This annual report <span class="hlt">covers</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817671S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817671S"><span>Mapping and Assessing Variability in the Antarctic Marginal <span class="hlt">Ice</span> Zone, the Pack <span class="hlt">Ice</span> and Coastal Polynyas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, Julienne; Jenouvrier, Stephanie</p> <p>2016-04-01</p> <p>Sea <span class="hlt">ice</span> variability within the marginal <span class="hlt">ice</span> zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore mapping their spatial extent, seasonal and interannual variability is essential for understanding how current and future changes in these biological active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of different <span class="hlt">ice</span> types to the total Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> may also help to shed light on the factors contributing towards recent expansion of the Antarctic <span class="hlt">ice</span> <span class="hlt">cover</span> in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent data record for assessing different <span class="hlt">ice</span> types. However, estimates of the amount of MIZ, consolidated pack <span class="hlt">ice</span> and polynyas depends strongly on what sea <span class="hlt">ice</span> algorithm is used. This study uses two popular passive microwave sea <span class="hlt">ice</span> algorithms, the NASA Team and Bootstrap to evaluate the distribution and variability in the MIZ, the consolidated pack <span class="hlt">ice</span> and coastal polynyas. Results reveal the NASA Team algorithm has on average twice the MIZ and half the consolidated pack <span class="hlt">ice</span> area as the Bootstrap algorithm. Polynya area is also larger in the NASA Team algorithm, and the timing of maximum polynya area may differ by as much as 5 months between algorithms. These differences lead to different relationships between sea <span class="hlt">ice</span> characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4822014','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4822014"><span>Evidence for <span class="hlt">ice</span>-free summers in the late Miocene central Arctic Ocean</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stein, Ruediger; Fahl, Kirsten; Schreck, Michael; Knorr, Gregor; Niessen, Frank; Forwick, Matthias; Gebhardt, Catalina; Jensen, Laura; Kaminski, Michael; Kopf, Achim; Matthiessen, Jens; Jokat, Wilfried; Lohmann, Gerrit</p> <p>2016-01-01</p> <p>Although the permanently to seasonally <span class="hlt">ice-covered</span> Arctic Ocean is a unique and sensitive component in the Earth's climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP25 as a proxy for spring sea-<span class="hlt">ice</span> <span class="hlt">cover</span> and alkenone-<span class="hlt">based</span> summer sea-surface temperatures >4 °C that support a seasonal sea-<span class="hlt">ice</span> <span class="hlt">cover</span> with an <span class="hlt">ice</span>-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate. PMID:27041737</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011036','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011036"><span>Improving Surface Mass Balance Over <span class="hlt">Ice</span> Sheets and Snow Depth on Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan</p> <p>2013-01-01</p> <p>Surface mass balance (SMB) over <span class="hlt">ice</span> sheets and snow on sea <span class="hlt">ice</span> (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On <span class="hlt">ice</span> sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea <span class="hlt">ice</span> <span class="hlt">cover</span>. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland <span class="hlt">ice</span> sheet and the smallest satellite-recorded Arctic sea <span class="hlt">ice</span> extent, making this meeting both timely and relevant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1210S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1210S"><span>Towards development of an operational snow on sea <span class="hlt">ice</span> product</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J.; Liston, G. E.; Barrett, A. P.; Tschudi, M. A.; Stewart, S.</p> <p>2017-12-01</p> <p>Sea <span class="hlt">ice</span> has been visibly changing over the past couple of decades; most notably the annual minimum extent which has shown a distinct downward, and recently accelerating, trend. September mean sea <span class="hlt">ice</span> extent was over 7×106 km2 in the 1980's, but has averaged less than 5×106 km2 in the last decade. Should this loss continue, there will be wide-ranging impacts on marine ecosystems, coastal communities, prospects for resource extraction and marine activity, and weather conditions in the Arctic and beyond. While changes in the spatial extent of sea <span class="hlt">ice</span> have been routinely monitored since the 1970s, less is known about how the thickness of the <span class="hlt">ice</span> <span class="hlt">cover</span> has changed. While estimates of <span class="hlt">ice</span> thickness across the Arctic Ocean have become available over the past 20 years <span class="hlt">based</span> on data from ERS-1/2, Envisat, ICESat, CryoSat-2 satellites and Operation <span class="hlt">Ice</span>Bridge aircraft campaigns, the variety of these different measurement approaches, sensor technologies and spatial coverage present formidable challenges. Key among these is that measurement techniques do not measure <span class="hlt">ice</span> thickness directly - retrievals also require snow depth and density. Towards that end, a sophisticated snow accumulation model is tested in a Lagrangian framework to map daily snow depths across the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> using atmospheric reanalysis data as input. Accuracy of the snow accumulation is assessed through comparison with Operation <span class="hlt">Ice</span>Bridge data and <span class="hlt">ice</span> mass balance buoys (IMBs). Impacts on <span class="hlt">ice</span> thickness retrievals are further discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA02971&hterms=sea+world&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsea%2Bworld','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA02971&hterms=sea+world&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsea%2Bworld"><span>Comparative Views of Arctic Sea <span class="hlt">Ice</span> Growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2000-01-01</p> <p>NASA researchers have new insights into the mysteries of Arctic sea <span class="hlt">ice</span>, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts.<p/>Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete <span class="hlt">ice</span> <span class="hlt">cover</span> of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites.<p/>The two images above are separated by nine days (earlier image on the left). Both images represent an area (approximately 96 by 128 kilometers; 60 by 80 miles)located in the Baufort Sea, north of the Alaskan coast. The brighter features are older thicker <span class="hlt">ice</span> and the darker areas show young, recently formed <span class="hlt">ice</span>. Within the nine-day span, large and extensive cracks in the <span class="hlt">ice</span> <span class="hlt">cover</span> have formed due to <span class="hlt">ice</span> movement. These cracks expose the open ocean to the cold, frigid atmosphere where sea <span class="hlt">ice</span> grows rapidly and thickens.<p/>Using this new information, scientists at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., can generate comprehensive maps of Arctic sea <span class="hlt">ice</span> thickness for the first time. 'Before we knew only the extent of the <span class="hlt">ice</span> <span class="hlt">cover</span>,' said Dr. Ronald Kwok, JPL principal investigator of a project called Sea <span class="hlt">Ice</span> Thickness Derived From High Resolution Radar Imagery. 'We also knew that the sea <span class="hlt">ice</span> extent had decreased over the last 20 years, but we knew very little about <span class="hlt">ice</span> thickness.'<p/>'Since sea <span class="hlt">ice</span> is very thin, about 3 meters (10 feet) or less,'Kwok explained, 'it is very sensitive to climate change.'<p/>Until now, observations of polar sea <span class="hlt">ice</span> thickness have been available for specific areas, but not for the entire polar region.<p/>The new radar mapping technique has also given scientists a close look at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..297..217S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..297..217S"><span>Study of <span class="hlt">ice</span>-related flow features around Tanaica Montes, Mars: Implications for late amazonian debris-<span class="hlt">covered</span> glaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinha, Rishitosh K.; Vijayan, S.; Bharti, Rajiv R.</p> <p>2017-11-01</p> <p>Lobate debris aprons (LDA) and lineated valley fill (LVF) have been broadly recognized in the mid-latitudes of Mars and their subsequent analyses using data from the SHAllow RADar (SHARAD) instrument has suggested evidence for contemporary <span class="hlt">ice</span> preserved beneath these features. In this study, we conduct detailed characterization of newly identified LDA flow units within the Tanaica Montes region (39.55˚ N, 269.17˚ E) of Mars to assess and understand the similarities in their emplacement with respect to LDA flow units mapped in other regions of Mars. We utilize the Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) images and SHAllow RADar (SHARAD) datasets for geomorphic and subsurface analysis and Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) point tracks for topographic analysis. Geomorphic observation of LDA flow units surrounding the montes flanks and massif walls reveal integrated pattern of convergence and divergence and evidence of bending and deflection within the flow lines that resulted in concentric, loop-like flow patterns in the downslope. Brain-terrain texture and craters with varying morphological characteristics (ring-mold type) is suggestive that LDAs may be similar to <span class="hlt">ice</span>-rich, debris-<span class="hlt">covered</span> glaciers. MOLA point track <span class="hlt">based</span> convex-up topographic profiles of LDAs suggest that their thickness vary in the range of ∼100-200 m in both the northwestern and southeastern portions of study region. Further, the slope values of mapped LDA surfaces within the study region are within ∼0.1˚-4˚. The extent of mapped LDAs within the study region is such that some of the low elevation (∼0.8-1.3 km) portions of montes flanks are surrounded by relatively less extent (up to ∼0.5-0.8 km) of LDA flow units. Geomorphic and topographic evidence for flow units that appear to be superposed on the main LDA body collectively suggest the possibility of episodic glacial activity in the region. Furthermore, <span class="hlt">based</span> on the alignment of subsurface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.5521K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.5521K"><span>Seasonal sea <span class="hlt">ice</span> predictions for the Arctic <span class="hlt">based</span> on assimilation of remotely sensed observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kauker, F.; Kaminski, T.; Ricker, R.; Toudal-Pedersen, L.; Dybkjaer, G.; Melsheimer, C.; Eastwood, S.; Sumata, H.; Karcher, M.; Gerdes, R.</p> <p>2015-10-01</p> <p>The recent thinning and shrinking of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has increased the interest in seasonal sea <span class="hlt">ice</span> forecasts. Typical tools for such forecasts are numerical models of the coupled ocean sea <span class="hlt">ice</span> system such as the North Atlantic/Arctic Ocean Sea <span class="hlt">Ice</span> Model (NAOSIM). The model uses as input the initial state of the system and the atmospheric boundary condition over the forecasting period. This study investigates the potential of remotely sensed <span class="hlt">ice</span> thickness observations in constraining the initial model state. For this purpose it employs a variational assimilation system around NAOSIM and the Alfred Wegener Institute's CryoSat-2 <span class="hlt">ice</span> thickness product in conjunction with the University of Bremen's snow depth product and the OSI SAF <span class="hlt">ice</span> concentration and sea surface temperature products. We investigate the skill of predictions of the summer <span class="hlt">ice</span> conditions starting in March for three different years. Straightforward assimilation of the above combination of data streams results in slight improvements over some regions (especially in the Beaufort Sea) but degrades the over-all fit to independent observations. A considerable enhancement of forecast skill is demonstrated for a bias correction scheme for the CryoSat-2 <span class="hlt">ice</span> thickness product that uses a spatially varying scaling factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930037350&hterms=rate+sensitivity+ice&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drate%2Bsensitivity%2Bice','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930037350&hterms=rate+sensitivity+ice&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drate%2Bsensitivity%2Bice"><span>Ocean interactions with the <span class="hlt">base</span> of Amery <span class="hlt">Ice</span> Shelf, Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hellmer, Hartmut H.; Jacobs, Stanley S.</p> <p>1992-01-01</p> <p>Using a two-dimensional ocean themohaline circulation model, we varied the cavity shape beneath Amery <span class="hlt">Ice</span> Shelf in an attempt to reproduce the 150-m-thick marine <span class="hlt">ice</span> layer observed at the 'G1' <span class="hlt">ice</span> core site. Most simulations caused melting rates which decrease the <span class="hlt">ice</span> thickness by as much as 400 m between grounding line and G1, but produce only minor accumulation at the <span class="hlt">ice</span> core site and closer to the <span class="hlt">ice</span> front. Changes in the sea floor and <span class="hlt">ice</span> topographies revealed a high sensitivity of the basal mass balance to water column thickness near the grounding line, to submarine sills, and to discontinuities in <span class="hlt">ice</span> thickness. Model results showed temperature/salinity gradients similar to observations from beneath other <span class="hlt">ice</span> shelves where <span class="hlt">ice</span> is melting into seawater. Modeled outflow characteristics at the <span class="hlt">ice</span> front are in general agreement with oceanographic data from Prydz Bay. We concur with Morgan's inference that the G1 core may have been taken in a basal crevasse filled with marine <span class="hlt">ice</span>. This <span class="hlt">ice</span> is formed from water cooled by ocean/<span class="hlt">ice</span> shelf interactions along the interior <span class="hlt">ice</span> shelf <span class="hlt">base</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P53H..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P53H..03K"><span>Water <span class="hlt">ice</span> is water <span class="hlt">ice</span>: some applications and limitations of Earth analogues to Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koutnik, M.; Pathare, A.; Waddington, E. D.; Winebrenner, D. P.</p> <p>2017-12-01</p> <p> particular, we discuss why internal layers alone are not a diagnostic test for <span class="hlt">ice</span> flow. We also present progress in applying models of debris-<span class="hlt">covered</span> glacier flow to LDAs where dynamic debris <span class="hlt">cover</span>, <span class="hlt">ice</span> flow, and accumulation/ablation act to shape the <span class="hlt">ice</span>-mass surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4167550','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4167550"><span>Environmental Predictors of <span class="hlt">Ice</span> Seal Presence in the Bering Sea</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Miksis-Olds, Jennifer L.</p> <p>2014-01-01</p> <p><span class="hlt">Ice</span> seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and <span class="hlt">ice</span> <span class="hlt">covered</span> environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under <span class="hlt">ice</span>. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of <span class="hlt">ice</span> seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. <span class="hlt">Ice</span> <span class="hlt">cover</span> and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with <span class="hlt">ice</span> <span class="hlt">cover</span>) as potential predictors as well. <span class="hlt">Ice</span> seal presence showed a strong positive correlation with <span class="hlt">ice</span> <span class="hlt">cover</span> and a negative association with 10 kHz environmental sound. On average, there was a 20–30 dB difference between sound levels during solid <span class="hlt">ice</span> conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid <span class="hlt">ice</span> conditions by which <span class="hlt">ice</span> seals could orient. By constantly assessing the acoustic environment associated with the seasonal <span class="hlt">ice</span> movement in the Bering Sea, it is possible that <span class="hlt">ice</span> seals could utilize aspects of the soundscape to gauge their safe distance to open water or the <span class="hlt">ice</span> edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal <span class="hlt">ice</span> conditions and soundscapes are likely to change which may impact the ability of animals using <span class="hlt">ice</span> presence and cues to successfully function during the winter breeding season. PMID:25229453</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860058714&hterms=limnology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlimnology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860058714&hterms=limnology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlimnology"><span>Oxygen budget of a perennially <span class="hlt">ice-covered</span> Antarctic lake</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wharton, R. A., Jr.; Mckay, C. P.; Simmons, G. M., Jr.; Parker, B. C.</p> <p>1986-01-01</p> <p>A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as <span class="hlt">ice</span> by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. <span class="hlt">Based</span> on these results, it is suggested that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/gip/ice_age/ice_age.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/gip/ice_age/ice_age.pdf"><span>The Great <span class="hlt">Ice</span> Age</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ray, Louis L.</p> <p>1992-01-01</p> <p>The Great <span class="hlt">Ice</span> Age, a recent chapter in the Earth's history, was a period of recurring widespread glaciations. During the Pleistocene Epoch of the geologic time scale, which began about a million or more years ago, mountain glaciers formed on all continents, the icecaps of Antarctica and Greenland were more extensive and thicker than today, and vast glaciers, in places as much as several thousand feet thick, spread across northern North America and Eurasia. So extensive were these glaciers that almost a third of the present land surface of the Earth was intermittently <span class="hlt">covered</span> by <span class="hlt">ice</span>. Even today remnants of the great glaciers <span class="hlt">cover</span> almost a tenth of the land, indicating that conditions somewhat similar to those which produced the Great <span class="hlt">Ice</span> Age are still operating in polar and subpolar climates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E1409K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E1409K"><span>Evaluation of the operational SAR <span class="hlt">based</span> Baltic sea <span class="hlt">ice</span> concentration products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karvonen, Juha</p> <p></p> <p>Sea <span class="hlt">ice</span> concentration is an important <span class="hlt">ice</span> parameter both for weather and climate modeling and sea <span class="hlt">ice</span> navigation. We have developed an fully automated algorithm for sea <span class="hlt">ice</span> concentration retrieval using dual-polarized ScanSAR wide mode RADARSAT-2 data. RADARSAT-2 is a C-band SAR instrument enabling dual-polarized acquisition in ScanSAR mode. The swath width for the RADARSAT-2 ScanSAR mode is about 500 km, making it very suitable for operational sea <span class="hlt">ice</span> monitoring. The polarization combination used in our concentration estimation is HH/HV. The SAR data is first preprocessed, the preprocessing consists of geo-rectification to Mercator projection, incidence angle correction fro both the polarization channels. and SAR mosaicking. After preprocessing a segmentation is performed for the SAR mosaics, and some single-channel and dual-channel features are computed for each SAR segment. Finally the SAR concentration is estimated <span class="hlt">based</span> on these segment-wise features. The algorithm is similar as introduced in Karvonen 2014. The <span class="hlt">ice</span> concentration is computed daily using a daily RADARSAT-2 SAR mosaic as its input, and it thus gives the concentration estimated at each Baltic Sea location <span class="hlt">based</span> on the most recent SAR data at the location. The algorithm has been run in an operational test mode since January 2014. We present evaluation of the SAR-<span class="hlt">based</span> concentration estimates for the Baltic <span class="hlt">ice</span> season 2014 by comparing the SAR results with gridded the Finnish <span class="hlt">Ice</span> Service <span class="hlt">ice</span> charts and <span class="hlt">ice</span> concentration estimates from a radiometer algorithm (AMSR-2 Bootstrap algorithm results). References: J. Karvonen, Baltic Sea <span class="hlt">Ice</span> Concentration Estimation <span class="hlt">Based</span> on C-Band Dual-Polarized SAR Data, IEEE Transactions on Geoscience and Remote Sensing, in press, DOI: 10.1109/TGRS.2013.2290331, 2014.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020155','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020155"><span>Diatoms in sediments of perennially <span class="hlt">ice-covered</span> Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.</p> <p>1997-01-01</p> <p>Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially <span class="hlt">ice-covered</span> Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the <span class="hlt">ice</span> surface and are deposited episodically on the lake bottom. Benthic microbial mats are <span class="hlt">covered</span> in situ by the coarse episodic deposits, and the new surfaces are recolonized. <span class="hlt">Ice</span> <span class="hlt">cover</span> prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMES...9..854K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMES...9..854K"><span>LIVVkit: An extensible, python-<span class="hlt">based</span>, land <span class="hlt">ice</span> verification and validation toolkit for <span class="hlt">ice</span> sheet models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kennedy, Joseph H.; Bennett, Andrew R.; Evans, Katherine J.; Price, Stephen; Hoffman, Matthew; Lipscomb, William H.; Fyke, Jeremy; Vargo, Lauren; Boghozian, Adrianna; Norman, Matthew; Worley, Patrick H.</p> <p>2017-06-01</p> <p>To address the pressing need to better understand the behavior and complex interaction of <span class="hlt">ice</span> sheets within the global Earth system, significant development of continental-scale, dynamical <span class="hlt">ice</span> sheet models is underway. Concurrent to the development of the Community <span class="hlt">Ice</span> Sheet Model (CISM), the corresponding verification and validation (V&V) process is being coordinated through a new, robust, Python-<span class="hlt">based</span> extensible software package, the Land <span class="hlt">Ice</span> Verification and Validation toolkit (LIVVkit). Incorporated into the typical <span class="hlt">ice</span> sheet model development cycle, it provides robust and automated numerical verification, software verification, performance validation, and physical validation analyses on a variety of platforms, from personal laptops to the largest supercomputers. LIVVkit operates on sets of regression test and reference data sets, and provides comparisons for a suite of community prioritized tests, including configuration and parameter variations, bit-for-bit evaluation, and plots of model variables to indicate where differences occur. LIVVkit also provides an easily extensible framework to incorporate and analyze results of new intercomparison projects, new observation data, and new computing platforms. LIVVkit is designed for quick adaptation to additional <span class="hlt">ice</span> sheet models via abstraction of model specific code, functions, and configurations into an <span class="hlt">ice</span> sheet model description bundle outside the main LIVVkit structure. Ultimately, through shareable and accessible analysis output, LIVVkit is intended to help developers build confidence in their models and enhance the credibility of <span class="hlt">ice</span> sheet models overall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T23C1534E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T23C1534E"><span>Detrital zircon fission track analysis reveals the thermotectonic history of <span class="hlt">ice-covered</span> rocks of the Chugach-St. Elias orogen, SE-Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Enkelmann, E.; Garver, J. I.; Pavlis, T. L.; Bruhn, R. L.; Chapman, J. B.</p> <p>2007-12-01</p> <p>Investigating the exhumation history of the Chugach-St. Elias orogen (SE Alaska) using low-temperature thermochronometers is challenged by significant <span class="hlt">ice</span> <span class="hlt">cover</span>. Assuming exhumation drove cooling, cooling ages increase with elevation in an orogenic belt, and as such the youngest ages occur in valley bottoms. Cooling and exhumation rates are expected to be very high in the Chugach-St. Elias orogen due to efficient glacial erosion and the most intense erosion occurs under the major <span class="hlt">ice</span> fields. To study the cooling history of rapidly exhuming rocks underneath this <span class="hlt">ice</span> <span class="hlt">cover</span>, we analyzed detrital zircon fission track (DZFT) ages of Recent sand samples from modern rivers that drain the central Bagley <span class="hlt">Ice</span> field and smaller glaciers draining north (Chitina valley) and south (Pacific) of the mountain range. A distinct advantage of DZFT is that it allows one to sample a landscape regardless of accessibility. The youngest ZFT component populations of samples north and south of the Bagley <span class="hlt">Ice</span> field record a Late Miocene (5-13 Ma) cooling of the orogen. The pattern of cooling ages shows symmetry across the orogen predates the earliest record of the collision of the Yakutat terrane with Alaska. This result contrasts with the asymmetric cooling pattern displayed by low- temperature thermochronological ages (AFT and AHe) of the exposed bedrock within the range. Apatite FT and U- Th/He ages of bedrock samples south of the Bagley <span class="hlt">Ice</span> field record the syn-collisional (<5 Ma) fast exhumation whereas apatite ages to the north reveal more heterogeneous exhumation and vary widely from Miocene to Eocene. The bedrock samples from throughout the orogenic belt thus display predominantly the effects of the recent climatic situation of the mountain range with very high precipitation on the south, seaward side versus a more arid north side. Our ZFT results from the northern drainages highlight the relative sense and timing of two important fault zones, both accommodate south-side-up exhumation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMED33A0619H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMED33A0619H"><span><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby!</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamilton, C.</p> <p>2008-12-01</p> <p>The Center for Remote Sensing of <span class="hlt">Ice</span> Sheets (CReSIS) has developed an outreach program <span class="hlt">based</span> on hands-on activities called "<span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, density, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "<span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby" have successfully taught these to adults and students at informal events. The lessons are <span class="hlt">based</span> on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C31A..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C31A..01G"><span>Seasonal Changes of Arctic Sea <span class="hlt">Ice</span> Physical Properties Observed During N-<span class="hlt">ICE</span>2015: An Overview</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gerland, S.; Spreen, G.; Granskog, M. A.; Divine, D.; Ehn, J. K.; Eltoft, T.; Gallet, J. C.; Haapala, J. J.; Hudson, S. R.; Hughes, N. E.; Itkin, P.; King, J.; Krumpen, T.; Kustov, V. Y.; Liston, G. E.; Mundy, C. J.; Nicolaus, M.; Pavlov, A.; Polashenski, C.; Provost, C.; Richter-Menge, J.; Rösel, A.; Sennechael, N.; Shestov, A.; Taskjelle, T.; Wilkinson, J.; Steen, H.</p> <p>2015-12-01</p> <p>Arctic sea <span class="hlt">ice</span> is changing, and for improving the understanding of the cryosphere, data is needed to describe the status and processes controlling current seasonal sea <span class="hlt">ice</span> growth, change and decay. We present preliminary results from in-situ observations on sea <span class="hlt">ice</span> in the Arctic Basin north of Svalbard from January to June 2015. Over that time, the Norwegian research vessel «Lance» was moored to in total four <span class="hlt">ice</span> floes, drifting with the sea <span class="hlt">ice</span> and allowing an international group of scientists to conduct detailed research. Each drift lasted until the ship reached the marginal <span class="hlt">ice</span> zone and <span class="hlt">ice</span> started to break up, before moving further north and starting the next drift. The ship stayed within the area approximately 80°-83° N and 5°-25° E. While the expedition <span class="hlt">covered</span> measurements in the atmosphere, the snow and sea <span class="hlt">ice</span> system, and in the ocean, as well as biological studies, in this presentation we focus on physics of snow and sea <span class="hlt">ice</span>. Different <span class="hlt">ice</span> types could be investigated: young <span class="hlt">ice</span> in refrozen leads, first year <span class="hlt">ice</span>, and old <span class="hlt">ice</span>. Snow surveys included regular snow pits with standardized measurements of physical properties and sampling. Snow and <span class="hlt">ice</span> thickness were measured at stake fields, along transects with electromagnetics, and in drillholes. For quantifying <span class="hlt">ice</span> physical properties and texture, <span class="hlt">ice</span> cores were obtained regularly and analyzed. Optical properties of snow and <span class="hlt">ice</span> were measured both with fixed installed radiometers, and from mobile systems, a sledge and an ROV. For six weeks, the surface topography was scanned with a ground LIDAR system. Spatial scales of surveys ranged from spot measurements to regional surveys from helicopter (<span class="hlt">ice</span> thickness, photography) during two months of the expedition, and by means of an array of autonomous buoys in the region. Other regional information was obtained from SAR satellite imagery and from satellite <span class="hlt">based</span> radar altimetry. The analysis of the data collected has started, and first results will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930063976&hterms=1535&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D1535','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930063976&hterms=1535&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D1535"><span>Comparison of radar backscatter from Antarctic and Arctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hosseinmostafa, R.; Lytle, V.</p> <p>1992-01-01</p> <p>Two ship-<span class="hlt">based</span> step-frequency radars, one at C-band (5.3 GHz) and one at Ku-band (13.9 GHz), measured backscatter from <span class="hlt">ice</span> in the Weddell Sea. Most of the backscatter data were from first-year (FY) and second-year (SY) <span class="hlt">ice</span> at the <span class="hlt">ice</span> stations where the ship was stationary and detailed snow and <span class="hlt">ice</span> characterizations were performed. The presence of a slush layer at the snow-<span class="hlt">ice</span> interface masks the distinction between FY and SY <span class="hlt">ice</span> in the Weddell Sea, whereas in the Arctic the separation is quite distinct. The effect of snow-<span class="hlt">covered</span> <span class="hlt">ice</span> on backscattering coefficients (sigma0) from the Weddell Sea region indicates that surface scattering is the dominant factor. Measured sigma0 values were compared with Kirchhoff and regression-analysis models. The Weibull power-density function was used to fit the measured backscattering coefficients at 45 deg.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70157522','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70157522"><span>Lake <span class="hlt">ice</span> records used to detect historical and future climatic changes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Robertson, Dale M.; Ragotzkie, R.A.; Magnuson, John J.</p> <p>1992-01-01</p> <p>With the relationships between air temperature and freeze and break up dates, we can project how the <span class="hlt">ice</span> <span class="hlt">cover</span> of Lake Mendota should respond to future climatic changes. If warming occurs, the <span class="hlt">ice</span> <span class="hlt">cover</span> for Lake Mendota should decrease approximately 11 days per 1 °C increase. With a warming of 4 to 5 °C, years with no <span class="hlt">ice</span> <span class="hlt">cover</span> should occur in approximately 1 out of 15 to 30 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840019240','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840019240"><span>Satellite remote sensing over <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thomas, R. H.</p> <p>1984-01-01</p> <p>Satellite remote sensing provides unique opportunities for observing <span class="hlt">ice-covered</span> terrain. Passive-microwave data give information on snow extent on land, sea-<span class="hlt">ice</span> extent and type, and zones of summer melting on the polar <span class="hlt">ice</span> sheets, with the potential for estimating snow-accumulation rates on these <span class="hlt">ice</span> sheets. All weather, high-resolution imagery of sea <span class="hlt">ice</span> is obtained using synthetic aperture radars, and <span class="hlt">ice</span>-movement vectors can be deduced by comparing sequential images of the same region. Radar-altimetry data provide highly detailed information on <span class="hlt">ice</span>-sheet topography, with the potential for deducing thickening/thinning rates from repeat surveys. The coastline of Antarctica can be mapped accurately using altimetry data, and the size and spatial distribution of icebergs can be monitored. Altimetry data also distinguish open ocean from pack <span class="hlt">ice</span> and they give an indication of sea-<span class="hlt">ice</span> characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860043882&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAntarctic%2Bicebergs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860043882&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAntarctic%2Bicebergs"><span>Satellite remote sensing over <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thomas, R. H.</p> <p>1986-01-01</p> <p>Satellite remote sensing provides unique opportunities for observing <span class="hlt">ice-covered</span> terrain. Passive-microwave data give information on snow extent on land, sea-<span class="hlt">ice</span> extent and type, and zones of summer melting on the polar <span class="hlt">ice</span> sheets, with the potential for estimating snow-accumulation rates on these <span class="hlt">ice</span> sheets. All weather, high-resolution imagery of sea <span class="hlt">ice</span> is obtained using synthetic aperture radars, and <span class="hlt">ice</span>-movement vectors can be deduced by comparing sequential images of the same region. Radar-altimetry data provide highly detailed information on <span class="hlt">ice</span>-sheet topography, with the potential for deducing thickening/thinning rates from repeat surveys. The coastline of Antarctica can be mapped accurately using altimetry data, and the size and spatial distribution of icebergs can be monitored. Altimetry data also distinguish open ocean from pack <span class="hlt">ice</span> and they give an indication of sea-<span class="hlt">ice</span> characteristics.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C31A1151B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C31A1151B"><span>Influence of sea <span class="hlt">ice</span> on Arctic coasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnhart, K. R.; Kay, J. E.; Overeem, I.; Anderson, R. S.</p> <p>2017-12-01</p> <p>Coasts form the dynamic interface between the terrestrial and oceanic systems. In the Arctic, and in much of the world, the coast is a focal point for population, infrastructure, biodiversity, and ecosystem services. A key difference between Arctic and temperate coasts is the presence of sea <span class="hlt">ice</span>. Changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span> can influence the coast because (1) the length of the sea <span class="hlt">ice</span>-free season controls the time over which nearshore water can interact with the land, and (2) the location of the sea <span class="hlt">ice</span> edge controls the fetch over which storm winds can interact with open ocean water, which in turn governs nearshore water level and wave field. We first focus on the interaction of sea <span class="hlt">ice</span> and <span class="hlt">ice</span>-rich coasts. We combine satellite records of sea <span class="hlt">ice</span> with a model for wind-driven storm surge and waves to estimate how changes in the sea <span class="hlt">ice</span>-free season have impacted the nearshore hydrodynamic environment along Alaska's Beaufort Sea Coast for the period 1979-2012. This region has experienced some of the greatest changes in both sea <span class="hlt">ice</span> <span class="hlt">cover</span> and coastal erosion rates in the Arctic: the median length of the open-water season has expanded by 90 percent, while coastal erosion rates have more than doubled from 8.7 to 19 m yr-1. At Drew Point, NW winds increase shoreline water levels that control the incision of a submarine notch, the rate-limiting step of coastal retreat. The maximum water-level setup at Drew Point has increased consistently with increasing fetch. We extend our analysis to the entire Arctic using both satellite-<span class="hlt">based</span> observations and global coupled climate model output from the Community Earth System Model Large Ensemble (CESM-LE) project. This 30-member ensemble employs a 1-degree version of the CESM-CAM5 historical forcing for the period 1920-2005, and RCP 8.5 forcing from 2005-2100. A control model run with constant pre-industrial (1850) forcing characterizes internal variability in a constant climate. Finally, we compare observations and model results to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1352451-livvkit-extensible-python-based-land-ice-verification-validation-toolkit-ice-sheet-models','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1352451-livvkit-extensible-python-based-land-ice-verification-validation-toolkit-ice-sheet-models"><span>LIVVkit: An extensible, python-<span class="hlt">based</span>, land <span class="hlt">ice</span> verification and validation toolkit for <span class="hlt">ice</span> sheet models</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kennedy, Joseph H.; Bennett, Andrew R.; Evans, Katherine J.</p> <p></p> <p>To address the pressing need to better understand the behavior and complex interaction of <span class="hlt">ice</span> sheets within the global Earth system, significant development of continental-scale, dynamical <span class="hlt">ice</span> sheet models is underway. Concurrent to the development of the Community <span class="hlt">Ice</span> Sheet Model (CISM), the corresponding verification and validation (V&V) process is being coordinated through a new, robust, Python-<span class="hlt">based</span> extensible software package, the Land <span class="hlt">Ice</span> Verification and Validation toolkit (LIVVkit). Incorporated into the typical <span class="hlt">ice</span> sheet model development cycle, it provides robust and automated numerical verification, software verification, performance validation, and physical validation analyses on a variety of platforms, from personal laptopsmore » to the largest supercomputers. LIVVkit operates on sets of regression test and reference data sets, and provides comparisons for a suite of community prioritized tests, including configuration and parameter variations, bit-for-bit evaluation, and plots of model variables to indicate where differences occur. LIVVkit also provides an easily extensible framework to incorporate and analyze results of new intercomparison projects, new observation data, and new computing platforms. LIVVkit is designed for quick adaptation to additional <span class="hlt">ice</span> sheet models via abstraction of model specific code, functions, and configurations into an <span class="hlt">ice</span> sheet model description bundle outside the main LIVVkit structure. Furthermore, through shareable and accessible analysis output, LIVVkit is intended to help developers build confidence in their models and enhance the credibility of <span class="hlt">ice</span> sheet models overall.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1352451-livvkit-extensible-python-based-land-ice-verification-validation-toolkit-ice-sheet-models','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1352451-livvkit-extensible-python-based-land-ice-verification-validation-toolkit-ice-sheet-models"><span>LIVVkit: An extensible, python-<span class="hlt">based</span>, land <span class="hlt">ice</span> verification and validation toolkit for <span class="hlt">ice</span> sheet models</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Kennedy, Joseph H.; Bennett, Andrew R.; Evans, Katherine J.; ...</p> <p>2017-03-23</p> <p>To address the pressing need to better understand the behavior and complex interaction of <span class="hlt">ice</span> sheets within the global Earth system, significant development of continental-scale, dynamical <span class="hlt">ice</span> sheet models is underway. Concurrent to the development of the Community <span class="hlt">Ice</span> Sheet Model (CISM), the corresponding verification and validation (V&V) process is being coordinated through a new, robust, Python-<span class="hlt">based</span> extensible software package, the Land <span class="hlt">Ice</span> Verification and Validation toolkit (LIVVkit). Incorporated into the typical <span class="hlt">ice</span> sheet model development cycle, it provides robust and automated numerical verification, software verification, performance validation, and physical validation analyses on a variety of platforms, from personal laptopsmore » to the largest supercomputers. LIVVkit operates on sets of regression test and reference data sets, and provides comparisons for a suite of community prioritized tests, including configuration and parameter variations, bit-for-bit evaluation, and plots of model variables to indicate where differences occur. LIVVkit also provides an easily extensible framework to incorporate and analyze results of new intercomparison projects, new observation data, and new computing platforms. LIVVkit is designed for quick adaptation to additional <span class="hlt">ice</span> sheet models via abstraction of model specific code, functions, and configurations into an <span class="hlt">ice</span> sheet model description bundle outside the main LIVVkit structure. Furthermore, through shareable and accessible analysis output, LIVVkit is intended to help developers build confidence in their models and enhance the credibility of <span class="hlt">ice</span> sheet models overall.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.9903K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.9903K"><span>Airborne laser scanning <span class="hlt">based</span> quantification of dead-<span class="hlt">ice</span> melting in recently deglaciated terrain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klug, C.; Sailer, R.; Schümberg, M.; Stötter, J.</p> <p>2012-04-01</p> <p>Dead-<span class="hlt">ice</span> is explained as stagnant glacial <span class="hlt">ice</span>, not influenced by glacier flow anymore. Whenever glaciers have negative mass balances and an accumulation of debris-<span class="hlt">cover</span> on the surface, dead-<span class="hlt">ice</span> may form. Although, there are numerous conceptual process-sediment-landform models for the melt-out of dead-<span class="hlt">ice</span> bodies and areas of dead-<span class="hlt">ice</span> environments at glacier margins are easily accessible, just a few quantitative studies of dead-<span class="hlt">ice</span> melting have been carried out so far. Processes and rates of dead-<span class="hlt">ice</span> melting are commonly believed to be controlled by climate and debris-<span class="hlt">cover</span> properties, but there is still a lack of knowledge about this fact. This study has a focus on the quantification of process induced volumetric changes caused by dead-<span class="hlt">ice</span> melting. The research for this project was conducted at Hintereisferner (Ötztal Alps, Austria), Gepatschferner (Ötztal Alps, Austria) and Schrankar (Stubai Alps, Austria), areas for which a good data basis of ALS (Airborne Laser Scanning) measurements is available. 