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Sample records for seasonal ice zone

  1. Contrasts in Sea Ice Deformation and Production in the Arctic Seasonal and Perennial Ice Zones

    NASA Technical Reports Server (NTRS)

    Kwok, K.

    2006-01-01

    Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. Three-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the midwinter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is seen in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m): this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. Uncertainties in these estimates are discussed. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice. Divergence is shown to be negligibly correlated to cyclonic motion in summer and winter in both ice zones.

  2. Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

    NASA Technical Reports Server (NTRS)

    Kwok, R.

    2006-01-01

    Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

  3. A microwave technique for mapping ice temperature in the Arctic seasonal sea ice zone

    SciTech Connect

    St. Germain, K.M.; Cavalieri, D.J.

    1997-07-01

    A technique for deriving ice temperature in the Arctic seasonal sea ice zone from passive microwave radiances has been developed. The algorithm operates on brightness temperatures derived from the Special Sensor Microwave/Imager (SSM/I) and uses ice concentration and type from a previously developed thin ice algorithm to estimate the surface emissivity. Comparisons of the microwave derived temperatures with estimates derived from infrared imagery of the Bering Strait yield a correlation coefficient of 0.93 and an RMS difference of 2.1 K when coastal and cloud contaminated pixels are removed. SSM/I temperatures were also compared with a time series of air temperature observations from Gambell on St. Lawrence Island and from Point Barrow, AK weather stations. These comparisons indicate that the relationship between the air temperature and the ice temperature depends on ice type.

  4. Characteristics of Arctic Ocean ice determined from SMMR data for 1979 - Case studies in the seasonal sea ice zone

    NASA Technical Reports Server (NTRS)

    Anderson, M. R.; Crane, R. G.; Barry, R. G.

    1985-01-01

    Sea ice data derived from the Scanning Multichannel Microwave Radiometer are examined for sections of the Arctic Ocean during early summer 1979. The temporary appearance of spuriously high multiyear ice fractions in the seasonal ice zones of the Kara and Barents Seas is a result of surface melt phenomena and the relative responses of the different channels to these effects. These spurious signatures can provide early identification of melt onset and additional information on surface characteristics.

  5. Seasonal changes of ice surface characteristics and productivity in the ablation zone of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Chandler, D. M.; Alcock, J. D.; Wadham, J. L.; Mackie, S. L.; Telling, J.

    2015-03-01

    Field and remote sensing observations in the ablation zone of the Greenland Ice Sheet have revealed a diverse range of ice surface characteristics, primarily reflecting the variable distribution of fine debris (cryoconite). This debris reduces the surface albedo and is therefore an important control on melt rates and ice sheet mass balance. Meanwhile, studies of ice sheet surface biological processes have found active microbial communities associated with the cryoconite debris, which may themselves modify the cryoconite distribution. Due to the considerable difficulties involved with collecting ground-based observations of the ice surface, our knowledge of the physical and biological surface processes, and their links, remains very limited. Here we present data collected at a field camp established in the ice sheet ablation zone at 67° N, occupied for almost the entire melt season (26 May-10 August 2012), with the aim of gaining a much more detailed understanding of the physical and biological processes occurring on the ice surface. These data sets include quadrat surveys of surface type, measurements of ice surface ablation, and in situ biological oxygen demand incubations to quantify microbial activity. In addition, albedo at the site was retrieved from AVHRR (Advanced Very High Resolution Radiometer) remote sensing data. Observations of the areal coverage of different surface types revealed a rapid change from complete snow cover to the "summer" (summer study period) ice surface of patchy debris ("dirty ice") and cryoconite holes. There was significant correlation between surface albedo, cryoconite hole coverage and surface productivity during the melt season, but microbial activity in "dirty ice" was not correlated with albedo and varied widely throughout the season. While this link suggests the potential for a remote-sensing approach to monitoring cryoconite hole biological processes, very wide seasonal and spatial variability in net surface productivity

  6. Seasonal changes of ice surface characteristics and productivity in the ablation zone of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Chandler, D. M.; Alcock, J. D.; Wadham, J. L.; Mackie, S. L.; Telling, J.

    2014-02-01

    Field and remote sensing observations in the ablation zone of the Greenland Ice Sheet have revealed a diverse range of ice surface characteristics, primarily reflecting the variable distribution of fine debris (cryoconite). This debris reduces the surface albedo and is therefore an important control on melt rates and ice sheet mass balance. Meanwhile, studies of ice sheet surface biological processes have found active microbial communities associated with the cryoconite debris, which may themselves modify the cryoconite distribution. Due to the considerable difficulties involved with collecting ground-based observations of the ice surface, our knowledge of the physical and biological surface processes, and their links, remains very limited. Here we present data collected at a field camp established in the ice sheet ablation zone at 67° N, occupied for almost the entire melt season (26 May-10 August 2012), with the aim of gaining a much more detailed understanding of the physical and biological processes occurring on the ice surface. These data sets include quadrat surveys of surface type, measurements of ice surface ablation, and in-situ biological oxygen demand incubations to quantify microbial activity. In addition, albedo at the site was retrieved from AVHRR remote sensing data. Observations of the areal coverage of different surface types revealed a rapid change from complete snow cover to the "summer" ice surface of patchy debris ("dirty ice") and cryoconite holes. There was significant correlation between surface albedo, cryoconite hole coverage and cryoconite hole productivity during the main melt season, but microbial activity in "dirty ice" was not correlated with albedo and varied widely throughout the season. While this link suggests the potential for a remote-sensing approach to monitoring cryoconite hole biological processes, very wide seasonal and spatial variability in net surface productivity demonstrates the need for caution when extrapolating

  7. Aerial Surveys of the Beaufort Sea Seasonal Ice Zone in 2012-2014

    NASA Astrophysics Data System (ADS)

    Dewey, S.; Morison, J.; Andersen, R.; Zhang, J.

    2014-12-01

    Seasonal Ice Zone Reconnaissance Surveys (SIZRS) of the Beaufort Sea aboard U.S. Coast Guard Arctic Domain Awareness flights were made monthly from May 2012 to October 2012, June 2013 to August 2013, and June 2014 to October 2014. In 2012 sea ice extent reached a record minimum and the SIZRS sampling ranged from complete ice cover to open water; in addition to its large spatial coverage, the SIZRS program extends temporal coverage of the seasonal ice zone (SIZ) beyond the traditional season for ship-based observations, and is a good set of measurements for model validation and climatological comparison. The SIZ, where ice melts and reforms annually, encompasses the marginal ice zone (MIZ). Thus SIZRS tracks interannual MIZ conditions, providing a regional context for smaller-scale MIZ processes. Observations with Air eXpendable CTDs (AXCTDs) reveal two near-surface warm layers: a locally-formed surface seasonal mixed layer and a layer of Pacific origin at 50-60m. Temperatures in the latter differ from the freezing point by up to 2°C more than climatologies. To distinguish vertical processes of mixed layer formation from Pacific advection, vertical heat and salt fluxes are quantified using a 1-D Price-Weller-Pinkel (PWP) model adapted for ice-covered seas. This PWP simulates mixing processes in the top 100m of the ocean. Surface forcing fluxes are taken from the Marginal Ice Zone Modeling and Assimilation System MIZMAS. Comparison of SIZRS observations with PWP output shows that the ocean behaves one-dimensionally above the Pacific layer of the Beaufort Gyre. Despite agreement with the MIZMAS-forced PWP, SIZRS observations remain fresher to 100m than do outputs from MIZMAS and ECCO.2. The shapes of seasonal cycles in SIZRS salinity and temperature agree with MIZMAS and ECCO.2 model outputs despite differences in the values of each. However, the seasonal change of surface albedo is not high enough resolution to accurately drive the PWP. Use of ice albedo

  8. A Comparison of Sea Ice Type, Sea Ice Temperature, and Snow Thickness Distributions in the Arctic Seasonal Ice Zones with the DMSP SSM/I

    NASA Technical Reports Server (NTRS)

    St.Germain, Karen; Cavalieri, Donald J.; Markus, Thorsten

    1997-01-01

    Global climate studies have shown that sea ice is a critical component in the global climate system through its effect on the ocean and atmosphere, and on the earth's radiation balance. Polar energy studies have further shown that the distribution of thin ice and open water largely controls the distribution of surface heat exchange between the ocean and atmosphere within the winter Arctic ice pack. The thickness of the ice, the depth of snow on the ice, and the temperature profile of the snow/ice composite are all important parameters in calculating surface heat fluxes. In recent years, researchers have used various combinations of DMSP SSMI channels to independently estimate the thin ice type (which is related to ice thickness), the thin ice temperature, and the depth of snow on the ice. In each case validation efforts provided encouraging results, but taken individually each algorithm gives only one piece of the information necessary to compute the energy fluxes through the ice and snow. In this paper we present a comparison of the results from each of these algorithms to provide a more comprehensive picture of the seasonal ice zone using passive microwave observations.

  9. The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink

    PubMed Central

    Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

    2015-01-01

    Reduced surface–deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface–subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring–summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall–winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink. PMID:26382319

  10. The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink

    NASA Astrophysics Data System (ADS)

    Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

    2015-09-01

    Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

  11. The Weddell-Scotia marginal ice zone: Physical oceanographic conditions, geographical and seasonal variability

    NASA Astrophysics Data System (ADS)

    Muench, R. D.; Huber, B. A.; Gunn, J. T.; Husby, D. M.; Mountain, D. G.

    1992-03-01

    Physical oceanographic conditions were measured in the Weddell and Scotia Sea marginal ice zones (MIZ's) during 1983, 1986 and 1988. The field work encompassed spring, autumn and mid-winter periods and included retreating, advancing and steady-state ice edges. Observed upper ocean structures, which typify MIZ's and reflect input of low salinity water from melting ice, included low salinity upper layers, lenses and fronts. An upper mixed layer was always present and was generally more fully developed in autumn and winter than at other times of year. Conditions in the deeper waters reflected regional oceanographic processes and significant differences were present between the Weddell and Scotia seas. Weddell Sea Water is a major source of water for the southern Scotia Sea, however, the upper Scotia Sea was dominated by warmer, less saline waters from Drake Passage. The colder, denser Weddell water appeared to have mixed isopycnally with deeper water in the Scotia Sea, present there at depths exceeding 500 m. The Scotia Sea was dominated by strong gradients and energetic mesoscale features, with currents exceeding 50 cm/s. The northwestern Weddell Sea had, in contrast, current speeds well below about 5 cm/s and small to negligible lateral water property gradients. Our observations suggest that the Weddell western boundary current was weaker than has been estimated in the past. In addition, we found scant evidence of deep winter convection in the Scotia Sea, a process which has been hypothesized in the past to contribute to deep water formation. No evidence was found during winter 1988 in the Scotia Sea of the modified water known as Weddell-Scotia Confluence water.

  12. Modeling the Seasonal Ice Zone from the Air: use of repeat aerial hydrographic surveys to constrain a regional ice-ocean model in an area of rapidly evolving ice cover

    NASA Astrophysics Data System (ADS)

    Dewey, S.; Morison, J.; Zhang, J.

    2015-12-01

    The Seasonal Ice Zone of the Beaufort Sea is the area of ocean north of Alaska over which sea ice melts and reforms annually. It contains the more narrow, near-edge marginal ice zone (MIZ). Seasonal Ice Zone Reconnaissance Surveys (SIZRS) measure hydrography along two meridional sections using Air eXpendable CTDs (AXCTDs) and Air eXpendable Current Profilers (AXCPs). These surveys take place aboard U.S. Coast Guard Arctic Domain Awareness flights of opportunity during each melt season (June-October) starting in 2012. The Marginal Ice Zone Modeling and Assimilation System (MIZMAS) is a high-resolution regional ice-ocean model with daily, three-dimensional output encompassing the SIZRS survey area. Direct comparison of the SIZRS data with MIZMAS output as well as with several regional climatologies can constrain the ice-ocean model and help to explain recent changes in subsurface heat content and salinity. For example, observed freshening relative to climatology has been used as a reference to which MIZMAS surface salinity values can be relaxed. MIZMAS may in turn shed light on the physical mechanisms driving the observed freshening. In addition, use of MIZMAS surface fluxes to drive a one-dimensional mixed layer model gives results close to observations when the model is initialized with SIZRS profiles. Because SIZRS observations range in time from the onset of melt to the onset of Fall freeze-up, the comparison of the one-dimensional model with MIZMAS illustrates the relative roles of local and regional processes in forming near-surface temperature maxima and salinity minima. The SIZRS observations and one-dimensional model are used to constrain MIZMAS estimations of stored subsurface heat while establishing the physical drivers of these temperature and salinity changes.

  13. Color Reveals Translucent Seasonal Ice

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Figure 1

    In a region near the south pole of Mars translucent carbon dioxide ice covers the ground seasonally. For the first time we can 'see' the translucent ice by the affect it has on the appearance of the surface below.

    Dark fans of dust (figure 1) from the surface drape over the top of the seasonal ice. The surface would be the same color as the dust except that the seasonal ice affecting its appearance. Bright bluish streaks are frost that has re-crystallized from the atmosphere.

    Sunlight can penetrate through the seasonal layer of translucent ice to warm the ground below. That causes the seasonal ice layer to sublime (evaporate) from the bottom rather than the top.

    Observation Geometry Image PSP_002942_0935 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 13-Mar-2007. The complete image is centered at -86.4 degrees latitude, 99.2 degrees East longitude. The range to the target site was 245.4 km (153.4 miles). At this distance the image scale is 49.1 cm/pixel (with 2 x 2 binning) so objects 147 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel . The image was taken at a local Mars time of 06:41 PM and the scene is illuminated from the west with a solar incidence angle of 82 degrees, thus the sun was about 8 degrees above the horizon. At a solar longitude of 199.6 degrees, the season on Mars is Northern Autumn.

  14. Physical and biological control of protistan community composition, distribution and abundance in the seasonal ice zone of the Southern Ocean between 30 and 80°E

    NASA Astrophysics Data System (ADS)

    Davidson, Andrew T.; Scott, Fiona J.; Nash, Geraldine V.; Wright, Simon W.; Raymond, Ben

    2010-05-01

    Protists are critical components of the Antarctic marine ecosystem as they comprise most of the living carbon and are the base of the Antarctic food web. They are also key determinants of vertical carbon flux and mediate draw-down of atmospheric CO 2 by the ocean. The community composition, abundance and distribution of marine protists (phytoplankton and protozoa) was studied during the Baseline Research on Oceanography, Krill and the Environment-West (BROKE-West) survey, in the seasonal ice zone during the 2005-2006 austral summer between 30°E and 80°E. Light and electron microscopy were used to determine the protistan composition and abundance in samples obtained at 30 sites from surface waters and at 26 sites from the depth of the maximum in situ chlorophyll fluorescence (Chl max). Cluster analysis was used to identify 5 groups of sample sites at the surface and 5 at the Chl max that were of similar protist composition and abundance. The physical characteristics, taxonomic composition, indicator taxa, and taxonomic diversity were determined for each group. In the southwest, a bloom of colonial Phaeocystis antarctica dominated the protistan community composition and biomass amongst the receding ice, but this was replaced by the flagellate life stage/s of this haptophyte in waters to the north. In the southeast, a diatom bloom had the highest diversity of protist taxa observed during the survey and centric diatoms dominated the biomass. Outside these blooms, grazing by krill probably reduced the composition and abundance of large diatoms and autotrophic dinoflagellates in coastal to mid-inshore waters. Only in offshore waters did large diatoms and dinoflagellates increase in abundance and diversity, despite low concentrations of iron and silicate at many of these sites. This increase was probably due to reduced top-down control by krill and other large zooplankton. Large diatoms dominated in offshore waters, despite other coincident studies showing that the

  15. Solar radiation interactions with seasonal sea ice

    NASA Astrophysics Data System (ADS)

    Ehn, Jens Kristian

    Presently, the Arctic Ocean is undergoing an escalating reduction in sea ice and a transition towards a seasonal sea ice environment. This warrants detailed investigations into improving our understanding of the seasonal evolution of sea ice and snow covers, and their representation in climate models. The interaction of solar radiation with sea ice is an important process influencing the energy balance and biological activity in polar seas, and consequently plays a key role in the earth's climate system. This thesis focuses on characterization of the optical properties---and the underlying physical properties that determine them---of seasonal sea ice during the fall freeze-up and the spring melt periods. Both periods display high spatial heterogeneity and rapid temporal changes in sea ice properties, and are therefore poorly understood. Field data were collected in Amundsen Gulf/Franklin Bay (FB), southern-eastern Beaufort Sea, in Oct.-Nov. 2003 and Apr. 2004 and in Button Bay (BB), western Hudson Bay, in Mar.-May 2005 to address (1) the temporal and spatial evolution of surface albedo and transmittance, (2) how radiative transfer in sea ice is controlled by its physical nature, and (3) the characteristics of the bottom ice algae community and its effect on the optical properties. The fall study showed the importance of surface features such as dry or slushy bare ice, frost flowers and snow cover in determining the surface albedo. Ice thickness was also important, however, mostly because surface features were associated with thickness. For example, nilas (<10 cm thick) was typically not covered by a snow layer as snow grains were dissolved or merged with the salty and warm brine skim layer on the surface, while surface conditions on thicker ice types were cold and dry enough to support a snow cover. In general, the surface albedo increased exponentially with an ice thickness increase, however, variability within ice thickness types were very large. It is apparent

  16. Seasonal Changes of Arctic Sea Ice Physical Properties Observed During N-ICE2015: An Overview

    NASA Astrophysics Data System (ADS)

    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.

    2015-12-01

    Arctic sea ice is changing, and for improving the understanding of the cryosphere, data is needed to describe the status and processes controlling current seasonal sea ice growth, change and decay. We present preliminary results from in-situ observations on sea ice 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 ice floes, drifting with the sea ice and allowing an international group of scientists to conduct detailed research. Each drift lasted until the ship reached the marginal ice zone and ice 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 covered measurements in the atmosphere, the snow and sea ice system, and in the ocean, as well as biological studies, in this presentation we focus on physics of snow and sea ice. Different ice types could be investigated: young ice in refrozen leads, first year ice, and old ice. Snow surveys included regular snow pits with standardized measurements of physical properties and sampling. Snow and ice thickness were measured at stake fields, along transects with electromagnetics, and in drillholes. For quantifying ice physical properties and texture, ice cores were obtained regularly and analyzed. Optical properties of snow and ice 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 (ice 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 based radar altimetry. The analysis of the data collected has started, and first results will be

  17. Remote sensing of the marginal ice zone during Marginal Ice Zone Experiment (MIZEX) 83

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Campbell, W. J.; Burns, B. A.; Ellingsen, E.; Farrelly, B. A.; Gloersen, P.; Grenfell, T. C.; Hollinger, J.; Horn, D.; Johannessen, J. A.

    1984-01-01

    The remote sensing techniques utilized in the Marginal Ice Zone Experiment (MIZEX) to study the physical characteristics and geophysical processes of the Fram Strait Region of the Greenland Sea are described. The studies, which utilized satellites, aircraft, helicopters, and ship and ground-based remote sensors, focused on the use of microwave remote sensors. Results indicate that remote sensors can provide marginal ice zone characteristics which include ice edge and ice boundary locations, ice types and concentration, ice deformation, ice kinematics, gravity waves and swell (in the water and the ice), location of internal wave fields, location of eddies and current boundaries, surface currents and sea surface winds.

  18. Variability in the Antarctic Marginal Ice Zone and Pack Ice in Observations and NCAR CESM

    NASA Astrophysics Data System (ADS)

    Stroeve, J. C.; Campbell, G. G.; Holland, M. M.; Landrum, L.

    2015-12-01

    Sea ice around Antarctica reached another record high extent in September 2014, recording a maximum extent of more than 20 million km2 for the first time since the modern satellite data record began in October 1978. This follows previous record maxima in 2012 and 2013, resulting in an overall increase in Antarctic September sea ice extent of 1.3% per decade since 1979. Several explanations have been put forward to explain the increasing trends, such as anomalous short-term wind patterns that both grow and spread out the ice, and freshening of the surface ocean layer from increased melting of floating ice from the continent. These positive trends in Antarctic sea ice are at odds with climate model forecasts that suggest the sea ice should be declining in response to increasing greenhouse gases and stratospheric ozone depletion. While the reasons for the increases in total extent remain poorly understood, it is likely that these changes are not just impacting the total ice extent, but also the distribution of pack ice, the marginal ice zone (MIZ) and polynyas, with important ramifications for phytoplankton productivity that in turn impact zooplankton, fish, sea birds and marine mammals. This study evaluates changes in the distribution of the pack ice, polynyas and the marginal ice zone around Antarctica from two sea ice algorithms, the NASA Team and the Bootstrap. These results are further compared with climate model simulations from the CESM large ensemble output. Seasonal analysis of the different ice types using NASA Team and Bootstrap shows that during ice advance, the ice advances as pack ice, with a seasonal peak in September (broader peak for Bootstrap), and as the pack ice begins to retreat, it first converts to a wide area of MIZ, that reaches its peak around November (NASA Team) or December (Bootstrap). CESM also shows a similar seasonal cycle, with a peak in the pack ice in August, and a December/January peak in the MIZ. Seasonal variability and trends are

  19. Mapping and Assessing Variability in the Antarctic Marginal Ice Zone, the Pack Ice and Coastal Polynyas

    NASA Astrophysics Data System (ADS)

    Stroeve, Julienne; Jenouvrier, Stephanie

    2016-04-01

    Sea ice variability within the marginal ice 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 ice types to the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover 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 ice types. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depends strongly on what sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice 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 ice characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.

  20. Spatially Mapped Reductions in the Length of the Arctic Sea Ice Season

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2014-01-01

    Satellite data are used to determine the number of days having sea ice coverage in each year 1979-2013 and to map the trends in these ice-season lengths. Over the majority of the Arctic seasonal sea ice zone, the ice season shortened at an average rate of at least 5 days/decade between 1979 and 2013, and in a small area in the northeastern Barents Sea the rate of shortening reached over 65 days/decade. The only substantial non-coastal area with lengthening sea ice seasons is the Bering Sea, where the ice season lengthened by 5-15 days/decade. Over the Arctic as a whole, the area with ice seasons shortened by at least 5 days/decade is 12.4 × 10(exp 6) square kilimeters, while the area with ice seasons lengthened by at least 5 days/decade is only 1.1 × 10(exp 6) square kilometers. The contrast is even greater, percentage-wise, for higher rates.

  1. MIZMAS Forecast of Sea Ice Thickness and Drift in the Beaufort Sea Marginal Ice Zone

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Schweiger, A. J. B.; Steele, M.; Stern, H. L., III

    2014-12-01

    A significant decline of Arctic sea ice has been observed in recent years. The decline was particularly steep during summers 2007-2013, when the arctic sea ice extent decreased to the lowest levels observed in the satellite era. The summer melt back was most severe in the Pacific sector including the Beaufort Sea where increasing areas of warming open water and marginal ice zone (MIZ) have been observed. To enhance our understanding of MIZ processes, an Office of Naval Research MIZ initiative is under way, which is an integrated program of observations and numerical simulations to investigate ice-ocean-atmosphere dynamics in and around the Beaufort Sea MIZ. In early 2014, the observation team of this program deployed 4 clusters of instruments of various platforms in the Beaufort Sea in order to capture the processes that affect MIZ evolution during the ice melt season. To assist the field work, we have developed a numerical framework for 48-hour forecast of sea ice thickness and drift in and around the Beaufort Sea MIZ using the Marginal Ice Zone ice/ocean Modeling and Assimilation System (MIZMAS). MIZMAS is a variant of the Pan-arctic Ice/Ocean Modeling and Assimilation System (PIOMAS), with a high-resolution focus of the Chukchi, Beaufort, and Bering seas. The 48-hour sea ice forecast system is forced by the forecast atmospheric data from the NCEP (National Center for Environmental Prediction) Climate Forecast System version 2 (CFSv2). The CFSv2 forecast ranges from hours to months and the forecast atmospheric data are widely accessible, thus ideal for forcing our sea ice forecast over a range of time scales. The sea ice forecast system has been used to predict sea ice thickness in the Beaufort Sea MIZ 48 hours in advance, focusing on the areas around the 4 clusters. It has also been used to predict the movement of these clusters. In this presentation, we will assess MIZMAS' forecast skills by comparing available ice thickness observations and the actual cluster

  2. Modeling Wave-Ice Interactions in the Marginal Ice Zone

    NASA Astrophysics Data System (ADS)

    Orzech, Mark; Shi, Fengyan; Bateman, Sam; Veeramony, Jay; Calantoni, Joe

    2015-04-01

    The small-scale (O(m)) interactions between waves and ice floes in the marginal ice zone (MIZ) are investigated with a coupled model system. Waves are simulated with the non-hydrostatic finite-volume model NHWAVE (Ma et al., 2012) and ice floes are represented as bonded collections of smaller particles with the discrete element system LIGGGHTS (Kloss et al., 2012). The physics of fluid and ice are recreated as authentically as possible, to allow the coupled system to supplement and/or substitute for more costly and demanding field experiments. The presentation will first describe the development and validation of the coupled system, then discuss the results of a series of virtual experiments in which ice floe and wave characteristics are varied to examine their effects on energy dissipation, MIZ floe size distribution, and ice pack retreat rates. Although Wadhams et al. (1986) suggest that only a small portion (roughly 10%) of wave energy entering the MIZ is reflected, dissipation mechanisms for the remaining energy have yet to be delineated or measured. The virtual experiments are designed to focus on specific properties and processes - such as floe size and shape, collision and fracturing events, and variations in wave climate - and measure their relative roles the transfer of energy and momentum from waves to ice. Questions to be examined include: How is energy dissipated by ice floe collisions, fracturing, and drag, and how significant is the wave attenuation associated with each process? Do specific wave/floe length scale ratios cause greater wave attenuation? How does ice material strength affect the rate of wave energy loss? The coupled system will ultimately be used to test and improve upon wave-ice parameterizations for large-scale climate models. References: >Kloss, C., C. Goniva, A. Hager, S. Amberger, and S. Pirker (2012). Models, algorithms and validation for opensource DEM and CFD-DEM. Progress in Computational Fluid Dynamics 12(2/3), 140-152. >Ma, G

  3. Change and Variability in East Antarctic Sea Ice Seasonality, 1979/80–2009/10

    PubMed Central

    Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

    2013-01-01

    Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors. PMID:23705008

  4. The Influence of the Zonal Wave Three on Antarctic Sea Ice during Ice Advance Season

    NASA Astrophysics Data System (ADS)

    Khan, H. M.; Raphael, M. N.

    2015-12-01

    Previous works have looked at the influence of key atmospheric circulation patterns on sea ice in the Antarctic in terms of the atmosphere's seasonal cycle. This study examines the influence of one of these atmospheric patterns, the zonal wave three (ZW3), in terms of the sea ice's seasons from 1979-2009 in order to better understand the response of the sea ice. An index to represent the amplitude of the ZW3 was calculated using zonal anomalies of 850 hPa geopotential heights taken from the ERA-Interim data set. Sea ice concentrations (SIC), taken from the Hadley Center sea ice and sea surface temperature data set, were found to be significantly positively correlated with the ZW3 index during the ice advance season (March to August) in the Ross and Weddell Seas and off the Amery ice shelf. These regions align with where cold, southerly flow associated with the ZW3 are found. In the Amundsen-Bellingshausen Seas region, SIC was found to be negatively correlated with the ZW3 index, which coincides with where the warm, northerly flow of the wave is found in this region. Regression analysis showed SIC to be significantly dependent upon the ZW3 in parts of the Ross Sea, the ice edge in the Amundsen-Bellingshausen Seas and off the Amery ice shelf during ice advance season. The results suggest that the ZW3 plays a role in the occurrence of the observed sea ice trends in the Ross Sea, Amundsen-Bellingshausen Seas, Weddell Sea and off the Amery ice shelf regions during the ice advance season, the critical period for sea ice growth. The results also demonstrate that re-examining the influence of relevant atmospheric patterns on sea ice in terms of the ice's seasonal cycles could allow firmer connections to be established between sea ice trends and atmospheric patterns.

  5. Determining the ice seasons severity during 1982-2015 using the ice extents sum as a new characteristic

    NASA Astrophysics Data System (ADS)

    Rjazin, Jevgeni; Pärn, Ove

    2016-04-01

    Sea ice is a key climate factor and it restricts considerably the winter navigation in sever seasons on the Baltic Sea. So determining ice conditions severity and describing ice cover behaviour at severe seasons interests scientists, engineers and navigation managers. The present study is carried out to determine the ice seasons severity degree basing on the ice seasons 1982 to 2015. A new integrative characteristic is introduced to describe the ice season severity. It is the sum of ice extents of the ice season id est the daily ice extents of the season are summed. The commonly used procedure to determine the ice season severity degree by the maximal ice extent is in this research compared to the new characteristic values. The remote sensing data on the ice concentrations on the Baltic Sea published in the European Copernicus Programme are used to obtain the severity characteristic values. The ice extents are calculated on these ice concentration data. Both the maximal ice extent of the season and a newly introduced characteristic - the ice 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 ice 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 ice cover in these three seasons. In several winters, for example 2010/11 ice cover extended enough for some time, but did not endure. At few other ice seasons as 2002/03 the Baltic Sea was ice-covered in moderate extent, but the ice cover stayed long time. At 11 winters the ice extents sum differed considerably (> 10%) from the maximal ice extent. These winters yield one third of the studied ice seasons. The maximal ice extent of the season is simple to use and enables to reconstruct the ice cover history and to predict maximal ice

  6. The Temporal Evolution of the Albedo of Seasonal Sea Ice

    NASA Astrophysics Data System (ADS)

    Perovich, D. K.; Polashenski, C.; Eicken, H.; Grenfell, T. C.

    2009-12-01

    The ice-albedo feedback mechanism plays a key role in the heat budget of the Arctic sea ice cover and has climate implications. Seasonal ice is now the dominant Arctic ice type and has a significant impact on the large-scale albedo. The albedo of shorefast, seasonal ice was measured from April through late June for five field seasons. There was considerable interannual variability in the seasonal evolution of albedo, and consequently the solar heat input to the ice and upper ocean. In one year there was a monotonic decrease in areally averaged albedo after the onset of melt, while in others there were significant fluctuations of up to 0.4 over periods of only a few days. For all of the different evolutionary pathways there were two key drivers of albedo; the timing of the onset of melt and the areal coverage of melt ponds. Melt ponds on undeformed seasonal ice have been observed to reach coverages as large as 80% in only a few days. Just as rapidly coverages have been observed to drop to 7% as the ponds drained. The evolution of melt ponds is the key to understanding the evolution of seasonal ice albedo during the early stages of melt.

  7. Impact of sea ice initialisation on sea ice and atmosphere prediction skill on seasonal timescales

    NASA Astrophysics Data System (ADS)

    Guemas, Virginie; Chevallier, Matthieu; Deque, Michel; Bellprat, Omar; Doblas-Reyes, Francisco; Fuckar, Neven-Stjepan

    2016-04-01

    We present a robust assessment of the impact of sea ice initialisation from observations on the sea ice and atmosphere prediction skill. We ran two ensemble seasonal prediction experiments from 1979 to 2012: one using the highest possible quality for sea ice initial conditions and another where sea ice is initialized from a climatology, with two forecast systems. During the freezing season in the Arctic Ocean, sea ice forecasts become skilful with sea ice initialization until three to five months ahead, thanks to the memory held by sea ice thickness. During the melting season in both the Arctic and Antarctic Oceans, sea ice forecasts are skilful for seven and two months respectively with negligible differences between the two experiments, the memory being held by the ocean heat content. A weak impact on the atmosphere prediction skill is obtained.

  8. Impact of sea ice initialization on sea ice and atmosphere prediction skill on seasonal timescales

    NASA Astrophysics Data System (ADS)

    Guemas, V.; Chevallier, M.; Déqué, M.; Bellprat, O.; Doblas-Reyes, F.

    2016-04-01

    We present a robust assessment of the impact of sea ice initialization from reconstructions of the real state on the sea ice and atmosphere prediction skill. We ran two ensemble seasonal prediction experiments from 1979 to 2012 : one using realistic sea ice initial conditions and another where sea ice is initialized from a climatology, with two forecast systems. During the melting season in the Arctic Ocean, sea ice forecasts become skilful with sea ice initialization until 3-5 months ahead, thanks to the memory held by sea ice thickness. During the freezing season in both the Arctic and Antarctic Oceans, sea ice forecasts are skilful for 7 and 2 months, respectively, with negligible differences between the two experiments, the memory being held by the ocean heat content. A weak impact on the atmosphere prediction skill is obtained.

  9. SIPEX--Exploring the Antarctic Sea Ice Zone

    ERIC Educational Resources Information Center

    Zicus, Sandra; Dobson, Jane; Worby, Anthony

    2008-01-01

    Sea ice in the polar regions plays a key role in both regulating global climate and maintaining marine ecosystems. The international Sea Ice Physics and Ecosystem eXperiment (SIPEX) explored the sea ice zone around Antarctica in September and October 2007, investigating relationships between the physical sea ice environment and the structure of…

  10. Waves and mesoscale features in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chih Y.

    1993-01-01

    Ocean-ice interaction processes in the Marginal Ice Zone (MIZ) by waves and mesoscale features, such as upwelling and eddies, are studied using ERS-1 Synthetic Aperture Radar (SAR) imagery and wave-ice interaction models. Satellite observations of mesoscale features can play a crucial role in ocean-ice interaction study.

  11. Seasonal change of antarctic sea ice cover.

    PubMed

    Gordon, A L; Taylor, H W

    1975-01-31

    The winter expansion of the sea ice surrounding Antarctica and the subsequent retreat of the ice in summer may be linked with the wind stress acting on the Southern Ocean in conjunction with the heat exchange in open water regions within the ice fields. PMID:17814267

  12. Will Arctic sea ice thickness initialization improve seasonal forecast skill?

    NASA Astrophysics Data System (ADS)

    Day, J. J.; Hawkins, E.; Tietsche, S.

    2014-11-01

    Arctic sea ice thickness is thought to be an important predictor of Arctic sea ice extent. However, coupled seasonal forecast systems do not generally use sea ice thickness observations in their initialization and are therefore missing a potentially important source of additional skill. To investigate how large this source is, a set of ensemble potential predictability experiments with a global climate model, initialized with and without knowledge of the sea ice thickness initial state, have been run. These experiments show that accurate knowledge of the sea ice thickness field is crucially important for sea ice concentration and extent forecasts up to 8 months ahead, especially in summer. Perturbing sea ice thickness also has a significant impact on the forecast error in Arctic 2 m temperature a few months ahead. These results suggest that advancing capabilities to observe and assimilate sea ice thickness into coupled forecast systems could significantly increase skill.

  13. CO2, CH4, and N2O in the Open Ocean, Sea-ice Zone, and Polynya of the Southern Ocean Observed during Austral Summer Season from 2009 to 2013

    NASA Astrophysics Data System (ADS)

    Rhee, T. S.; Park, K.; Hahm, D.; Jeon, H.; Park, K.; Kwon, Y.; Shin, H.; Lee, S.; Lee, K. E.

    2013-12-01

    Korean ice-breaking research vessel Araon has been at sea since 2010 carrying out a variety of research activities. During these periods we measured CO2, CH4, and N2O at sea below and above the sea surface to estimate sink or source strengths of the ocean in the characteristic provinces at high latitude. The ocean plays a wide range of role in the budget of these gases in the atmosphere: as a sink for CO2 and a source for CH4 and N2O. High latitude of the Southern Ocean is particularly important as the change in the cryosphere can impact the ecological and physical settings that govern the content and flux of these dissolved gases in seawater. We have visited the Amundsen Sea during the austral summer in 2010/2011 and 2012, and the Ross Sea in 2013 in order to investigate the impact of the change in the cryospheric environments. In addition we had opportunity to survey the Pacific sector of the Southern Ocean in 2009 onboard R/V Polarstern. In the open ocean, CO2 in the seawater was mostly undersaturated, CH4 was in equilibrium or slightly undersaturated, and N2O was supersaturated with respect to that in the marine boundary layer. These features were not observed in the sea-ice zone; CO2 in the seawater was slightly supersaturated in 2011, but not in 2012 and 2013, while dissolved CH4 was undersaturated and N2O was supersaturated for three years. In the polynya of the Amundsen Sea and the Ross Sea, CO2 and CH4 were undersaturated in the seawater while N2O was supersaturated with respect to that in the atmosphere. Based on these 4-year observations during austral summer season, high latitude of the southern ocean contributes as a strong sink for atmospheric CO2 whilst as a strong source for N2O. In the case of CH4, the Southern Ocean acted as a sink of the atmospheric CH4, which differs from the role of the ocean in the global scale.

  14. Seasonal evolution of melt ponds on Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Webster, Melinda A.; Rigor, Ignatius G.; Perovich, Donald K.; Richter-Menge, Jacqueline A.; Polashenski, Christopher M.; Light, Bonnie

    2015-09-01

    The seasonal evolution of melt ponds has been well documented on multiyear and landfast first-year sea ice, but is critically lacking on drifting, first-year sea ice, which is becoming increasingly prevalent in the Arctic. Using 1 m resolution panchromatic satellite imagery paired with airborne and in situ data, we evaluated melt pond evolution for an entire melt season on drifting first-year and multiyear sea ice near the 2011 Applied Physics Laboratory Ice Station (APLIS) site in the Beaufort and Chukchi seas. A new algorithm was developed to classify the imagery into sea ice, thin ice, melt pond, and open water classes on two contrasting ice types: first-year and multiyear sea ice. Surprisingly, melt ponds formed ˜3 weeks earlier on multiyear ice. Both ice types had comparable mean snow depths, but multiyear ice had 0-5 cm deep snow covering ˜37% of its surveyed area, which may have facilitated earlier melt due to its low surface albedo compared to thicker snow. Maximum pond fractions were 53 ± 3% and 38 ± 3% on first-year and multiyear ice, respectively. APLIS pond fractions were compared with those from the Surface Heat Budget of the Arctic Ocean (SHEBA) field campaign. APLIS exhibited earlier melt and double the maximum pond fraction, which was in part due to the greater presence of thin snow and first-year ice at APLIS. These results reveal considerable differences in pond formation between ice types, and underscore the importance of snow depth distributions in the timing and progression of melt pond formation.

