Observation of wave refraction at an ice edge by synthetic aperture radar

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Vachon, Paris W.; Peng, Chih Y.

1991-01-01

In this note the refraction of waves at the ice edge is studied by using aircraft synthesis aperture radar (SAR). Penetration of a dominant swell from open ocean into the ice cover was observed by SAR during the Labrador Ice Margin Experiment (LIMEX), conducted on the marginal ice zone (MIZ) off the east coast of Newfoundland, Canada, in March 1987. At an ice edge with a large curvature, the dominant swell component disappeared locally in the SAR imagery. Six subscenes of waves in the MIZ from the SAR image have been processed, revealing total reflection, refraction, and energy reduction of the ocean waves by the ice cover. The observed variations of wave spectra from SAR near the ice edge are consistent with the model prediction of wave refraction at the ice edge due to the change of wave dispersion relation in ice developed by Liu and Mollo-Christensen (1988).

Under the Sea Ice: Exploration of the Relationships Between Sea Ice Patterns and Foraging Movements of a Marine Predator in East Antarctica.

NASA Astrophysics Data System (ADS)

Labrousse, S.; Sallee, J. B.; Fraser, A. D.; Massom, R. A.; Reid, P.; Sumner, M.; Guinet, C.; Harcourt, R.; Bailleul, F.; Hindell, M.; Charrassin, J. B.

2016-02-01

Investigating ecological relationships between top predators and their environment is essential to understand the response of marine ecosystems to climate variability. Specifically, variability and changes in sea ice, which is known as an important habitat for marine ecosystems, presents complex patterns in East Antarctic. The impact for ecosystems of such changes of their habitat is however still unknown. Acting as an ecological double-edged sword, sea ice can impede access to marine resources while harboring a rich ecosystem during winter. Here, we investigated which type of sea ice habitat is used by male and female southern elephant seals during winter and examine if and how the spatio-temporal variability of sea ice concentration (SIC) influence their foraging strategies. We also examined over a 10 years time-series the impact of SIC and sea ice advance anomaly on foraging activity. To do this, we studied 46 individuals equipped with Satellite linked data recorders between 2004 and 2014, undertaking post-moult trips in winter from Kerguelen to the peri-Antarctic shelf. The general patterns of sea ice use by males and females are clearly distinct; while females tended to follow the sea ice edge as it extended northward, males remained on the continental shelf. Female foraging activity was higher in late autumn in the outer part of the pack ice in concentrated SIC and spatially stable. They remained in areas of variable SIC over time and low persistence. The seal hunting time, a proxy of foraging activity inferred from the diving behaviour, was much higher during earlier advance of sea ice over female time-series. The females were possibly taking advantage of the ice algal autumn bloom sustaining krill and an under ice ecosystem without being trapped in sea ice. Males foraging activity increased when they remained deep inside sea ice over the shelf using variable SIC in time and space, presumably in polynyas or flaw leads between fast and pack ice. This strategy probably gave them access to zones of enhanced resources in early spring such as polynyas, the Antarctic Slope Front, or the Antarctic shelf while avoiding the constraint of sea ice. Over years, males foraging activity were not affected by anomalies of sea ice advance, however negative SIC anomalies were profitable allowing them to use remote areas within sea ice.

Statistical Analysis of SSMIS Sea Ice Concentration Threshold at the Arctic Sea Ice Edge during Summer Based on MODIS and Ship-Based Observational Data.

PubMed

Ji, Qing; Li, Fei; Pang, Xiaoping; Luo, Cong

2018-04-05

The threshold of sea ice concentration (SIC) is the basis for accurately calculating sea ice extent based on passive microwave (PM) remote sensing data. However, the PM SIC threshold at the sea ice edge used in previous studies and released sea ice products has not always been consistent. To explore the representable value of the PM SIC threshold corresponding on average to the position of the Arctic sea ice edge during summer in recent years, we extracted sea ice edge boundaries from the Moderate-resolution Imaging Spectroradiometer (MODIS) sea ice product (MOD29 with a spatial resolution of 1 km), MODIS images (250 m), and sea ice ship-based observation points (1 km) during the fifth (CHINARE-2012) and sixth (CHINARE-2014) Chinese National Arctic Research Expeditions, and made an overlay and comparison analysis with PM SIC derived from Special Sensor Microwave Imager Sounder (SSMIS, with a spatial resolution of 25 km) in the summer of 2012 and 2014. Results showed that the average SSMIS SIC threshold at the Arctic sea ice edge based on ice-water boundary lines extracted from MOD29 was 33%, which was higher than that of the commonly used 15% discriminant threshold. The average SIC threshold at sea ice edge based on ice-water boundary lines extracted by visual interpretation from four scenes of the MODIS image was 35% when compared to the average value of 36% from the MOD29 extracted ice edge pixels for the same days. The average SIC of 31% at the sea ice edge points extracted from ship-based observations also confirmed that choosing around 30% as the SIC threshold during summer is recommended for sea ice extent calculations based on SSMIS PM data. These results can provide a reference for further studying the variation of sea ice under the rapidly changing Arctic.

Studies of the Antarctic Sea Ice Edges and Ice Extents from Satellite and Ship Observations

NASA Technical Reports Server (NTRS)

Worby, Anthony P.; Comiso, Josefino C.

2003-01-01

Passive-microwave derived ice edge locations in Antarctica are assessed against other satellite data as well as in situ observations of ice edge location made between 1989 and 2000. The passive microwave data generally agree with satellite and ship data but the ice concentration at the observed ice edge varies greatly with averages of 14% for the TEAM algorithm and 19% for the Bootstrap algorithm. The comparisons of passive microwave with the field data show that in the ice growth season (March - October) the agreement is extremely good, with r(sup 2) values of 0.9967 and 0.9797 for the Bootstrap and TEAM algorithms respectively. In the melt season however (November - February) the passive microwave ice edge is typically 1-2 degrees south of the observations due to the low concentration and saturated nature of the ice. Sensitivity studies show that these results can have significant impact on trend and mass balance studies of the sea ice cover in the Southern Ocean.

A Burst of Spring

NASA Image and Video Library

2010-03-10

In the winter a layer of carbon dioxide ice dry ice covers the north polar sand dunes as shown by NASA Mars Reconnaissance Orbiter. In the spring the sublimation of the ice going directly from ice to gas causes a host of uniquely Martian phenomena.

Do pelagic grazers benefit from sea ice? Insights from the Antarctic sea ice proxy IPSO25

NASA Astrophysics Data System (ADS)

Schmidt, Katrin; Brown, Thomas A.; Belt, Simon T.; Ireland, Louise C.; Taylor, Kyle W. R.; Thorpe, Sally E.; Ward, Peter; Atkinson, Angus

2018-04-01

Sea ice affects primary production in polar regions in multiple ways. It can dampen water column productivity by reducing light or nutrient supply, provide a habitat for ice algae and condition the marginal ice zone (MIZ) for phytoplankton blooms on its seasonal retreat. The relative importance of three different carbon sources (sea ice derived, sea ice conditioned, non-sea-ice associated) for the polar food web is not well understood, partly due to the lack of methods that enable their unambiguous distinction. Here we analysed two highly branched isoprenoid (HBI) biomarkers to trace sea-ice-derived and sea-ice-conditioned carbon in Antarctic krill (Euphausia superba) and relate their concentrations to the grazers' body reserves, growth and recruitment. During our sampling in January-February 2003, the proxy for sea ice diatoms (a di-unsaturated HBI termed IPSO25, δ13C = -12.5 ± 3.3 ‰) occurred in open waters of the western Scotia Sea, where seasonal ice retreat was slow. In suspended matter from surface waters, IPSO25 was present at a few stations close to the ice edge, but in krill the marker was widespread. Even at stations that had been ice-free for several weeks, IPSO25 was found in krill stomachs, suggesting that they gathered the ice-derived algae from below the upper mixed layer. Peak abundances of the proxy for MIZ diatoms (a tri-unsaturated HBI termed HBI III, δ13C = -42.2 ± 2.4 ‰) occurred in regions of fast sea ice retreat and persistent salinity-driven stratification in the eastern Scotia Sea. Krill sampled in the area defined by the ice edge bloom likewise contained high amounts of HBI III. As indicators for the grazer's performance we used the mass-length ratio, size of digestive gland and growth rate for krill, and recruitment for the biomass-dominant calanoid copepods Calanoides acutus and Calanus propinquus. These indices consistently point to blooms in the MIZ as an important feeding ground for pelagic grazers. Even though ice-conditioned blooms are of much shorter duration than blooms downstream of the permanently sea-ice-free South Georgia, they enabled fast growth and offspring development. Our study shows two rarely considered ways that pelagic grazers may benefit from sea ice: firstly, after their release from sea ice, suspended or sinking ice algae can supplement the grazers' diet if phytoplankton concentrations are low. Secondly, conditioning effects of seasonal sea ice can promote pelagic primary production and therefore food availability in spring and summer.

The Timing of Arctic Sea Ice Advance and Retreat as an Indicator of Ice-Dependent Marine Mammal Habitat

NASA Astrophysics Data System (ADS)

Stern, H. L.; Laidre, K. L.