'Hintereisferner' can be characterized as a typical high alpine environment in mid-latitudes, which ranges between approximately 2250 m and 3740 m a.s.l.. The Hintereisferner region has been investigated intensively since many decades. Two dead <span class="hlt">ice</span> bodies at the orographic right side and one at the orographic left side of the Hintereisferner glacier terminus (approx. at 2500 m to 2550 m a.s.l.) were identified. Since 2001, ALS measurements have been carried out regularly at Hintereisferner resulting in a unique data record of 21 ALS flight campaigns, allowing long-term explorations of the two dead-<span class="hlt">ice</span> areas. The second study area of 'Gepatschferner' in the Kaunertal ranges between 2060 m and 3520 m a.s.l. and is the second largest glacier of Austria. Near the glacier tongue at the orographic right side a significant dead <span class="hlt">ice</span> body has formed. The ALS data used for quantification include a period of time of 4 years (2006 - 2010). 'Schrankar' is located in the Western</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840059709&hterms=Thorndike&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThorndike','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840059709&hterms=Thorndike&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThorndike"><span>Measuring the sea <span class="hlt">ice</span> floe size distribution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rothrock, D. A.; Thorndike, A. S.</p> <p>1984-01-01</p> <p>The sea <span class="hlt">ice</span> <span class="hlt">covering</span> the Arctic Ocean is broken into distinct pieces,called floes. In the summer, these floes, which have diameters ranging up to 100 km, are separated from each other by a region of open water. In the winter, floes still exist, but they are less easily identified. An understanding of the geometry of the <span class="hlt">ice</span> pack is of interest for a number of practical applications associated with transportation in <span class="hlt">ice-covered</span> seas and with the design of offshore structures intended to survive in the presence of <span class="hlt">ice</span>. The present investigation has the objective to clarify ideas about floe sizes and to propose techniques for measuring them. Measurements are presented with the primary aim to illustrate points of technique or approach. A preliminary discussion of the floe size distribution of sea <span class="hlt">ice</span> is devoted to questions of definition and of measurement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1014822','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1014822"><span>Using <span class="hlt">Ice</span> Predictions to Guide Submarines</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2016-01-01</p> <p>the Arctic Cap Nowcast/ Forecast System (ACNFS) in September 2013. The ACNFS consists of a coupled <span class="hlt">ice</span> -ocean model that assimilates available real...of the <span class="hlt">ice</span> <span class="hlt">cover</span>. The age of the sea <span class="hlt">ice</span> serves as an indicator of its physical properties including surface roughness, melt pond coverage, and...the Arctic Cap Nowcast/Forecast System (ACNFS). <span class="hlt">Ice</span> thickness is in meters for 11 September 2015. Thickness ranges from zero to five meters as shown</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601203','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601203"><span>Forecasting Future Sea <span class="hlt">Ice</span> Conditions in the MIZ: A Lagrangian Approach</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>www.mcgill.ca/meteo/people/tremblay LONG-TERM GOALS 1- Determine the source regions for sea <span class="hlt">ice</span> in the seasonally <span class="hlt">ice-covered</span> zones (SIZs...distribution of sea <span class="hlt">ice</span> <span class="hlt">cover</span> and transport pathways. 2- Improve our understanding of the strengths and/or limitations of GCM predictions of future...ocean currents, RGPS sea <span class="hlt">ice</span> deformation, Reanalysis surface wind , surface radiative fluxes, etc. Processing the large datasets involved is a tedious</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70040743','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70040743"><span>Walrus areas of use in the Chukchi Sea during sparse sea <span class="hlt">ice</span> <span class="hlt">cover</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jay, Chadwick V.; Fischbach, Anthony S.; Kochnev, Anatoly A.</p> <p>2012-01-01</p> <p>The Pacific walrus Odobenus rosmarus divergens feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering Seas and rests on sea <span class="hlt">ice</span> between foraging trips. With climate warming, <span class="hlt">ice</span>-free periods in the Chukchi Sea have increased and are projected to increase further in frequency and duration. We radio-tracked walruses to estimate areas of walrus foraging and occupancy in the Chukchi Sea from June to November of 2008 to 2011, years when sea <span class="hlt">ice</span> was sparse over the continental shelf in comparison to historical records. The earlier and more extensive sea <span class="hlt">ice</span> retreat in June to September, and delayed freeze-up of sea <span class="hlt">ice</span> in October to November, created conditions for walruses to arrive earlier and stay later in the Chukchi Sea than in the past. The lack of sea <span class="hlt">ice</span> over the continental shelf from September to October caused walruses to forage in nearshore areas instead of offshore areas as in the past. Walruses did not frequent the deep waters of the Arctic Basin when sea <span class="hlt">ice</span> retreated off the shelf. Walruses foraged in most areas they occupied, and areas of concentrated foraging generally corresponded to regions of high benthic biomass, such as in the northeastern (Hanna Shoal) and southwestern Chukchi Sea. A notable exception was the occurrence of concentrated foraging in a nearshore area of northwestern Alaska that is apparently depauperate in walrus prey. With increasing sea <span class="hlt">ice</span> loss, it is likely that walruses will increase their use of coastal haul-outs and nearshore foraging areas, with consequences to the population that are yet to be understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GeoRL..35.8501D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GeoRL..35.8501D"><span>Calcium carbonate as ikaite crystals in Antarctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dieckmann, Gerhard S.; Nehrke, Gernot; Papadimitriou, Stathys; Göttlicher, Jörg; Steininger, Ralph; Kennedy, Hilary; Wolf-Gladrow, Dieter; Thomas, David N.</p> <p>2008-04-01</p> <p>We report on the discovery of the mineral ikaite (CaCO3.6H2O) in sea-<span class="hlt">ice</span> from the Southern Ocean. The precipitation of CaCO3 during the freezing of seawater has previously been predicted from thermodynamic modelling, indirect measurements, and has been documented in artificial sea <span class="hlt">ice</span> during laboratory experiments but has not been reported for natural sea-<span class="hlt">ice</span>. It is assumed that CaCO3 formation in sea <span class="hlt">ice</span> may be important for a sea <span class="hlt">ice</span>-driven carbon pump in <span class="hlt">ice-covered</span> oceanic waters. Without direct evidence of CaCO3 precipitation in sea <span class="hlt">ice</span>, its role in this and other processes has remained speculative. The discovery of CaCO3.6H2O crystals in natural sea <span class="hlt">ice</span> provides the necessary evidence for the evaluation of previous assumptions and lays the foundation for further studies to help elucidate the role of ikaite in the carbon cycle of the seasonally sea <span class="hlt">ice-covered</span> regions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5371420','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5371420"><span>The frequency and extent of sub-<span class="hlt">ice</span> phytoplankton blooms in the Arctic Ocean</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Horvat, Christopher; Jones, David Rees; Iams, Sarah; Schroeder, David; Flocco, Daniela; Feltham, Daniel</p> <p>2017-01-01</p> <p>In July 2011, the observation of a massive phytoplankton bloom underneath a sea ice–<span class="hlt">covered</span> region of the Chukchi Sea shifted the scientific consensus that regions of the Arctic Ocean <span class="hlt">covered</span> by sea <span class="hlt">ice</span> were inhospitable to photosynthetic life. Although the impact of widespread phytoplankton blooms under sea <span class="hlt">ice</span> on Arctic Ocean ecology and carbon fixation is potentially marked, the prevalence of these events in the modern Arctic and in the recent past is, to date, unknown. We investigate the timing, frequency, and evolution of these events over the past 30 years. Although sea <span class="hlt">ice</span> strongly attenuates solar radiation, it has thinned significantly over the past 30 years. The thinner summertime Arctic sea <span class="hlt">ice</span> is increasingly <span class="hlt">covered</span> in melt ponds, which permit more light penetration than bare or snow-<span class="hlt">covered</span> <span class="hlt">ice</span>. Our model results indicate that the recent thinning of Arctic sea <span class="hlt">ice</span> is the main cause of a marked increase in the prevalence of light conditions conducive to sub-<span class="hlt">ice</span> blooms. We find that as little as 20 years ago, the conditions required for sub-<span class="hlt">ice</span> blooms may have been uncommon, but their frequency has increased to the point that nearly 30% of the <span class="hlt">ice-covered</span> Arctic Ocean in July permits sub-<span class="hlt">ice</span> blooms. Recent climate change may have markedly altered the ecology of the Arctic Ocean. PMID:28435859</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17..233W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17..233W"><span>The Antarctic <span class="hlt">Ice</span> Sheet during the last Interglaciation: Insights from my Thesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whipple, Matthew; Lunt, Dan; Singarayer, Joy; Bradley, Sarah; Milne, Glenn; Wolff, Eric; Siddall, Mark</p> <p>2015-04-01</p> <p>The last interglaciation represents a period of warmer climates and higher sea levels, and a useful analogue to future climate. While many studies have focussed on the response of the Greenland <span class="hlt">Ice</span> sheet, far less is known about the response of the Antarctic <span class="hlt">ice</span> sheet. Here, I present the summarised results of my PhD thesis "Constraints on the minimum extent of the Antarctic <span class="hlt">ice</span> sheet during the last interglaciation". Firstly, I <span class="hlt">cover</span> the timings of interglaciation in Antarctica, and their differences with respect to the Northern Hemisphere timings, <span class="hlt">based</span> on paleo sea level indicators, and oceanic temperature records. I move on to <span class="hlt">cover</span> climate forcings, and how they influence the <span class="hlt">ice</span> sheet, relative to present, and early Holocene. Secondly, I present thesis results, from looking at <span class="hlt">ice</span> core stable water isotopes. These are compared with Isostatic and Climatic modelling results, for various different <span class="hlt">Ice</span> sheet scenarios, as to the resulting Climate, from changes in Elevation, Temperature, Precipitation, and Sublimation, all contributing to the recorded stable water isotope record. Thirdly, I move on to looking at the mid-field relative sea level records, from Australia and Argentina. Using isostatic modelling, these are used to assess the relative contribution of the Eastern and Western Antarctic <span class="hlt">Ice</span> sheets. Although data uncertainties result in us being to identify the contribution from West Antarctica. Overall, using model-data comparison, we find a lack of evidence for a substantial retreat of the Wilkes Subglacial basin. No data location is close enough to determine the existence of the marine <span class="hlt">based</span> West Antarctic <span class="hlt">Ice</span> sheet. Model uncertainty is unable to constrain evidence of variations in <span class="hlt">ice</span> thickness in East Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1612477L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1612477L"><span>Ship speeds and sea <span class="hlt">ice</span> forecasts - how are they related?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loeptien, Ulrike; Axell, Lars</p> <p>2014-05-01</p> <p>The Baltic Sea is a shallow marginal sea, located in northern Europe. A seasonally occurring sea <span class="hlt">ice</span> <span class="hlt">cover</span> has the potential to hinder the intense ship traffic substantially. There are thus considerable efforts to fore- and nowcast <span class="hlt">ice</span> conditions. Here we take a somewhat opposite approach and relate ship speeds, as observed via the Automatic Identification System (AIS) network, back to the prevailing sea <span class="hlt">ice</span> conditions. We show that these information are useful to constrain fore- and nowcasts. More specifically we find, by fitting a statistical model (mixed effect model) for a test region in the Bothnian Bay, that the forecasted <span class="hlt">ice</span> properties can explain 60-65% of the ship speed variations (<span class="hlt">based</span> on 25 minute averages).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2010/1176/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2010/1176/"><span>Arctic sea <span class="hlt">ice</span> decline: Projected changes in timing and extent of sea <span class="hlt">ice</span> in the Bering and Chukchi Seas</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Douglas, David C.</p> <p>2010-01-01</p> <p>The Arctic region is warming faster than most regions of the world due in part to increasing greenhouse gases and positive feedbacks associated with the loss of snow and <span class="hlt">ice</span> <span class="hlt">cover</span>. One consequence has been a rapid decline in Arctic sea <span class="hlt">ice</span> over the past 3 decades?a decline that is projected to continue by state-of-the-art models. Many stakeholders are therefore interested in how global warming may change the timing and extent of sea <span class="hlt">ice</span> Arctic-wide, and for specific regions. To inform the public and decision makers of anticipated environmental changes, scientists are striving to better understand how sea <span class="hlt">ice</span> influences ecosystem structure, local weather, and global climate. Here, projected changes in the Bering and Chukchi Seas are examined because sea <span class="hlt">ice</span> influences the presence of, or accessibility to, a variety of local resources of commercial and cultural value. In this study, 21st century sea <span class="hlt">ice</span> conditions in the Bering and Chukchi Seas are <span class="hlt">based</span> on projections by 18 general circulation models (GCMs) prepared for the fourth reporting period by the Intergovernmental Panel on Climate Change (IPCC) in 2007. Sea <span class="hlt">ice</span> projections are analyzed for each of two IPCC greenhouse gas forcing scenarios: the A1B `business as usual? scenario and the A2 scenario that is somewhat more aggressive in its CO2 emissions during the second half of the century. A large spread of uncertainty among projections by all 18 models was constrained by creating model subsets that excluded GCMs that poorly simulated the 1979-2008 satellite record of <span class="hlt">ice</span> extent and seasonality. At the end of the 21st century (2090-2099), median sea <span class="hlt">ice</span> projections among all combinations of model ensemble and forcing scenario were qualitatively similar. June is projected to experience the least amount of sea <span class="hlt">ice</span> loss among all months. For the Chukchi Sea, projections show extensive <span class="hlt">ice</span> melt during July and <span class="hlt">ice</span>-free conditions during August, September, and October by the end of the century, with high agreement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41D0732M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41D0732M"><span>Object-<span class="hlt">Based</span> Arctic Sea <span class="hlt">Ice</span> Feature Extraction through High Spatial Resolution Aerial photos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miao, X.; Xie, H.</p> <p>2015-12-01</p> <p>High resolution aerial photographs used to detect and classify sea <span class="hlt">ice</span> features can provide accurate physical parameters to refine, validate, and improve climate models. However, manually delineating sea <span class="hlt">ice</span> features, such as melt ponds, submerged <span class="hlt">ice</span>, water, <span class="hlt">ice</span>/snow, and pressure ridges, is time-consuming and labor-intensive. An object-<span class="hlt">based</span> classification algorithm is developed to automatically extract sea <span class="hlt">ice</span> features efficiently from aerial photographs taken during the Chinese National Arctic Research Expedition in summer 2010 (CHINARE 2010) in the MIZ near the Alaska coast. The algorithm includes four steps: (1) the image segmentation groups the neighboring pixels into objects <span class="hlt">based</span> on the similarity of spectral and textural information; (2) the random forest classifier distinguishes four general classes: water, general submerged <span class="hlt">ice</span> (GSI, including melt ponds and submerged <span class="hlt">ice</span>), shadow, and <span class="hlt">ice</span>/snow; (3) the polygon neighbor analysis separates melt ponds and submerged <span class="hlt">ice</span> <span class="hlt">based</span> on spatial relationship; and (4) pressure ridge features are extracted from shadow <span class="hlt">based</span> on local illumination geometry. The producer's accuracy of 90.8% and user's accuracy of 91.8% are achieved for melt pond detection, and shadow shows a user's accuracy of 88.9% and producer's accuracies of 91.4%. Finally, pond density, pond fraction, <span class="hlt">ice</span> floes, mean <span class="hlt">ice</span> concentration, average ridge height, ridge profile, and ridge frequency are extracted from batch processing of aerial photos, and their uncertainties are estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C32B..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C32B..01T"><span>Some Results on Sea <span class="hlt">Ice</span> Rheology for the Seasonal <span class="hlt">Ice</span> Zone, Obtained from the Deformation Field of Sea <span class="hlt">Ice</span> Drift Pattern</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toyota, T.; Kimura, N.</p> <p>2017-12-01</p> <p>Sea <span class="hlt">ice</span> rheology which relates sea <span class="hlt">ice</span> stress to the large-scale deformation of the <span class="hlt">ice</span> <span class="hlt">cover</span> has been a big issue to numerical sea <span class="hlt">ice</span> modelling. At present the treatment of internal stress within sea <span class="hlt">ice</span> area is <span class="hlt">based</span> mostly on the rheology formulated by Hibler (1979), where the whole sea <span class="hlt">ice</span> area behaves like an isotropic and plastic matter under the ordinary stress with the yield curve given by an ellipse with an aspect ratio (e) of 2, irrespective of sea <span class="hlt">ice</span> area and horizontal resolution of the model. However, this formulation was initially developed to reproduce the seasonal variation of the perennial <span class="hlt">ice</span> in the Arctic Ocean. As for its applicability to the seasonal <span class="hlt">ice</span> zones (SIZ), where various types of sea <span class="hlt">ice</span> are present, it still needs validation from observational data. In this study, the validity of this rheology was examined for the Sea of Okhotsk <span class="hlt">ice</span>, typical of the SIZ, <span class="hlt">based</span> on the AMSR-derived <span class="hlt">ice</span> drift pattern in comparison with the result obtained for the Beaufort Sea. To examine the dependence on a horizontal scale, the coastal radar data operated near the Hokkaido coast, Japan, were also used. <span class="hlt">Ice</span> drift pattern was obtained by a maximum cross-correlation method with grid spacings of 37.5 km from the 89 GHz brightness temperature of AMSR-E for the entire Sea of Okhotsk and the Beaufort Sea and 1.3 km from the coastal radar for the near-shore Sea of Okhotsk. The validity of this rheology was investigated from a standpoint of work rate done by deformation field, following the theory of Rothrock (1975). In analysis, the relative rates of convergence were compared between theory and observation to check the shape of yield curve, and the strain ellipse at each grid cell was estimated to see the horizontal variation of deformation field. The result shows that the ellipse of e=1.7-2.0 as the yield curve represents the observed relative conversion rates well for all the <span class="hlt">ice</span> areas. Since this result corresponds with the yield criterion by Tresca and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17843316','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17843316"><span>Physical conditions at the <span class="hlt">base</span> of a fast moving antarctic <span class="hlt">ice</span> stream.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Engelhardt, H; Humphrey, N; Kamb, B; Fahnestock, M</p> <p>1990-04-06</p> <p>Boreholes drilled to the bottom of <span class="hlt">ice</span> stream B in the West Antarctic <span class="hlt">Ice</span> Sheet reveal that the <span class="hlt">base</span> of the <span class="hlt">ice</span> stream is at the melting point and the basal water pressure is within about 1.6 bars of the <span class="hlt">ice</span> overburden pressure. These conditions allow the rapid <span class="hlt">ice</span> streaming motion to occur by basal sliding or by shear deformation of unconsolidated sediments that underlie the <span class="hlt">ice</span> in a layer at least 2 meters thick. The mechanics of <span class="hlt">ice</span> streaming plays a role in the response of the <span class="hlt">ice</span> sheet to climatic change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123...90L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123...90L"><span>Under-<span class="hlt">Ice</span> Phytoplankton Blooms Inhibited by Spring Convective Mixing in Refreezing Leads</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lowry, Kate E.; Pickart, Robert S.; Selz, Virginia; Mills, Matthew M.; Pacini, Astrid; Lewis, Kate M.; Joy-Warren, Hannah L.; Nobre, Carolina; van Dijken, Gert L.; Grondin, Pierre-Luc; Ferland, Joannie; Arrigo, Kevin R.</p> <p>2018-01-01</p> <p>Spring phytoplankton growth in polar marine ecosystems is limited by light availability beneath <span class="hlt">ice-covered</span> waters, particularly early in the season prior to snowmelt and melt pond formation. Leads of open water increase light transmission to the <span class="hlt">ice-covered</span> ocean and are sites of air-sea exchange. We explore the role of leads in controlling phytoplankton bloom dynamics within the sea <span class="hlt">ice</span> zone of the Arctic Ocean. Data are presented from spring measurements in the Chukchi Sea during the Study of Under-<span class="hlt">ice</span> Blooms In the Chukchi Ecosystem (SUBICE) program in May and June 2014. We observed that fully consolidated sea <span class="hlt">ice</span> supported modest under-<span class="hlt">ice</span> blooms, while waters beneath sea <span class="hlt">ice</span> with leads had significantly lower phytoplankton biomass, despite high nutrient availability. Through an analysis of hydrographic and biological properties, we attribute this counterintuitive finding to springtime convective mixing in refreezing leads of open water. Our results demonstrate that waters beneath loosely consolidated sea <span class="hlt">ice</span> (84-95% <span class="hlt">ice</span> concentration) had weak stratification and were frequently mixed below the critical depth (the depth at which depth-integrated production balances depth-integrated respiration). These findings are supported by theoretical model calculations of under-<span class="hlt">ice</span> light, primary production, and critical depth at varied lead fractions. The model demonstrates that under-<span class="hlt">ice</span> blooms can form even beneath snow-<span class="hlt">covered</span> sea <span class="hlt">ice</span> in the absence of mixing but not in more deeply mixed waters beneath sea <span class="hlt">ice</span> with refreezing leads. Future estimates of primary production should account for these phytoplankton dynamics in <span class="hlt">ice-covered</span> waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A"><span>Interactions Between <span class="hlt">Ice</span> Thickness, Bottom <span class="hlt">Ice</span> Algae, and Transmitted Spectral Irradiance in the Chukchi Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arntsen, A. E.; Perovich, D. K.; Polashenski, C.; Stwertka, C.</p> <p>2015-12-01</p> <p>The amount of light that penetrates the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> impacts sea-<span class="hlt">ice</span> mass balance as well as ecological processes in the upper ocean. The seasonally evolving macro and micro spatial variability of transmitted spectral irradiance observed in the Chukchi Sea from May 18 to June 17, 2014 can be primarily attributed to variations in snow depth, <span class="hlt">ice</span> thickness, and bottom <span class="hlt">ice</span> algae concentrations. This study characterizes the interactions among these dominant variables using observed optical properties at each sampling site. We employ a normalized difference index to compute estimates of Chlorophyll a concentrations and analyze the increased attenuation of incident irradiance due to absorption by biomass. On a kilometer spatial scale, the presence of bottom <span class="hlt">ice</span> algae reduced the maximum transmitted irradiance by about 1.5 orders of magnitude when comparing floes of similar snow and <span class="hlt">ice</span> thicknesses. On a meter spatial scale, the combined effects of disparities in the depth and distribution of the overlying snow <span class="hlt">cover</span> along with algae concentrations caused maximum transmittances to vary between 0.0577 and 0.282 at a single site. Temporal variability was also observed as the average integrated transmitted photosynthetically active radiation increased by one order of magnitude to 3.4% for the last eight measurement days compared to the first nine. Results provide insight on how interrelated physical and ecological parameters of sea <span class="hlt">ice</span> in varying time and space may impact new trends in Arctic sea <span class="hlt">ice</span> extent and the progression of melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413439B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413439B"><span>Changes in the seasonality of Arctic sea <span class="hlt">ice</span> and temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bintanja, R.</p> <p>2012-04-01</p> <p>Observations show that the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is currently declining as a result of climate warming. According to climate models, this retreat will continue and possibly accelerate in the near-future. However, the magnitude of this decline is not the same throughout the year. With temperatures near or above the freezing point, summertime Arctic sea <span class="hlt">ice</span> will quickly diminish. However, at temperatures well below freezing, the sea <span class="hlt">ice</span> <span class="hlt">cover</span> during winter will exhibit a much weaker decline. In the future, the sea <span class="hlt">ice</span> seasonal cycle will be no <span class="hlt">ice</span> in summer, and thin one-year <span class="hlt">ice</span> in winter. Hence, the seasonal cycle in sea <span class="hlt">ice</span> <span class="hlt">cover</span> will increase with ongoing climate warming. This in itself leads to an increased summer-winter contrast in surface air temperature, because changes in sea <span class="hlt">ice</span> have a dominant influence on Arctic temperature and its seasonality. Currently, the annual amplitude in air temperature is decreasing, however, because winters warm faster than summer. With ongoing summer sea <span class="hlt">ice</span> reductions there will come a time when the annual temperature amplitude will increase again because of the large seasonal changes in sea <span class="hlt">ice</span>. This suggests that changes in the seasonal cycle in Arctic sea <span class="hlt">ice</span> and temperature are closely, and intricately, connected. Future changes in Arctic seasonality (will) have an profound effect on flora, fauna, humans and economic activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29957836','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29957836"><span>Reproductive performance and diving behaviour share a common sea-<span class="hlt">ice</span> concentration optimum in Adélie penguins (Pygoscelis adeliae).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Le Guen, Camille; Kato, Akiko; Raymond, Ben; Barbraud, Christophe; Beaulieu, Michaël; Bost, Charles-André; Delord, Karine; MacIntosh, Andrew J J; Meyer, Xavier; Raclot, Thierry; Sumner, Michael; Takahashi, Akinori; Thiebot, Jean-Baptiste; Ropert-Coudert, Yan</p> <p>2018-06-29</p> <p>The Southern Ocean is currently experiencing major environmental changes, including in sea-<span class="hlt">ice</span> <span class="hlt">cover</span>. Such changes strongly influence ecosystem structure and functioning and affect the survival and reproduction of predators such as seabirds. These effects are likely mediated by reduced availability of food resources. As such, seabirds are reliable eco-indicators of environmental conditions in the Antarctic region. Here, <span class="hlt">based</span> on nine years of sea-<span class="hlt">ice</span> data, we found that the breeding success of Adélie penguins (Pygoscelis adeliae) reaches a peak at intermediate sea-<span class="hlt">ice</span> <span class="hlt">cover</span> (ca. 20%). We further examined the effects of sea-<span class="hlt">ice</span> conditions on the foraging activity of penguins, measured at multiple scales from individual dives to foraging trips. Analysis of temporal organisation of dives, including fractal and bout analyses, revealed an increasingly consistent behaviour during years with extensive sea-<span class="hlt">ice</span> <span class="hlt">cover</span>. The relationship between several dive parameters and sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in the foraging area appears to be quadratic. In years of low and high sea-<span class="hlt">ice</span> <span class="hlt">cover</span>, individuals adjusted their diving effort by generally diving deeper, more frequently and by resting at the surface between dives for shorter periods of time than in years with intermediate sea-<span class="hlt">ice</span> <span class="hlt">cover</span>. Our study therefore suggests that sea-<span class="hlt">ice</span> <span class="hlt">cover</span> is likely to affect the reproductive performance of Adélie penguins through its effects on foraging behaviour, as breeding success and most diving parameters share a common optimum. Some years, however, deviated from this general trend, suggesting that other factors (e.g. precipitation during the breeding season) might sometimes become preponderant over the sea-<span class="hlt">ice</span> effects on breeding and foraging performance. Our study highlights the value of monitoring fitness parameters and individual behaviour concomitantly over the long term to better characterize optimal environmental conditions and potential resilience of wildlife. Such an approach is crucial if we want</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C41C0478A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C41C0478A"><span>Controls on Arctic sea <span class="hlt">ice</span> from first-year and multi-year <span class="hlt">ice</span> survival rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Armour, K.; Bitz, C. M.; Hunke, E. C.; Thompson, L.</p> <p>2009-12-01</p> <p>The recent decrease in Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has transpired with a significant loss of multi-year (MY) <span class="hlt">ice</span>. The transition to an Arctic that is populated by thinner first-year (FY) sea <span class="hlt">ice</span> has important implications for future trends in area and volume. We develop a reduced model for Arctic sea <span class="hlt">ice</span> with which we investigate how the survivability of FY and MY <span class="hlt">ice</span> control various aspects of the sea-<span class="hlt">ice</span> system. We demonstrate that Arctic sea-<span class="hlt">ice</span> area and volume behave approximately as first-order autoregressive processes, which allows for a simple interpretation of September sea-<span class="hlt">ice</span> in which its mean state, variability, and sensitivity to climate forcing can be described naturally in terms of the average survival rates of FY and MY <span class="hlt">ice</span>. This model, used in concert with a sea-<span class="hlt">ice</span> simulation that traces FY and MY <span class="hlt">ice</span> areas to estimate the survival rates, reveals that small trends in the <span class="hlt">ice</span> survival rates explain the decline in total Arctic <span class="hlt">ice</span> area, and the relatively larger loss of MY <span class="hlt">ice</span> area, over the period 1979-2006. Additionally, our model allows for a calculation of the persistence time scales of September area and volume anomalies. A relatively short memory time scale for <span class="hlt">ice</span> area (~ 1 year) implies that Arctic <span class="hlt">ice</span> area is nearly in equilibrium with long-term climate forcing at all times, and therefore observed trends in area are a clear indication of a changing climate. A longer memory time scale for <span class="hlt">ice</span> volume (~ 5 years) suggests that volume can be out of equilibrium with climate forcing for long periods of time, and therefore trends in <span class="hlt">ice</span> volume are difficult to distinguish from its natural variability. With our reduced model, we demonstrate the connection between memory time scale and sensitivity to climate forcing, and discuss the implications that a changing memory time scale has on the trajectory of <span class="hlt">ice</span> area and volume in a warming climate. Our findings indicate that it is unlikely that a “tipping point” in September <span class="hlt">ice</span> area and volume will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......145P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......145P"><span>Implications of a reduced Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> on the large-scale atmospheric energy and moisture budgets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Porter, David Felton</p> <p></p> <p> vertically deep heating and moistening of the Arctic atmosphere. Significant warming and moistening persists through November. This warmer and moister atmosphere is associated with an increase in cloud <span class="hlt">cover</span>, affecting the surface and atmospheric energy budget. There is an enhancement of the hydrologic cycle, with increased evaporation in areas of sea <span class="hlt">ice</span> loss paired with increased precipitation. Summertime changes in the hydrologic cycle reflect circulation responses to mid-latitude SSTs, highlighting the general sensitivity of the Arctic climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917155B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917155B"><span>Sea <span class="hlt">ice</span> type dynamics in the Arctic <span class="hlt">based</span> on Sentinel-1 Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Babiker, Mohamed; Korosov, Anton; Park, Jeong-Won</p> <p>2017-04-01</p> <p>Sea <span class="hlt">ice</span> observation from satellites has been carried out for more than four decades and is one of the most important applications of EO data in operational monitoring as well as in climate change studies. Several sensors and retrieval methods have been developed and successfully utilized to measure sea <span class="hlt">ice</span> area, concentration, drift, type, thickness, etc [e.g. Breivik et al., 2009]. Today operational sea <span class="hlt">ice</span> monitoring and analysis is fully dependent on use of satellite data. However, new and improved satellite systems, such as multi-polarisation Synthetic Apperture Radar (SAR), require further studies to develop more advanced and automated sea <span class="hlt">ice</span> monitoring methods. In addition, the unprecedented volume of data available from recently launched Sentinel missions provides both challenges and opportunities for studying sea <span class="hlt">ice</span> dynamics. In this study we investigate sea <span class="hlt">ice</span> type dynamics in the Fram strait <span class="hlt">based</span> on Sentinel-1 A, B SAR data. Series of images for the winter season are classified into 4 <span class="hlt">ice</span> types (young <span class="hlt">ice</span>, first year <span class="hlt">ice</span>, multiyear <span class="hlt">ice</span> and leads) using the new algorithm developed by us for sea <span class="hlt">ice</span> classification, which is <span class="hlt">based</span> on segmentation, GLCM calculation, Haralick texture feature extraction, unsupervised and supervised classifications and Support Vector Machine (SVM) [Zakhvatkina et al., 2016; Korosov et al., 2016]. This algorithm is further improved by applying thermal and scalloping noise removal [Park et al. 2016]. Sea <span class="hlt">ice</span> drift is retrieved from the same series of Sentinel-1 images using the newly developed algorithm <span class="hlt">based</span> on combination of feature tracking and pattern matching [Mukenhuber et al., 2016]. Time series of these two products (sea <span class="hlt">ice</span> type and sea <span class="hlt">ice</span> drift) are combined in order to study sea <span class="hlt">ice</span> deformation processes at small scales. Zones of sea <span class="hlt">ice</span> convergence and divergence identified from sea <span class="hlt">ice</span> drift are compared with ridges and leads identified from texture features. That allows more specific interpretation of SAR</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016789','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016789"><span>Simulation of lake <span class="hlt">ice</span> and its effect on the late-Pleistocene evaporation rate of Lake Lahontan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hostetler, S.W.</p> <p>1991-01-01</p> <p>A model of lake <span class="hlt">ice</span> was coupled with a model of lake temperature and evaporation to assess the possible effect of <span class="hlt">ice</span> <span class="hlt">cover</span> on the late-Pleistocene evaporation rate of Lake Lahontan. The simulations were done using a data set <span class="hlt">based</span> on proxy temperature indicators and features of the simulated late-Pleistocene atmospheric circulation over western North America. When a data set <span class="hlt">based</span> on a mean-annual air temperature of 3?? C (7?? C colder than present) and reduced solar radiation from jet-stream induced cloud <span class="hlt">cover</span> was used as input to the model, <span class="hlt">ice</span> <span class="hlt">cover</span> lasting ??? 4 months was simulated. Simulated evaporation rates (490-527 mm a-1) were ??? 60% lower than the present-day evaporation rate (1300 mm a-1) of Pyramid Lake. With this reduced rate of evaporation, water inputs similar to the 1983 historical maxima that occurred in the Lahontan basin would have been sufficient to maintain the 13.5 ka BP high stand of Lake Lahontan. ?? 1991 Springer-Verlag.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51A0955L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51A0955L"><span>Sea <span class="hlt">ice</span> roughness: the key for predicting Arctic summer <span class="hlt">ice</span> albedo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Landy, J.; Ehn, J. K.; Tsamados, M.; Stroeve, J.; Barber, D. G.</p> <p>2017-12-01</p> <p>Although melt ponds on Arctic sea <span class="hlt">ice</span> evolve in stages, <span class="hlt">ice</span> with smoother surface topography typically allows the pond water to spread over a wider area, reducing the <span class="hlt">ice</span>-albedo and accelerating further melt. Building on this theory, we simulated the distribution of meltwater on a range of statistically-derived topographies to develop a quantitative relationship between premelt sea <span class="hlt">ice</span> surface roughness and summer <span class="hlt">ice</span> albedo. Our method, previously applied to ICESat observations of the end-of-winter sea <span class="hlt">ice</span> roughness, could account for 85% of the variance in AVHRR observations of the summer <span class="hlt">ice</span>-albedo [Landy et al., 2015]. Consequently, an Arctic-wide reduction in sea <span class="hlt">ice</span> roughness over the ICESat operational period (from 2003 to 2008) explained a drop in <span class="hlt">ice</span>-albedo that resulted in a 16% increase in solar heat input to the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Here we will review this work and present new research linking pre-melt sea <span class="hlt">ice</span> surface roughness observations from Cryosat-2 to summer sea <span class="hlt">ice</span> albedo over the past six years, examining the potential of winter roughness as a significant new source of sea <span class="hlt">ice</span> predictability. We will further evaluate the possibility for high-resolution (kilometre-scale) forecasts of summer sea <span class="hlt">ice</span> albedo from waveform-level Cryosat-2 roughness data in the landfast sea <span class="hlt">ice</span> zone of the Canadian Arctic. Landy, J. C., J. K. Ehn, and D. G. Barber (2015), Albedo feedback enhanced by smoother Arctic sea <span class="hlt">ice</span>, Geophys. Res. Lett., 42, 10,714-10,720, doi:10.1002/2015GL066712.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC53E0944A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC53E0944A"><span>Record low lake <span class="hlt">ice</span> thickness and bedfast <span class="hlt">ice</span> extent on Alaska's Arctic Coastal Plain in 2017 exemplify the value of monitoring freshwater <span class="hlt">ice</span> to understand sea-<span class="hlt">ice</span> forcing and predict permafrost dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arp, C. D.; Alexeev, V. A.; Bondurant, A. C.; Creighton, A.; Engram, M. J.; Jones, B. M.; Parsekian, A.</p> <p>2017-12-01</p> <p>The winter of 2016/2017 was exceptionally warm and snowy along the coast of Arctic Alaska partly due to low fall sea <span class="hlt">ice</span> extent. <span class="hlt">Based</span> on several decades of field measurements, we documented a new record low maximum <span class="hlt">ice</span> thickness (MIT) for lakes on the Barrow Peninsula, averaging 1.2 m. This is in comparison to a long-term average MIT of 1.7 m stretching back to 1962 with a maximum of 2.1 m in 1970 and previous minimum of 1.3 m in 2014. The relevance of thinner lake <span class="hlt">ice</span> in arctic coastal lowlands, where thermokarst lakes <span class="hlt">cover</span> greater than 20% of the land area, is that permafrost below lakes with bedfast <span class="hlt">ice</span> is typically preserved. Lakes deeper than the MIT warm and thaw sub-lake permafrost forming taliks. Remote sensing analysis using synthetic aperture radar (SAR) is a valuable tool for scaling the field observations of MIT to the entire freshwater landscape to map bedfast <span class="hlt">ice</span>. A new, long-term time-series of late winter multi-platform SAR from 1992 to 2016 shows a large dynamic range of bedfast <span class="hlt">ice</span> extent, 29% of lake area or 6% of the total land area over this period, and adding 2017 to this record is expected to extend this range further. Empirical models of lake mean annual bed temperature suggest that permafrost begins to thaw at depths less than 60% of MIT. <span class="hlt">Based</span> on this information and knowledge of average lake <span class="hlt">ice</span> growth trajectories, we suggest that future SAR analysis of lake <span class="hlt">ice</span> should focus on mid-winter (January) to evaluate the extent of bedfast <span class="hlt">ice</span> and corresponding zones of sub-lake permafrost thaw. Tracking changes in these areas from year to year in mid-winter may provide the best landscape-scale evaluation of changing permafrost conditions in lake-rich arctic lowlands. Because observed changes in MIT coupled with mid-winter bedfast <span class="hlt">ice</span> extent provide much information on permafrost stability, we suggest that these measurements can serve as Essential Climate Variables (EVCs) to indicate past and future changes in lake-rich arctic regions. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAn.IV2..311X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAn.IV2..311X"><span>Lake <span class="hlt">Ice</span> Monitoring with Webcams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, M.; Rothermel, M.; Tom, M.; Galliani, S.; Baltsavias, E.; Schindler, K.</p> <p>2018-05-01</p> <p>Continuous monitoring of climate indicators is important for understanding the dynamics and trends of the climate system. Lake <span class="hlt">ice</span> has been identified as one such indicator, and has been included in the list of Essential Climate Variables (ECVs). Currently there are two main ways to survey lake <span class="hlt">ice</span> <span class="hlt">cover</span> and its change over time, in-situ measurements and satellite remote sensing. The challenge with both of them is to ensure sufficient spatial and temporal resolution. Here, we investigate the possibility to monitor lake <span class="hlt">ice</span> with video streams acquired by publicly available webcams. Main advantages of webcams are their high temporal frequency and dense spatial sampling. By contrast, they have low spectral resolution and limited image quality. Moreover, the uncontrolled radiometry and low, oblique viewpoints result in heavily varying appearance of water, <span class="hlt">ice</span> and snow. We present a workflow for pixel-wise semantic segmentation of images into these classes, <span class="hlt">based</span> on state-of-the-art encoder-decoder Convolutional Neural Networks (CNNs). The proposed segmentation pipeline is evaluated on two sequences featuring different ground sampling distances. The experiment suggests that (networks of) webcams have great potential for lake <span class="hlt">ice</span> monitoring. The overall per-pixel accuracies for both tested data sets exceed 95 %. Furthermore, per-image discrimination between <span class="hlt">ice</span>-on and <span class="hlt">ice</span>-off conditions, derived by accumulating per-pixel results, is 100 % correct for our test data, making it possible to precisely recover freezing and thawing dates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010037608','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010037608"><span>Trends in the Length of the Southern Ocean Sea <span class="hlt">Ice</span> Season: 1979-1999</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Satellite data can be used to observe the sea <span class="hlt">ice</span> distribution around the continent of Antarctica on a daily basis and hence to determine how many days a year have sea <span class="hlt">ice</span> at each location. This has been done for each of the 21 years 1979-1999. Mapping the trends in these data over the 21-year period reveals a detailed pattern of changes in the length of the sea <span class="hlt">ice</span> season around Antarctica. Most of the Ross Sea <span class="hlt">ice</span> <span class="hlt">cover</span> has undergone a lengthening of the sea <span class="hlt">ice</span> season, whereas most of the Amundsen Sea <span class="hlt">ice</span> <span class="hlt">cover</span> and almost the entire Bellingshausen Sea <span class="hlt">ice</span> <span class="hlt">cover</span> have undergone a shortening of the sea <span class="hlt">ice</span> season. Results around the rest of the continent, including in the Weddell Sea, are more mixed, but overall, more of the Southern Ocean experienced a lengthening of the sea <span class="hlt">ice</span> season than a shortening. For instance, the area experiencing a lengthening of the sea <span class="hlt">ice</span> season by at least 1 day per year is 5.8 x 10(exp 6) sq km, whereas the area experiencing a shortening of the sea <span class="hlt">ice</span> season by at least 1 day per year is less than half that, at 2.8 x 10(exp 6) sq km. This contrasts sharply with what is happened over the same period in the Arctic, where, overall, there has been some depletion of the <span class="hlt">ice</span> <span class="hlt">cover</span>, including shortened sea <span class="hlt">ice</span> seasons and decreased <span class="hlt">ice</span> extents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2173G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2173G"><span>Estimates of ikaite export from sea <span class="hlt">ice</span> to the underlying seawater in a sea <span class="hlt">ice</span>-seawater mesocosm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Geilfus, Nicolas-Xavier; Galley, Ryan J.; Else, Brent G. T.; Campbell, Karley; Papakyriakou, Tim; Crabeck, Odile; Lemes, Marcos; Delille, Bruno; Rysgaard, Søren</p> <p>2016-09-01</p> <p>The precipitation of ikaite and its fate within sea <span class="hlt">ice</span> is still poorly understood. We quantify temporal inorganic carbon dynamics in sea <span class="hlt">ice</span> from initial formation to its melt in a sea <span class="hlt">ice</span>-seawater mesocosm pool from 11 to 29 January 2013. <span class="hlt">Based</span> on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea <span class="hlt">ice</span> were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea <span class="hlt">ice</span> acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmol kg-1 within sea <span class="hlt">ice</span> was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64-66 µmol kg-1 in the water column. The export of TCO2 from sea <span class="hlt">ice</span> to the water column increased the underlying seawater TCO2 by 43.5 µmol kg-1, suggesting that almost all of the TCO2 that left the sea <span class="hlt">ice</span> was exported to the underlying seawater. The export of ikaite from the <span class="hlt">ice</span> to the underlying seawater was associated with brine rejection during sea <span class="hlt">ice</span> growth, increased vertical connectivity in sea <span class="hlt">ice</span> due to the upward percolation of seawater and meltwater flushing during sea <span class="hlt">ice</span> melt. <span class="hlt">Based</span> on the change in TA in the water column around the onset of sea <span class="hlt">ice</span> melt, more than half of the total ikaite precipitated in the <span class="hlt">ice</span> during sea <span class="hlt">ice</span> growth was still contained in the <span class="hlt">ice</span> when the sea <span class="hlt">ice</span> began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea <span class="hlt">ice</span> growth. Results indicate that ikaite export from sea <span class="hlt">ice</span> and its dissolution in the underlying seawater can potentially hamper</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........69M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........69M"><span>Arctic Sea <span class="hlt">Ice</span>: Trends, Stability and Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moon, Woosok</p> <p></p> <p>A stochastic Arctic sea-<span class="hlt">ice</span> model is derived and analyzed in detail to interpret the recent decay and associated variability of Arctic sea-<span class="hlt">ice</span> under changes in greenhouse gas forcing widely referred to as global warming. The approach begins from a deterministic model of the heat flux balance through the air/sea/<span class="hlt">ice</span> system, which uses observed monthly-averaged heat fluxes to drive a time evolution of sea-<span class="hlt">ice</span> thickness. This model reproduces the observed seasonal cycle of the <span class="hlt">ice</span> <span class="hlt">cover</span> and it is to this that stochastic noise---representing high frequency variability---is introduced. The model takes the form of a single periodic non-autonomous stochastic ordinary differential equation. Following an introductory chapter, the two that follow focus principally on the properties of the deterministic model in order to identify the main properties governing the stability of the <span class="hlt">ice</span> <span class="hlt">cover</span>. In chapter 2 the underlying time-dependent solutions to the deterministic model are analyzed for their stability. It is found that the response time-scale of the system to perturbations is dominated by the destabilizing sea-<span class="hlt">ice</span> albedo feedback, which is operative in the summer, and the stabilizing long wave radiative cooling of the <span class="hlt">ice</span> surface, which is operative in the winter. This basic competition is found throughout the thesis to define the governing dynamics of the system. In particular, as greenhouse gas forcing increases, the sea-<span class="hlt">ice</span> albedo feedback becomes more effective at destabilizing the system. Thus, any projections of the future state of Arctic sea-<span class="hlt">ice</span> will depend sensitively on the treatment of the <span class="hlt">ice</span>-albedo feedback. This in turn implies that the treatment a fractional <span class="hlt">ice</span> <span class="hlt">cover</span> as the <span class="hlt">ice</span> areal extent changes rapidly, must be handled with the utmost care. In chapter 3, the idea of a two-season model, with just winter and summer, is revisited. By breaking the seasonal cycle up in this manner one can simplify the interpretation of the basic dynamics. Whereas in the fully</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRC..119.4141K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRC..119.4141K"><span>Snow depth of the Weddell and Bellingshausen sea <span class="hlt">ice</span> <span class="hlt">covers</span> from <span class="hlt">Ice</span>Bridge surveys in 2010 and 2011: An examination</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kwok, R.; Maksym, T.</p> <p>2014-07-01</p> <p>We examine the snow radar data from the Weddell and Bellingshausen Seas acquired by eight <span class="hlt">Ice</span>Bridge (OIB) flightlines in October of 2010 and 2011. In snow depth retrieval, the sidelobes from the stronger scattering snow-<span class="hlt">ice</span> (s-i) interfaces could be misidentified as returns from the weaker air-snow (a-s) interfaces. In this paper, we first introduce a retrieval procedure that accounts for the structure of the radar system impulse response followed by a survey of the snow depths in the Weddell and Bellingshausen Seas. Limitations and potential biases in our approach are discussed. Differences between snow depth estimates from a repeat survey of one Weddell Sea track separated by 12 days, without accounting for variability due to <span class="hlt">ice</span> motion, is -0.7 ± 13.6 cm. Average snow depth is thicker in coastal northwestern Weddell and thins toward Cape Norvegia, a decrease of >30 cm. In the Bellingshausen, the thickest snow is found nearshore in both Octobers and is thickest next to the Abbot <span class="hlt">Ice</span> Shelf. Snow depth is linearly related to freeboard when freeboards are low but diverge as the freeboard increases especially in the thicker/rougher <span class="hlt">ice</span> of the western Weddell. We find correlations of 0.71-0.84 between snow depth and surface roughness suggesting preferential accumulation over deformed <span class="hlt">ice</span>. Retrievals also seem to be related to radar backscatter through surface roughness. Snow depths reported here, generally higher than those from in situ records, suggest dissimilarities in sample populations. Implications of these differences on Antarctic sea <span class="hlt">ice</span> thickness are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070018931','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070018931"><span>Waterway <span class="hlt">Ice</span> Thickness Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1978-01-01</p> <p>The ship on the opposite page is a U. S. Steel Corporation tanker cruising through the <span class="hlt">ice-covered</span> waters of the Great Lakes in the dead of winter. The ship's crew is able to navigate safely by plotting courses through open water or thin <span class="hlt">ice</span>, a technique made possible by a multi-agency technology demonstration program in which NASA is a leading participant. Traditionally, the Great Lakes-St. Lawrence Seaway System is closed to shipping for more than three months of winter season because of <span class="hlt">ice</span> blockage, particularly fluctuations in the thickness and location of <span class="hlt">ice</span> <span class="hlt">cover</span> due to storms, wind, currents and variable temperatures. Shippers have long sought a system of navigation that would allow year-round operation on the Lakes and produce enormous economic and fuel conservation benefits. Interrupted operations require that industrial firms stockpile materials to carry them through the impassable months, which is costly. Alternatively, they must haul cargos by more expensive overland transportation. Studies estimate the economic benefits of year-round Great Lakes shipping in the hundreds of millions of dollars annually and fuel consumption savings in the tens of millions of gallons. Under Project Icewarn, NASA, the U.S. Coast Guard and the National Oceanic Atmospheric Administration collaborated in development and demonstration of a system that permits safe year-round operations. It employs airborne radars, satellite communications relay and facsimile transmission to provide shippers and ships' masters up-to-date <span class="hlt">ice</span> charts. Lewis Research Center contributed an accurate methods of measuring <span class="hlt">ice</span> thickness by means of a special "short-pulse" type of radar. In a three-year demonstration program, Coast Guard aircraft equipped with Side-Looking Airborne Radar (SLAR) flew over the Great Lakes three or four times a week. The SLAR, which can penetrate clouds, provided large area readings of the type and distribution of <span class="hlt">ice</span> <span class="hlt">cover</span>. The information was supplemented by short</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAr42.3.2625L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAr42.3.2625L"><span>Compiling Techniques for East Antarctic <span class="hlt">Ice</span> Velocity Mapping <span class="hlt">Based</span> on Historical Optical Imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, X.; Li, R.; Qiao, G.; Cheng, Y.; Ye, W.; Gao, T.; Huang, Y.; Tian, Y.; Tong, X.</p> <p>2018-05-01</p> <p><span class="hlt">Ice</span> flow velocity over long time series in East Antarctica plays a vital role in estimating and predicting the mass balance of Antarctic <span class="hlt">Ice</span> Sheet and its contribution to global sea level rise. However, there is no Antarctic <span class="hlt">ice</span> velocity product with large space scale available showing the East Antarctic <span class="hlt">ice</span> flow velocity pattern before the 1990s. We proposed three methods including parallax decomposition, grid-<span class="hlt">based</span> NCC image matching, feature and gird-<span class="hlt">based</span> image matching with constraints for estimation of surface velocity in East Antarctica <span class="hlt">based</span> on ARGON KH-5 and LANDSAT imagery, showing the feasibility of using historical optical imagery to obtain Antarctic <span class="hlt">ice</span> motion. <span class="hlt">Based</span> on these previous studies, we presented a set of systematic method for developing <span class="hlt">ice</span> surface velocity product for the entire East Antarctica from the 1960s to the 1980s in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27264318','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27264318"><span>Bacterial communities in Arctic first-year drift <span class="hlt">ice</span> during the winter/spring transition.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Eronen-Rasimus, Eeva; Piiparinen, Jonna; Karkman, Antti; Lyra, Christina; Gerland, Sebastian; Kaartokallio, Hermanni</p> <p>2016-08-01</p> <p>Horizontal and vertical variability of first-year drift-<span class="hlt">ice</span> bacterial communities was investigated along a North-South transect in the Fram Strait during the winter/spring transition. Two different developmental stages were captured along the transect <span class="hlt">based</span> on the prevailing environmental conditions and the differences in bacterial community composition. The differences in the bacterial communities were likely driven by the changes in sea-<span class="hlt">ice</span> algal biomass (2.6-5.6 fold differences in chl-a concentrations). Copiotrophic genera common in late spring/summer sea <span class="hlt">ice</span>, such as Polaribacter, Octadecabacter and Glaciecola, dominated the bacterial communities, supporting the conclusion that the increase in the sea-<span class="hlt">ice</span> algal biomass was possibly reflected in the sea-<span class="hlt">ice</span> bacterial communities. Of the dominating bacterial genera, Polaribacter seemed to benefit the most from the increase in algal biomass, since they <span class="hlt">covered</span> approximately 39% of the total community at the southernmost stations with higher (>6 μg l(-1) ) chl-a concentrations and only 9% at the northernmost station with lower chl-a concentrations (<6 μg l(-1) ). The sea-<span class="hlt">ice</span> bacterial communities also varied between the <span class="hlt">ice</span> horizons at all three stations and thus we recommend that for future studies multiple <span class="hlt">ice</span> horizons be sampled to <span class="hlt">cover</span> the variability in sea-<span class="hlt">ice</span> bacterial communities in spring. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010100393','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010100393"><span>Variability of Antarctic Sea <span class="hlt">Ice</span> 1979-1998</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Comiso, Josefino C.; Parkinson, Claire L.; Cavalieri, Donald J.; Gloersen, Per; Koblinsky, Chester J. (Technical Monitor)</p> <p>2001-01-01</p> <p>The principal characteristics of the variability of Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> as previously described from satellite passive-microwave observations are also evident in a systematically-calibrated and analyzed data set for 20.2 years (1979-1998). The total Antarctic sea <span class="hlt">ice</span> extent (concentration > 15 %) increased by 13,440 +/- 4180 sq km/year (+1.18 +/- 0.37%/decade). The area of sea <span class="hlt">ice</span> within the extent boundary increased by 16,960 +/- 3,840 sq km/year (+1.96 +/- 0.44%/decade). Regionally, the trends in extent are positive in the Weddell Sea (1.5 +/- 0.9%/decade), Pacific Ocean (2.4 +/- 1.4%/decade), and Ross (6.9 +/- 1.1 %/decade) sectors, slightly negative in the Indian Ocean (-1.5 +/- 1.8%/decade, and strongly negative in the Bellingshausen-Amundsen Seas sector (-9.5 +/- 1.5%/decade). For the entire <span class="hlt">ice</span> pack, small <span class="hlt">ice</span> increases occur in all seasons with the largest increase during autumn. On a regional basis, the trends differ season to season. During summer and fall, the trends are positive or near zero in all sectors except the Bellingshausen-Amundsen Seas sector. During winter and spring, the trends are negative or near zero in all sectors except the Ross Sea, which has positive trends in all seasons. Components of interannual variability with periods of about 3 to 5 years are regionally large, but tend to counterbalance each other in the total <span class="hlt">ice</span> pack. The interannual variability of the annual mean sea-<span class="hlt">ice</span> extent is only 1.6% overall, compared to 5% to 9% in each of five regional sectors. Analysis of the relation between regional sea <span class="hlt">ice</span> extents and spatially-averaged surface temperatures over the <span class="hlt">ice</span> pack gives an overall sensitivity between winter <span class="hlt">ice</span> <span class="hlt">cover</span> and temperature of -0.7% change in sea <span class="hlt">ice</span> extent per K. For summer, some regional <span class="hlt">ice</span> extents vary positively with temperature and others negatively. The observed increase in Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> is counter to the observed decreases in the Arctic. It is also qualitatively consistent with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28025300','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28025300"><span>Linking scales in sea <span class="hlt">ice</span> mechanics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weiss, Jérôme; Dansereau, Véronique</p> <p>2017-02-13</p> <p>Mechanics plays a key role in the evolution of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> through its control on drift, on momentum and thermal energy exchanges between the polar oceans and the atmosphere along cracks and faults, and on <span class="hlt">ice</span> thickness distribution through opening and ridging processes. At the local scale, a significant variability of the mechanical strength is associated with the microstructural heterogeneity of saline <span class="hlt">ice</span>, however characterized by a small correlation length, below the <span class="hlt">ice</span> thickness scale. Conversely, the sea <span class="hlt">ice</span> mechanical fields (velocity, strain and stress) are characterized by long-ranged (more than 1000 km) and long-lasting (approx. few months) correlations. The associated space and time scaling laws are the signature of the brittle character of sea <span class="hlt">ice</span> mechanics, with deformation resulting from a multi-scale accumulation of episodic fracturing and faulting events. To translate the short-range-correlated disorder on strength into long-range-correlated mechanical fields, several key ingredients are identified: long-ranged elastic interactions, slow driving conditions, a slow viscous-like relaxation of elastic stresses and a restoring/healing mechanism. These ingredients constrained the development of a new continuum mechanics modelling framework for the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, called Maxwell-elasto-brittle. Idealized simulations without advection demonstrate that this rheological framework reproduces the main characteristics of sea <span class="hlt">ice</span> mechanics, including anisotropy, spatial localization and intermittency, as well as the associated scaling laws.This article is part of the themed issue 'Microdynamics of <span class="hlt">ice</span>'. © 2016 The Author(s).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RSPTA.37550352W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37550352W"><span>Linking scales in sea <span class="hlt">ice</span> mechanics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiss, Jérôme; Dansereau, Véronique</p> <p>2017-02-01</p> <p>Mechanics plays a key role in the evolution of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> through its control on drift, on momentum and thermal energy exchanges between the polar oceans and the atmosphere along cracks and faults, and on <span class="hlt">ice</span> thickness distribution through opening and ridging processes. At the local scale, a significant variability of the mechanical strength is associated with the microstructural heterogeneity of saline <span class="hlt">ice</span>, however characterized by a small correlation length, below the <span class="hlt">ice</span> thickness scale. Conversely, the sea <span class="hlt">ice</span> mechanical fields (velocity, strain and stress) are characterized by long-ranged (more than 1000 km) and long-lasting (approx. few months) correlations. The associated space and time scaling laws are the signature of the brittle character of sea <span class="hlt">ice</span> mechanics, with deformation resulting from a multi-scale accumulation of episodic fracturing and faulting events. To translate the short-range-correlated disorder on strength into long-range-correlated mechanical fields, several key ingredients are identified: long-ranged elastic interactions, slow driving conditions, a slow viscous-like relaxation of elastic stresses and a restoring/healing mechanism. These ingredients constrained the development of a new continuum mechanics modelling framework for the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, called Maxwell-elasto-brittle. Idealized simulations without advection demonstrate that this rheological framework reproduces the main characteristics of sea <span class="hlt">ice</span> mechanics, including anisotropy, spatial localization and intermittency, as well as the associated scaling laws. This article is part of the themed issue 'Microdynamics of <span class="hlt">ice</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120000908','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120000908"><span>Comparison of In-Situ, Model and Ground <span class="hlt">Based</span> In-Flight <span class="hlt">Icing</span> Severity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnston, Christopher J.; Serke, David J.; Adriaansen, Daniel R.; Reehorst, Andrew L.; Politovich, Marica K.; Wolff, Cory A.; McDonough, Frank</p> <p>2011-01-01</p> <p>As an aircraft flies through supercooled liquid water, the liquid freezes instantaneously to the airframe thus altering its lift, drag, and weight characteristics. In-flight <span class="hlt">icing</span> is a contributing factor to many aviation accidents, and the reliable detection of this hazard is a fundamental concern to aviation safety. The scientific community has recently developed products to provide in-flight <span class="hlt">icing</span> warnings. NASA's <span class="hlt">Icing</span> Remote Sensing System (NIRSS) deploys a vertically--pointing Ka--band radar, a laser ceilometer, and a profiling multi-channel microwave radiometer for the diagnosis of terminal area in-flight <span class="hlt">icing</span> hazards with high spatial and temporal resolution. NCAR s Current <span class="hlt">Icing</span> Product (CIP) combines several meteorological inputs to produce a gridded, three-dimensional depiction of <span class="hlt">icing</span> severity on an hourly basis. Pilot reports are the best and only source of information on in-situ <span class="hlt">icing</span> conditions encountered by an aircraft. The goal of this analysis was to ascertain how the testbed NIRSS <span class="hlt">icing</span> severity product and the operational CIP severity product compare to pilot reports of <span class="hlt">icing</span> severity, and how NIRSS and CIP compare to each other. This study revealed that the <span class="hlt">icing</span> severity product from the ground-<span class="hlt">based</span> NASA testbed system compared very favorably with the operational model-<span class="hlt">based</span> product and pilot reported in-situ <span class="hlt">icing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33B1199B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33B1199B"><span>Broadband acoustic wave propagation across sloping topography <span class="hlt">covered</span> by sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Badiey, M.; Wan, L.; Eickmeier, J.; Muenchow, A.; Ryan, P. A.</p> <p>2017-12-01</p> <p>The Canada Basin Acoustic Propagation Experiment (CANAPE) quantifies how sound generated in the deep Basin is received on the continental shelf. The two regimes, deep basin and shallow shelves, are separated by a 30-km wide region where the bottom changes from 1000-m to 100-m. This narrow region focuses and traps kinetic energy that surface wind forcing inputs into the ocean over a wide region with periodicities of days to months. As a result, ocean temperature and speed of sound are more variable near sloping topography than they are over either deep basins or shallow shelves. In contrast to companion CANAPE presentations in this session, here we use sound speed as input to predict likely propagation paths and transmission losses across the continental slope with a two-dimensional parabolic model (2D PE). Intensity fluctuations due to the changing bathymetry, water column oceanography, and the scattering from <span class="hlt">ice</span> <span class="hlt">cover</span> for broadband signals are checked against measured broadband acoustic signals that were collected simultaneously with the oceanographic measurements for a long period. Differences between measured and calculated transmission loss can be the result of out of plane acoustic paths requiring 3D PE modeling for future studies. [Work supported by ONR code 322 OA].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1213N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1213N"><span>On the Impact of Snow Salinity on CryoSat-2 First-Year Sea <span class="hlt">Ice</span> Thickness Retrievals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nandan, V.; Yackel, J.; Geldsetzer, T.; Mahmud, M.</p> <p>2017-12-01</p> <p>European Space Agency's Ku-band altimeter CryoSat-2 (CS-2) has demonstrated its potential to provide extensive basin-scale spatial and temporal measurements of Arctic sea <span class="hlt">ice</span> freeboard. It is assumed that CS-2 altimetric returns originate from the snow/sea <span class="hlt">ice</span> interface (assumed to be the main scattering horizon). However, in newly formed thin <span class="hlt">ice</span> ( 0.6 m) through to thick first-year sea <span class="hlt">ice</span> (FYI) ( 2 m), upward wicking of brine into the snow <span class="hlt">cover</span> from the underlying sea <span class="hlt">ice</span> surface produces saline snow layers, especially in the bottom 6-8 cm of a snow <span class="hlt">cover</span>. This in turn modifies the brine volume at/or near the snow/sea <span class="hlt">ice</span> interface, altering the dielectric and scattering properties of the snow <span class="hlt">cover</span>, leading to strong Ku-band microwave attenuation within the upper snow volume. Such significant reductions in Ku-band penetration may substantially affect CS-2 FYI freeboard retrievals. Therefore, the goal of this study is to evaluate a theoretical approach to estimate snow salinity induced uncertainty on CS-2 Arctic FYI freeboard measurements. Using the freeboard-to-thickness hydrostatic equilibrium equation, we quantify the error differences between the CS-2 FYI thickness, (assuming complete penetration of CS-2 radar signals to the snow/FYI interface), and the FYI thickness <span class="hlt">based</span> on the modeled Ku-band main scattering horizon for different snow <span class="hlt">cover</span> cases. We utilized naturally occurring saline and non-saline snow <span class="hlt">cover</span> cases ranging between 6 cm to 32 cm from the Canadian Arctic, observed during late-winter from 1993 to 2017, on newly-formed <span class="hlt">ice</span> ( 0.6 m), medium ( 1.5 m) and thick FYI ( 2 m). Our results suggest that irrespective of the thickness of the snow <span class="hlt">cover</span> overlaying FYI, the thickness of brine-wetted snow layers and actual FYI freeboard strongly influence the amount with which CS-2 FYI freeboard estimates and thus thickness calculations are overestimated. This effect is accentuated for increasingly thicker saline snow <span class="hlt">covers</span> overlaying newly-formed <span class="hlt">ice</span></p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMIN54A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMIN54A..08P"><span>Applying Agile Methods to the Development of a Community-<span class="hlt">Based</span> Sea <span class="hlt">Ice</span> Observations Database</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pulsifer, P. L.; Collins, J. A.; Kaufman, M.; Eicken, H.; Parsons, M. A.; Gearheard, S.</p> <p>2011-12-01</p> <p>Local and traditional knowledge and community-<span class="hlt">based</span> monitoring programs are increasingly being recognized as an important part of establishing an Arctic observing network, and understanding Arctic environmental change. The Seasonal <span class="hlt">Ice</span> Zone Observing Network (SIZONet, http://www.sizonet.org) project has implemented an integrated program for observing seasonal <span class="hlt">ice</span> in Alaska. Observation and analysis by local sea <span class="hlt">ice</span> experts helps track seasonal and inter-annual variability of the <span class="hlt">ice</span> <span class="hlt">cover</span> and its use by coastal communities. The ELOKA project (http://eloka-arctic.org) is collaborating with SIZONet on the development of a community accessible, Web-<span class="hlt">based</span> application for collecting and distributing local observations. The SIZONet project is dealing with complicated qualitative and quantitative data collected from a growing number of observers in different communities while concurrently working to design a system that will serve a wide range of different end users including Arctic residents, scientists, educators, and other stakeholders with a need for sea <span class="hlt">ice</span> information. The benefits of linking and integrating knowledge from communities and university-<span class="hlt">based</span> researchers are clear, however, development of an information system in this multidisciplinary, multi-participant context is challenging. Participants are geographically distributed, have different levels of technical expertise, and have varying goals for how the system will be used. As previously reported (Pulsifer et al. 2010), new technologies have been used to deal with some of the challenges presented in this complex development context. In this paper, we report on the challenges and innovations related to working as a multi-disciplinary software development team. Specifically, we discuss how Agile software development methods have been used in defining and refining user needs, developing prototypes, and releasing a production level application. We provide an overview of the production application that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMIN24A..02N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMIN24A..02N"><span><span class="hlt">Ice</span> Sheet Roughness Estimation <span class="hlt">Based</span> on Impulse Responses Acquired in the Global <span class="hlt">Ice</span> Sheet Mapping Orbiter Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niamsuwan, N.; Johnson, J. T.; Jezek, K. C.; Gogineni, P.</p> <p>2008-12-01</p> <p>The Global <span class="hlt">Ice</span> Sheet Mapping Orbiter (GISMO) mission was developed to address scientific needs to understand the polar <span class="hlt">ice</span> subsurface structure. This NASA Instrument Incubator Program project is a collaboration between Ohio State University, the University of Kansas, Vexcel Corporation and NASA. The GISMO design utilizes an interferometric SAR (InSAR) strategy in which <span class="hlt">ice</span> sheet reflected signals received by a dual-antenna system are used to produce an interference pattern. The resulting interferogram can be used to filter out surface clutter so as to reveal the signals scattered from the <span class="hlt">base</span> of the <span class="hlt">ice</span> sheet. These signals are further processed to produce 3D-images representing basal topography of the <span class="hlt">ice</span> sheet. In the past three years, the GISMO airborne field campaigns that have been conducted provide a set of useful data for studying geophysical properties of the Greenland <span class="hlt">ice</span> sheet. While topography information can be obtained using interferometric SAR processing techniques, <span class="hlt">ice</span> sheet roughness statistics can also be derived by a relatively simple procedure that involves analyzing power levels and the shape of the radar impulse response waveforms. An electromagnetic scattering model describing GISMO impulse responses has previously been proposed and validated. This model suggested that rms-heights and correlation lengths of the upper surface profile can be determined from the peak power and the decay rate of the pulse return waveform, respectively. This presentation will demonstrate a procedure for estimating the roughness of <span class="hlt">ice</span> surfaces by fitting the GISMO impulse response model to retrieved waveforms from selected GISMO flights. Furthermore, an extension of this procedure to estimate the scattering coefficient of the glacier bed will be addressed as well. Planned future applications involving the classification of glacier bed conditions <span class="hlt">based</span> on the derived scattering coefficients will also be described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.T41E2986K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.T41E2986K"><span>Arctic Ocean Sedimentary <span class="hlt">Cover</span> Structure, <span class="hlt">Based</span> on 2D MCS Seismic Data.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kireev, A.; Kaminsky, V.; Poselov, V.; Poselova, L.; Kaminsky, D.</p> <p>2016-12-01</p> <p>In 2016 the Russian Federation has submitted its partial revised Submission for establishment of the OLCS (outer limit of the continental shelf) in the Arctic Ocean. In order to prepare the Submission, in 2005 - 2014 the Russian organizations carried out a wide range of geological and geophysical studies, so that today over 23000 km of MCS lines and 4000 km of deep seismic sounding are accomplished. For correct time/depth conversion of seismic sections obtained with a short streamer in difficult <span class="hlt">ice</span> conditions wide-angle reflection/refraction seismic sonobuoy soundings were used. All of these seismic data were used to refine the stratigraphy model, to identify sedimentary complexes and to estimate the total thickness of the sedimentary <span class="hlt">cover</span>. Seismic stratigraphy model was successively determined for the Cenozoic and pre-Cenozoic parts of the sedimentary section and was <span class="hlt">based</span> on correlation of the Russian MCS data and seismic data documented by boreholes. Cenozoic part of the sedimentary <span class="hlt">cover</span> is <span class="hlt">based</span> on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge for Amerasia basin and by correlation of onlap contacts onto oceanic crust with defined magnetic anomalies for Eurasia basin. Pre-Cenozoic part of the sedimentary <span class="hlt">cover</span> is <span class="hlt">based</span> on tracing major unconformities from boreholes on the Chukchi shelf (Crackerjack, Klondike, Popcorn) to the North-Chuckchi Trough and further to the Mendeleev Rise as well as to the Vilkitsky Trough and the adjacent Podvodnikov Basin. Six main unconformities were traced: regional unconformity (RU), Eocene unconformity (EoU) (for Eurasia basin only), post-Campanian unconformity (pCU), Brookian (BU - <span class="hlt">base</span> of the Lower Brookian unit), Lower Cretaceous (LCU) and Jurassic (JU - top of the Upper Ellesmerian unit). The final step in our research was to generalize all seismic surveys (top of acoustic basement correlation data) and bathymetry data in the sedimentary <span class="hlt">cover</span> thickness map</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51B0713H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51B0713H"><span>Probability <span class="hlt">based</span> hydrologic catchments of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hudson, B. D.</p> <p>2015-12-01</p> <p>Greenland <span class="hlt">Ice</span> Sheet melt water impacts <span class="hlt">ice</span> sheet flow dynamics, fjord and coastal circulation, and sediment and biogeochemical fluxes. Melt water exiting the <span class="hlt">ice</span> sheet also is a key term in its mass balance. Because of this, knowledge of the area of the <span class="hlt">ice</span> sheet that contributes melt water to a given outlet (its hydrologic catchment) is important to many <span class="hlt">ice</span> sheet studies and is especially critical to methods using river runoff to assess <span class="hlt">ice</span> sheet mass balance. Yet uncertainty in delineating <span class="hlt">ice</span> sheet hydrologic catchments is a problem that is rarely acknowledged. <span class="hlt">Ice</span> sheet catchments are delineated as a function of both basal and surface topography. While surface topography is well known, basal topography is less certain because it is dependent on radar surveys. Here, I a present a Monte Carlo <span class="hlt">based</span> approach to delineating <span class="hlt">ice</span> sheet catchments that quantifies the impact of uncertain basal topography. In this scheme, over many iterations I randomly vary the <span class="hlt">ice</span> sheet bed elevation within published error bounds (using Morlighem et al., 2014 bed and bed error datasets). For each iteration of <span class="hlt">ice</span> sheet bed elevation, I calculate the hydraulic potentiometric surface and route water over its path of 'steepest' descent to delineate the catchment. I then use all realizations of the catchment to arrive at a probability map of all major melt water outlets in Greenland. I often find that catchment size is uncertain, with small, random perturbations in basal topography leading to large variations in catchments size. While some catchments are well defined, others can double or halve in size within published basal topography error bars. While some uncertainty will likely always remain, this work points to locations where studies of <span class="hlt">ice</span> sheet hydrology would be the most successful, allows reinterpretation of past results, and points to where future radar surveys would be most advantageous.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B23G..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B23G..08P"><span>Sources and sinks of methane beneath polar <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Priscu, J. C.; Adams, H. E.; Hand, K. P.; Dore, J. E.; Matheus-Carnevali, P.; Michaud, A. B.; Murray, A. E.; Skidmore, M. L.; Vick-Majors, T.</p> <p>2014-12-01</p> <p>Several icy moons of the outer solar system carry subsurface oceans containing many times the volume of liquid water on Earth and may provide the greatest volume of habitable space in our solar system. Functional sub-<span class="hlt">ice</span> polar ecosystems on Earth provide compelling models for the habitability of extraterrestrial sub-<span class="hlt">ice</span> oceans. A key feature of sub-<span class="hlt">ice</span> environments is that most of them receive little to no solar energy. Consequently, organisms inhabiting these environments must rely on chemical energy to assimilate either carbon dioxide or organic molecules to support their metabolism. Methane can be utilized by certain bacteria as both a carbon and energy source. Isotopic data show that methane in Earth's polar lakes is derived from both biogenic and thermogenic sources. Thermogenic sources of methane in the thermokarst lakes of the north slope of Alaska yield supersaturated water columns during winter <span class="hlt">ice</span> <span class="hlt">cover</span> that support active populations of methanotrophs during the polar night. Methane in the permanently <span class="hlt">ice-covered</span> lakes of the McMurdo Dry Valleys, Antarctica varies widely in concentration and is produced either by contemporary methanogenesis or is a relic from subglacial flow. Rate measurements revealed that microbial methane oxidation occurs beneath the <span class="hlt">ice</span> in both the arctic and Antarctic lakes. The first samples collected from an Antarctic subglacial environment beneath 800 m of <span class="hlt">ice</span> (Subglacial Lake Whillans) revealed an active microbial ecosystem that has been isolated from the atmosphere for many thousands of years. The sediments of Lake Whillans contained high levels of methane with an isotopic signature that indicates it was produced via methanogenesis. The source of this methane appears to be from the decomposition of organic carbon deposited when this region of Antarctica was <span class="hlt">covered</span> by the sea. Collectively, data from these sub-<span class="hlt">ice</span> environments show that methane transformations play a key role in microbial community metabolism. The discovery of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA617626','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA617626"><span>Forecasting Future Sea <span class="hlt">Ice</span> Conditions: A Lagrangian Approach</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>perennial sea <span class="hlt">ice</span> <span class="hlt">cover</span> and two projection periods in the 21st Century (2040- 2060 and 2080- 2080). OBJECTIVES 1- Reduce uncertainties in future...climate and the transitional period to a summer <span class="hlt">ice</span> free Arctic (2040- 2060 ) and a virtually <span class="hlt">ice</span>-free Arctic (2080-2100). IMPACT/APPLICATIONS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P34A..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P34A..05S"><span>Breaking <span class="hlt">Ice</span>: Fracture Processes in Floating <span class="hlt">Ice</span> on Earth and Elsewhere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scambos, T. A.