  15. Environment at the Grounding Zone of the Whillans Ice Stream-Ross Ice Shelf, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.; Mikucki, J.; Scherer, R. P.; Tulaczyk, S. M.; Coenen, J. J.; Puttkammer, R.; Branecky, C.

    2015-12-01

    Grounding zones where grounded ice sheets transition to floating ice shelves, are the primary gateways through which the Antarctic Ice Sheet loses mass to the ocean. In these environments, ice, ocean, meltwater and sediment meet and interact, influencing both the ice sheet and ocean circulation beneath the ice shelf. Here, we report on conditions near the grounding zone of the Whillans Ice Stream, which feeds into the Ross Ice Shelf. Cameras and instruments lowered through an access borehole to the ocean cavity beneath the ice shelf found a 10m-thick water column comprising an upper layer of colder ice shelf water formed from mixing between meltwater with the lower layer of warmer higher salinity shelf water. This style of stratification is typical of large ice shelves, but it was uncertain whether it existed so near the grounding zone, where stronger tidal currents and/or strong subglacial stream discharges could mix the water column. Salinity and temperature of the water suggest it formed from sea ice production in the Western Ross Sea, with minimal modification beneath the ice shelf. This source region is distinct from waters previously observed at the nearby J-9 borehole, illustrating the importance of the sub-ice shelf bathymetry in steering circulation between the ocean and the grounding zone. Preliminary data suggest an active exchange of heat and nutrients between the grounding zone and the open ocean, despite being separated by 600km. Thus life found near the grounding line is probably not an isolated oasis, but may instead be part of a much broader ecosystem that spans the ice shelf. Although sea ice formation presently maintains water in the sub-ice shelf cavity near the surface freezing point, buffering many larger ice shelves from gradual ocean warming, these findings suggest that even grounding zones of extensive ice shelves may respond quickly to abrupt changes in ocean circulation, such as that observed in the Amundsen Sea.

  16. Skill improvement of dynamical seasonal Arctic sea ice forecasts

    NASA Astrophysics Data System (ADS)

    Krikken, Folmer; Schmeits, Maurice; Vlot, Willem; Guemas, Virginie; Hazeleger, Wilco

    2016-05-01

    We explore the error and improve the skill of the outcome from dynamical seasonal Arctic sea ice reforecasts using different bias correction and ensemble calibration methods. These reforecasts consist of a five-member ensemble from 1979 to 2012 using the general circulation model EC-Earth. The raw model reforecasts show large biases in Arctic sea ice area, mainly due to a differently simulated seasonal cycle and long term trend compared to observations. This translates very quickly (1-3 months) into large biases. We find that (heteroscedastic) extended logistic regressions are viable ensemble calibration methods, as the forecast skill is improved compared to standard bias correction methods. Analysis of regional skill of Arctic sea ice shows that the Northeast Passage and the Kara and Barents Sea are most predictable. These results show the importance of reducing model error and the potential for ensemble calibration in improving skill of seasonal forecasts of Arctic sea ice.

  17. Antarctic Sea ice variations and seasonal air temperature relationships

    NASA Technical Reports Server (NTRS)

    Weatherly, John W.; Walsh, John E.; Zwally, H. J.

    1991-01-01

    Data through 1987 are used to determine the regional and seasonal dependencies of recent trends of Antarctic temperature and sea ice. Lead-lag relationships involving regional sea ice and air temperature are systematically evaluated, with an eye toward the ice-temperature feedbacks that may influence climatic change. Over the 1958-1087 period the temperature trends are positive in all seasons. For the 15 years (l973-l987) for which ice data are available, the trends are predominantly positive only in winter and summer, and are most strongly positive over the Antarctic Peninsula. The spatially aggregated trend of temperature for this latter period is small but positive, while the corresponding trend of ice coverage is small but negative. Lag correlations between seasonal anomalies of the two variables are generally stronger with ice lagging the summer temperatures and with ice leading the winter temperatures. The implication is that summer temperatures predispose the near-surface waters to above-or below-normal ice coverage in the following fall and winter.

  18. JGR and marginal ice zone processes

    NASA Astrophysics Data System (ADS)

    As a follow-up to the special sessions on marginal ice zone (MIZ) processes at the AGU 1981 Fall Meeting in San Francisco and to sessions scheduled for the upcoming AGU/ASLO Meeting in San Antonio, a collection of papers on MIZ research is planned for the Journal of Geophysical Research.Tentative titles for manuscripts should be sent as soon as possible to Robin D. Muench, Coordinator JGR/MIZ Issue, SAI/Northwest, 13400B Northrup Way #36, Bellevue, WA 98005. Finished manuscripts, due April 1, 1982, should be sent directly to A.D. Kirwan, Jr., coeditor of JGR, Oceans and Atmospheres, Department of Marine Science, University of South Florida, 140 Seventh Ave. South, St. Petersburg, FL 33701. Authors are requested to specify that manuscripts are for the special MIZ issue.

  19. Selected physical, biological and biogeochemical implications of a rapidly changing Arctic Marginal Ice Zone

    NASA Astrophysics Data System (ADS)

    Barber, David G.; Hop, Haakon; Mundy, Christopher J.; Else, Brent; Dmitrenko, Igor A.; Tremblay, Jean-Eric; Ehn, Jens K.; Assmy, Philipp; Daase, Malin; Candlish, Lauren M.; Rysgaard, Søren

    2015-12-01

    The Marginal Ice Zone (MIZ) of the Arctic Ocean is changing rapidly due to a warming Arctic climate with commensurate reductions in sea ice extent and thickness. This Pan-Arctic review summarizes the main changes in the Arctic ocean-sea ice-atmosphere (OSA) interface, with implications for primary- and secondary producers in the ice and the underlying water column. Changes in the Arctic MIZ were interpreted for the period 1979-2010, based on best-fit regressions for each month. Trends of increasingly open water were statistically significant for each month, with quadratic fit for August-November, illustrating particularly strong seasonal feedbacks in sea-ice formation and decay. Geographic interpretations of physical and biological changes were based on comparison of regions with significant changes in sea ice: (1) The Pacific Sector of the Arctic Ocean including the Canada Basin and the Beaufort, Chukchi and East Siberian seas; (2) The Canadian Arctic Archipelago; (3) Baffin Bay and Hudson Bay; and (4) the Barents and Kara seas. Changes in ice conditions in the Barents sea/Kara sea region appear to be primarily forced by ocean heat fluxes during winter, whereas changes in the other sectors appear to be more summer-autumn related and primarily atmospherically forced. Effects of seasonal and regional changes in OSA-system with regard to increased open water were summarized for photosynthetically available radiation, nutrient delivery to the euphotic zone, primary production of ice algae and phytoplankton, ice-associated fauna and zooplankton, and gas exchange of CO2. Changes in the physical factors varied amongst regions, and showed direct effects on organisms linked to sea ice. Zooplankton species appear to be more flexible and likely able to adapt to variability in the onset of primary production. The major changes identified for the ice-associated ecosystem are with regard to production timing and abundance or biomass of ice flora and fauna, which are related to

  20. Seasonal Evolution of Snow Cover on Antarctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Maksym, T.; Leonard, K. C.; Trujillo, E.; White, S.; Wilkinson, J.; Stammerjohn, S. E.; Mei, J.

    2015-12-01

    Snow cover on Antarctic sea ice plays a key role in the evolution of ice thickness, its estimation from space-borne altimeters, and structuring of sea ice ecosystems. Yet until recently, there have been very few continuous observations of the seasonal evolution of snow cover on Antarctic sea ice. We present observations of the seasonal evolution of the snow cover from ice mass balance buoys (IMBs) deployed between 2009 and 2013 in the Weddell, Bellingshausen, and Amundsen Seas and the East Antarctic sector. In addition, automatic weather stations that provided direct observations of precipitation, accumulation, and blowing snow were deployed alongside IMBs in October, 2012 in the East Antarctic during the Sea Ice Physics and Ecosystem eXperiment II (SIPEX II), and in July and August, 2013 in the Weddell Sea during the Antarctic Winter Ecosystem and Climate Study (AWECS). These buoys show markedly different snow accumulation regimes in each sector, although accumulation is also strongly controlled by the local morphology of the ice cover through snow erosion and deposition during blowing snow and precipitations events. Comparisons of snow accumulation from these buoys with estimates from atmospheric reanalysis and the direct measurements of precipitation and blowing snow show that precipitation is generally not a good estimator of snow accumulation. Improved treatment of blowing snow is needed if sea ice models are to accurately simulate Antarctic snow and sea ice mass balance. In summer, melting of the snow pack is relatively modest in most cases. Nevertheless, it appears to play an important role in governing sea ice hydrology and sea ice surface properties, and hence may play an important role in modulating sea ice primary productivity.

  1. Seasonal precipitation timing and ice core records

    SciTech Connect

    Steig, E.J.; Grootes, P.M.; Stuiver, M. )

    1994-12-16

    This is a commentary on global circulation model experiments of moisture source changes in Greenland, urging caution in how they are applied because they have important implications for paleoclimate reconstruction from ice cores. The work comes from preliminary find is of a ice core (GISP2) of the authors. The authors conclude that at present anomalies in Greenland ice core records should not be interpreted solely in terms of source region variations. The combined use of oxygen 18, D and ionic species in the new Summit, Greenland cores should make it possible to answer empirically some of the questions raised by the GCM experiments as to the interpretation of oxygen 18 records in terms of temperature. 4 refs., 1 fig.

  2. The 2013 Arctic Field Season of the NRL Sea-Ice Measurement Program

    NASA Astrophysics Data System (ADS)

    Gardner, J. M.; Brozena, J. M.; Ball, D.; Hagen, R. A.; Liang, R.; Stoudt, C.

    2013-12-01

    The U.S. Naval Research Laboratory (NRL) is conducting a five year study of the changing Arctic with a particular focus on ice thickness and distribution variability with the intent of optimizing state-of-the-art computer models which are currently used to predict sea ice changes. An important part of our study is to calibrate/validate CryoSat2 ice thickness data prior to its incorporation into new ice forecast models. NRL Code 7420 collected coincident data with the CryoSat2 satellite in 2011 and 2012 using a LiDAR (Riegl Q560) to measure combined snow and ice thickness and a 10 GHz pulse-limited precision radar altimeter to measure sea-ice freeboard. This field season, LiDAR data was collected using the Riegl Q680 which permitted higher density operation and data collection. Concident radar data was collected using an improved version of the NRL 10 GHz pulse limited radar that was used for the 2012 fieldwork. 8 coincident tracks of CryoSat2 satellite data were collected. Additionally a series of grids (7 total) of adjacent tracks were flown coincident with Cryosat2 satellite overpass. These grids cover the approximate satellite footprint of the satellite on the ice as it passes overhead. Data from these grids are shown here and will be used to examine the relationship of the tracked satellite waveform data to the actual surface across the footprint. We also coordinated with the Seasonal Ice Zone Observing Network (SIZONet) group who conducted surface based ice thickness surveys using a Geonics EM-31 along hunter trails on the landfast ice near Barrow as well as on drifting ice offshore during helicopter landings. On two sorties, a twin otter carrying the NRL LiDAR and radar altimeter flew in tandem with the helicopter carrying the EM-31 to achieve synchronous data acquisition. Data from these flights are shown here along with a digital elevation map.

  3. Seasonal Greenland Ice Sheet ice flow variations in regions of differing bed and surface topography

    NASA Astrophysics Data System (ADS)

    Sole, A. J.; Livingstone, S. J.; Rippin, D. M.; Hill, J.; McMillan, M.; Quincey, D. J.

    2015-12-01

    The contribution of the Greenland Ice Sheet (GrIS) to future sea-level rise is uncertain. Observations reveal the important role of basal water in controlling ice-flow to the ice sheet margin. In Greenland, drainage of large volumes of surface meltwater to the ice sheet bed through moulins and hydrofracture beneath surface lakes dominates the subglacial hydrological system and provides an efficient means of moving mass and heat through the ice sheet. Ice surface and bed topography influence where meltwater can access the bed, and the nature of its subsequent flow beneath the ice. However, no systematic investigation into the influence of topographic variability on Greenland hydrology and dynamics exists. Thus, physical processes controlling storage and drainage of surface and basal meltwater, and the way these affect ice flow are not comprehensively understood. This presents a critical obstacle in efforts to predict the future evolution of the GrIS. Here we present high-resolution satellite mapping of the ice-surface drainage network (e.g. lakes, channels and moulins) and measurements of seasonal variations in ice flow in south west Greenland. The region is comprised of three distinct subglacial terrains which vary in terms of the amplitude and wavelength and thus the degree to which basal topography is reflected in the ice sheet surface. We find that the distribution of surface hydrological features is related to the transfer of bed topography to the ice sheet surface. For example, in areas of thinner ice and high bed relief, moulins occur more frequently and are more uniformly dispersed, indicating a more distributed influx of surface-derived meltwater to the ice sheet bed. We investigate the implications of such spatial variations in surface hydrology on seasonal ice flow rates.

  4. Observing Radiative Properties of a Thinner, Seasonal Arctic Ice Pack

    NASA Astrophysics Data System (ADS)

    Hudson, S. R.; Nicolaus, M.; Granskog, M.; Gerland, S.; Wang, C.

    2011-12-01

    The Arctic is coming to be dominated by young ice, much of it seasonal. Many of our observations of the radiative properties of sea ice come from drifting stations on thick, multi-year ice. To better understand the Arctic climate system in a warmer world, we need more data about the radiative properties and their seasonal and spatial variability on thinner, younger ice. Since this younger ice is not always thick enough to support lengthy drifting stations, there is a need for new technologies to help us get optical measurements on seasonal ice. One challenge is obtaining seasonal data on ice that is too weak to support even a ship-based camp, and especially to have these observations extend well into the melt season. For these situations, we have developed a spectral radiation monitoring buoy that can be deployed during a one-day ice station, and that can then autonomously observe the spectral albedo and transmittance of the sea ice, transmitting all data in near real time by satellite, until the buoy melts out. Similar installations at manned or regularly visited sites have provided good data, with surprisingly few data-quality problems due to frost, precipitation, or tilting. The buoys consist of 3 spectral radiometers, covering wavelengths 350 to 800 nm, and a datalogger with an Irridium modem. The datalogger and necessary batteries are inside a sealed housing which is frozen into a hole drilled in the ice. Arms extend from both the top and bottom of the housing, holding sensors that measure incident, reflected, and transmitted spectra. The under-ice radiometer is equipped with a bioshutter to avoid algal growth on the sensor. They will be deployed alongside ice mass balance buoys, providing data about the physical development of the ice and snow, as well as position. While the buoys provide an excellent record of diurnal, synoptic, and seasonal variability, they are fixed to one location in the ice, so other methods are still needed for measuring the spatial

  5. Wave climate in the Arctic 1992-2014: seasonality, trends, and wave-ice influence

    NASA Astrophysics Data System (ADS)

    Girard-Ardhuin, Fanny; Stopa, Justin; Ardhuin, Fabrice

    2016-04-01

    The diminishing sea ice has direct implications on the wave field which is mainly dependent on the ice-free area and wind. Over the past decade, the Arctic sea ice has diminished which directly impacts the wave field. This study characterizes the wave climate in the Arctic using detailed sea state information from a wave hindcast and merged altimeter dataset spanning 1992-2014. The waves are driven by winds from the Climate Forecast System Reanalysis. Ice concentrations derived from satellites with a grid spacing of 12.5 km are sufficiently able to resolve important features in the marginal ice zone. Before implementation, suitable wind forcing is identified and the validity and consistency of the wave hindcast is verified with altimeters. The seasonal ice advance and retreat largely dictates the waves and creates distinct features in the wind-waves and swells. The Nordic-Greenland Sea is dominated by swells from the North Atlantic while the coastal regions and semi-enclosed seas of the Kara, Laptev, Chukchi, and Beaufort have a more equal proportion of wind-waves and swells. Trends in the altimeters and model are in agreement and show increasing wave activities in the Baffin Bay, Beaufort, Chukchi, Laptev, and Kara Seas due to the loss of sea ice. In the Nordic-Greenland Sea, there is a decreasing trend related to changes in the wind field by North Atlantic Oscillation. The waves also influence the sea ice. Two distinctly different wave-ice environments are identified and selected events demonstrate the importance of waves in the marginal ice zone. The crux of the research identifies the need for continued study and improvement of wave-ice interaction.

  6. Sea Ice Deformation Rates in the Arctic: from Wind-Driven Synoptic Variability to Seasonal Trends

    NASA Astrophysics Data System (ADS)

    Glowacki, O.; Herman, A.

    2012-12-01

    Deformation mechanisms of the Arctic Ocean ice sheet are characterized by high spatial and temporal variability, in which ice ridges and leads tend to be concentrated in elongated, narrow zones. Present state-of-the-art numerical models, especially those based on various versions of viscous-plastic rheology, are still far from perfection in terms of reproducing localized and intermittent characteristics of sea ice deformation. In this study, the relationship (and its variability) between scaling properties of sea ice deformation and 10-m wind speed is analyzed. We used NCEP-DOE Reanalysis 2 data to determine area-averaged atmospheric drag force. Gridded sea ice total deformation rates from Radarsat Geophysical Processor System (RGPS) data were obtained from the NASA Jet Propulsion Laboratory, with a time resolution of 3 days and a spatial resolution of 12.55 km. Our analysis covers 11 winter seasons from 1996/1997 to 2007/2008. We calculated the moments mq, L of probability distribution functions (pdfs) of total sea ice deformation rates for a range of spatial scales L. The logarithms of the moments are significantly correlated with basin-scale wind forcing, especially for low values of q (with Pearson correlation coefficient reaching 0.7). It can be well-described by simplified momentum equations and a very general rheology model. Furthermore, the strength of this relationship varies seasonally and reaches its minimum in March, due to changeable thickness and consolidation of the Arctic Ocean ice sheet. This effect is clearly seen in comparison with trend lines of time-varying values of moments. Finally, there is a positive trend in seasonally-averaged power of correlation, which is probably associated with decreasing area of the multi-year ice. As a result, the course of sea ice deformation process in the Arctic is a possible indicator of climate change.

  7. Norwegian remote sensing experiment in a marginal ice zone

    USGS Publications Warehouse

    Farrelly, B.; Johannessen, J.A.; Svendsen, E.; Kloster, K.; Horjen, I.; Matzler, C.; Crawford, J.; Harrington, R.; Jones, L.; Swift, C.; Delnore, V.E.; Cavalieri, D.; Gloersen, P.; Hsiao, S.V.; Shemdin, O.H.; Thompson, T.W.; Ramseier, R.O.; Johannessen, O.M.; Campbell, W.J.

    1983-01-01

    The Norwegian Remote Sensing Experiment in the marginal ice zone north of Svalbard took place in fall 1979. Coordinated passive and active microwave measurements were obtained from shipborne, airborne, and satellite instruments together with in situ observations. The obtained spectra of emissivity (frequency range, 5 to 100 gigahertz) should improve identification of ice types and estimates of ice concentration. Mesoscale features along the ice edge were revealed by a 1.215-gigahertz synthetic aperture radar. Ice edge location by the Nimbus 7 scanning multichannel microwave radiometer was shown to be accurate to within 10 kilometers.

  8. Dynamics of the intertropical convergence zone over the western Pacific during the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Yan, Hong; Wei, Wei; Soon, Willie; An, Zhisheng; Zhou, Weijian; Liu, Zhonghui; Wang, Yuhong; Carter, Robert M.

    2015-04-01

    Precipitation in low latitudes is primarily controlled by the position of the intertropical convergence zone, which migrates from south to north seasonally. The Little Ice Age (defined as AD 1400-1850) was associated with low solar irradiance and high atmospheric aerosol concentrations as a result of several large volcanic eruptions. The mean position of the intertropical convergence zone over the western Pacific has been proposed to have shifted southwards during this interval, which would lead to relatively dry Little Ice Age conditions in the northern extent of the intertropical convergence zone and wet conditions around its southern limit. However, here we present a synthesis of palaeo-hydrology records from the Asian-Australian monsoon area that documents a rainfall distribution that distinctly violates the expected pattern. Our synthesis instead documents a synchronous retreat of the East Asian Summer Monsoon and the Australian Summer Monsoon into the tropics during the Little Ice Age, a pattern supported by the results of our climate model simulation of tropical precipitation over the past millennium. We suggest that this pattern over the western Pacific is best explained by a contraction in the latitudinal range over which the intertropical convergence zone seasonally migrates during the Little Ice Age. We therefore propose that rather than a strict north-south migration, the intertropical convergence zone in this region may instead expand and contract over decadal to centennial timescales in response to external forcing.

  9. MIZEX East 83/84: The Summer Marginal Ice Zone Program in the Fram Strait/Greenland Sea

    NASA Astrophysics Data System (ADS)

    MIZEX Group

    A marginal ice zone (MIZ) occurs where polar and temperate climate systems interact and result in an edge of pack ice cover. As a geophysical boundary zone the MIZ is unique in the complexity of the vertical and horizontal air-sea-ice energy interactions that take place there. In response to these, the ice edge moves hundred of kilometers north and south on a seasonal cycle. Successful modeling and prediction of variations in ice edge position and ice concentration would be of great value in furthering man's activities in the region in areas such as offshore Artie oil exploration, seaborne transport of Arctic resorces, further development of the rich fisheries close to the ice margins and for naval operations.

  10. A coupled ice-ocean model of upwelling in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Roed, L. P.; Obrien, J. J.

    1983-01-01

    A dynamical coupled ice-ocean numerical model for the marginal ice zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea ice model has a variable ice concentration and includes internal ice stress. The model is forced by stresses on the air/ocean and air/ice surfaces. The main coupling between the ice and the ocean is in the form of an interfacial stress on the ice/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 ice/ocean is proportional to the concentration of ice. A new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium. The upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across ice 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.

  11. Bimodal albedo distributions in the ablation zone of the southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S. E.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J. R.

    2014-09-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface, and thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. In this study, we analyze albedo and ablation rates using in situ and remotely-sensed data. Observations include: (1) a new high-quality in situ spectral albedo dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified surface ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 and 20-24 July 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  12. Bimodal Albedo Distributions in the Ablation Zone of the Southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J.; Koenig, L.

    2014-12-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface, and thus meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. In this study, we analyze albedo and ablation rates (m d-1) using in situ and remotely-sensed data. Observations include: 1) a new high-quality in situ spectral albedo dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three days in June 2013; 2) broadband albedo at two automatic weather stations; and 3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 July and 20-24 July, 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  13. Arctic sea ice a major determinant in Mandt's black guillemot movement and distribution during non-breeding season.

    PubMed

    Divoky, G J; Douglas, D C; Stenhouse, I J

    2016-09-01

    Mandt's black guillemot (Cepphus grylle mandtii) is one of the few seabirds associated in all seasons with Arctic sea ice, a habitat that is changing rapidly. Recent decreases in summer ice have reduced breeding success and colony size of this species in Arctic Alaska. Little is known about the species' movements and distribution during the nine month non-breeding period (September-May), when changes in sea ice extent and composition are also occurring and predicted to continue. To examine bird movements and the seasonal role of sea ice to non-breeding Mandt's black guillemots, we deployed and recovered (n = 45) geolocators on individuals at a breeding colony in Arctic Alaska during 2011-2015. Black guillemots moved north to the marginal ice zone (MIZ) in the Beaufort and Chukchi seas immediately after breeding, moved south to the Bering Sea during freeze-up in December, and wintered in the Bering Sea January-April. Most birds occupied the MIZ in regions averaging 30-60% sea ice concentration, with little seasonal variation. Birds regularly roosted on ice in all seasons averaging 5 h d(-1), primarily at night. By using the MIZ, with its roosting opportunities and associated prey, black guillemots can remain in the Arctic during winter when littoral waters are completely covered by ice. PMID:27601723

  14. Identification of paleo Arctic winter sea ice limits and the marginal ice zone: Optimised biomarker-based reconstructions of late Quaternary Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Belt, Simon T.; Cabedo-Sanz, Patricia; Smik, Lukas; Navarro-Rodriguez, Alba; Berben, Sarah M. P.; Knies, Jochen; Husum, Katrine

    2015-12-01

    Analysis of >100 surface sediments from across the Barents Sea has shown that the relative abundances of the mono-unsaturated sea ice diatom-derived biomarker IP25 and a tri-unsaturated highly branched isoprenoid (HBI) lipid (HBI III) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal sea ice edge. Thus, while IP25 is generally limited to locations experiencing seasonal sea ice, with higher abundances found for locations with longer periods of ice cover, HBI III is found in sediments from all sampling locations, but is significantly enhanced in sediments within the vicinity of the retreating sea ice edge or marginal ice zone (MIZ). The response of HBI III to this well-defined sea ice scenario also appears to be more selective than that of the more generic phytoplankton biomarker, brassicasterol. The potential for the combined analysis of IP25 and HBI III to provide more detailed assessments of past sea ice conditions than IP25 alone has been investigated by quantifying both biomarkers in three marine downcore records from locations with contrasting modern sea ice settings. For sediment cores from the western Barents Sea (intermittent seasonal sea ice) and the northern Norwegian Sea (ice-free), high IP25 and low HBI III during the Younger Dryas (ca. 12.9-11.9 cal. kyr BP) is consistent with extensive sea cover, with relatively short periods of ice-free conditions resulting from late summer retreat. Towards the end of the YD (ca. 11.9-11.5 cal. kyr BP), a general amelioration of conditions resulted in a near winter maximum ice edge scenario for both locations, although this was somewhat variable, and the eventual transition to predominantly ice-free conditions was later for the western Barents Sea site (ca. 9.9 cal. kyr BP) compared to NW Norway (ca. 11.5 cal. kyr BP). For both locations, coeval elevated HBI III (but absent IP25) potentially provides further evidence for increased Atlantic Water inflow

  15. Deterministic multi-zone ice accretion modeling

    NASA Technical Reports Server (NTRS)

    Yamaguchi, K.; Hansman, R. J., Jr.; Kazmierczak, M.

    1991-01-01

    The study focuses on a deterministic model of the surface roughness transition behavior of glaze ice and analyzes the initial smooth/rough transition location, bead formation, and the propagation of the transition location. Based on a hypothesis that the smooth/rough transition location coincides with the laminar/turbulent boundary-layer transition location, a multizone model is implemented in the LEWICE code. In order to verify the effectiveness of the model, ice accretion predictions for simple cylinders calculated by the multizone LEWICE are compared to experimental ice shapes. The glaze ice shapes are found to be sensitive to the laminar surface roughness and bead thickness parameters controlling the transition location, while the ice shapes are found to be insensitive to the turbulent surface roughness.

  16. Deterministic multi-zone ice accretion modeling

    NASA Technical Reports Server (NTRS)

    Yamaguchi, K.; Hansman, R. John, Jr.; Kazmierczak, Michael

    1991-01-01

    The focus here is on a deterministic model of the surface roughness transition behavior of glaze ice. The initial smooth/rough transition location, bead formation, and the propagation of the transition location are analyzed. Based on the hypothesis that the smooth/rough transition location coincides with the laminar/turbulent boundary layer transition location, a multizone model is implemented in the LEWICE code. In order to verify the effectiveness of the model, ice accretion predictions for simple cylinders calculated by the multizone LEWICE are compared to experimental ice shapes. The glaze ice shapes are found to be sensitive to the laminar surface roughness and bead thickness parameters controlling the transition location, while the ice shapes are found to be insensitive to the turbulent surface roughness.

  17. Understanding the Sea Ice Zone: Scientists and Communities Partnering to Archive, Analyze and Disseminate Local Ice Observations

    NASA Astrophysics Data System (ADS)

    Collins, J. A.; Oldenburg, J.; Liu, M.; Pulsifer, P. L.; Kaufman, M.; Eicken, H.; Parsons, M. A.

    2012-12-01

    Knowledge of sea ice is critical to the hunting, whaling, and cultural activities of many Indigenous communities in Northern and Western Alaska. Experienced hunters have monitored seasonal changes of the sea ice over many years, giving them a unique expertise in assessing the current state of the sea ice as well as any anomalies in seasonal sea ice conditions. The Seasonal Ice Zone Observing Network (SIZONet), in collaboration with the Exchange for Local Observations and Knowledge of the Arctic (ELOKA), has developed an online application for collecting, storing, and analyzing sea ice observations contributed by local experts from coastal Alaskan communities. Here we present the current iteration of the application, outline future plans and discuss how the development process and resulting system have improved our collective understanding of sea ice processes and changes. The SIZONet application design is based on the needs of the research scientists responsible for entering observation data into the database, the needs of local sea ice experts contributing their observations and knowledge, and the information needs of Alaska coastal communities. Entry forms provide a variety of input methods, including menus, check boxes, and free text input. Input options strive to balance flexibility in capturing concepts and details with the need for analytical consistency. Currently, research staff at the University of Alaska Fairbanks use the application to enter observations received via written or electronic communications from local sea ice experts. Observation data include current weather conditions, snow and ice quantity and quality, and wildlife sighted or taken. Future plans call for direct use of the SIZONet interface by local sea ice experts as well as students, both as contributors to the data collection and as users seeking meaning in the data. This functionality is currently available to a limited number of community members as we extend the application to support

  18. Microwave and physical properties of sea ice in the winter marginal ice zone

    NASA Technical Reports Server (NTRS)

    Tucker, W. B., III; Perovich, D. K.; Gow, A. J.; Grenfell, T. C.; Onstott, R. G.

    1991-01-01

    Surface-based active and passive microwave measurements were made in conjunction with ice property measurements for several distinct ice types in the Fram Strait during March and April 1987. Synthesis aperture radar imagery downlinked from an aircraft was used to select study sites. The surface-based radar scattering cross section and emissivity spectra generally support previously inferred qualitative relationships between ice types, exhibiting expected separation between young, first-year and multiyear ice. Gradient ratios, calculated for both active and passive data, appear to allow clear separation of ice types when used jointly. Surface flooding of multiyear floes, resulting from excessive loading and perhaps wave action, causes both active and passive signatures to resemble those of first-year ice. This effect could possibly cause estimates of ice type percentages in the marginal ice zone to be in error when derived from aircraft- or satellite-born sensors.

  19. Passive microwave characteristics of the Bering Sea ice cover during Marginal Ice Zone Experiment (MIZEX) West

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.; Gloersen, P.; Wilheit, T. T.; Calhoon, C.

    1984-01-01

    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 ice zone delineating regions of open water, ice compactness, and ice-edge structure. Analysis of the fixed-beam data shows that spectral differences increase with a decrease in ice thickness. Polarization at 18 and 37 GHz distinguishes among new, young, and first-year sea ice types.

  20. Seismic exploration noise reduction in the Marginal Ice Zone.

    PubMed

    Tollefsen, Dag; Sagen, Hanne

    2014-07-01

    A sonobuoy field was deployed in the Marginal Ice Zone of the Fram Strait in June 2011 to study the spatial variability of ambient noise. High noise levels observed at 10-200 Hz are attributed to distant (1400 km range) seismic exploration. The noise levels decreased with range into the ice cover; the reduction is fitted by a spreading loss model with a frequency-dependent attenuation factor less than for under-ice interior Arctic propagation. Numerical modeling predicts transmission loss of the same order as the observed noise level reduction and indicates a significant loss contribution from under-ice interaction. PMID:24993237

  1. Autonomous Investigations of Marginal Ice Zone Processes- Changing Feedbacks and Observational Challenges

    NASA Astrophysics Data System (ADS)

    Lee, Craig; Doble, Martin; Maslowski, Wieslaw; Stanton, Tim; Timmermans, Mary-Louise; Thomson, Jim; Wilkinson, Jeremy

    2015-04-01

    The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice 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 (PSW) and Atlantic (AW) waters) and elevated surface wave energy that acts to deform and fracture sea ice, all of which grow in importance with increasing open water extent. Investigations of MIZ dynamics must resolve the short spatial and temporal scales associated with the processes that govern the exchange of momentum, heat and freshwater near the atmosphere-ice-ocean interface while also achieving the spatial scope and temporal persistence required to characterize how the balance of processes shifts as a function of evolving open water fraction and open water fetch to the south. The recent Office of Naval Research (ONR) Marginal Ice Zone program employed an integrated system of autonomous platforms to provide high-resolution measurements that extend from open water, through the MIZ and deep into ice-covered regions while providing persistence to quantify evolution over an entire summertime melt season. This presentation will provide an overview of the strategy developed by the ONR MIZ team and present early results from the 2014 field program.

  2. Autonomous Investigations of Marginal Ice Zone Processes- Changing Feedbacks and Observational Challenges

    NASA Astrophysics Data System (ADS)

    Lee, C.

    2014-12-01

    The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) has profound impacts on the balance of processes controlling sea ice 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 (PSW) and Atlantic (AW) waters) and elevated surface wave energy that acts to deform and fracture sea ice, all of which grow in importance with increasing open water extent. Investigations of MIZ dynamics must resolve the short spatial and temporal scales associated with the processes that govern the exchange of momentum, heat and freshwater near the atmosphere-ice-ocean interface while also achieving the spatial scope and temporal persistence required to characterize how the balance of processes shifts as a function of evolving open water fraction and open water fetch to the south. The recent Office of Naval Research (ONR) Marginal Ice Zone program provides an example of how autonomous platforms can be applied to provide high-resolution measurements that extend from open water, through the MIZ and deep into ice-covered regions while providing persistence to quantify evolution over an entire summertime melt season. This talk will provide an overview of the strategy developed by the ONR MIZ team and highlight early results from the 2014 field program.

  3. Sea ice melting in the marginal ice zone.

    USGS Publications Warehouse

    Josberger, E.G.

    1983-01-01

    The heat and salt flux boundary conditions together with the freezing curve relationship are a necessary component of any ice- sea water thermodynamic model. A neutral two-layer oceanic planetary boundary layer model that incorporates these boundary conditions is used. The results are discussed. -from Author

  4. Evolution of microwave sea ice signatures during early summer and midsummer in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Onstott, R. G.; Grenfell, T. C.; Matzler, C.; Luther, C. A.; Svendsen, E. A.

    1987-01-01

    Emissivities at frequencies from 5 to 94 GHz and backscatter at frequencies from 1 to 17 GHz were measured from sea ice in Fram Strait during the marginal Ice Zone Experiment in June and July of 1983 and 1984. The ice observed was primarily multiyear; the remainder, first-year ice, was often deformed. Results from this active and passive microwave study include the description of the evolution of the sea ice during early summer and midsummer; the absorption properties of summer snow; the interrelationship between ice thickness and the state and thickness of snow; and the modulation of the microwave signature, especially at the highest frequencies, by the freezing of the upper few centimeters of the ice.

  5. Arctic sea ice trends, variability and implications for seasonal ice forecasting.

    PubMed

    Serreze, Mark C; Stroeve, Julienne

    2015-07-13

    September Arctic sea ice extent over the period of satellite observations has a strong downward trend, accompanied by pronounced interannual variability with a detrended 1 year lag autocorrelation of essentially zero. We argue that through a combination of thinning and associated processes related to a warming climate (a stronger albedo feedback, a longer melt season, the lack of especially cold winters) the downward trend itself is steepening. The lack of autocorrelation manifests both the inherent large variability in summer atmospheric circulation patterns and that oceanic heat loss in winter acts as a negative (stabilizing) feedback, albeit insufficient to counter the steepening trend. These findings have implications for seasonal ice forecasting. In particular, while advances in observing sea ice thickness and assimilating thickness into coupled forecast systems have improved forecast skill, there remains an inherent limit to predictability owing to the largely chaotic nature of atmospheric variability. PMID:26032315

  6. Arctic sea ice trends, variability and implications for seasonal ice forecasting

    PubMed Central

    Serreze, Mark C.; Stroeve, Julienne

    2015-01-01

    September Arctic sea ice extent over the period of satellite observations has a strong downward trend, accompanied by pronounced interannual variability with a detrended 1 year lag autocorrelation of essentially zero. We argue that through a combination of thinning and associated processes related to a warming climate (a stronger albedo feedback, a longer melt season, the lack of especially cold winters) the downward trend itself is steepening. The lack of autocorrelation manifests both the inherent large variability in summer atmospheric circulation patterns and that oceanic heat loss in winter acts as a negative (stabilizing) feedback, albeit insufficient to counter the steepening trend. These findings have implications for seasonal ice forecasting. In particular, while advances in observing sea ice thickness and assimilating thickness into coupled forecast systems have improved forecast skill, there remains an inherent limit to predictability owing to the largely chaotic nature of atmospheric variability. PMID:26032315

  7. Marginal Ice Zone Processes Observed from Unmanned Aerial Systems

    NASA Astrophysics Data System (ADS)

    Zappa, C. J.