2013-12-01

The Arctic is widely recognized as the front line of climate change. Arctic air temperature is rising at twice the global average rate, and the sea-ice cover is shrinking and thinning, with total disappearance of summer sea ice projected to occur in a matter of decades. Arctic marine mammals such as polar bears, seals, walruses, belugas, narwhals, and bowhead whales depend on the sea-ice cover as an integral part of their existence. While the downward trend in sea-ice extent in a given month is an often-used metric for quantifying physical changes in the ice cover, it is not the most relevant measure for characterizing changes in the sea-ice habitat of marine mammals. Species that depend on sea ice are behaviorally tied to the annual retreat of sea ice in the spring and advance in the fall. Changes in the timing of the spring retreat and the fall advance are more relevant to Arctic marine species than changes in the areal sea-ice coverage in a particular month of the year. Many ecologically important regions of the Arctic are essentially ice-covered in winter and ice-free in summer, and will probably remain so for a long time into the future. But the dates of sea-ice retreat in spring and advance in fall are key indicators of climate change for ice-dependent marine mammals. We use daily sea-ice concentration data derived from satellite passive microwave sensors to calculate the dates of sea-ice retreat in spring and advance in fall in 12 regions of the Arctic for each year from 1979 through 2013. The regions include the peripheral seas around the Arctic Ocean (Beaufort, Chukchi, East Siberian, Laptev, Kara, Barents), the Canadian Arctic Archipelago, and the marginal seas (Okhotsk, Bering, East Greenland, Baffin Bay, Hudson Bay). We find that in 11 of the 12 regions (all except the Bering Sea), sea ice is retreating earlier in spring and advancing later in fall. Rates of spring retreat range from -5 to -8 days/decade, and rates of fall advance range from +5 to +9 days/decade, with steeper trends in the Barents Sea. Thus the season of sparse sea-ice coverage is lengthening by about 2 weeks/decade, or 6 weeks over the period of record. The trends in all 11 regions are statistically significant. The dates of sea-ice retreat in spring and advance in fall are negatively correlated: an early spring retreat tends to be followed by a late fall advance, and vice-versa. This is a manifestation of the ice-albedo feedback: with an early sea-ice retreat, the ocean has more time to absorb heat from the sun. The extra heat is stored in the upper ocean through the summer, and must be released to the atmosphere in the fall before sea ice can begin to form, thus delaying fall freeze-up. This relationship gives some predictive power to the date of fall sea-ice advance, given the date of spring retreat. Changes have been reported in the seasonal distribution of polar bears, walruses, seals, and whales in the Arctic. We are developing metrics for potential use by the U.S. National Climate Assessment based on the timing of sea-ice advance and retreat, to be used as indicators of ice-dependent marine mammal habitat. Future work will examine connections between the phenology of Arctic marine mammals and the sea-ice indicators.

La calotta polare sud di Mars

NASA Astrophysics Data System (ADS)

di Giovanni, Giovanni

2006-06-01

The paper discusses the variations in the ice-retreat rate of the south polar cap of Mars in springtime during the 2003 and 2005 apparitions. For this we have measured the planetocentric cap amplitude on images of the Mars Sections of the Italian Union of Amateur Astronomers (UAI), the American Association of Lunar and Planetary Observers (ALPO) and ALPO Japan in the relevant Internet sites. A reasonable first approach to the problem was to perform a simple heat-balance model of Mars' ice cap including solar insolation, surface thermal emission, condensation and sublimation of carbon dioxide frost. The model doesn't include several important physical conditions, such as atmospherical absorption of radiation etc. and other components of ice (i.e. dust, H2O etc.). A suitable mathematical continue function θ(Ls) concerning the planetocentric amplitude of the cap as a function of the areocentric solar longitude on Mars (Ls) has been used to fit the experimental points in a classical diagram cap amplitude versus Ls. The correlation coefficient resulted 0.95. The second derivative of the function (d2θ/dLs2) suggests the existence of three important points during the spring recession: a) at Ls≍228° the highest sublimation rate is observe; b) at Ls≍245° (near perihelion) the highest retraction speed of the edge cap occurs, when the solar radiation flux over the south pole exceeds the flux over the equatorial zone; c) at Ls>285° the retraction speed of the cap's edge is constant. With the same function θ(Ls) we have worked out the ice thickness for every degrees in Ls, sublimation diurnal rate and total mass of seasonal cap. The ring of ice around to the pole, whose existence was suggested by Cross, was not revealed.

Antarctic krill under sea ice: elevated abundance in a narrow band just south of ice edge.

PubMed

Brierley, Andrew S; Fernandes, Paul G; Brandon, Mark A; Armstrong, Frederick; Millard, Nicholas W; McPhail, Steven D; Stevenson, Peter; Pebody, Miles; Perrett, James; Squires, Mark; Bone, Douglas G; Griffiths, Gwyn

2002-03-08

We surveyed Antarctic krill (Euphausia superba) under sea ice using the autonomous underwater vehicle Autosub-2. Krill were concentrated within a band under ice between 1 and 13 kilometers south of the ice edge. Within this band, krill densities were fivefold greater than that of open water. The under-ice environment has long been considered an important habitat for krill, but sampling difficulties have previously prevented direct observations under ice over the scale necessary for robust krill density estimation. Autosub-2 enabled us to make continuous high-resolution measurements of krill density under ice reaching 27 kilometers beyond the ice edge.

MGS TES observations of the water vapor above the seasonal and perennial ice caps during northern spring and summer

NASA Astrophysics Data System (ADS)

Pankine, Alexey A.; Tamppari, Leslie K.; Smith, Michael D.

2010-11-01

We report on new retrievals of water vapor column abundances from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data. The new retrievals are from the TES nadir data taken above the 'cold' surface areas in the North polar region ( Tsurf < 220 K, including seasonal frost and permanent ice cap) during spring and summer seasons, where retrievals were not performed initially. Retrievals are possible (with some modifications to the original algorithm) over cold surfaces overlaid by sufficiently warm atmosphere. The retrieved water vapor column abundances are compared to the column abundances observed by other spacecrafts in the Northern polar region during spring and summer and good agreement is found. We detect an annulus of water vapor growing above the edge of the retreating seasonal cap during spring. The formation of the vapor annulus is consistent with the previously proposed mechanism for water cycling in the polar region, according to which vapor released by frost sublimation during spring re-condenses on the retreating seasonal CO 2 cap. The source of the vapor in the vapor annulus, according to this model, is the water frost on the surface of the CO 2 at the retreating edge of the cap and the frost on the ground that is exposed by the retreating cap. Small contribution from regolith sources is possible too, but cannot be quantified based on the TES vapor data alone. Water vapor annulus exhibits interannual variability, which we attribute to variations in the atmospheric temperature. We propose that during spring and summer the water ice sublimation is retarded by high relative humidity of the local atmosphere, and that higher atmospheric temperatures lead to higher vapor column abundances by increasing the water holding capacity of the atmosphere. Since the atmospheric temperatures are strongly influenced by the atmospheric dust content, local dust storms may be controlling the release of vapor into the polar atmosphere. Water vapor abundances above the residual polar cap also exhibit noticeable interannual variability. In some years abundances above the cap are lower than the abundances outside of the cap, consistent with previous observations, while in the other years the abundances above the cap are higher or similar to abundances outside of the cap. We speculate that the differences may be due to weaker off-cap transport in the latter case, keeping more vapor closer to the source at the surface of the residual cap. Despite the large observed variability in water vapor column abundances in the Northern polar region during spring and summer, the latitudinal distribution of the vapor mass in the atmosphere is very similar during the summer season. If the variability in vapor abundances is caused by the variability of vapor sources across the residual cap then this would mean that they annually contribute relatively little vapor mass to significantly affect the vapor mass budget. Alternatively this may suggest that the vapor variability is caused by the variability of the polar atmospheric circulation. The new water vapor retrievals should be useful in tuning the Global Circulation Models of the martian water cycle.

Net community production in the bottom of first-year sea ice over the Arctic spring bloom

NASA Astrophysics Data System (ADS)

Campbell, K.; Mundy, C. J.; Gosselin, M.; Landy, J. C.; Delaforge, A.; Rysgaard, S.

2017-09-01

The balance of photosynthesis and respiration by organisms like algae and bacteria determines whether sea ice is net heterotrophic or autotrophic. In turn this clarifies the influence of microbes on atmosphere-ice-ocean gas fluxes and their contribution to the trophic system. In this study we define two phases of the spring bloom based on bottom ice net community production and algal growth. Phase I was characterized by limited algal accumulation and low productivity, which at times resulted in net heterotrophy. Greater productivity in Phase II drove rapid algal accumulation that consistently produced net autotrophic conditions. The different phases were associated with seasonal shifts in light availability and species dominance. Results from this study demonstrate the importance of community respiration on spring productivity, as respiration rates can maintain a heterotrophic state independent of algal growth. This challenges previous assumptions of a fully autotrophic sea ice community during the ice-covered spring.

Primary productivity of the Palmer Long Term Ecological Research Area and the Southern Ocean

NASA Astrophysics Data System (ADS)

Smith, R. C.; Baker, K. S.; Byers, M. L.; Stammerjohn, S. E.