</p> <p>2016-12-01</p> <p>Rapid, intense fracturing events in the <span class="hlt">ice</span> shelves of the Antarctic Peninsula reveal a set of processes that were not fully appreciated prior to the series of <span class="hlt">ice</span> shelf break-ups observed in the late 1990s and early 2000s. A series of studies have uncovered a fascinating array of relationships between climate, ocean, and <span class="hlt">ice</span>: intense widespread hydrofracture; repetitive hydrofracture induced by <span class="hlt">ice</span> plate bending; the ability for sub-surface flooded firn to support hydrofracture; potential triggering by long-period wave action; accelerated fracturing by trapped tsunamic waves; iceberg disintegration, and a remarkable <span class="hlt">ice</span> rebound process from lake drainage that resembles runaway nuclear fission. The events and subsequent studies have shown that rapid regional warming in <span class="hlt">ice</span> shelf areas leads to catastrophic changes in a previously stable <span class="hlt">ice</span> mass. More typical fracturing of thick <span class="hlt">ice</span> plates is a natural consequence of <span class="hlt">ice</span> flow in a complex geographic setting, i.e., it is induced by shear and divergence of spreading plate flow around obstacles. While these are not a result of climate or ocean change, weather and ocean processes may impact the exact timing of final separation of an iceberg from a shelf. Taking these terrestrial perspectives to other <span class="hlt">ice-covered</span> ocean worlds, cautiously, provides an observational framework for interpreting features on Europa and Enceladus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26ES...63a2001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26ES...63a2001S"><span>Internet of Things <span class="hlt">Based</span> Combustible <span class="hlt">Ice</span> Safety Monitoring System Framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Enji</p> <p>2017-05-01</p> <p>As the development of human society, more energy is requires to meet the need of human daily lives. New energies play a significant role in solving the problems of serious environmental pollution and resources exhaustion in the present world. Combustible <span class="hlt">ice</span> is essentially frozen natural gas, which can literally be lit on fire bringing a whole new meaning to fire and <span class="hlt">ice</span> with less pollutant. This paper analysed the advantages and risks on the uses of combustible <span class="hlt">ice</span>. By compare to other kinds of alternative energies, the advantages of the uses of combustible <span class="hlt">ice</span> were concluded. The combustible <span class="hlt">ice</span> basic physical characters and safety risks were analysed. The developments troubles and key utilizations of combustible <span class="hlt">ice</span> were predicted in the end. A real-time safety monitoring system framework <span class="hlt">based</span> on the internet of things (IOT) was built to be applied in the future mining, which provide a brand new way to monitoring the combustible <span class="hlt">ice</span> mining safety.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C21D..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C21D..01D"><span>Snow <span class="hlt">cover</span> data records from satellite and conventional measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Derksen, C.; Brown, R.; Wang, L.</p> <p>2008-12-01</p> <p> coupled with lake <span class="hlt">ice</span> model simulations have illustrated frequency dependent, seasonally evolving relationships between brightness temperature and lake fraction across tundra regions. A potential solution <span class="hlt">based</span> on the temporal evolution of 37 GHz AMSR-E measurements shows some promise as this was found to be significantly correlated with field measurements of tundra SWE, and to be relatively insensitive to lake fraction. New pan-Arctic (N 60°N) snowmelt onset and end date records (2000-2006) were produced from enhanced resolution (4.45 km) QuikSCAT (QSCAT) Ku-band backscatter measurements. The goal is to merge this with melt onset information from other components of the cryosphere (e.g. glaciers, <span class="hlt">ice</span> caps, <span class="hlt">ice</span> sheets, lake <span class="hlt">ice</span>, sea <span class="hlt">ice</span>) to provide an integrated circumpolar melt onset and duration dataset for climate monitoring and research on cryosphere-climate links and feedbacks. A major challenge is expanding the relatively short time period of Ku-band satellite measurements with historical C-band data (i.e. from ERS-1). Geostatistical methods and snow <span class="hlt">cover</span> modeling were used to develop a 10-km gridded SWE dataset over Quebec from 1970-2005 for climate studies and evaluation of the performance of the Canadian Regional Climate Model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C53B0574L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C53B0574L"><span><span class="hlt">Ice</span> Shelf-Ocean Interactions Near <span class="hlt">Ice</span> Rises and <span class="hlt">Ice</span> Rumples</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lange, M. A.; Rückamp, M.; Kleiner, T.</p> <p>2013-12-01</p> <p>The stability of <span class="hlt">ice</span> shelves depends on the existence of embayments and is largely influenced by <span class="hlt">ice</span> rises and <span class="hlt">ice</span> rumples, which act as 'pinning-points' for <span class="hlt">ice</span> shelf movement. Of additional critical importance are interactions between <span class="hlt">ice</span> shelves and the water masses underlying them in <span class="hlt">ice</span> shelf cavities, particularly melting and refreezing processes. The present study aims to elucidate the role of <span class="hlt">ice</span> rises and <span class="hlt">ice</span> rumples in the context of climate change impacts on Antarctic <span class="hlt">ice</span> shelves. However, due to their smaller spatial extent, <span class="hlt">ice</span> rumples react more sensitively to climate change than <span class="hlt">ice</span> rises. Different forcings are at work and need to be considered separately as well as synergistically. In order to address these issues, we have decided to deal with the following three issues explicitly: oceanographic-, cryospheric and general topics. In so doing, we paid particular attention to possible interrelationships and feedbacks in a coupled <span class="hlt">ice</span>-shelf-ocean system. With regard to oceanographic issues, we have applied the ocean circulation model ROMBAX to ocean water masses adjacent to and underneath a number of idealized <span class="hlt">ice</span> shelf configurations: wide and narrow as well as laterally restrained and unrestrained <span class="hlt">ice</span> shelves. Simulations were performed with and without small <span class="hlt">ice</span> rises located close to the calving front. For larger configurations, the impact of the <span class="hlt">ice</span> rises on melt rates at the <span class="hlt">ice</span> shelf <span class="hlt">base</span> is negligible, while for smaller configurations net melting rates at the <span class="hlt">ice</span>-shelf <span class="hlt">base</span> differ by a factor of up to eight depending on whether <span class="hlt">ice</span> rises are considered or not. We employed the thermo-coupled <span class="hlt">ice</span> flow model TIM-FD3 to simulate the effects of several <span class="hlt">ice</span> rises and one <span class="hlt">ice</span> rumple on the dynamics of <span class="hlt">ice</span> shelf flow. We considered the complete un-grounding of the <span class="hlt">ice</span> shelf in order to investigate the effect of pinning points of different characteristics (interior or near calving front, small and medium sized) on the resulting flow and stress fields</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CliPa..13...39M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CliPa..13...39M"><span>Sea <span class="hlt">ice</span> and pollution-modulated changes in Greenland <span class="hlt">ice</span> core methanesulfonate and bromine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maselli, Olivia J.; Chellman, Nathan J.; Grieman, Mackenzie; Layman, Lawrence; McConnell, Joseph R.; Pasteris, Daniel; Rhodes, Rachael H.; Saltzman, Eric; Sigl, Michael</p> <p>2017-01-01</p> <p>Reconstruction of past changes in Arctic sea <span class="hlt">ice</span> extent may be critical for understanding its future evolution. Methanesulfonate (MSA) and bromine concentrations preserved in <span class="hlt">ice</span> cores have both been proposed as indicators of past sea <span class="hlt">ice</span> conditions. In this study, two <span class="hlt">ice</span> cores from central and north-eastern Greenland were analysed at sub-annual resolution for MSA (CH3SO3H) and bromine, <span class="hlt">covering</span> the time period 1750-2010. We examine correlations between <span class="hlt">ice</span> core MSA and the HadISST1 <span class="hlt">ICE</span> sea <span class="hlt">ice</span> dataset and consult back trajectories to infer the likely source regions. A strong correlation between the low-frequency MSA and bromine records during pre-industrial times indicates that both chemical species are likely linked to processes occurring on or near sea <span class="hlt">ice</span> in the same source regions. The positive correlation between <span class="hlt">ice</span> core MSA and bromine persists until the mid-20th century, when the acidity of Greenland <span class="hlt">ice</span> begins to increase markedly due to increased fossil fuel emissions. After that time, MSA levels decrease as a result of declining sea <span class="hlt">ice</span> extent but bromine levels increase. We consider several possible explanations and ultimately suggest that increased acidity, specifically nitric acid, of snow on sea <span class="hlt">ice</span> stimulates the release of reactive Br from sea <span class="hlt">ice</span>, resulting in increased transport and deposition on the Greenland <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10511299K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10511299K"><span>Results of the Sea <span class="hlt">Ice</span> Model Intercomparison Project: Evaluation of sea <span class="hlt">ice</span> rheology schemes for use in climate simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kreyscher, Martin; Harder, Markus; Lemke, Peter; Flato, Gregory M.</p> <p>2000-05-01</p> <p>A hierarchy of sea <span class="hlt">ice</span> rheologies is evaluated on the basis of a comprehensive set of observational data. The investigations are part of the Sea <span class="hlt">Ice</span> Model Intercomparison Project (SIMIP). Four different sea <span class="hlt">ice</span> rheology schemes are compared: a viscous-plastic rheology, a cavitating-fluid model, a compressible Newtonian fluid, and a simple free drift approach with velocity correction. The same grid, land boundaries, and forcing fields are applied to all models. As verification data, there are (1) <span class="hlt">ice</span> thickness data from upward looking sonars (ULS), (2) <span class="hlt">ice</span> concentration data from the passive microwave radiometers SMMR and SSM/I, (3) daily buoy drift data obtained by the International Arctic Buoy Program (IABP), and (4) satellite-derived <span class="hlt">ice</span> drift fields <span class="hlt">based</span> on the 85 GHz channel of SSM/I. All models are optimized individually with respect to mean drift speed and daily drift speed statistics. The impact of <span class="hlt">ice</span> strength on the <span class="hlt">ice</span> <span class="hlt">cover</span> is best revealed by the spatial pattern of <span class="hlt">ice</span> thickness, <span class="hlt">ice</span> drift on different timescales, daily drift speed statistics, and the drift velocities in Fram Strait. Overall, the viscous-plastic rheology yields the most realistic simulation. In contrast, the results of the very simple free-drift model with velocity correction clearly show large errors in simulated <span class="hlt">ice</span> drift as well as in <span class="hlt">ice</span> thicknesses and <span class="hlt">ice</span> export through Fram Strait compared to observation. The compressible Newtonian fluid cannot prevent excessive <span class="hlt">ice</span> thickness buildup in the central Arctic and overestimates the internal forces in Fram Strait. Because of the lack of shear strength, the cavitating-fluid model shows marked differences to the statistics of observed <span class="hlt">ice</span> drift and the observed spatial pattern of <span class="hlt">ice</span> thickness. Comparison of required computer resources demonstrates that the additional cost for the viscous-plastic sea <span class="hlt">ice</span> rheology is minor compared with the atmospheric and oceanic model components in global climate simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C43B0744A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C43B0744A"><span>Spatial scales of light transmission through Antarctic pack <span class="hlt">ice</span>: Surface flooding vs. floe-size distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arndt, S.; Meiners, K.; Krumpen, T.; Ricker, R.; Nicolaus, M.</p> <p>2016-12-01</p> <p>Snow on sea <span class="hlt">ice</span> plays a crucial role for interactions between the ocean and atmosphere within the climate system of polar regions. Antarctic sea <span class="hlt">ice</span> is <span class="hlt">covered</span> with snow during most of the year. The snow contributes substantially to the sea-<span class="hlt">ice</span> mass budget as the heavy snow loads can depress the <span class="hlt">ice</span> below water level causing flooding. Refreezing of the snow and seawater mixture results in snow-<span class="hlt">ice</span> formation on the <span class="hlt">ice</span> surface. The snow <span class="hlt">cover</span> determines also the amount of light being reflected, absorbed, and transmitted into the upper ocean, determining the surface energy budget of <span class="hlt">ice-covered</span> oceans. The amount of light penetrating through sea <span class="hlt">ice</span> into the upper ocean is of critical importance for the timing and amount of bottom sea-<span class="hlt">ice</span> melt, biogeochemical processes and under-<span class="hlt">ice</span> ecosystems. Here, we present results of several recent observations in the Weddell Sea measuring solar radiation under Antarctic sea <span class="hlt">ice</span> with instrumented Remotely Operated Vehicles (ROV). The combination of under-<span class="hlt">ice</span> optical measurements with simultaneous characterization of surface properties, such as sea-<span class="hlt">ice</span> thickness and snow depth, allows the identification of key processes controlling the spatial distribution of the under-<span class="hlt">ice</span> light. Thus, our results show how the distinction between flooded and non-flooded sea-<span class="hlt">ice</span> regimes dominates the spatial scales of under-<span class="hlt">ice</span> light variability for areas smaller than 100-by-100m. In contrast, the variability on larger scales seems to be controlled by the floe-size distribution and the associated lateral incidence of light. These results are related to recent studies on the spatial variability of Arctic under-<span class="hlt">ice</span> light fields focusing on the distinctly differing dominant surface properties between the northern (e.g. summer melt ponds) and southern (e.g. year-round snow <span class="hlt">cover</span>, surface flooding) hemisphere sea-<span class="hlt">ice</span> <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22715789','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22715789"><span>[Spectral features analysis of sea <span class="hlt">ice</span> in the Arctic Ocean].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ke, Chang-qing; Xie, Hong-jie; Lei, Rui-bo; Li, Qun; Sun, Bo</p> <p>2012-04-01</p> <p>Sea <span class="hlt">ice</span> in the Arctic Ocean plays an important role in the global climate change, and its quick change and impact are the scientists' focus all over the world. The spectra of different kinds of sea <span class="hlt">ice</span> were measured with portable ASD FieldSpec 3 spectrometer during the long-term <span class="hlt">ice</span> station of the 4th Chinese national Arctic Expedition in 2010, and the spectral features were analyzed systematically. The results indicated that the reflectance of sea <span class="hlt">ice</span> <span class="hlt">covered</span> by snow is the highest one, naked sea <span class="hlt">ice</span> the second, and melted sea <span class="hlt">ice</span> the lowest. Peak and valley characteristics of spectrum curves of sea <span class="hlt">ice</span> <span class="hlt">covered</span> by thick snow, thin snow, wet snow and snow crystal are very significant, and the reflectance basically decreases with the wavelength increasing. The rules of reflectance change with wavelength of natural sea <span class="hlt">ice</span>, white <span class="hlt">ice</span> and blue <span class="hlt">ice</span> are basically same, the reflectance of them is medium, and that of grey <span class="hlt">ice</span> is far lower than natural sea <span class="hlt">ice</span>, white <span class="hlt">ice</span> and blue <span class="hlt">ice</span>. It is very significant for scientific research to analyze the spectral features of sea <span class="hlt">ice</span> in the Arctic Ocean and to implement the quantitative remote sensing of sea <span class="hlt">ice</span>, and to further analyze its response to the global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPA13A1975T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPA13A1975T"><span>Guide to Sea <span class="hlt">Ice</span> Information and Sea <span class="hlt">Ice</span> Data Online - the Sea <span class="hlt">Ice</span> Knowledge and Data Platform www.meereisportal.de and www.seaiceportal.de</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Treffeisen, R. E.; Nicolaus, M.; Bartsch, A.; Fritzsch, B.; Grosfeld, K.; Haas, C.; Hendricks, S.; Heygster, G.; Hiller, W.; Krumpen, T.; Melsheimer, C.; Ricker, R.; Weigelt, M.</p> <p>2016-12-01</p> <p>The combination of multi-disciplinary sea <span class="hlt">ice</span> science and the rising demand of society for up-to-date information and user customized products places emphasis on creating new ways of communication between science and society. The new knowledge platform is a contribution to the cross-linking of scientifically qualified information on climate change, and focuses on the theme: `sea <span class="hlt">ice</span>' in both Polar Regions. With this platform, the science opens to these changing societal demands. It is the first comprehensive German speaking knowledge platform on sea <span class="hlt">ice</span>; the platform went online in 2013. The web site delivers popularized information for the general public as well as scientific data meant primarily for the more expert readers and scientists. It also provides various tools allowing for visitor interaction. The demand for the web site indicates a high level of interest from both the general public and experts. It communicates science-<span class="hlt">based</span> information to improve awareness and understanding of sea <span class="hlt">ice</span> related research. The principle concept of the new knowledge platform is <span class="hlt">based</span> on three pillars: (1) sea <span class="hlt">ice</span> knowledge and background information, (2) data portal with visualizations, and (3) expert knowledge, latest research results and press releases. Since then, the content and selection of data sets increased and the data portal received increasing attention, also from the international science community. Meanwhile, we are providing near-real time and archived data of many key parameters of sea <span class="hlt">ice</span> and its snow <span class="hlt">cover</span>. The data sets result from measurements acquired by various platforms as well as numerical simulations. Satellite observations (e.g., AMSR2, CryoSat-2 and SMOS) of sea <span class="hlt">ice</span> concentration, freeboard, thickness and drift are available as gridded data sets. Sea <span class="hlt">ice</span> and snow temperatures and thickness as well as atmospheric parameters are available from autonomous <span class="hlt">ice</span>-tethered platforms (buoys). Additional ship observations, <span class="hlt">ice</span> station measurements, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.1497K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.1497K"><span>Sea-<span class="hlt">ice</span> thickness from field measurements in the northwestern Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>King, Jennifer; Spreen, Gunnar; Gerland, Sebastian; Haas, Christian; Hendricks, Stefan; Kaleschke, Lars; Wang, Caixin</p> <p>2017-02-01</p> <p>The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter-time sea-<span class="hlt">ice</span> area in the Arctic, at -23±4% decade-1. Sea-<span class="hlt">ice</span> thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter-borne electromagnetic (HEM) <span class="hlt">ice</span> thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to <span class="hlt">ice</span> thickness calculated from <span class="hlt">ice</span> draft measured by ULS deployed between 1994 and 1996. These data show that <span class="hlt">ice</span> thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long-range advection. In a year with a large inflow of sea-<span class="hlt">ice</span> from the Arctic Basin, the Barents Sea <span class="hlt">ice</span> <span class="hlt">cover</span> is dominated by thick multiyear <span class="hlt">ice</span>; as was the case in 2003 and 1995. In a year with an <span class="hlt">ice</span> <span class="hlt">cover</span> that was mainly grown in situ, the <span class="hlt">ice</span> will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in <span class="hlt">ice</span> thickness. In 2003 the dominant <span class="hlt">ice</span> class was more than 2 years old; and modal sea-<span class="hlt">ice</span> thickness varied regionally from 0.6 to 1.4 m, with the thinner <span class="hlt">ice</span> being either first-year <span class="hlt">ice</span>, or multiyear <span class="hlt">ice</span> which had come into contact with warm Atlantic water. In 2014 the <span class="hlt">ice</span> <span class="hlt">cover</span> was predominantly locally grown <span class="hlt">ice</span> less than 1 month old (regional modes of 0.5-0.8 m). These two situations represent two extremes of a range of possible <span class="hlt">ice</span> thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009093','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009093"><span>The Antarctic <span class="hlt">Ice</span> Sheet, Sea <span class="hlt">Ice</span>, and the Ozone Hole: Satellite Observations of how they are Changing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>2012-01-01</p> <p>Antarctica is the Earth's coldest and highest continent and has major impacts on the climate and life of the south polar vicinity. It is <span class="hlt">covered</span> almost entirely by the Earth's largest <span class="hlt">ice</span> sheet by far, with a volume of <span class="hlt">ice</span> so great that if all the Antarctic <span class="hlt">ice</span> were to go into the ocean (as <span class="hlt">ice</span> or liquid water), this would produce a global sea level rise of about 60 meters (197 feet). The continent is surrounded by sea <span class="hlt">ice</span> that in the wintertime is even more expansive than the continent itself and in the summertime reduces to only about a sixth of its wintertime extent. Like the continent, the expansive sea <span class="hlt">ice</span> <span class="hlt">cover</span> has major impacts, reflecting the sun's radiation back to space, blocking exchanges between the ocean and the atmosphere, and providing a platform for some animal species while impeding other species. Far above the continent, the Antarctic ozone hole is a major atmospheric phenomenon recognized as human-caused and potentially quite serious to many different life forms. Satellites are providing us with remarkable information about the <span class="hlt">ice</span> sheet, the sea <span class="hlt">ice</span>, and the ozone hole. Satellite visible and radar imagery are providing views of the large scale structure of the <span class="hlt">ice</span> sheet never seen before; satellite laser altimetry has produced detailed maps of the topography of the <span class="hlt">ice</span> sheet; and an innovative gravity-measuring two-part satellite has allowed mapping of regions of mass loss and mass gain on the <span class="hlt">ice</span> sheet. The surrounding sea <span class="hlt">ice</span> <span class="hlt">cover</span> has a satellite record that goes back to the 1970s, allowing trend studies that show a decreasing sea <span class="hlt">ice</span> presence in the region of the Bellingshausen and Amundsen seas, to the west of the prominent Antarctic Peninsula, but increasing sea <span class="hlt">ice</span> presence around much of the rest of the continent. Overall, sea <span class="hlt">ice</span> extent around Antarctica has increased at an average rate of about 17,000 square kilometers per year since the late 1970s, as determined from satellite microwave data that can be collected under both light and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730011671','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730011671"><span>Survey of the seasonal snow <span class="hlt">cover</span> in Alaska</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weller, G. E. (Principal Investigator)</p> <p>1973-01-01</p> <p>The author has identified the following significant results. ERTS-1 data are used together with synoptic-climatological data to describe the buildup of the seasonal snow and <span class="hlt">ice</span> <span class="hlt">covers</span> in a north-south transect of a total length of about 1250 km across Alaska. It has been demonstrated that the ERTS-1 data may, under favorable conditions, be used for accurate mapping of snow lines in high mountain regions. The analysis shows that especially in the Brooks Range and on the Arctic Slope where snow <span class="hlt">covers</span> generally are relatively thin, the ERTS-1 scenes can be useful for qualitative descriptions of the snow and <span class="hlt">ice</span> <span class="hlt">covers</span> over wide expanses. The onset and retreat of the seasonal snow <span class="hlt">cover</span> are sensitive indicators of climatic fluctuations and the ERTS-1 data offers a possibility to record variations of the snow and <span class="hlt">ice</span> buildup from year to year in a practical and informative way, which should be especially useful for studies of climatic trends. This is particularly true in Alaska where the density of the station network is too low to permit interpolations between the stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Sci...341..266R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Sci...341..266R"><span><span class="hlt">Ice</span>-Shelf Melting Around Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.</p> <p>2013-07-01</p> <p>We compare the volume flux divergence of Antarctic <span class="hlt">ice</span> shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making <span class="hlt">ice</span>-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne <span class="hlt">ice</span> shelves <span class="hlt">covering</span> two-thirds of the total <span class="hlt">ice</span>-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific <span class="hlt">ice</span> shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic <span class="hlt">ice</span> shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C53A0279G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C53A0279G"><span>Rapid Access <span class="hlt">Ice</span> Drill: A New Tool for Exploration of the Deep Antarctic <span class="hlt">Ice</span> Sheets and Subglacial Geology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goodge, J. W.; Severinghaus, J. P.</p> <p>2014-12-01</p> <p>The Rapid Access <span class="hlt">Ice</span> Drill (RAID) will penetrate the Antarctic <span class="hlt">ice</span> sheets in order to core through deep <span class="hlt">ice</span>, the glacial bed, and into bedrock below. This new technology will provide a critical first look at the interface between major <span class="hlt">ice</span> caps and their subglacial geology. Currently in construction, RAID is a mobile drilling system capable of making several long boreholes in a single field season in Antarctica. RAID is interdisciplinary and will allow access to polar paleoclimate records in <span class="hlt">ice</span> >1 Ma, direct observation at the <span class="hlt">base</span> of the <span class="hlt">ice</span> sheets, and recovery of rock cores from the <span class="hlt">ice-covered</span> East Antarctic craton. RAID uses a diamond rock-coring system as in mineral exploration. Threaded drill-pipe with hardened metal bits will cut through <span class="hlt">ice</span> using reverse circulation of Estisol for pressure-compensation, maintenance of temperature, and removal of <span class="hlt">ice</span> cuttings. Near the bottom of the <span class="hlt">ice</span> sheet, a wireline bottom-hole assembly will enable diamond coring of <span class="hlt">ice</span>, the glacial bed, and bedrock below. Once complete, boreholes will be kept open with fluid, capped, and made available for future down-hole measurement of thermal gradient, heat flow, <span class="hlt">ice</span> chronology, and <span class="hlt">ice</span> deformation. RAID will also sample for extremophile microorganisms. RAID is designed to penetrate up to 3,300 meters of <span class="hlt">ice</span> and take sample cores in less than 200 hours. This rapid performance will allow completion of a borehole in about 10 days before moving to the next drilling site. RAID is unique because it can provide fast borehole access through thick <span class="hlt">ice</span>; take short <span class="hlt">ice</span> cores for paleoclimate study; sample the glacial bed to determine <span class="hlt">ice</span>-flow conditions; take cores of subglacial bedrock for age dating and crustal history; and create boreholes for use as an observatory in the <span class="hlt">ice</span> sheets. Together, the rapid drilling capability and mobility of the drilling system, along with <span class="hlt">ice</span>-penetrating imaging methods, will provide a unique 3D picture of the interior Antarctic <span class="hlt">ice</span> sheets.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A41C0063M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A41C0063M"><span>Convergence on the Prediction of <span class="hlt">Ice</span> Particle Mass and Projected Area in <span class="hlt">Ice</span> Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitchell, D. L.</p> <p>2013-12-01</p> <p><span class="hlt">Ice</span> particle mass- and area-dimensional power law (henceforth m-D and A-D) relationships are building-blocks for formulating microphysical processes and optical properties in cloud and climate models, and they are critical for <span class="hlt">ice</span> cloud remote sensing algorithms, affecting the retrieval accuracy. They can be estimated by (1) directly measuring the sizes, masses and areas of individual <span class="hlt">ice</span> particles at ground-level and (2) using aircraft probes to simultaneously measure the <span class="hlt">ice</span> water content (IWC) and <span class="hlt">ice</span> particle size distribution. A third indirect method is to use observations from method 1 to develop an m-A relationship representing mean conditions in <span class="hlt">ice</span> clouds. Owing to a tighter correlation (relative to m-D data), this m-A relationship can be used to estimate m from aircraft probe measurements of A. This has the advantage of estimating m at small sizes, down to 10 μm using the 2D-Sterio probe. In this way, 2D-S measurements of maximum dimension D can be related to corresponding estimates of m to develop <span class="hlt">ice</span> cloud type and temperature dependent m-D expressions. However, these expressions are no longer linear in log-log space, but are slowly varying curves <span class="hlt">covering</span> most of the size range of natural <span class="hlt">ice</span> particles. This work compares all three of the above methods and demonstrates close agreement between them. Regarding (1), 4869 <span class="hlt">ice</span> particles and corresponding melted hemispheres were measured during a field campaign to obtain D and m. Selecting only those unrimed habits that formed between -20°C and -40°C, the mean mass values for selected size intervals are within 35% of the corresponding masses predicted by the Method 3 curve <span class="hlt">based</span> on a similar temperature range. Moreover, the most recent m-D expression <span class="hlt">based</span> on Method 2 differs by no more than 50% with the m-D curve from Method 3. Method 3 appears to be the most accurate over the observed <span class="hlt">ice</span> particle size range (10-4000 μm). An m-D/A-D scheme was developed by which self-consistent m-D and A-D power laws</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5179961','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5179961"><span>Linking scales in sea <span class="hlt">ice</span> mechanics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Weiss, Jérôme; Dansereau, Véronique</p> <p>2017-01-01</p> <p>Mechanics plays a key role in the evolution of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> through its control on drift, on momentum and thermal energy exchanges between the polar oceans and the atmosphere along cracks and faults, and on <span class="hlt">ice</span> thickness distribution through opening and ridging processes. At the local scale, a significant variability of the mechanical strength is associated with the microstructural heterogeneity of saline <span class="hlt">ice</span>, however characterized by a small correlation length, below the <span class="hlt">ice</span> thickness scale. Conversely, the sea <span class="hlt">ice</span> mechanical fields (velocity, strain and stress) are characterized by long-ranged (more than 1000 km) and long-lasting (approx. few months) correlations. The associated space and time scaling laws are the signature of the brittle character of sea <span class="hlt">ice</span> mechanics, with deformation resulting from a multi-scale accumulation of episodic fracturing and faulting events. To translate the short-range-correlated disorder on strength into long-range-correlated mechanical fields, several key ingredients are identified: long-ranged elastic interactions, slow driving conditions, a slow viscous-like relaxation of elastic stresses and a restoring/healing mechanism. These ingredients constrained the development of a new continuum mechanics modelling framework for the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, called Maxwell–elasto-brittle. Idealized simulations without advection demonstrate that this rheological framework reproduces the main characteristics of sea <span class="hlt">ice</span> mechanics, including anisotropy, spatial localization and intermittency, as well as the associated scaling laws. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025300</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21G1192Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21G1192Z"><span>Under Sea <span class="hlt">Ice</span> phytoplankton bloom detection and contamination in Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, C.; Zeng, T.; Xu, H.</p> <p>2017-12-01</p> <p>Previous researches reported compelling sea <span class="hlt">ice</span> phytoplankton bloom in Arctic, while seldom reports studied about Antarctic. Here, lab experiment showed sea <span class="hlt">ice</span> increased the visible light albedo of the water leaving radiance. Even a new formed sea <span class="hlt">ice</span> of 10cm thickness increased water leaving radiance up to 4 times of its original bare water. Given that phytoplankton preferred growing and accumulating under the sea <span class="hlt">ice</span> with thickness of 10cm-1m, our results showed that the changing rate of OC4 estimated [Chl-a] varied from 0.01-0.5mg/m3 to 0.2-0.3mg/m3, if the water <span class="hlt">covered</span> by 10cm sea <span class="hlt">ice</span>. Going further, varying thickness of sea <span class="hlt">ice</span> modulated the changing rate of estimating [Chl-a] non-linearly, thus current routine OC4 model cannot estimate under sea <span class="hlt">ice</span> [Chl-a] appropriately. Besides, marginal sea <span class="hlt">ice</span> zone has a large amount of mixture regions containing sea <span class="hlt">ice</span>, water and snow, where is favorable for phytoplankton. We applied 6S model to estimate the sea <span class="hlt">ice</span>/snow contamination on sub-pixel water leaving radiance of 4.25km spatial resolution ocean color products. Results showed that sea <span class="hlt">ice</span>/snow scale effectiveness overestimated [Chl-a] concentration <span class="hlt">based</span> on routine band ratio OC4 model, which contamination increased with the rising fraction of sea <span class="hlt">ice</span>/snow within one pixel. Finally, we analyzed the under sea <span class="hlt">ice</span> bloom in Antarctica <span class="hlt">based</span> on the [Chl-a] concentration trends during 21 days after sea <span class="hlt">ice</span> retreating. Regardless of those overestimation caused by sea <span class="hlt">ice</span>/snow sub scale contamination, we still did not see significant under sea <span class="hlt">ice</span> blooms in Antarctica in 2012-2017 compared with Arctic. This research found that Southern Ocean is not favorable for under sea <span class="hlt">ice</span> blooms and the phytoplankton bloom preferred to occur in at least 3 weeks after sea <span class="hlt">ice</span> retreating.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/pp/0050/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/pp/0050/report.pdf"><span>The Montana lobe of the Keewatin <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Calhoun, F.H.H.</p> <p>1906-01-01</p> <p>The area <span class="hlt">covered</span> by this investigation lies along the eastern front of the Montana Rockies, between longitude 108° and 113° 40', and latitude 47° 15' and 49° 30'. Over the eastern and northern part of this area the <span class="hlt">ice</span> from the northeast deposited its drift. Over the western part the <span class="hlt">ice</span> from the Eockies pushed down the mountain valleys and, deploying on the plain, deposited large and well-defined terminal moraines. Extending from the Canadian line to the Missouri there is a strip of country, varying greatly in width, which the <span class="hlt">ice</span> did not <span class="hlt">cover</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C23B0494D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C23B0494D"><span>Improved parameterization of marine <span class="hlt">ice</span> dynamics and flow instabilities for simulation of the Austfonna <span class="hlt">ice</span> cap using a large-scale <span class="hlt">ice</span> sheet model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dunse, T.; Greve, R.; Schuler, T.; Hagen, J. M.; Navarro, F.; Vasilenko, E.; Reijmer, C.</p> <p>2009-12-01</p> <p>The Austfonna <span class="hlt">ice</span> cap <span class="hlt">covers</span> an area of 8120 km2 and is by far the largest glacier on Svalbard. Almost 30% of the entire area is grounded below sea-level, while the figure is as large as 57% for the known surge-type basins in particular. Marine <span class="hlt">ice</span> dynamics, as well as flow instabilities presumably control flow regime, form and evolution of Austfonna. These issues are our focus in numerical simulations of the <span class="hlt">ice</span> cap. We employ the thermodynamic, large-scale <span class="hlt">ice</span> sheet model SICOPOLIS (http://sicopolis.greveweb.net/) which is <span class="hlt">based</span> on the shallow-<span class="hlt">ice</span> approximation. We present improved parameterizations of (a) the marine extent and calving and (b) processes that may initiate flow instabilities such as switches from cold to temperate basal conditions, surface steepening and hence, increases in driving stress, enhanced sliding or deformation of unconsolidated marine sediments and diminishing <span class="hlt">ice</span> thicknesses towards flotation thickness. Space-borne interferometric snapshots of Austfonna revealed a velocity structure of a slow moving polar <span class="hlt">ice</span> cap (< 10m/a) interrupted by distinct fast flow units with velocities in excess of 100m/a. However, observations of flow variability are scarce. In spring 2008, we established a series of stakes along the centrelines of two fast-flowing units. Repeated DGPS and continuous GPS measurements of the stake positions give insight in the temporal flow variability of these units and provide constrains to the modeled surface velocity field. Austfonna’s thermal structure is described as polythermal. However, direct measurements of the temperature distribution is available only from one single borehole at the summit area. The vertical temperature profile shows that the bulk of the 567m thick <span class="hlt">ice</span> column is cold, only underlain by a thin temperate basal layer of approximately 20m. To acquire a spatially extended picture of the thermal structure (and bed topography), we used low-frequency (20 MHz) GPR profiling across the <span class="hlt">ice</span> cap and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C21A0312F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C21A0312F"><span>Using Airborne Lidar Data from <span class="hlt">Ice</span>Pod to Measure Annual and Seasonal <span class="hlt">Ice</span> Changes Over Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frearson, N.; Bertinato, C.; Das, I.</p> <p>2014-12-01</p> <p>The <span class="hlt">Ice</span>Pod is a multi-sensor airborne science platform that supports a wide suite of instruments, including a Riegl VQ-580 infrared scanning laser, GPS-inertial positioning system, shallow and deep-<span class="hlt">ice</span> radars, visible-wave and infrared cameras, and upward-looking pyrometer. These instruments allow us to image the <span class="hlt">ice</span> from top to bottom, including the surface of melt-water plumes that originate at the <span class="hlt">ice</span>-ocean boundary. In collaboration with the New York Air National Guard 109th Airlift Wing, the <span class="hlt">Ice</span>Pod is flown on LC-130 aircraft, which presents the unique opportunity to routinely image the Greenland <span class="hlt">ice</span> sheet several times within a season. This is particularly important for mass balance studies, as we can measure elevation changes during the melt season. During the 2014 summer, laser data was collected via <span class="hlt">Ice</span>Pod over the Greenland <span class="hlt">ice</span> sheet, including Russell Glacier, Jakobshavn Glacier, Eqip Glacier, and Summit Camp. The Icepod will also be routinely operated in Antarctica. We present the initial testing, calibration, and error estimates from the first set of laser data that were collected on <span class="hlt">Ice</span>Pod. At a survey altitude of 1000 m, the laser swath <span class="hlt">covers</span> ~ 1000 m. A Northrop-Grumman LN-200 tactical grade IMU is rigidly attached to the laser scanner to provide attitude data at a rate of 200 Hz. Several methods were used to determine the lever arm between the IMU center of navigation and GPS antenna phase center, terrestrial scanning laser, total station survey, and optimal estimation. Additionally, initial bore sight calibration flights yielded misalignment angles within an accuracy of ±4 cm. We also performed routine passes over the airport ramp in Kangerlussuaq, Greenland, comparing the airborne GPS and Lidar data to a reference GPS-<span class="hlt">based</span> ground survey across the ramp, spot GPS points on the ramp and a nearby GPS <span class="hlt">base</span> station. Positioning errors can severely impact the accuracy of a laser altimeter when flying over remote regions such as across the <span class="hlt">ice</span> sheets</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.7354L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.7354L"><span>Improving the simulation of landfast <span class="hlt">ice</span> by combining tensile strength and a parameterization for grounded ridges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lemieux, Jean-François; Dupont, Frédéric; Blain, Philippe; Roy, François; Smith, Gregory C.; Flato, Gregory M.</p> <p>2016-10-01</p> <p>In some coastal regions of the Arctic Ocean, grounded <span class="hlt">ice</span> ridges contribute to stabilizing and maintaining a landfast <span class="hlt">ice</span> <span class="hlt">cover</span>. Recently, a grounding scheme representing this effect on sea <span class="hlt">ice</span> dynamics was introduced and tested in a viscous-plastic sea <span class="hlt">ice</span> model. This grounding scheme, <span class="hlt">based</span> on a basal stress parameterization, improves the simulation of landfast <span class="hlt">ice</span> in many regions such as in the East Siberian Sea, the Laptev Sea, and along the coast of Alaska. Nevertheless, in some regions like the Kara Sea, the area of landfast <span class="hlt">ice</span> is systematically underestimated. This indicates that another mechanism such as <span class="hlt">ice</span> arching is at play for maintaining the <span class="hlt">ice</span> <span class="hlt">cover</span> fast. To address this problem, the combination of the basal stress parameterization and tensile strength is investigated using a 0.25° Pan-Arctic CICE-NEMO configuration. Both uniaxial and isotropic tensile strengths notably improve the simulation of landfast <span class="hlt">ice</span> in the Kara Sea but also in the Laptev Sea. However, the simulated landfast <span class="hlt">ice</span> season for the Kara Sea is too short compared to observations. This is especially obvious for the onset of the landfast <span class="hlt">ice</span> season which systematically occurs later in the model and with a slower build up. This suggests that improvements to the sea <span class="hlt">ice</span> thermodynamics could reduce these discrepancies with the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRD..123..473M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRD..123..473M"><span>Isolating the Liquid Cloud Response to Recent Arctic Sea <span class="hlt">Ice</span> Variability Using Spaceborne Lidar Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morrison, A. L.; Kay, J. E.; Chepfer, H.; Guzman, R.; Yettella, V.