    2015-12-01

    Recent years have seen extreme changes in the Arctic. Marginal ice zones (MIZ), or areas where the "ice-albedo feedback" driven by solar warming is highest and ice melt is extensive, may provide insights into the extent of these changes. Furthermore, MIZ play a central role in setting the air-sea CO2 balance making them a critical component of the global carbon cycle. Incomplete understanding of how the sea-ice modulates gas fluxes renders it difficult to estimate the carbon budget in MIZ. Here, we investigate the turbulent mechanisms driving mixing and gas exchange in leads, polynyas and in the presence of ice floes using both field and laboratory measurements. Measurements from unmanned aerial systems (UAS) in the marginal ice zone were made during 2 experiments: 1) North of Oliktok Point AK in the Beaufort Sea were made during the Marginal Ice Zone Ocean and Ice Observations and Processes EXperiment (MIZOPEX) in July-August 2013 and 2) Fram Strait and Greenland Sea northwest of Ny-Ålesund, Svalbard, Norway during the Air-Sea-Ice Physics and Biogeochemistry Experiment (ASIPBEX) April - May 2015. We developed a number of new payloads that include: i) hyperspectral imaging spectrometers to measure VNIR (400-1000 nm) and NIR (900-1700 nm) spectral radiance; ii) net longwave and net shortwave radiation for ice-ocean albedo studies; iii) air-sea-ice turbulent fluxes as well as wave height, ice freeboard, and surface roughness with a LIDAR; and iv) drone-deployed micro-drifters (DDµD) deployed from the UAS that telemeter temperature, pressure, and RH as it descends through the atmosphere and temperature and salinity of the upper meter of the ocean once it lands on the ocean's surface. Visible and IR imagery of melting ice floes clearly defines the scale of the ice floes. The IR imagery show distinct cooling of the skin sea surface temperature (SST) as well as an intricate circulation and mixing pattern that depends on the surface current, wind speed, and near

  8. A meteorological experiment in the melting zone of the Greenland ice sheet

    SciTech Connect

    Oerlemans, J. ); Vugts, H.F. )

    1993-03-01

    Preliminary results are described from a glaciometeorological experiment carried out in the margin (melting zone) of the Greenland ice sheet in the summers of 1990 and 1991. This work was initiated within the framework of a Dutch research program on land ice and sea level change. Seven meteostations were operated along a transect running from the tundra well onto the ice sheet. At the ice edge, humidity, temperature, and wind profiles were obtained with a tethered balloon. On the ice sheet, 90 km from the edge, a boundary-layer research unit, including a sound detecting and ranging system (SODAR) and a radio acoustic sounding system (RASS), was established. Although focusing on the relation between surface energy balance, glacier mass balance, and ice flow, the experiment has also delivered a unique dataset on the dynamics of the atmospheric boundary layer around the warm tundra-cold ice sheet transition. Unexpected behavior was found for the surface albedo during the melt season. Lowest values are not found close to the ice edge, which is usual for glaciers, but higher on the ice sheet. Meltwater accumulation due to inefficient surface drainage was found to be the cause for this. The wind regime is dominated by katabatic flow from the ice sheet. The katabatic layer is typically 100-200 m thick. Close to the ice edge, the flow exhibits a very regular daily rhythm, with maximum wind speed in the afternoon. Farther on the ice sheet, the regime changes, and wind speed reaches maximum values in late night/early morning.

  9. Trends in the Length of the Southern Ocean Sea Ice Season: 1979-1999

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    Satellite data can be used to observe the sea ice distribution around the continent of Antarctica on a daily basis and hence to determine how many days a year have sea ice 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 ice season around Antarctica. Most of the Ross Sea ice cover has undergone a lengthening of the sea ice season, whereas most of the Amundsen Sea ice cover and almost the entire Bellingshausen Sea ice cover have undergone a shortening of the sea ice 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 ice season than a shortening. For instance, the area experiencing a lengthening of the sea ice 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 ice 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 ice cover, including shortened sea ice seasons and decreased ice extents.

  10. Seasonal variations in sea ice motion and effects on sea ice concentration in the Canada Basin

    NASA Astrophysics Data System (ADS)

    Serreze, Mark C.; Barry, Roger G.; McLaren, Alfred S.

    1989-08-01

    Drifting buoy data, surface pressure, and geostrophic wind analyses from the Arctic Ocean Buoy Program are used to examine seasonal features of the sea ice motion in the Canada Basin for 1979-1985. Although the 7-year annual mean motion in this region is clockwise, the month-to-month motion is highly variable. In late summer to early autumn, the circulation can become net anticlockwise for periods lasting at least 30 days. Results from a linear model demonstrate that these "reversals" of ice motion in the Beaufort Gyre are a wind-driven response to persistent cyclonic activity that contrasts sharply with the predominantly anticyclonic regimes of spring, late autumn, and winter. Model-predicted ice divergences of 0.5% or more per day which can occur during periods of anticlockwise ice motion are in good agreement with values calculated from optimally interpolated velocity gradient fields. Visible band imagery and passive microwave data confirm associated large areal reductions in ice concentration of approximately 20%. Data from under-ice submarine sonar transects and surface pressure records prior to the study period point to frequent recurrences of these late summer to early autumn ice conditions.

  11. Anomalous snow accumulation over the southeast region of the Greenland ice sheet during 2002-2003 snow season

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Steffen, K.; Huff, R.; Neumann, G.

    2005-01-01

    Our objective is to determine seasonal snow accumulation in the percolation zone of the Greenland ice sheet on the daily-weekly basis over the large scale. Our approach utilizes data from the Greenland Climate Network (GC-Net) and from the SeaWinds Scatterometer on the QuikSCAT satellite (QSCAT) to measure snow accumulation (SA) in the percolation zone of the Greenland ice sheet. GC-Net measurements provide crucial in-situ data to facilitate the interpretation of QSCAT backscatter signature for the development of an algorithm to map SA.

  12. Coupled ice-ocean dynamics in the marginal ice zones Upwelling/downwelling and eddy generation

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.

    1986-01-01

    This study is aimed at modeling mesoscale processes such as upwelling/downwelling and ice edge eddies in the marginal ice zones. A two-dimensional coupled ice-ocean model is used for the study. The ice 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 ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux; thus the Ekman transport is greater than the ice 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 ice cover 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 ice edge, so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice.

  13. Melt ponds and marginal ice zone from new algorithm of sea ice concentration retrieval

    NASA Astrophysics Data System (ADS)

    Repina, Irina; Tikhonov, Vasiliy; Komarova, Nataliia; Raev, Mikhail; Sharkov, Evgeniy

    2016-04-01

    Studies of spatial and temporal properties of sea ice distribution in polar regions help to monitor global environmental changes and reveal their natural and anthropogenic factors, as well as make forecasts of weather, marine transportation and fishing conditions, assess perspectives of mineral mining on the continental shelf, etc. Contact methods of observation are often insufficient to meet the goals, very complicated technically and organizationally and not always safe for people involved. Remote sensing techniques are believed to be the best alternative. Its include monitoring of polar regions by means of passive microwave sensing with the aim to determine spatial distribution, types, thickness and snow cover of ice. However, the algorithms employed today to retrieve sea ice characteristics from passive microwave sensing data for different reasons give significant errors, especially in summer period and also near ice edges and in cases of open ice. A new algorithm of sea ice concentration retrieval in polar regions from satellite microwave radiometry data is discussed. Beside estimating sea ice concentration, the algorithm makes it possible to indicate ice areas with melting snow and melt ponds. Melt ponds are an important element of the Arctic climate system. Covering up to 50% of the surface of drifting ice in summer, they are characterized by low albedo values and absorb several times more incident shortwave radiation than the rest of the snow and ice cover. The change of melt ponds area in summer period 1987-2015 is investigated. The marginal ice zone (MIZ) is defined as the area where open ocean processes, including specifically ocean waves, alter significantly the dynamical properties of the sea ice cover. Ocean wave fields comprise short waves generated locally and swell propagating from the large ocean basins. Depending on factors like wind direction and ocean currents, it may consist of anything from isolated, small and large ice floes drifting over a

  14. Formation processes of floe size distribution in the marginal ice zone (Invited)

    NASA Astrophysics Data System (ADS)

    Toyota, T.; Kohout, A.; Fraser, A.

    2013-12-01

    Since the marginal ice zone (MIZ) is the outer sea ice zone, its behavior is key to the understanding of the variability of sea ice extent associated with climate change. Especially for the melting processes in MIZ, where relatively small ice floes are dominant, floe size distribution (FSD) is an important parameter because smaller ice floes are subject to stronger lateral melting due to their larger cumulative perimeters. As the MIZ is characterized by vigorous interaction between sea ice and waves, breakup of sea ice due to flexural forcing and collisions is considered to play an essential role in the determination of FSD there. However, the available data have been very limited so far. Analysis of the observations of ice floes with a heli-borne video camera, focusing on the floe size ranging from 2 m to 100 m, in the Sea of Okhotsk, the Weddell Sea and off East Antarctica, revealed that while FSD is basically scale-invariant, a regime shift occurs at a size of about a few tens of meters, irrespective of the study region. It was also shown 1) that the floe size at which regime shift occurs slightly increases from 20 to 40 m with ice thickness, consistent with the theory of the flexural failure of sea ice; and 2) that to explain the scale invariance in FSD for smaller floes, a fragility of sea ice which is relevant to the strength of sea ice relative to waves can be a useful physical parameter to be correlated with the fractal dimension. Thus these results confirm the importance of wave-ice interaction to the formation of FSD. Based on this, a possible mechanism of the melting process was hypothesized that in the melting season sea ice extent retreats keeping the FSD relative to the ice edge nearly constant. As a next step and to confirm and further investigate this result, we planned to conduct the concurrent measurements of FSD, wave activities, and ice thickness off East Antarctica during the Sea Ice Physics and Ecosystem Experiment 2 (SIPEX2) in September to

  15. The 2012 Arctic Field Season of the NRL Sea-Ice Measurement Program

    NASA Astrophysics Data System (ADS)

    Gardner, J. M.; Brozena, J. M.; Hagen, R. A.; Liang, R.; Ball, D.

    2012-12-01

    The U.S. Naval Research Laboratory (NRL) is beginning a five year study of the changing Arctic with a particular focus on ice thickness and distribution variability with the intent of optimizing state-of-the-art computer models which are currently used to predict sea ice changes. An important part of our study is to calibrate/validate CryoSat2 ice thickness data prior to its incorporation into new ice forecast models. NRL Code 7420 collected coincident data with the CryoSat2 satellite in both 2011 and 2012 using a LiDAR (Riegl Q560) to measure combined snow and ice thickness and a 10 GHz pulse-limited precision radar altimeter to measure sea-ice freeboard. These measurements were coordinated with the Seasonal Ice Zone Observing Network (SIZONet) group who conducted surface based ice thickness surveys using a Geonics EM-31 along hunter trails on the landfast ice near Barrow as well as on drifting ice offshore during helicopter landings. On two sorties, a twin otter carrying the NRL LiDAR and radar altimeter flew in tandem with the helicopter carrying the EM-31 to achieve synchronous data acquisition. Data from these flights are shown here along with a digital elevation map. The LiDAR and radar altimeter were also flown on grid patterns over the ice that were synchronous with 5 Cryosat2 satellite passes. These grids were intended to cover roughly 10 km long segments of Cryosat2 tracks with widths similar to the footprint of the satellite (~2 km). Reduction of these grids is challenging because of ice drift which can be many hundreds of meters over the 1-2 hours collection period of each grid. Relocation of the individual scanning LiDAR tracks is done by means of tie-points observed in the overlapping swaths. Data from these grids are shown here and will be used to examine the relationship of the tracked satellite waveform data to the actual surface across the footprint.

  16. Formation of the Carbon Dioxide Ice Seasonal Polar Caps

    NASA Astrophysics Data System (ADS)

    Forget, F.

    1998-01-01

    One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO2 ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties Of CO2 ice condensing in a CO2 atmosphere. For instance, the Infrared Thermal Mapper (IRTM). One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO2 ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties Of CO2 ice condensing in a CO2 atmosphere. For instance, the IRTM instrument observed variable structures exhibiting brightness temperatures far below the physical temperature appropriate for condensed CO, in vapor pressure equilibrium at the expected atmospheric pressure. A detailed analysis of the data suggests that these low brightness temperatures result from the radiative properties of the SMO CO2 ice particles that condense in the atmosphere rather than directly on the surface New observations are being transmitted by Mars Global Surveyor. TES and MOLA data should greatly improve our understand- ing of what is really going on during the cap formation. instrument observed variable structures exhibiting brightness temperatures

  17. Thermal insulation of the intertidal zone by the ice foot

    NASA Astrophysics Data System (ADS)

    Scrosati, Ricardo; Eckersley, Lindsay K.

    2007-11-01

    Few studies have looked at the ecological significance of the ice foot in intertidal habitats. During the 2007 winter, we quantified the hourly variation of temperature at the intertidal zone and at the upper, dry coast on the southern Gulf of St. Lawrence (Nova Scotia, Canada) using submersible data loggers. While air temperature dropped to - 20 °C at the peak of the winter, intertidal temperature was never below - 7 °C during the winter. In fact, for almost two months when the ice foot was stable, temperature ranged only between - 2.4 °C and - 1.1 °C at the intertidal zone. The intertidal values are higher than published values of lethal temperature for cold-water intertidal invertebrates and seaweeds. Thus, the ice foot may prevent these organisms from experiencing lethal levels of thermal stress, contributing to their long-term persistence in these environmentally stressful habitats.

  18. 36 CFR 13.1304 - Ice fall hazard zones.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Ice fall hazard zones. 13.1304 Section 13.1304 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Kenai Fjords National Park...

  19. 36 CFR 13.1304 - Ice fall hazard zones.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Ice fall hazard zones. 13.1304 Section 13.1304 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Kenai Fjords National Park...

  20. 36 CFR 13.1304 - Ice fall hazard zones.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Ice fall hazard zones. 13.1304 Section 13.1304 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Kenai Fjords National Park...

  1. 36 CFR 13.1304 - Ice fall hazard zones.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Ice fall hazard zones. 13.1304 Section 13.1304 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Kenai Fjords National Park...

  2. 36 CFR 13.1304 - Ice fall hazard zones.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Ice fall hazard zones. 13.1304 Section 13.1304 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Kenai Fjords National Park...

  3. Multisensor comparison of ice concentration estimates in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Burns, B. A.; Cavalieri, D. J.; Gloersen, P.; Keller, M. R.; Campbell, W. J.

    1987-01-01

    Aircraft remote sensing data collected during the 1984 summer Marginal Ice Zone Experiment in the Fram Strait are used to compare ice concentration estimates derived from synthetic aperture radar (SAR) imagery, passive microwave imagery at several frequencies, aerial photography, and spectral photometer data. The comparison is carried out not only to evaluate SAR performance against more established techniques but also to investigate how ice surface conditions, imaging geometry, and choice of algorithm parameters affect estimates made by each sensor.Active and passive microwave sensor estimates of ice concentration derived using similar algorithms show an rms difference of 13 percent. Agreement between each microwave sensor and near-simultaneous aerial photography is approximately the same (14 percent). The availability of high-resolution microwave imagery makes it possible to ascribe the discrepancies in the concentration estimates to variations in ice surface signatures in the scene.

  4. Active/passive microwave sensor comparison of MIZ-ice concentration estimates. [Marginal Ice Zone (MIZ)

    NASA Technical Reports Server (NTRS)

    Burns, B. A.; Cavalieri, D. J.; Keller, M. R.

    1986-01-01

    Active and passive microwave data collected during the 1984 summer Marginal Ice Zone Experiment in the Fram Strait (MIZEX 84) are used to compare ice concentration estimates derived from synthetic aperture radar (SAR) data to those obtained from passive microwave imagery at several frequencies. The comparison is carried out to evaluate SAR performance against the more established passive microwave technique, and to investigate discrepancies in terms of how ice surface conditions, imaging geometry, and choice of algorithm parameters affect each sensor. Active and passive estimates of ice concentration agree on average to within 12%. Estimates from the multichannel passive microwave data show best agreement with the SAR estimates because the multichannel algorithm effectively accounts for the range in ice floe brightness temperatures observed in the MIZ.

  5. Seasonal circulation under the eastern Ross Ice Shelf, Antarctia

    SciTech Connect

    Hellmer, H.H.; Jacobs, S.S.

    1995-06-15

    An annual cycle of shelf water temperatures and salinities measured at depth near the eastern Ross Ice Shelf front is used to force a two-dimensional thermohaline circulation model adapted to different subice paths in the vicinity of Roosevelt Island. These paths were assumed to have constant water column thicknesses of 160, 200, and 240 m and lengths of 460-800 km. Additional simulations with the longer cavity included a 80-m thick interior water column in order to approximate conditions closer to the grounding line. Model results were compared with other long-term measurements that showed outflow from beneath the ice shelf. Shelf water flowing into the cavity west of Roosevelt Island appears to follow a cyclonic route around the island. The ice shelf base loses mass at a rate of 18-27 cm yr{sup {minus}1}, with seasonal forcing increasing the spatial and temporal variability of circulation and property distributions in the larger cavities. Shallow cavities reduce the influence of shelf water variability with increasing length. Introducing a transient shelf water temperature rise of 0.01{degrees}C yr {sup {minus}1} for 100 years increases the melt rate by 4-5 times. However, this increase is smaller if salinity also decreases over the same period of time, as might be expected from the added meltwater component. 42 refs., 9 figs.

  6. Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle

    NASA Astrophysics Data System (ADS)

    Li, Linghan; McClean, Julie L.; Miller, Arthur J.; Eisenman, Ian; Hendershott, Myrl C.; Papadopoulos, Caroline A.

    2014-12-01

    The seasonal cycle of sea ice 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-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice 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 ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice 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 ice edge. In spring and fall, similar thermodynamic and dynamic

  7. Distinct Seasonal Velocity Patterns Based on Ice-Sheet-Wide Analysis of Greenland Outlet Glaciers

    NASA Astrophysics Data System (ADS)

    Moon, T. A.; Joughin, I. R.; Smith, B. E.; van den Broeke, M. R.; Usher, M.

    2014-12-01

    Mass loss from the Greenland Ice Sheet increased significantly over the last several decades and current mass losses of 260-380 Gt ice/yr contribute 0.7-1.1 mm/yr to global sea-level rise. Greenland mass loss includes ice discharge via marine-terminating outlet glaciers and surface meltwater runoff, the former now making up a third to a half of total ice loss. The magnitude of ice discharge depends in part on ice-flow speed, which has broadly increased since 2000 but varies locally, regionally, and from year to year. Research on a limited set of Greenland glaciers also shows that speeds vary seasonally. However, for much of the west, northwest, and southeast coasts where ice loss is increasing most rapidly, there are few or no records of seasonal velocity variation. Ice velocity is influenced by several key components of the ice-sheet-ocean-climate system: subglacial environment, surface melt and runoff, and ice-ocean interaction at the ice-front (terminus). Thus, knowledge of seasonal velocity patterns is important for predicting annual ice discharge, understanding the effects of increased surface melt on total mass loss, and establishing how ice-flow responds to other climatic changes. We developed 5-year records of seasonal velocity measurements for 55 glaciers around the ice-sheet margin. Among glaciers with significant speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position, with seasonal summer speedup sustained through fall. The other two patterns appear to be meltwater controlled and indicate regional differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. These differences in dominant velocity control mechanisms reveal likely spatiotemporal variations in the dynamic response of the ice sheet to climate change.

  8. Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification ?

    NASA Astrophysics Data System (ADS)

    Inoue, J.; Hori, M. E.

    2011-12-01

    Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent ramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase.

  9. Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification?

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Hori, Masatake E.

    2011-06-01

    Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent dramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase.

  10. Ocean-ice interaction in the marginal ice zone using synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chich Y.; Weingartner, Thomas J.

    1994-01-01

    Ocean-ice interaction processes in the marginal ice zone (MIZ) by wind, waves, and mesoscale features, such as up/downwelling and eddies are studied using Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) images and an ocean-ice interaction model. A sequence of seven SAR images of the MIZ in the Chukchi Sea with 3 or 6 days interval are investigated for ice edge advance/retreat. Simultaneous current measurements from the northeast Chukchi Sea, as well as the Barrow wind record, are used to interpret the MIZ dynamics. SAR spectra of waves in ice and ocean waves in the Bering and Chukchi Sea are compared for the study of wave propagation and dominant SAR imaging mechanism. By using the SAR-observed ice edge configuration and wind and wave field in the Chukchi Sea as inputs, a numerical simulation has been performed with the ocean-ice interaction model. After 3 days of wind and wave forcing the resulting ice edge configuration, eddy formation, and flow velocity field are shown to be consistent with SAR observations.

  11. Radar measurements of melt zones on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.; Gogineni, Prasad; Shanableh, M.

    1994-01-01

    Surface-based microwave radar measurements were performed at a location on the western flank of the Greenland Ice Sheet. Here, firn metamorphasis is dominated by seasonal melt, which leads to marked contrasts in the vertical structure of winter and summer firn. This snow regime is also one of the brightest radar targets on Earth with an average backscatter coefficient of 0 dB at 5.3 GHz and an incidence angle of 25 deg. By combining detailed observations of firn physical properties with ranging radar measurements we find that the glaciological mechanism associated with this strong electromagnetic response is summer ice lens formation within the previous winter's snow pack. This observation has important implications for monitoring and understanding changes in ice sheet volume using spaceborne microwave sensors.

  12. Composition, Diversity, and Stability of Microbial Assemblages in Seasonal Lake Ice, Miquelon Lake, Central Alberta

    PubMed Central

    Bramucci, Anna; Han, Sukkyun; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2013-01-01

    The most familiar icy environments, seasonal lake and stream ice, have received little microbiological study. Bacteria and Eukarya dominated the microbial assemblage within the seasonal ice of Miquelon Lake, a shallow saline lake in Alberta, Canada. The bacterial assemblages were moderately diverse and did not vary with either ice depth or time. The closest relatives of the bacterial sequences from the ice included Actinobacteria, Bacteroidetes, Proteobacteria, Verrucomicrobia, and Cyanobacteria. The eukaryotic assemblages were less conserved and had very low diversity. Green algae relatives dominated the eukaryotic gene sequences; however, a copepod and cercozoan were also identified, possibly indicating the presence of complete microbial loop. The persistence of a chlorophyll a peak at 25–30 cm below the ice surface, despite ice migration and brine flushing, indicated possible biological activity within the ice. This is the first study of the composition, diversity, and stability of seasonal lake ice. PMID:24832796

  13. Comparison of icing cloud instruments for 1982-1983 icing season flight program

    NASA Technical Reports Server (NTRS)

    Ide, R. F.; Richter, G. P.

    1984-01-01

    A number of modern and old style liquid water content (LWC) and droplet sizing instruments were mounted on a DeHavilland DHC-6 Twin Otter and operated in natural icing clouds in order to determine their comparative operating characteristics and their limitations over a broad range of conditions. The evaluation period occurred during the 1982-1983 icing season from January to March 1983. Time histories of all instrument outputs were plotted and analyzed to assess instrument repeatability and reliability. Scatter plots were also generated for comparison of instruments. The measured LWC from four instruments differed by as much as 20 percent. The measured droplet size from two instruments differed by an average of three microns. The overall effort demonstrated the need for additional data, and for some means of calibrating these instruments to known standards.

  14. Recent Trends in the Arctic Navigable Ice Season and Links to Atmospheric Circulation

    NASA Astrophysics Data System (ADS)

    Maslanik, J.; Drobot, S.

    2002-12-01

    One of the potential effects of Arctic climate warming is an increase in the navigable ice season, perhaps resulting in development of the Arctic as a major shipping route. The distance from western North American ports to Europe through the Northwest Passage (NWP) or the Northern Sea Route (NSR) is typically 20 to 60 percent shorter than travel through the Panama Canal, while travel between Europe and the Far East may be reduced by as much as three weeks compared to transport through the Suez Canal. An increase in the navigable ice season would also improve commercial opportunities within the Arctic region, such as mineral and oil exploration and tourism, which could potentially expand the economic base of Arctic residents and companies, but which would also have negative environmental impacts. Utilizing daily passive-microwave derived sea ice concentrations, trends and variability in the Arctic navigable ice season are examined from 1979 through 2001. Trend analyses suggest large increases in the length of the navigable ice season in the Kara and Barents seas, the Sea of Okhotsk, and the Beaufort Sea, with decreases in the length of the navigable ice season in the Bering Sea. Interannual variations in the navigable ice season largely are governed by fluctuations in low-frequency atmospheric circulation, although the specific annular modes affecting the length of the navigable ice season vary by region. In the Beaufort and East Siberian seas, variations in the North Atlantic Oscillation/Arctic Oscillation control the navigable ice season, while variations in the East Pacific anomaly play an important role in controlling the navigable ice season in the Kara and Barents seas. In Hudson Bay, the Canadian Arctic Archipelago, and Baffin Bay, interannual variations in the navigable ice season are strongly related to the Pacific Decadal Oscillation.

  15. Seasonal Changes in Mars' North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    1997-01-01

    These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This first mosaic is a view which could not actually be seen in nature because at this season a portion of the pole would have actually been in shadow; the last view, taken near the summer solstice, would correspond to the Midnight Sun on Earth with the pole fully illuminated all day. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap.

    October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. (The notches are areas where Hubble data were not available). A thin, comma-shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the geographic pole at this season; the bluish 'knobs' where the cap seems to extend further are actually clouds that occurred near the edges of the three separate sets of images used to make the mosaic.

    January 1997 (mid-spring): Increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes (see March '97 map); these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season

  16. Prospects for better seasonal Arctic sea ice predictions from multivariate initialization

    NASA Astrophysics Data System (ADS)

    Massonnet, Francois; Fichefet, Thierry; Goosse, Hugues; Zunz, Violette

    2014-05-01

    Predicting the summer Arctic sea ice conditions a few months in advance has become a challenging priority. A good knowledge of the initial sea ice state is necessary to hopefully produce skillful seasonal forecasts. However, most of the intrinsic memory of sea ice lies in its thickness distribution, and homogeneous observational networks of sea ice thickness are limited in space and time. To overcome this problem, we constrain the ocean-sea ice model NEMO-LIM3 with real observations of sea ice concentration using the ensemble Kalman filter. Because of the multivariate nature of this filter, sea ice thickness is globally updated in a consistent way whenever observations of concentration are available. We report the skill of 27 retrospective seasonal Arctic sea ice forecasts (1983-2009) with and without sea ice initialization, using a prescribed atmosphere. The results clearly exhibit the added value of sea initialization for seasonal prediction of the September ice concentration, in particular during the last decade. This suggests that current seasonal sea ice forecast systems could gain predictive skill from a realistic sea ice initialization.

  17. Modeling the seasonal variability of a coupled Arctic ice-ocean system

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Mellor, George L.

    1992-01-01

    The seasonal variability of the ice-ocean system in the Arctic Basin and the Norwegian, Greenland, and Barents Seas was modeled using a three-dimensional coupled ice-ocean model developed at Princeton University. The snow-ice model uses a three-level thermodynamic scheme similar to Semtner's (1976), but is extended to include the effect of leads. It is shown that simulations using the climatological monthly forcing fields produce a realistic seasonal variability of the ice cover. The ice thickness had a considerable sensitivity to the choice of the long-wave back radiation scheme, but these effects can be reduced through dynamical factors.

  18. Ice surface temperatures: seasonal cycle and daily variability from in-situ and satellite observations

    NASA Astrophysics Data System (ADS)

    Madsen, Kristine S.; Dybkjær, Gorm; Høyer, Jacob L.; Nielsen-Englyst, Pia; Rasmussen, Till A. S.; Tonboe, Rasmus T.

    2016-04-01

    Surface temperature is an important parameter for understanding the climate system, including the Polar Regions. Yet, in-situ temperature measurements over ice- and snow covered regions are sparse and unevenly distributed, and atmospheric circulation models estimating surface temperature may have large biases. To change this picture, we will analyse the seasonal cycle and daily variability of in-situ and satellite observations, and give an example of how to utilize the data in a sea ice model. We have compiled a data set of in-situ surface and 2 m air temperature observations over land ice, snow, sea ice, and from the marginal ice zone. 2523 time series of varying length from 14 data providers, with a total of more than 13 million observations, have been quality controlled and gathered in a uniform format. An overview of this data set will be presented. In addition, IST satellite observations have been processed from the Metop/AVHRR sensor and a merged analysis product has been constructed based upon the Metop/AVHRR, IASI and Modis IST observations. The satellite and in-situ observations of IST are analysed in parallel, to characterize the IST variability on diurnal and seasonal scales and its spatial patterns. The in-situ data are used to estimate sampling effects within the satellite observations and the good coverage of the satellite observations are used to complete the geographical variability. As an example of the application of satellite IST data, results will be shown from a coupled HYCOM-CICE ocean and sea ice model run, where the IST products have been ingested. The impact of using IST in models will be assessed. This work is a part of the EUSTACE project under Horizon 2020, where the ice surface temperatures form an important piece of the puzzle of creating an observationally based record of surface temperatures for all corners of the Earth, and of the ESA GlobTemperature project which aims at applying surface temperatures in models in order to

  19. Formation of the Carbon Dioxide Ice Seasonal Polar Caps

    NASA Astrophysics Data System (ADS)

    Foster, J.; Chang, A.; Hall, D.; Tait, A.; Klein, A.

    1998-01-01

    One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO, ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties of CO2 ice condensing in a CO2 atmosphere. For instance, the Infrared Thermal Mapper (IRTM) instrument observed variable structures exhibiting brightness temperatures far below the physical temperature appropriate for condensed CO2 in vapor pressure equilibrium at the expected atmospheric pressure. A detailed analysis of the data suggests that these low brightness temperatures result from the radiative properties of the small CO2 ice particles that condense in the atmosphere rather than directly on the surface. Indeed, simulations performed with General Circulation Models have shown that a fraction of the total CO2 condensation can take place in the atmosphere. Atmospheric condensation can result from radiative cooling on the one hand (especially when the atmosphere is dust laden) and from adiabatic cooling in upward motions on the other . The resulting CO2 snowfalls could create the observed features, because the CO2 ice particles that condense in the atmosphere can be efficient scatterers at infrared wavelengths (whether they are airborne or have just fallen to the ground) carbon dioxide ice deposits composed of nonporous solid ice, however, having directly condensed on the ground or having undergone frost metamorphism should behave almost like blackbody emitters, or, more likely, be transparent in the infrared so that the ground beneath can radiate through. In fact, by simply parametrizing

  20. 46 CFR 42.30-5 - Northern Winter Seasonal Zones and area.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-5 Northern Winter Seasonal Zones and.... Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by...

  1. 46 CFR 42.30-5 - Northern Winter Seasonal Zones and area.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-5 Northern Winter Seasonal Zones and.... Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by...

  2. 46 CFR 42.30-5 - Northern Winter Seasonal Zones and area.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-5 Northern Winter Seasonal Zones and.... Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by...

  3. 46 CFR 42.30-5 - Northern Winter Seasonal Zones and area.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-5 Northern Winter Seasonal Zones and.... Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by...

  4. 46 CFR 42.30-5 - Northern Winter Seasonal Zones and area.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-5 Northern Winter Seasonal Zones and.... Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by...

  5. Insights into the Thwaites Glacier grounding zone from Operation IceBridge aerogravity

    NASA Astrophysics Data System (ADS)

    Tinto, K. J.; Bell, R. E.; Cochran, J. R.; Elieff, S.; Frearson, N.

    2010-12-01

    Operation IceBridge acquired 1500 km of geophysical data, at 10 km spacing, in front of the Thwaites Glacier grounding line during the 2009 season. The gravity anomalies recorded by the survey have been used to model the bathymetry of the sea floor in front of the glacier, an area inaccessible to previous surveys. The resulting map reveals previously unseen detail of the Thwaites grounding zone, as well as the spatial extent of features that were formerly only known as points affecting the ice surface. The modeled bathymetry in front of Thwaites Glacier is marked by an undulating ridge running sub-parallel to the grounding line, 40 km seaward. The highest peak on the ridge is in contact with the overlying ice shelf, hindering its flow. Ridge elevation decreases to the west, with a maximum ridge depth of 850 m and an average relief of 350 m. This is comparable in scale to the recently identified ridge crossing the channel of nearby Pine Island Glacier (Jenkins et al., 2010). The present-day grounding line of Thwaites appears to be marked by a more subdued ridge, in which we have identified a 20 km wide hollow, to a water depth of 1200 m. Our model shows that this hollow corresponds to a landward bight in the grounding line, in the region through which the fast ice flow of Thwaites Glacier is focused. This correlation was not visible on previous, coarser scale maps of the grounding line, and shows a clear relationship between the bathymetry and ice flow. Gravity inversions have been constrained by nearby marine surveys, satellite images of the ice rise at the peak of the ridge and radar and laser data from the IceBridge survey to constrain ice thickness. The absolute values of predicted bathymetry are dependent on the density of the rocks in the subsurface, for example the presence or absence of volcanic material or loose sediments. Some models of the geology of the survey area are also proposed. Uncertainty of underlying geology may account for ~100 m errors in the

  6. Summer Arctic Sea Ice Intra-Seasonal Predictability Using a Vector Auto-Regressive Model

    NASA Astrophysics Data System (ADS)

    Ting, M.; Wang, L.; Yuan, X.

    2014-12-01

    Recent Arctic sea ice changes have important societal and economic impacts: the accelerated melting of Arctic sea ice in summer provides new fishery opportunities and increases the feasibility of trans-Arctic shipping, yet it may also lead to adverse effects on the Arctic ecosystem, weather and climate. Understanding the predictability of Arctic sea ice melting is thus an important task. A Vector Auto-Regressive (VAR) model is evaluated for predicting the summer time (May through September) daily Arctic sea ice concentrations. The intra-seasonal forecast skill of the Arctic sea ice is assessed using 1979-2012 satellite data provided by the National Snow & Ice Data Center (NSIDC). The cross-validated forecast skill of the VAR model is superior over persistence and climatological seasonal cycle for a lead-time of 15~60 days, especially over marginal seas. In addition to capturing the general seasonal melt of sea ice, the VAR model is also able to capture the interannual variability of the melting, from partial melt of the marginal sea ice in the beginning of the period to almost a complete melt in the later years. While the detailed mechanism leading to the high predictability of intra-seasonal sea ice concentration needs to be further examined, the study reveals for the first time that Arctic sea ice concentration can be predicted statistically with reasonable skills at the intra-seasonal time scales.

  7. 78 FR 12595 - Safety Zone for Ice Conditions; Baltimore Captain of the Port Zone

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-25

    ...) 366-9826. SUPPLEMENTARY INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal... the January 17, 2008, issue of the Federal Register (73 FR 3316). 4. Public Meeting We do not now plan... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone for Ice Conditions; Baltimore Captain of...

  8. Seasonal Variability in Vadose zone biodegradation at a crude oil pipeline rupture site

    USGS Publications Warehouse

    Sihota, Natasha J.; Trost, Jared J.; Bekins, Barbara; Berg, Andrew M.; Delin, Geoffrey N.; Mason, Brent E.; Warren, Ean; Mayer, K. Ulrich

    2016-01-01

    Understanding seasonal changes in natural attenuation processes is critical for evaluating source-zone longevity and informing management decisions. The seasonal variations of natural attenuation were investigated through measurements of surficial CO2 effluxes, shallow soil CO2 radiocarbon contents, subsurface gas concentrations, soil temperature, and volumetric water contents during a 2-yr period. Surficial CO2 effluxes varied seasonally, with peak values of total soil respiration (TSR) occurring in the late spring and summer. Efflux and radiocarbon data indicated that the fractional contributions of natural soil respiration (NSR) and contaminant soil respiration (CSR) to TSR varied seasonally. The NSR dominated in the spring and summer, and CSR dominated in the fall and winter. Subsurface gas concentrations also varied seasonally, with peak values of CO2 and CH4 occurring in the fall and winter. Vadose zone temperatures and subsurface CO2 concentrations revealed a correlation between contaminant respiration and temperature. A time lag of 5 to 7 mo between peak subsurface CO2 concentrations and peak surface efflux is consistent with travel-time estimates for subsurface gas migration. Periods of frozen soils coincided with depressed surface CO2 effluxes and elevated CO2 concentrations, pointing to the temporary presence of an ice layer that inhibited gas transport. Quantitative reactive transport simulations demonstrated aspects of the conceptual model developed from field measurements. Overall, results indicated that source-zone natural attenuation (SZNA) rates and gas transport processes varied seasonally and that the average annual SZNA rate estimated from periodic surface efflux measurements is 60% lower than rates determined from measurements during the summer.

  9. Ku band airborne radar altimeter observations of marginal sea ice during the 1984 Marginal Ice Zone Experiment

    NASA Technical Reports Server (NTRS)

    Drinkwater, Mark R.

    1991-01-01

    Pulse-limited, airborne radar data taken in June and July 1984 with a 13.8-GHz altimeter over the Fram Strait marginal ice zone are analyzed with the aid of large-format aerial photography, airborne synthetic aperture radar data, and surface observations. Variations in the radar return pulse waveforms are quantified and correlated with ice properties recorded during the Marginal Ice Zone Experiment. Results indicate that the wide-beam altimeter is a flexible instrument, capable of identifying the ice edge with a high degree of accuracy, calculating the ice concentration, and discriminating a number of different ice classes. This suggests that microwave radar altimeters have a sensitivity to sea ice which has not yet been fully exploited. When fused with SSM/I, AVHRR and ERS-1 synthetic aperture radar imagery, future ERS-1 altimeter data are expected to provide some missing pieces to the sea ice geophysics puzzle.