1998-11-01

A major objective of the Palmer Long Term Ecological Research (Palmer LTER) project is to obtain a comprehensive understanding of the various components of the Antarctic marine ecosystem. Phytoplankton production plays a key role in this so-called high nutrient, low chlorophyll environment, and factors that regulate production include those that control cell growth (light, temperature, and nutrients) and those that control cell accumulation rate and hence population growth (water column stability, grazing, and sinking). Sea ice mediates several of these factors and frequently conditions the water column for a spring bloom which is characterized by a pulse of production restricted in both time and space. This study models the spatial and temporal variability of primary production within the Palmer LTER area west of the Antarctic Peninsula and discusses this production in the context of historical data for the Southern Ocean. Primary production for the Southern Ocean and the Palmer LTER area have been computed using both light-pigment production models [Smith, R.C., Bidigare, R.R., Prézelin, B.B., Baker, K.S., Brooks, J.M., 1987. Optical characterization of primary productivity across a coastal front. Mar. Biol. (96), 575-591; Bidigare, R.R., Smith, R.C., Baker, K.S., Marra, J., 1987. Oceanic primary production estimates from measurements of spectral irradiance and pigment concentrations. Global Biogeochem. Cycles (1), 171-186; Morel, A., Berthon, J.F., 1989. Surface pigments, algal biomass profiles and potential production of the euphotic layer—relationships reinvestigated in view of remote-sensing applications. Limnol. Oceanogr. (34), 1545-1562] and an ice edge production model [Nelson, D.M., Smith, W.O., 1986. Phytoplankton bloom dynamics of the western Ross Sea ice edge: II. Mesoscale cycling of nitrogen and silicon. Deep-Sea Res. (33), 1389-1412; Wilson, D.L., Smith, W.O., Nelson, D.M., 1986. Phytoplankton bloom dynamics of the Western Ross Sea ice edge: I. primary productivity and species-specific production. Deep-Sea Res., 33, 1375-1387; Smith, W.O., Nelson, D.M., 1986. Importance of ice edge phytoplankton production in the Southern Ocean. BioScience (36), 251-257]. Chlorophyll concentrations, total photosynthetically available radiation (PAR) and sea ice concentrations were derived from satellite data. These same parameters, in addition to hydrodynamic conditions, have also been determined from shipboard and Palmer Station observations during the LTER program. Model results are compared, sensitivity studies evaluated, and productivity of the Palmer LTER region is discussed in terms of its space time distribution, seasonal and interannual variability, and overall contribution to the marine ecology of the Southern Ocean.

Satellite microwave and in situ observations of the Weddell Sea ice cover and its marginal ice zone

NASA Technical Reports Server (NTRS)

Comiso, J. C.; Sullivan, C. W.

1986-01-01

The radiative and physical characteristics of the Weddell Sea ice cover and its marginal ice zone are analyzed using multichannel satellite passive microwave data and ship and helicopter observations obtained during the 1983 Antarctic Marine Ecosystem Research. Winter and spring brightness temperatures are examined; spatial variability in the brightness temperatures of consolidated ice in winter and spring cyclic increases and decrease in brightness temperatures of consolidated ice with an amplitude of 50 K at 37 GHz and 20 K at 18 GHz are observed. The roles of variations in air temperature and surface characteristics in the variability of spring brightness temperatures are investigated. Ice concentrations are derived using the frequency and polarization techniques, and the data are compared with the helicopter and ship observations. Temporal changes in the ice margin structure and the mass balance of fresh water and of biological features of the marginal ice zone are studied.

Predictability of the Arctic sea ice edge

NASA Astrophysics Data System (ADS)

Goessling, H. F.; Tietsche, S.; Day, J. J.; Hawkins, E.; Jung, T.

2016-02-01

Skillful sea ice forecasts from days to years ahead are becoming increasingly important for the operation and planning of human activities in the Arctic. Here we analyze the potential predictability of the Arctic sea ice edge in six climate models. We introduce the integrated ice-edge error (IIEE), a user-relevant verification metric defined as the area where the forecast and the "truth" disagree on the ice concentration being above or below 15%. The IIEE lends itself to decomposition into an absolute extent error, corresponding to the common sea ice extent error, and a misplacement error. We find that the often-neglected misplacement error makes up more than half of the climatological IIEE. In idealized forecast ensembles initialized on 1 July, the IIEE grows faster than the absolute extent error. This means that the Arctic sea ice edge is less predictable than sea ice extent, particularly in September, with implications for the potential skill of end-user relevant forecasts.

Aircraft Surveys of the Beaufort Sea Seasonal Ice Zone

NASA Astrophysics Data System (ADS)

Morison, J.

2016-02-01

The Seasonal Ice Zone Reconnaissance Surveys (SIZRS) is a program of repeated ocean, ice, and atmospheric measurements across the Beaufort-Chukchi sea seasonal sea ice zone (SIZ) utilizing US Coast Guard Arctic Domain Awareness (ADA) flights of opportunity. The SIZ is the region between maximum winter sea ice extent and minimum summer sea ice extent. As such, it contains the full range of positions of the marginal ice zone (MIZ) where sea ice interacts with open water. The increasing size and changing air-ice-ocean properties of the SIZ are central to recent reductions in Arctic sea ice extent. The changes in the interplay among the atmosphere, ice, and ocean require a systematic SIZ observational effort of coordinated atmosphere, ice, and ocean observations covering up to interannual time-scales, Therefore, every year beginning in late Spring and continuing to early Fall, SIZRS makes monthly flights across the Beaufort Sea SIZ aboard Coast Guard C-130H aircraft from USCG Air Station Kodiak dropping Aircraft eXpendable CTDs (AXCTD) and Aircraft eXpendable Current Profilers (AXCP) for profiles of ocean temperature, salinity and shear, dropsondes for atmospheric temperature, humidity, and velocity profiles, and buoys for atmosphere and upper ocean time series. Enroute measurements include IR imaging, radiometer and lidar measurements of the sea surface and cloud tops. SIZRS also cooperates with the International Arctic Buoy Program for buoy deployments and with the NOAA Earth System Research Laboratory atmospheric chemistry sampling program on board the aircraft. Since 2012, SIZRS has found that even as SIZ extent, ice character, and atmospheric forcing varies year-to-year, the pattern of ocean freshening and radiative warming south of the ice edge is consistent. The experimental approach, observations and extensions to other projects will be discussed.

Mars Global Surveyor TES Results: Observations of Water Ice Clouds

NASA Technical Reports Server (NTRS)

Pearl, John C.; Smith, M. D.; Conrath, B. J.; Bandfield, J. L.; Christensen, P. R.

1999-01-01

On July 31, 1999, Mars Global Surveyor completed its first martian year in orbit. During this time, the Thermal Emission Spectrometer (TES) experiment gathered extensive data on water ice clouds. We report here on three types of martian clouds. 1) Martian southern summer has long been characterized as the season when the most severe dust storms occur. It is now apparent that northern spring/summer is characterized as a time of substantial low latitude ice clouds [1]. TES observations beginning in the northern summer (Lsubs=107) show a well developed cloud belt between 10S and 30N latitude; 12 micron opacities were typically 0.15. This system decreased dramatically after Lsubs= 130. Thereafter, remnants were most persistent over the Tharsis ridge. 2) Clouds associated with major orographic features follow a different pattern [2]. Clouds of this type were present prior to the regional Noachis dust storm of 1997. They disappeared with the onset of the storm, but reappeared rather quickly following its decay. Typical infrared opacities were near 0.5. 3) Extensive, very thin clouds are also widespread [3]. Found at high altitudes (above 35 km), their opacities are typically a few hundredths. At times, such as in northern spring, these clouds are limited in their northern extent only by the southern edge of the polar vortex. We describe the distribution, infrared optical properties, and seasonal trends of these systems during the first martian year of TES operations.

Loitering of the retreating sea ice edge in the Arctic Seas.

PubMed

Steele, Michael; Ermold, Wendy

2015-12-01

Each year, the arctic sea ice edge retreats from its winter maximum extent through the Seasonal Ice Zone (SIZ) to its summer minimum extent. On some days, this retreat happens at a rapid pace, while on other days, parts of the pan-arctic ice edge hardly move for periods of days up to 1.5 weeks. We term this stationary behavior "ice edge loitering," and identify areas that are more prone to loitering than others. Generally, about 20-25% of the SIZ area experiences loitering, most often only one time at any one location during the retreat season, but sometimes two or more times. The main mechanism controlling loitering is an interaction between surface winds and warm sea surface temperatures in areas from which the ice has already retreated. When retreat happens early enough to allow atmospheric warming of this open water, winds that force ice floes into this water cause melting. Thus, while individual ice floes are moving, the ice edge as a whole appears to loiter. The time scale of loitering is then naturally tied to the synoptic time scale of wind forcing. Perhaps surprisingly, the area of loitering in the arctic seas has not changed over the past 25 years, even as the SIZ area has grown. This is because rapid ice retreat happens most commonly late in the summer, when atmospheric warming of open water is weak. We speculate that loitering may have profound effects on both physical and biological conditions at the ice edge during the retreat season.

Conditions leading to the unprecedented low Antarctic sea ice extent during the 2016 austral spring season

NASA Astrophysics Data System (ADS)

Stuecker, Malte F.; Bitz, Cecilia M.; Armour, Kyle C.

2017-09-01

The 2016 austral spring was characterized by the lowest Southern Hemisphere (SH) sea ice extent seen in the satellite record (1979 to present) and coincided with anomalously warm surface waters surrounding most of Antarctica. We show that two distinct processes contributed to this event: First, the extreme El Niño event peaking in December-February 2015/2016 contributed to pronounced extratropical SH sea surface temperature and sea ice extent anomalies in the eastern Ross, Amundsen, and Bellingshausen Seas that persisted in part until the following 2016 austral spring. Second, internal unforced atmospheric variability of the Southern Annular Mode promoted the exceptional low sea ice extent in November-December 2016. These results suggest that a combination of tropically forced and internal SH atmospheric variability contributed to the unprecedented sea ice decline during the 2016 austral spring, on top of a background of slow changes expected from greenhouse gas and ozone forcing.