</p> <p>2018-01-01</p> <p>While the radiative influence of clouds on Arctic sea <span class="hlt">ice</span> is known, the influence of sea <span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two-way relationship between sea <span class="hlt">ice</span> <span class="hlt">cover</span> and Arctic clouds is important for predicting the rate of future sea <span class="hlt">ice</span> loss. Here we use 8 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea <span class="hlt">ice</span> and over open water. Using a novel surface mask to restrict our analysis to where sea <span class="hlt">ice</span> concentration varies, we isolate the influence of sea <span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid-containing clouds are the most important cloud type for radiative fluxes and therefore for sea <span class="hlt">ice</span> melt and growth. Summer is the only season with no observed cloud response to sea <span class="hlt">ice</span> <span class="hlt">cover</span> variability: liquid cloud profiles are nearly identical over sea <span class="hlt">ice</span> and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long-term summer sea <span class="hlt">ice</span> loss. In contrast, more liquid clouds are observed over open water than over sea <span class="hlt">ice</span> in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea <span class="hlt">ice</span> loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud <span class="hlt">cover</span> over newly open water are linked to human activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171250','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171250"><span>ICESat Observations of Arctic Sea <span class="hlt">Ice</span>: A First Look</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kwok, Ron; Zwally, H. Jay; Yi, Dong-Hui</p> <p>2004-01-01</p> <p>Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin <span class="hlt">ice</span> or open water) in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> as well as to surface relief of old and first-year <span class="hlt">ice</span>. The precision of the elevation estimates, measured over relatively flat sea <span class="hlt">ice</span>, is approx. 2 cm Using the thickness of thin-<span class="hlt">ice</span> in recent openings to estimate sea level references, we obtain the sea-<span class="hlt">ice</span> free-board along the altimeter tracks. This step is necessitated by the large uncertainties in the time-varying sea surface topography compared to that required for accurate determination of free-board. Unknown snow depth introduces the largest uncertainty in the conversion of free-board to <span class="hlt">ice</span> thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean <span class="hlt">ice</span> <span class="hlt">cover</span> at length scales at and above the spatial dimension of the altimeter footprint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP11B2218B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP11B2218B"><span>Triple Isotope Water Measurements of Lake Untersee <span class="hlt">Ice</span> using Off-Axis ICOS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berman, E. S.; Huang, Y. W.; Andersen, D. T.; Gupta, M.; McKay, C. P.</p> <p>2015-12-01</p> <p>Lake Untersee (71.348°S, 13.458°E) is the largest surface freshwater lake in the interior of the Gruber Mountains of central Queen Maud Land in East Antarctica. The lake is permanently <span class="hlt">covered</span> with <span class="hlt">ice</span>, is partly bounded by glacier <span class="hlt">ice</span> and has a mean annual air temperature of -10°C. In contrast to other Antarctic lakes the dominating physical process controlling <span class="hlt">ice-cover</span> dynamics is low summer temperatures and high wind speeds resulting in sublimation rather than melting as the main mass-loss process. The <span class="hlt">ice-cover</span> of the lake is composed of lake-water <span class="hlt">ice</span> formed during freeze-up and rafted glacial <span class="hlt">ice</span> derived from the Anuchin Glacier. The mix of these two fractions impacts the energy balance of the lake, which directly affects <span class="hlt">ice-cover</span> thickness. <span class="hlt">Ice-cover</span> is important if one is to understand the physical, chemical, and biological linkages within these unique, physically driven ecosystems. We have analyzed δ2H, δ18O, and δ17O from samples of lake and glacier <span class="hlt">ice</span> collected at Lake Untersee in Dec 2014. Using these data we seek to answer two specific questions: Are we able to determine the origin and history of the lake <span class="hlt">ice</span>, discriminating between rafted glacial <span class="hlt">ice</span> and lake water? Can isotopic gradients in the surface <span class="hlt">ice</span> indicate the ablation (sublimation) rate of the surface <span class="hlt">ice</span>? The triple isotope water analyzer developed by Los Gatos Research (LGR 912-0032) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures δ2H, δ18O, and δ17O from water, as well as the calculated d-excess and 17O-excess. The laboratory precision in high performance mode for both δ17O and δ18O is 0.03 ‰, and for δ2H is 0.2 ‰. Methodology and isotope data from Lake Untersee samples are presented. Figure: <span class="hlt">Ice</span> samples were collected across Lake Untersee from both glacial and lake <span class="hlt">ice</span> regions for this study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4822405R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4822405R"><span>The Effect of Surface <span class="hlt">Ice</span> and Topography on the Atmospheric Circulation and Distribution of Nitrogen <span class="hlt">Ice</span> on Pluto</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rafkin, Scot C. R.; Soto, Alejandro; Michaels, Timothy I.</p> <p>2016-10-01</p> <p>A newly developed general circulation model (GCM) for Pluto is used to investigate the impact of a heterogeneous distribution of nitrogen surface <span class="hlt">ice</span> and large scale topography on Pluto's atmospheric circulation. The GCM is <span class="hlt">based</span> on the GFDL Flexible Modeling System (FSM). Physics include a gray model radiative-conductive scheme, subsurface conduction, and a nitrogen volatile cycle. The radiative-conductive model takes into account the 2.3, 3.3 and 7.8 μm bands of CH4 and CO, including non-local thermodynamic equilibrium effects. including non-local thermodynamic equilibrium effects. The nitrogen volatile cycle is <span class="hlt">based</span> on a vapor pressure equilibrium assumption between the atmosphere and surface. Prior to the arrival of the New Horizons spacecraft, the expectation was that the volatile <span class="hlt">ice</span> distribution on the surface of Pluto would be strongly controlled by the latitudinal temperature gradient. If this were the case, then Pluto would have broad latitudinal bands of both <span class="hlt">ice</span> <span class="hlt">covered</span> surface and <span class="hlt">ice</span> free surface, as dictated by the season. Further, the circulation, and the thus the transport of volatiles, was thought to be driven almost exclusively by sublimation and deposition flows associated with the volatile cycle. In contrast to expectations, images from New Horizon showed an extremely complex, heterogeneous distribution of surface <span class="hlt">ices</span> draped over substantial and variable topography. To produce such an <span class="hlt">ice</span> distribution, the atmospheric circulation and volatile transport must be more complex than previously envisioned. Simulations where topography, surface <span class="hlt">ice</span> distributions, and volatile cycle physics are added individually and in various combinations are used to individually quantify the importance of the general circulation, topography, surface <span class="hlt">ice</span> distributions, and condensation flows. It is shown that even regional patches of <span class="hlt">ice</span> or large craters can have global impacts on the atmospheric circulation, the volatile cycle, and hence, the distribution of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013QSRv...79..168A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013QSRv...79..168A"><span>A review of sea <span class="hlt">ice</span> proxy information from polar <span class="hlt">ice</span> cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abram, Nerilie J.; Wolff, Eric W.; Curran, Mark A. J.</p> <p>2013-11-01</p> <p>Sea <span class="hlt">ice</span> plays an important role in Earth's climate system. The lack of direct indications of past sea <span class="hlt">ice</span> coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea <span class="hlt">ice</span> dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea <span class="hlt">ice</span> conditions. Here we review the advances that have been made in using chemical tracers preserved in <span class="hlt">ice</span> cores to determine past changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span> around Antarctica. <span class="hlt">Ice</span> core records of sea salt concentration show promise for revealing patterns of sea <span class="hlt">ice</span> extent particularly over glacial-interglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea <span class="hlt">ice</span> indicator. Methane sulphonic acid (MSA) in near-coastal <span class="hlt">ice</span> cores has been used to reconstruct quantified changes and interannual variability in sea <span class="hlt">ice</span> extent over shorter time scales spanning the last ˜160 years, and has potential to be extended to produce records of Antarctic sea <span class="hlt">ice</span> changes throughout the Holocene. However the MSA <span class="hlt">ice</span> core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea <span class="hlt">ice</span> factors, and we summarise some recommended strategies for the further development of sea <span class="hlt">ice</span> histories from <span class="hlt">ice</span> core MSA. For both proxies the limited information about the production and transfer of chemical markers from the sea <span class="hlt">ice</span> zone to the Antarctic <span class="hlt">ice</span> sheets remains an issue that requires further multidisciplinary study. Despite some exploratory and statistical work, the application of either proxy as an indicator of sea <span class="hlt">ice</span> change in the Arctic also remains largely unknown. As information about these new <span class="hlt">ice</span> core proxies builds, so too does the potential to develop a more comprehensive understanding of past changes in sea</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010095442&hterms=Global+Warming+Climate+Change+Warning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DGlobal%2BWarming%2BClimate%2BChange%2BWarning','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010095442&hterms=Global+Warming+Climate+Change+Warning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DGlobal%2BWarming%2BClimate%2BChange%2BWarning"><span>Sea <span class="hlt">Ice</span> and <span class="hlt">Ice</span> Temperature Variability as Observed by Microwave and Infrared Satellite Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Koblinsky, Chester J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Recent reports of a retreating and thinning sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Arctic have pointed to a strong suggestion of significant warming in the polar regions. It is especially important to understand what these reports mean in light of the observed global warning and because the polar regions are expected to be most sensitive to changes in climate. To gain insight into this phenomenon, co-registered <span class="hlt">ice</span> concentrations and surface temperatures derived from two decades of satellite microwave and infrared data have been processed and analyzed. While observations from meteorological stations indicate consistent surface warming in both regions during the last fifty years, the last 20 years of the same data set show warming in the Arctic but a slight cooling in the Antarctic. These results are consistent with the retreat in the Arctic <span class="hlt">ice</span> <span class="hlt">cover</span> and the advance in the Antarctic <span class="hlt">ice</span> <span class="hlt">cover</span> as revealed by historical satellite passive microwave data. Surface temperatures derived from satellite infrared data are shown to be consistent within 3 K with surface temperature data from the limited number of stations. While not as accurate, the former provides spatially detailed changes over the twenty year period. In the Arctic, for example, much of the warming occurred in the Beaufort Sea and the North American region in 1998 while slight cooling actually happened in parts of the Laptev Sea and Northern Siberia during the same time period. Big warming anomalies are also observed during the last five years but a periodic cycle of about ten years is apparent suggesting a possible influence of the North Atlantic Oscillation. In the Antarctic, large interannual and seasonal changes are also observed in the circumpolar <span class="hlt">ice</span> <span class="hlt">cover</span> with regional changes showing good coherence with surface temperature anomalies. However, a mode 3 is observed to be more dominant than the mode 2 wave reported in the literature. Some of these spatial and temporal changes appear to be influenced by the Antarctic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.7657L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.7657L"><span>Optical properties of melting first-year Arctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Light, Bonnie; Perovich, Donald K.; Webster, Melinda A.; Polashenski, Christopher; Dadic, Ruzica</p> <p>2015-11-01</p> <p>The albedo and transmittance of melting, first-year Arctic sea <span class="hlt">ice</span> were measured during two cruises of the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded <span class="hlt">ice</span> types at a total of 19 <span class="hlt">ice</span> stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, <span class="hlt">ice</span> physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first-year Arctic sea <span class="hlt">ice</span>. Ponded <span class="hlt">ice</span> was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare <span class="hlt">ice</span>. The ubiquitous surface-scattering layer and drained layer present on bare, melting sea <span class="hlt">ice</span> are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded <span class="hlt">ice</span> depends on the physical thickness of the <span class="hlt">ice</span> and the magnitude of the scattering coefficient in the <span class="hlt">ice</span> interior. Bare <span class="hlt">ice</span> reflects nearly three-quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded <span class="hlt">ice</span> absorbs or transmits to the ocean more than three-quarters of the incident sunlight. Characterization of the heat balance of a summertime <span class="hlt">ice</span> <span class="hlt">cover</span> is largely dictated by its pond coverage, and light transmittance through ponded <span class="hlt">ice</span> shows strong contrast between first-year and multiyear Arctic <span class="hlt">ice</span> <span class="hlt">covers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation"><span>Studies of the Antarctic Sea <span class="hlt">Ice</span> Edges and <span class="hlt">Ice</span> Extents from Satellite and Ship Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Worby, Anthony P.; Comiso, Josefino C.</p> <p>2003-01-01</p> <p>Passive-microwave derived <span class="hlt">ice</span> edge locations in Antarctica are assessed against other satellite data as well as in situ observations of <span class="hlt">ice</span> edge location made between 1989 and 2000. The passive microwave data generally agree with satellite and ship data but the <span class="hlt">ice</span> concentration at the observed <span class="hlt">ice</span> edge varies greatly with averages of 14% for the TEAM algorithm and 19% for the Bootstrap algorithm. The comparisons of passive microwave with the field data show that in the <span class="hlt">ice</span> growth season (March - October) the agreement is extremely good, with r(sup 2) values of 0.9967 and 0.9797 for the Bootstrap and TEAM algorithms respectively. In the melt season however (November - February) the passive microwave <span class="hlt">ice</span> edge is typically 1-2 degrees south of the observations due to the low concentration and saturated nature of the <span class="hlt">ice</span>. Sensitivity studies show that these results can have significant impact on trend and mass balance studies of the sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the Southern Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21456825','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21456825"><span>Regular network model for the sea <span class="hlt">ice</span>-albedo feedback in the Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Müller-Stoffels, Marc; Wackerbauer, Renate</p> <p>2011-03-01</p> <p>The Arctic Ocean and sea <span class="hlt">ice</span> form a feedback system that plays an important role in the global climate. The complexity of highly parameterized global circulation (climate) models makes it very difficult to assess feedback processes in climate without the concurrent use of simple models where the physics is understood. We introduce a two-dimensional energy-<span class="hlt">based</span> regular network model to investigate feedback processes in an Arctic <span class="hlt">ice</span>-ocean layer. The model includes the nonlinear aspect of the <span class="hlt">ice</span>-water phase transition, a nonlinear diffusive energy transport within a heterogeneous <span class="hlt">ice</span>-ocean lattice, and spatiotemporal atmospheric and oceanic forcing at the surfaces. First results for a horizontally homogeneous <span class="hlt">ice</span>-ocean layer show bistability and related hysteresis between perennial <span class="hlt">ice</span> and perennial open water for varying atmospheric heat influx. Seasonal <span class="hlt">ice</span> <span class="hlt">cover</span> exists as a transient phenomenon. We also find that ocean heat fluxes are more efficient than atmospheric heat fluxes to melt Arctic sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMIN24A..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMIN24A..06H"><span>Hyperparameter Classification of Arctic Sea <span class="hlt">Ice</span> and Snow <span class="hlt">Based</span> on Aerial Laser Data, Passive Microwave Data and Field Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herzfeld, U. C.; Maslanik, J.; Williams, S.; Sturm, M.; Cavalieri, D.</p> <p>2006-12-01</p> <p>In the past year, the Arctic sea-<span class="hlt">ice</span> <span class="hlt">cover</span> has been shrinking at an alarming rate. Remote-sensing technologies provide opportunities for observations of the sea <span class="hlt">ice</span> at unprecedented repetition rates and spatial resolutions. The advance of new observational technologies is not only fascinating, it also brings with it the challenge and necessity to derive adequate new geoinformatical and geomathematical methods as a basis for analysis and geophysical interpretation of new data types. Our research includes validation and analysis of NASA EOS data, development of observational instrumentation and advanced geoinformatics. In this talk we emphasize the close linkage between technological development and geoinformatics along case studies of sea-<span class="hlt">ice</span> near Point Barrow, Alaska, <span class="hlt">based</span> on the following data types: AMSR-E and PSR passive microwave data, RADARSAT and ERS SAR data, manually-collected snow-depth data and laser-elevation data from unmanned aerial vehicles. The hyperparameter concept is introduced to facilitate characterization and classification of the same sea-<span class="hlt">ice</span> properties and spatial structures from these data sets, which differ with respect to spatial resolution, measured parameters and observed geophysical variables. Mathematically, this requires parameter identification in undersampled, oversampled or overprinted situations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5324094','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5324094"><span>Variability in sea <span class="hlt">ice</span> <span class="hlt">cover</span> and climate elicit sex specific responses in an Antarctic predator</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Rob A.; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit</p> <p>2017-01-01</p> <p>Contrasting regional changes in Southern Ocean sea <span class="hlt">ice</span> have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea <span class="hlt">ice</span> concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack <span class="hlt">ice</span> in years with greatest sea <span class="hlt">ice</span> concentration and earliest sea <span class="hlt">ice</span> advance, while males foraged longer in polynyas in years of lowest sea <span class="hlt">ice</span> concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea <span class="hlt">ice</span> property and dynamic anomalies. PMID:28233791</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28233791','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28233791"><span>Variability in sea <span class="hlt">ice</span> <span class="hlt">cover</span> and climate elicit sex specific responses in an Antarctic predator.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D; Massom, Rob A; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A; Charrassin, Jean-Benoit</p> <p>2017-02-24</p> <p>Contrasting regional changes in Southern Ocean sea <span class="hlt">ice</span> have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea <span class="hlt">ice</span> concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack <span class="hlt">ice</span> in years with greatest sea <span class="hlt">ice</span> concentration and earliest sea <span class="hlt">ice</span> advance, while males foraged longer in polynyas in years of lowest sea <span class="hlt">ice</span> concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea <span class="hlt">ice</span> property and dynamic anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28505135','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28505135"><span>Sea <span class="hlt">Ice</span> Detection <span class="hlt">Based</span> on an Improved Similarity Measurement Method Using Hyperspectral Data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Han, Yanling; Li, Jue; Zhang, Yun; Hong, Zhonghua; Wang, Jing</p> <p>2017-05-15</p> <p>Hyperspectral remote sensing technology can acquire nearly continuous spectrum information and rich sea <span class="hlt">ice</span> image information, thus providing an important means of sea <span class="hlt">ice</span> detection. However, the correlation and redundancy among hyperspectral bands reduce the accuracy of traditional sea <span class="hlt">ice</span> detection methods. <span class="hlt">Based</span> on the spectral characteristics of sea <span class="hlt">ice</span>, this study presents an improved similarity measurement method <span class="hlt">based</span> on linear prediction (ISMLP) to detect sea <span class="hlt">ice</span>. First, the first original band with a large amount of information is determined <span class="hlt">based</span> on mutual information theory. Subsequently, a second original band with the least similarity is chosen by the spectral correlation measuring method. Finally, subsequent bands are selected through the linear prediction method, and a support vector machine classifier model is applied to classify sea <span class="hlt">ice</span>. In experiments performed on images of Baffin Bay and Bohai Bay, comparative analyses were conducted to compare the proposed method and traditional sea <span class="hlt">ice</span> detection methods. Our proposed ISMLP method achieved the highest classification accuracies (91.18% and 94.22%) in both experiments. From these results the ISMLP method exhibits better performance overall than other methods and can be effectively applied to hyperspectral sea <span class="hlt">ice</span> detection.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5470800','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5470800"><span>Sea <span class="hlt">Ice</span> Detection <span class="hlt">Based</span> on an Improved Similarity Measurement Method Using Hyperspectral Data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Han, Yanling; Li, Jue; Zhang, Yun; Hong, Zhonghua; Wang, Jing</p> <p>2017-01-01</p> <p>Hyperspectral remote sensing technology can acquire nearly continuous spectrum information and rich sea <span class="hlt">ice</span> image information, thus providing an important means of sea <span class="hlt">ice</span> detection. However, the correlation and redundancy among hyperspectral bands reduce the accuracy of traditional sea <span class="hlt">ice</span> detection methods. <span class="hlt">Based</span> on the spectral characteristics of sea <span class="hlt">ice</span>, this study presents an improved similarity measurement method <span class="hlt">based</span> on linear prediction (ISMLP) to detect sea <span class="hlt">ice</span>. First, the first original band with a large amount of information is determined <span class="hlt">based</span> on mutual information theory. Subsequently, a second original band with the least similarity is chosen by the spectral correlation measuring method. Finally, subsequent bands are selected through the linear prediction method, and a support vector machine classifier model is applied to classify sea <span class="hlt">ice</span>. In experiments performed on images of Baffin Bay and Bohai Bay, comparative analyses were conducted to compare the proposed method and traditional sea <span class="hlt">ice</span> detection methods. Our proposed ISMLP method achieved the highest classification accuracies (91.18% and 94.22%) in both experiments. From these results the ISMLP method exhibits better performance overall than other methods and can be effectively applied to hyperspectral sea <span class="hlt">ice</span> detection. PMID:28505135</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26213674','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26213674"><span>On the nature of the sea <span class="hlt">ice</span> albedo feedback in simple models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moon, W; Wettlaufer, J S</p> <p>2014-08-01</p> <p>We examine the nature of the <span class="hlt">ice</span>-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea <span class="hlt">ice</span>. The central issue examined is how the evolution of the <span class="hlt">ice</span> area is treated when modeling a partial <span class="hlt">ice</span> <span class="hlt">cover</span> using a two-category-thickness scheme; thin sea <span class="hlt">ice</span> and open water in one category and "thick" sea <span class="hlt">ice</span> in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional <span class="hlt">ice</span> <span class="hlt">cover</span> and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying <span class="hlt">ice</span> <span class="hlt">cover</span> approaching the transitions to seasonal or <span class="hlt">ice</span>-free conditions. Clearly, a mishandling of the evolution of the <span class="hlt">ice</span> area has leading-order effects on the <span class="hlt">ice</span>-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea <span class="hlt">ice</span> thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4508964','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4508964"><span>On the nature of the sea <span class="hlt">ice</span> albedo feedback in simple models</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moon, W; Wettlaufer, J S</p> <p>2014-01-01</p> <p>We examine the nature of the <span class="hlt">ice</span>-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea <span class="hlt">ice</span>. The central issue examined is how the evolution of the <span class="hlt">ice</span> area is treated when modeling a partial <span class="hlt">ice</span> <span class="hlt">cover</span> using a two-category-thickness scheme; thin sea <span class="hlt">ice</span> and open water in one category and “thick” sea <span class="hlt">ice</span> in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional <span class="hlt">ice</span> <span class="hlt">cover</span> and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying <span class="hlt">ice</span> <span class="hlt">cover</span> approaching the transitions to seasonal or <span class="hlt">ice</span>-free conditions. Clearly, a mishandling of the evolution of the <span class="hlt">ice</span> area has leading-order effects on the <span class="hlt">ice</span>-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea <span class="hlt">ice</span> thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe. PMID:26213674</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDM29002R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDM29002R"><span>Forced convective melting at an evolving <span class="hlt">ice</span>-water interface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramudu, Eshwan; Hirsh, Benjamin; Olson, Peter; Gnanadesikan, Anand</p> <p>2015-11-01</p> <p>The intrusion of warm Circumpolar Deep Water into the ocean cavity between the <span class="hlt">base</span> of <span class="hlt">ice</span> shelves and the sea bed in Antarctica causes melting at the <span class="hlt">ice</span> shelves' basal surface, producing a turbulent melt plume. We conduct a series of laboratory experiments to investigate how the presence of forced convection (turbulent mixing) changes the delivery of heat to the <span class="hlt">ice</span>-water interface. We also develop a theoretical model for the heat balance of the system that can be used to predict the change in <span class="hlt">ice</span> thickness with time. In cases of turbulent mixing, the heat balance includes a term for turbulent heat transfer that depends on the friction velocity and an empirical coefficient. We obtain a new value for this coefficient by comparing the modeled <span class="hlt">ice</span> thickness against measurements from a set of nine experiments <span class="hlt">covering</span> one order of magnitude of Reynolds numbers. Our results are consistent with the altimetry-inferred melting rate under Antarctic <span class="hlt">ice</span> shelves and can be used in climate models to predict their disintegration. This work was supported by NSF grant EAR-110371.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27145844','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27145844"><span><span class="hlt">Ice</span>-Binding Proteins and Their Function.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bar Dolev, Maya; Braslavsky, Ido; Davies, Peter L</p> <p>2016-06-02</p> <p><span class="hlt">Ice</span>-binding proteins (IBPs) are a diverse class of proteins that assist organism survival in the presence of <span class="hlt">ice</span> in cold climates. They have different origins in many organisms, including bacteria, fungi, algae, diatoms, plants, insects, and fish. This review <span class="hlt">covers</span> the gamut of IBP structures and functions and the common features they use to bind <span class="hlt">ice</span>. We discuss mechanisms by which IBPs adsorb to <span class="hlt">ice</span> and interfere with its growth, evidence for their irreversible association with <span class="hlt">ice</span>, and methods for enhancing the activity of IBPs. The applications of IBPs in the food industry, in cryopreservation, and in other technologies are vast, and we chart out some possibilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27650478','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27650478"><span>Canadian Arctic sea <span class="hlt">ice</span> reconstructed from bromine in the Greenland NEEM <span class="hlt">ice</span> core.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Spolaor, Andrea; Vallelonga, Paul; Turetta, Clara; Maffezzoli, Niccolò; Cozzi, Giulio; Gabrieli, Jacopo; Barbante, Carlo; Goto-Azuma, Kumiko; Saiz-Lopez, Alfonso; Cuevas, Carlos A; Dahl-Jensen, Dorthe</p> <p>2016-09-21</p> <p>Reconstructing the past variability of Arctic sea <span class="hlt">ice</span> provides an essential context for recent multi-year sea <span class="hlt">ice</span> decline, although few quantitative reconstructions <span class="hlt">cover</span> the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea <span class="hlt">ice</span> in so-called "bromine explosions" and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea <span class="hlt">ice</span> and depositional transport over multi-year sea <span class="hlt">ice</span> and land <span class="hlt">ice</span>. We report bromine enrichment in the Northwest Greenland Eemian NEEM <span class="hlt">ice</span> core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea <span class="hlt">ice</span> occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea <span class="hlt">ice</span> extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea <span class="hlt">ice</span>. These findings demonstrate a clear relationship between temperature and first-year sea <span class="hlt">ice</span> extent in the Arctic and suggest multi-year sea <span class="hlt">ice</span> will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/1000536','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/1000536"><span>ROV dives under Great Lakes <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bolsenga, S.J.; Gannon, John E.; Kennedy, Gregory; Norton, D.C.; Herdendorf, Charles E.</p> <p>1989-01-01</p> <p>Observations of the underside of <span class="hlt">ice</span> have a wide variety of applications. Severe under-<span class="hlt">ice</span> roughness can affect <span class="hlt">ice</span> movements, rough under-<span class="hlt">ice</span> surfaces can scour the bottom disturbing biota and man-made structures such as pipelines, and the flow rate of rivers is often affected by under-<span class="hlt">ice</span> roughness. A few reported observations of the underside of an <span class="hlt">ice</span> <span class="hlt">cover</span> have been made, usually by cutting a large block of <span class="hlt">ice</span> and overturning it, by extensive boring, or by remote sensing. Such operations are extremely labor-intensive and, in some cases, prone to inaccuracies. Remotely operated vehicles (ROV) can partially solve these problems. In this note, we describe the use, performance in a hostile environment, and results of a study in which a ROV was deployed under the <span class="hlt">ice</span> in Lake Erie (North American Great Lakes).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121..674K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121..674K"><span>Sea surface height and dynamic topography of the <span class="hlt">ice-covered</span> oceans from CryoSat-2: 2011-2014</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kwok, Ron; Morison, James</p> <p>2016-01-01</p> <p>We examine 4 years (2011-2014) of sea surface heights (SSH) from CryoSat-2 (CS-2) over the <span class="hlt">ice-covered</span> Arctic and Southern Oceans. Results are from a procedure that identifies and determines the heights of sea surface returns. Along 25 km segments of satellite ground tracks, variability in the retrieved SSHs is between ˜2 and 3 cm (standard deviation) in the Arctic and is slightly higher (˜3 cm) in the summer and the Southern Ocean. Average sea surface tilts (along these 25 km segments) are 0.01 ± 3.8 cm/10 km in the Arctic, and slightly lower (0.01 ± 2.0 cm/10 km) in the Southern Ocean. Intra-seasonal variability of CS-2 dynamic ocean topography (DOT) in the <span class="hlt">ice-covered</span> Arctic is nearly twice as high as that of the Southern Ocean. In the Arctic, we find a correlation of 0.92 between 3 years of DOT and dynamic heights (DH) from hydrographic stations. Further, correlation of 4 years of area-averaged CS-2 DOT near the North Pole with time-variable ocean-bottom pressure from a pressure gauge and from GRACE, yields coefficients of 0.83 and 0.77, with corresponding differences of <3 cm (RMS). These comparisons contrast the length scale of baroclinic and barotropic features and reveal the smaller amplitude barotropic signals in the Arctic Ocean. Broadly, the mean DOT from CS-2 for both poles compares well with those from the ICESat campaigns and the DOT2008A and DTU13MDT fields. Short length scale topographic variations, due to oceanographic signals and geoid residuals, are especially prominent in the Arctic Basin but less so in the Southern Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000038122&hterms=modis+snow+cover&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodis%2Bsnow%2Bcover','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000038122&hterms=modis+snow+cover&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodis%2Bsnow%2Bcover"><span>MODIS Snow and <span class="hlt">Ice</span> Products from the NSIDC DAAC</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scharfen, Greg R.; Hall, Dorothy K.; Riggs, George A.</p> <p>1997-01-01</p> <p>The National Snow and <span class="hlt">Ice</span> Data Center (NSIDC) Distributed Active Archive Center (DAAC) provides data and information on snow and <span class="hlt">ice</span> processes, especially pertaining to interactions among snow, <span class="hlt">ice</span>, atmosphere and ocean, in support of research on global change detection and model validation, and provides general data and information services to cryospheric and polar processes research community. The NSIDC DAAC is an integral part of the multi-agency-funded support for snow and <span class="hlt">ice</span> data management services at NSIDC. The Moderate Resolution Imaging Spectroradiometer (MODIS) will be flown on the first Earth Observation System (EOS) platform (AM-1) in 1998. The MODIS Instrument Science Team is developing geophysical products from data collected by the MODIS instrument, including snow and <span class="hlt">ice</span> products which will be archived and distributed by NSIDC DAAC. The MODIS snow and <span class="hlt">ice</span> mapping algorithms will generate global snow, lake <span class="hlt">ice</span>, and sea <span class="hlt">ice</span> <span class="hlt">cover</span> products on a daily basis. These products will augment the existing record of satellite-derived snow <span class="hlt">cover</span> and sea <span class="hlt">ice</span> products that began about 30 years ago. The characteristics of these products, their utility, and comparisons to other data set are discussed. Current developments and issues are summarized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C41A0504B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C41A0504B"><span>Managing <span class="hlt">Ice</span>Bridge Airborne Mission Data at the National Snow and <span class="hlt">Ice</span> Data Center</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brodzik, M.; Kaminski, M. L.; Deems, J. S.; Scambos, T. A.</p> <p>2010-12-01</p> <p> a map-<span class="hlt">based</span> interface. This portal will provide flight line rendering and multi-instrument data previewing capabilities to facilitate use of the wide array of data types, resolutions, and configurations in this dynamic airborne mission. Together with the <span class="hlt">Ice</span>Bridge Science Team and <span class="hlt">Ice</span> Bridge Science Working Groups, NSIDC is generating value-added products from the <span class="hlt">Ice</span> Bridge data streams and other ancillary data. These products will provide simple, useful combinations of <span class="hlt">Ice</span> Bridge products and regional maps of important geophysical parameters from other sources. Planned value-added products include: (1) gridded products in which new profiles from <span class="hlt">Ice</span> Bridge (e.g. elevation or <span class="hlt">ice</span> thickness) are combined with existing DEMs or bed maps to produce revised grids and (2) flight-profile multi-instrument products in which data from several instruments are combined into <span class="hlt">ice</span> sheet profiles (surface elevation, <span class="hlt">ice</span> thickness, internal reflection data, bed reflection intensity, and gravimetry), sea <span class="hlt">ice</span> profiles (freeboard, snow <span class="hlt">cover</span>, and thickness), and surface data profiles (elevation, slope, roughness, near-surface layering, and imagery).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721118','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721118"><span>Diatom assemblages promote <span class="hlt">ice</span> formation in large lakes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L</p> <p>2013-01-01</p> <p>We present evidence for the directed formation of <span class="hlt">ice</span> by planktonic communities dominated by filamentous diatoms sampled from the <span class="hlt">ice-covered</span> Laurentian Great Lakes. We hypothesize that <span class="hlt">ice</span> formation promotes attachment of these non-motile phytoplankton to overlying <span class="hlt">ice</span>, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for <span class="hlt">ice</span> nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (Tc) as high as −3 °C. <span class="hlt">Ice</span> nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of <span class="hlt">ice</span> nucleation activity, the resulting production of frazil <span class="hlt">ice</span> may provide a means for the diatoms to be recruited to the overlying lake <span class="hlt">ice</span>, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal <span class="hlt">ice</span> <span class="hlt">cover</span> around the world. PMID:23552624</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850053020&hterms=helicopter+sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhelicopter%2Bsea','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850053020&hterms=helicopter+sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhelicopter%2Bsea"><span>Active microwave measurements of Arctic sea <span class="hlt">ice</span> under summer conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Onstott, R. G.; Gogineni, S. P.</p> <p>1985-01-01</p> <p>Radar provides a valuable tool in the study of sea-<span class="hlt">ice</span> conditions and the solution of sea-<span class="hlt">ice</span> operational problems. For this reason, the U.S. and Canada have conducted studies to define a bilateral synthetic aperture radar (SAR) satellite program. The present paper is concerned with work which has been performed to explore the needs associated with the study of sea-<span class="hlt">ice-covered</span> waters. The design of a suitable research or operational spaceborne SAR or real aperture radar must be <span class="hlt">based</span> on an adequate knowledge of the backscatter coefficients of the <span class="hlt">ice</span> features which are of interest. In order to obtain the needed information, studies involving the use of a helicopter were conducted. In these studies L-C-X-Ku-band calibrated radar data were acquired over areas of Arctic first-year and multiyear <span class="hlt">ice</span> during the first half of the summer of 1982. The results show that the microwave response in the case of sea <span class="hlt">ice</span> is greatly influenced by summer melt, which produces significant changes in the properties of the snowpack and <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860050945&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860050945&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>Aircraft and satellite passive microwave observations of the Bering Sea <span class="hlt">ice</span> <span class="hlt">cover</span> during MIZEX West</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, D. J.; Gloersen, P.; Wilheit, T. T., Jr.</p> <p>1986-01-01</p> <p>Passive microwave measurements of the Bering Sea were made with the NASA CV-990 airborne laboratory during February. Microwave data were obtained with imaging and dual-polarized, fixed-beam radiometers in a range of frequencies from 10 to 183 GHz. The high resolution imagery at 92 GHz provides a particularly good description of the marginal <span class="hlt">ice</span> zone delineating regions of open water, <span class="hlt">ice</span> compactness, and <span class="hlt">ice</span>-edge structure. Analysis of the fixed-beam data shows that spectral differences increase with a decrease in <span class="hlt">ice</span> thickness. Polarization at 18 and 37 GHz distinguishes among new, young, and first-year <span class="hlt">ice</span> types.