  10. Prospects for improved seasonal Arctic sea ice predictions from multivariate data assimilation

    NASA Astrophysics Data System (ADS)

    Massonnet, François; Fichefet, Thierry; Goosse, Hugues

    2015-04-01

    Predicting the summer Arctic sea ice conditions a few months in advance has become a challenging priority. Seasonal prediction is partly an initial condition problem; therefore, a good knowledge of the initial sea ice state is necessary to hopefully produce reliable forecasts. Most of the intrinsic memory of sea ice lies in its thickness, but consistent and homogeneous observational networks of sea ice thickness are still limited in space and time. To overcome this problem, we constrain the ocean-sea ice model NEMO-LIM3 with gridded sea ice concentration retrievals from satellite observations using the ensemble Kalman filter. No sea ice thickness products are assimilated. However, thanks to the multivariate formalism of the data assimilation method used, sea ice thickness is globally updated in a consistent way whenever observations of concentration are available. We compare in this paper the skill of 27 pairs of initialized and uninitialized seasonal Arctic sea ice hindcasts spanning 1983-2009, driven by the same atmospheric forcing as to isolate the pure role of initial conditions on the prediction skill. The results exhibit the interest of multivariate sea ice initialization for the seasonal predictions of the September ice concentration and are particularly encouraging for hindcasts in the 2000s. In line with previous studies showing the interest of data assimilation for sea ice thickness reconstruction, our results thus show that sea ice data assimilation is also a promising tool for short-term prediction, and that current seasonal sea ice forecast systems could gain predictive skill from a more realistic sea ice initialization.

  11. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    USGS Publications Warehouse

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D; Winslow, Luke; Korhonen, Johanna; Yasuyuki Aono

    2016-01-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality.

  12. Direct observations of ice seasonality reveal changes in climate over the past 320-570 years.

    PubMed

    Sharma, Sapna; Magnuson, John J; Batt, Ryan D; Winslow, Luke A; Korhonen, Johanna; Aono, Yasuyuki

    2016-01-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443-2014) for Lake Suwa, Japan, and of ice breakup dates (1693-2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality. PMID:27113125

  13. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    NASA Astrophysics Data System (ADS)

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D.; Winslow, Luke A.; Korhonen, Johanna; Aono, Yasuyuki

    2016-04-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality.

  14. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    PubMed Central

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D.; Winslow, Luke A.; Korhonen, Johanna; Aono, Yasuyuki

    2016-01-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality. PMID:27113125

  15. Processes and imagery of first-year fast sea ice during the melt season

    NASA Technical Reports Server (NTRS)

    Holt, B.; Digby, S. A.

    1985-01-01

    In June and July 1982, a field program was conducted in the Canadian Arctic on Prince Patrick Island to study sea ice during the melt season with in situ measurements and microwave instrumentation operated near the surface and from aircraft. The objective of the program was to measure physical characteristics together with microwave backscatter and emission coefficients of sea ice during this major period of transition. The present paper is concerned with a study of both surface measurements and imagery of first-year fast ice during the melt season. The melting process observed in first-year fast ice was found to begin with the gradual reduction of the snow cover. For a two- to three-day period in this melt stage, a layer of superimposed ice nodules formed at the snow/ice interface as meltwater froze around ice and snow grains.

  16. Grounding Zone Process: Ice Mechanics and Margin Lakes, Kamb Ice Stream and Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Fried, Mason

    The lateral "corners" where Kamb and Whillans Ice Streams (KIS and WIS) discharge into the Ross Ice Shelf share common geometries and ice mechanical settings. At both corners of the now-stagnant KIS outlet, shear margins of apparently different ages confine regions with a relatively flat, smooth surface expression. These features are called the "Duckfoot" on the northern, right-lateral side and the "Goosefoot" on the other. It has been suggested, on evidence found in ice internal layers, that the flat ice terrains on KIS were afloat in the recent past, at a time when the ice stream grounding line was upstream of its present location. The overdeepening in the bed just upstream of the KIS grounding line supports this view of the past geometry. The right-lateral margin at the outlet of the currently active WIS, the location of Subglacial Lake Englehardt (SLE), appears to have many similarities with the right lateral margin of KIS, though with a less developed looking inboard margin. This paper presents a mechanical analysis using surface and bed topography and velocity datasets comparing the Duckfoot flat ice terrain with the terrain around Subglacial Lake Englehardt. At both locations mechanical thinning along shear margins and lows in the bed topography redirects basal water routing towards the features. Here, I consider the history of these features and their role in ice stream variability by comparison of the relict and modern features and via numerical modeling of ice shelf grounding and ungrounding in response to variations in ice flow. We propose two scenarios for the development of flat ice terrains/subglacial lakes at the outlets of ice streams. In the first, development of a lake in the hydraulic potential low along a shear margin forces a margin jump as shearing develops along the inboard shore of the margin lake. This thesis presents evidence for an inboard (relative to the main outboard shear margin) zone of shear along the inboard shoreline of SLE

  17. Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Heimbürger, Lars-Eric; Sonke, Jeroen E.; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T.; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers

    2015-05-01

    Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79-90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81-85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea ice, extension of the seasonal sea ice zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.

  18. Stability and climate sensitivity of seasonal sea ice: a theoretical framework.

    NASA Astrophysics Data System (ADS)

    Deweaver, E. T.

    2006-12-01

    A simple "toy" model is devised to study the stability and climate sensitivity of oceanic regions which are sea- ice covered in winter but ice free in summer. The premise of the model is that the rates of ice freezing and melting and ice-free mixed layer warming and cooling are determined by external climate forcing, independently of the lengths of the seasons. The system adjusts to changes in external climate forcing through changes in the lengths of the freezing, melting, cooling, and warming seasons. We first examine the stability of the seasonal ice states with respect to perturbations in the start dates of the seasons. Stability can be assessed by considering the ratio of the freezing rate to the melting rate or the ratio of the mixed layer warming and cooling rates. More simply, stability can be assessed by comparing the durations of the freezing and melting seasons or the durations of the warming and cooling seasons. Roughly speaking, the seasonal ice climate is stable if the ice "wants" to melt but the mixed layer "wants" to freeze. To examine the sensitivity of the seasonal ice climate to changes in external climate forcing we construct a 4- by-4 matrix which can be solved for the lengths of the four seasons. The matrix then is reduced to two equations for the lengths of the ice freezing and mixed layer cooling seasons. The lengths of the freezing and cooling seasons can be represented by the intersection of the lines representing the two equations. When the system is stable with respect to initial conditions, a shift to warmer climate forcing causes the intersection of the two lines to move upward and to the left, signifying a transition to a longer ice-free cooling season and a shorter ice-covered freezing season. Finally, we compare the climate sensitivity of two versions of the toy model, one in which the rates are determined entirely by external climate forcing and one in which the lengths of the seasons can influence the rates (a nonlinear

  19. Influence of timing of sea ice retreat on phytoplankton size during marginal ice zone bloom period in the Chukchi and Bering shelves

    NASA Astrophysics Data System (ADS)

    Fujiwara, A.; Hirawake, T.; Suzuki, K.; Eisner, L.; Imai, I.; Nishino, S.; Kikuchi, T.; Saitoh, S. I.

    2015-08-01

    Timing of sea ice retreat (TSR) as well as cell size of primary producers (i.e., phytoplankton) plays crucial roles in seasonally ice-covered marine ecosystem. Thus, it is important to monitor the temporal and spatial distribution of phytoplankton community size structure. Prior to this study, an ocean color algorithm has been developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll a derived from the cells larger than 5 μm to the total chl a using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analyzed pixel-by-pixel relationships between FL during marginal ice zone (MIZ) bloom period and TSR over a period of 1998-2013. The influence of TSR on sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and TSR was widely found in the shelf region during MIZ bloom season. On the other hand, we found a significant positive (negative) relationship between SST (ΔOHC) and TSR. That is, earlier sea-ice retreat was associated with a dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that duration of nitrate supply, which is important for large-sized phytoplankton growth in this region (i.e., diatoms), can change according to TSR. In addition, under-ice phytoplankton blooms are likely to occur in years with late ice retreat, because sufficient light for phytoplankton growth can pass through the ice and penetrate into the water columns due to an increase in solar radiation toward the summer solstice. Moreover, we found not only the length of ice-free season but also annual median of FL positively correlated with annual net primary production (APP). Thus, both phytoplankton community composition and growing season are important for APP in the study area. Our findings showed quantitative relationship between the inter-annual variability of FL

  20. Influence of timing of sea ice retreat on phytoplankton size during marginal ice zone bloom period on the Chukchi and Bering shelves

    NASA Astrophysics Data System (ADS)

    Fujiwara, A.; Hirawake, T.; Suzuki, K.; Eisner, L.; Imai, I.; Nishino, S.; Kikuchi, T.; Saitoh, S.-I.

    2016-01-01

    The size structure and biomass of a phytoplankton community during the spring bloom period can affect the energy use of higher-trophic-level organisms through the predator-prey body size relationships. The timing of the sea ice retreat (TSR) also plays a crucial role in the seasonally ice-covered marine ecosystem, because it is tightly coupled with the timing of the spring bloom. Thus, it is important to monitor the temporal and spatial distributions of a phytoplankton community size structure. Prior to this study, an ocean colour algorithm was developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll a (chl a) derived from cells larger than 5 µm to the total chl a, using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analysed the pixel-by-pixel relationships between FL during the marginal ice zone (MIZ) bloom period and TSR over the period of 1998-2013. The influences of the TSR on the sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and the TSR was widely found in the shelf region during the MIZ bloom season. However, we found a significant positive (negative) relationship between the SST (ΔOHC) and TSR. Specifically, an earlier sea ice retreat was associated with the dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that the duration of the nitrate supply, which is important for the growth of large-sized phytoplankton in this region (i.e. diatoms), can change according to the TSR. In addition, under-ice phytoplankton blooms are likely to occur in years with late ice retreat, because sufficient light for phytoplankton growth can pass through the ice and penetrate into the water columns as a result of an increase in solar radiation toward the summer solstice

  1. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

    USGS Publications Warehouse

    Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

    2006-01-01

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

  2. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap.

    PubMed

    Kieffer, Hugh H; Christensen, Philip R; Titus, Timothy N

    2006-08-17

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. PMID:16915284

  3. Polygonal cracks in the seasonal semi-translucent CO2 ice layer in Martian polar areas

    NASA Astrophysics Data System (ADS)

    Portyankina, Ganna; Pommerol, Antoine; Aye, Klaus-Michael; Hansen, Candice J.; Thomas, Nicolas

    2012-02-01

    In this paper, we use morphological and numerical methods to test the hypothesis that seasonally formed fracture patterns in the Martian polar regions result from the brittle failure of seasonal CO2 slab ice. The observations by the High Resolution Imaging Science Experiment (HiRISE) of polar regions of Mars show very narrow dark elongated linear patterns that are observed during some periods of time in spring, disappear in summer and re-appear again in the following spring. They are repeatedly formed in the same areas but they do not repeat the exact pattern from year to year. This leads to the conclusion that they are cracks formed in the seasonal ice layer. Some of models of seasonal surface processes rely on the existence of a transparent form of CO2 ice, so-called slab ice. For the creation of the observed cracks the ice is required to be a continuous media, not an agglomeration of relatively separate particles like a firn. The best explanation for our observations is a slab ice with relatively high transparency in the visible wavelength range. This transparency allows a solid state green-house effect to act underneath the ice sheet raising the pressure by sublimation from below. The trapped gas creates overpressure and the ice sheet breaks at some point creating the observed cracks. We show that the times when the cracks appear are in agreement with the model calculation, providing one more piece of evidence that CO2 slab ice covers polar areas in spring.

  4. Surf Zone Hyperbenthos of Belgian Sandy Beaches: Seasonal Patterns

    NASA Astrophysics Data System (ADS)

    Beyst, B.; Buysse, D.; Dewicke, A.; Mees, J.

    2001-12-01

    Since surf zone hyperbenthos, although highly important in local food webs, has often been neglected and very little information is available, a survey of the Belgian sandy beaches was carried out from May 1996 until July 1997. Monthly samples were taken to give a complete record of hyperbenthic organisms occurring in the surf zone of Belgian sandy beaches and to evaluate the intensity by which this surf zone is used. In total 172 species were recorded. The number of species occurring in the surf zone is comparable to that of adjacent areas. As well as true hyperbenthic species, endobenthic and planktonic organisms were sampled. More than 75% of the average total sample composition consisted of mysids, mainly Mesopodopsis slabberi, Schistomysis spiritus and Schistomysis kervillei (holohyperbenthos). Apart from several resident species, active and passive seasonal migration towards the surf zone by a number of species is suggested. A large number of sporadic species adds to the composition of surf zone hyperbenthos. Within the merohyperbenthos, postlarval decapods and fish were the dominant organisms. During the year three recruitment peaks were observed. Average densities per month exceeded 1500 ind. 100 m -2. Yearly biomass averages ranged from 300 to over 3000 mg ADW 100 m -2. Densities of the common species are slightly higher in the surf zone than in other habitats, emphasising the importance of the area. Besides a possible nursery function, the surf zone may also be used as a transient area between different habitats. Finally, the influence of several abiotic factors on the hyperbenthic assemblages was evaluated. The main structuring variables determining the occurrence of most of the organisms are water temperature and hydrodynamic factors such as wave height and turbidity. The influence of wave height seems to be two-fold: several good swimmers such as mysids and some fish species are suggested to be able to actively avoid severe wave conditions, whereas

  5. Seasonal variability of ice nuclei over Central Europe

    NASA Astrophysics Data System (ADS)

    Klein, Holger; Nickovic, Slobodan; Schuetz, Lothar; Weinbruch, Stephan; Levin, Zev; Andreae, Meinrat; Barrie, Leonard; Ebert, Martin; Bundke, Ulrich; Bingemer, Heinz

    2010-05-01

    The abundance of ice nuclei (IN) has been measured every day since April 2008 at the Taunus Observatory on Mt. Kleiner Feldberg (50.22°N, 8.45°E, 825 m. above sea level) at 20 km north of Frankfurt / M., Germany. Aerosol samples were collected on silicon wafers by an electrical aerosol precipitator and analyzed for IN number concentration (condensation and deposition freezing modes) using the static vapor diffusion chamber FRIDGE (Klein et al., Atmos. Res, doi:10.1016/j.atmosres.2009.08.002, 2009). Around 800 samples were analyzed so far. The IN number concentration shows a pronounced seasonal signal with about a factor of 10 higher ice nuclei in summer than in winter. Desert dust transported over long distances appears to be the dominant contributor to IN at the site. Episodes of Sahara dust transport are well represented by individual peaks in the IN record and identified by airmass trajectories, transport modelling and mineralogical analysis. The contribution of mineral dust to IN is further corroborated by the covariance of the individual IN concentrations with the aerosol optical depth (AOD) due to extinction by large particles, which was measured simultaneously at the AERONET site (Max-Planck-Institute for Chemistry) at Mainz, 20 km southwest of our site. The relation between IN and AOD not only holds for our individual daily measurements, but is also valid for the monthly means of our IN record, which are highly correlated to the multi-year monthly means of coarse and middle-sized dust AOD which is derived from the Multi-angle Imaging SpectroRadiometer (MISR) satellite instrument (http://eosweb.larc.nasa.gov/cgi-bin/misr_tools/clim_likely.cgi ) for the grid point closest to our site. Acknowledgements: We gratefully acknowledge funding of this work by the Deutsche Forschungsgemeinschaft (DFG) as part of the collaborative research centre Die troposphärische Eisphase (SFB641) and by the German-Israeli Foundation (GIF).

  6. Variations in the Sea Ice Edge and the Marginal Ice Zone on Different Spatial Scales as Observed from Different Satellite Sensor

    NASA Technical Reports Server (NTRS)

    Markus, Thorsten; Henrichs, John

    2006-01-01

    and volume scattering characteristics. The Canadian RADARSAT C-band SAR provides data that cover the Arctic Ocean and the MIZ every 3 days. A change-point detection approach was utilized to obtain an ice edge estimate from the RADARSAT data The Quickscat scatterometer provides ice edge information with a resolution of a few kilometers on a near-daily basis. During portions of March and April of 2003 a series of aircraft flights were conducted over the ice edge in the Bering Sea carrying the Polarimetric Scanning Radiometer (PSR), which provides spectral coverage identical with the AMSR-E instrument at a resolution of 500 meters. In this study we investigated these different data sets and analyzed differences in their definition of the sea ice edge and the marginal ice zone and how these differences as well as their individual limitations affect the monitoring of the ice edge dynamics. We also examined how the nature of the sea ice edge, including its location, compactness and shape, changes over the seasons. Our approach was based on calculation of distances between ice edges derived from the satellite and aircraft data sets listed above as well as spectral coherence methods and shape parameters such as tortuosity, curvature, and fractional dimension.

  7. Dynamics of coupled ice-ocean system in the marginal ice zone: Study of the mesoscale processes and of constitutive equations for sea ice

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.

    1984-01-01

    This study is aimed at the modelling of mesoscale processed such as up/downwelling and ice edge eddies in the marginal ice zones. A 2-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model (f-plane) through interfacial stresses. The constitutive equations of the sea ice are formulated on the basis of the Reiner-Rivlin theory. The internal ice stresses are important only at high ice concentrations (90-100%), otherwise the ice motion is essentially free drift, where the air-ice stress is balanced by the ice-water stress. The model was tested by studying the upwelling dynamics. Winds parallel to the ice edge with the ice on the right produce upwilling because the air-ice momentum flux is much greater that air-ocean momentum flux, and thus the Ekman transport is bigger under the ice than in the open water. The upwelling simulation was extended to include temporally varying forcing, which was chosen to vary sinusoidally with a 4 day period. This forcing resembles successive cyclone passings. In the model with a thin oceanic upper layer, ice bands were formed.

  8. Martian Seasonal CO2 Frost Indicating Decameter-Scale Variability in Buried Water Ice

    NASA Astrophysics Data System (ADS)

    Mellon, M. T.; Hansen, C. J.; Cull, S.; Arvidson, R. E.; Searls, M.

    2011-12-01

    Several new lines of evidence indicate that subsurface water ice (ground ice) on Mars is more complexly distributed, and in variable concentrations, than had been previously envisioned. Understanding the current distribution of ground ice is a fundamental part of understanding how this ice was emplaced and the recent past climate conditions under which icy deposits formed and subsequently evolved. In this work we examine the seasonal defrosting of CO2 observed by HiRISE as an indicator of decameter-scale ground-ice heterogeneity. It is well known that CO2 dry ice accumulates on the martian surface in winter. The amount of dry ice and the time it spends on the ground depends strongly on surface properties. A readily observable attribute is the "crocus date", the season (Ls) when CO2 completely sublimates, exposing the soil surface. Many factors can affect the crocus date, but perhaps most important are the properties of CO2 frost and of the surface soil. We examine HiRISE observations, spanning more than a martian year, for decameter-scale patterns of CO2 frost and the crocus date. Year-to-year repeatability of CO2 ice patterns, both in polygon troughs and decameter-size patches, along with a lack of topography nor aeolian redistribution, suggests that differences in the surface substrate is the root cause for these patterns. In addition, only CO2 slab ice (solid, non-porous dry ice) is indicated throughout the observed seasons and at all spatial scales (down to meter scale), as evidenced by albedo (HiRISE and TES) and IR spectra (CRISM). In addition, the low emissivity and high albedo of fine-grained particulate CO2 frost would result in a crocus date much earlier than even the earliest observed. We present two scenarios of substrate differences which explain the observations: (i) the ice-table depth varies away from atmospheric equilibrium, such that a thicker "dry-soil" layer occurs in disequilibrium where the CO2 ice lingers longest; and (ii) the H2O

  9. Spatial patterns in the length of the sea ice season in the Southern Ocean, 1979-1986

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1994-01-01

    The length of the sea ice season summarizes in one number the ice coverage conditions for an individual location for an entire year. It becomes a particularly valuable variable when mapped spatially over a large area and examined for regional and interannual differences, as is done here for the Southern Ocean over the years 1979-1986, using the satellite passive microwave data of the Nimbus 7 scanning multichannel microwave radiometer. Three prominent geographic anomalies in ice season lengths occur consistently in each year of the data set, countering the general tendency toward shorter ice seasons from south to north: (1) in the Weddell Sea the tendency is toward shorter ice seasons from southwest to northeast, reflective of the cyclonic ice/atmosphere/ocean circulations in the Weddell Sea region. (2) Directly north of the Ross Ice Shelf anomalously short ice seasons occur, lasting only 245-270 days, in contrast to the perennial ice coverage at comparable latitudes in the southern Bellingshausen and Amundsen Seas and in the western Weddell Sea. The short ice season off the Ross Ice Shelf reflects the consistently early opening of the ice cover each spring, under the influence of upwelling along the continental slope and shelf and atmospheric forcing from winds blowing off the Antarctic continent. (3) In the southern Amundsen Sea, anomalously short ice seasons occur adjacent to the coast, owing to the frequent existence of coastal polynyas off the many small ice shelves bordering the sea. Least squares trends in the ice season lengths over the 1979-1986 period are highly coherent spatially, with overall trends toward shorter ice seasons in the northern Weddell and Bellingshausen seas and toward longer ice seasons in the Ross Sea, around much of East Antarctica, and in a portion of the south central Weddell Sea.

  10. Current trends in seasonal ice storage. [Compilation of projects

    SciTech Connect

    Gorski, A.J.

    1986-05-01

    This document is a compilation of modern research projects focused upon the use of naturally grown winter ice for summer cooling applications. Unlike older methods of ice-based cooling, in which ice was cut from rivers and lakes and transported to insulated icehouses, modern techniques grow ice directly in storage containers - by means of heat pipes, snow machines, and water sprays - at the site of application. This modern adaptation of an old idea was reinvented independently at several laboratories in the United States and Canada. Applications range from air conditioning and food storage to desalinization.

  11. High-resolution wave forecasting system for the seasonally ice-covered Baltic Sea

    NASA Astrophysics Data System (ADS)

    Tuomi, Laura; Lehtiranta, Jonni

    2016-04-01

    When forecasting surface waves in seasonally ice-covered seas, the inclusion of ice conditions in the modelling is important. The ice cover affects the propagation and also changes the fetch over which the waves grow. In wave models the ice conditions are often still given as a boundary condition and handled by excluding areas where the ice concentration exceeds a certain threshold value. The ice data used are typically based on satellite analysis or expert analysis of local Ice Services who combine data from different sources. This type of data is sufficiently accurate to evaluate the near-real time ice concentrations, but when making forecasts it is also important to account for the possible changes in ice conditions. For example in a case of a high wind situation, there can be rapid changes in the ice field, when the wind and waves may push the ice towards shores and cause fragmentation of ice field. To enhance handling of ice conditions in the Baltic Sea wave forecasts, utilisation of ice model data was studied. Ice concentration, thickness produced by FMI's operational ice model HELMI were used to provide ice data to wave model as follows: Wave model grid points where the ice concentration was more than or equal to 70% and the ice thickness more than1 cm, were excluded from calculations. Ice concentrations smaller than that were taken into account as additional grid obstructions by decreasing the wave energy passed from one grid cell to another. A challenge in evaluating wave forecast accuracy in partly ice covered areas it that there's typically no wave buoy data available, since the buoys have to be recovered well before the sea area freezes. To evaluate the accuracy of wave forecast in partially ice covered areas, significant wave heights from altimeter's ERS2, Envisat, Jason-1 and Jason-2 were extracted from Ifremer database. Results showed that the more frequent update of the ice data was found to improve the wave forecast especially during high wind

  12. A two-dimensional thermodynamic model for sea ice advance and retreat in the Newfoundland marginal ice zone

    NASA Astrophysics Data System (ADS)

    Tang, C. L.

    1991-03-01

    A time dependent two-dimensional ice-ocean coupled thermodynamic model is developed to study the ice edge advance and retreat, development of the oceanic mixed layer, and oceanic response to ice movement, ice melt, and heat balance in the Newfoundland marginal ice zone. The model domain is a vertical section of the ocean along the direction of the ice velocity. Initially, the ocean is free of ice and has a deep mixed layer formed by winter surface cooling. An ice sheet then moves into the domain from the upstream boundary at constant velocity. It melts from the bottom and a shallow mixed layer beneath the ice is developed. Heat and buoyancy fluxes at the air-sea and ice-water interfaces and at the bottom of the mixed layer determine the melt rate and change of the mixed layer properties. The ice edge reaches a maximum distance and starts to retreat when the ice is being melted by the warm water faster than it is being advected into the area. The oceanic properties change with the ice movement. During the advancing phase of the ice movement, the heat loss to the ice bottom from ice melting exceeds the heat gain by surface heating and entrainment, causing the mixed layer temperature to drop. But since the buoyancy created by the melting is not sufficient to overcome the effect of wind mixing, the mixed layer deepens rapidly. During the retreating phase, the mixed layer becomes shallower and warmer because of the increasing surface heating and buoyance production by ice melting. The most important factors controlling the melt rate and the excursion distance are the air temperature and the ambient water temperature. Higher wind speeds increase the mixed layer depth but do not have a strong effect on the melt rate.

  13. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Hopkins, Thomas L.; Torres, Joseph J.

    1989-04-01

    The structure of the food web in the vicinity of a marginal ice zone was investigated in the western Weddell Sea during austral autumn 1986. The diets of 40 species of zooplankton and micronekton occurring in the epipelagic zone were examined and compared using non-hierarchical clustering procedures. Over half the species were in three clusters of predominantly small-particle (phytoplankton; protozoans) grazers. These included biomass dominants Calanoides acutus, Calanus propinquus, Metridia gerlachei and Salpa thompsoni. Six clusters contained omnivores that had diets consisting of small particles as well as a substantial fraction of metazoan food. Among these was Euphausia superba. Seven groups were carnivorous, including species of copepods (1), chaetognaths (3), and fishes (5). Copepods were the most frequent food of carnivores; however krill also were important in the diets of three fish species. Among small-particle grazers, phytoplankton occurred more frequently in guts of individuals from open water; carnivory was more in evidence in samples collected under the pack ice. Regional comparisons of material taken on this and several previous cruises indicate that, in most of the dominant species, diets remain relatively consistent with respect to major food categories. Seasonal impact on feeding dynamics appears to be great: the guts of grazing species were generally much more full (visual evidence) during summer bloom conditions than during the autumn. The following trophic sequence is suggested for grazing zooplankton species in ice-covered regions of the Antarctic: (1) Active small-particle grazing during the summer bloom period; (2) reduced ingestion rates in autumn as primary production declines and the system becomes more oligotrophic, with some species augmenting grazing with carnivory; (3) descent of zooplankton biomass species into the mesopelagic zone in late autumn-early winter with feeding largely terminated. The sequence applies to the dominant

  14. 77 FR 2017 - Safety Zone; Ice Rescue Exercise; Green Bay, Dyckesville, WI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-13

    ... multiple agencies. The Captain of the Port Sector Lake has determined that this ice rescue exercise will... Port, Sector Lake Michigan, will be in the area of the ice rescue exercise at all times. (4) People or... SECURITY Coast Guard 33 CFR PART 165 RIN 1625-AA00 Safety Zone; Ice Rescue Exercise; Green Bay,...

  15. Seasonal ice cycle at the Mars Phoenix landing site: 2. Postlanding CRISM and ground observations

    NASA Astrophysics Data System (ADS)

    Cull, Selby; Arvidson, R. E.; Morris, R. V.; Wolff, M.; Mellon, M. T.; Lemmon, M. T.

    2010-05-01

    The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ˜10 km diameter Heimdal Crater, located ˜10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine-grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger-grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ˜ 109°, ˜9 sols before Phoenix’s Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ˜ 155°, after Phoenix operations ended.

  16. Melt Pond Development on Arctic Land-Fast Sea Ice in Relation to Snow and Ice Properties During the Ice Growth Season

    NASA Astrophysics Data System (ADS)

    Petrich, C.; Eicken, H.; Pringle, D.; Sturm, M.; Perovich, D.; Polashenski, C.; Finnegan, D.

    2008-12-01

    The dynamics of melt pond development on sea ice were studied on a well-defined patch of level land-fast sea ice off the coast of Barrow, Alaska in 2008. The pond development was correlated with both sea ice properties and the history of snow distribution during the ice growth season. In mid January, the ice was covered by an almost level snow layer of 4~cm thickness. We observed an increase in snow depth and development of snow dunes since February. At least some snow dunes stayed in place, and at the end of April ice thickness was negatively correlated with the thickness of compacted snow dunes. Snow salinity remained above 5~psu in the bottom 4 to 5~cm of the snow pack throughout the ice growth season. In comparison, snow more than 5~cm above the snow--ice interface was almost devoid of salt. The air temperature increased rapidly in early May and started to exceed 0°C on May 15. From this day on, thermistor string data show that the sea ice temperature profile deviated from linear with the lowest temperature inside the body of ice rather than at the surface. Superimposed ice was present with certainty after May 24. The superimposed ice investigated in early June exhibited a rough texture consistent with meltwater percolation columns in the snow pack. It was found only under snow dunes; no superimposed ice was observed under thin snow (2~cm) or melt ponds. Meltwater collected at topographic low points that surrounded distinct ice islands. Aerial photography and surface LiDAR measurements at various times during the early melt season showed that the location of these ice islands coincided with the locations of wind packed snow dunes that had been tracked since February. The lateral movement of surface waters was relatively slow during the very early stages of melt pond formation. However, we observed a significant lateral redistribution of meltwater under the ice surface; this redistribution happened through distinct veins. The sea ice salinity profiles showed

  17. The leading role of ammonium in the nitrogen uptake regime of Southern Ocean marginal ice zones

    NASA Astrophysics Data System (ADS)

    Goeyens, L.; Tréguer, P.; Baumann, M. E. M.; Baeyens, W.; Dehairs, F.

    1995-06-01

    The nitrogen signature of marginal ice zones in the Southern Ocean often departs from the "classical" Antarctic nutrient profiles with high nitrate and low ammonium values in the surface layer. Weddell Sea marginal ice zones e.g. show enhanced nitrate depletions, amounting to ~ 500 mmol N m -2. Additionally, ammonium stocks in the upper layer can be up to 7% of the inorganic nitrogen pool. The corresponding nitrogen uptake regime suggests elevated nitrate assimilation during the early phase of the productive season and significantly reduced nitrate assimilation at a later stage. Absolute as well as specific nitrate uptake rates decrease by an order of magnitude when ammonium stocks exceed 1.7% of the total inorganic nitrogen. The variability in nitrogen utilisation reflects physiological changes in the phytoplankton assemblage. In response to increased ammonium stocks phytoplankton show a reduction in their capacity to take up nitrate and following an initial diatom bloom non-siliceous phytoplankton become predominant in a regenerated production regime.

  18. Seasonal reversal at Miryang Eoreumgol (Ice Valley), Korea: observation and monitoring

    NASA Astrophysics Data System (ADS)

    Byun, Hi-Ryong; Tanaka, Hiroshi L.; Choi, Pom-Yong; Kim, Do-Woo

    2011-12-01

    We investigate an anomalous phenomenon evident in the Miryang Eoreumgol (Ice Valley), Korea: The wind and water are cold during summer and warm during winter, and ice formation does not occur in winter but in summer. We have initiated observations and investigations into the origin of heat sources particularly with regard to the mechanism of ice formation in summer. Previous theories, e.g., concerning underground gravity currents, water evaporation, diurnal and seasonal respirations of the talus, effects of ground heat, radiation and topography, etc., are considered. After a calculation of heat sources, we propose two new concepts—a repetitious heat separation mechanism and a positive feedback mechanism of cold air generation—to demonstrate that the heat mechanism of the seasonal reversal of the ice valley may be controlled by the use of the phase change between ice and water vapor with only a small amount of additional unknown energy.

  19. The 2003-04 Sea Ice Season at Barrow as Seen by Land-Based Radar

    NASA Astrophysics Data System (ADS)

    Robson, K. L.; Mahoney, A.; Eicken, H.

    2004-12-01

    The objective was to determine the position of the landfast sea ice edge and its morphology throughout the 2003-04 sea ice season near Barrow using a land-based 10 kW, X-band (3 cm) marine radar mounted on a building near the beach at the Ukpeagvik Inupiat Corporation Naval Artcic Research Laboratory (UIC-NARL). This data would then be used to help understand how landfast ice attaches to coast and what causes it to breakaway. An improved understanding together with real-time data available on the internet will provide more information for the safety of whalers, Native people, and the development of nearshore operations. X-band radar does not discriminate well between level ice and open water, since both areas are characterized by very low back-scatter, but it detects ice floes and rough ice that contain surfaces facing towards the radar. It is very effective at monitoring nearshore sea ice motion in a time series of data. Landfast ice can change very rapidly with break-offs and ice shoves occurring in a matter of hours and nearshore pack ice motion can reverse several times in one day. We were able to monitor these changes by the animation of radar images spaced at five-minute intervals. A very similar land-based radar was installed on the beach approximately 500m further towards Barrow between 1973 and 1979 (Shapiro and Metzner, 1991). In a comparison with this earlier study, the 2003-04 season was noted to be much more dynamic and there was less observed pack ice. In conjunction with field measurements, it was also observed that a stable fast ice edge does not necessarily correlate with a grounded ridge, contrary to the World Meteorological Organization's definition of fast ice.

  20. Seasonal-to-Decadal Predictions of Arctic Sea Ice: Challenges and Strategies

    NASA Astrophysics Data System (ADS)

    Richter-Menge, J.; Walsh, J. E.; Thomas, K.

    2012-12-01

    Arctic sea ice plays a number of important roles in moderating global climate and influencing oceanic and atmospheric circulation. The recent dramatic changes in the thickness and extent of the Arctic sea ice cover, which can be linked to the warming climate, are well-documented. Such changes in Arctic sea ice have various direct and indirect scientific, technological, and societal impacts such as the planning of new shipping ports, oil and gas exploration, increased marine transportation, as well as ecological changes. Currently, our limited understanding of the coupled and complex interactions between Arctic sea ice, oceans, and atmosphere hinders our ability to predict the rate and magnitude of future change. In addition, while a number of efforts are underway to better understand the role of Arctic sea ice in the broader context of the Arctic climate system, and to forecast sea ice, there is also a need to better understand the role that sea ice plays beyond the polar region. A 2012 National Research Council report, "Seasonal-to-Decadal Predictions of Arctic Sea Ice: Challenges and Strategies", explores current major challenges in sea ice prediction and identifies new methods, observations, and technologies that might advance seasonal-to-decadal sea ice predictive capabilities through improved understanding of the Arctic system. Based heavily on information generated at a large community workshop, the report examines current observations and modeling efforts of sea ice, and identifies (but does not prioritize) areas of research and technology advances needed to better understand current and future changes. The report places a particular emphasis on seasonal-to-decadal timescales.

  1. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics.

    PubMed

    Cherry, Seth G; Derocher, Andrew E; Thiemann, Gregory W; Lunn, Nicholas J

    2013-07-01

    Understanding how seasonal environmental conditions affect the timing and distribution of synchronized animal movement patterns is a central issue in animal ecology. Migration, a behavioural adaptation to seasonal environmental fluctuations, is a fundamental part of the life history of numerous species. However, global climate change can alter the spatiotemporal distribution of resources and thus affect the seasonal movement patterns of migratory animals. We examined sea ice dynamics relative to migration patterns and seasonal geographical fidelity of an Arctic marine predator, the polar bear (Ursus maritimus). Polar bear movement patterns were quantified using satellite-linked telemetry data collected from collars deployed between 1991-1997 and 2004-2009. We showed that specific sea ice characteristics can predict the timing of seasonal polar bear migration on and off terrestrial refugia. In addition, fidelity to specific onshore regions during the ice-free period was predicted by the spatial pattern of sea ice break-up but not by the timing of break-up. The timing of migration showed a trend towards earlier arrival of polar bears on shore and later departure from land, which has been driven by climate-induced declines in the availability of sea ice. Changes to the timing of migration have resulted in polar bears spending progressively longer periods of time on land without access to sea ice and their marine mammal prey. The links between increased atmospheric temperatures, sea ice dynamics, and the migratory behaviour of an ice-dependent species emphasizes the importance of quantifying and monitoring relationships between migratory wildlife and environmental cues that may be altered by climate change. PMID:23510081

  2. Quantifying Uncertainties in the Seasonal Cycle of Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Lucas, D. D.; Covey, C. C.; Klein, R.; Tannahill, J.; Ivanova, D. P.

    2013-12-01

    Many climate models project that the Arctic Ocean will be free of summertime sea ice within a century when forced with representative future greenhouse gas emission scenarios. To determine whether uncertainties in sea ice physics can also lead to an ice-free Arctic, we ran present-day ensemble simulations with the Community Climate System Model (CCSM4) that varied 7 parameters in the Community Ice Code (CICE4) over expert-provided ranges. The September minimum in sea ice extent computed by the ensemble ranges from 0.5 to 7.7 million km2, the lower end of which is significantly less than current observed values and lower than the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). CCSM4 can therefore simulate a summertime Arctic that is effectively free of sea ice either by increasing greenhouse gas forcing or by keeping the forcing constant and varying CICE4 parameters within recommended ranges. We identified three key CICE4 parameters related to radiative and thermal properties of snow that drive this extreme ensemble variability. Given observational data, machine learning algorithms were also used to quantify and constrain probability distribution functions for these parameters, which can be sampled to provide probabilistic assessments of sea ice characteristics simulated by CICE4. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was funded by the Uncertainty Quantification Strategic Initiative Laboratory Directed Research and Development Project at LLNL under project tracking code 10-SI-013 (UCRL LLNL-ABS-641752).