The Effect of Break Edge Configuration on the Aerodynamics of Anti-Ice Jet Flow

NASA Astrophysics Data System (ADS)

Tatar, V.; Yildizay, H.; Aras, H.

2015-05-01

One of the components of a turboprop gas turbine engine is the Front Bearing Structure (FBS) which leads air into the compressor. FBS directly encounters with ambient air, as a consequence ice accretion may occur on its static vanes. There are several aerodynamic parameters which should be considered in the design of anti-icing system of FBS, such as diameter, position, exit angle of discharge holes, etc. This research focuses on the effects of break edge configuration over anti-ice jet flow. Break edge operation is a process which is applied to the hole in order to avoid sharp edges which cause high stress concentration. Numerical analyses and flow visualization test have been conducted. Four different break edge configurations were used for this investigation; without break edge, 0.35xD, 74xD, 0.87xD. Three mainstream flow conditions at the inlet of the channel are defined; 10m/s, 20 m/s and 40 m/s. Shear stresses are extracted from numerical analyses near the trailing edge of pressure surface where ice may occur under icing conditions. A specific flow visualization method was used for the experimental study. Vane surface near the trailing edge was dyed and thinner was injected into anti-ice jet flow in order to remove dye from the vane surface. Hence, film effect on the surface could be computed for each testing condition. Thickness of the dye removal area of each case was examined. The results show noticeable effects of break edge operation on jet flow, and the air film effectiveness decreases when mainstream inlet velocity decreases.

Circulation and water properties in the landfast ice zone of the Alaskan Beaufort Sea

NASA Astrophysics Data System (ADS)

Weingartner, Thomas J.; Danielson, Seth L.; Potter, Rachel A.; Trefry, John H.; Mahoney, Andy; Savoie, Mark; Irvine, Cayman; Sousa, Leandra

2017-09-01

Moorings, hydrography, satellite-tracked drifters, and high-frequency radar data describe the annual cycle in circulation and water properties in the landfast ice zone (LIZ) of the Alaskan Beaufort Sea. Three seasons, whose duration and characteristics are controlled by landfast ice formation and ablation, define the LIZ: ;winter;, ;break-up;, and ;open-water;. Winter begins in October with ice formation and ends in June when rivers commence discharging. Winter LIZ ice velocities are zero, under-ice currents are weak ( 5 cm s-1), and poorly correlated with winds and local sea level. The along-shore momentum balance is between along-shore pressure gradients and bottom and ice-ocean friction. Currents at the landfast ice-edge are swift ( 35 cm s-1), wind-driven, with large horizontal shears, and potentially unstable. Weak cross-shore velocities ( 1 cm s-1) imply limited exchanges between the LIZ and the outer shelf in winter. The month-long break-up season (June) begins with the spring freshet and concludes when landfast ice detaches from the bottom. Cross-shore currents increase, and the LIZ hosts shallow ( 2 m), strongly-stratified, buoyant and sediment-laden, under-ice river plumes that overlie a sharp, 1 m thick, pycnocline across which salinity increases by 30. The plume salt balance is between entrainment and cross-shore advection. Break-up is followed by the 3-month long open-water season when currents are swift (≥20 cm s-1) and predominantly wind-driven. Winter water properties are initialized by fall advection and evolve slowly due to salt rejection from ice. Fall waters and ice within the LIZ derive from local rivers, the Mackenzie and/or Chukchi shelves, and the Arctic basin.

Transient nature of Arctic spring systems driven by subglacial meltwater

NASA Astrophysics Data System (ADS)

Scheidegger, J. M.; Bense, V. F.; Grasby, S. E.

2012-06-01

In the High Arctic, supra- and proglacial springs occur at Borup Fiord Pass, Ellesmere Island. Spring waters are sulfur bearing and isotope analysis suggests springs are fed by deeply circulating glacial meltwater. However, the mechanism maintaining spring flow is unclear in these areas of thick permafrost which would hamper the discharge of deep groundwater to the surface. It has been hypothesized that fracture zones along faults focus groundwater which discharges initially underneath wet-based parts of the ice. With thinning ice, the spring head is exposed to surface temperatures, tens of degrees lower than temperatures of pressure melting, and permafrost starts to develop. Numerical modeling of coupled heat and fluid flow suggest that focused groundwater discharge should eventually be cut off by permafrost encroaching into the feeding channel of the spring. Nevertheless, our model simulations show that these springs can remain flowing for millennia depending on the initial flow rate and ambient surface temperature. These systems might provide a terrestrial analog for the possible occurrence of Martian springs recharged by polar ice caps.

Integrating expert- and algorithm-derived data to generate a hemispheric ice edge

NASA Astrophysics Data System (ADS)

Tsatsoulis, C.; Komp, E.

The Arctic ice edge is the area of the Arctic where sea ice concentration is less than 15%, and is considered navigable by most vessels. Experts at the National Ice Center generate a daily ice edge product that is available to the public. Data of preference is that of active, high resolution satellite sensors such as RADARSAT which yields all-weather images of 100m resolution, and a second source is OLS data with 550m resolution. Unfortunately, RADARSAT does not provide full, daily coverage of the Arctic and OLS can be obscured by clouds. The SSM/I sensor provides complete coverage of the Arctic at 25km resolution and is independent of cloud cover and solar illumination during the Arctic winter. SSM/I data is analyzed by the NASA Team algorithm to establish ice concentration. Our work integrates the ice edge created by experts using high resolution data with the ice edge generated out of the coarser SSM/I microwave data. The result is a product that combines human and algorithmic outputs, deals with gross differences in resolution of the underlying data sets, and results in a useful, operational product.

Wave-Ice and Air-Ice-Ocean Interaction During the Chukchi Sea Ice Edge Advance

DTIC Science & Technology

2015-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Wave -Ice and Air-Ice-Ocean Interaction During the...Chukchi Sea in the late summer have potentially changed the impact of fall storms by creating wave fields in the vicinity of the advancing ice edge. A...first) wave -ice interaction field experiment that adequately documents the relationship of a growing pancake ice cover with a time and space varying

77 FR 60651 - Airworthiness Directives; BAE Systems (Operations) Limited Airplanes

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2012-10-04

... of the wing leading edge. This proposed AD would require a detailed inspection of the end caps on the... tube, and ice accretion on the wing leading edge or run-back ice, which could lead to a reduction in... leading edge anti- icing piccolo tube end caps on two aircraft. This was discovered during routine zonal...

78 FR 7259 - Airworthiness Directives; BAE SYSTEMS (OPERATIONS) LIMITED Airplanes

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2013-02-01

... wing leading edge. This AD requires a detailed inspection of the end caps on the anti-icing piccolo... on the wing leading edge or run-back ice, which could lead to a reduction in the stall margin on... the loss of the wing leading edge anti- icing piccolo tube end caps on two aircraft. This was...

Bacterial communities in Arctic first-year drift ice during the winter/spring transition.

PubMed

Eronen-Rasimus, Eeva; Piiparinen, Jonna; Karkman, Antti; Lyra, Christina; Gerland, Sebastian; Kaartokallio, Hermanni

2016-08-01

Horizontal and vertical variability of first-year drift-ice bacterial communities was investigated along a North-South transect in the Fram Strait during the winter/spring transition. Two different developmental stages were captured along the transect based on the prevailing environmental conditions and the differences in bacterial community composition. The differences in the bacterial communities were likely driven by the changes in sea-ice algal biomass (2.6-5.6 fold differences in chl-a concentrations). Copiotrophic genera common in late spring/summer sea ice, such as Polaribacter, Octadecabacter and Glaciecola, dominated the bacterial communities, supporting the conclusion that the increase in the sea-ice algal biomass was possibly reflected in the sea-ice bacterial communities. Of the dominating bacterial genera, Polaribacter seemed to benefit the most from the increase in algal biomass, since they covered approximately 39% of the total community at the southernmost stations with higher (>6 μg l(-1) ) chl-a concentrations and only 9% at the northernmost station with lower chl-a concentrations (<6 μg l(-1) ). The sea-ice bacterial communities also varied between the ice horizons at all three stations and thus we recommend that for future studies multiple ice horizons be sampled to cover the variability in sea-ice bacterial communities in spring. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Thermal infrared and visual observations of a water ice lag in the Mars southern summer

USGS Publications Warehouse

Titus, T.N.

2005-01-01

We present thermal infrared and visual evidence for the existence of water ice lags in the early southern summer. The observed H2O-ice lags lay in and near a chasma and appears to survive between 6-8 sols past the sublimation of the CO2. Possible sources of the H2O that compose the lag are (1) atmospheric H2O that is incorporated into the seasonal cap during condensation, (2) cold trapping of atmospheric water vapor onto the surface of the cap in the spring, or (3) a combination of the 2 processes where water is released from the sublimating cap only to be transported back over the cap edge and cold trapped. We refer to this later process as the "Houben" effect which may enrich the amount of water contained in the seasonal cap at 85??S by as much as a factor of 15. This phenomenon, which has already been identified for the northern retreating cap, may present an important water transport mechanism in the Southern Hemisphere.

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.

Spring and fall phytoplankton blooms in a productive subarctic ecosystem, the eastern Bering Sea, during 1995-2011

NASA Astrophysics Data System (ADS)

Sigler, Michael F.; Stabeno, Phyllis J.; Eisner, Lisa B.; Napp, Jeffrey M.; Mueter, Franz J.