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050185661','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050185661"><span>Sea <span class="hlt">Ice</span> Kinematics and Thickness from RGPS: Observations and Theory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stern, Harry; Lindsay, Ron; Yu, Yan-Ling; Moritz, Richard; Rothrock, Drew</p> <p>2005-01-01</p> <p>The RADARSAT Geophysical Processor System (RGPS) has produced a wealth of data on Arctic sea <span class="hlt">ice</span> motion, deformation, and thickness with broad geographical coverage and good temporal resolution. These data provide unprecedented spatial detail of the structure and evolution of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. The broad purpose of this study was to take advantage of the strengths of the RGPS data set to investigate sea <span class="hlt">ice</span> kinematics and thickness, which affect the climate through their influence on <span class="hlt">ice</span> production, ridging, and transport (i.e. mass balance); heat flux to the atmosphere; and structure of the upper ocean mixed layer. The objectives of this study were to: (1) Explain the relationship between the discontinuous motion of the <span class="hlt">ice</span> <span class="hlt">cover</span> and the large-scale, smooth wind field that drives the <span class="hlt">ice</span>; (2) Characterize the sea <span class="hlt">ice</span> deformation in the Arctic at different temporal and spatial scales, and compare it with deformation predicted by a state-of-theart <span class="hlt">ice</span>/ocean model; and (3) Compare RGPS-derived sea <span class="hlt">ice</span> thickness with other data, and investigate the thinning of the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> as seen in ULS data obtained by U.S. Navy submarines. We briefly review the results of our work below, separated into the topics of sea <span class="hlt">ice</span> deformation and sea <span class="hlt">ice</span> thickness. This is followed by a list of publications, meetings and presentations, and other activities supported under this grant. We are attaching to this report copies of all the listed publications. Finally, we would like to point out our community service to NASA through our involvement with the ASF User Working Group and the RGPS Science Working Group, as evidenced in the list of meetings and presentations below.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26553610','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26553610"><span>Methane excess in Arctic surface water-triggered by sea <span class="hlt">ice</span> formation and melting.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Damm, E; Rudels, B; Schauer, U; Mau, S; Dieckmann, G</p> <p>2015-11-10</p> <p>Arctic amplification of global warming has led to increased summer sea <span class="hlt">ice</span> retreat, which influences gas exchange between the Arctic Ocean and the atmosphere where sea <span class="hlt">ice</span> previously acted as a physical barrier. Indeed, recently observed enhanced atmospheric methane concentrations in Arctic regions with fractional sea-<span class="hlt">ice</span> <span class="hlt">cover</span> point to unexpected feedbacks in cycling of methane. We report on methane excess in sea <span class="hlt">ice</span>-influenced water masses in the interior Arctic Ocean and provide evidence that sea <span class="hlt">ice</span> is a potential source. We show that methane release from sea <span class="hlt">ice</span> into the ocean occurs via brine drainage during freezing and melting i.e. in winter and spring. In summer under a fractional sea <span class="hlt">ice</span> <span class="hlt">cover</span>, reduced turbulence restricts gas transfer, then seawater acts as buffer in which methane remains entrained. However, in autumn and winter surface convection initiates pronounced efflux of methane from the <span class="hlt">ice</span> <span class="hlt">covered</span> ocean to the atmosphere. Our results demonstrate that sea <span class="hlt">ice</span>-sourced methane cycles seasonally between sea <span class="hlt">ice</span>, sea-<span class="hlt">ice</span>-influenced seawater and the atmosphere, while the deeper ocean remains decoupled. Freshening due to summer sea <span class="hlt">ice</span> retreat will enhance this decoupling, which restricts the capacity of the deeper Arctic Ocean to act as a sink for this greenhouse gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51C0999X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51C0999X"><span>Snowmelt Pattern and Lake <span class="hlt">Ice</span> Phenology around Tibetan Plateau Estimated from Enhanced Resolution Passive Microwave Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, C.; Shi, J.; Wang, T.</p> <p>2017-12-01</p> <p>Snow and <span class="hlt">ice</span> is very sensitive to the climate change. Rising air temperature will cause the snowmelt time change. In contrast, the change in snow state will have feedback on climate through snow albedo. The snow melt timing is also correlated with the associated runoff. <span class="hlt">Ice</span> phenology describes the seasonal cycle of lake <span class="hlt">ice</span> <span class="hlt">cover</span> and includes freeze-up and breakup periods and <span class="hlt">ice</span> <span class="hlt">cover</span> duration, which is an important weather and climate indicator. It is also important for lake-atmosphere interactions and hydrological and ecological processes. The enhanced resolution (up to 3.125 km) passive microwave data is used to estimate the snowmelt pattern and lake <span class="hlt">ice</span> phenology on and around Tibetan Plateau. The enhanced resolution makes the estimation of snowmelt and lake <span class="hlt">ice</span> phenology in more spatial detail compared to previous 25 km gridded passive microwave data. New algorithm <span class="hlt">based</span> on smooth filters and change point detection was developed to estimate the snowmelt and lake <span class="hlt">ice</span> freeze-up and break-up timing. Spatial and temporal pattern of snowmelt and lake <span class="hlt">ice</span> phonology are estimated. This study provides an objective evidence of climate change impact on the cryospheric system on Tibetan Plateau. The results show significant earlier snowmelt and lake <span class="hlt">ice</span> break-up in some regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1511771L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1511771L"><span>The northern Uummannaq <span class="hlt">Ice</span> Stream System, West Greenland: <span class="hlt">ice</span> dynamics and and controls upon deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lane, Timothy; Roberts, David; Rea, Brice; Cofaigh, Colm Ó.; Vieli, Andreas</p> <p>2013-04-01</p> <p>At the Last Glacial Maximum (LGM), the Uummannaq <span class="hlt">Ice</span> Stream System comprised a series coalescent outlet glaciers which extended along the trough to the shelf edge, draining a large proportion of the West Greenland <span class="hlt">Ice</span> Sheet. Geomorphological mapping, terrestrial cosmogenic nuclide (TCN) exposure dating, and radiocarbon dating constrain warm-<span class="hlt">based</span> <span class="hlt">ice</span> stream activity in the north of the system to 1400 m a.s.l. during the LGM. Intervening plateaux areas (~ 2000 m a.s.l.) either remained <span class="hlt">ice</span> free, or were <span class="hlt">covered</span> by cold-<span class="hlt">based</span> icefields, preventing diffluent or confluent flow throughout the inner to outer fjord region. Beyond the fjords, a topographic sill north of Ubekendt Ejland prevented the majority of westward <span class="hlt">ice</span> flow, forcing it south through Igdlorssuit Sund, and into the Uummannaq Trough. Here it coalesced with <span class="hlt">ice</span> from the south, forming the trunk zone of the UISS. Deglaciation of the UISS began at 14.9 cal. ka BP, rapidly retreating through the overdeepened Uummannaq Trough. Once beyond Ubekendt Ejland, the northern UISS retreated northwards, separating from the south. Retreat continued, and <span class="hlt">ice</span> reached the present fjord confines in northern Uummannaq by 11.6 kyr. Both geomorphological (termino-lateral moraines) and geochronological (14C and TCN) data provide evidence for an <span class="hlt">ice</span> marginal stabilisation at within Karrat-Rink Fjord, at Karrat Island, from 11.6-6.9 kyr. The Karrat moraines appear similar in both fjord position and form to 'Fjord Stade' moraines identified throughout West Greenland. Though chronologies constraining moraine formation are overlapping (Fjord Stade moraines - 9.3-8.2 kyr, Karrat moraines - 11.6-6.9 kyr), these moraines have not been correlated. This <span class="hlt">ice</span> margin stabilisation was able to persist during the Holocene Thermal Maximum (~7.2 - 5 kyr). It overrode climatic and oceanic forcings, remaining on Karrat Island throughout peaks of air temperature and relative sea-level, and during the influx of the warm West Greenland Current into</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8907S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8907S"><span>Toward a Lake <span class="hlt">Ice</span> Phenology Derived from VIIRS Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sütterlin, Melanie; Duguay-Tetzlaff, Anke; Wunderle, Stefan</p> <p>2017-04-01</p> <p><span class="hlt">Ice</span> <span class="hlt">cover</span> on lakes plays an essential role in the physical, chemical, and biological processes of freshwater systems (e.g., <span class="hlt">ice</span> duration controls the seasonal heat budget of lakes), and it also has many economic implications (e.g., for hydroelectricity, transportation, winter tourism). The variability and trends in the seasonal cycle of lake <span class="hlt">ice</span> (e.g., timing of freeze-up and break-up) represent robust and direct indicators of climate change; they therefore emphasize the importance of monitoring lake <span class="hlt">ice</span> phenology. Satellite remote sensing has proven its great potential for detecting and measuring the <span class="hlt">ice</span> <span class="hlt">cover</span> on lakes. Different remote sensing systems have been successfully used to collect recordings of freeze-up, break-up, and <span class="hlt">ice</span> thickness and increase the spatial and temporal coverage of ground-<span class="hlt">based</span> observations. Therefore, within the Global Climate Observing System (GCOS) Swiss project, "Integrated Monitoring of <span class="hlt">Ice</span> in Selected Swiss Lakes," initiated by MeteoSwiss, satellite images from various sensors and different approaches are used and compared to perform investigations aimed at integrated monitoring of lake <span class="hlt">ice</span> in Switzerland and contributing to the collection of lake <span class="hlt">ice</span> phenology recordings. Within the framework of this project, the Remote Sensing Research Group of the University of Bern (RSGB) utilizes data acquired in the fine-resolution imagery (I) bands (1-5) of the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor that is mounted onboard the SUOMI-NPP. Visible and near-infrared reflectances, as well as thermal infrared-derived lake surface water temperatures (LSWT), are used to retrieve lake <span class="hlt">ice</span> phenology dates. The VIIRS instrument, which combines a high temporal resolution ( 2 times per day) with a reasonable spatial resolution (375 m), is equipped with a single broad-band thermal I-channel (I05). Thus, a single-channel LSWT retrieval algorithm is employed to correct for the atmospheric influence. The single channel algorithm applied in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33B1193M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33B1193M"><span>Cloud Response to Arctic Sea <span class="hlt">Ice</span> Loss and Implications for Feedbacks in the CESM1 Climate Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morrison, A.; Kay, J. E.; Chepfer, H.; Guzman, R.; Bonazzola, M.</p> <p>2017-12-01</p> <p>Clouds have the potential to accelerate or slow the rate of Arctic sea <span class="hlt">ice</span> loss through their radiative influence on the surface. Cloud feedbacks can therefore play into Arctic warming as clouds respond to changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span>. As the Arctic moves toward an <span class="hlt">ice</span>-free state, understanding how cloud - sea <span class="hlt">ice</span> relationships change in response to sea <span class="hlt">ice</span> loss is critical for predicting the future climate trajectory. From satellite observations we know the effect of present-day sea <span class="hlt">ice</span> <span class="hlt">cover</span> on clouds, but how will clouds respond to sea <span class="hlt">ice</span> loss as the Arctic transitions to a seasonally open water state? In this study we use a lidar simulator to first evaluate cloud - sea <span class="hlt">ice</span> relationships in the Community Earth System Model (CESM1) against present-day observations (2006-2015). In the current climate, the cloud response to sea <span class="hlt">ice</span> is well-represented in CESM1: we see no summer cloud response to changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span>, but more fall clouds over open water than over sea <span class="hlt">ice</span>. Since CESM1 is credible for the current Arctic climate, we next assess if our process-<span class="hlt">based</span> understanding of Arctic cloud feedbacks related to sea <span class="hlt">ice</span> loss is relevant for understanding future Arctic clouds. In the future Arctic, summer cloud structure continues to be insensitive to surface conditions. As the Arctic warms in the fall, however, the boundary layer deepens and cloud fraction increases over open ocean during each consecutive decade from 2020 - 2100. This study will also explore seasonal changes in cloud properties such as opacity and liquid water path. Results thus far suggest that a positive fall cloud - sea <span class="hlt">ice</span> feedback exists in the present-day and future Arctic climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171197','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171197"><span>MODIS Snow and Sea <span class="hlt">Ice</span> Products</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.</p> <p>2004-01-01</p> <p>In this chapter, we describe the suite of Earth Observing System (EOS) Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow and sea <span class="hlt">ice</span> products. Global, daily products, developed at Goddard Space Flight Center, are archived and distributed through the National Snow and <span class="hlt">Ice</span> Data Center at various resolutions and on different grids useful for different communities Snow products include binary snow <span class="hlt">cover</span>, snow albedo, and in the near future, fraction of snow in a 5OO-m pixel. Sea <span class="hlt">ice</span> products include <span class="hlt">ice</span> extent determined with two different algorithms, and sea <span class="hlt">ice</span> surface temperature. The algorithms used to develop these products are described. Both the snow and sea <span class="hlt">ice</span> products, available since February 24,2000, are useful for modelers. Validation of the products is also discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0800H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0800H"><span>Landcover Mapping of the McMurdo <span class="hlt">Ice</span> Shelf Using Landsat and WorldView Image Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hansen, E. K.; Macdonald, G.; Mayer, D. P.; MacAyeal, D. R.</p> <p>2016-12-01</p> <p><span class="hlt">Ice</span> shelves bound approximately half of the Antarctic coast and act to buttress the glaciers that feed them. The collapse of the Larsen B <span class="hlt">Ice</span> Shelf on the Antarctic Peninsula highlights the importance of processes at the surface for an <span class="hlt">ice</span> shelf's stability. The McMurdo <span class="hlt">Ice</span> Shelf is unique among Antarctic <span class="hlt">ice</span> shelves in that it exists in a relatively warm climate zone and is thus more vulnerable to climate change than colder <span class="hlt">ice</span> shelves at similar latitudes. However, little is known quantitatively about the surface <span class="hlt">cover</span> types across the <span class="hlt">ice</span> shelf, impeding the study of its hydrology and of the origins of its features. In particular, no work has been done linking field observations of supraglacial channels to shelf-wide surface hydrology. We will present the first satellite-derived multiscale landcover map of the McMurdo <span class="hlt">Ice</span> Shelf <span class="hlt">based</span> on Landsat 8 and WorldView-2 image data. Landcover types are extracted using supervised classification methods referenced to field observations. Landsat 8 provides coverage of the entire <span class="hlt">ice</span> shelf ( 5,000 km2) at 30 m/pixel, sufficient to distinguish glacial <span class="hlt">ice</span>, debris <span class="hlt">cover</span>, and large supraglacial lakes. WorldView data <span class="hlt">cover</span> a smaller area— 300 km2 at 2 m/pixel—and thus allow detailed mapping of features that are not spatially resolved by Landsat, such as supraglacial channels and small fractures across the <span class="hlt">ice</span> shelf's surface. We take advantage of the higher resolution of WorldView-2 data to calculate the area of mid-summer surface water in channels and melt ponds within a detailed study area and use this as the basis for a spectral mixture model in order to estimate the total surface water area across the <span class="hlt">ice</span> shelf. We intend to use the maps to guide strategic planning of future field research into the seasonal surface hydrology and climate stability of the McMurdo <span class="hlt">Ice</span> Shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70040729','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70040729"><span>The impact of lower sea-<span class="hlt">ice</span> extent on Arctic greenhouse-gas exchange</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Parmentier, Frans-Jan W.; Christensen, Torben R.; Sørensen, Lise Lotte; Rysgaard, Søren; McGuire, A. David; Miller, Paul A.; Walker, Donald A.</p> <p>2013-01-01</p> <p>In September 2012, Arctic sea-<span class="hlt">ice</span> extent plummeted to a new record low: two times lower than the 1979–2000 average. Often, record lows in sea-<span class="hlt">ice</span> <span class="hlt">cover</span> are hailed as an example of climate change impacts in the Arctic. Less apparent, however, are the implications of reduced sea-<span class="hlt">ice</span> <span class="hlt">cover</span> in the Arctic Ocean for marine–atmosphere CO2 exchange. Sea-<span class="hlt">ice</span> decline has been connected to increasing air temperatures at high latitudes. Temperature is a key controlling factor in the terrestrial exchange of CO2 and methane, and therefore the greenhouse-gas balance of the Arctic. Despite the large potential for feedbacks, many studies do not connect the diminishing sea-<span class="hlt">ice</span> extent with changes in the interaction of the marine and terrestrial Arctic with the atmosphere. In this Review, we assess how current understanding of the Arctic Ocean and high-latitude ecosystems can be used to predict the impact of a lower sea-<span class="hlt">ice</span> <span class="hlt">cover</span> on Arctic greenhouse-gas exchange.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..365R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..365R"><span>Consistent biases in Antarctic sea <span class="hlt">ice</span> concentration simulated by climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roach, Lettie A.; Dean, Samuel M.; Renwick, James A.</p> <p>2018-01-01</p> <p>The simulation of Antarctic sea <span class="hlt">ice</span> in global climate models often does not agree with observations. In this study, we examine the compactness of sea <span class="hlt">ice</span>, as well as the regional distribution of sea <span class="hlt">ice</span> concentration, in climate models from the latest Coupled Model Intercomparison Project (CMIP5) and in satellite observations. We find substantial differences in concentration values between different sets of satellite observations, particularly at high concentrations, requiring careful treatment when comparing to models. As a fraction of total sea <span class="hlt">ice</span> extent, models simulate too much loose, low-concentration sea <span class="hlt">ice</span> <span class="hlt">cover</span> throughout the year, and too little compact, high-concentration <span class="hlt">cover</span> in the summer. In spite of the differences in physics between models, these tendencies are broadly consistent across the population of 40 CMIP5 simulations, a result not previously highlighted. Separating models with and without an explicit lateral melt term, we find that inclusion of lateral melt may account for overestimation of low-concentration <span class="hlt">cover</span>. Targeted model experiments with a coupled ocean-sea <span class="hlt">ice</span> model show that choice of constant floe diameter in the lateral melt scheme can also impact representation of loose <span class="hlt">ice</span>. This suggests that current sea <span class="hlt">ice</span> thermodynamics contribute to the inadequate simulation of the low-concentration regime in many models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP33A2279P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP33A2279P"><span>Initial Insights into the Quaternary Evolution of the Laurentide <span class="hlt">Ice</span> Sheet on Southeastern Baffin Island</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pendleton, S.; Anderson, R. S.; Miller, G. H.; Refsnider, K. A.</p> <p>2015-12-01</p> <p>Increasing Arctic summer temperatures in recent decades and shrinking cold-<span class="hlt">based</span> <span class="hlt">ice</span> caps on Cumberland Peninsula, Baffin Island, are exposing ancient landscapes complete with uneroded bedrock surfaces. Previous work has indicated that these upland surfaces <span class="hlt">covered</span> with cold-<span class="hlt">based</span> <span class="hlt">ice</span> experience negligible erosion compared with the valleys and fjords systems that contain fast-flowing <span class="hlt">ice</span>. Given the appearance of highly weathered bedrock, it is argued that these landscapes have remained largely unchanged since at least the last interglaciation (~120 ka), and have likely experienced multiple cycles of <span class="hlt">ice</span> expansion and retraction with little erosion throughout the Quaternary. To explore this hypothesis, we use multiple cosmogenic radionuclides (26Al and 10Be) to investigate and provide insight into longer-term cryosphere activity and landscape evolution. 26Al/10Be in surfaces recently exposed exhibit a wide range of exposure-burial histories. Total exposure-burial times range from ~0.3 - 1.5 My and estimated erosion rates from 0.5 - 6.2 m Ma-1. The upland surfaces of the Penny <span class="hlt">Ice</span> cap generally experienced higher erosion rates (~0.45 cm ka-1) than those <span class="hlt">covered</span> by smaller <span class="hlt">ice</span> caps (~0.2 cm ka-1). The cumulative burial/exposure histories in high, fjord-edge locations indicate that significant erosion north of the Penny <span class="hlt">Ice</span> Cap ceased between ~600 and 800 ka, suggesting that Laurentide <span class="hlt">Ice</span> Sheet (LIS) organization and fjord inception was underway by at least this time. Additionally, 26Al/10Be ratios near production values despite high inventories from a coastal summit 50 km east of the Penny <span class="hlt">Ice</span> Cape suggest that that area has not experienced appreciable burial by <span class="hlt">ice</span>, suggesting that it was never inundated by the LIS. Moreover, these initial data suggest a variable and dynamic cryosphere in the region and provide insight into how large <span class="hlt">ice</span> sheets evolved and organized themselves during the Quaternary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PCE....83...75G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PCE....83...75G"><span>Various remote sensing approaches to understanding roughness in the marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gupta, Mukesh</p> <p></p> <p>Multi-platform <span class="hlt">based</span> measurement approaches to understanding complex marginal <span class="hlt">ice</span> zone (MIZ) are suggested in this paper. Physical roughness measurements using ship- and helicopter-<span class="hlt">based</span> laser systems combined with ship-<span class="hlt">based</span> active microwave backscattering (C-band polarimetric coherences) and dual-polarized passive microwave emission (polarization ratio, PR and spectral gradient ratios, GR at 37 and 89 GHz) are presented to study diverse sea <span class="hlt">ice</span> types found in the MIZ. Autocorrelation functions are investigated for different sea <span class="hlt">ice</span> roughness types. Small-scale roughness classes were discriminated using data from a ship-<span class="hlt">based</span> laser profiler. The polarimetric coherence parameter ρHHVH , is not found to exhibit any observable sensitivity to the surface roughness for all incidence angles. Rubble-ridges, pancake <span class="hlt">ice</span>, snow-<span class="hlt">covered</span> frost flowers, and dense frost flowers exhibit separable signatures using GR-H and GR-V at >70° incidence angles. This paper diagnosed changes in sea <span class="hlt">ice</span> roughness on a spatial scale of ∼0.1-4000 m and on a temporal scale of ∼1-240 days (<span class="hlt">ice</span> freeze-up to summer melt). The coupling of MIZ wave roughness and aerodynamic roughness in conjunction with microwave emission and backscattering are future avenues of research. Additionally, the integration of various datasets into thermodynamic evolution model of sea <span class="hlt">ice</span> will open pathways to successful development of inversion models of MIZ behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010403','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010403"><span>Satellite Observations of Antarctic Sea <span class="hlt">Ice</span> Thickness and Volume</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurtz, Nathan; Markus, Thorsten</p> <p>2012-01-01</p> <p>We utilize satellite laser altimetry data from ICESat combined with passive microwave measurements to analyze basin-wide changes in Antarctic sea <span class="hlt">ice</span> thickness and volume over a 5 year period from 2003-2008. Sea <span class="hlt">ice</span> thickness exhibits a small negative trend while area increases in the summer and fall balanced losses in thickness leading to small overall volume changes. Using a five year time-series, we show that only small <span class="hlt">ice</span> thickness changes of less than -0.03 m/yr and volume changes of -266 cu km/yr and 160 cu km/yr occurred for the spring and summer periods, respectively. The calculated thickness and volume trends are small compared to the observational time period and interannual variability which masks the determination of long-term trend or cyclical variability in the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. These results are in stark contrast to the much greater observed losses in Arctic sea <span class="hlt">ice</span> volume and illustrate the different hemispheric changes of the polar sea <span class="hlt">ice</span> <span class="hlt">covers</span> in recent years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1220A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1220A"><span>Polynyas and <span class="hlt">Ice</span> Production Evolution in the Ross Sea (PIPERS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ackley, S. F.</p> <p>2017-12-01</p> <p>One focus of the PIPERS cruise into the Ross Sea <span class="hlt">ice</span> <span class="hlt">cover</span> during April-June 2017 was the Terra Nova Bay (TNB) polynya where joint measurements of air-<span class="hlt">ice</span>-ocean wave interaction were conducted over twelve days. In Terra Nova Bay, measurements were made in three katabatic wind events each with sustained winds over 35 ms-1 and air temperatures below -15C. Near shore, intense wave fields with wave amplitudes of over 2m and 7-9 sec periods built and large amounts of frazil <span class="hlt">ice</span> crystals grew. The frazil <span class="hlt">ice</span> gathered initially into short and narrow plumes that eventually were added laterally to create longer and wider streaks or bands. Breaking waves within these wider streaks were dampened which appeared to enhance the development of pancake <span class="hlt">ice</span>. Eventually, the open water areas between the streaks sealed off, developing a complete <span class="hlt">ice</span> <span class="hlt">cover</span> of 100 percent concentration (80-90 percent pancakes, 20-10 percent frazil) over a wide front (30km). The pancakes continued to grow in diameter and thickness as waves alternately contracted and expanded the <span class="hlt">ice</span> <span class="hlt">cover</span>, with the thicker larger floes further diminishing the wave field and lateral motion between pancakes until the initial pancake <span class="hlt">ice</span> growth ceased. The equilibrium thickness of the <span class="hlt">ice</span> was 20-30cm in the pancake <span class="hlt">ice</span>. While the waves had died off however, katabatic wind velocities were sustained and resulted in a wide area of concentrated, rafted, pancake <span class="hlt">ice</span> that was rapidly advected downstream until the end of the katabatic event. High resolution TerraSar-X radar satellite imagery showed the length of the <span class="hlt">ice</span> area produced in one single event extended over 300km or ten times the length of the open water area during one polynya event. The TNB polynya is therefore an "<span class="hlt">ice</span> factory" where frazil <span class="hlt">ice</span> is manufactured into pancake <span class="hlt">ice</span> floes that are then pushed out of the assembly area and advected, rafted (and occasionally piled up into "dragon skin" <span class="hlt">ice</span>), until the katabatic wind dies off at the coastal source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcMod..84...51L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcMod..84...51L"><span>Processes driving sea <span class="hlt">ice</span> variability in the Bering Sea in an eddying ocean/sea <span class="hlt">ice</span> model: Mean seasonal cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Linghan; McClean, Julie L.; Miller, Arthur J.; Eisenman, Ian; Hendershott, Myrl C.; Papadopoulos, Caroline A.</p> <p>2014-12-01</p> <p>The seasonal cycle of sea <span class="hlt">ice</span> variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-<span class="hlt">ice</span> model configured in the Community Earth System Model (CESM) framework. The ocean/sea-<span class="hlt">ice</span> model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea <span class="hlt">Ice</span> Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970-1989. This study focuses on the time period 1980-1989. The simulated seasonal-mean fields of sea <span class="hlt">ice</span> concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea <span class="hlt">ice</span> energy budget reveals that the seasonal thermodynamic <span class="hlt">ice</span> volume changes are dominated by the surface energy flux between the atmosphere and the <span class="hlt">ice</span> in the northern region and by heat flux from the ocean to the <span class="hlt">ice</span> along the southern <span class="hlt">ice</span> edge, especially on the western side. The sea <span class="hlt">ice</span> force balance analysis shows that sea <span class="hlt">ice</span> motion is largely associated with wind stress. The force due to divergence of the internal <span class="hlt">ice</span> stress tensor is large near the land boundaries in the north, and it is small in the central and southern <span class="hlt">ice-covered</span> region. During winter, which dominates the annual mean, it is found that the simulated sea <span class="hlt">ice</span> was mainly formed in the northern Bering Sea, with the maximum <span class="hlt">ice</span> growth rate occurring along the coast due to cold air from northerly winds and <span class="hlt">ice</span> motion away from the coast. South of St Lawrence Island, winds drive the model sea <span class="hlt">ice</span> southwestward from the north to the southwestern part of the <span class="hlt">ice-covered</span> region. Along the <span class="hlt">ice</span> edge in the western Bering Sea, model sea <span class="hlt">ice</span> is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric <span class="hlt">ice</span> edge. In spring and fall, similar thermodynamic and dynamic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000643.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000643.html"><span>Sea <span class="hlt">ice</span> in the Greenland Sea</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p>As the northern hemisphere experiences the heat of summer, <span class="hlt">ice</span> moves and melts in the Arctic waters and the far northern lands surrounding it. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image of sea <span class="hlt">ice</span> off Greenland on July 16, 2015. Large chunks of melting sea <span class="hlt">ice</span> can be seen in the sea <span class="hlt">ice</span> off the coast, and to the south spirals of <span class="hlt">ice</span> have been shaped by the winds and currents that move across the Greenland Sea. Along the Greenland coast, cold, fresh melt water from the glaciers flows out to the sea, as do newly calved icebergs. Frigid air from interior Greenland pushes the <span class="hlt">ice</span> away from the shoreline, and the mixing of cold water and air allows some sea <span class="hlt">ice</span> to be sustained even at the height of summer. According to observations from satellites, 2015 is on track to be another low year for arctic summer sea <span class="hlt">ice</span> <span class="hlt">cover</span>. The past ten years have included nine of the lowest <span class="hlt">ice</span> extents on record. The annual minimum typically occurs in late August or early September. The amount of Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> has been dropping as global temperatures rise. The Arctic is two to three times more sensitive to temperature changes as the Earth as a whole. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P43C2117H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P43C2117H"><span><span class="hlt">Ice</span> under <span class="hlt">cover</span>: Using bulk spatial and physical properties of probable ground <span class="hlt">ice</span> driven mass wasting features on Ceres to better understand its surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hughson, K.; Russell, C.; Schmidt, B. E.; Chilton, H.; Scully, J. E. C.; Castillo, J. C.; Combe, J. P.; Ammannito, E.; Sizemore, H.; Platz, T.; Byrne, S.; Nathues, A.; Raymond, C. A.</p> <p>2016-12-01</p> <p>NASA's Dawn spacecraft arrived at Ceres on March 6, 2015, and has been studying the dwarf planet through a series of successively lower orbits, obtaining morphological and topographical image, mineralogical, elemental composition, and gravity data (Russell et al., 2016). Images taken by Dawn's Framing Camera show a multitude of flow features that were broadly interpreted as ground <span class="hlt">ice</span> related structures either similar to <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented flows (as seen on Earth and Mars), long run-out landslides, or fluidized ejecta (as seen on Mars) by Schmidt et al. (2016a and 2016b) and Buczkowski et al. (2016). The aforementioned <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented-like flows are present only at high latitudes. Results from Dawn's Gamma Ray and Neutron Detector (GRaND) indicate a shallow <span class="hlt">ice</span> table on Ceres above 45-50°N/S, which supports the interpretation that these flows are <span class="hlt">ice</span>-rich (Prettyman et al., 2016). A near coincident spectral detection of H2O <span class="hlt">ice</span> with one of these <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented-like flows in Oxo crater by Dawn's Visual and Infrared spectrometer (VIR) further bolsters this claim (Combe et al., 2016). We use aggregate spatial and physical properties of these <span class="hlt">ice</span> attributed cerean flows, such as flow orientation, inclination, preference for north or south facing slopes, drop height to run-out length ratio, geographical location, and areal number density to better understand the rheology and distribution of ground <span class="hlt">ice</span> in Ceres' uppermost layer. By combining these data with local spectroscopic, global elemental abundance, experimentally derived physical properties of cerean analogue material, and other morphological information (such as the morphologies of flow hosting craters) we intend to further test the ground <span class="hlt">ice</span> hypothesis for the formation of these flows and constrain the global distribution of near surface ground <span class="hlt">ice</span> on Ceres to a higher fidelity than what would be possible using GRaND and VIR observations alone. References: Buczkowski et al., (2016) Science</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRG..120.2326L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRG..120.2326L"><span>Assessing the potential impacts of declining Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> on the photochemical degradation of dissolved organic matter in the Chukchi and Beaufort Seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Logvinova, Christie L.; Frey, Karen E.; Mann, Paul J.; Stubbins, Aron; Spencer, Robert G. M.</p> <p>2015-11-01</p> <p>A warming and shifting climate in the Arctic has led to significant declines in sea <span class="hlt">ice</span> over the last several decades. Although these changes in sea <span class="hlt">ice</span> <span class="hlt">cover</span> are well documented, large uncertainties remain in how associated increases in solar radiation transmitted to the underlying ocean water column will impact heating, biological, and biogeochemical processes in the Arctic Ocean. In this study, six under-<span class="hlt">ice</span> marine, two <span class="hlt">ice</span>-free marine, and two <span class="hlt">ice</span>-free terrestrially influenced water samples were irradiated using a solar simulator for 72 h (representing ~10 days of ambient sunlight) to investigate dissolved organic matter (DOM) dynamics from the Chukchi and Beaufort Seas. Solar irradiation caused chromophoric DOM (CDOM) light absorption at 254 nm to decrease by 48 to 63%. An overall loss in total DOM fluorescence intensity was also observed at the end of all experiments, and each of six components identified by parallel factor (PARAFAC) analysis was shown to be photoreactive in at least one experiment. Fluorescent DOM (FDOM) also indicated that the majority of DOM in under-<span class="hlt">ice</span> and <span class="hlt">ice</span>-free marine waters was likely algal-derived. Measurable changes in dissolved organic carbon (DOC) were only observed for sites influenced by riverine runoff. Losses of CDOM absorbance at shorter wavelengths suggest that the beneficial UV protection currently received by marine organisms may decline with the increased light transmittance associated with sea <span class="hlt">ice</span> melt ponding and overall reductions of sea <span class="hlt">ice</span>. Our FDOM analyses demonstrate that DOM irrespective of source was susceptible to photobleaching. Additionally, our findings suggest that photodegradation of CDOM in under-<span class="hlt">ice</span> waters is not currently a significant source of carbon dioxide (CO2) (i.e., we did not observe systematic DOC loss). However, increases in primary production and terrestrial freshwater export expected under future climate change scenarios may cause an increase in CDOM quantity and shift in quality</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC23D1173L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC23D1173L"><span>Sparse <span class="hlt">ice</span>: Geophysical, biological and Indigenous knowledge perspectives on a habitat for <span class="hlt">ice</span>-associated fauna</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, O. A.; Eicken, H.; Weyapuk, W., Jr.; Adams, B.; Mohoney, A. R.</p> <p>2015-12-01</p> <p>The significance of highly dispersed, remnant Arctic sea <span class="hlt">ice</span> as a platform for marine mammals and indigenous hunters in spring and summer may have increased disproportionately with changes in the <span class="hlt">ice</span> <span class="hlt">cover</span>. As dispersed remnant <span class="hlt">ice</span> becomes more common in the future it will be increasingly important to understand its ecological role for upper trophic levels such as marine mammals and its role for supporting primary productivity of <span class="hlt">ice</span>-associated algae. Potential sparse <span class="hlt">ice</span> habitat at sea <span class="hlt">ice</span> concentrations below 15% is difficult to detect using remote sensing data alone. A combination of high resolution satellite imagery (including Synthetic Aperture Radar), data from the Barrow sea <span class="hlt">ice</span> radar, and local observations from indigenous sea <span class="hlt">ice</span> experts was used to detect sparse sea <span class="hlt">ice</span> in the Alaska Arctic. Traditional knowledge on sea <span class="hlt">ice</span> use by marine mammals was used to delimit the scales where sparse <span class="hlt">ice</span> could still be used as habitat for seals and walrus. Potential sparse <span class="hlt">ice</span> habitat was quantified with respect to overall spatial extent, size of <span class="hlt">ice</span> floes, and density of floes. Sparse <span class="hlt">ice</span> persistence offshore did not prevent the occurrence of large coastal walrus haul outs, but the lack of sparse <span class="hlt">ice</span> and early sea <span class="hlt">ice</span> retreat coincided with local observations of ringed seal pup mortality. Observations from indigenous hunters will continue to be an important source of information for validating remote sensing detections of sparse <span class="hlt">ice</span>, and improving understanding of marine mammal adaptations to sea <span class="hlt">ice</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2027S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2027S"><span>Sea-<span class="hlt">ice</span> indicators of polar bear habitat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stern, Harry L.; Laidre, Kristin L.</p> <p>2016-09-01</p> <p>Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea <span class="hlt">ice</span> as a platform for traveling, hunting, and breeding. Therefore polar bear phenology - the cycle of biological events - is linked to the timing of sea-<span class="hlt">ice</span> retreat in spring and advance in fall. We analyzed the dates of sea-<span class="hlt">ice</span> retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-<span class="hlt">ice</span> concentration data from satellite passive microwave instruments. We define the dates of sea-<span class="hlt">ice</span> retreat and advance in a region as the dates when the area of sea <span class="hlt">ice</span> drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979-2014) mean September and mean March sea-<span class="hlt">ice</span> areas. In all 19 regions there is a trend toward earlier sea-<span class="hlt">ice</span> retreat and later sea-<span class="hlt">ice</span> advance. Trends generally range from -3 to -9 days decade-1 in spring and from +3 to +9 days decade-1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-<span class="hlt">ice</span> area exceeded the threshold (termed <span class="hlt">ice-covered</span> days) and the average sea-<span class="hlt">ice</span> concentration from 1 June through 31 October. The number of <span class="hlt">ice-covered</span> days is declining in all regions at the rate of -7 to -19 days decade-1, with larger trends in the Barents Sea and central Arctic Basin. The June-October sea-<span class="hlt">ice</span> concentration is declining in all regions at rates ranging from -1 to -9 percent decade-1. These sea-<span class="hlt">ice</span> metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-<span class="hlt">ice</span> retreat and advance in future reports.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830005807','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830005807"><span>NASA Lewis Research Center's Program on <span class="hlt">Icing</span> Research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Reinmann, J. J.; Shaw, R. J.; Olsen, W. A., Jr.</p> <p>1982-01-01</p> <p>The helicopter and general aviation, light transport, and commercial transport aircraft share common <span class="hlt">icing</span> requirements: highly effective, lightweight, low power consuming deicing systems, and detailed knowledge of the aeropenalties due to <span class="hlt">ice</span> on aircraft surfaces. To meet current and future needs, NASA has a broadbased <span class="hlt">icing</span> research program which <span class="hlt">covers</span> both research and engineering applications, and is well coordinated with the FAA, DOD, universities, industry, and some foreign governments. Research activity in <span class="hlt">ice</span> protection systems, <span class="hlt">icing</span> instrumentation, experimental methods, analytical modeling, and in-flight research are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMNG43B1422M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMNG43B1422M"><span>Transient and asymptotic behavior in a regular network model for the <span class="hlt">ice</span>-albedo feedback under thermal forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mueller-Stoffels, M.; Wackerbauer, R.