  3. Amplitude analysis of active source seismic data from the grounding zone of Whillans Ice Stream

    NASA Astrophysics Data System (ADS)

    Horgan, Huw; Anandakrishnan, Sridhar; Alley, Richard; Christianson, Knut

    2015-04-01

    Amplitude analysis of active source seismic data is often used to estimate acoustic properties and thereby infer the lithology of the substrate beneath glaciers and ice streams. The substrate beneath the ice streams of West Antarctica is of particular interest as here subglacial sediment deformation results in the rapid flow of the overriding ice. At the grounding zone, where the grounded ice sheet transitions to the floating ice shelf, this substrate is thought to stiffen due to tidal compaction resulting in a zone of higher basal shear stress which is manifest in the buckling of the internal layering in the overriding ice. Here we investigate these processes by estimating subglacial properties using active source seismic data acquired across the grounding zone of Whillans Ice Stream. Perhaps uniquely, we are able to test our methodology due to the survey crossing from an ice overlying sediment interface into a known ice overlying water interface. Our analysis indicates that lithological variations within the grounding zone are below the resolution of our methodology with the exception of a body of water trapped by a hydropotential reversal upstream of the grounding zone.

  4. Seasonality of Spectral Albedo and Transmission of Sea Ice in the Transpolar Drift, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Nicolaus, M.; Gerland, S.; Hudson, S.; Haapala, J.; Hanson, S.; Palo, T.; Perovich, D. K.

    2008-12-01

    The physical and optical properties of snow and sea ice in the Polar regions control the amount of solar short-wave radiation, reflected at the surface, scattered and absorbed within snow and ice, and transmitted into the ocean beneath. Albedo and transmissivity of snow and sea ice strongly influence heat fluxes within the coupled atmosphere-ice-ocean system, and by that the evolution of the sea ice. Spectral optical properties are crucial for primary production and evolution of sea ice related microorganisms and various bio-chemical processes. Furthermore, the increasing importance of remote sensors when studying snow and sea ice, raises the need for ground truth data of spectral optical and other physical properties of snow and sea ice. Spectral albedo and transmission were measured continuously within high spectral and temporal resolution during the transpolar drift of the drifting schooner "Tara" through the Arctic Basin between 30 April and 05 September 2007. Simultaneous in-situ measurements of snow and sea ice properties as well as a comprehensive meteorological program complement the dataset and allow common analysis and an integrated dataset. Results show significant seasonal changes and highlight key events during the transitions from spring to summer and summer to autumn; including formation, evolution, and freeze up of melt ponds. We were able to derive absolute values of energy transfer through snow and ice and into the upper ocean. The timing of changes in surface energy balance can be determined and characterized by including results from detailed snow and sea ice studies as temperature and density profiles, snow stratigraphy, and sea ice texture. Among others, they show that the melting period lasted 80 days which was about 20 days longer than on average. Interestingly, the observation period coincides with the time prior to the Arctic sea ice extent minimum in autumn 2007. Consequently, the findings might assist to understand and explain processes

  5. Subglacial Water and Sediment Transport across the Grounding Zone of Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Christianson, Knut; Horgan, Huw; Jacobel, Robert; Anandakrishnan, Sridhar; Alley, Richard; Muto, Atsuhiro; Craig, Brian; Dalla-Santa, Kevin; Gobel, Rebecca; Keisling, Benjamin; Synder, Lauren

    2013-04-01

    Much of the threshold behavior of marine ice sheets is thought to result from processes occurring at the grounding zone, where the ice sheet transitions into the ice shelf. At short time scales (decades to centuries) grounding zone behavior is likely to be influenced by processes not included in the current generation of ice sheet models. Here we report on two such processes: the flow of subglacial water from beneath the ice sheet, and the associated transport, and deposition, of sediment. We present a ground-based geophysical study across the grounding zone of a major West Antarctic Ice Stream (Whillans Ice Stream). Using a combination of active-source seismology and radio-echo sounding (RES) data, we image the outlet of a large subglacial drainage system. This drainage system deposits sediment, the lithology of which we determine with seismic amplitude analysis, into a thin (< 15 m) ocean water column. RES reflectivity indicates that subglacial deformation, subglacial water flow, and this ocean water column likely transport sediment along the base of the ice sheet and eventually the ice shelf. These findings have implications for the evolution of grounding zones and the basal melt of ice shelves; knowledge of both of which is required if well-informed models are to provide accurate estimates of future sea level rise.

  6. Using Airborne Lidar Data from IcePod to Measure Annual and Seasonal Ice Changes Over Greenland

    NASA Astrophysics Data System (ADS)

    Frearson, N.; Bertinato, C.; Das, I.

    2014-12-01

    The IcePod 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-ice radars, visible-wave and infrared cameras, and upward-looking pyrometer. These instruments allow us to image the ice from top to bottom, including the surface of melt-water plumes that originate at the ice-ocean boundary. In collaboration with the New York Air National Guard 109th Airlift Wing, the IcePod is flown on LC-130 aircraft, which presents the unique opportunity to routinely image the Greenland ice 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 IcePod over the Greenland ice 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 IcePod. At a survey altitude of 1000 m, the laser swath covers ~ 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-based ground survey across the ramp, spot GPS points on the ramp and a nearby GPS base station. Positioning errors can severely impact the accuracy of a laser altimeter when flying over remote regions such as across the ice sheets

  7. Vertical material flux under seasonal sea ice in the Okhotsk Sea north of Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Hiwatari, Takehiko; Shirasawa, Kunio; Fukamachi, Yasushi; Nagata, Ryuichi; Koizumi, Tomoyoshi; Koshikawa, Hiroshi; Kohata, Kunio

    Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m -2 day -1) and organic matter (mainly detritus; 333 mg m -2 day -1) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81-93 mg m -2 day -1) and opal as biosilica (51-67 mg m -2 day -1), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10 6 cells m -2 day -1), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.

  8. Spatial Distribution of Trends and Seasonality in the Hemispheric Sea Ice Covers

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Parkinson, C. L.; Cavalieri, D. J.; Cosmiso, J. C.; Zwally, H. J.

    1998-01-01

    We extend earlier analyses of a 9-year sea ice data set that described the local seasonal and trend variations in each of the hemispheric sea ice covers to the recently merged 18.2-year sea ice 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 ice covers. By combining the separate hemispheric sea ice records into a global one, we have shown that there are statistically significant net decreases in the sea ice coverage on a global scale. The change in the global sea ice extent, is -0.01 +/- 0.003 x 10(exp 6) sq km per decade. The decrease in the areal coverage of the sea ice is only slightly smaller, so that the difference in the two, the open water within the packs, has no statistically significant change.

  9. A comparison of radiation budgets in the Fram Strait marginal ice zone

    NASA Technical Reports Server (NTRS)

    Francis, Jennifer A.; Katsaros, Kristina B.; Ackerman, Thomas P.; Lind, Richard J.; Davidson, Kenneth L.

    1991-01-01

    Results are presented from calculations of radiation budgets for the sea-ice and the open-water regimes in the marginal ice zone (MIZ) of the Fram Strait, from measurements of surface irradiances and meteorological conditions made during the 1984 Marginal Ice Zone Experiment. Simultaneous measurements on either side of the ice edge allowed a comparison of the open-water and the sea-ice environments. The results show significant differences between the radiation budgets of the two regimes in the MIZ. The open water absorbed twice as much radiation as did the ice, and the mean cooling rate of the atmosphere over water was approximately 15 percent larger than that over ice. Calculated fluxes and atmospheric cooling rates were found to compare well with available literature data.

  10. Aerosol data over the last 3000 years in seasonal resolution from the Greenland NEEM ice core

    NASA Astrophysics Data System (ADS)

    Leuenberger, Daiana; Gfeller, Gideon; Schüpbach, Simon; Bigler, Matthias; Fischer, Hubertus

    2013-04-01

    During the field season in summer 2009, the first 600 m (corresponding to 3 kyr b2k (3000 years before A.D. 2000) on the GICC05 timescale) of the Greenland NEEM ice core have been analysed for a variety of aerosol constituents using Continuous Flow Analysis (CFA). Here, the records of electric conductivity, sodium (Na+), calcium (Ca2+), particle numbers of insoluble dust, ammonium (NH4+), nitrate (NO3-) and hydrogen peroxide (H2O2) are presented with an average effective resolution of 1-2 cm, depending on the component. Since the annual layer thickness ? amounts to 15cm at minimum sub-annual signals are resolved in all components over the Holocene period. We achieved to extend the aerosol record over the early Holocene period except for a large gap over the brittle zone from 5-9 kyr b2k. Seasonal variations and extreme events are preserved in great detail and all components. H2O2 is a reliable proxy for the strength of photochemical processes in the lower atmosphere and thus shows its minima and maxima at the summer and winter solstice, respectively. Dust-derived species (insoluble dust, Ca2+) show peak concentrations in early spring and minima in mid-summer. The marine-derived Na+peaks in mid-winter and is lowest during early summer. The mean annual variability in concentrations is about 20 ppbw for both Ca2+andNa+. Moreover, it is of the same order of magnitude in NH4+, butconsiderably larger in NO3- (100 ppbw), both representing continental biogenic sources peaking in spring and showing minima in autumn. The interpretation itsclimatic signal is restricted by NO3- undergoing post-depositional redistribution processes. Not only is the analysis of impurities in sub-annual resolution crucial for the accurate dating of the ice core, but also for establishing a detailed chronology of the occurrence of extreme events such as volcanic eruptions and wildfires. Furthermore, possible changes in the seasonal variability of aerosol concentrations can be investigated. First

  11. Disturbed basal ice seen in radio echo images coincide with zones of big interlocking ice crystals.

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, Dorthe; Gogineni, Sivaprasad; Panton, Christian

    2014-05-01

    Improvement of the depth sounding radio echo sounding (RES) over Antarctica and Greenland Ice Sheet has made it possible to map the near basal layers that have not been 'seen' earlier due to the very high demand of attenuation needed to reach through more than 3000m of ice. The RES internal reflectors show that the near basal ice at many locations has disturbed layering. At the locations where ice cores reach the bedrock both in Greenland and Antarctica studies of the ice crystal size and orientation show that the near basal ice has big and interlocking ice crystals which suggests the ice is not actively deforming. These observations challenge the often used constitutive equations like Glens flow law in ice sheet modelling. A discussion of the impact of the RES findings on ice sheet modeling and the quest to find the oldest ice in Antarctic based on the anisotropy of the basal ice will follow.

  12. Seasonal changes in the spatial distribution of phytoplankton in small, temperate-zone lakes

    USGS Publications Warehouse

    Cloern, J.E.; Alpine, A.E.; Cole, B.E.; Heller, T.

    1992-01-01

    Sampling across two N Minnesota small lakes shows that phytoplankton patchiness is greatly enhanced during winter ice-cover relative to the open-water seasons of exposure to wind stress and rapid turbulent mixing. -Authors

  13. Seasonal and decadal variations of ice-shelf front positions in Dronning Maud Land, East Antarctica

    NASA Astrophysics Data System (ADS)

    Deschamps-Berger, César; Matsuoka, Kenichi; Moholdt, Geir; König, Max

    2015-04-01

    Most of recent rapid changes of the Antarctic ice sheet have been triggered from the ice shelves through enhanced basal melting and/or iceberg calving. The Dronning Maud Land (DML) coastal region is encompassed by many semi-continuous ice shelves, and its mass balance is thus particularly sensitive to changes in the coastal environment. Better knowledge on the region's ice shelves is necessary to predict future behavior of the ice sheet. Here, we present temporal changes of the ice-shelf front positions in DML over the past decade. RADARSAT-2 imagery was used to delineate the front positions at six times between August 2012 and December 2013. Displacements of the ice-shelf edges over this period are mostly in good agreement with displacements derived from satellite interferometery observations. Yet we observe in several sub-regions that displacement during the austral summer is larger than that during the winter. We also observe winter-growth of sea ice from the ice-shelf fronts and outwards to icebergs that are grounded on the continental shelf. Fast sea ice growth and break-up is seasonal and could influence ice-shelf flow close to the fronts. On a longer term, comparison between 2004 and 2009 MOA coast line datasets and our 2012-13 dataset highlights the general stability of the area in the past decade. Between 2004 and 2013, only six ice shelves experienced considerable retreat due to calving of tabular icebergs, leaving the remaining 90 % of the region's ice-shelf fronts advancing in accordance with their local flow.

  14. Duration of the Arctic sea ice melt season: Regional and interannual variability, 1979-2001

    USGS Publications Warehouse

    Belchansky, G.I.; Douglas, D.C.; Platonov, N.G.

    2004-01-01

    Melt onset dates, freeze onset dates, and melt season duration were estimated over Arctic sea ice, 1979-2001, using passive microwave satellite imagery and surface air temperature data. Sea ice melt duration for the entire Northern Hemisphere varied from a 104-day minimum in 1983 and 1996, to a 124-day maximum in 1989. Ranges in melt duration were highest in peripheral seas, numbering 32, 42, 44, and 51 days in the Laptev, Barents-Kara, East Siberian and Chukchi Seas, respectively. In the Arctic Ocean, average melt duration varied from a 75-day minimum in 1987 to a 103-day maximum in 1989. On average, melt onset in annual ice began 10.6 days earlier than perennial ice, and freeze onset in perennial ice commenced 18.4 days earlier than annual ice. Average annual melt dates, freeze dates, and melt durations in annual ice were significantly correlated with seasonal strength of the Arctic Oscillation (AO). Following high-index AO winters (January-March), spring melt tended to be earlier and autumn freeze later, leading to longer melt season durations. The largest increases in melt duration were observed in the eastern Siberian Arctic, coincident with cyclonic low pressure and ice motion anomalies associated with high-index AO phases. Following a positive AO shift in 1989, mean annual melt duration increased 2-3 weeks in the northern East Siberian and Chukchi Seas. Decreasing correlations between consecutive-year maps of melt onset in annual ice during 1979-2001 indicated increasing spatial variability and unpredictability in melt distributions from one year to the next. Despite recent declines in the winter AO index, recent melt distributions did not show evidence of reestablishing spatial patterns similar to those observed during the 1979-88 low-index AO period. Recent freeze distributions have become increasingly similar to those observed during 1979-88, suggesting a recurrent spatial pattern of freeze chronology under low-index AO conditions.

  15. Seasonal sea ice predictions for the Arctic based on assimilation of remotely sensed observations

    NASA Astrophysics Data System (ADS)

    Kauker, F.; Kaminski, T.; Ricker, R.; Toudal-Pedersen, L.; Dybkjaer, G.; Melsheimer, C.; Eastwood, S.; Sumata, H.; Karcher, M.; Gerdes, R.

    2015-10-01

    The recent thinning and shrinking of the Arctic sea ice cover has increased the interest in seasonal sea ice forecasts. Typical tools for such forecasts are numerical models of the coupled ocean sea ice system such as the North Atlantic/Arctic Ocean Sea Ice 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 ice 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 ice thickness product in conjunction with the University of Bremen's snow depth product and the OSI SAF ice concentration and sea surface temperature products. We investigate the skill of predictions of the summer ice 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 ice thickness product that uses a spatially varying scaling factor.

  16. Modeling seasonality of ice and ocean carbon production in the Arctic

    NASA Astrophysics Data System (ADS)

    Jin, M.; Deal, C. M.; Ji, R.

    2011-12-01

    In the Arctic Ocean, both phytoplankton and sea ice algae are important contributors to the primary production and the arctic food web. Copepod in the arctic regions have developed their feeding habit depending on the timing between the ice algal bloom and the subsequent phytoplankton bloom. A mismatch of the timing due to climate changes could have dramatic consequences on the food web as shown by some regional observations. In this study, a global coupled ice-ocean-ecosystem model was used to assess the seasonality of the ice algal and phytoplankton blooms in the arctic. The ice-ocean ecosystem modules are fully coupled in the physical model POP-CICE (Parallel Ocean Program- Los Alamos Sea Ice Model). The model results are compared with various observations. The modeled ice and ocean carbon production were analyzed by regions and their linkage to the physical environment changes (such as changes of ice concentration and water temperature, and light intensity etc.) between low- and high-ice years.

  17. An Evaluation of the Seasonal Arctic Sea Ice Predictions from CFSv2

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Wang, M.; Overland, J. E.

    2015-12-01

    The rapid reductions in Arctic sea ice have been observed in the past several decades, especially at the end of the summer melt season in September. It is necessary to have a reliable seasonal forecast of Arctic sea ice. In this study, we examined the Arctic sea ice predictions produced by NCEP Climate Forecast System version 2 (CFSv2) in the real- time operational mode. Forecasts were initialized monthly for two-year period (March 2014 to September 2015). Forecasts of sea ice extent (SIE) and concentration (SIC) were evaluated against the sea ice analysis (HadISST_ice) from the Hadley Center. We found that the Arctic September SIE forecasts from CFS were overestimated with the biases in SIC mainly originated from the Beaufort Sea, Laptev Sea and Fram Strait. For 2014, we found that the forecast initialized from March with the lead-time of 6 months gave the best September SIE forecast while the forecast initialized from July with the lead-time of 2 months had the worst September SIE forecast. In order to understand the forecast biases in September sea ice, the atmospheric forecasted forcings including incoming solar/Infrared radiation, upward solar/infrared radiation from surface, latent and sensible heat flux, 2-meter air temperature, cloud fraction, sea level pressure and 10-meter wind from CFSv2 were evaluated using the European Center for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim) .

  18. Variations of mesoscale and large-scale sea ice morphology in the 1984 Marginal Ice Zone Experiment as observed by microwave remote sensing

    NASA Technical Reports Server (NTRS)

    Campbell, W. J.; Josberger, E. G.; Gloersen, P.; Johannessen, O. M.; Guest, P. S.

    1987-01-01

    The data acquired during the summer 1984 Marginal Ice Zone Experiment in the Fram Strait-Greenland Sea marginal ice zone, using airborne active and passive microwave sensors and the Nimbus 7 SMMR, were analyzed to compile a sequential description of the mesoscale and large-scale ice morphology variations during the period of June 6 - July 16, 1984. Throughout the experiment, the long ice edge between northwest Svalbard and central Greenland meandered; eddies were repeatedly formed, moved, and disappeared but the ice edge remained within a 100-km-wide zone. The ice pack behind this alternately diffuse and compact edge underwent rapid and pronounced variations in ice concentration over a 200-km-wide zone. The high-resolution ice concentration distributions obtained in the aircraft images agree well with the low-resolution distributions of SMMR images.

  19. Investigating the marginal ice zone on the Newfoundland Shelf

    NASA Astrophysics Data System (ADS)

    Smith, Peter C.; Tang, C. L.; MacPherson, J. Ian; McKenna, Richard F.

    From the ice and current data collected over the Newfoundland Shelf by the second Canadian Atlantic Storms Program (CASP II), it is evident that ice motion is affected by wind-generated ocean current. This points to the importance of coupled ice-ocean response to wind forcing in the study of shortterm ice motion and operational ice forecasting. The mutual influence of ice and the ocean can also be seen in the water properties.To study the mature stages of explosive cyclogenesis in east coast winter storms and to investigate their influence on the circulation and sea ice properties on the Newfoundland continental shelf and Grand Banks, CASP II was conducted by scientists from the Bedford Institute of Oceanography (BIO), the Atmospheric Environment Service (AES), the National Research Council (NRC), and many universities, private companies, and other government agencies.

  20. Peculiarities of the Bound Water and Water Ice Seasonal Variations in the Martian Surface Layer of the Regolith.

    NASA Astrophysics Data System (ADS)

    Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. H.; Mitrofanov, I. G.; Litvak, M. L.

    2008-09-01

    Introduction: The processes of the hydration/ dehydration of salt minerals within the Martian soil and the condensation/sublimation of water ice (and frost) in the surficial soil layer and on the polar cap surface play great significance in the modern water cycle on Mars and directly affect the redistribution of the water phases and forms in the system "atmosphere/regolith/polar caps" [1, 2, 3, 4, 5]. The processes are reversible in time and their intensity is strongly dependent on such time-variable climatic parameters as atmospheric and surface temperature, atmospheric water vapour content and specific features of atmospheric seasonal circulation [6, 7, 8, 9, 10]. In the work we report the study results of the seasonal variations of the chemically bound water (BW) spectral signature (based on the TES and OMEGA data), estimation and mapping of the winterand spring-time water ice increase within the Martian surface soil (based on the TES and HEND data). Analysis and results: Regional and global mapping of the BW spectral index distribution as function of the seasons was conducted by using of the 6.1 μm emission pick from the TES dataset and the 1.91 μm absorption band from reflectance spectra of the OMEGA data. The study of the seasonal redistribution of the water ice (and frost) within the thin surficial soil layer was conducted based on the TES thermal inertia (TI) data and the HEND neutrons flux mapping data. Bound water mapping: The mapping of the TES 6.1 μm BW index distributions was conducted at the time steps from 30° to 60° of Ls [11]. The mapping results show remarkable changes of the BW index values from one season to other one at notable latitudinal dependence of the index (Fig.1). At that, the higher BW index values are disposed mostly within the peripheral zone near the edge of the perennial and seasonal polar caps (cooler, wetter areas), while the lower BW index values are observed at low latitudes (warmer, drier areas). Between the Nspring (Ls=0

  1. Peculiarities of the Bound Water and Water Ice Seasonal Variations in the Martian Surface Layer of the Regolith.

    NASA Astrophysics Data System (ADS)

    Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. H.; Mitrofanov, I. G.; Litvak, M. L.

    2008-09-01

    Introduction: The processes of the hydration/ dehydration of salt minerals within the Martian soil and the condensation/sublimation of water ice (and frost) in the surficial soil layer and on the polar cap surface play great significance in the modern water cycle on Mars and directly affect the redistribution of the water phases and forms in the system "atmosphere/regolith/polar caps" [1, 2, 3, 4, 5]. The processes are reversible in time and their intensity is strongly dependent on such time-variable climatic parameters as atmospheric and surface temperature, atmospheric water vapour content and specific features of atmospheric seasonal circulation [6, 7, 8, 9, 10]. In the work we report the study results of the seasonal variations of the chemically bound water (BW) spectral signature (based on the TES and OMEGA data), estimation and mapping of the winterand spring-time water ice increase within the Martian surface soil (based on the TES and HEND data). Analysis and results: Regional and global mapping of the BW spectral index distribution as function of the seasons was conducted by using of the 6.1 μm emission pick from the TES dataset and the 1.91 μm absorption band from reflectance spectra of the OMEGA data. The study of the seasonal redistribution of the water ice (and frost) within the thin surficial soil layer was conducted based on the TES thermal inertia (TI) data and the HEND neutrons flux mapping data. Bound water mapping: The mapping of the TES 6.1 μm BW index distributions was conducted at the time steps from 30° to 60° of Ls [11]. The mapping results show remarkable changes of the BW index values from one season to other one at notable latitudinal dependence of the index (Fig.1). At that, the higher BW index values are disposed mostly within the peripheral zone near the edge of the perennial and seasonal polar caps (cooler, wetter areas), while the lower BW index values are observed at low latitudes (warmer, drier areas). Between the Nspring (Ls=0

  2. Seasonal changes in ice sheet motion due to melt water lubrication

    NASA Astrophysics Data System (ADS)

    Hewitt, I.

    2012-12-01

    Significant temporal variability of ice flow has been observed at the melting margins of the Greenland ice sheet. Seasonal acceleration and deceleration has been partly attributed to changes in resistance at the ice-bed interface caused by subglacial routing of surface melt water, as is the case for valley glaciers. Larger quantities of melt water do not necessarily reduce resistance, however, and the overall effect of melt water lubrication on the mean annual motion of the ice sheet remains unclear. In this work, numerical models are used to explore the coupling between subglacial drainage of surface melt water and ice sheet motion. A synthetic ice sheet is forced to melt according to a prescribed seasonal cycle and the effect of this melting on the speed of the ice is calculated. The model adopts a distributed-channelized structure for the subglacial drainage system, with opening and closing of drainage space controlled by turbulent dissipation, cavitation around bedrock roughness elements, and creep closure of the ice. Subglacial water pressure is assumed to exert the main hydrological control on ice lubrication and is used to parameterize the basal sliding law for a vertically-integrated higher-order ice flow model. The model results suggest that the fastest ice velocities should be expected soon after the onset of surface melting, when runoff into moulins swamps the existing capacity of the drainage system. Periods of relatively high melting at any stage of the melt season can have the same effect, but the establishment of a more efficient drainage system can also have the effect of reducing water pressure and sliding velocities. This behaviour is in broad agreement with current observations. Comparing years with different total melting rates, the model further suggests that slow-down due to the more efficient drainage system is likely to be confined to close to the ice sheet margins (perhaps within about 20km), whereas further away from the margin a larger

  3. Summer-Fall Seasonal Ices at the Mars Phoenix Landing Site: Results from CRISM Observations

    NASA Astrophysics Data System (ADS)

    Cull, S.; Arvidson, R. E.; Morris, R. V.; Wolff, M. J.; Mellon, M. T.; Lemmon, M. T.

    2009-12-01

    We combine ground observations from the Mars Phoenix lander with orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to chart the onset of seasonal ice at the landing site from late spring (solar longitude [Ls] ~ 84) to late summer (Ls] ~ 117) . We use 25 CRISM observations acquired directly over the landing site and 13 acquired near the landing site. We find that summer ice-free spectra at the Phoenix landing site are approximated by scattering properties similar to Gusev Crater soils. Summer spectra have the strong water absorption at 3 μm, indicating a low level of hydration or adsorption of water, an effect previously observed throughout the northern hemisphere. Patches of permanent water ice appear on the shadowed sides of Heimdal Crater and on the shadowed sides of large mountains to the northeast. These patches were monitored throughout the summer and did not appear to grow or shrink; however, the ice patches darken between Ls~119 and Ls~160, possibly due to the sublimation or sintering of fine-grained ices cold-trapped onto the ice deposits during the spring defrost period. Mobile patches of summertime ice were observed to follow the shadow of a crater wall on an ~85-m crater located ~6.5 km northeast of the landing site. Widespread surface ice was first observed at the Phoenix landing site during the night (3 a.m. Local True Solar Time [LTST]) at Ls~104, and water ice was first observed in the afternoon (3 p.m. LTST) at Ls~154. CRISM observations show the first afternoon water ice clouds at Ls~157. Phoenix Surface Stereo Imager (SSI) images first show evidence of afternoon (1 p.m. LTST) water ice in the shadows of large rocks on operations sol 80 (Ls~112), but did not observe widespread afternoon ice during the mission, which ended at Ls~149.

  4. Observational uncertainty of Arctic sea-ice concentration significantly affects seasonal climate forecasts

    NASA Astrophysics Data System (ADS)

    Bunzel, Felix; Notz, Dirk; Baehr, Johanna; Müller, Wolfgang; Fröhlich, Kristina

    2016-04-01

    We examine how the choice of a particular satellite-retrieved sea-ice concentration dataset used for initialising seasonal climate forecasts impacts the prediction skill of Arctic sea-ice area and Northern hemispheric 2-meter air temperatures. To do so, we performed two assimilation runs with the Max Planck Institute Earth System Model (MPI-ESM) from 1979 to 2012, where atmospheric and oceanic parameters as well as sea-ice concentration were assimilated using Newtonian relaxation. The two assimilation runs differ only in the sea-ice concentration dataset used for assimilating sea ice. In the first run, we use sea-ice concentrations as derived by the NASA-Team algorithm, while in the second run we use sea-ice concentrations as derived from the Bootstrap algorithm. A major difference between these two sea-ice concentration data products involves the treatment of melt ponds. While for both products melt ponds appear as open water in the raw satellite data, the Bootstrap algorithm more strongly attempts to offset this systematic bias by synthetically increasing the retrieved ice concentration during summer months. For each year of the two assimilation runs we performed a 10-member ensemble of hindcast experiments starting on 1 May and 1 November with a hindcast length of 6 months. For hindcasts started in November, initial differences in Arctic sea-ice area and surface temperature decrease rapidly throughout the freezing period. For hindcasts started in May, initial sea-ice area differences increase over time. By the end of the melting period, this causes significant differences in 2-meter air temperature of regionally more than 3°C. Hindcast skill for surface temperatures over Europe and North America is higher with Bootstrap initialization during summer and with NASA Team initialisation during winter. This implies that the choice of the sea-ice data product and, thus, the observational uncertainty also affects forecasts of teleconnections that depend on Northern

  5. Seasonal comparisons of sea ice concentration estimates derived from SSM/I, OKEAN and RADARSAT data

    USGS Publications Warehouse

    Belchansky, G.I.; Douglas, D.C.

    2002-01-01

    The SSM/I microwave satellite radiometer and its predecessor SMMR are primary sources of information for global sea-ice and climate studies. However, comparisons of SSM/I, LANDSAT, AVHRR and ERS-1 SAR have shown substantial seasonal and regional differences in their estimates of sea ice concentration. To evaluate these differences, we compared SSM/I estimates of sea ice coverage derived with the NASA Team and Bootstrap algorithms to estimates made using RADARSAT, and OKEAN-01 satellite sensor data. The study area included the Barents, Kara Sea, Laptev Sea, and adjacent parts of the Arctic Ocean, during October 1995 through October 1999. Ice concentration estimates from spatially and temporally near-coincident imagery were calculated using independent algorithms for each sensor type. The OKEAN algorithm implemented the satellite's two-channel active (radar) and passive microwave data in a linear mixture model based on the measured values of brightness temperature and radar backscatter. The RADARSAT algorithm utilized a segmentation approach of the measured radar backscatter, and the SSM/I ice concentrations were derived at National Snow and Ice Data Center (NSIDC) using the NASA Team and Bootstrap algorithms. Seasonal and monthly differences between SSM/I, OKEAN, and RADARSAT ice concentrations were calculated and compared. Overall, total sea ice concentration estimates derived independently from near-coincident RADARSAT, OKEAN-01 and SSM/I satellite imagery demonstrated mean differences of less than 5.5 % (SD < 9.5%) during the winter period. Differences between the SSM/I NASA Team and the SSM/I Bootstrap concentrations were no more than 3.1 % (SD < 5.4%) during this period. RADARSAT and OKEAN-01 data both yielded higher total ice concentrations than the NASA Team and the Bootstrap algorithms. The Bootstrap algorithm yielded higher total ice concentrations than the NASA Team algorithm. Total ice concentrations derived from OKEAN-01 and SSM/I satellite imagery were

  6. Satellite and aircraft passive microwave observations during the Marginal Ice Zone Experiment in 1984

    NASA Technical Reports Server (NTRS)

    Gloersen, Per; Campbell, William J.

    1988-01-01

    This paper compares satellite data on the marginal ice zone obtained during the Marginal Ice Zone Experiment in 1984 by Nimbus 7 with simultaneous mesoscale aircraft (in particular, the NASA CV-990 airborne laboratory) and surface observations. Total and multiyear sea ice concentrations calculated from the airborne multichannel microwave radiometer were found to agree well with similar calculations using the Nimbus SMMR data. The temperature dependence of the determination of multiyear sea-ice concentration near the melting point was found to be the same for both airborne and satellite data. It was found that low total ice concentrations and open-water storm effects near the ice edge could be reliably distinguished by means of spectral gradient ratio, using data from the 0.33-cm and the 1.55-cm radiometers.

  7. Skill improvement of seasonal Arctic sea ice forecasts using bias-correction and ensemble calibration

    NASA Astrophysics Data System (ADS)

    Krikken, Folmer; Hazeleger, Wilco; Vlot, Willem; Schmeits, Maurice; Guemas, Virginie

    2016-04-01

    We explore the standard error and skill of dynamical seasonal sea ice forecasts of the Arctic using different bias-correction and ensemble calibration methods. The latter is often used in weather forecasting, but so far has not been applied to Arctic sea ice forecasts. We use seasonal predictions of Arctic sea ice of a 5-member ensemble forecast using the fully coupled GCM EC-Earth, with model initial states obtained by nudging towards ORAS4 and ERA-Interim. The raw model forecasts contain large biases in total sea ice area, especially during the summer months. This is mainly caused by a difference in average seasonal cycle between EC-Earth and observations, which translates directly into the forecasts yielding large biases. Further errors are introduced by the differences in long term trend between the observed sea ice, and the uninitialised EC-earth simulation. We find that extended logistic regression (ELR) and heteroscedastic extended logistic regression (HELR) both prove viable ensemble calibration methods, and improve the forecasts substantially compared to standard bias correction techniques. No clear distinction between ELR and HELR is found. Forecasts starting in May have higher skill (CRPSS > 0 up to 5 months lead time) than forecasts starting in August (2-3 months) and November (2-3 months), with trend-corrected climatology as reference. Analysis of regional skill in the Arctic shows distinct differences, where mainly the Arctic ocean and the Kara and Barents sea prove to be one of the more predictable regions with skilful forecasts starting in May up to 5-6 months lead time. Again, forecasts starting in August and November show much lower regional skill. Overall, it is still difficult to beat relative simple statistical forecasts, but by using ELR and HELR we are getting reasonably close to skilful seasonal forecasts up to 12 months lead time. These results show there is large potential, and need, for using ensemble calibration in seasonal forecasts of

  8. Local Effects of Ice Floes on Skin Sea Surface Temperature in the Marginal Ice Zone from UAVs

    NASA Astrophysics Data System (ADS)

    Zappa, C. J.; Brown, S.; Emery, W. J.; Adler, J.; Wick, G. A.; Steele, M.; Palo, S. E.; Walker, G.; Maslanik, J. A.

    2013-12-01

    Recent years have seen extreme changes in the Arctic. Particularly striking are changes within the Pacific sector of the Arctic Ocean, and especially in the seas north of the Alaskan coast. These areas have experienced record warming, reduced sea ice extent, and loss of ice in areas that had been ice-covered throughout human memory. Even the oldest and thickest ice types have failed to survive through the summer melt period in areas such as the Beaufort Sea and Canada Basin, and fundamental changes in ocean conditions such as earlier phytoplankton blooms may be underway. Marginal ice zones (MIZ), or areas where the "ice-albedo feedback" driven by solar warming is highest and ice melt is extensive, may provide insights into the extent of these changes. Airborne remote sensing, in particular InfraRed (IR), offers a unique opportunity to observe physical processes at sea-ice margins. It permits monitoring the ice extent and coverage, as well as the ice and ocean temperature variability. It can also be used for derivation of surface flow field allowing investigation of turbulence and mixing at the ice-ocean interface. Here, we present measurements of visible and IR imagery of melting ice floes in the marginal ice zone north of Oliktok Point AK in the Beaufort Sea made during the Marginal Ice Zone Ocean and Ice Observations and Processes EXperiment (MIZOPEX) in July-August 2013. The visible and IR imagery were taken from the unmanned airborne vehicle (UAV) ScanEagle. The visible imagery clearly defines the scale of the ice floes. The IR imagery show distinct cooling of the skin sea surface temperature (SST) as well as a intricate circulation and mixing pattern that depends on the surface current, wind speed, and near-surface vertical temperature/salinity structure. Individual ice floes develop turbulent wakes as they drift and cause transient mixing of an influx of colder surface (fresh) melt water. The upstream side of the ice floe shows the coldest skin SST, and

  9. 36 CFR 13.912 - Kantishna area summer season firearm safety zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... firearm safety zone. 13.912 Section 13.912 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve General Provisions § 13.912 Kantishna area summer season firearm safety zone. What is prohibited? No one may fire a gun during the summer season in or across the Kantishna area firearm safety...

  10. 36 CFR 13.912 - Kantishna area summer season firearm safety zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... firearm safety zone. 13.912 Section 13.912 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve General Provisions § 13.912 Kantishna area summer season firearm safety zone. What is prohibited? No one may fire a gun during the summer season in or across the Kantishna area firearm safety...

  11. 36 CFR 13.912 - Kantishna area summer season firearm safety zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... firearm safety zone. 13.912 Section 13.912 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve General Provisions § 13.912 Kantishna area summer season firearm safety zone. What is prohibited? No one may fire a gun during the summer season in or across the Kantishna area firearm safety...

  12. 36 CFR 13.912 - Kantishna area summer season firearm safety zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... firearm safety zone. 13.912 Section 13.912 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve General Provisions § 13.912 Kantishna area summer season firearm safety zone. What is prohibited? No one may fire a gun during the summer season in or across the Kantishna area firearm safety...

  13. 36 CFR 13.912 - Kantishna area summer season firearm safety zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... firearm safety zone. 13.912 Section 13.912 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve General Provisions § 13.912 Kantishna area summer season firearm safety zone. What is prohibited? No one may fire a gun during the summer season in or across the Kantishna area firearm safety...

  14. Linking IceBridge, ICESat, and CryoSat-2 for improved seasonal to decadal-scale estimates of sea ice thickness and volume (Invited)

    NASA Astrophysics Data System (ADS)

    Kurtz, N. T.; Galin, N.; Studinger, M.; Farrell, S. L.; Harbeck, J. P.; Markus, T.; Onana, V.; Richter-Menge, J.; Yi, D.

    2013-12-01

    Recent work by Laxon et al., [2013] has connected the observational records of Arctic sea ice thickness from ICESat and CryoSat-2, and airborne measurements collected by IceBridge and ESA's CryoVEx campaign. The wealth of observations and public availability of data products from the IceBridge airborne campaign provide a continuing source for evaluation and improvement of the observational sea ice thickness record. Additionally, the fast availability of the IceBridge quick look data products are now providing a unique new data set for improving seasonal forecasts of Arctic sea ice. We present a best estimate of the ten year (2003-2013) sea ice thickness time series and associated uncertainty from the laser altimetry records of ICESat and IceBridge. We also connect the IceBridge observations to CryoSat-2 results. We show that improved freeboard and thickness results can be obtained over currently used threshold tracker methods through the usage of a new surface tracker which adapts to varying surface roughness and the associated backscattering variations found over different sea ice surfaces. Lastly, we will present an evaluation of the archival and quick look IceBridge sea ice products to determine areas of needed improvement and constrain errors in the usage of the quick look data for seasonal sea ice forecasts.

  15. Can Ice-Nucleating Aerosols Affect Arctic Seasonal Climate?

    SciTech Connect

    Prenni, Anthony J.; Harrington, Jerry Y.; Tjernstrom, Michael; DeMott, Paul J.; Avramov, Alexander; Long, Charles N.; Kreidenweis, Sonia M.; Olsson, Peter Q.; Verlinde, J.