2014-11-01

The timing and magnitude of phytoplankton blooms in subarctic ecosystems often strongly influence the amount of energy that is transferred through subsequent trophic pathways. In the eastern Bering Sea, spring bloom timing has been linked to ice retreat timing and production of zooplankton and fish. A large part of the eastern Bering Sea shelf (~500 km wide) is ice-covered during winter and spring. Four oceanographic moorings have been deployed along the 70-m depth contour of the eastern Bering Sea shelf with the southern location occupied annually since 1995, the two northern locations since 2004 and the remaining location since 2001. Chlorophyll a fluorescence data from the four moorings provide 37 realizations of a spring bloom and 33 realizations of a fall bloom. We found that in the eastern Bering Sea: if ice was present after mid-March, spring bloom timing was related to ice retreat timing (p<0.001, df=1, 24); if ice was absent or retreated before mid-March, a spring bloom usually occurred in May or early June (average day 148, SE=3.5, n=11). A fall bloom also commonly occurred, usually in late September (average day 274, SE=4.2, n=33), and its timing was not significantly related to the timing of storms (p=0.88, df=1, 27) or fall water column overturn (p=0.49, df=1, 27). The magnitudes of the spring and fall blooms were correlated (p=0.011, df=28). The interval between the spring and fall blooms varied between four to six months depending on year and location. We present a hypothesis to explain how the large crustacean zooplankton taxa Calanus spp. likely respond to variation in the interval between blooms (spring to fall and fall to spring).

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.

Phytoplankton standing crops within an Antarctic ice edge assessed by satellite remote sensing

NASA Technical Reports Server (NTRS)

Sullivan, C. W.; Mcclain, C. R.; Comiso, J. C.; Smith, W. O., Jr.

1988-01-01

The dynamic interactions between the pack-ice recession and the occurrence of ice blooms of phytoplankton in waters of the marginal ice zone within an Antarctic ice edge were investigated using CZCS and SMMR imageries from the Nimbus 7 satellite (September 16-December 17, 1983), together with in situ measurements of pigments and sea ice concentration carried out from November 7 to December 2. A substantial amount of spatial variability in pigment concentration was observed to occur along the ice edge in the Weddell Sea. The relationships among light, ice distribution, and vertical stability and their effects on observed spatial variations in phytoplankton biomass are discussed. The results of this investigation suggest that the retreat of ice provides an input of significant volumes of meltwater which creates vertical stability for a period necessary to permit growth and accumulation of phytoplankton.

A coupled dynamic-thermodynamic model of an ice-ocean system in the marginal ice zone

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa

1987-01-01

Thermodynamics are incorporated into a coupled ice-ocean model in order to investigate wind-driven ice-ocean processes in the marginal zone. Upswelling at the ice edge which is generated by the difference in the ice-air and air-water surface stresses is found to give rise to a strong entrainment by drawing the pycnocline closer to the surface. Entrainment is shown to be negligible outside the areas affected by the ice edge upswelling. If cooling at the top is included in the model, the heat and salt exchanges are further enhanced in the upswelling areas. It is noted that new ice formation occurs in the region not affected by ice edge upswelling, and it is suggested that the high-salinity mixed layer regions (with a scale of a few Rossby radii of deformation) will overturn due to cooling, possibly contributing to the formation of deep water.

Simultaneous teleseismic and geodetic observations of the stick-slip motion of an Antarctic ice stream.

PubMed

Wiens, Douglas A; Anandakrishnan, Sridhar; Winberry, J Paul; King, Matt A

2008-06-05

Long-period seismic sources associated with glacier motion have been recently discovered, and an increase in ice flow over the past decade has been suggested on the basis of secular changes in such measurements. Their significance, however, remains uncertain, as a relationship to ice flow has not been confirmed by direct observation. Here we combine long-period surface-wave observations with simultaneous Global Positioning System measurements of ice displacement to study the tidally modulated stick-slip motion of the Whillans Ice Stream in West Antarctica. The seismic origin time corresponds to slip nucleation at a region of the bed of the Whillans Ice Stream that is likely stronger than in surrounding regions and, thus, acts like an 'asperity' in traditional fault models. In addition to the initial pulse, two seismic arrivals occurring 10-23 minutes later represent stopping phases as the slip terminates at the ice stream edge and the grounding line. Seismic amplitude and average rupture velocity are correlated with tidal amplitude for the different slip events during the spring-to-neap tidal cycle. Although the total seismic moment calculated from ice rigidity, slip displacement, and rupture area is equivalent to an earthquake of moment magnitude seven (M(w) 7), seismic amplitudes are modest (M(s) 3.6-4.2), owing to the source duration of 20-30 minutes. Seismic radiation from ice movement is proportional to the derivative of the moment rate function at periods of 25-100 seconds and very long-period radiation is not detected, owing to the source geometry. Long-period seismic waves are thus useful for detecting and studying sudden ice movements but are insensitive to the total amount of slip.

A probabilistic verification score for contours demonstrated with idealized ice-edge forecasts

NASA Astrophysics Data System (ADS)

Goessling, Helge; Jung, Thomas

2017-04-01

We introduce a probabilistic verification score for ensemble-based forecasts of contours: the Spatial Probability Score (SPS). Defined as the spatial integral of local (Half) Brier Scores, the SPS can be considered the spatial analog of the Continuous Ranked Probability Score (CRPS). Applying the SPS to idealized seasonal ensemble forecasts of the Arctic sea-ice edge in a global coupled climate model, we demonstrate that the SPS responds properly to ensemble size, bias, and spread. When applied to individual forecasts or ensemble means (or quantiles), the SPS is reduced to the 'volume' of mismatch, in case of the ice edge corresponding to the Integrated Ice Edge Error (IIEE).

Multi-channel Ice Penetrating Radar Traverse for Estimates of Firn Density in the Percolation Zone, Western Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Meehan, T.; Osterberg, E. C.; Lewis, G.; Overly, T. B.; Hawley, R. L.; Bradford, J.; Marshall, H. P.

2016-12-01

To better predict the response of the Greenland Ice Sheet (GrIS) to future warming, leading edge Regional Climate Models (RCM) must be calibrated with in situ measurements of recent accumulation and melt. Mass balance estimates averaged across the entire Greenland Ice Sheet (GrIS) vary between models by more than 30 percent, and regional comparisons of mass balance reconstructions in Greenland vary by 100 percent or more. Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) is a multi-year and multi-disciplinary 1700 km science traverse from Raven/Dye2 in SW Greenland, to Summit Station. Multi-offset radar measurements can provide high accuracy electromagnetic (EM) velocity estimates of the firn to within (+-) 0.002 to 0.003 m/ns. EM velocity, in turn, can be used to estimate bulk firn density. Using a mixing equation such as the CRIM Equation we use the measured EM velocity, along with the known EM velocity in air and ice, to estimate bulk density. During spring 2016, we used multi-channel 500MHz radar in a multi-offset configuration to survey more than 800 km from Raven towards summit. Preliminary radar-derived snow density estimates agree with density estimates from a firn core measurement ( 50 kg/m3), despite the lateral heterogeneity of the firn across the length of the antenna array (12 m).

A method of predicting flow rates required to achieve anti-icing performance with a porous leading edge ice protection system

NASA Technical Reports Server (NTRS)

Kohlman, D. L.; Albright, A. E.

1983-01-01

An analytical method was developed for predicting minimum flow rates required to provide anti-ice protection with a porous leading edge fluid ice protection system. The predicted flow rates compare with an average error of less than 10 percent to six experimentally determined flow rates from tests in the NASA Icing Research Tunnel on a general aviation wing section.

Patterns of Macrozooplankton and Fish Occurrence Beneath McMurdo Sound Fast Ice during Spring/Summer 2014/2015

NASA Astrophysics Data System (ADS)

Saenz, B. T.; Daly, K. L.; Kim, S.; Ainley, D. G.; Ballard, G.

2016-02-01

McMurdo Sound, Antarctica, represents a unique environment for study of trophic interactions, where a full complement of marine predators thrive. As part of a greater study of McMurdo Sound food web interactions, including ocean and ice physics, algal characterization, and predator behavior, macrozooplankton and fish were surveyed using bioacoustics and video using a specially-designed under-ice ROV. Acoustic returns from 82 under-ice surveys were divided into classes consisting of krill, silverfish, and weak scatters. Krill were scarce during surveys in late November, but increased in abundance in association with increasing chlorophyll a in December and early January when surveys ended. The greatest concentrations of krill were found near Ross Island in the eastern Sound, where southerly currents move high-productivity waters beneath the fast ice. Conversely, silverfish, especially schools of juveniles, were found in greater abundance toward the west where currents flow northward and platelet ice typically blocked light from surface waters. Silverfish were rare toward the end of the survey in late December/early January, but possibly had moved deeper than the acoustic instrument could detect. Overall, krill were less abundant and occurred deeper in the water column within 2 km of the fast ice edge, which was accessible by air-breathing predators, suggesting that predation pressure helped structure krill abundance or distribution. Acoustic returns from weak scatters, which included observed jellies, pteropods, detached ice algae and potentially other mesoplankton in high abundance such as copepods, also increased during the study period and co-occurred with chlorophyll a. The patterns of macrozooplankton and fish observed in McMurdo Sound raise important questions about source-sink dynamics, overwinter strategies of mid-trophic organisms, prey-predator dynamics, and sea-ice structuring of ecosystems.