</p> <p>2010-12-01</p> <p>The Arctic ocean and sea <span class="hlt">ice</span> form a feedback system which plays an important role in the global climate. Variations of the global <span class="hlt">ice</span> and snow distribution have a significant effect on the planetary albedo which governs the absorption of shortwave radiation. The complexity of highly parametrized GCMs makes it very difficult to assess single feedback processes in the climate system without the concurrent use of simple models where the physics are understood [1][2][3]. We introduce a complex systems model to investigate thermodynamic feedback processes in an Arctic <span class="hlt">ice</span>-ocean layer. The <span class="hlt">ice</span>-ocean layer is represented as a regular network of coupled cells. The state of each cell is determined by its energy content, which also defines the phase of the cell. The energy transport between cells is described with nonlinear and heterogeneous diffusion constants. And the time-evolution of the <span class="hlt">ice</span>-ocean is driven by shortwave, longwave and lateral oceanic and atmospheric thermal forcing. This model is designed to study the stability of an <span class="hlt">ice</span> <span class="hlt">cover</span> under various heat intake scenarios. The network structure of the model allows to easily introduce albedo heterogeneities due to aging <span class="hlt">ice</span>, wind blown snow <span class="hlt">cover</span>, and <span class="hlt">ice</span> movement to explore the time-evolution and pattern formation (melt ponds) processes in the Arctic sea <span class="hlt">ice</span>. The solely thermodynamic model exhibits two stable states; one in the perennially <span class="hlt">ice</span> <span class="hlt">covered</span> domain and one in the perennially open water domain. Their existence is due to the temperature dependence of the longwave radiative budget. Transition between these states can be forced via lateral heat fluxes. During the transition from the <span class="hlt">ice</span> <span class="hlt">covered</span> to the open water stable state the <span class="hlt">ice</span> albedo feedback effects are manifested as an increased warming rate of the <span class="hlt">ice</span> <span class="hlt">cover</span> together with enhanced seasonal energy oscillations. In the current model realization seasonal <span class="hlt">ice</span> <span class="hlt">cover</span> is present as a transient state only. Furthermore, the model exhibits hysteresis between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.5747D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.5747D"><span><span class="hlt">ICE</span> stereocamera system - photogrammetric setup for retrieval and analysis of small scale sea <span class="hlt">ice</span> topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Divine, Dmitry; Pedersen, Christina; Karlsen, Tor Ivan; Aas, Harald; Granskog, Mats; Renner, Angelika; Spreen, Gunnar; Gerland, Sebastian</p> <p>2013-04-01</p> <p>A new thin-<span class="hlt">ice</span> Arctic paradigm requires reconsideration of the set of parameterizations of mass and energy exchange within the ocean-sea-<span class="hlt">ice</span>-atmosphere system used in modern CGCMs. Such a reassessment would require a comprehensive collection of measurements made specifically on first-year pack <span class="hlt">ice</span> with a focus on summer melt season when the difference from typical conditions for the earlier multi-year Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> becomes most pronounced. Previous in situ studies have demonstrated a crucial importance of smaller (i.e. less than 10 m) scale surface topography features for the seasonal evolution of pack <span class="hlt">ice</span>. During 2011-2012 NPI developed a helicopter borne <span class="hlt">ICE</span> stereocamera system intended for mapping the sea <span class="hlt">ice</span> surface topography and aerial photography. The hardware component of the system comprises two Canon 5D Mark II cameras, combined GPS/INS unit by "Novatel" and a laser altimeter mounted in a single enclosure outside the helicopter. The unit is controlled by a PXI chassis mounted inside the helicopter cabin. The <span class="hlt">ICE</span> stereocamera system was deployed for the first time during the 2012 summer field season. The hardware setup has proven to be highly reliable and was used in about 30 helicopter flights over Arctic sea-<span class="hlt">ice</span> during July-September. Being highly automated it required a minimal human supervision during in-flight operation. The deployment of the camera system was mostly done in combination with the EM-bird, which measures sea-<span class="hlt">ice</span> thickness, and this combination provides an integrated view of sea <span class="hlt">ice</span> <span class="hlt">cover</span> along the flight track. During the flight the cameras shot sequentially with a time interval of 1 second each to ensure sufficient overlap between subsequent images. Some 35000 images of sea <span class="hlt">ice</span>/water surface captured per camera sums into 6 Tb of data collected during its first field season. The reconstruction of the digital elevation model of sea <span class="hlt">ice</span> surface will be done using SOCET SET commercial software. Refraction at water/air interface can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.V21A2763E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.V21A2763E"><span>Experimental Insights on Natural Lava-<span class="hlt">Ice</span>/Snow Interactions and Their Implications for Glaciovolcanic and Submarine Eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, B. R.; Karson, J.; Wysocki, R.; Lev, E.; Bindeman, I. N.; Kueppers, U.</p> <p>2012-12-01</p> <p>Lava-<span class="hlt">ice</span>-snow interactions have recently gained global attention through the eruptions of <span class="hlt">ice-covered</span> volcanoes, particularly from Eyjafjallajokull in south-central Iceland, with dramatic effects on local communities and global air travel. However, as with most submarine eruptions, direct observations of lava-<span class="hlt">ice</span>/snow interactions are rare. Only a few hundred potentially active volcanoes are presently <span class="hlt">ice-covered</span>, these volcanoes are generally in remote places, and their associated hazards make close observation and measurements dangerous. Here we report the results of the first large-scale experiments designed to provide new constraints on natural interactions between lava and <span class="hlt">ice</span>/snow. The experiments comprised controlled effusion of tens of kilograms of melted basalt on top of <span class="hlt">ice</span>/snow, and provide insights about observations from natural lava-<span class="hlt">ice</span>-snow interactions including new constraints for: 1) rapid lava advance along the <span class="hlt">ice</span>-lava interface; 2) rapid downwards melting of lava flows through <span class="hlt">ice</span>; 3) lava flow exploitation of pre-existing discontinuities to travel laterally beneath and within <span class="hlt">ice</span>; and 4) formation of abundant limu o Pele and non-explosive vapor transport from the <span class="hlt">base</span> to the top of the lava flow with minor O isotope exchange. The experiments are consistent with observations from eruptions showing that lava is more efficient at melting <span class="hlt">ice</span> when emplaced on top of the <span class="hlt">ice</span> as opposed to beneath the <span class="hlt">ice</span>, as well as the efficacy of tephra <span class="hlt">cover</span> for slowing melting. The experimental extrusion rates are as within the range of those for submarine eruptions as well, and reproduce some features seen in submarine eruptions including voluminous production of gas rich cavities within initially anhydrous lavas and limu on lava surfaces. Our initial results raise questions about the possibility of secondary ingestion of water by submarine and glaciovolcanic lava flows, and the origins of apparent primary gas cavities in those flows. Basaltic melt moving down</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1919075L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1919075L"><span><span class="hlt">Ice</span> Flows: A Game-<span class="hlt">based</span> Learning approach to Science Communication</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Brocq, Anne</p> <p>2017-04-01</p> <p>Game-<span class="hlt">based</span> learning allows people to become immersed in an environment, and learn how the system functions and responds to change through playing a game. Science and gaming share a similar characteristic: they both involve learning and understanding the rules of the environment you are in, in order to achieve your objective. I will share experiences of developing and using the educational game "<span class="hlt">Ice</span> Flows" for science communication. The game tasks the player with getting a penguin to its destination, through controlling the size of the <span class="hlt">ice</span> sheet via ocean temperature and snowfall. Therefore, the game aims to educate the user about the environmental controls on the behaviour of the <span class="hlt">ice</span> sheet, whilst they are enjoying playing a game with penguins. The game was funded by a NERC Large Grant entitled "<span class="hlt">Ice</span> shelves in a warming world: Filchner <span class="hlt">Ice</span> Shelf system, Antarctica", so uses data from the Weddell Sea sector of the West Antarctic <span class="hlt">Ice</span> Sheet to generate unique levels. The game will be easily expandable to other regions of Antarctica and beyond, with the ultimate aim of giving a full understanding to the user of different <span class="hlt">ice</span> flow regimes across the planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910044122&hterms=refraction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drefraction','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910044122&hterms=refraction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drefraction"><span>Observation of wave refraction at an <span class="hlt">ice</span> edge by synthetic aperture radar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, Antony K.; Vachon, Paris W.; Peng, Chih Y.</p> <p>1991-01-01</p> <p>In this note the refraction of waves at the <span class="hlt">ice</span> edge is studied by using aircraft synthesis aperture radar (SAR). Penetration of a dominant swell from open ocean into the <span class="hlt">ice</span> <span class="hlt">cover</span> was observed by SAR during the Labrador <span class="hlt">Ice</span> Margin Experiment (LIMEX), conducted on the marginal <span class="hlt">ice</span> zone (MIZ) off the east coast of Newfoundland, Canada, in March 1987. At an <span class="hlt">ice</span> edge with a large curvature, the dominant swell component disappeared locally in the SAR imagery. Six subscenes of waves in the MIZ from the SAR image have been processed, revealing total reflection, refraction, and energy reduction of the ocean waves by the <span class="hlt">ice</span> <span class="hlt">cover</span>. The observed variations of wave spectra from SAR near the <span class="hlt">ice</span> edge are consistent with the model prediction of wave refraction at the <span class="hlt">ice</span> edge due to the change of wave dispersion relation in <span class="hlt">ice</span> developed by Liu and Mollo-Christensen (1988).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920045032&hterms=GMT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DGMT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920045032&hterms=GMT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DGMT"><span>AVHRR imagery reveals Antarctic <span class="hlt">ice</span> dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bindschadler, Robert A.; Vornberger, Patricia L.</p> <p>1990-01-01</p> <p>A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of <span class="hlt">ice</span> sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the <span class="hlt">ice</span> sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which <span class="hlt">cover</span> the area of <span class="hlt">ice</span> streams that drain the interior of the West Antarctic <span class="hlt">ice</span> sheet into the Ross <span class="hlt">Ice</span> Shelf.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816755T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816755T"><span>eVolv2k: A new <span class="hlt">ice</span> core-<span class="hlt">based</span> volcanic forcing reconstruction for the past 2000 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toohey, Matthew; Sigl, Michael</p> <p>2016-04-01</p> <p>Radiative forcing resulting from stratospheric aerosols produced by major volcanic eruptions is a dominant driver of climate variability in the Earth's past. The ability of climate model simulations to accurately recreate past climate is tied directly to the accuracy of the volcanic forcing timeseries used in the simulations. We present here a new volcanic forcing reconstruction, <span class="hlt">based</span> on newly updated <span class="hlt">ice</span> core composites from Antarctica and Greenland. <span class="hlt">Ice</span> core records are translated into stratospheric aerosol properties for use in climate models through the Easy Volcanic Aerosol (EVA) module, which provides an analytic representation of volcanic stratospheric aerosol forcing <span class="hlt">based</span> on available observations and aerosol model results, prescribing the aerosol's radiative properties and primary modes of spatial and temporal variability. The evolv2k volcanic forcing dataset <span class="hlt">covers</span> the past 2000 years, and has been provided for use in the Paleo-Modeling Intercomparison Project (PMIP), and VolMIP experiments within CMIP6. Here, we describe the construction of the eVolv2k data set, compare with prior forcing sets, and show initial simulation results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5067M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5067M"><span>Satellite altimetry in sea <span class="hlt">ice</span> regions - detecting open water for estimating sea surface heights</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller, Felix L.; Dettmering, Denise; Bosch, Wolfgang</p> <p>2017-04-01</p> <p>The Greenland Sea and the Farm Strait are transporting sea <span class="hlt">ice</span> from the central Arctic ocean southwards. They are <span class="hlt">covered</span> by a dynamic changing sea <span class="hlt">ice</span> layer with significant influences on the Earth climate system. Between the sea <span class="hlt">ice</span> there exist various sized open water areas known as leads, straight lined open water areas, and polynyas exhibiting a circular shape. Identifying these leads by satellite altimetry enables the extraction of sea surface height information. Analyzing the radar echoes, also called waveforms, provides information on the surface backscatter characteristics. For example waveforms reflected by calm water have a very narrow and single-peaked shape. Waveforms reflected by sea <span class="hlt">ice</span> show more variability due to diffuse scattering. Here we analyze altimeter waveforms from different conventional pulse-limited satellite altimeters to separate open water and sea <span class="hlt">ice</span> waveforms. An unsupervised classification approach employing partitional clustering algorithms such as K-medoids and memory-<span class="hlt">based</span> classification methods such as K-nearest neighbor is used. The classification is <span class="hlt">based</span> on six parameters derived from the waveform's shape, for example the maximum power or the peak's width. The open-water detection is quantitatively compared to SAR images processed while accounting for sea <span class="hlt">ice</span> motion. The classification results are used to derive information about the temporal evolution of sea <span class="hlt">ice</span> extent and sea surface heights. They allow to provide evidence on climate change relevant influences as for example Arctic sea level rise due to enhanced melting rates of Greenland's glaciers and an increasing fresh water influx into the Arctic ocean. Additionally, the sea <span class="hlt">ice</span> <span class="hlt">cover</span> extent analyzed over a long-time period provides an important indicator for a globally changing climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25908601','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25908601"><span>Exposure age and <span class="hlt">ice</span>-sheet model constraints on Pliocene East Antarctic <span class="hlt">ice</span> sheet dynamics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki</p> <p>2015-04-24</p> <p>The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic <span class="hlt">Ice</span> Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand <span class="hlt">ice</span> sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An <span class="hlt">ice</span> sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased <span class="hlt">ice</span> volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea <span class="hlt">ice</span> <span class="hlt">cover</span> and inhibited active moisture transport to Antarctica, resulting in reduced <span class="hlt">ice</span> sheet thickness, at least in coastal areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940026121','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940026121"><span>A toy model of sea <span class="hlt">ice</span> growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thorndike, Alan S.</p> <p>1992-01-01</p> <p>My purpose here is to present a simplified treatment of the growth of sea <span class="hlt">ice</span>. By ignoring many details, it is possible to obtain several results that help to clarify the ways in which the sea <span class="hlt">ice</span> <span class="hlt">cover</span> will respond to climate change. Three models are discussed. The first deals with the growth of sea <span class="hlt">ice</span> during the cold season. The second describes the cycle of growth and melting for perennial <span class="hlt">ice</span>. The third model extends the second to account for the possibility that the <span class="hlt">ice</span> melts away entirely in the summer. In each case, the objective is to understand what physical processes are most important, what <span class="hlt">ice</span> properties determine the <span class="hlt">ice</span> behavior, and to which climate variables the system is most sensitive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920055266&hterms=sonar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsonar','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920055266&hterms=sonar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsonar"><span>An <span class="hlt">ice</span>-ocean coupled model for the Northern Hemisphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheng, Abe; Preller, Ruth</p> <p>1992-01-01</p> <p>The Hibler <span class="hlt">ice</span> model has been modified and adapted to a domain that includes most of the sea <span class="hlt">ice-covered</span> areas in the Northern Hemisphere. This model, joined with the Cox ocean model, is developed as an enhancement to the U.S. Navy's sea <span class="hlt">ice</span> forecasting, PIPS, and is termed PIPS2.0. Generally, the modeled <span class="hlt">ice</span> edge is consistent with the Navy-NOAA Joint <span class="hlt">Ice</span> Center weekly analysis, and the modeled <span class="hlt">ice</span> thickness distribution agrees with submarine sonar data in the central Arctic basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EPJC...77..692A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EPJC...77..692A"><span>Measurement of the ν _{μ } energy spectrum with <span class="hlt">Ice</span>Cube-79</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Al Samarai, I.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bagherpour, H.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Bradascio, F.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Bron, S.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Unger, E.; Usner, M.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Vehring, M.; Voge, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Waza, A.; Weaver, Ch.; Weiss, M. J.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.</p> <p>2017-10-01</p> <p><span class="hlt">Ice</span>Cube is a neutrino observatory deployed in the glacial <span class="hlt">ice</span> at the geographic South Pole. The ν _μ energy unfolding described in this paper is <span class="hlt">based</span> on data taken with <span class="hlt">Ice</span>Cube in its 79-string configuration. A sample of muon neutrino charged-current interactions with a purity of 99.5% was selected by means of a multivariate classification process <span class="hlt">based</span> on machine learning. The subsequent unfolding was performed using the software Truee. The resulting spectrum <span class="hlt">covers</span> an E_ν -range of more than four orders of magnitude from 125 GeV to 3.2 PeV. Compared to the Honda atmospheric neutrino flux model, the energy spectrum shows an excess of more than 1.9 σ in four adjacent bins for neutrino energies E_ν ≥ 177.8 {TeV}. The obtained spectrum is fully compatible with previous measurements of the atmospheric neutrino flux and recent <span class="hlt">Ice</span>Cube measurements of a flux of high-energy astrophysical neutrinos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020050249','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020050249"><span>Hellas as a Possible Site of Ancient <span class="hlt">Ice-Covered</span> Lakes on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, Jeffrey M.; Wilhelms, Don E.; DeVincenzi, Donald (Technical Monitor)</p> <p>2002-01-01</p> <p><span class="hlt">Based</span> on topographic, morphologic, and stratigraphic evidence, we propose that ancient water-laid sediment is the dominant component of deposits within Hellas Planitia, Mars. Multiply layered sediment is manifested by alternating benches and scarps visible in Mars Orbiting Camera narrow-angle (MOC NA) images. Viking Orbiter camera and MOC NA images were used to map contacts and stratigraphically order the different materials units within Hellas. Mar's Orbiting Laser Altimeter (MOLA) data reveal that the contacts of these sedimentary units, as well as a number of scarps or other abrupt changes in landscape texture, trace contours of constant elevation for thousands of km, and in one case all around the basin. Channels, consensually interpreted to be cut by water, lead into the basin. MOLA results indicate that the area encompassed by greater Hellas' highest closed contour is nearly one-fifth that of the entire northern plains, making the Hellas 'drainage' area much larger than previously reported. If lakes formed under climatic conditions similar to the modern Martian climate, they would develop thick <span class="hlt">ice</span> carapaces, then the lakes would eventually sublimate away. Two units within Hellas exhibit a reticulate or honeycomb pattern we speculate are impressions made by lake-lowered <span class="hlt">ice</span> blocks grounding into initially soft mud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70023375','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70023375"><span>Hellas as a possible site of ancient <span class="hlt">ice-covered</span> lakes on Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Moore, Johnnie N.; Wilhelms, D.E.</p> <p>2001-01-01</p> <p><span class="hlt">Based</span> on topographic, morphologic, and stratigraphic evidence, we propose that ancient water-laid sediment is the dominant component of deposits within Hellas Planitia, Mars. Multiple-layered sediment is manifested by alternating benches and scarps visible in Mars orbiting camera narrow-angle (MOC NA) images. Viking Orbiter camera and MOC NA images were used to map contacts and stratigraphically order the different materials units within Hellas. Mars orbiting laser altimeter (MOLA) data reveal that the contacts of these sedimentary units, as well as a number of scarps or other abrupt changes in landscape texture, trace contours of constant elevation for thousands of km, and in one case all around the basin. Channels, consensually interpreted to be cut by water, lead into the basin. MOLA results indicate that the area encompassed by greater Hellas' highest closed contour is nearly one-fifth that of the entire northern plains, making the Hellas "drainage" area much larger than previously reported. If lakes formed under climatic conditions similar to the modern Martian climate, they would develop thick <span class="hlt">ice</span> carapaces, then the lakes would eventually sublimate away. Two units within Hellas exhibit a reticulate or honeycomb pattern, which we speculate are impressions made by lake-lowered <span class="hlt">ice</span> blocks grounding into initially soft mud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P43C2889P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P43C2889P"><span>Variability in radar returns from Martian debris-<span class="hlt">covered</span> glaciers attributed to surface debris layer roughness and composition: implications for the regional distribution of massive subsurface <span class="hlt">ice</span> and near-surface pore-filling <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petersen, E.; Holt, J. W.; Levy, J. S.; Lalich, D.</p> <p>2017-12-01</p> <p>Lobate debris aprons, lineated valley fill, and concentric crater fill are a class of Martian landform thought to be glaciers blanketed by a lithic debris layer. They are found in the mid latitudes (roughly 30-50°N and S) where surface <span class="hlt">ice</span> is presently unstable. Shallow Radar (SHARAD) sounder observations are in many cases able to resolve the basal contact between the glacier and underlying bedrock, showing that the bulk composition of these features is water <span class="hlt">ice</span> with < 20% lithic debris; they are thus often referred to as debris-<span class="hlt">covered</span> glaciers (DCG). The basal contact of candidate glaciers is not always present in SHARAD radargrams, and variable reflection power between glacier sites suggests that non-detections may be due to a reduction of echo power below the noise floor. A likely candidate for signal loss is the variable roughness of different glacial surface textures. We test this mechanism of signal reduction via analysis of SHARAD reflections augmented by surface roughness analyses generated from HiRISE stereo DEMs. This method provides a means of constraining the electrical properties of the surface debris. We show that measured surface roughness is sufficient to explain basal reflection signal loss for five glacier sites in the region of Deuteronilus/Protonilus Mensae (R2 = 0.90), with the dielectric constant for the surface debris layer constrained to 4.9 ± 0.3. Assuming debris formed of basalt rock, this value is consistent with a porous debris layer containing up to 64% <span class="hlt">ice</span>, or an <span class="hlt">ice</span>-free debris layer with porosity of 28-34%. From this work, we conclude that (1) weak or non-existent basal reflections at these sites are due to roughness-induced radar signal loss and not due to differing properties of the basal interface, (2) all DCG candidates in this study exhibit similar bulk compositions of relatively pure water <span class="hlt">ice</span>, and (3) the surface debris layer is formed of porous lithic debris which may contain a significant fraction of pore <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..892C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..892C"><span>Mechanisms of interannual- to decadal-scale winter Labrador Sea <span class="hlt">ice</span> variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Close, S.; Herbaut, C.; Houssais, M.-N.; Blaizot, A.-C.</p> <p>2017-12-01</p> <p>The variability of the winter sea <span class="hlt">ice</span> <span class="hlt">cover</span> of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean-sea <span class="hlt">ice</span> model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea <span class="hlt">ice</span> <span class="hlt">cover</span> are found amongst the various data sets. The highest values of sea <span class="hlt">ice</span> area occur when the northern Labrador Sea is <span class="hlt">ice</span> <span class="hlt">covered</span>. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea <span class="hlt">ice</span> is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea <span class="hlt">ice</span> melt, driven by the enhanced offshore transport of sea <span class="hlt">ice</span> in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea <span class="hlt">ice</span> transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea <span class="hlt">ice</span> area of the following winter is obtained. This relationship represents a dependence on the availability of sea <span class="hlt">ice</span> to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..993Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..993Z"><span>On the retrieval of sea <span class="hlt">ice</span> thickness and snow depth using concurrent laser altimetry and L-band remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Lu; Xu, Shiming; Liu, Jiping; Wang, Bin</p> <p>2018-03-01</p> <p>The accurate knowledge of sea <span class="hlt">ice</span> parameters, including sea <span class="hlt">ice</span> thickness and snow depth over the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, is key to both climate studies and data assimilation in operational forecasts. Large-scale active and passive remote sensing is the basis for the estimation of these parameters. In traditional altimetry or the retrieval of snow depth with passive microwave remote sensing, although the sea <span class="hlt">ice</span> thickness and the snow depth are closely related, the retrieval of one parameter is usually carried out under assumptions over the other. For example, climatological snow depth data or as derived from reanalyses contain large or unconstrained uncertainty, which result in large uncertainty in the derived sea <span class="hlt">ice</span> thickness and volume. In this study, we explore the potential of combined retrieval of both sea <span class="hlt">ice</span> thickness and snow depth using the concurrent active altimetry and passive microwave remote sensing of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Specifically, laser altimetry and L-band passive remote sensing data are combined using two forward models: the L-band radiation model and the isostatic relationship <span class="hlt">based</span> on buoyancy model. Since the laser altimetry usually features much higher spatial resolution than L-band data from the Soil Moisture Ocean Salinity (SMOS) satellite, there is potentially covariability between the observed snow freeboard by altimetry and the retrieval target of snow depth on the spatial scale of altimetry samples. Statistically significant correlation is discovered <span class="hlt">based</span> on high-resolution observations from Operation <span class="hlt">Ice</span>Bridge (OIB), and with a nonlinear fitting the covariability is incorporated in the retrieval algorithm. By using fitting parameters derived from large-scale surveys, the retrievability is greatly improved compared with the retrieval that assumes flat snow <span class="hlt">cover</span> (i.e., no covariability). Verifications with OIB data show good match between the observed and the retrieved parameters, including both sea <span class="hlt">ice</span> thickness and snow depth. With</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C43E0586E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C43E0586E"><span>Carbon Dioxide Transfer Through Sea <span class="hlt">Ice</span>: Modelling Flux in Brine Channels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, L.; Mitchelson-Jacob, G.; Hardman-Mountford, N.</p> <p>2010-12-01</p> <p>For many years sea <span class="hlt">ice</span> was thought to act as a barrier to the flux of CO2 between the ocean and atmosphere. However, laboratory-<span class="hlt">based</span> and in-situ observations suggest that while sea <span class="hlt">ice</span> may in some circumstances reduce or prevent transfer (e.g. in regions of thick, superimposed multi-year <span class="hlt">ice</span>), it may also be highly permeable (e.g. thin, first year <span class="hlt">ice</span>) with some studies observing significant fluxes of CO2. Sea <span class="hlt">ice</span> <span class="hlt">covered</span> regions have been observed to act both as a sink and a source of atmospheric CO2 with the permeability of sea <span class="hlt">ice</span> and direction of flux related to sea <span class="hlt">ice</span> temperature and the presence of brine channels in the <span class="hlt">ice</span>, as well as seasonal processes such as whether the <span class="hlt">ice</span> is freezing or thawing. Brine channels concentrate dissolved inorganic carbon (DIC) as well as salinity and as these dense waters descend through both the sea <span class="hlt">ice</span> and the surface ocean waters, they create a sink for CO2. Calcium carbonate (ikaite) precipitation in the sea <span class="hlt">ice</span> is thought to enhance this process. Micro-organisms present within the sea <span class="hlt">ice</span> will also contribute to the CO2 flux dynamics. Recent evidence of decreasing sea <span class="hlt">ice</span> extent and the associated change from a multi-year <span class="hlt">ice</span> to first-year <span class="hlt">ice</span> dominated system suggest the potential for increased CO2 flux through regions of thinner, more porous sea <span class="hlt">ice</span>. A full understanding of the processes and feedbacks controlling the flux in these regions is needed to determine their possible contribution to global CO2 levels in a future warming climate scenario. Despite the significance of these regions, the air-sea CO2 flux in sea <span class="hlt">ice</span> <span class="hlt">covered</span> regions is not currently included in global climate models. Incorporating this carbon flux system into Earth System models requires the development of a well-parameterised sea <span class="hlt">ice</span>-air flux model. In our work we use the Los Alamos sea <span class="hlt">ice</span> model, CICE, with a modification to incorporate the movement of CO2 through brine channels including the addition of DIC processes and <span class="hlt">ice</span> algae production to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PolSc..10..239S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PolSc..10..239S"><span>Surface elevation change on <span class="hlt">ice</span> caps in the Qaanaaq region, northwestern Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saito, Jun; Sugiyama, Shin; Tsutaki, Shun; Sawagaki, Takanobu</p> <p>2016-09-01</p> <p>A large number of glaciers and <span class="hlt">ice</span> caps (GICs) are distributed along the Greenland coast, physically separated from the <span class="hlt">ice</span> sheet. The total area of these GICs accounts for 5% of Greenland's <span class="hlt">ice</span> <span class="hlt">cover</span>. Melt water input from the GICs to the ocean substantially contributed to sea-level rise over the last century. Here, we report surface elevation changes of six <span class="hlt">ice</span> caps near Qaanaaq (77°28‧N, 69°13‧W) in northwestern Greenland <span class="hlt">based</span> on photogrammetric analysis of stereo pair satellite images. We processed the images with a digital map plotting instrument to generate digital elevation models (DEMs) in 2006 and 2010 with a grid resolution of 500 m. Generated DEMs were compared to measure surface elevation changes between 2006 and 2010. Over the study area of the six <span class="hlt">ice</span> caps, <span class="hlt">covering</span> 1215 km2, the mean rate of elevation change was -1.1 ± 0.1 m a-1. This rate is significantly greater than that previously reported for the 2003-2008 period (-0.6 ± 0.1 m a-1) for GICs all of northwestern Greenland. This increased mass loss is consistent with the rise in summer temperatures in this region at a rate of 0.12 °C a-1 for the 1997-2013 period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23413190','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23413190"><span>Export of algal biomass from the melting Arctic sea <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boetius, Antje; Albrecht, Sebastian; Bakker, Karel; Bienhold, Christina; Felden, Janine; Fernández-Méndez, Mar; Hendricks, Stefan; Katlein, Christian; Lalande, Catherine; Krumpen, Thomas; Nicolaus, Marcel; Peeken, Ilka; Rabe, Benjamin; Rogacheva, Antonina; Rybakova, Elena; Somavilla, Raquel; Wenzhöfer, Frank</p> <p>2013-03-22</p> <p>In the Arctic, under-<span class="hlt">ice</span> primary production is limited to summer months and is restricted not only by <span class="hlt">ice</span> thickness and snow <span class="hlt">cover</span> but also by the stratification of the water column, which constrains nutrient supply for algal growth. Research Vessel Polarstern visited the <span class="hlt">ice-covered</span> eastern-central basins between 82° to 89°N and 30° to 130°E in summer 2012, when Arctic sea <span class="hlt">ice</span> declined to a record minimum. During this cruise, we observed a widespread deposition of <span class="hlt">ice</span> algal biomass of on average 9 grams of carbon per square meter to the deep-sea floor of the central Arctic basins. Data from this cruise will contribute to assessing the effect of current climate change on Arctic productivity, biodiversity, and ecological function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009528','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009528"><span>Antarctic Sea <span class="hlt">Ice</span> Variability and Trends, 1979-2010</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, C. L.; Cavalieri, D. J.</p> <p>2012-01-01</p> <p>In sharp contrast to the decreasing sea <span class="hlt">ice</span> coverage of the Arctic, in the Antarctic the sea <span class="hlt">ice</span> <span class="hlt">cover</span> has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978 - December 2010 reveal an overall positive trend in <span class="hlt">ice</span> extents of 17,100 +/- 2,300 square km/yr. Much of the increase, at 13,700 +/- 1,500 square km/yr, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has, like the Arctic, instead experienced significant sea <span class="hlt">ice</span> decreases, with an overall <span class="hlt">ice</span> extent trend of -8,200 +/- 1,200 square km/yr. When examined through the annual cycle over the 32-year period 1979-2010, the Southern Hemisphere sea <span class="hlt">ice</span> <span class="hlt">cover</span> as a whole experienced positive <span class="hlt">ice</span> extent trends in every month, ranging in magnitude from a low of 9,100 +/- 6,300 square km/yr in February to a high of 24,700 +/- 10,000 square km/yr in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and Western Pacific Ocean had a mixture of positive and negative trends. Comparing <span class="hlt">ice</span>-area results to <span class="hlt">ice</span>-extent results, in each case the <span class="hlt">ice</span>-area trend has the same sign as the <span class="hlt">ice</span>-extent trend, but differences in the magnitudes of the two trends identify regions with overall increasing <span class="hlt">ice</span> concentrations and others with overall decreasing <span class="hlt">ice</span> concentrations. The strong pattern of decreasing <span class="hlt">ice</span> coverage in the Bellingshausen/Amundsen Seas region and increasing <span class="hlt">ice</span> coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMGC11B..08Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMGC11B..08Y"><span>Climatic Changes on Tibetan Plateau <span class="hlt">Based</span> on <span class="hlt">Ice</span> Core Records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yao, T.</p> <p>2008-12-01</p> <p>Climatic changes have been reconstructed for the Tibetan Plateau <span class="hlt">based</span> on <span class="hlt">ice</span> core records. The Guliya <span class="hlt">ice</span> core on the Tibetan Plateau presents climatic changes in the past 100,000 years, thus is comparative with that from Vostok <span class="hlt">ice</span> core in Antarctica and GISP2 record in Arctic. These three records share an important common feature, i.e., our climate is not stable. It is also evident that the major patterns of climatic changes are similar on the earth. Why does climatic change over the earth follow a same pattern? It might be attributed to solar radiation. We found that the cold periods correspond to low insolation periods, and warm periods to high insolation periods. We found abrupt climatic change in the <span class="hlt">ice</span> core climatic records, which presented dramatic temperature variation of as much as 10 °C in 50 or 60 years. Our major challenge in the study of both climate and environment is that greenhouse gases such as CO2, CH4 are possibly amplifying global warming, though at what degree remains unclear. One of the ways to understand the role of greenhouse gases is to reconstruct the past greenhouse gases recorded in <span class="hlt">ice</span>. In 1997, we drilled an <span class="hlt">ice</span> core from 7100 m a.s.l. in the Himalayas to reconstruct methane record. <span class="hlt">Based</span> on the record, we found seasonal cycles in methane variation. In particular, the methane concentration is high in summer, suggestiing active methane emission from wet land in summer. <span class="hlt">Based</span> on the seasonal cycle, we can reconstruct the methane fluctuation history in the past 500 years. The most prominent feature of the methane record in the Himalayan <span class="hlt">ice</span> core is the abrupt increase since 1850 A.D.. This is closely related to the industrial revolution worldwide. We can also observe sudden decrease in methane concentration during the World War I and World War II. It implies that the industrial revolution has dominated the atmospheric greenhouse gas emission for about 100 years. Besides, the average methane concentration in the Himalayan <span class="hlt">ice</span> core is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B33I0591K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B33I0591K"><span>Development and evaluation of <span class="hlt">ice</span> phenology algorithm from space-borne active and passive microwave measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, K.; Duguay, C. R.</p> <p>2013-12-01</p> <p>The presence (or absence) of <span class="hlt">ice</span> <span class="hlt">cover</span> plays an important role in lake-atmosphere interactions at high latitudes during the winter months. Knowledge of <span class="hlt">ice</span> phenology (i.e. freeze-onset/melt-onset, <span class="hlt">ice-on/ice</span>-off dates, and <span class="hlt">ice</span> <span class="hlt">cover</span> duration) is crucial for understanding both the role of lake <span class="hlt">ice</span> <span class="hlt">cover</span> in and its response to regional weather and climate. Shortening of the <span class="hlt">ice</span> <span class="hlt">cover</span> season in many regions of the Northern Hemisphere over recent decades has been shown to significantly influence the thermal regime as well as the water quality and quantity of lakes. In this respect, satellite remote sensing instruments are providing invaluable measurements for monitoring changes in timing of <span class="hlt">ice</span> phenological events and the length of the <span class="hlt">ice</span> <span class="hlt">cover</span> (or open water) season on large northern lakes, and also for providing more spatially representative limnological information than available from in situ measurements. In this study, we present a new <span class="hlt">ice</span> phenology retrieval algorithm developed from the synergistic use of Quick Scatterometer (QuikSCAT), Oceansat-2 Scatterometer (OSCAT) and the Advanced Microwave Scanning Radiometer (AMSR-E). Retrieved <span class="hlt">ice</span> dates are then evaluated against those derived from the NOAA Interactive Multisensor Snow and <span class="hlt">Ice</span> Mapping System (IMS) 4 km resolution product (2004-2011) during the freeze-up and break-up periods (2002-2012) for 11 lakes (Amadjuak, Nettilling, Great Bear, Great Slave, Manitoba, and Winnipeg in North America as well as Inarijrvi, Ladoga, Onega, Qinghai (Koko Nor), and Baikal in Eurasia). In addition, daily wind speed derived from QuikSCAT/OSCAT is analyzed along with WindSAT surface wind vector products (2002-2012) during the open water season for the large lakes. A detailed evaluation of the new algorithm conducted over Great Slave Lake (GSL) and Great Bear Lake (GBL) reveals that estimated <span class="hlt">ice-on/ice</span>-off dates are within 4-7 days of those derived from the IMS product. Preliminary analysis of <span class="hlt">ice</span> dates show that <span class="hlt">ice</span>-on occurs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15772652','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15772652"><span>Tropical to mid-latitude snow and <span class="hlt">ice</span> accumulation, flow and glaciation on Mars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Head, J W; Neukum, G; Jaumann, R; Hiesinger, H; Hauber, E; Carr, M; Masson, P; Foing, B; Hoffmann, H; Kreslavsky, M; Werner, S; Milkovich, S; van Gasselt, S</p> <p>2005-03-17</p> <p>Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the <span class="hlt">base</span> of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely <span class="hlt">ice</span>-rich glacier-like viscous flow and sublimation. Together with new evidence for recent <span class="hlt">ice</span>-rich rock glaciers at the <span class="hlt">base</span> of the Olympus Mons scarp superposed on larger Late Amazonian debris-<span class="hlt">covered</span> piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar <span class="hlt">ice</span> was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual <span class="hlt">ice</span> probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70029180','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70029180"><span>Tropical to mid-latitude snow and <span class="hlt">ice</span> accumulation, flow and glaciation on Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Head, J.W.