    2007-04-01

    To date, climate and regional models have generally proven unsuccessful at simulating Arctic cloudiness, particularly during the colder months. Models tend to underpredict the amount of liquid water in mixed-phase clouds, which are ubiquitous in this region. This is problematic because cloud coverage and phase can greatly impact the Arctic radiative budget. Using recent measurements of ice nucleating aerosol, we show that incorrect, or nonexistent, parameterizations of aerosol-cloud interactions are at least partially responsible for the poor model predictions. Moreover, we show that this can lead to errors in the modeled surface radiative energy budget of 10-100 W m-2.

  16. Rapid growth and seasonal persistence of efficient subglacial drainage under kilometre thick Greenland ice

    NASA Astrophysics Data System (ADS)

    Nienow, P.; Wadham, J.; Chandler, D.; Doyle, S. H.; Tedstone, A. J.; Hubbard, A., II

    2015-12-01

    The relationship between surface melt and ice motion partly determines the sensitivity of the Greenland Ice Sheet to climate, and the structure of the subglacial drainage system may be critical in controlling how changing melt-rates will impact on future ice dynamics. However, the extent to which efficient subglacial drainage develops tens of km inland from the ice margin under thick (>1km) ice remains equivocal. In particular, several numerical modelling studies suggest that under such conditions subglacial channels cannot evolve on seasonal timescales, even under extreme inputs of surface meltwater. Here, we present hydrological and ice-motion data collected in summer 2012 in the vicinity of a moulin located ~40 km from the western margin of the Greenland Ice Sheet, where ice is ~1km thick. Supraglacial discharge into the moulin was monitored from the onset of surface drainage and the tracer sulphur hexafluoride (SF6) was injected into the moulin at repeat intervals and its emergence was monitored at its proglacial river outlet. The tracer results indicate rapid evolution from a slow, inefficient drainage system to a fast, hydraulically efficient system within ~three weeks from the onset of surface drainage. Once an efficient hydrological pathway was established, it remained open - as evidenced by the fast tracer return times - even during periods of low surface melt (~0.01m/d), when discharge into the moulin was <4 m3 s-1 and ceased overnight. Ice motion in the vicinity of the moulin slowed following the establishment of the efficient drainage pathway with a clear diurnal cyclicity driven by variations in supraglacial discharge. Our results confirm that hydraulically-efficient subglacial drainage can exist 10s km from the ice sheet margin where ice is ~1km thick, that the drainage configuration can form in a matter of weeks, and that it persists even during cool periods when local surface melt rates and inputs are low.

  17. Estimation and mapping of wintertime increase in water ice content of the Martian surface soil based on seasonal Thermal Emission Spectrometer thermal inertia variations

    NASA Astrophysics Data System (ADS)

    Kuzmin, R. O.; Zabalueva, E. V.; Christensen, P. R.

    2009-04-01

    Results of the Mars Global Surveyor Thermal Emission Spectrometer (TES) thermal inertia seasonal variations analysis show significant increase of the thermal inertia during autumn-winter periods in the middle latitudes. This observed increase occurred with regular repetition during each of the three Mars years of the TES observations. Two climatic factors (atmospheric dust loading and water ice (frost) formation in the soil) might lead to the real and/or apparent seasonal increase in thermal inertia. We compare maps of summertime and wintertime thermal inertia at similarly low atmospheric dust opacity within the latitude belt ±50°, outside of the seasonal CO2 ice cover. On the basis of the results of such comparison we developed a new method for estimating and mapping the wintertime increase of the water ice within the surface soil layer corresponding to the daily thermal skin depth of 2-10 cm. We use both the nomograms of relation between the thermal inertia for dry and icy soil compiled for different water ice content and an analytical approach. Comparison of the mapped wintertime TES thermal inertia values with computed values of the parameter for icy soil at different ice amounts shows that the wintertime thermal inertia values in the latitude ranges 40°-50°N and 40°-50°S are consistent with the presence of the water ice amount in the soil from 4 up to 17 vol % (locally), whereas at lower latitudes the ice amount is mainly less than 1 vol %. Mapping results show that the zone with a soil water ice amount of >3 vol % is much more in the northern hemisphere than in the southern one.

  18. Impact of the assimilated sea ice data product on seasonal climate predictions with MPI-ESM

    NASA Astrophysics Data System (ADS)

    Bunzel, Felix; Notz, Dirk; Baehr, Johanna; Müller, Wolfgang; Fröhlich, Kristina

    2015-04-01

    We examine the impact of choosing a particular satellite record of sea ice for the initialisation of a seasonal prediction system. Such systems have in the past usually only been initialised with data describing the state of the ocean and of the atmosphere. However, also sea ice yields a substantial source of predictability, as it plays an important role for the Earth's energy and water budget. Therefore, recent studies started to incorporate sea ice into the initialisation of seasonal forecasts. For our study, we performed two assimilation runs with MPI-ESM from 1979 to 2012, where atmospheric and oceanic parameters as well as sea ice concentration were assimilated using Newtonian relaxation. The two assimilation runs differ only in the sea ice concentration dataset used for assimilating sea ice. In the first run, sea ice concentrations as derived by the NASA-Team algorithm are used, while in the second run sea ice concentrations computed from the Bootstrap algorithm are assimilated. A major difference between the two sea ice concentration data products involves the treatment of melt ponds. While for both products melt ponds appear as open water in the raw satellite data, the Bootstrap algorithm more strongly attempts to offset this systematic bias by synthetically increasing the retrieved ice concentration during summer months. For each year of the two assimilation runs we performed a 10-member ensemble of hindcast experiments starting on 1 May. We find the anomaly correlation coefficient for Arctic sea ice area at 2-3 months lead time to be substantially larger for Bootstrap initialisation compared to NASA-Team initialisation. The root mean square error reveals that in the central Arctic the Bootstrap initialisation produces better predictions, whereas the NASA-Team initialisation outperforms the Bootstrap initialisation in the vicinity of the ice edge. We investigate causes and mechanisms behind the dependence of the obtained prediction skill on the sea ice

  19. Seasonal variability of heterogeneous ice formation in stratiform clouds over the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Seifert, Patric; Kunz, Clara; Baars, Holger; Ansmann, Albert; Bühl, Johannes; Senf, Fabian; Engelmann, Ronny; Althausen, Dietrich; Artaxo, Paulo

    2015-07-01

    Based on 11 months of polarization lidar observations in the Amazon Basin near Manaus, Brazil (2.3°S, 60°W), the relationship between temperature and heterogeneous ice formation efficiency in stratiform clouds was evaluated in the cloud top temperature range between -40 and 0°C. Between -30 and 0°C, ice-containing clouds are a factor of 1.5 to 2 more frequent during the dry season. Free-tropospheric aerosol backscatter profiles revealed a twofold to tenfold increase in aerosol load during the dry season and a Monitoring Atmospheric Composition and Climate—Interim Implementation reanalysis data set implies that the aerosol composition during the dry season is strongly influenced by biomass burning aerosol, whereas other components such as mineral dust do not vary strongly between the seasons. The injection of smoke accompanied by the likely dispersion of biological material, soil dust, or ash particles was identified as a possible source for the increased ice formation efficiency during the dry season.

  20. Seasonal climate forecasts significantly affected by observational uncertainty of Arctic sea ice concentration

    NASA Astrophysics Data System (ADS)

    Bunzel, Felix; Notz, Dirk; Baehr, Johanna; Müller, Wolfgang A.; Fröhlich, Kristina

    2016-01-01

    We investigate how observational uncertainty in satellite-retrieved sea ice concentrations affects seasonal climate predictions. To do so, we initialize hindcast simulations with the Max Planck Institute Earth System Model every 1 May and 1 November from 1981 to 2011 with two different sea ice concentration data sets, one based on the NASA Team and one on the Bootstrap algorithm. For hindcasts started in November, initial differences in Arctic sea ice area and surface temperature decrease rapidly throughout the freezing period. For hindcasts started in May, initial differences in sea ice area increase over time. By the end of the melting period, this causes significant differences in 2 meter air temperature of regionally more than 3°C. Hindcast skill for surface temperatures over Europe and North America is higher with Bootstrap initialization during summer and with NASA Team initialization during winter. This implies that the observational uncertainty also affects forecasts of teleconnections that depend on northern hemispheric climate indices.

  1. Tracking Retreat of the North Seasonal Ice Cap on Mars: Results from the THEMIS Investigation

    NASA Technical Reports Server (NTRS)

    Ivanov, A. B.; Wagstaff, K. L.; Ttus, T. N.

    2005-01-01

    The CO2 ice caps on Mars advance and retreat with the seasons. This phenomenon was first observed by Cassini and then confirmed by numerous ground based observations in 19th and 20th centuries. With the advent of the space age observations of the seasonal ice cap were done by all orbiting spacecraft starting with Mariner 7. Viking Orbiters and more recently the Mars Global Surveyor (particularly Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES) instruments) have accumulated significant data on the retreat of the CO2 seasonal cap. During Mars year 2 of THEMIS operations at Mars, we planned an observational campaign in which the THEMIS instrument (onboard the Mars Odyssey spacecraft) repeatedly observed the north seasonal polar cap from midwinter to late spring. THEMIS allows simultaneous observations in both Thermal IR (12.57 m) and Visible wavelengths (0.65 m). One of the goals for this work is to initiate an interannual program for observations of the seasonal ice caps using the THEMIS instrument. The most efficient way to detect the edge between frost and bare ground is directly onboard of the spacecraft. Prior to onboard software design effort, we have developed two groundbased algorithms for automatically finding the edge of the seasonal polar cap in THEMIS IR data. The first algorithm relies on fully calibrated data and can be used for highly reliable groundbased analyses. The second method was specifically developed for processing raw, uncalibrated data in a highly efficient way. It has the potential to enable automatic, onboard detections of the seasonal cap retreat. We have experimentally confirmed that both methods produce similar results, and we have validated both methods against a model constructed from the MGS TES data from the same season.

  2. Nutrients Seasonal Variability and Carbonate System Dynamics in the Laptev Sea coastal zone

    NASA Astrophysics Data System (ADS)

    Savelieva, Nina; Pipko, Irina; Semiletov, Igor

    2010-05-01

    The Arctic ocean has the broadest shelf in the World ocean: the continental shelves occupy about 36% of the Arctic oceanic area. Morever, greater than 90% of all organic carbon burial occurs in sediments depositing on deltas, continental shelves , and upper continental slopes, and the significant portion of organic carbon withdraw is occurred over the Siberian shelf (Macdonald et al., 2008). The coastal zone plays an important role in the East Siberian Arctic land-shelf-basin system, because the major transport of fresh water, dissolved and solid material into the Arctic Ocean is determined by 1) the riverine discharges, and 2) coastal erosion. Production in the Arctic is highly seasonal, and it is important to consider the magnitude of seasonal variations in nutrients. Here we present the results (nutrients, parameters of the carbonate system, and oxygen) obtained during ice-covered season (April of 2002 and 2007) and open water season (September of 2000 and 2005) over the south-eastern part of the Laptev Sea which is under strong influence of the Lena river and coastal erosion. High spatial-temporal variability in nutrients (ammonium, nitrates, nitrites, phosphate, and silicates) and carbonate parameters (pH, Talk, and pCO2) distributions has been found. We suggest that relatively high (vs entire oligotrophic Laptev and East Siberian seas) productivity of the coastal zone is related not only to the influence of the river inputs, but also the coastal erosion, enriching the coastal waters in nutrients and terrestrial organic matter and to the close coupling between the water and sediment, assuring a rapid reutilization of regenerated elements. Highest anomalies of all parameters (for instance: pCO2 up to 4000mkatm) are associated with the areas strongly affected by coastal erosion. References Macdonald R.W., Anderson L.G., Christensen J.P., Miller L.A., Semiletov I.P., and R. Stein, 2008. The Arctic Ocean: budgets and fluxes, In "Carbon and Nutrient Fluxes in

  3. On Impacts of Ocean Waves in Marginal Ice Zones and their Repercussions for Arctic Ice/Ocean Models (Invited)

    NASA Astrophysics Data System (ADS)

    Squire, V. A.

    2013-12-01

    , each with possibly different concentrations and randomized floes present in some FSD, the manner in which a long crested sea with its intrinsic directional spread advances through a conglomeration of dispersed multiply-scattering floes can be tracked, with the purpose of finding how the waves diminish in amplitude and whether the sea ice will be broken up. The details of how this is done are the subject of another AGU paper. My presentation will focus primarily on the ';why and how' of implanting wave-ice interactions in ice/ocean models and on recent developments to ensure that the physics used is as robust as practicable. Francis, O. P., G. G. Panteleev, and D. E. Atkinson (2011), Ocean wave conditions in the Chukchi Sea from satellite and in situ observations, Geophys. Res. Lett., 38, L24610, doi: 10.1029/ 2011GL049839. Williams, T. D., L. G. Bennetts, V. A. Squire, D. Dumont, and L. Bertino (2013a), Wave-ice interactions in the marginal ice zone. Part 1: Theoretical foundations, Ocean Model., doi: 10.1016/j.ocemod. 2013.05.010. ------ (2013b), Wave-ice interactions in the marginal ice zone. Part 2: Numerical implementation and sensitivity studies along 1D transects of the ocean surface, Ocean Model., doi: 10.1016/j.ocemod. 2013.05.011.

  4. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    DOE PAGESBeta

    Greene, S.; Walter Anthony, K. M.; Archer, D.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.

    2014-07-15

    Microbial methane (CH4) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominatesmore » annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.« less

  5. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    DOE PAGESBeta

    Greene, S.; Walter Anthony, K. M.; Archer, D.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.

    2014-12-08

    Microbial methane (CH4) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominatesmore » annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.« less

  6. Mapping of ice layer extent and snow accumulation in the percolation zone of the Greenland ice sheet

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Steffen, K.; Neumann, G.; Huff, R.

    2005-01-01

    The Greenland ice sheet underwent record extensive melt in 2002 and prolonged melt in 2003. The severe melting created a significant and extensive ice layer over the Greenland ice sheet. An innovative approach is developed to detect the ice layer formation using data acquired by the SeaWinds scatterometer on the QuikSCAT satellite. QuikSCAT backscatter together with in situ data from automatic weather stations of the Greenland Climate Network are used to map the extent of ice layer formation. The results reveal areas of extensive ice layer formed by the 2002 melt, which is consistent with the maximum melt extent in 2002. Moreover, during freezing seasons, QuikSCAT data show a linear decrease in backscatter (in decibels or dB) that is related to the amount of snow accumulation in the ice layer formation region. This snow accumulation signature is caused by the attenuation of radar waves in the snow layer, accumulating since the last major melt event, whose thickness appears as an exponential function in relation to the backscatter signature. We use the Greenland Climate Network data to calibrate the QuikSCAT accumulation rate in order to estimate and map snow accumulation. QuikSCAT results capture the extreme snowfall in mid-April 2003, which deposited more than 0.5 m of snow in a day as measured by the automated weather station at the NASA South East site. Large-scale QuikSCAT results show an anomalous increase of snow accumulation over the southeast region of Greenland during the 2002-2003 freezing season.

  7. Mapping of ice layer extent and snow accumulation in the percolation zone of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.; Steffen, K.; Neumann, G.; Huff, R.

    2005-06-01

    The Greenland ice sheet underwent record extensive melt in 2002 and prolonged melt in 2003. The severe melting created a significant and extensive ice layer over the Greenland ice sheet. An innovative approach is developed to detect the ice layer formation using data acquired by the SeaWinds scatterometer on the QuikSCAT satellite. QuikSCAT backscatter together with in situ data from automatic weather stations of the Greenland Climate Network are used to map the extent of ice layer formation. The results reveal areas of extensive ice layer formed by the 2002 melt, which is consistent with the maximum melt extent in 2002. Moreover, during freezing seasons, QuikSCAT data show a linear decrease in backscatter (in decibels or dB) that is related to the amount of snow accumulation in the ice layer formation region. This snow accumulation signature is caused by the attenuation of radar waves in the snow layer, accumulating since the last major melt event, whose thickness appears as an exponential function in relation to the backscatter signature. We use the Greenland Climate Network data to calibrate the QuikSCAT accumulation rate in order to estimate and map snow accumulation. QuikSCAT results capture the extreme snowfall in mid-April 2003, which deposited more than 0.5 m of snow in a day as measured by the automated weather station at the NASA South East site. Large-scale QuikSCAT results show an anomalous increase of snow accumulation over the southeast region of Greenland during the 2002-2003 freezing season.

  8. Using reanalysis data for the prediction of seasonal wind turbine power losses due to icing

    NASA Astrophysics Data System (ADS)

    Burtch, Daniel G.

    The Northern Plains region of the United States is home to a significant amount of potential wind energy. However, in winter months capturing this potential power is severely impacted by the meteorological conditions, in the form of icing. Predicting the expected loss in power production due to icing is a valuable parameter that can be used in wind turbine operations, determination of wind turbine site locations and long-term energy estimates which are used for financing purposes. Currently, losses due to icing must be estimated when developing predictions for turbine feasibility and financing studies, while icing maps, a tool commonly used in Europe, are lacking in the United States. This study uses the Modern-Era Retrospective Analysis for Research and Applications (MERRA) dataset in conjunction with turbine production data and in-situ wind measurements to investigate six methods of predicting seasonal losses (October-March) due to icing at two sites located in Petersburg, ND and Valley City, ND. The prediction of icing losses is based on temperature and relative humidity thresholds and is accomplished using six methods. Three methods use a Measure-Correlate-Predict (MCP) and flow model (WAsP) analysis for the determination of wind speeds and MERRA for temperature and relative humidity, while three methods use MERRA for all three variables. For each season from 2002 to 2010, the predicted losses due to icing are determined for a range of relative humidity thresholds and compared with observed icing losses. An optimal relative humidity is then determined and tested on all seasons from 2002 to 2013. The prediction methods are then compared to a common practice used in the wind energy industry of assuming a constant percentage loss for icing over the same time period. The three methods using MERRA data alone show severe deficiencies in the accurate determination of wind speeds which leads to a large underprediction in accurate power output. Of the three MCP

  9. Deformation of subglacial till near ice-sheet grounding zones: theory and experiments

    NASA Astrophysics Data System (ADS)

    Kowal, K. N.; Worster, G.

    2015-12-01

    Large-scale ice-sheet dynamics pivot on the deformation and transport of subglacial sediment through changes in the basal sliding velocities of glaciers. Such unconsolidated, water-saturated glacigenic sediment, or till, is found to accumulate into sedimentary wedges, or till-deltas, in grounding zones separating floating ice shelves from grounded ice streams. In addition to affecting glacial slip, such sedimentation may serve to stabilise ice sheets against grounding-line retreat in response to rising sea levels. We present a fluid-mechanical explanation of the formation of these wedges in terms of the jump in hydrostatic loading and unloading of till across the grounding zone, and we compare our findings with geophysical data of sedimentary wedge formation at the modern-day grounding zone of Whillans Ice Stream, West Antarctica. We develop a theoretical model of wedge formation in which we treat both ice and till as viscous fluids spreading under gravity into an inviscid ocean and find that a similar wedge of underlying fluid accumulates around the grounding line in our series of fluid-mechanical laboratory experiments. The experiments were performed in a confined channel geometry. We extend our theory to unconfined geometries in which till deformation is resisted dominantly by vertical shear stresses and the flow of the overlying ice is resisted dominantly either by vertical shear stresses between the ice and till or by extensional stresses characteristic of floating ice shelves and shelfy streams. The former is relevant to less-lubricated, grounded ice sheets whereas the latter is relevant to well-lubricated ice streams, sliding over soft, deformable till of low viscosity and appreciable thickness. We formulate a local condition relating wedge slopes in each of the three scenarios and find a reasonable agreement with geophysical data.

  10. Using Reanalysis Data for the Prediction of Seasonal Wind Turbine Power Losses Due to Icing

    NASA Astrophysics Data System (ADS)

    Burtch, D.; Mullendore, G. L.; Delene, D. J.; Storm, B.

    2013-12-01

    The Northern Plains region of the United States is home to a significant amount of potential wind energy. However, in winter months capturing this potential power is severely impacted by the meteorological conditions, in the form of icing. Predicting the expected loss in power production due to icing is a valuable parameter that can be used in wind turbine operations, determination of wind turbine site locations and long-term energy estimates which are used for financing purposes. Currently, losses due to icing must be estimated when developing predictions for turbine feasibility and financing studies, while icing maps, a tool commonly used in Europe, are lacking in the United States. This study uses the Modern-Era Retrospective Analysis for Research and Applications (MERRA) dataset in conjunction with turbine production data to investigate various methods of predicting seasonal losses (October-March) due to icing at two wind turbine sites located 121 km apart in North Dakota. The prediction of icing losses is based on temperature and relative humidity thresholds and is accomplished using three methods. For each of the three methods, the required atmospheric variables are determined in one of two ways: using industry-specific software to correlate anemometer data in conjunction with the MERRA dataset and using only the MERRA dataset for all variables. For each season, a percentage of the total expected generated power lost due to icing is determined and compared to observed losses from the production data. An optimization is performed in order to determine the relative humidity threshold that minimizes the difference between the predicted and observed values. Eight seasons of data are used to determine an optimal relative humidity threshold, and a further three seasons of data are used to test this threshold. Preliminary results have shown that the optimized relative humidity threshold for the northern turbine is higher than the southern turbine for all methods

  11. Seasonal Ice loss in the Beaufort Sea: Toward Synchronicity and Prediction

    NASA Astrophysics Data System (ADS)

    Steele, M.; Dickinson, S.; Zhang, J.; Lindsay, R. W.

    2014-12-01

    The seasonal evolution of sea ice loss in the Beaufort Sea during 1979-2012 is examined, focusing on spatial differences between eastern and western sectors. Two stages in ice loss are identified: "opening" is defined as the spring decrease in ice concentration from its winter maximum below a value of 80% areal concentration; "retreat" is the summer decrease below 15% concentration. We consider three aspects of the problem, i.e. (i) the long-term mean, (ii) long-term linear trends, and (iii) year-to-year variability. We find that in the mean, ice opening occurs earliest in the southeast Beaufort Sea (SEB), forced by atmospheric heating acting on particularly thin ice relative to the southwestern Beaufort Sea (SWB). This thin SEB ice arises from divergence forced by easterly winds in fall and spring. There is no significant long-term trend in the date of SEB ice opening, although ice opening in the SWB is in fact trending toward earlier dates. This means that spatial differences in opening dates across the Beaufort Sea have been shrinking over the past 33 years, i.e., these dates are becoming more synchronous, a situation which may impact human and marine mammal activity in the area. Synchronicity in ice retreat dates is also increasing, although with no statistical significance at this time. Finally, we find that in any given year, an increase in monthly mean easterly winds of ~ 1 m/s during spring is associated with earlier summer retreat of 9-15 days, offering predictive capability with 1-2 months lead time.

  12. The effect of ocean heat flux on seasonal ice growth in Young Sound (Northeast Greenland)

    NASA Astrophysics Data System (ADS)

    Kirillov, Sergei; Dmitrenko, Igor; Babb, David; Rysgaard, Søren; Barber, David

    2015-07-01

    The seasonal ice cover plays an important role in the climate system limiting the exchange of heat and momentum across the air-water interface. Among other factors, sea ice is sensitive to the ocean heat flux. In this study, we use in situ oceanographic, sea ice, and meteorological data collected during winter 2013/2014 in Young Sound (YS) fjord in Northeast Greenland to estimate the ocean heat flux to the landfast ice cover. During the preceding ice-free summer, incident solar radiation caused sea surface temperatures of up to 5-6°C. Subsequently, this heat was transferred down to the intermediate depths, but returned to the surface and retarded ice growth throughout winter. Two different approaches were used to estimate the ocean heat fluxes; (i) a residual method based on a 1-D thermodynamic ice growth model and (ii) a bulk parameterization using friction velocities and available heat content of water beneath the ice. The average heat flux in the inner YS varied from 13 W m-2 in October-December to less than 2 W m-2 in January-May. An average heat flux of 9 W m-2 was calculated for the outer YS. Moreover, we show that the upward heat flux in the outer fjord is strongly modulated by surface outflow, which produced two maxima in heat flux (up to 18-24 W m-2) during 26 December to 27 January and from 11 February to 14 March. By May 2014, the upward ocean heat flux reduced the landfast ice thickness by 18% and 24% in the inner and outer YS, respectively.

  13. Seasonal forecast skill of Arctic sea ice area in a dynamical forecast system

    NASA Astrophysics Data System (ADS)

    Sigmond, M.; Fyfe, J. C.; Flato, G. M.; Kharin, V. V.; Merryfield, W. J.