Hydro-chemical detection of permafrost degradation in the Eastern European Alps - Implications for geomorphological process studies and natural hazard assessment

NASA Astrophysics Data System (ADS)

Kraushaar, Sabine; Kamleitner, Sarah; Czarnowsky, Verena; Blöthe, Jan; Morche, David; Knöller, Kay; Lachner, Johannes

2017-04-01

The Gepatschferner glacier in the Upper Kaunertal valley is one of the fastest melting glaciers in the Eastern European Alps. With a retreat rate of around 110 m a-1 since the hydrological year 2012/ 2013, unconsolidated sediments of steep lateral moraines have been exposed to erosion, from which nowadays episodic and perennial springs well. We hypothesize that the springs indicate the melt out of dead ice lenses in areas below 2500 m, causing a potential significant morphological change in the moraines and a decrease of slope stability in the proglacial long after glacier retreat. However, permafrost degradation has not been considered so far in contemporary erosion measurements. The present study aims to identify the spring water's origin and displays first attempts of quantifying thermal erosion, which describes the matrix volume loss due to melting and drainage of ice water. Samples were routinely analyzed for temperature, electrical conductivity, δ2H, and δ18O. Results support the hypothesis that certain springs derive from melting ice of similar isotopic signature as the glacier. In a second step, chosen samples were examined for the long-lived anthropogenic nuclide 129I. Since the 1950s the atmospheric abundance of 129I has significantly increased. Its occurrence in the water samples hints a surface contact of the waters in the last 65 years. Springs of ice origin show little 129I content and are believed to derive from dead ice by the glacier. First electric resistivity measurements support the hydro-chemical results and suggest the existence of ice lenses in the subsurface. Ice ablation and discharge measurements allowed first estimates of the thermal erosion volume caused by the melt out and drainage of ice lenses.

Intra-annual variations in atmospheric dust and tritium in the North Pacific region detected from an ice core from Mount Wrangell, Alaska

NASA Astrophysics Data System (ADS)

Yasunari, Teppei J.; Shiraiwa, Takayuki; Kanamori, Syosaku; Fujii, Yoshiyuki; Igarashi, Makoto; Yamazaki, Koji; Benson, Carl S.; Hondoh, Takeo

2007-05-01

The North Pacific is subject to various seasonal climate phenomena and material circulations. Therefore intra-annual ice core data are necessary for an assessment of the climate variations. To assess past variations, a 50-m ice core was drilled at the summit of Mount Wrangell Volcano, Alaska. The dust number, tritium concentrations, and stable hydrogen isotope were analyzed. The period covered was from 1992 to 2002. We found that the concentrations of both fine dust (0.52-1.00 μm), an indicator of long-range transport, and coarse dust (1.00-8.00 μm) increased together every spring. Moreover, their concentrations increased drastically after 2000, corresponding to the recent increase in Asian dust outbreaks in spring. Additionally, an increase in the spring of 2001 corresponded to the largest dust storm recorded in east Asia since 1979. Therefore our findings imply that Asian dust strongly polluted Mount Wrangell every spring. The stratospheric tracer, tritium, had late spring maxima almost every year, and we found this useful for ice core dating to identify late spring in the North Pacific region. We also found that a high positive annual correlation existed between the calculated tritium and fine dust fluxes from late spring to summer. We propose that an annual relationship between the stratosphere-troposphere exchange and Asian dust storm are most closely connected in late spring because their activities are weak in summer. The Mount Wrangell ice core is important and useful for assessing the dust and tritium circulation in the distant past around the North Pacific with probable intra-annual timescale information.

Under-Ice Phytoplankton Blooms Inhibited by Spring Convective Mixing in Refreezing Leads

NASA Astrophysics Data System (ADS)

Lowry, Kate E.; Pickart, Robert S.; Selz, Virginia; Mills, Matthew M.; Pacini, Astrid; Lewis, Kate M.; Joy-Warren, Hannah L.; Nobre, Carolina; van Dijken, Gert L.; Grondin, Pierre-Luc; Ferland, Joannie; Arrigo, Kevin R.

2018-01-01

Spring phytoplankton growth in polar marine ecosystems is limited by light availability beneath ice-covered waters, particularly early in the season prior to snowmelt and melt pond formation. Leads of open water increase light transmission to the ice-covered ocean and are sites of air-sea exchange. We explore the role of leads in controlling phytoplankton bloom dynamics within the sea ice zone of the Arctic Ocean. Data are presented from spring measurements in the Chukchi Sea during the Study of Under-ice Blooms In the Chukchi Ecosystem (SUBICE) program in May and June 2014. We observed that fully consolidated sea ice supported modest under-ice blooms, while waters beneath sea ice with leads had significantly lower phytoplankton biomass, despite high nutrient availability. Through an analysis of hydrographic and biological properties, we attribute this counterintuitive finding to springtime convective mixing in refreezing leads of open water. Our results demonstrate that waters beneath loosely consolidated sea ice (84-95% ice concentration) had weak stratification and were frequently mixed below the critical depth (the depth at which depth-integrated production balances depth-integrated respiration). These findings are supported by theoretical model calculations of under-ice light, primary production, and critical depth at varied lead fractions. The model demonstrates that under-ice blooms can form even beneath snow-covered sea ice in the absence of mixing but not in more deeply mixed waters beneath sea ice with refreezing leads. Future estimates of primary production should account for these phytoplankton dynamics in ice-covered waters.

Effect of Ice Formations on Section Drag of Swept NACA 63A-009 Airfoil with Partical-span Leading-edge Slat for Various Modes of Thermal Ice Protection

NASA Technical Reports Server (NTRS)

Von Glahn, Uwe H; Gray, Vernon H

1954-01-01

Studies were made to determine the effect of ice formations on the section drag of a 6.9-foot-chord 36 degree swept NACA 63A-009 airfoil with partial-span leading-edge slat. In general, the icing of a thin swept airfoil will result in greater aerodynamic penalties than for a thick unswept airfoil. Glaze-ice formations at the leading edge of the airfoil caused large increases in section drag even at liquid-water content of 0.39 gram per cubic meter. The use of an ice-free parting strip in the stagnation region caused a negligible change in drag compared with a completely unheated airfoil. Cyclic de-icing when properly applied caused the drag to decrease almost to the bare-airfoil drag value.

Striking similarities in temporal changes to spring sea ice occurrence across the central Canadian Arctic Archipelago over the last 7000 years

NASA Astrophysics Data System (ADS)

Belt, Simon T.; Vare, Lindsay L.; Massé, Guillaume; Manners, Hayley R.; Price, John C.; MacLachlan, Suzanne E.; Andrews, John T.; Schmidt, Sabine

2010-12-01

A 7000 year spring sea ice record for Victoria Strait (ARC-4) and Dease Strait (ARC-5) in the Canadian Arctic Archipelago (CAA) has been determined by quantification of the sea ice diatom-derived biomarker IP 25 in two marine sediment piston cores obtained in 2005. The chronologies of the ARC-4 and ARC-5 cores were determined using a combination of 14C AMS dates obtained from macrobenthic fossils and magnetic susceptibility measurements. The ages of the tops of the piston cores were estimated by matching chemical and physical parameters with those obtained from corresponding box cores. These analyses revealed that, while the top of the ARC-4 piston core was estimated to be essentially modern (ca. 60 cal yr BP), a few hundred years of sediment appeared to be absent from the ARC-5 piston core. Downcore changes to IP 25 fluxes for both cores were interpreted in terms of variations in spring sea ice occurrence, and correlations between the individual IP 25 flux profiles for Victoria Strait, Dease Strait and Barrow Strait (reported previously) were shown to be statistically significant at both 50 and 100-year resolutions. The IP 25 data indicate lower spring sea ice occurrences during the early part of the record (ca. 7.0-3.0 cal kyr BP) and for parts of the late Holocene (ca. 1.5-0.8 cal kyr BP), especially for the two lower latitude study locations. In contrast, higher spring sea ice occurrences existed during ca. 3.0-1.5 cal kyr BP and after ca. 800 cal yr BP. The observation of, consecutively, lower and higher spring sea ice occurrence during two periods of the late Holocene, coincides broadly with the Medieval Warm Period and Little Ice Age epochs, respectively. The IP 25 data are complemented by particle size and mineralogical data, although these may alternatively reflect changes in sea level at the study sites. The IP 25 data are also compared to previous proxy-based determinations of palaeo sea ice and palaeoclimate for the CAA, including those based on bowhead whale remains and dinocyst assemblages. The spatial consistency in the proxy data which, most notably, indicates an increase in spring sea ice occurrence around 3 cal kyr BP, provides a potentially useful benchmark for the termination of the Holocene Thermal Maximum for the central CAA.

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.

Remote sensing of the Fram Strait marginal ice zone

USGS Publications Warehouse

Shuchman, R.A.; Burns, B.A.; Johannessen, O.M.; Josberger, E.G.; Campbell, W.J.; Manley, T.O.; Lannelongue, N.

1987-01-01

Sequential remote sensing images of the Fram Strait marginal ice zone played a key role in elucidating the complex interactions of the atmosphere, ocean, and sea ice. Analysis of a subset of these images covering a 1-week period provided quantitative data on the mesoscale ice morphology, including ice edge positions, ice concentrations, floe size distribution, and ice kinematics. The analysis showed that, under light to moderate wind conditions, the morphology of the marginal ice zone reflects the underlying ocean circulation. High-resolution radar observations showed the location and size of ocean eddies near the ice edge. Ice kinematics from sequential radar images revealed an ocean eddy beneath the interior pack ice that was verified by in situ oceanographic measurements.