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; Hoffmann, H.; Kreslavsky, M.; Werner, S.; Milkovich, S.; Van Gasselt, S.</p> <p>2005-01-01</p> <p>Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the <span class="hlt">base</span> of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely <span class="hlt">ice</span>-rich glacier-like viscous flow and sublimation. Together with new evidence for recent <span class="hlt">ice</span>-rich rock glaciers at the <span class="hlt">base</span> of the Olympus Mons scarp superposed on larger Late Amazonian debris-<span class="hlt">covered</span> piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar <span class="hlt">ice</span> was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual <span class="hlt">ice</span> probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNS21C..07H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNS21C..07H"><span>Airborne geophysics for mesoscale observations of polar sea <span class="hlt">ice</span> in a changing climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hendricks, S.; Haas, C.; Krumpen, T.; Eicken, H.; Mahoney, A. R.</p> <p>2016-12-01</p> <p>Sea <span class="hlt">ice</span> thickness is an important geophysical parameter with a significant impact on various processes of the polar energy balance. It is classified as Essential Climate Variable (ECV), however the direct observations of the large <span class="hlt">ice-covered</span> oceans are limited due to the harsh environmental conditions and logistical constraints. Sea-<span class="hlt">ice</span> thickness retrieval by the means of satellite remote sensing is an active field of research, but current observational capabilities are not able to capture the small scale variability of sea <span class="hlt">ice</span> thickness and its evolution in the presence of surface melt. We present an airborne observation system <span class="hlt">based</span> on a towed electromagnetic induction sensor that delivers long range measurements of sea <span class="hlt">ice</span> thickness for a wide range of sea <span class="hlt">ice</span> conditions. The purpose-built sensor equipment can be utilized from helicopters and polar research aircraft in multi-role science missions. While airborne EM induction sounding is used in sea <span class="hlt">ice</span> research for decades, the future challenge is the development of unmanned aerial vehicle (UAV) platform that meet the requirements for low-level EM sea <span class="hlt">ice</span> surveys in terms of range and altitude of operations. The use of UAV's could enable repeated sea <span class="hlt">ice</span> surveys during the the polar night, when manned operations are too dangerous and the observational data <span class="hlt">base</span> is presently very sparse.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C42B..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C42B..03D"><span>Assessing deformation and morphology of Arctic landfast sea <span class="hlt">ice</span> using InSAR to support use and management of coastal <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dammann, D. O.; Eicken, H.; Meyer, F. J.; Mahoney, A. R.</p> <p>2016-12-01</p> <p>Arctic landfast sea <span class="hlt">ice</span> provides important services to people, including coastal communities and industry, as well as key marine biota. In many regions of the Arctic, the use of landfast sea <span class="hlt">ice</span> by all stakeholders is increasingly limited by reduced stability of the <span class="hlt">ice</span> <span class="hlt">cover</span>, which results in more deformation and rougher <span class="hlt">ice</span> conditions as well as reduced extent and an increased likelihood of detachment from the shore. Here, we use Synthetic Aperture Radar Interferometry (InSAR) to provide stakeholder-relevant data on key constraints for sea <span class="hlt">ice</span> use, in particular <span class="hlt">ice</span> stability and morphology, which are difficult to assess using conventional SAR. InSAR has the capability to detect small-scale landfast <span class="hlt">ice</span> displacements, which are linked to important coastal hazards, including the formation of cracks, ungrounding of <span class="hlt">ice</span> pressure ridges, and catastrophic breakout events. While InSAR has previously been used to identify the extent of landfast <span class="hlt">ice</span> and regions of deformation within, quantitative analysis of small-scale <span class="hlt">ice</span> motion has yet to be thoroughly validated and its potential remains largely underutilized in sea <span class="hlt">ice</span> science. Using TanDEM-X interferometry, we derive surface displacements of landfast <span class="hlt">ice</span> within Elson Lagoon near Barrow, Alaska, which we validate using in-situ DGPS data. We then apply an inverse model to estimate rates and patterns of shorefast <span class="hlt">ice</span> deformation in other regions of landfast <span class="hlt">ice</span> using interferograms generated with long-temporal baseline L-band ALOS-1 PALSAR-1 data. The model is able to correctly identify deformation modes and proxies for the associated relative internal elastic stress. The derived potential for fractures corresponds well with large-scale sea <span class="hlt">ice</span> patterns and local in-situ observations. The utility of InSAR to quantify sea <span class="hlt">ice</span> roughness has also been explored using TanDEM-X bistatic interferometry, which eliminates the effects of temporal changes in the <span class="hlt">ice</span> <span class="hlt">cover</span>. The InSAR-derived DEM shows good correlation with a high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3365033','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3365033"><span>Pre-Partum Diet of Adult Female Bearded Seals in Years of Contrasting <span class="hlt">Ice</span> Conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hindell, Mark A.; Lydersen, Christian; Hop, Haakon; Kovacs, Kit M.</p> <p>2012-01-01</p> <p>Changing patterns of sea-<span class="hlt">ice</span> distribution and extent have measurable effects on polar marine systems. Beyond the obvious impacts of key-habitat loss, it is unclear how such changes will influence <span class="hlt">ice</span>-associated marine mammals in part because of the logistical difficulties of studying foraging behaviour or other aspects of the ecology of large, mobile animals at sea during the polar winter. This study investigated the diet of pregnant bearded seals (Erignathus barbatus) during three spring breeding periods (2005, 2006 and 2007) with markedly contrasting <span class="hlt">ice</span> conditions in Svalbard using stable isotopes (δ13C and δ15N) measured in whiskers collected from their newborn pups. The δ15N values in the whiskers of individual seals ranged from 11.95 to 17.45 ‰, spanning almost 2 full trophic levels. Some seals were clearly dietary specialists, despite the species being characterised overall as a generalist predator. This may buffer bearded seal populations from the changes in prey distributions lower in the marine food web which seems to accompany continued changes in temperature and <span class="hlt">ice</span> <span class="hlt">cover</span>. Comparisons with isotopic signatures of known prey, suggested that benthic gastropods and decapods were the most common prey. Bayesian isotopic mixing models indicated that diet varied considerably among years. In the year with most fast-<span class="hlt">ice</span> (2005), the seals had the greatest proportion of pelagic fish and lowest benthic invertebrate content, and during the year with the least <span class="hlt">ice</span> (2006), the seals ate more benthic invertebrates and less pelagic fish. This suggests that the seals fed further offshore in years with greater <span class="hlt">ice</span> <span class="hlt">cover</span>, but moved in to the fjords when <span class="hlt">ice-cover</span> was minimal, giving them access to different types of prey. Long-term trends of sea <span class="hlt">ice</span> decline, earlier <span class="hlt">ice</span> melt, and increased water temperatures in the Arctic are likely to have ecosystem-wide effects, including impacts on the forage <span class="hlt">bases</span> of pagophilic seals. PMID:22693616</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22693616','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22693616"><span>Pre-partum diet of adult female bearded seals in years of contrasting <span class="hlt">ice</span> conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hindell, Mark A; Lydersen, Christian; Hop, Haakon; Kovacs, Kit M</p> <p>2012-01-01</p> <p>Changing patterns of sea-<span class="hlt">ice</span> distribution and extent have measurable effects on polar marine systems. Beyond the obvious impacts of key-habitat loss, it is unclear how such changes will influence <span class="hlt">ice</span>-associated marine mammals in part because of the logistical difficulties of studying foraging behaviour or other aspects of the ecology of large, mobile animals at sea during the polar winter. This study investigated the diet of pregnant bearded seals (Erignathus barbatus) during three spring breeding periods (2005, 2006 and 2007) with markedly contrasting <span class="hlt">ice</span> conditions in Svalbard using stable isotopes (δ(13)C and δ(15)N) measured in whiskers collected from their newborn pups. The δ(15)N values in the whiskers of individual seals ranged from 11.95 to 17.45 ‰, spanning almost 2 full trophic levels. Some seals were clearly dietary specialists, despite the species being characterised overall as a generalist predator. This may buffer bearded seal populations from the changes in prey distributions lower in the marine food web which seems to accompany continued changes in temperature and <span class="hlt">ice</span> <span class="hlt">cover</span>. Comparisons with isotopic signatures of known prey, suggested that benthic gastropods and decapods were the most common prey. Bayesian isotopic mixing models indicated that diet varied considerably among years. In the year with most fast-<span class="hlt">ice</span> (2005), the seals had the greatest proportion of pelagic fish and lowest benthic invertebrate content, and during the year with the least <span class="hlt">ice</span> (2006), the seals ate more benthic invertebrates and less pelagic fish. This suggests that the seals fed further offshore in years with greater <span class="hlt">ice</span> <span class="hlt">cover</span>, but moved in to the fjords when <span class="hlt">ice-cover</span> was minimal, giving them access to different types of prey. Long-term trends of sea <span class="hlt">ice</span> decline, earlier <span class="hlt">ice</span> melt, and increased water temperatures in the Arctic are likely to have ecosystem-wide effects, including impacts on the forage <span class="hlt">bases</span> of pagophilic seals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1216F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1216F"><span>Under-<span class="hlt">ice</span> melt ponds and the oceanic mixed layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flocco, D.; Smith, N.; Feltham, D. L.</p> <p>2017-12-01</p> <p>Under-<span class="hlt">ice</span> melt ponds are pools of freshwater beneath the Arctic sea <span class="hlt">ice</span> that form when melt from the surface of the sea <span class="hlt">ice</span> percolates down through the porous sea <span class="hlt">ice</span>. Through double diffusion, a sheet of <span class="hlt">ice</span> can form at the interface between the ocean and the under-<span class="hlt">ice</span> melt pond, completely isolating the pond from the mixed layer below and forming a false bottom to the sea <span class="hlt">ice</span>. As such, they insulate the sea <span class="hlt">ice</span> from the ocean below. It has been estimated that these ponds could <span class="hlt">cover</span> between 5 and 40 % of the <span class="hlt">base</span> of the Arctic sea <span class="hlt">ice</span>, and so could have a notable impact on the mass balance of the sea <span class="hlt">ice</span>. We have developed a one-dimensional model to calculate the thickness and thermodynamic properties of a slab of sea <span class="hlt">ice</span>, an under-<span class="hlt">ice</span> melt pond, and a false bottom, as these layers evolve. Through carrying out sensitivity studies, we have identified a number of interesting ways that under-<span class="hlt">ice</span> melt ponds affect the <span class="hlt">ice</span> above them and the rate of basal ablation. We found that they result in thicker sea <span class="hlt">ice</span> above them, due to their insulation of the <span class="hlt">ice</span>, and have found a possible positive feedback cycle in which less <span class="hlt">ice</span> will be gained due to under-<span class="hlt">ice</span> melt ponds as the Arctic becomes warmer. More recently, we have coupled this model to a simple Kraus-Turner type model of the oceanic mixed layer to investigate how these ponds affect the ocean water beneath them. Through altering basal ablation rates and <span class="hlt">ice</span> thickness, they change the fresh water and salt fluxes into the mixed layer, as well as incoming radiation. Multi-year simulations have, in particular, shown how these effects work on longer time-scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860038376&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmarginal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860038376&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmarginal"><span>Coupled <span class="hlt">ice</span>-ocean dynamics in the marginal <span class="hlt">ice</span> zones Upwelling/downwelling and eddy generation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, S.</p> <p>1986-01-01</p> <p>This study is aimed at modeling mesoscale processes such as upwelling/downwelling and <span class="hlt">ice</span> edge eddies in the marginal <span class="hlt">ice</span> zones. A two-dimensional coupled <span class="hlt">ice</span>-ocean model is used for the study. The <span class="hlt">ice</span> model is coupled to the reduced gravity ocean model through interfacial stresses. The parameters of the ocean model were chosen so that the dynamics would be nonlinear. The model was tested by studying the dynamics of upwelling. Wings parallel to the <span class="hlt">ice</span> edge with the <span class="hlt">ice</span> on the right produce upwelling because the air-<span class="hlt">ice</span> momentum flux is much greater than air-ocean momentum flux; thus the Ekman transport is greater than the <span class="hlt">ice</span> than in the open water. The stability of the upwelling and downwelling jets is discussed. The downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence. The constant wind field exerted on a varying <span class="hlt">ice</span> <span class="hlt">cover</span> will generate vorticity leading to enhanced upwelling/downwelling regions, i.e., wind-forced vortices. Steepening and strengthening of vortices are provided by the nonlinear terms. When forcing is time-varying, the advection terms will also redistribute the vorticity. The wind reversals will separate the vortices from the <span class="hlt">ice</span> edge, so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140003875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140003875"><span>Modeling Commercial Turbofan Engine <span class="hlt">Icing</span> Risk With <span class="hlt">Ice</span> Crystal Ingestion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jorgenson, Philip C. E.; Veres, Joseph P.</p> <p>2013-01-01</p> <p>The occurrence of <span class="hlt">ice</span> accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to <span class="hlt">ice</span> crystal ingestion, partially melting, and <span class="hlt">ice</span> accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As <span class="hlt">ice</span> crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the <span class="hlt">ice</span> crystals to melt. It is hypothesized that this allows the <span class="hlt">ice</span>-water mixture to <span class="hlt">cover</span> the metal surfaces of the compressor stationary components which leads to <span class="hlt">ice</span> accretion through evaporative cooling. <span class="hlt">Ice</span> accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine <span class="hlt">icing</span> computational tool to simulate the flow through a turbofan engine and assess the risk of <span class="hlt">ice</span> accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an <span class="hlt">ice</span> particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual <span class="hlt">ice</span> accretion. A commercial turbofan engine which has previously experienced <span class="hlt">icing</span> events during operation in a high altitude <span class="hlt">ice</span> crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous <span class="hlt">ice</span> cloud which are ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was <span class="hlt">ice</span> accretion in the engine due to <span class="hlt">ice</span> crystal ingestion, at the same simulated altitude operating conditions as experienced previously in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29291835','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29291835"><span><span class="hlt">Ice</span> cream structure modification by <span class="hlt">ice</span>-binding proteins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kaleda, Aleksei; Tsanev, Robert; Klesment, Tiina; Vilu, Raivo; Laos, Katrin</p> <p>2018-04-25</p> <p><span class="hlt">Ice</span>-binding proteins (IBPs), also known as antifreeze proteins, were added to <span class="hlt">ice</span> cream to investigate their effect on structure and texture. <span class="hlt">Ice</span> recrystallization inhibition was assessed in the <span class="hlt">ice</span> cream mixes using a novel accelerated microscope assay and the <span class="hlt">ice</span> cream microstructure was studied using an <span class="hlt">ice</span> crystal dispersion method. It was found that adding recombinantly produced fish type III IBPs at a concentration 3 mg·L -1 made <span class="hlt">ice</span> cream hard and crystalline with improved shape preservation during melting. <span class="hlt">Ice</span> creams made with IBPs (both from winter rye, and type III IBP) had aggregates of <span class="hlt">ice</span> crystals that entrapped pockets of the <span class="hlt">ice</span> cream mixture in a rigid network. Larger individual <span class="hlt">ice</span> crystals and no entrapment in control <span class="hlt">ice</span> creams was observed. <span class="hlt">Based</span> on these results a model of <span class="hlt">ice</span> crystals aggregates formation in the presence of IBPs was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.sciencedirect.com/science/article/pii/S0165232X13001730','USGSPUBS'); return false;" href="http://www.sciencedirect.com/science/article/pii/S0165232X13001730"><span>Reconstruction of historic sea <span class="hlt">ice</span> conditions in a sub-Arctic lagoon</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Petrich, Chris; Tivy, Adrienne C.; Ward, David H.</p> <p>2014-01-01</p> <p>Historical sea <span class="hlt">ice</span> conditions were reconstructed for Izembek Lagoon, Bering Sea, Alaska. This lagoon is a crucial staging area during migration for numerous species of avian migrants and a major eelgrass (Zostera marina) area important to a variety of marine and terrestrial organisms, especially Pacific Flyway black brant geese (Branta bernicla nigricans). <span class="hlt">Ice</span> <span class="hlt">cover</span> is a common feature of the lagoon in winter, but appears to be declining, which has implications for eelgrass distribution and abundance, and its use by wildlife. We evaluated <span class="hlt">ice</span> conditions from a model <span class="hlt">based</span> on degree days, calibrated to satellite observations, to estimate distribution and long-term trends in <span class="hlt">ice</span> conditions in Izembek Lagoon. Model results compared favorably with ground observations and 26 years of satellite data, allowing <span class="hlt">ice</span> conditions to be reconstructed back to 1943. Specifically, periods of significant (limited access to eelgrass areas) and severe (almost complete <span class="hlt">ice</span> coverage of the lagoon) <span class="hlt">ice</span> conditions could be identified. The number of days of severe <span class="hlt">ice</span> within a single season ranged from 0 (e.g., 2001) to ≥ 67 (e.g., 2000). We detected a slight long-term negative trend in <span class="hlt">ice</span> conditions, superimposed on high inter-annual variability in seasonal aggregate <span class="hlt">ice</span> conditions. <span class="hlt">Based</span> on reconstructed <span class="hlt">ice</span> conditions, the seasonally cumulative number of significant or severe <span class="hlt">ice</span> days correlated linearly with mean air temperature from January until March. Further, air temperature at Izembek Lagoon was correlated with wind direction, suggesting that <span class="hlt">ice</span> conditions in Izembek Lagoon were associated with synoptic-scale weather patterns. Methods employed in this analysis may be transferable to other coastal locations in the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010027899','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010027899"><span>Studies of Antarctic Sea <span class="hlt">Ice</span> Concentrations from Satellite Data and Their Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Steffen, Konrad; Zukor, Dorothy J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Large changes in the sea <span class="hlt">ice</span> <span class="hlt">cover</span> have been observed recently. Because of the relevance of such changes to climate change studies it is important that key <span class="hlt">ice</span> concentration data sets used for evaluating such changes are interpreted properly. High and medium resolution visible and infrared satellite data are used in conjunction with passive microwave data to study the true characteristics of the Antarctic sea <span class="hlt">ice</span> <span class="hlt">cover</span>, assess errors in currently available <span class="hlt">ice</span> concentration products, and evaluate the applications and limitations of the latter in polar process studies. Cloud-free high resolution data provide valuable information about the natural distribution, stage of formation, and composition of the <span class="hlt">ice</span> <span class="hlt">cover</span> that enables interpretation of the large spatial and temporal variability of the microwave emissivity of Antarctic sea <span class="hlt">ice</span>. Comparative analyses of co-registered visible, infrared and microwave data were used to evaluate <span class="hlt">ice</span> concentrations derived from standard <span class="hlt">ice</span> algorithms (i.e., Bootstrap and Team) and investigate the 10 to 35% difference in derived values from large areas within the <span class="hlt">ice</span> pack, especially in the Weddell Sea, Amundsen Sea, and Ross Sea regions. Landsat and OLS data show a predominance of thick consolidated <span class="hlt">ice</span> in these areas and show good agreement with the Bootstrap Algorithm. While direct measurements were not possible, the lower values from the Team Algorithm results are likely due to layering within the <span class="hlt">ice</span> and snow and/or surface flooding, which are known to affect the polarization ratio. In predominantly new <span class="hlt">ice</span> regions, the derived <span class="hlt">ice</span> concentration from passive microwave data is usually lower than the true percentage because the emissivity of new <span class="hlt">ice</span> changes with age and thickness and is lower than that of thick <span class="hlt">ice</span>. However, the product provides a more realistic characterization of the sea <span class="hlt">ice</span> <span class="hlt">cover</span>, and are more useful in polar process studies since it allows for the identification of areas of significant divergence and polynya</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www1.ncdc.noaa.gov/pub/data/cmb/bams-sotc/climate-assessment-2004.pdf','USGSPUBS'); return false;" href="http://www1.ncdc.noaa.gov/pub/data/cmb/bams-sotc/climate-assessment-2004.pdf"><span>Polar Climate: Arctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stone, R.S.; Douglas, David C.; Belchansky, G.I.; Drobot, S.D.</p> <p>2005-01-01</p> <p>Recent decreases in snow and sea <span class="hlt">ice</span> <span class="hlt">cover</span> in the high northern latitudes are among the most notable indicators of climate change. Northern Hemisphere sea <span class="hlt">ice</span> extent for the year as a whole was the third lowest on record dating back to 1973, behind 1995 (lowest) and 1990 (second lowest; Hadley Center–NCEP). September sea <span class="hlt">ice</span> extent, which is at the end of the summer melt season and is typically the month with the lowest sea <span class="hlt">ice</span> extent of the year, has decreased by about 19% since the late 1970s (Fig. 5.2), with a record minimum observed in 2002 (Serreze et al. 2003). A record low extent also occurred in spring (Chapman 2005, personal communication), and 2004 marked the third consecutive year of anomalously extreme sea <span class="hlt">ice</span> retreat in the Arctic (Stroeve et al. 2005). Some model simulations indicate that <span class="hlt">ice</span>-free summers will occur in the Arctic by the year 2070 (ACIA 2004).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP11B1783E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP11B1783E"><span>An unusual early Holocene diatom event north of the Getz <span class="hlt">Ice</span> Shelf (Amundsen Sea): Implications for West Antarctic <span class="hlt">Ice</span> Sheet development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esper, O.; Gersonde, R.; Hillenbrand, C.; Kuhn, G.; Smith, J.</p> <p>2011-12-01</p> <p>Modern global change affects not only the polar north but also, and to increasing extent, the southern high latitudes, especially the Antarctic regions <span class="hlt">covered</span> by the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS). Consequently, knowledge of the mechanisms controlling past WAIS dynamics and WAIS behaviour at the last deglaciation is critical to predict its development in a future warming world. Geological and palaeobiological information from major drainage areas of the WAIS, like the Amundsen Sea Embayment, shed light on the history of the WAIS glaciers. Sediment records obtained from a deep inner shelf basin north of Getz <span class="hlt">Ice</span> Shelf document a deglacial warming in three phases. Above a glacial diamicton and a sediment package barren of microfossils that document sediment deposition by grounded <span class="hlt">ice</span> and below an <span class="hlt">ice</span> shelf or perennial sea <span class="hlt">ice</span> <span class="hlt">cover</span> (possibly fast <span class="hlt">ice</span>), respectively, a sediment section with diatom assemblages dominated by sea <span class="hlt">ice</span> taxa indicates <span class="hlt">ice</span> shelf retreat and seasonal <span class="hlt">ice</span>-free conditions. This conclusion is supported by diatom-<span class="hlt">based</span> summer temperature reconstructions. The early retreat was followed by a phase, when exceptional diatom ooze was deposited around 12,500 cal. years B.P. [1]. Microscopical inspection of this ooze revealed excellent preservation of diatom frustules of the species Corethron pennatum together with vegetative Chaetoceros, thus an assemblage usually not preserved in the sedimentary record. Sediments succeeding this section contain diatom assemblages indicating rather constant Holocene cold water conditions with seasonal sea <span class="hlt">ice</span>. The deposition of the diatom ooze can be related to changes in hydrographic conditions including strong advection of nutrients. However, sediment focussing in the partly steep inner shelf basins cannot be excluded as a factor enhancing the thickness of the ooze deposits. It is not only the presence of the diatom ooze but also the exceptional preservation and the species composition of the diatom assemblage</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27441129','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27441129"><span>On twelve types of <span class="hlt">covering-based</span> rough sets.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Safari, Samira; Hooshmandasl, Mohammad Reza</p> <p>2016-01-01</p> <p><span class="hlt">Covering</span> approximation spaces are a generalization of equivalence-<span class="hlt">based</span> rough set theories. In this paper, we will consider twelve types of <span class="hlt">covering</span> <span class="hlt">based</span> approximation operators by combining four types of <span class="hlt">covering</span> lower approximation operators and three types of <span class="hlt">covering</span> upper approximation operators. Then, we will study the properties of these new pairs and show they have most of the common properties among existing <span class="hlt">covering</span> approximation pairs. Finally, the relation between these new pairs is studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000039366&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DParkinsons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000039366&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DParkinsons"><span>Changes in the Areal Extent of Arctic Sea <span class="hlt">Ice</span>: Observations from Satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>2000-01-01</p> <p>Wintertime sea <span class="hlt">ice</span> <span class="hlt">covers</span> 15 million square kilometers of the north polar region, an area exceeding one and a half times the area of the U. S. Even at the end of the summer melt season, sea <span class="hlt">ice</span> still <span class="hlt">covers</span> 7 million square kilometers. This vast <span class="hlt">ice</span> <span class="hlt">cover</span> is an integral component of the climate system, being moved around by winds and waves, restricting heat and other exchanges between the ocean and atmosphere, reflecting most of the solar radiation incident on it, transporting cold, relatively fresh water equatorward, and affecting the overturning of ocean waters underneath, with impacts that can be felt worldwide. Sea <span class="hlt">ice</span> also is a major factor in the Arctic ecosystem, affecting life forms ranging from minute organisms living within the <span class="hlt">ice</span>, sometimes to the tune of millions in a single <span class="hlt">ice</span> floe, to large marine mammals like walruses that rely on sea <span class="hlt">ice</span> as a platform for resting, foraging, social interaction, and breeding. Since 1978, satellite technology has allowed the monitoring of the vast Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> on a routine basis. The satellite observations reveal that, overall, the areal extent of Arctic sea <span class="hlt">ice</span> has been decreasing since 1978, at an average rate of 2.7% per decade through the end of 1998. Through 1998, the greatest rates of decrease occurred in the Seas of Okhotsk and Japan and the Kara and Barents Seas, with most other regions of the Arctic also experiencing <span class="hlt">ice</span> extent decreases. The two regions experiencing <span class="hlt">ice</span> extent increases over this time period were the Bering Sea and the Gulf of St. Lawrence. Furthermore, the satellite data reveal that the sea <span class="hlt">ice</span> season shortened by over 25 days per decade in the central Sea of Okhotsk and the eastern Barents Sea, and by lesser amounts throughout much of the rest of the Arctic seasonal sea <span class="hlt">ice</span> region, although not in the Bering Sea or the Gulf of St. Lawrence. Concern has been raised that if the trends toward shortened sea <span class="hlt">ice</span> seasons and lesser sea <span class="hlt">ice</span> coverage continue, this could entail major</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70073649','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70073649"><span>New eyes in the sky measure glaciers and <span class="hlt">ice</span> sheets</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kieffer, Hugh; Kargel, Jeffrey S.; Barry, Roger G.; Bindschadler, Robert; Bishop, Michael P.; MacKinnon, David; Ohmura, Atsumu; Raup, Bruce; Antoninetti, Massimo; Bamber, Jonathan; Braun, Mattias; Brown, Ian; Cohen, Denis; Copland, Luke; DueHagen, Jon; Engeset, Rune V.; Fitzharris, Blair; Fujita, Koji; Haeberli, Wilfried; Hagen, Jon Oue; Hall, Dorothy; Hoelzle, Martin; Johansson, Maria; Kaab, Andi; Koenig, Max; Konovalov, Vladimir; Maisch, Max; Paul, Frank; Rau, Frank; Reeh, Niels; Rignot, Eric; Rivera, Andres; De Ruyter de Wildt, Martiyn; Scambos, Ted; Schaper, Jesko; Scharfen, Greg; Shroder, Jack; Solomina, Olga; Thompson, David; van der Veen, Kees; Wohlleben, Trudy; Young, Neal</p> <p>2000-01-01</p> <p>The mapping and measurement of glaciers and their changes are useful in predicting sea-level and regional water supply, studying hazards and climate change [Haeberli et al., 1998],and in the hydropower industry Existing inventories <span class="hlt">cover</span> only about 67,000 of the world's estimated 160,000 glaciers and are <span class="hlt">based</span> on data collected over 50 years or more [e.g.,Haeberli et al., 1998]. The data available have proven that small <span class="hlt">ice</span> bodies are disappearing at an accelerating rate and that the Antarctic <span class="hlt">ice</span> sheet and its fringing <span class="hlt">ice</span> shelves are undergoing unexpected, rapid change. According to many glaciologists, much larger fluctuations in land ice—with vast implications for society—are possible in the coming decades and centuries due to natural and anthropogenic climate change [Oppenheimer, 1998].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DParkinsons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=Parkinsons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DParkinsons"><span>Variability of Arctic Sea <span class="hlt">Ice</span> as Determined from Satellite Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>1999-01-01</p> <p>The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea <span class="hlt">ice</span> now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea <span class="hlt">ice</span> <span class="hlt">cover</span> and its variability. The information includes data on <span class="hlt">ice</span> concentrations (percent areal coverages of <span class="hlt">ice</span>), <span class="hlt">ice</span> extents, <span class="hlt">ice</span> melt, <span class="hlt">ice</span> velocities, the seasonal cycle of the <span class="hlt">ice</span>, the interannual variability of the <span class="hlt">ice</span>, the frequency of <span class="hlt">ice</span> coverage, and the length of the sea <span class="hlt">ice</span> season. The data reveal marked regional and interannual variabilities, as well as some statistically significant trends. For the north polar <span class="hlt">ice</span> <span class="hlt">cover</span> as a whole, maximum <span class="hlt">ice</span> extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum <span class="hlt">ice</span> coverage. In spite of the large variations from year to year and region to region, overall the Arctic <span class="hlt">ice</span> extents showed a statistically significant, 2.80% / decade negative trend over the 18.2-year period. <span class="hlt">Ice</span> season lengths, which vary from only a few weeks near the <span class="hlt">ice</span> margins to the full year in the large region of perennial <span class="hlt">ice</span> coverage, also experienced interannual variability, along with spatially coherent overall trends. Linear least squares trends show the sea <span class="hlt">ice</span> season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0805G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0805G"><span>In situ validation of segmented SAR satellite scenes of young Arctic thin landfast sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gerland, S.; Negrel, J.; Doulgeris, A. P.; Akbari, V.; Lauknes, T. R.; Rouyet, L.; Storvold, R.</p> <p>2016-12-01</p> <p>The use of satellite remote sensing techniques for the observation and monitoring of the polar regions has increased in recent years due to the ability to <span class="hlt">cover</span> larger areas than can be <span class="hlt">covered</span> by ground measurements, However, in situ data remain mandatory for the validation of such data. In April 2016 an Arctic fieldwork campaign was conducted at Kongsfjorden, Svalbard. Ground measurements from this campaign are used together with satellite data acquisitions to improve identification of young sea <span class="hlt">ice</span> types from satellite data. This work was carried out in combination with Norwegian Polar Institute's long-term monitoring of Svalbard fast <span class="hlt">ice</span>, and with partner institutes in the Center for Integrated Remote Sensing and Forecasting for Arctic operations (CIRFA). Thin <span class="hlt">ice</span> types are generally more difficult to investigate than thicker <span class="hlt">ice</span>, because <span class="hlt">ice</span> of only a few centimetres thickness does not allow scientists to stand and work on it. Identifying it on radar scenes will make it easier to study and monitor. Four high resolution 25 km x 25 km Radarsat-2 quad-pol scenes were obtained, coincident in space and time with the in situ measurements. The field teams used a variety of methods, including <span class="hlt">ice</span> thickness transects, <span class="hlt">ice</span> salinity measurements, ground-<span class="hlt">based</span> radar imaging from the coast and UAV-<span class="hlt">based</span> photography, to identify the different thin <span class="hlt">ice</span> types, their location and evolution in time. Sampling of the thinnest <span class="hlt">ice</span> types was managed from a small boat. In addition, iceberg positions were recorded with GPS and photographed to enable us to quantify their contribution to the radar response. Thin <span class="hlt">ice</span> from 0.02 to 0.18 m thickness was sampled on in a total nine <span class="hlt">ice</span> stations. The <span class="hlt">ice</span> had no or only a thin snow layer. The GPS positions and tracks and <span class="hlt">ice</span> characteristics are then compared to the Radarsat-2 scenes, and the radar responses of the different thin <span class="hlt">ice</span> types in the quad-pol scenes are identified. The first segmentation results of the scenes present a good</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914888H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914888H"><span>Stress and deformation characteristics of sea <span class="hlt">ice</span> in a high resolution numerical sea <span class="hlt">ice</span> model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heorton, Harry; Feltham, Daniel; Tsamados, Michel</p> <p>2017-04-01</p> <p>The drift and deformation of sea <span class="hlt">ice</span> floating on the polar oceans is due to the applied wind and ocean currents. The deformations of sea <span class="hlt">ice</span> over ocean basin length scales have observable patterns; cracks and leads in satellite images and within the velocity fields generated from floe tracking. In a climate sea <span class="hlt">ice</span> model the deformation of sea <span class="hlt">ice</span> over ocean basin length scales is modelled using a rheology that represents the relationship between stresses and deformation within the sea <span class="hlt">ice</span> <span class="hlt">cover</span>. Here we investigate the link between observable deformation characteristics and the underlying internal sea <span class="hlt">ice</span> stresses and force balance using the Los Alamos numerical sea <span class="hlt">ice</span> climate model. In order to mimic laboratory experiments on the deformation of small cubes of sea <span class="hlt">ice</span> we have developed an idealised square domain that tests the model response at spatial resolutions of up to 500m. We use the Elastic Anisotropic Plastic and Elastic Viscous Plastic rheologies, comparing their stability over varying resolutions and time scales. Sea <span class="hlt">ice</span> within the domain is forced by idealised winds in order to compare the confinement of wind stresses and internal sea <span class="hlt">ice</span> stresses. We document the characteristic deformation patterns of convergent, divergent and rotating stress states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70014695','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70014695"><span>Remote sensing of the Fram Strait marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shuchman, R.A.; Burns, B.A.; Johannessen, O.M.; Josberger, E.G.; Campbell, W.J.; Manley, T.O.; Lannelongue, N.</p> <p>1987-01-01</p> <p>Sequential remote sensing images of the Fram Strait marginal <span class="hlt">ice</span> zone played a key role in elucidating the complex interactions of the atmosphere, ocean, and sea <span class="hlt">ice</span>. Analysis of a subset of these images <span class="hlt">covering</span> a 1-week period provided quantitative data on the mesoscale <span class="hlt">ice</span> morphology, including <span class="hlt">ice</span> edge positions, <span class="hlt">ice</span> concentrations, floe size distribution, and <span class="hlt">ice</span> kinematics. The analysis showed that, under light to moderate wind conditions, the morphology of the marginal <span class="hlt">ice</span> zone reflects the underlying ocean circulation. High-resolution radar observations showed the location and size of ocean eddies near the <span class="hlt">ice</span> edge. <span class="hlt">Ice</span> kinematics from sequential radar images revealed an ocean eddy beneath the interior pack <span class="hlt">ice</span> that was verified by in situ oceanographic measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11809961','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11809961"><span>Antarctic Sea <span class="hlt">ice</span>--a habitat for extremophiles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomas, D N; Dieckmann, G S</p> <p>2002-01-25</p> <p>The pack <span class="hlt">ice</span> of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an <span class="hlt">ice</span> matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-<span class="hlt">ice</span> organisms thrive in the <span class="hlt">ice</span>, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea <span class="hlt">ice</span> have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on <span class="hlt">ice-covered</span> extraterrestrial bodies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41A0639L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41A0639L"><span>Upper Ocean Evolution Across the Beaufort Sea Marginal <span class="hlt">Ice</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, C.; Rainville, L.; Gobat, J. I.; Perry, M. J.; Freitag, L. E.; Webster, S.</p> <p>2016-12-01</p> <p>The observed reduction of Arctic summertime sea <span class="hlt">ice</span> extent and expansion of the marginal <span class="hlt">ice</span> zone (MIZ) have profound impacts on the balance of processes controlling sea <span class="hlt">ice</span> evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer and Atlantic waters), and elevated surface wave energy that acts to deform and fracture sea <span class="hlt">ice</span>. Spatial and temporal variability in <span class="hlt">ice</span> properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing <span class="hlt">ice</span> <span class="hlt">cover</span>, how the balance of processes shift as a function of <span class="hlt">ice</span> fraction and distance from open water, and how these processes impact sea <span class="hlt">ice</span> evolution, a network of autonomous platforms sampled the atmosphere-<span class="hlt">ice</span>-ocean system in the Beaufort, beginning in spring, well before the start of melt, and ending with the autumn freeze-up. Four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal <span class="hlt">ice</span> zone, deep into the pack during summer 2014 in the Beaufort Sea. Gliders penetrated up to 200 km into the <span class="hlt">ice</span> pack, under complete <span class="hlt">ice</span> <span class="hlt">cover</span> for up to 10 consecutive days. Sections reveal strong fronts where cold, <span class="hlt">ice-covered</span> waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the <span class="hlt">ice</span> edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse late in the season as they progress through the MIZ and into open water. Stratification just above the Pacific Summer Water rapidly weakens near the <span class="hlt">ice</span> edge and temperature variance increases, likely due to mixing or energetic vertical exchange associated with strong</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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