    2013-02-01

    AbstractWe assess the <span class="hlt">seasonal</span> forecast skill of pan-Arctic sea <span class="hlt">ice</span> area in a dynamical forecast system that includes interactive atmosphere, ocean, and sea <span class="hlt">ice</span> components. Forecast skill is quantified by the correlation skill score computed from 12 month ensemble forecasts initialized in each month between January 1979 to December 2009. We find that forecast skill is substantial for all lead times and predicted <span class="hlt">seasons</span> except spring but is mainly due to the strong downward trend in observations for lead times of about 4 months and longer. Skill is higher when evaluated against an observation-based dataset with larger trends. The forecast skill when linear trends are removed from the forecasts and verifying observations is small and generally not statistically significant at lead times greater than 2 to 3 months, except for January/February when forecast skill is moderately high up to an 11 month lead time. For short lead times, high trend-independent forecast skill is found for October, while low skill is found for November/December. This is consistent with the <span class="hlt">seasonal</span> variation of observed lag correlations. For most predicted months and lead times, trend-independent forecast skill exceeds that of an anomaly persistence forecast, highlighting the potential for dynamical forecast systems to provide valuable <span class="hlt">seasonal</span> predictions of Arctic sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P23A1924H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P23A1924H"><span id="translatedtitle">Effects of Snowfall on the Thickness and Stability of Mars' <span class="hlt">Seasonal</span> <span class="hlt">Ice</span> Caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hayne, P. O.; Paige, D. A.; Aharonson, O.; Schofield, J. T.; Kass, D. M.; Kleinboehl, A.; Heavens, N. G.; Shirley, J. H.; McCleese, D. J.</p> <p>2012-12-01</p> <p><span class="hlt">Seasonal</span> exchange of carbon dioxide between the Martian atmosphere and <span class="hlt">ice</span> caps is responsible for cyclical variations of ~30% in global atmospheric pressure, as well as for the growth and retreat of the <span class="hlt">seasonal</span> <span class="hlt">ice</span> caps. Energy balance and general circulation models have had limited success in reproducing the important aspects of this cycle, largely due to uncertainties in the radiative properties (albedo and emissivity) of the <span class="hlt">ice</span> caps. Evidence from remote sensing by several different orbital investigations suggests that snowfall consisting primarily of solid CO2 contributes substantial material to the growing <span class="hlt">seasonal</span> caps, strongly affecting their radiative properties. However, the mass of material deposited as snow, its spatial and temporal variation, and its effect on the energy budget, have all remained uncertain. Using data from the Mars Climate Sounder (MCS), we have quantified and mapped snow cloud formation and surface accumulation based on opacity profiles and calculated infrared cooling rates. We then compared the derived snowfall distribution to <span class="hlt">seasonal</span> cap thicknesses derived from Mars Orbiter Laser Altimeter (MOLA) "crossover" data. Large variations in the occurrence, thickness, and timing of snow clouds are observed, with the most extensive and persistent clouds observed over the south polar residual cap (SPRC). We find a strong correlation between clouds, "cold spots" (regions of suppressed thermal emission), and <span class="hlt">seasonal</span> cap thickness. Furthermore, some of these regions of high snow cloud activity also exhibit high solar albedo in the spring and summer. Together, these results suggest that granular deposits of CO2 snow: 1) are thicker (probably due to lower density) on average than "slab <span class="hlt">ice</span>" formed by direct vapor deposition; 2) reduce energy loss by thermal emission during the polar night; and 3) reduce energy gain by reflecting solar radiation during spring and summer. As the snowiest place on Mars, the SPRC exhibits all of these properties</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.9227L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.9227L&link_type=ABSTRACT"><span id="translatedtitle">Upper Ocean Evolution Across the Beaufort Sea Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> from Autonomous Gliders</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; Rainville, Luc; Perry, Mary Jane</p> <p>2016-04-01</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> <span class="hlt">zone</span> (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 (PSW) and Atlantic (AW) 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> cover, and how the balance of processes shift as a function of <span class="hlt">ice</span> fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal <span class="hlt">ice</span> <span class="hlt">zone</span>, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, <span class="hlt">ice</span>-covered 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 as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kgm‑3, just above the PSW, consistently thickens near the <span class="hlt">ice</span> edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea <span class="hlt">ice</span> extent, and evolution over the summer to the start of freeze up.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140008938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140008938"><span id="translatedtitle">The Annual Glaciohydrology Cycle in the Ablation <span class="hlt">Zone</span> of the Greenland <span class="hlt">Ice</span> Sheet: Part 2. Observed and Modeled <span class="hlt">Ice</span> Flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colgan, William Terence; Rajaram, Harihar; Anderson, Robert S.; Steffen, Konrad; Zwally, H. Jay; Phillips, Thomas; Abdalati, Waleed</p> <p>2012-01-01</p> <p><span class="hlt">Ice</span> velocities observed in 2005/06 at three GPS stations along the Sermeq Avannarleq flowline, West Greenland, are used to characterize an observed annual velocity cycle. We attempt to reproduce this annual <span class="hlt">ice</span> velocity cycle using a 1-D <span class="hlt">ice</span>-flow model with longitudinal stresses coupled to a 1-D hydrology model that governs an empirical basal sliding rule. <span class="hlt">Seasonal</span> basal sliding velocity is parameterized as a perturbation of prescribed winter sliding velocity that is proportional to the rate of change of glacier water storage. The coupled model reproduces the broad features of the annual basal sliding cycle observed along this flowline, namely a summer speed-up event followed by a fall slowdown event. We also evaluate the hypothesis that the observed annual velocity cycle is due to the annual calving cycle at the terminus. We demonstrate that the <span class="hlt">ice</span> acceleration due to a catastrophic calving event takes an order of magnitude longer to reach CU/ETH ('Swiss') Camp (46km upstream of the terminus) than is observed. The <span class="hlt">seasonal</span> acceleration observed at Swiss Camp is therefore unlikely to be the result of velocity perturbations propagated upstream via longitudinal coupling. Instead we interpret this velocity cycle to reflect the local history of glacier water balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015BGeo...12.3009M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015BGeo...12.3009M&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Seasonal</span> dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost <span class="hlt">zone</span> of western Siberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manasypov, R. M.; Vorobyev, S. N.; Loiko, S. V.; Kritzkov, I. V.; Shirokova, L. S.; Shevchenko, V. P.; Kirpotin, S. N.; Kulizhsky, S. P.; Kolesnichenko, L. G.; Zemtzov, V. A.; Sinkinov, V. V.; Pokrovsky, O. S.</p> <p>2015-05-01</p> <p>Despite relatively good knowledge of the biogeochemistry of Siberian thermokarst lakes during summer base flow, their <span class="hlt">seasonal</span> dynamics remains almost unexplored. This work describes the chemical composition of ~130 thermokarst lakes ranging in size from a few m2 to several km2, located in the discontinuous permafrost <span class="hlt">zone</span>. Lakes were sampled during spring flood, just after the <span class="hlt">ice</span> break (early June), the end of summer (August), the beginning of <span class="hlt">ice</span> formation (October) and during the full freezing <span class="hlt">season</span> in winter (February). The lakes larger than 1000 m2 did not exhibit any statistically significant control of the lake size on dissolved organic carbon (DOC), the major and trace element concentrations over three major open water <span class="hlt">seasons</span>. On the annual scale, the majority of dissolved elements including organic carbon increased their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The concentrations of most trace elements (TEs) increased in the order spring > summer > autumn > winter. The <span class="hlt">ice</span> formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the <span class="hlt">ice</span> surface. This water was subsequently frozen and formed layered <span class="hlt">ice</span> rich in organic matter. As a result, the DOC and metal (Mn, Fe, Ni, Cu, Zn, As, Ba and Pb) concentrations were highest near the surface of the <span class="hlt">ice</span> column (0 to 20 cm) and decreased by a factor of 2 towards the bottom. The main implications of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficients of a TE between amorphous organo-ferric coagulates and lake water (<0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (<1 kDa, or <1-2 nm</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S44A..07A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S44A..07A"><span id="translatedtitle">Effects of <span class="hlt">Seasonal</span> and Secular changes in Antarctic Sea <span class="hlt">Ice</span> on Microseismic Noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anthony, R. E.; Aster, R. C.; Rowe, C. A.; Wiens, D. A.</p> <p>2014-12-01</p> <p>The Earth's background microseism noise spectrum, observed widely across the Earth is commonly dominated between ~1-30 seconds period by oceanic wave activity that arises when ocean swell is converted to (predominately) Rayleigh waves. Peak power levels in the microseism band at high-latitude stations typically coincide with large-scale extratropical cyclonic winter storm activity. However, due to the <span class="hlt">seasonal</span> formation of sea <span class="hlt">ice</span> around the continental shelves of polar regions, oceanic waves are impeded from efficiently exciting seismic energy, and annual peak microseism power thus occurs prior to the midwinter storm peak. We analyze recently collected Polar Earth Observatory (POLENET/A-NET) and Antarctica's Gamburtsev Province (GAMSEIS) seismic data to characterize the Antarctic microseism signal and its unique <span class="hlt">seasonality</span> and annual variations in each of three distinct bands: the high-frequency secondary microseism (1-5 s), the secondary microseism (5-10 s) and the primary microseism band (10-20 s). Power in these bands is found to be strongly anti-correlated with sea <span class="hlt">ice</span> extent. with the shorter period signals being exceptionally sensitive to local conditions. We quantitatively show that the formation of sea <span class="hlt">ice</span> may be capable of attenuating on-shore microseism power by as much as 90%. Additionally, we note a significant increase in primary microseism power attributable to near coastal Antarctic Peninsula sources during the last twenty years. This increase correlates with regional sea <span class="hlt">ice</span> loss driven by large-scale wind changes associated with the strengthening of the Southern Annular Mode. Investigation of microseism <span class="hlt">seasonality</span>, power, and decadal-scale trends in the Antarctic shows promise as a spatially integrated tool for monitoring and interpreting such sea <span class="hlt">ice</span> strength and extent, metrics through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014200','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014200"><span id="translatedtitle"><span class="hlt">Ice</span>-edge eddies in the Fram Strait marginal <span class="hlt">ice</span> <span class="hlt">zone</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>Johannessen, O.M.; Johannessen, J.A.; Svendsen, E.; Shuchman, R.A.; Campbell, W.J.; Josberger, E.</p> <p>1987-01-01</p> <p>Five prominent <span class="hlt">ice</span>-edge eddies in Fram Strait on the scale of 30 to 40 kilometers were observed over deep water within 77??N to 79??N and 5??W to 3??E. The use of remote sensing, a satellite-tracked buoy, and in situ oceanographic measurements showed the presence of eddies with orbital speeds of 30 to 40 centimeters per second and lifetimes of at least 20 days. <span class="hlt">Ice</span> ablation measurements made within one of these <span class="hlt">ice</span>-ocean eddies indicated that melting, which proceeded at rates of 20 to 40 centimeters per day, is an important process in determining the <span class="hlt">ice</span>-edge position. These studies give new insight on the formation, propagation, and dissipation of <span class="hlt">ice</span>-edge eddies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715613W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715613W"><span id="translatedtitle">The impacts of intense moisture transport on the deep and marginal sea-<span class="hlt">ice</span> <span class="hlt">zones</span> of the Arctic during winter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woods, Cian; Caballero, Rodrigo</p> <p>2015-04-01</p> <p> warming at the surface. There are an average of 14 such events that enter the polar cap each winter, driving about 50% of the <span class="hlt">seasonal</span> variation in surface temperature over the deep Arctic. We show that, over the last 30 years, the marginal <span class="hlt">ice-zones</span> in the Barents, Labrador and Chukchi Seas have experienced roughly a doubling in the frequency of these intense moisture intrusion events during winter. Interestingly, these are the regions that have experienced the most rapid wintertime <span class="hlt">ice</span> loss in the Arctic, raising the question: to what extent has the recent Arctic warming been driven by local vs. interannual/remote processes?</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_13");'>»</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_13");'>»</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://ntrs.nasa.gov/search.jsp?R=19890024800&hterms=Salt+properties&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSalt%2Bproperties','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890024800&hterms=Salt+properties&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSalt%2Bproperties"><span id="translatedtitle">Numerical simulations of the profile properties of undeformed first-year sea <span class="hlt">ice</span> during the growth <span class="hlt">season</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cox, G. F. N.; Weeks, W. F.</p> <p>1988-01-01</p> <p>A model is presented for estimating salinity profiles for the first-year sea <span class="hlt">ice</span> during the growth <span class="hlt">season</span>, in which <span class="hlt">ice</span> growth equations were coupled with salt entrapment and brine drainage relations to obtain the relationship between the initial <span class="hlt">ice</span> salinity and the <span class="hlt">ice</span>-growth velocity and seawater salinity, as well as the subsequent drainage of brine from the <span class="hlt">ice</span>. The results obtained were found to be in reasonable agreement with field observations in that they showed characteristic C-shaped profiles similar to natural profiles. The average <span class="hlt">ice</span> salinity values were also in reasonable agreement with field data. The predicted <span class="hlt">ice</span> property profiles give composite plate properties that are significantly different from bulk property estimates that would result by assuming that sea <span class="hlt">ice</span> could be represented as a homogeneous plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2012-05-31/pdf/2012-13160.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2012-05-31/pdf/2012-13160.pdf"><span id="translatedtitle">77 FR 32018 - Safety <span class="hlt">Zone</span>; Kemah Boardwalk Summer <span class="hlt">Season</span> Fireworks, Galveston Bay, Kemah, TX</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2012-05-31</p> <p>... INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety <span class="hlt">Zone</span>; Kemah Boardwalk Summer <span class="hlt">Season</span> Fireworks... mariners viewing the Kemah Boardwalk Summer <span class="hlt">Season</span> Fireworks. During periods of enforcement, entry into...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..260..396B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..260..396B"><span id="translatedtitle">Hemispheric asymmetry in martian <span class="hlt">seasonal</span> surface water <span class="hlt">ice</span> from MGS TES</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bapst, Jonathan; Bandfield, Joshua L.; Wood, Stephen E.</p> <p>2015-11-01</p> <p>The Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) visible/near-infrared and thermal infrared bolometers measured planetary broadband albedo and temperature for more than three Mars years. As <span class="hlt">seasons</span> progress on Mars, surface temperatures may fall below the frost point of volatiles in the atmosphere (namely, carbon dioxide and water). Systematic mapping of the spatial and temporal occurrence of these volatiles in the martian atmosphere, on the surface, and in the subsurface has shown their importance in understanding the climate of Mars. We examine TES daytime albedo, temperature, and atmospheric opacity data to map the latitudinal and temporal occurrence of <span class="hlt">seasonal</span> surface water frost on Mars. We expand on previous work by looking at the behavior of water frost over the entire martian year, made possible with comprehensive, multi-year data. Interpretations of frost are based on albedo changes and the corresponding daytime temperature range. Data is considered consistent with water frost when there are significant albedo increases (>0.05 relative to frost-free <span class="hlt">seasons</span>) and the observed temperatures are ∼170-200 K. We argue the presence of extensive water frost in the northern hemisphere, extending from the pole to ∼40°N, following <span class="hlt">seasonal</span> temperature trends. In the north, water frost first appears near the pole at Ls = ∼160° and is last observed at Ls = ∼90°. Extensive water frost is less evident in southern hemisphere data, though both hemispheres show data that are consistent with the presence of a water <span class="hlt">ice</span> annulus during <span class="hlt">seasonal</span> cap retreat. Hemispherical asymmetry in the occurrence of <span class="hlt">seasonal</span> water frost is due in part to the lower (∼40%) atmospheric water vapor abundances observed in the southern hemisphere. Our results are consistent with net transport of water vapor to the northern hemisphere. The deposition and sublimation of <span class="hlt">seasonal</span> water frost may significantly increase the near-surface water vapor density that could</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.6345A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.6345A"><span id="translatedtitle">Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">seasonal</span> and spatial mass variability from model simulations and GRACE (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, P. M.; Tedesco, M.; Schlegel, N.-J.; Luthcke, S. B.; Fettweis, X.; Larour, E.</p> <p>2015-11-01</p> <p>Improving the ability of regional climate models (RCMs) and <span class="hlt">ice</span> sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the 2003-2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the <span class="hlt">Ice</span> Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -179 and -240 Gt yr-1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an <span class="hlt">ice</span>-sheet wide scale, the timing of the modeled <span class="hlt">seasonal</span> cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived <span class="hlt">seasonal</span> cycle, within limits of uncertainty from the GRACE solution. However, on sub-<span class="hlt">ice</span>-sheet-wide scales, there are significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or unaccounted-for processes related to <span class="hlt">ice</span> dynamics or hydrology may lead to the observed differences. This highlights the need for further evaluation of modelled processes at regional and <span class="hlt">seasonal</span> scales, and further study of <span class="hlt">ice</span> sheet processes not</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016TCry...10.1259A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016TCry...10.1259A&link_type=ABSTRACT"><span id="translatedtitle">Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">seasonal</span> and spatial mass variability from model simulations and GRACE (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric</p> <p>2016-06-01</p> <p>Improving the ability of regional climate models (RCMs) and <span class="hlt">ice</span> sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for mass change are less well understood and modeled, and could potentially play an important role in future GrIS mass change. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the <span class="hlt">Ice</span> Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -178.9 ± 4.4 and -239.4 ± 7.7 Gt yr-1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an <span class="hlt">ice</span>-sheet-wide scale, the timing of the modeled <span class="hlt">seasonal</span> cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived <span class="hlt">seasonal</span> cycle, within limits of uncertainty from the GRACE solution. However, on sub-<span class="hlt">ice</span>-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or processes not accounted for by models related</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFMGC11A0529W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFMGC11A0529W&link_type=ABSTRACT"><span id="translatedtitle">Projected Duration of the Sea-<span class="hlt">Ice</span>-Free <span class="hlt">Season</span> in the Future Alaskan Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, M.; Overland, J. E.</p> <p>2014-12-01</p> <p>The change in the Arctic climate is fast and broad. Among many changes that have been observed, the reduction of sea <span class="hlt">ice</span> coverage has been one of the most significant factors. Continued reduction in sea <span class="hlt">ice</span> cover will probably result in longer open water duration, which is important for the shipping industry, marine mammals as well as other component of the local ecosystem. In this study we are to assess future sea <span class="hlt">ice</span> conditions, particularly the length of open water duration in the Alaskan Arctic over the next few decades using the latest coupled climate models (CMIP5). The Alaskan Arctic, including the Chukchi and the Beaufort Sea, has been a major region of summer sea <span class="hlt">ice</span> retreat since 2007. Based on the mean of 12 climate models, for the region north of the Bering Strait (70° N), future open-water duration may extend from a current 3-4 months to around five months by 2050. It is about one month shorter along the same latitude over the Beaufort Sea. The difference in the length of <span class="hlt">ice</span>-free <span class="hlt">season</span> between the north and the south will remain, but will be smaller in the 21st century compared with current condition. Open-water duration in the Alaskan Arctic expands quickly in these models over the next decades, in contrast to model under-predictions of sea <span class="hlt">ice</span> loss for the summer minimum over the Arctic wide domain. Uncertainty is generally ±one month estimated from the range of model results. Continued increases in open-water duration over the next two decades will impact regional economic access and potentially alter ecosystems, yet we need to keep in mind that from December through May most of the northern Alaskan Arctic will remain sea <span class="hlt">ice</span> covered into the second half of the century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2013-06-27/pdf/2013-15496.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2013-06-27/pdf/2013-15496.pdf"><span id="translatedtitle">78 FR 38584 - Safety <span class="hlt">Zone</span>; San Diego Symphony Summer POPS Fireworks 2013 <span class="hlt">Season</span>, San Diego, CA</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2013-06-27</p> <p>... FR Federal Register NPRM Notice of Proposed Rulemaking A. Regulatory History and Information The... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety <span class="hlt">Zone</span>; San Diego Symphony Summer POPS Fireworks... Symphony Summer POPS Fireworks 2013 <span class="hlt">season</span>. This safety <span class="hlt">zone</span> is necessary to provide for the safety of...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMS...142...62R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMS...142...62R"><span id="translatedtitle"><span class="hlt">Seasonal</span> dynamics in diatom and particulate export fluxes to the deep sea in the Australian sector of the southern Antarctic <span class="hlt">Zone</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rigual-Hernández, Andrés S.; Trull, Thomas W.; Bray, Stephen G.; Closset, Ivia; Armand, Leanne K.</p> <p>2015-02-01</p> <p>Particle fluxes were recorded over a one-year period (2001-02) in the southern Antarctic <span class="hlt">Zone</span> in the Australian Sector of the Southern Ocean. Here, we present the results on the <span class="hlt">seasonal</span> and vertical variability of biogenic particle and diatom valve fluxes. Total mass and diatom fluxes were highly <span class="hlt">seasonal</span>, with maxima registered during the austral summer and minima during winter. Biogenic opal dominated sedimentation, followed by carbonate, and very low levels of organic carbon (annual average 1.4%). The strong correlation between opal and organic carbon at both depth levels suggests that a significant fraction of organic matter exported to the deep sea was associated with diatom sedimentation events. <span class="hlt">Seasonal</span> diatom fluxes appear driven principally by changes in the flux of Fragilariopsis kerguelensis. The occurrence of the sea-<span class="hlt">ice</span> affiliated diatoms Fragilariopsis cylindrus and Fragilariopsis curta in both sediment traps is considered to correspond to the sedimentation of a diatom bloom advected from an area under the influence of sea <span class="hlt">ice</span>. Highest fluxes of the subsurface-dwelling species Thalassiothrix antarctica registered at the end of the summer bloom were linked to a drop of the light levels during the summer-autumn transition. This study provides the first annual observation on <span class="hlt">seasonal</span> succession of diatom species in the Australian sector of the Antarctic <span class="hlt">Zone</span>, and corresponds, in terms of magnitude and <span class="hlt">seasonality</span> of diatom fluxes, to those in neighbouring sectors (Pacific and eastern Atlantic).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900060071&hterms=pigment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpigment','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900060071&hterms=pigment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpigment"><span id="translatedtitle"><span class="hlt">Seasonal</span> and interannual variability of pigment concentrations across a California Current frontal <span class="hlt">zone</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thomas, A. C.; Strub, P. T.</p> <p>1990-01-01</p> <p>The <span class="hlt">seasonal</span> and interannual variability of the latitudinal position of the California Current frontal <span class="hlt">zone</span> was investigated by examining satellite images of phytoplankton pigment from the coastal-<span class="hlt">zone</span> color scanner for the periods 1979-1983 and 1986. The pigment concentrations associated with the zonal front were also determined. A general <span class="hlt">seasonal</span> cycle of pigment concentrations is was established. It was found that variations in the frontal structure are controlled primarily by changes in pigment concentration north of the front. <span class="hlt">Seasonal</span> variations were found to be minimal south of the front, where pigment concentrations remain low throughout the spring, summer, and fall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JMS.....2....1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JMS.....2....1C"><span id="translatedtitle">Copepods in <span class="hlt">ice</span>-covered seas—Distribution, adaptations to <span class="hlt">seasonally</span> limited food, metabolism, growth patterns and life cycle strategies in polar seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Conover, R. J.; Huntley, M.</p> <p>1991-07-01</p> <p>While a <span class="hlt">seasonal</span> <span class="hlt">ice</span> cover limits light penetration into both polar seas for up to ten months a year, its presence is not entirely negative. The mixed layer under sea <span class="hlt">ice</span> will generally be shallower than in open water at the same latitude and <span class="hlt">season</span>. <span class="hlt">Ice</span> forms a substrate on which primary production can be concentrated, a condition which contrasts with the generally dilute nutritional conditions which prevail in the remaining ocean. The combination of a shallow, generally stable mixed layer with a close proximity to abundant food make the under-<span class="hlt">ice</span> <span class="hlt">zone</span> a suitable nursery for both pelagic and benthic species, an upside-down benthos for opportunistic substrate browsers, and a rich feeding environment for species often considered to be neritic in temperate environments. Where the <span class="hlt">ice</span> cover is not continuous there may be a retreating <span class="hlt">ice</span> edge that facilitates the <span class="hlt">seasonal</span> production of phytoplankton primarily through increased stability from the melt water. <span class="hlt">Ice</span> edge blooms similarly encourage secondary production by pelagic animals. Pseudocalanus acuspes, which may be the most abundant and productive copepod in north polar latitudes, initiates growth at the start of the "spring bloom" of epontic algae, reaching sexual maturity at breakup or slightly before. In the Southern Hemisphere, the small neritic copepod Paralabidocera antarctica and adult krill have been observed to utilize <span class="hlt">ice</span> algae. Calanus hyperboreus breeds in the dark <span class="hlt">season</span> at depth and its buoyant eggs, slowly developing on the ascent, reach the under-<span class="hlt">ice</span> layer in April as nauplii ready to benefit from the primary production there. On the other hand, C. glacialis may initiate ontogenetic migrations and reproduction in response to increased erosion of <span class="hlt">ice</span> algae due to solar warming and melting at the <span class="hlt">ice</span>-water interface. While the same species in a phytoplankton bloom near the <span class="hlt">ice</span> edge reproduces actively, those under still-consolidated <span class="hlt">ice</span> nearby can have immature gonads. Diel migration and diel feeding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024509','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024509"><span id="translatedtitle"><span class="hlt">Seasonal</span> comparisons of sea <span class="hlt">ice</span> concentration estimates derived from SSM/I, OKEAN, and RADARSAT data</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, D.C.</p> <p>2002-01-01</p> <p>The Special Sensor Microwave Imager (SSM/I) microwave satellite radiometer and its predecessor SMMR are primary sources of information for global sea <span class="hlt">ice</span> and climate studies. However, comparisons of SSM/I, Landsat, AVHRR, and ERS-1 synthetic aperture radar (SAR) have shown substantial <span class="hlt">seasonal</span> and regional differences in their estimates of sea <span class="hlt">ice</span> concentration. To evaluate these differences, we compared SSM/I estimates of sea <span class="hlt">ice</span> coverage derived with the NASA Team and Bootstrap algorithms to estimates made using RADARSAT, and OKEAN-01 satellite sensor data. The study area included the Barents Sea, Kara Sea, Laptev Sea, and adjacent parts of the Arctic Ocean, during October 1995 through October 1999. <span class="hlt">Ice</span> concentration estimates from spatially and temporally near-coincident imagery were calculated using independent algorithms for each sensor type. The OKEAN algorithm implemented the satellite's two-channel active (radar) and passive microwave data in a linear mixture model based on the measured values of brightness temperature and radar backscatter. The RADARSAT algorithm utilized a segmentation approach of the measured radar backscatter, and the SSM/I <span class="hlt">ice</span> concentrations were derived at National Snow and <span class="hlt">Ice</span> Data Center (NSIDC) using the NASA Team and Bootstrap algorithms. <span class="hlt">Seasonal</span> and monthly differences between SSM/I, OKEAN, and RADARSAT <span class="hlt">ice</span> concentrations were calculated and compared. Overall, total sea <span class="hlt">ice</span> concentration estimates derived independently from near-coincident RADARSAT, OKEAN-01, and SSM/I satellite imagery demonstrated mean differences of less than 5.5% (S.D. <9.5%) during the winter period. Differences between the SSM/I NASA Team and the SSM/I Bootstrap concentrations were no more than 3.1% (S.D. <5.4%) during this period. RADARSAT and OKEAN-01 data both yielded higher total <span class="hlt">ice</span> concentrations than the NASA Team and the Bootstrap algorithms. The Bootstrap algorithm yielded higher total <span class="hlt">ice</span> concentrations than the NASA Team algorithm. Total <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.P72C..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.P72C..06R"><span id="translatedtitle"><span class="hlt">Seasonally</span>-Active Water on Mars: Vapour, <span class="hlt">Ice</span>, Adsorbate, and the Possibility of Liquid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richardson, M. I.</p> <p>2002-12-01</p> <p><span class="hlt">Seasonally</span>-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global <span class="hlt">seasonal</span> water cycle, tied proximately to planetary eccentricity, and the existence of residual <span class="hlt">ice</span> caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water <span class="hlt">ice</span> cap. The southern summer residual carbon dioxide <span class="hlt">ice</span> cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water <span class="hlt">ice</span> in the northern hemisphere by tropical water <span class="hlt">ice</span> clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground <span class="hlt">ice</span> in the mid- and high-latitudes, but this water is likely below the <span class="hlt">seasonal</span> skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PolSc..10...43S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PolSc..10...43S&link_type=ABSTRACT"><span id="translatedtitle">Interannual variability in sea-<span class="hlt">ice</span> thickness in the pack-<span class="hlt">ice</span> <span class="hlt">zone</span> off Lützow-Holm Bay, 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>Sugimoto, Fuko; Tamura, Takeshi; Shimoda, Haruhito; Uto, Shotaro; Simizu, Daisuke; Tateyama, Kazutaka; Hoshino, Seita; Ozeki, Toshihiro; Fukamachi, Yasushi; Ushio, Shuki; Ohshima, Kay I.</p> <p>2016-03-01</p> <p>Under the Japanese Antarctic Research Expedition (JARE) program, sea-<span class="hlt">ice</span> thickness has been routinely monitored off Lützow-Holm Bay (East Antarctica) during the summer (mid-December to early January) since 2000/01, using an electromagnetic induction (EM) instrument onboard the icebreaker Shirase. Analysis of these data over a 10-year period, combined with visual observations using a simplified form of the ASPeCt (Antarctic Sea <span class="hlt">ice</span> Processes and Climate) protocol, suggests a strong interannual variability in sea-<span class="hlt">ice</span> thickness in this region. For the repeat pack-<span class="hlt">ice</span> observation area, where the sea-<span class="hlt">ice</span> thickness averaged over the nine <span class="hlt">seasons</span> is ∼1.9 m, mean thicknesses of observed sea-<span class="hlt">ice</span> in 2010/11 and 2011/12 are exceptionally large, at ∼3.3 and ∼5.8 m, respectively. This result is strongly related to regional patterns of sea <span class="hlt">ice</span> dynamics. <span class="hlt">Ice</span> convergence caused by anomalous northerly winds was particularly high in 2011/12, suggesting that the extremely thick <span class="hlt">ice</span> observed in that <span class="hlt">season</span> resulted largely from sea-<span class="hlt">ice</span> deformation processes (including pressure ridging). Longer-term analysis of data from the past 34 years confirms that sea-<span class="hlt">ice</span> conditions and thickness off Lützow-Holm Bay in summer are determined mainly by the large-scale pattern of atmospheric pressure in December.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27458438','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27458438"><span id="translatedtitle">Unanticipated Geochemical and Microbial Community Structure under <span class="hlt">Seasonal</span> <span class="hlt">Ice</span> Cover in a Dilute, Dimictic Arctic Lake.</span></a></p> <p><a target="_blank" href="http://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 <span class="hlt">seasonally</span> frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under <span class="hlt">ice</span> cover. We assessed the vertical microbial community distribution and geochemical composition in early spring under <span class="hlt">ice</span> in a <span class="hlt">seasonally</span> <span class="hlt">ice</span>-covered lake in southwest Greenland using amplicon-based 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. PMID:27458438</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4932660','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4932660"><span id="translatedtitle">Unanticipated Geochemical and Microbial Community Structure under <span class="hlt">Seasonal</span> <span class="hlt">Ice</span> Cover in a Dilute, Dimictic Arctic 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>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 <span class="hlt">seasonally</span> frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under <span class="hlt">ice</span> cover. We assessed the vertical microbial community distribution and geochemical composition in early spring under <span class="hlt">ice</span> in a <span class="hlt">seasonally</span> <span class="hlt">ice</span>-covered lake in southwest Greenland using amplicon-based 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. PMID:27458438</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11E..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11E..06M"><span id="translatedtitle"><span class="hlt">Seasonal</span> and Interannual Glacier Terminus Fluctuations in Northwest Greenland and Links to Sea <span class="hlt">Ice</span> and Velocity Trends during the 21st Century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moon, T. A.; Joughin, I. R.; Smith, B. E.</p> <p>2014-12-01</p> <p>Current <span class="hlt">ice</span> loss from the Greenland <span class="hlt">Ice</span> Sheet is a significant component of global sea-level rise. Observations suggest that both increasing <span class="hlt">ice</span> flow speeds and sustained terminus retreat on most Greenland glaciers have increased mass loss via <span class="hlt">ice</span> discharge over the last several decades. However, our understanding of the mechanisms causing retreat and how well connected terminus fluctuations are to other dynamic changes in the <span class="hlt">ice</span> sheet remains limited. We examined terminus position, sea <span class="hlt">ice</span> and <span class="hlt">ice</span> mélange conditions, and <span class="hlt">seasonal</span> velocity patterns for 16 northwestern glaciers during 2009-2012, with extended 1999-2012 records for 4 glaciers. On a <span class="hlt">seasonal</span> scale, there is strong correspondence between terminus advance and retreat and sea <span class="hlt">ice/ice</span> mélange conditions, with a distinct <span class="hlt">seasonal</span> signature. Longer sea-<span class="hlt">ice</span>-free periods and reductions in rigid mélange formation appear to induce sustained multi-year retreat outside of the <span class="hlt">seasonal</span> signal. While <span class="hlt">seasonal</span> terminus retreat is not clearly linked to <span class="hlt">seasonal</span> velocity patterns, multi-year retreat is accompanied by interannual speedup on most glaciers. Projections of continued warming and longer sea-<span class="hlt">ice</span>-free periods around Greenland indicate that notable retreat over wide areas may continue. This sustained retreat likely will contribute to multi-year speedup. Longer melt <span class="hlt">seasons</span> and earlier breakup of mélange may also alter the timing of <span class="hlt">seasonal</span> <span class="hlt">ice</span>-dynamic patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.7223B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.7223B"><span id="translatedtitle">Air-sea exchange of carbon dioxide in the Southern Ocean and Antarctic marginal <span class="hlt">ice</span> <span class="hlt">zone</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Butterworth, Brian J.; Miller, Scott D.</p> <p>2016-07-01</p> <p>Direct carbon dioxide flux measurements using eddy covariance from an icebreaker in the high-latitude Southern Ocean and Antarctic marginal <span class="hlt">ice</span> <span class="hlt">zone</span> are reported. Fluxes were combined with the measured water-air carbon dioxide partial pressure difference (ΔpCO2) to compute the air-sea gas transfer velocity (k, normalized to Schmidt number 660). The open water data showed a quadratic relationship between k (cm h-1) and the neutral 10 m wind speed (U10n, m s-1), kopen = 0.245 U10n2 + 1.3, in close agreement with decades old tracer-based results and much lower than cubic relationships inferred from previous open ocean eddy covariance studies. In the marginal <span class="hlt">ice</span> <span class="hlt">zone</span>, the effective gas transfer velocity decreased in proportion to sea <span class="hlt">ice</span> cover, in contrast with predictions of enhanced gas exchange in the presence of sea <span class="hlt">ice</span>. The combined open water and marginal <span class="hlt">ice</span> <span class="hlt">zone</span> results affect the calculated magnitude and spatial distribution of Southern Ocean carbon flux.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009100','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009100"><span id="translatedtitle">The Annual Glaciohydrology Cycle in the Ablation <span class="hlt">Zone</span> of the Greenland <span class="hlt">Ice</span> Sheet: Part 1. Hydrology Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colgan, William; Rajaram, Harihar; Anderson, Robert; Steffen. Konrad; Phillips, Thomas; Zwally, H. Jay; Abdalati, Waleed</p> <p>2012-01-01</p> <p>We apply a novel one-dimensional glacier hydrology model that calculates hydraulic head to the tidewater-terminating Sermeq Avannarleq flowline of the Greenland <span class="hlt">ice</span> sheet. Within a plausible parameter space, the model achieves a quasi-steady-state annual cycle in which hydraulic head oscillates close to flotation throughout the ablation <span class="hlt">zone</span>. Flotation is briefly achieved during the summer melt <span class="hlt">season</span> along a approx.17 km stretch of the approx.50 km of flowline within the ablation <span class="hlt">zone</span>. Beneath the majority of the flowline, subglacial conduit storage closes (i.e. obtains minimum radius) during the winter and opens (i.e. obtains maximum radius) during the summer. Along certain stretches of the flowline, the model predicts that subglacial conduit storage remains open throughout the year. A calculated mean glacier water residence time of approx.2.2 years implies that significant amounts of water are stored in the glacier throughout the year. We interpret this residence time as being indicative of the timescale over which the glacier hydrologic system is capable of adjusting to external surface meltwater forcings. Based on in situ <span class="hlt">ice</span> velocity observations, we suggest that the summer speed-up event generally corresponds to conditions of increasing hydraulic head during inefficient subglacial drainage. Conversely, the slowdown during fall generally corresponds to conditions of decreasing hydraulic head during efficient subglacial drainage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26342133','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26342133"><span id="translatedtitle">Winter severity determines functional trait composition of phytoplankton in <span class="hlt">seasonally</span> <span class="hlt">ice</span>-covered lakes.</span></a></p> <p><a target="_blank" href="http://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 <span class="hlt">seasonally</span> <span class="hlt">ice</span>-covered 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), covering 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-based 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> cover; phototrophic taxa) or severe winters (i.e., thick <span class="hlt">ice</span> cover; exclusively motile taxa). Based on predicted milder winters for temperate regions and a reduction in <span class="hlt">ice</span>-cover 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://hdl.handle.net/2060/20050167779','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050167779"><span id="translatedtitle">Mars Water <span class="hlt">Ice</span> and Carbon Dioxide <span class="hlt">Seasonal</span> Polar Caps: GCM Modeling and Comparison with Mars Express Omega Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Forget, F.; Levrard, B.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Bibring, J. P.</p> <p>2005-01-01</p> <p>To better understand the behavior of the Mars CO2 <span class="hlt">ice</span> <span class="hlt">seasonal</span> polar caps, and in particular interpret the the Mars Express Omega observations of the recession of the northern <span class="hlt">seasonal</span> cap, we present some simulations of the Martian Climate/CO2 cycle/ water cycle as modeled by the Laboratoire de Meteorologie Dynamique (LMD) global climate model.</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_13");'>»</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_9");'>9</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_13");'>»</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/cgi-bin/nph-data_query?bibcode=2015AGUFM.A53C0391Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.A53C0391Y&link_type=ABSTRACT"><span id="translatedtitle">A Regional Model for <span class="hlt">Seasonal</span> Sea <span class="hlt">Ice</span> Prediction in the Pacific Sector of 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>Yuan, X.; Li, Y.; Chen, D.; Zhang, Q.; Li, C.; Niu, F.; Sun, Y.</p> <p>2015-12-01</p> <p>The recent results from a linear Markov model for <span class="hlt">seasonal</span> prediction of pan-Arctic sea <span class="hlt">ice</span> concentration (SIC) show that sea <span class="hlt">ice</span> in the Pacific sector has the lowest predictability compared to other regions. One reason could be that the climate variability in the Atlantic sector is so dominant that other signals in the Arctic climate system do not appear in the leading modes used for model construction. This study develops a regional Markov model to improve <span class="hlt">seasonal</span> forecasting of SIC in the Pacific sector. The model climate system consists of various combinations of the monthly mean series of SIC, sea surface temperature (SST), surface air temperature (SAT), pressure/geopotential height fields and winds at pressure levels. Multivariate empirical orthogonal functions (MEOF) and rotated MEOF are applied to each set of data to reduce the model dimensions. After a series of experiments, the final model configuration selects 23 rotated MEOF modes from a data matrix of three variables (SIC, SST and SAT). This regional model shows considerable improvement in the prediction skill in the Pacific sector in all <span class="hlt">seasons</span>. The anomaly correlation skill increases by 0.2 at 1- to 4-month leads in the Bering Sea, and by 0.1 at 1- to 10-month leads in the Sea of Okhotsk. In general, the model performs better in summer and fall than in winter and spring. On average, the correlation skill can reach 0.6 at a 2-month (4-month) lead in the Bering Sea (the Sea of Okhotsk).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ClDy...25..477C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ClDy...25..477C"><span id="translatedtitle">Influence of high latitude <span class="hlt">ice</span> cover on the marine Intertropical Convergence <span class="hlt">Zone</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chiang, John C. H.; Bitz, Cecilia M.</p> <p>2005-10-01</p> <p>We investigate the causes for a strong high latitude imposed <span class="hlt">ice</span> (land or sea) influence on the marine Intertropical Convergence <span class="hlt">Zone</span> (ITCZ) in the Community Climate Model version 3 coupled to a 50-m slab ocean. The marine ITCZ in all the ocean basins shift meridionally away from the hemisphere with an imposed added <span class="hlt">ice</span> cover, altering the global Hadley circulation with an increased tropical subsidence in the hemisphere with imposed <span class="hlt">ice</span> and uplift in the other. The effect appears to be independent of the longitudinal position of imposed <span class="hlt">ice</span>. The anomalous <span class="hlt">ice</span> induces a rapid cooling and drying of the air and surface over the entire high- and midlatitudes; subsequent progression of cold anomalies occurs in the Pacific and Atlantic northeasterly trade regions, where a wind-evaporation-sea surface temperature (SST) feedback initiates progression of a cold SST ‘front’ towards the ITCZ latitudes. Once the cooler SST reaches the ITCZ latitude, the ITCZ shifts southwards, aided by positive feedbacks associated with the displacement. The ITCZ displacement transports moisture away from the colder and drier hemisphere into the other hemisphere, resulting in a pronounced hemispheric asymmetric response in anomalous specific humidity; we speculate that the atmospheric humidity plays a central role in the hemispheric asymmetric nature of the climate response to high latitude <span class="hlt">ice</span> cover anomalies. From an energy balance viewpoint, the increased outgoing radiative flux at the latitudes of the imposed <span class="hlt">ice</span> is compensated by an increased radiative energy flux at the tropical latitudes occupied by the displaced ITCZ, and subsequently transported by the altered Hadley and eddy circulations to the imposed <span class="hlt">ice</span> latitudes. The situation investigated here may be applicable to past climates like the Last Glacial Maximum where hemispheric asymmetric changes to <span class="hlt">ice</span> cover occurred. Major caveats to the conclusions drawn include omission of interactive sea <span class="hlt">ice</span> physics and ocean dynamical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcDyn.tmp...47G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcDyn.tmp...47G"><span id="translatedtitle">Wave observation in the marginal <span class="hlt">ice</span> <span class="hlt">zone</span> with the TerraSAR-X satellite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gebhardt, Claus; Bidlot, Jean-Raymond; Gemmrich, Johannes; Lehner, Susanne; Pleskachevsky, Andrey; Rosenthal, Wolfgang</p> <p>2016-05-01</p> <p>This article investigates the penetration of ocean waves into the marginal <span class="hlt">ice</span> <span class="hlt">zone</span> (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the <span class="hlt">ice</span>-free open ocean to solid <span class="hlt">ice</span>. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the <span class="hlt">ice</span>-covered region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016OcDyn..66..839G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016OcDyn..66..839G&link_type=ABSTRACT"><span id="translatedtitle">Wave observation in the marginal <span class="hlt">ice</span> <span class="hlt">zone</span> with the TerraSAR-X satellite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gebhardt, Claus; Bidlot, Jean-Raymond; Gemmrich, Johannes; Lehner, Susanne; Pleskachevsky, Andrey; Rosenthal, Wolfgang</p> <p>2016-07-01</p> <p>This article investigates the penetration of ocean waves into the marginal <span class="hlt">ice</span> <span class="hlt">zone</span> (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the <span class="hlt">ice</span>-free open ocean to solid <span class="hlt">ice</span>. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the <span class="hlt">ice</span>-covered region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989EOSTr..70..545M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989EOSTr..70..545M"><span id="translatedtitle">MIZEX East 1987: Winter Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> Program in the Fram Strait and Greenland Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>MIZEX'87 Group</p> <p></p> <p>The overall objective o f MIZEX is to gain a better understanding of the mesoscale physical and biological processes by which atmosphere, <span class="hlt">ice</span>, and ocean interact in the marginal <span class="hlt">ice</span> <span class="hlt">zones</span> (MIZ) that are found at the boundaries between <span class="hlt">ice</span>-covered and open oceans. Improved modeling and better prediction of <span class="hlt">ice</span>-edge position, <span class="hlt">ice</span> concentration, and <span class="hlt">ice</span> type in these regions would be a major step toward expanding human activities, for example, seaborne commerce, fishing, oil exploration and production, and naval operations. In addition, when more accurate parameterizations of mesoscale physical processes are available for inclusion in large-scale models, the result will be a major improvement in hemispherical climatological studies.Winter MIZEX '87 was conducted during March and April 1987 in the Fram Strait and Greenland Sea (see cover) and extended along the MIZ from about 75°N-79°N and 5°W-5°E. The experiment included an intensive 2-day investigation of the Barents Sea MIZ carried out between the southern tip of Svalbard and Bear Island. Two Norwegian ships, R/V Håakon Mosby and the <span class="hlt">ice</span>-strengthened R/V Polar Circle, and the R/V Valdivia of the Federal Republic of Germany participated in the experiment. Flight operations were carried out by two Canadian aircraft equipped with Synthetic Aperature Radar (SAR), a U.S. plane equipped with passive microwave sensors, a Norwegian P3 aircraft, and a helicopter based on the Polar Circle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813854S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813854S"><span id="translatedtitle">Airborne remote sensing of surface waves in the marginal <span class="hlt">ice</span> <span class="hlt">zone</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sutherland, Peter; Gascard, Jean-Claude</p> <p>2016-04-01</p> <p>The propagation of ocean surface waves into sea <span class="hlt">ice</span> is an important physical process in an increasingly <span class="hlt">ice</span>-free Arctic basin. Wave-fetch-<span class="hlt">ice</span> feedbacks are a key unknown in climate-scale simulations of Arctic sea <span class="hlt">ice</span>, and wave effects are one of the greatest sources of uncertainty in operational <span class="hlt">ice</span> models. We will present a technique developed for measuring waves in sea <span class="hlt">ice</span> using airborne scanning lidar. Applying this technique to data taken during the CryoSat Validation Experiment, 2006, we were able to observe the spatial directional spectra of surface waves propagating tens of kilometres into the marginal <span class="hlt">ice</span> <span class="hlt">zone</span>. Wave energy attenuation and the evolution of spectral spreading were observed. Co-located visible imagery was then used to relate floe size distributions to the wave spectra. The broader-scale implications of our results, which are particularly relevant to discerning between scattering-based and dissipative wave attenuation models, will be discussed. Suggestions for minor modifications to future airborne campaigns, that would allow significantly improved capture of wave processes, will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11A0349S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11A0349S"><span id="translatedtitle">The Floe Size Distribution in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> of the Beaufort and Chukchi Seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schweiger, A. J. B.; Stern, H. L., III; Stark, M.; Zhang, J.; Steele, M.; Hwang, P. B.</p> <p>2014-12-01</p> <p>Several key processes in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> (MIZ) of the Arctic Ocean are related to the size of the <span class="hlt">ice</span> floes, whose diameters range from meters to tens of kilometers. The floe size distribution (FSD) influences the mechanical properties of the <span class="hlt">ice</span> cover, air-sea momentum and heat transfer, lateral melting, and light penetration. However, no existing sea-<span class="hlt">ice</span>/ocean models currently simulate the FSD in the MIZ. Model development depends on observations of the FSD for parameterization, calibration, and validation. To support the development and implementation of the FSD in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> Modeling and Assimilation System (MIZMAS), we have analyzed the FSD in the Beaufort and Chukchi seas using multiple sources of satellite imagery: NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites (250 m pixel size), the USGS Landsat 8 satellite (80 m pixel size), the Canadian Space Agency's synthetic aperture radar (SAR) on RADARSAT (50 meter pixel size), and declassified National Technical Means imagery from the Global Fiducials Library (GFL) of the USGS (1 m pixel size). The procedure for identifying <span class="hlt">ice</span> floes in the imagery begins with manually delineating cloud-free regions (if necessary). A threshold is then chosen to separate <span class="hlt">ice</span> from water. Morphological operations and other semi-automated techniques are used to identify individual floes, whose properties are then easily calculated. We use the mean caliper diameter as the measure of floe size. The FSD is adequately described by a power-law in which the exponent characterizes the relative number of large and small floes. Changes in the exponent over time and space reflect changes in physical processes in the MIZ, such as sea-<span class="hlt">ice</span> deformation, fracturing, and melting. We report results of FSD analysis for the spring and summer of 2013 and 2014, and show how the FSD will be incorporated into the MIZMAS model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1762A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1762A"><span id="translatedtitle">Global warming related transient albedo feedback in the Arctic and its relation to the <span class="hlt">seasonality</span> of 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>Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco</p> <p>2015-04-01</p> <p>The Arctic is warming two to three times faster than the global average. Arctic sea <span class="hlt">ice</span> cover is very sensitive to this warming and has reached historic minima in late summer in recent years (i.e. 2007, 2012). Considering that the Arctic Ocean is mainly <span class="hlt">ice</span>-covered and that the albedo of sea <span class="hlt">ice</span> is very high compared to that of open water, the change in sea <span class="hlt">ice</span> cover is very likely to have a strong impact on the local surface albedo feedback. Here we quantify the temporal changes in surface albedo feedback in response to global warming. Usually feedbacks are evaluated as being representative and constant for long time periods, but we show here that the strength of climate feedbacks in fact varies strongly with time. For instance, time series of the amplitude of the surface albedo feedback, derived from future climate simulations (CIMP5, RCP8.5 up to year 2300) using a kernel method, peaks around the year 2100. This maximum is likely caused by an increased <span class="hlt">seasonality</span> in sea-<span class="hlt">ice</span> cover that is inherently associated with sea <span class="hlt">ice</span> retreat. We demonstrate that the Arctic average surface albedo has a strong <span class="hlt">seasonal</span> signature with a maximum in spring and a minimum in late summer/autumn. In winter when incoming solar radiation is minimal the surface albedo doesn't have an important effect on the energy balance of the climate system. The annual mean surface albedo is thus determined by the <span class="hlt">seasonality</span> of both downwelling shortwave radiation and sea <span class="hlt">ice</span> cover. As sea <span class="hlt">ice</span> cover reduces the <span class="hlt">seasonal</span> signature is modified, the transient part from maximum sea <span class="hlt">ice</span> cover to its minimum is shortened and sharpened. The sea <span class="hlt">ice</span> cover is reduced when downwelling shortwave radiation is maximum and thus the annual surface albedo is drastically smaller. Consequently the change in annual surface albedo with time will become larger and so will the surface albedo feedback. We conclude that a stronger <span class="hlt">seasonality</span> in sea <span class="hlt">ice</span> leads to a stronger surface albedo feedback, which accelerates</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H41F1107J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H41F1107J"><span id="translatedtitle">Groundwater-Stream Interactions in a <span class="hlt">Seasonal</span> Flooded Riparian <span class="hlt">Zone</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, J. K.; Engesgaard, P. K.; Nilsson, B.</p> <p>2011-12-01</p> <p>At Odense River in Denmark several wetlands/riparian <span class="hlt">zones</span> have recently been reconstructed with one objective to rehabilitate the wetland/riparian <span class="hlt">zone</span> as a buffer strip enhancing depletion of agricultural inputs of diffuse pollutants like nutrients and pesticides to the receiving Odense River. The approach is initiated to either force the polluted groundwater through a reactive buffer strip and/or allowing polluted river water to flood and infiltrate the reactive riparian <span class="hlt">zone</span>. However, often the hydraulics of these systems is poorly understood and therefore it is difficult to evaluate the efficiency of the systems and several questions often remain unanswered; Is residence time in the riparian <span class="hlt">zone</span> long enough to sufficiently deplete the pollutants? What are the effects of flooding and infiltration of polluted river water on the hydraulics of the buffer strip? Can differences in groundwater flow paths in periods with flooding reduce the effect of the buffer strip by shortening flow paths to the surface water and hence alter residence time; that is, does groundwater-stream interaction change during and after flooding? And finally; is it possible to upscale the overall effect for a whole river system? Monitoring is ongoing in a reconstructed riparian <span class="hlt">zone</span> heavily polluted with nitrate as a part of the EU project AQUAREHAB. The setup is a grid of 50 piezometers installed in selected transects following groundwater flow paths from an adjacent agricultural site to the river. The piezometer setup permits us to follow the changes in hydraulic heads and to perform water sampling for chemical characterization. The site has been characterized by geophysical Multi-Electrode-Profiling and correlated to two geotechnical drillings to depths of 20 m, by slug-test, and hydro periods have been determined from continuous recording of river stage. Temperature is used as a tracer for monitoring discharge of groundwater to the stream (non-continuous converted to an estimate of flux</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.1118S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.1118S"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">ice</span> loss in the Beaufort Sea: Toward synchrony and prediction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steele, Michael; Dickinson, Suzanne; Zhang, Jinlun; W. Lindsay, Ron</p> <p>2015-02-01</p> <p>The <span class="hlt">seasonal</span> evolution of sea <span class="hlt">ice</span> loss in the Beaufort Sea during 1979-2012 is examined, focusing on differences between eastern and western sectors. Two stages in <span class="hlt">ice</span> loss are identified: the Day of Opening (DOO) is defined as the spring decrease in <span class="hlt">ice</span> concentration from its winter maximum below a value of 0.8 areal concentration; the Day of Retreat (DOR) is the summer decrease below 0.15 concentration. We consider three aspects of the subject, i.e., (i) the long-term mean, (ii) long-term linear trends, and (iii) interannual variability. We find that in the mean, DOO occurs earliest in the eastern Beaufort Sea (EBS) owing to easterly winds which act to thin the <span class="hlt">ice</span> there, relative to the western Beaufort Sea (WBS) where <span class="hlt">ice</span> has been generally thicker. There is no significant long-term trend in EBS DOO, although WBS DOO is in fact trending toward earlier dates. This means that spatial differences in DOO across the Beaufort Sea have been shrinking over the past 33 years, i.e., these dates are becoming more synchronous, a situation which may impact human and marine mammal activity in the area. Retreat dates are also becoming more synchronous, although with no statistical significance over the studied time period. Finally, we find that in any given year, an increase in monthly mean easterly winds of ˜1 m/s during spring is associated with earlier summer DOR of 6-15 days, offering predictive capability with 2-4 months lead time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998DSRI...45.1357C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998DSRI...45.1357C&link_type=ABSTRACT"><span id="translatedtitle">Changes in lipid composition of copepods and Euphausia superba associated with diet and environmental conditions in the marginal <span class="hlt">ice</span> <span class="hlt">zone</span>, Bellingshausen Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cripps, G. C.; Hill, H. J.</p> <p>1998-08-01</p> <p>The effect of varying diet and environmental conditions at the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> (MIZ) on the fatty acid and hydrocarbon compositions of five species of copepod and krill, Euphausia superba, was investigated. Zooplankton at the MIZ experienced a range of conditions, from a low algal biomass (mainly flagellates) under pack-<span class="hlt">ice</span> to a spring bloom dominated by diatoms in the open ocean. Principal Component Analysis classified the copepods into three dietary regimes: (i) omnivores or general algal feeders under the pack <span class="hlt">ice</span>, (ii) dinoflagellate feeders, and (iii) diatom feeders in the open ocean. This classification was supported by the distribution of the diatom marker n-heneicosahexaene ( n-C 21:6) and a general indicator of herbivory, the isoprenoid pristane. The fatty acid and hydrocarbon composition reflected dietary preferences and availability as the <span class="hlt">season</span> progressed. Of the copepods under the pack-<span class="hlt">ice</span>, Oithona spp. was omnivorous whereas Calanus propinquus was feeding preferentially on flagellates. Metridia gerlachei fed on flagellates in all conditions, but also included diatoms in its diet during the bloom. Calanoides acutus and Rhincalanus gigas, which passed the winter in diapause, were feeding almost exclusively on diatoms in the open ocean. Euphausia superba, which were also mainly diatom feeders in the open ocean, were feeding on the sea-<span class="hlt">ice</span> algae (diatoms) and suspended material from the water column (dinoflagellates) under the pack-<span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C11A..08T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C11A..08T"><span id="translatedtitle">Bathymetry of Grounding <span class="hlt">Zones</span> and Sub-<span class="hlt">Ice</span> Shelf Cavities of the Amundsen Sea, from Operation <span class="hlt">Ice</span>Bridge Gravity Inversions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tinto, K. J.; Cochran, J. R.; Bell, R. E.</p> <p>2012-12-01</p> <p>In order to understand the observed changes in thinning and grounding line position of outlet glaciers it is essential to have accurate maps of the bathymetry of the sea floor within and around the grounding <span class="hlt">zone</span>. This bathymetry controls the stability of the grounding line as well as access and circulation of seawater under their stabilizing <span class="hlt">ice</span> shelves. Since 2009 Operation <span class="hlt">Ice</span>Bridge has flown gridded surveys over four of the <span class="hlt">ice</span> shelves of the Amundsen Sea embayment. We present a 3D inversion of the gravity from the region, supplemented by 2D profile models across the <span class="hlt">ice</span> shelves to provide a self-consistent bathymetric model of the grounding <span class="hlt">zone</span> and sub <span class="hlt">ice</span> cavity of Pine Island, Thwaites, Dotson and Crosson <span class="hlt">ice</span> shelves. Much attention has been paid to the largest outlet glaciers of the Amundsen Sea, and to the bathymetry beneath the floating <span class="hlt">ice</span> in front of their grounding <span class="hlt">zones</span>. Considerable changes have also been observed from the smaller Amundsen <span class="hlt">ice</span> shelves, Crosson and Dotson, which flow to the east and north respectively, between Thwaites Glacier and Getz <span class="hlt">ice</span> shelf, but little is known about their sub-<span class="hlt">ice</span> bathymetry. The Amundsen Sea region is vulnerable to the influence of relatively warm circumpolar deep water encroaching on to the continental shelf. The influence of these waters at the grounding <span class="hlt">zone</span> of the glaciers in the region is dictated by the depth and orientation of bathymetric features of the sea floor. The dominant geological fabric of the region is a NE-SW trending series of ridges and troughs, formed in association with the rifting of the Amundsen Sea region. The bathymetry models from OIB gravity inversions reveal the continuation of the deep (~1500 m) trough of the Kohler Glacier under Crosson <span class="hlt">Ice</span> Shelf. At the eastern end of the trough, at the front of Crosson <span class="hlt">ice</span> shelf, the sea floor rises to an average of ~500 m depth over a broad, 50 km wide region. Further east from here the NE-SW fabric is continued in a previously reported ridge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27106334','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27106334"><span id="translatedtitle">Identification and quantification of soundscape components in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geyer, Florian; Sagen, Hanne; Hope, Gaute; Babiker, Mohamed; Worcester, Peter F</p> <p>2016-04-01</p> <p>Acoustic experiments using an integrated <span class="hlt">ice</span> station were carried out during August 2012 and September 2013 in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> (MIZ) of Fram Strait. The two experiments lasted four days each and collected under-<span class="hlt">ice</span> acoustic recordings together with wave-in-<span class="hlt">ice</span> and meteorological data. Synthetic aperture radar satellite data provided information on regional <span class="hlt">ice</span> conditions. Four major components of the under-<span class="hlt">ice</span> soundscape were identified: ship cavitation noise, seismic airgun noise, marine mammal vocalizations, and natural background noise. Ship cavitation noise was connected to heavy icebreaking. It dominated the soundscape at times, with noise levels (NLs) 100 km from the icebreaker increased by 10-28 dB. Seismic airgun noise that originated from seismic surveys more than 800 km away was present during 117 out of 188 observation hours. It increased NLs at 20-120 Hz by 2-6 dB. Marine mammal vocalizations were a minor influence on measured NLs, but their prevalence shows the biological importance of the MIZ. The 10th percentile of the noise distributions was used to identify the ambient background noise. Background NLs above 100 Hz differed by 12 dB between the two experiments, presumably due to variations in natural noise sources. PMID:27106334</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70073506','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70073506"><span id="translatedtitle">Mapping the grounding <span class="hlt">zone</span> of Ross <span class="hlt">Ice</span> Shelf using ICESat laser altimetry</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brunt, Kelly M.; Fricker, Helen A.; Padman, Laurie; Scambos, Ted A.; O'Neel, Shad</p> <p>2010-01-01</p> <p>We use laser altimetry from the <span class="hlt">Ice</span>, Cloud, and land Elevation Satellite (ICESat) to map the grounding <span class="hlt">zone</span> (GZ) of the Ross <span class="hlt">Ice</span> Shelf, Antarctica, at 491 locations where ICESat tracks cross the grounding line (GL). <span class="hlt">Ice</span> flexure in the GZ occurs as the <span class="hlt">ice</span> shelf responds to short-term sea-level changes due primarily to tides. ICESat repeat-track analysis can be used to detect this region of flexure since each repeated pass is acquired at a different tidal phase; the technique provides estimates for both the landward limit of flexure and the point where the <span class="hlt">ice</span> becomes hydrostatically balanced. We find that the ICESat-derived landward limits of tidal flexure are, in many places, offset by several km (and up to ∼60 km) from the GL mapped previously using other satellite methods. We discuss the reasons why different mapping methods lead to different GL estimates, including: instrument limitations; variability in the surface topographic structure of the GZ; and the presence of <span class="hlt">ice</span> plains. We conclude that reliable and accurate mapping of the GL is most likely to be achieved when based on synthesis of several satellite datasets</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP33D..03Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP33D..03Y"><span id="translatedtitle">Contraction of the Western Pacific Intertropical Convergence <span class="hlt">Zone</span> During 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>Yan, H.; Wei, W.; Soon, W.; Zhou, W.; An, Z.</p> <p>2015-12-01</p> <p>Both palaeoclimate reconstructions and climate modeling have demonstrated thatprecipitation in low latitudes is primarily controlled by north- south migration of the globalIntertropical Convergence <span class="hlt">Zone</span> on millennial to orbital timescales. These migrations areassociated with the occurrence of opposite rainfall variations between the twohemispheres. However, the pattern of rainfalls around the marine-continental tropicalwestern Pacific region over the last millennium remains unclear. Several recent studiessuggest a southward migration of the Intertropical Convergence <span class="hlt">Zone</span> during the Little <span class="hlt">Ice</span>Age (~AD 1400-1850). Concomitantly, dry Little <span class="hlt">Ice</span> Age conditions should have occurred inthe northern extent of the Intertropical Convergence <span class="hlt">Zone</span> and wet conditions around thesouthern limit. However, our synthesis of proxy hydrology records from the Asian-Australian monsoon area documents a distinctly different rainfall pattern that violates thisexpectation, suggesting instead the occurrence of synchronous retreat of the East AsianSummer Monsoon and the Australian Summer Monsoon during the Little <span class="hlt">Ice</span> Age. Thus wepropose an alternative dynamic scenario: rather than strict north-south migration, theapparent mode of multi-decadal to centennial change for the western Pacific IntertropicalConvergence <span class="hlt">Zone</span> is contraction/expansion in response to external forcings such as solarirradiance variation and large volcanic eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS11B1656S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS11B1656S"><span id="translatedtitle">Quantifying the Floe Size Distribution in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> from Satellite Imagery for use in Model Development and Validation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schweiger, A. J.; Stern, H. L.; Stark, M.; Zhang, J.; Hwang, P.; Steele, M.</p> <p>2013-12-01</p> <p>Several key processes in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> (MIZ) of the Arctic Ocean are related to the size of the <span class="hlt">ice</span> floes, whose diameters range from meters to tens of kilometers. The floe size distribution (FSD) influences mechanical properties of the <span class="hlt">ice</span> and thus its response to winds, currents, and waves, which is likely to modify the air-sea momentum transfer. The FSD also influences the air-sea heat transfer and the response of the MIZ <span class="hlt">ice</span> cover to the thermal forcing. The FSD also has a significant role in lateral melting. No existing sea-<span class="hlt">ice</span>/ocean models currently simulate the FSD in the MIZ. Significant uncertainties in FSD-related processes hinder model incorporation of the FSD, and model development must heavily depend on observations of the FSD for parameterization, calibration, and validation. To support the development and implementation of the FSD in the Marginal <span class="hlt">Ice</span> <span class="hlt">Zone</span> Modeling and Assimilation System (MIZMAS), we have conducted an analysis of the FSD in the Beaufort and Chukchi seas using three sources of satellite imagery: NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites, the Canadian Space Agency's synthetic aperture radar (SAR) on RADARSAT, and declassified National Technical Means imagery from the Global Fiducials Library (GFL) of the U.S. Geological Survey. The MODIS visible and short-wave infrared bands have a pixel size of 250 meters, and are only useful in cloud-free regions. The SAR imagery is unaffected by clouds and darkness, and has a pixel size of 50 meters. The GFL visible imagery, with a pixel size of 1 meter, is only useful in cloud-free regions. The resolution and spatial extent of the various image products allows us to identify <span class="hlt">ice</span> floes of all sizes from 10 meters to 100 kilometers. The general procedure for identifying <span class="hlt">ice</span> floes in the imagery is as follows: delineate cloud-free regions (if necessary); choose a threshold to separate <span class="hlt">ice</span> from water, and create a binary image; apply the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990042088&hterms=iceland&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Diceland','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990042088&hterms=iceland&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Diceland"><span id="translatedtitle">Analysis of Daily, <span class="hlt">Seasonal</span>, and Interannual Changes in Hofsjokull <span class="hlt">Ice</span> Cap, Iceland, using Satellite Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, D. K.; Garvin, J. B.; Williams, R. S., Jr.; Barton, J. S.; Sigurosson, O.; Smith, L. C.</p> <p>1998-01-01</p> <p>Analysis of a time series of European Remote Sensing Satellite (ERS)-1 and -2, RADARSAT ScanSAR synthetic aperture radar (SAR) and Landsat images from 1973 to 1998, shows daily to interannual changes in Hofsjokull, a 923 sq km <span class="hlt">ice</span> cap in central Iceland. A digital elevation model of Hofsjokull was constructed using interferometry, and then SAR backscatter coefficient (d) was plotted with elevation, and air temperature along a transect across the <span class="hlt">ice</span> cap. Most of the a' changes measured along the transect are caused by a change in the state (frozen or thawed) of the surficial snow or <span class="hlt">ice</span> when air temperature rises above or below about -5 to O C. <span class="hlt">Seasonal</span> (sigma)deg patterns are identified in a 4-year time series of 57 ERS-1 and -2 images. In addition, June 1997 ScanSAR images display rapid changes in brightness that are tied closely to daily meteorological events. SAR and Landsat data were also used to measure changes in the areal extent of Hofsjokull, from 1973 to 1997, and to locate (sigma)deg and reflectance boundaries that relate to the glacier facies. Late-summer 1997 (sigma)deg and reflectance boundaries agree and are coincident with the approximate location of the fim line, and the January 1998 position of the equilibrium line as determined from ERS-2 data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7687C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7687C"><span id="translatedtitle">Using pan-Arctic, springtime, surface radiation observations to quantify atmospheric preconditioning processes that impact the sea <span class="hlt">ice</span> melt <span class="hlt">season</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cox, Christopher; Uttal, Taneil; Starkweather, Sandy; Intrieri, Janet; Maturilli, Marion; Kustov, Vasily; Konopleva, Elena; Crepinsek, Sara; Long, Chuck</p> <p>2015-04-01</p> <p>Accurate, <span class="hlt">seasonal</span>-scale forecasts of sea <span class="hlt">ice</span> extent and distribution are critical for weather forecasting, transportation, the energy industry and local Arctic communities. Current forecasting methods capture an overall trend of decreasing sea <span class="hlt">ice</span> on decadal scales, but do not reliably predict inter-annual variability. Recent work using satellite observations identified a relationship between spring-time, cloud modulated, shortwave radiation, and late <span class="hlt">season</span> sea-<span class="hlt">ice</span> extent; this relationship suggested an atmospheric preconditioning process that modulates the <span class="hlt">ice</span>-albedo feedback and sets the stage for the melt <span class="hlt">season</span>. Due to a general lack of emphasis on the role of the atmosphere on the evolution of the summer sea-<span class="hlt">ice</span>, compounded by biases in cloud properties within models, this preconditioning process is poorly represented in current forecasting methods. Longwave and shortwave radiation data collected at the surface from stations surrounding the Arctic Basin as part of the Baseline Surface Radiation Network (BSRN) provide high-quality, continuous observations of the surface radiation budget. This includes downwelling fluxes and surface-cloud radiative interactions which cannot be directly acquired by satellites. These BSRN data are used to investigate the role of the atmosphere and clouds in <span class="hlt">seasonal</span> scale variability of sea <span class="hlt">ice</span> conditions, and the potential for improving predictability by incorporating these atmospheric observations into prediction strategies. We find that the downwelling fluxes measured at the land stations in spring are well correlated with sea <span class="hlt">ice</span> conditions in September, especially in regions of the Arctic Ocean where late summer sea <span class="hlt">ice</span> concentration has large inter-annual variability. Using observations of the total radiative flux (longwave + shortwave) at the surface, it is possible to make a <span class="hlt">seasonal</span> sea-<span class="hlt">ice</span> extent forecast that is within the range of uncertainty of forecasts currently incorporated into the Sea <span class="hlt">Ice</span> Prediction Network</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2011-01-10/pdf/2011-171.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2011-01-10/pdf/2011-171.pdf"><span id="translatedtitle">76 FR 1362 - Safety <span class="hlt">Zone</span>; <span class="hlt">Ice</span> Conditions for the Baltimore Captain of Port <span class="hlt">Zone</span></span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2011-01-10</p> <p>... Federal Register (73 FR 3316). Public Meeting We do not now plan to hold a public meeting. But you may... severe winter, frozen waterways present numerous hazards to vessels. <span class="hlt">Ice</span> in a waterway may hamper a... of materials, performance, design, or operation; test methods; sampling procedures; and...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4923158','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4923158"><span id="translatedtitle"><span class="hlt">Seasonal</span> Variation of Carbon Metabolism in the Cambial <span class="hlt">Zone</span> of Eucalyptus grandis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Budzinski, Ilara G. F.; Moon, David H.; Lindén, Pernilla; Moritz, Thomas; Labate, Carlos A.</p> <p>2016-01-01</p> <p>Eucalyptus species are the most widely hardwood planted in the world. It is one of the successful examples of commercial forestry plantation in Brazil and other tropical and subtropical countries. The tree is valued for its rapid growth, adaptability and wood quality. Wood formation is the result of cumulative annual activity of the vascular cambium. This cambial activity is generally related to the alternation of cold and warm, and/or dry and rainy <span class="hlt">seasons</span>. Efforts have focused on analysis of cambial <span class="hlt">zone</span> in response to <span class="hlt">seasonal</span> variations in trees from temperate <span class="hlt">zones</span>. However, little is known about the molecular changes triggered by <span class="hlt">seasonal</span> variations in trees from tropical countries. In this work we attempted to establish a global view of <span class="hlt">seasonal</span> alterations in the cambial <span class="hlt">zone</span> of Eucalyptus grandis Hill ex Maiden, emphasizing changes occurring in the carbon metabolism. Using transcripts, proteomics and metabolomics we analyzed the tissues harvested in summer-wet and winter-dry <span class="hlt">seasons</span>. Based on proteomics analysis, 70 proteins that changed in abundance were successfully identified. Transcripts for some of these proteins were analyzed and similar expression patterns were observed. We identified 19 metabolites differentially abundant. Our results suggest a differential reconfiguration of carbon partioning in E. grandis cambial <span class="hlt">zone</span>. During summer, pyruvate is primarily metabolized via ethanolic fermentation, possibly to regenerate NAD+ for glycolytic ATP production and cellular maintenance. However, in winter there seems to be a metabolic change and we found that some sugars were highly abundant. Our results revealed a dynamic change in E. grandis cambial <span class="hlt">zone</span> due to <span class="hlt">seasonality</span> and highlight the importance of glycolysis and ethanolic fermentation for energy generation and maintenance in Eucalyptus, a fast growing tree. PMID:27446160</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><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_13");'>»</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_9");'>9</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><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</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://www.ncbi.nlm.nih.gov/pubmed/27446160','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27446160"><span id="translatedtitle"><span class="hlt">Seasonal</span> Variation of Carbon Metabolism in the Cambial <span class="hlt">Zone</span> of Eucalyptus grandis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Budzinski, Ilara G F; Moon, David H; Lindén, Pernilla; Moritz, Thomas; Labate, Carlos A</p> <p>2016-01-01</p> <p>Eucalyptus species are the most widely hardwood planted in the world. It is one of the successful examples of commercial forestry plantation in Brazil and other tropical and subtropical countries. The tree is valued for its rapid growth, adaptability and wood quality. Wood formation is the result of cumulative annual activity of the vascular cambium. This cambial activity is generally related to the alternation of cold and warm, and/or dry and rainy <span class="hlt">seasons</span>. Efforts have focused on analysis of cambial <span class="hlt">zone</span> in response to <span class="hlt">seasonal</span> variations in trees from temperate <span class="hlt">zones</span>. However, little is known about the molecular changes triggered by <span class="hlt">seasonal</span> variations in trees from tropical countries. In this work we attempted to establish a global view of <span class="hlt">seasonal</span> alterations in the cambial <span class="hlt">zone</span> of Eucalyptus grandis Hill ex Maiden, emphasizing changes occurring in the carbon metabolism. Using transcripts, proteomics and metabolomics we analyzed the tissues harvested in summer-wet and winter-dry <span class="hlt">seasons</span>. Based on proteomics analysis, 70 proteins that changed in abundance were successfully identified. Transcripts for some of these proteins were analyzed and similar expression patterns were observed. We identified 19 metabolites differentially abundant. Our results suggest a differential reconfiguration of carbon partioning in E. grandis cambial <span class="hlt">zone</span>. During summer, pyruvate is primarily metabolized via ethanolic fermentation, possibly to regenerate NAD(+) for glycolytic ATP production and cellular maintenance. However, in winter there seems to be a metabolic change and we found that some sugars were highly abundant. Our results revealed a dynamic change in E. grandis cambial <span class="hlt">zone</span> due to <span class="hlt">seasonality</span> and highlight the importance of glycolysis and ethanolic fermentation for energy generation and maintenance in Eucalyptus, a fast growing tree. PMID:27446160</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ClDy...37.2107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ClDy...37.2107S"><span id="translatedtitle">Snow precipitation at four <span class="hlt">ice</span> core sites in East Antarctica: provenance, <span class="hlt">seasonality</span> and blocking factors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scarchilli, Claudio; Frezzotti, Massimo; Ruti, Paolo Michele</p> <p>2011-11-01</p> <p>Snow precipitation is the primary mass input to the Antarctic <span class="hlt">ice</span> sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from <span class="hlt">ice</span> cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep <span class="hlt">ice</span> core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the <span class="hlt">ice</span> sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), <span class="hlt">seasonality</span> (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low (>10 days) and high (2-6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60-70°S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015BGD....12.1975M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015BGD....12.1975M&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Seasonal</span> dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost <span class="hlt">zone</span> of western Siberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manasypov, R. M.; Vorobyev, S. N.; Loiko, S. V.; Kritzkov, I. V.; Shirokova, L. S.; Shevchenko, V. P.; Kirpotin, S. N.; Kulizhsky, S. P.; Kolesnichenko, L. G.; Zemtzov, V. A.; Sinkinov, V. V.; Pokrovsky, O. S.</p> <p>2015-01-01</p> <p>Western Siberia's thermokarst (thaw) lakes extend over a territory spanning over a million km2; they are highly dynamic hydrochemical systems that receive chemical elements from the atmosphere and surrounding peat soil and vegetation, and exchange greenhouse gases with the atmosphere, delivering dissolved carbon and metals to adjacent hydrological systems. This work describes the chemical composition of ~ 130 thermokarst lakes of the size range from a few m2 to several km2, located in the discontinuous permafrost <span class="hlt">zone</span>. Lakes were sampled during spring floods, just after the <span class="hlt">ice</span> break (early June), the end of summer (August), the beginning of <span class="hlt">ice</span> formation (October) and during the full freezing <span class="hlt">season</span> in winter (February). Dissolved organic carbon (DOC) and the major and trace elements do not appreciably change their concentration with the lake size increase above 1000 m2 during all <span class="hlt">seasons</span>. On the annual scale, the majority of dissolved elements including organic carbon increase their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The maximal increase in trace element (TE) concentration occurred between spring and summer and autumn and winter. The <span class="hlt">ice</span> formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the <span class="hlt">ice</span> surface. This water was subsequently frozen and formed layered <span class="hlt">ice</span> rich in organic matter. As a result, the DOC and metal concentrations were the highest at the beginning of the <span class="hlt">ice</span> column and decreased from the surface to the depth. A number of elements demonstrated the accumulation, by more than a factor of 2, in the surface (0-20 cm) of the <span class="hlt">ice</span> column relative to the rest of the <span class="hlt">ice</span> core: Mn, Fe, Ni, Cu, Zn, As, Ba and Pb. The main consequences of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and the removal of dissolved</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011Ocgy...51..295S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011Ocgy...51..295S"><span id="translatedtitle">The inhabitants of the spring <span class="hlt">ice</span>, under-<span class="hlt">ice</span> water, and sediments of the white sea in the estuarine <span class="hlt">zone</span> of the Severnaya Dvina River</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sazhin, A. F.; Sapozhnikov, F. V.; Rat'kova, T. N.; Romanova, N. D.; Shevchenko, V. P.; Filippov, A. S.</p> <p>2011-04-01</p> <p>The data on the supra-<span class="hlt">ice</span> snow, <span class="hlt">ice</span>, under-<span class="hlt">ice</span> water, and benthic algal flora obtained in 2007-2008 by sampling in the estuary of the Severnaya Dvina River are analyzed. The river <span class="hlt">ice</span> and under-<span class="hlt">ice</span> water in the estuarine <span class="hlt">zone</span> and in the channel part of the Severnaya Dvina differed greatly in the algal flora's composition. The fresh water species never exceeded 8.6%, while the <span class="hlt">ice</span> algae composed 90-96% of the total <span class="hlt">ice</span> inhabitants' biomass. In the under-<span class="hlt">ice</span> water, this value did not exceed 58-64%. The bacteria in the <span class="hlt">ice</span> composed not more than 2.5-10% of the total biomass, while, in the under-<span class="hlt">ice</span> water, 36-49%. The shares of ciliates (0.04%) and nematodes (0.005-1.6%) in the total biomass were negligible. In the estuarine <span class="hlt">zone</span>, the <span class="hlt">ice</span> was inhabited mainly by nematodes (78% of the total biomass), while, in the river, their share decreased to 9%. The contribution of bacteria was 15% in Dvina Bay and increased to 61% in the river. The importance of algae in the snow was minor: 7% of the total biomass in the marine <span class="hlt">zone</span> and 30% in the river region. High species diversity of the algal flora in the sandy and sandy-silty littoral grounds was revealed. The values of the total biomass of the bottom algal flora (0.38 g C/m2) were only two to three times lower than the values revealed in similar habitats in the summer. The epipelithic forms (0.15 g C/m2) dominated, being represented by 46 species of algae (49%). The shares of epipsammonic (0.12 g C/m2) and planktonic (0.11 g C/m2) species were almost equal to each other: 25 and 22 species, respectively (27 and 24%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=225938','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=225938"><span id="translatedtitle">Forage Systems for the Upper Transition <span class="hlt">Zone</span> that Utilize Bermudagrass and Cool-<span class="hlt">Season</span> Annual Grasses</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Bermudagrass [Cynodon dactylon (L.) Pers.] cultivars are commercially available that have the cold hardiness to persist in the colder climate of the upper transition <span class="hlt">zone</span>. The grass has a short growing <span class="hlt">season</span> of 4 to 5 months in the region, which requires that pastures be over-seeded with cool-seaso...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016cosp...41E1894T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016cosp...41E1894T&link_type=ABSTRACT"><span id="translatedtitle">Meso- and submesoscale structures in marginal <span class="hlt">ice</span> <span class="hlt">zone</span> in Arctic ocean using 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>Tarasenko, Anastasiia</p> <p>2016-07-01</p> <p>A marginal sea <span class="hlt">ice</span> <span class="hlt">zone</span> is a region where ocean currents interact with the sea <span class="hlt">ice</span>. Recently freezed small sea <span class="hlt">ice</span> particles (frazil) can be used as a passive tracer for the ocean surface dynamics studies. Sentinel-1 SAR images with a high spatial resolution (40 or 25 m) permit to exploit this approach of "frazil as surface current's passive tracer". A preliminary research on meso- and submesoscale structures in marginal sea <span class="hlt">ice</span> <span class="hlt">zone</span> was carried out using Sentinel-1 SAR data. A new dataset of mesoscale structures was created for Eastern Greenland, Barents and Kara seas for 2014-2015. The raw data was processed with SNAP (Sentinel application Platform designed by ESA). A classical method of maximum cross-correlation was tested together with a method developed based on (Kudriavtsev et al, 2014) for eddy-like structures detection. References: Kudryavtsev, Vladimir, I. Kozlov, Bertrand Chapron, and J. A. Johannessen. "Quad-polarization SAR features of ocean currents." Journal of Geophysical Research: Oceans 119, no. 9 (2014): 6046-6065.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1817421J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1817421J&link_type=ABSTRACT"><span id="translatedtitle">Influence of <span class="hlt">ice</span> sheet bed morphology on spatial and <span class="hlt">seasonal</span> patterns of <span class="hlt">ice</span> flow in Greenland: preliminary results from an automated method for interpreting high resolution <span class="hlt">ice</span> velocity data derived from Landsat imagery.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, Andrew H.; Swift, Darrel A.; Livingstone, Stephen J.</p> <p>2016-04-01</p> <p><span class="hlt">Ice</span> sheet bed morphology affects <span class="hlt">ice</span> flow rates and patterns by topographically directing and resisting <span class="hlt">ice</span> flow and by modulating rates of basal sliding. Notably, reverse bedslopes are anticipated to modulate basal sliding rates and mechanisms through their control on subglacial drainage system morphology and efficiency. In <span class="hlt">ice</span> sheet contexts, understanding of the significance of these controls, their relative importance and ubiquity, remains weak. We aim to use contemporary remote sensing data products that provide high spatial and temporal resolution <span class="hlt">ice</span> velocity and bed data for the Greenland <span class="hlt">ice</span> sheet to attempt a comprehensive and systematic analysis of spatial and <span class="hlt">seasonal</span> variation in flow behaviour and its links to bed morphology. Here we present an automated method for high resolution 4-dimensional analysis of a large archive dataset (Rosenau et al, 2015) of Landsat-derived <span class="hlt">ice</span> velocity that enables the extraction of velocity data along a large number of longitudinal flowlines for individual glacier catchments and the analysis of along-flow velocity patterns. Analysis can be undertaken on individual flowlines, or adjacent flowlines can be custom aggregated both spatially and temporarily to investigate factors such as intra-annual or inter-annual <span class="hlt">seasonal</span> patterns. We present initial analyses of <span class="hlt">seasonal</span> velocity changes at a sample of glacier catchments and their relationship to glacier bed characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC22C..04W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC22C..04W"><span id="translatedtitle">Greenland <span class="hlt">Ice</span> Sheet delivers <span class="hlt">seasonally</span> elevated nitrogen fluxes to the Arctic oceans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wadham, J. L.; Hawkings, J.; Telling, J.; Chandler, D.; Alcock, J.; Lawson, E.; Monteiro, F. M.; Kaur, P.; Bagshaw, E.; Tranter, M.; Tedstone, A. J.; Nienow, P. W.</p> <p>2013-12-01</p> <p>The availability of nitrogen limits the productivity of phytoplankton over almost half of the world's oceans in the summer months. This includes many of the ocean basins around the Greenland <span class="hlt">Ice</span> Sheet (GrIS). Here, nitrogen is widely limiting in comparison to other nutrients such as phosphorus, silica and iron, which show only local limitation. Marine waters bordering the GrIS include some of the most productive ecosystems in the world, and boast high socio-economic value via fisheries. The productivity of phytoplankton in the North Atlantic also draws down CO2 from the atmosphere and has an important regulatory effect on global climate. The GrIS has recently begun to be considered as a source of nutrients to neighbouring oceans, but detailed studies of nitrogen fluxes in exported meltwater and icebergs from large catchments are lacking. Here, we present data from a large land-terminating glacier in Western Greenland during the 2012 melt <span class="hlt">season</span>, inferring fluxes, speciation and sources of nitrogen exported in the runoff. We present <span class="hlt">seasonal</span> time series of the concentrations of dissolved and sediment-bound nitrogen species in meltwaters both entering the glacial drainage system via moulins and exported runoff at the <span class="hlt">ice</span> margin. A comparison of these data indicate that dissolved nitrogen concentrations in meltwaters approximately double during transit through the supra- and subglacial drainage systems, largely via the acquisition of dissolved organic nitrogen, which is likely to be associated with microbial activity. We go on to estimate nitrogen fluxes from the GrIS and show that fluxes are of a similar order of magnitude to some of the largest Arctic rivers in summer. Glacial nitrogen fluxes increase with rising runoff volumes, and hence with the progression of the melt <span class="hlt">season</span>. This is significant given the reported nitrogen limitation of marine phytoplankton in some coastal waters around the GrIS in mid-summer following the spring phytoplankton bloom. We discuss</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title33-vol2/pdf/CFR-2012-title33-vol2-sec165-T08-0240.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title33-vol2/pdf/CFR-2012-title33-vol2-sec165-T08-0240.pdf"><span id="translatedtitle">33 CFR 165.T08-0240 - Safety <span class="hlt">Zone</span>; Kemah Boardwalk Summer <span class="hlt">Season</span> Fireworks, Galveston Bay, Kemah, TX.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-07-01</p> <p>... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Safety <span class="hlt">Zone</span>; Kemah Boardwalk Summer <span class="hlt">Season</span> Fireworks, Galveston Bay, Kemah, TX. 165.T08-0240 Section 165.T08-0240 Navigation and... Areas Eighth Coast Guard District § 165.T08-0240 Safety <span class="hlt">Zone</span>; Kemah Boardwalk Summer <span class="hlt">Season</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1526609E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1526609E"><span id="translatedtitle">Observations of surface momentum exchange over the marginal-<span class="hlt">ice-zone</span> and recommendations for its parameterization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elvidge, A. D.; Renfrew, I. A.; Weiss, A. I.; Brooks, I. M.; Lachlan-Cope, T. A.; King, J. C.</p> <p>2015-10-01</p> <p>Comprehensive aircraft observations are used to characterise surface roughness over the Arctic marginal <span class="hlt">ice</span> <span class="hlt">zone</span> (MIZ) and consequently make recommendations for the parameterization of surface momentum exchange in the MIZ. These observations were gathered in the Barents Sea and Fram Strait from two aircraft as part of the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) project. They represent a doubling of the total number of such aircraft observations currently available over the Arctic MIZ. The eddy covariance method is used to derive estimates of the 10 m neutral drag coefficient (CDN10) from turbulent wind velocity measurements, and a novel method using albedo and surface temperature is employed to derive <span class="hlt">ice</span> fraction. Peak surface roughness is found at <span class="hlt">ice</span> fractions in the range 0.6 to 0.8 (with a mean interquartile range in CDN10 of 1.25 to 2.85 × 10-3). CDN10 as a function of <span class="hlt">ice</span> fraction is found to be well approximated by the negatively skewed distribution provided by a leading parameterization scheme (Lüpkes et al., 2012) tailored for sea <span class="hlt">ice</span> drag over the MIZ in which the two constituent components of drag - skin and form drag - are separately quantified. Current parameterization schemes used in the weather and climate models are compared with our results and the majority are found to be physically unjustified and unrepresentative. The Lüpkes et al. (2012) scheme is recommended in a computationally simple form, with adjusted parameter settings. A good agreement is found to hold for subsets of the data from different locations despite differences in sea <span class="hlt">ice</span> conditions. <span class="hlt">Ice</span> conditions in the Barents Sea, characterised by small, unconsolidated <span class="hlt">ice</span> floes, are found to be associated with higher CDN10 values - especially at the higher <span class="hlt">ice</span> fractions - than those of Fram Strait, where typically larger, smoother floes are observed. Consequently, the important influence of sea <span class="hlt">ice</span> morphology and floe size on surface roughness is</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><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_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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