Improving Arctic Sea Ice Edge Forecasts by Assimilating High Horizontal Resolution Sea Ice Concentration Data into the US Navy’s Ice Forecast Systems

DTIC Science & Technology

2016-06-13

Global Ocean Forecast System 3.1 also showed a substantial improvement in ice edge location over a system using the SSMIS sea ice concentration product... Global Ocean Fore- cast System (GOFS 3.1). Prior to 2 February 2015, the ice concentration fields from both ACNFS and GOFS 3.1 had been updated with...Scanning Radiometer (AMSR2) on the Japan Aerospace Exploration Agency (JAXA) Global Change Observation Mission – Water (GCOM-W) platform became available

Seasonality of light transmittance through Arctic sea ice during spring and summe

NASA Astrophysics Data System (ADS)

Nicolaus, M.; Hudson, S. R.; Granskog, M. A.; Pavlov, A.; Taskjelle, T.; Kauko, H.; Katlein, C.; Geland, S.; Perovich, D. K.

2017-12-01

The energy budget of sea ice and the upper ocean during spring, summer, and autumn is strongly affected by the transfer of solar shortwave radiation through sea ice and into the upper ocean. Previous studies highlighted the great importance of the spring-summer transition, when incoming fluxes are highest and even small changes in surface albedo and transmittance have strong impacts on the annual budgets. The timing of melt onset and changes in snow and ice conditions are also crucial for primary productivity and biogeochemical processes. Here we present results from time series measurements of radiation fluxes through seasonal Arctic sea ice, as it may be expected to play a key role in the future Arctic. Our observations were performed during the Norwegian N-ICE drift experiment in 2015 and the Polarstern expedition PS106 in 2017, both studying sea ice north of Svalbard. Autonomous stations were installed to monitor spectral radiation fluxes above and under sea ice. The observation periods cover the spring-summer transition, including snow melt and early melt pond formation. The results show the direct relation of optical properties to under ice algae blooms and their influence on the energy budget. Beyond these results, we will discuss the latest plans and implementation of radiation measurements during the MOSAiC drift in 2019/2020. Then, a full annual cycle of radiation fluxes may be studied from manned and autonomous (buoys) measurements as well as using a remotely operated vehicle (ROV) as measurement platform. These measurements will be performed in direct relation with numerical simulations on different scales.

Zooplankton data: Vertical distributions of zooplankton in the Norweigian and Greenland Seas during summer, 1989

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

Lane, P.V.Z.; Smith, S.L.; Schwarting, E.M.

1993-08-01

Recent studies of zooplankton populations in the Greenland Sea have focused on processes at the Marginal Ice Zone (MIZ) and the areas immediately adjacent to it under the ice and in open water. These studies have shown a relatively short period of intense secondary productivity which is closely linked temporally and spatially to phytoplankton blooms occurring near the ice edge in spring and early summer. During the summer of 1989 we participated in a project focusing on benthic and water column processes in the basins of the Norwegian and Greenland Seas. This study allowed us to compare biological processes atmore » the MIZ with those occurring in the open waters of the Greenland Sea, and to compare processes at both of these locations with those in the Norwegian Sea. The data presented in this report are the results of zooplankton net tows covering the upper 1000 meters of the water column over the Norwegian Sea basin and the Greenland Sea basin, and the upper 500 meters of open water adjacent to the MIZ in the Greenland Sea. Sampling was conducted between 12 and 29 July 1989.« less

Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice

PubMed Central

Kang, Dongdong; Dai, Jiayu; Sun, Huayang; Hou, Yong; Yuan, Jianmin

2013-01-01

The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures. PMID:24253589

Aerodynamic Characterization of a Thin, High-Performance Airfoil for Use in Ground Fluids Testing

NASA Technical Reports Server (NTRS)

Broeren, Andy P.; Lee, Sam; Clark, Catherine

2013-01-01

The FAA has worked with Transport Canada and others to develop allowance times for aircraft operating in ice-pellet precipitation. Wind-tunnel testing has been carried out to better understand the flowoff characteristics and resulting aerodynamic effects of anti-icing fluids contaminated with ice pellets using a thin, high-performance wing section at the National Research Council of Canada Propulsion and Icing Wind Tunnel. The objective of this paper is to characterize the aerodynamic behavior of this wing section in order to better understand the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination. Aerodynamic performance data, boundary-layer surveys and flow visualization were conducted at a Reynolds number of approximately 6.0 x 10(exp 6) and a Mach number of 0.12. The clean, baseline model exhibited leading-edge stall characteristics including a leading-edge laminar separation bubble and minimal or no separation on the trailing edge of the main element or flap. These results were consistent with expected 2-D aerodynamics and showed no anomalies that could adversely affect the evaluation of anti-icing fluids and ice-pellet contamination on the wing. Tests conducted with roughness and leading-edge flow disturbances helped to explain the aerodynamic impact of the anti-icing fluids and contamination. The stalling characteristics of the wing section with fluid and contamination appear to be driven at least partially by the effects of a secondary wave of fluid that forms near the leading edge as the wing is rotated in the simulated takeoff profile. These results have provided a much more complete understanding of the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination on this wing section. This is important since these results are used, in part, to develop the ice-pellet allowance times that are applicable to many different airplanes.

Aerodynamic Characterization of a Thin, High-Performance Airfoil for Use in Ground Fluids Testing

NASA Technical Reports Server (NTRS)

Broeren, Andy P.; Lee, Sam; Clark, Catherine

2013-01-01

The FAA has worked with Transport Canada and others to develop allowance times for aircraft operating in ice-pellet precipitation. Wind-tunnel testing has been carried out to better understand the flowoff characteristics and resulting aerodynamic effects of anti-icing fluids contaminated with ice pellets using a thin, high-performance wing section at the National Research Council of Canada Propulsion and Icing Wind Tunnel. The objective of this paper is to characterize the aerodynamic behavior of this wing section in order to better understand the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination. Aerodynamic performance data, boundary-layer surveys and flow visualization were conducted at a Reynolds number of approximately 6.0×10(exp 6) and a Mach number of 0.12. The clean, baseline model exhibited leading-edge stall characteristics including a leading-edge laminar separation bubble and minimal or no separation on the trailing edge of the main element or flap. These results were consistent with expected 2-D aerodynamics and showed no anomalies that could adversely affect the evaluation of anti-icing fluids and ice-pellet contamination on the wing. Tests conducted with roughness and leading-edge flow disturbances helped to explain the aerodynamic impact of the anti-icing fluids and contamination. The stalling characteristics of the wing section with fluid and contamination appear to be driven at least partially by the effects of a secondary wave of fluid that forms near the leading edge as the wing is rotated in the simulated takeoff profile. These results have provided a much more complete understanding of the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination on this wing section. This is important since these results are used, in part, to develop the ice-pellet allowance times that are applicable to many different airplanes.

Community dynamics of bottom-ice algae in Dease Strait of the Canadian Arctic

NASA Astrophysics Data System (ADS)

Campbell, K.; Mundy, C. J.; Landy, J. C.; Delaforge, A.; Michel, C.; Rysgaard, S.

2016-12-01

Sea ice algae are a characteristic feature in ice-covered seas, contributing a significant fraction of the total primary production in many areas and providing a concentrated food source of high nutritional value to grazers in the spring. Algae respond to physical changes in the sea ice environment by modifying their cellular carbon, nitrogen and pigment content, and by adjusting their photophysiological characteristics. In this study we examined how the ratios of particulate organic carbon (POC) to nitrogen (PON), and POC to chlorophyll a (chl a), responded to the evolving snow-covered sea ice environment near Cambridge Bay, Nunavut, during spring 2014. We also estimated photosynthesis-irradiance (PI) curves using oxygen-optodes and evaluated the resulting time-series of PI parameters under thin and thick snow-covered sites. There were no significant differences in PI parameters between samples from different overlying snow depths, and only the maximum photosynthetic rates in the absence of photoinhibition (PsB) and photoacclimation (IS) parameters changed significantly over the spring bloom. Furthermore, we found that both these parameters increased over time in response to increasing percent transmission of photosynthetically active radiation (TPAR) through the ice, indicating that light was a limiting factor of photosynthesis and was an important driver of temporal (over the spring) rather than spatial (between snow depths) variability in photophysiological response. However, we note that spatial variability in primary production was evident. Higher TPAR over the spring and under thin snow affected the composition of algae over both time and space, causing greater POC:chl a estimates in late spring and under thin snow cover. Nitrogen limitation was pronounced in this study, likely reducing PsB and algal photosynthetic rates, and increasing POC:PON ratios to over six times the Redfield average. Our results highlight the influence of both light and nutrients on ice algal biomass composition and photophysiology, and suggest a limitation by both resources over a diel period.

Flooding of the Ob and Irtysh Rivers, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

These images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite shows the cause and effect of the large-scale seasonal flooding experienced on rivers throughout Siberia each year. Because many Siberian rivers flow from south to north, they flood regularly in the spring as meltwater from southern latitudes backs up against the still-frozen northern reaches of the rivers.These images show the Ob' River on the western edge of the Central Siberian Plateau. The images from June 20, 2002, show the mouth of the Ob' River (large river at left) where it empties into Kara Sea. In the false-color image, Vegetation appears in bright green, water appears dark blue or black, and ice appears bright blue. The ice is still choking the river's outlet to the sea.The effect of this ice block on the more southern stretches of the river can be seen in the images captured on June 17. In the false-color image, water is black, vegetation is in shades of gold and green, and clouds are pale orange. In the northernmost portion of the Ob' visible in this image (the Ob' runs southeast to northwest in the image), what is normally a fine mesh of braided streams and branches of the river channel has become almost a lake in places. The flood waters have engorged the river to 52 kilometers (32 miles) wide in places. Rivers can back up for hundreds of miles, and cause devastating flooding for towns and villages along the banks. Often, explosives are dropped into ice jams in an effort to free the river and give the flood waters a chance to escape. The spring and summer floods of 2002 have proven to be quite severe and perhaps as many as 100,000 people have been affected across the country. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

Mouth of the Ob River, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

These images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite shows the cause and effect of the large-scale seasonal flooding experienced on rivers throughout Siberia each year. Because many Siberian rivers flow from south to north, they flood regularly in the spring as meltwater from southern latitudes backs up against the still-frozen northern reaches of the rivers.These images show the Ob' River on the western edge of the Central Siberian Plateau. The images from June 20, 2002, show the mouth of the Ob' River (large river at left) where it empties into Kara Sea. In the false-color image, Vegetation appears in bright green, water appears dark blue or black, and ice appears bright blue. The ice is still choking the river's outlet to the sea.The effect of this ice block on the more southern stretches of the river can be seen in the images captured on June 17. In the false-color image, water is black, vegetation is in shades of gold and green, and clouds are pale orange. In the northernmost portion of the Ob' visible in this image (the Ob' runs southeast to northwest in the image), what is normally a fine mesh of braided streams and branches of the river channel has become almost a lake in places. The flood waters have engorged the river to 52 kilometers (32 miles) wide in places. Rivers can back up for hundreds of miles, and cause devastating flooding for towns and villages along the banks. Often, explosives are dropped into ice jams in an effort to free the river and give the flood waters a chance to escape. The spring and summer floods of 2002 have proven to be quite severe and perhaps as many as 100,000 people have been affected across the country. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

A coupled ice-ocean model of ice breakup and banding in the marginal ice zone

NASA Technical Reports Server (NTRS)

Smedstad, O. M.; Roed, L. P.

1985-01-01

A coupled ice-ocean numerical model for the marginal ice zone is considered. The model consists of a nonlinear sea ice model and a two-layer (reduced gravity) ocean model. The dependence of the upwelling response on wind stress direction is discussed. The results confirm earlier analytical work. It is shown that there exist directions for which there is no upwelling, while other directions give maximum upwelling in terms of the volume of uplifted water. The ice and ocean is coupled directly through the stress at the ice-ocean interface. An interesting consequence of the coupling is found in cases when the ice edge is almost stationary. In these cases the ice tends to break up a few tenths of kilometers inside of the ice edge.

Possible impacts of ozone depletion on trophic interactions and biogenic vertical carbon flux in the Southern Ocean

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

Marchant, H.J.; Davidson, A.

1992-03-01

Among the most productive region of the Southern Ocean is the marginal ice edge zone that trails the retreating ice edge in spring and early summer. The timing of this near-surface phytoplankton bloom coincides with seasonal stratospheric ozone depletion when UV irradiance is reportedly as high as in mid-summer. Recent investigations indicate that antarctic marine phytoplankton are presently UV stressed. The extent to which increasing UV radiation diminishes the ability of phytoplankton to fix C02 and/or leads to changes in their species composition is equivocal. The colonial stage in the life cycle of the alga Phaeocystis pouchetii is one ofmore » the major components of the bloom. The authors have found that this alga produces extracellular products which are strongly UV-B absorbing. When exposed to increasing levels of UV-B radiation, survival of antarctic colonial Phaeocystis was significantly greater than colonies of this species from temperate waters and of the single-celled stage of its life cycle which produces no UV-B-absorbing compounds. Phaeocystis is apparently a minor dietary component of Antarctic krill, Euphausia superba, and its nutritional value to crustacea is reportedly low. Phytoplankton, principally diatoms, together with fecal pellets and molted exoskeletons of grazers contribute most of the particulate carbon flux from the euphotic zone to deep water.« less

Spatial extent and temporal variability of Greenland firn aquifers detected by ground and airborne radars

NASA Astrophysics Data System (ADS)

Miège, Clément; Forster, Richard R.; Brucker, Ludovic; Koenig, Lora S.; Solomon, D. Kip; Paden, John D.; Box, Jason E.; Burgess, Evan W.; Miller, Julie Z.; McNerney, Laura; Brautigam, Noah; Fausto, Robert S.; Gogineni, Sivaprasad

2016-12-01

We document the existence of widespread firn aquifers in an elevation range of 1200-2000 m, in the high snow-accumulation regions of the Greenland ice sheet. We use NASA Operation IceBridge accumulation radar data from five campaigns (2010-2014) to estimate a firn-aquifer total extent of 21,900 km2. We investigate two locations in Southeast Greenland, where repeated radar profiles allow mapping of aquifer-extent and water table variations. In the upper part of Helheim Glacier the water table rises in spring following above-average summer melt, showing the direct firn-aquifer response to surface meltwater production changes. After spring 2012, a drainage of the firn-aquifer lower margin (5 km) is inferred from both 750 MHz accumulation radar and 195 MHz multicoherent radar depth sounder data. For 2011-2014, we use a ground-penetrating radar profile located at our Ridgeline field site and find a spatially stable aquifer with a water table fluctuating less than 2.5 m vertically. When combining radar data with surface topography, we find that the upper elevation edge of firn aquifers is located directly downstream of locally high surface slopes. Using a steady state 2-D groundwater flow model, water is simulated to flow laterally in an unconfined aquifer, topographically driven by ice sheet surface undulations until the water encounters crevasses. Simulations suggest that local flow cells form within the Helheim aquifer, allowing water to discharge in the firn at the steep-to-flat transitions of surface topography. Supported by visible imagery, we infer that water drains into crevasses, but its volume and rate remain unconstrained.

Observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-01-01

Based on airborne spectral imaging observations three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and ice floes have been identified and quantified. A method is presented to discriminate sea ice and open water in case of clouds from imaging radiance measurements. This separation simultaneously reveals that in case of clouds the transition of radiance between open water and sea ice is not instantaneously but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of sea ice - open water boundaries, while the nadir radiance above dark surfaces is enhanced compared to situations with clouds located above horizontal homogeneous surfaces. With help of the observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge. This affected distance Δ L was found to depend on both, cloud and sea ice properties. For a ground overlaying cloud in 0-200 m altitude, increasing the cloud optical thickness from τ = 1 to τ = 10 decreases Δ L from 600 to 250 m, while increasing cloud base altitude or cloud geometrical thickness can increase Δ L; Δ L(τ = 1/10) = 2200 m/1250 m for 500-1000 m cloud altitude. To quantify the effect for different shapes and sizes of the ice floes, various albedo fields (infinite straight ice edge, circles, squares, realistic ice floe field) were modelled. Simulations show that Δ L increases by the radius of the ice floe and for sizes larger than 6 km (500-1000 m cloud altitude) asymptotically reaches maximum values, which corresponds to an infinite straight ice edge. Furthermore, the impact of these 3-D-radiative effects on retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30% in retrievals of cloud optical thickness and effective radius reff, respectively. With help of Δ L quantified here, an estimate of the distance to the ice edge for which the retrieval errors are negligible is given.

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.

Observations of the north polar water ice annulus on Mars using THEMIS and TES

USGS Publications Warehouse

Wagstaff, K.L.; Titus, T.N.; Ivanov, A.B.; Castano, R.; Bandfield, J.L.

2008-01-01

The Martian seasonal CO2 ice caps advance and retreat each year. In the spring, as the CO2 cap gradually retreats, it leaves behind an extensive defrosting zone from the solid CO2 cap to the location where all CO2 frost has sublimated. We have been studying this phenomenon in the north polar region using data from the THermal EMission Imaging System (THEMIS), a visible and infra-red (IR) camera on the Mars Odyssey spacecraft, and the Thermal Emission Spectrometer (TES) on Mars Global Surveyor. Recently, we discovered that some THEMIS images of the CO2 defrosting zone contain evidence for a distinct defrosting phenomenon: some areas just south of the CO2 cap edge are too bright in visible wavelengths to be defrosted terrain, but too warm in the IR to be CO2 ice. We hypothesize that we are seeing evidence for a seasonal annulus of water ice (frost) that recedes with the seasonal CO2 cap, as predicted by previous workers. In this paper, we describe our observations with THEMIS and compare them to simultaneous observations by TES and OMEGA. All three instruments find that this phenomenon is distinct from the CO2 cap and most likely composed of water ice. We also find strong evidence that the annulus widens as it recedes. Finally, we show that this annulus can be detected in the raw THEMIS data as it is collected, enabling future long-term onboard monitoring. ?? 2007.

Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection Against Icing. 1: Unpartitioned Blades

NASA Technical Reports Server (NTRS)

Mulholland, Donald R.; Perkins, Porter J.

1948-01-01

An investigation to determine the effectiveness of icing protection afforded by air-heating hollow steel unpartitioned propeller blades has been conducted In the NACA Cleveland icing research tunnel. The propeller used was a production model modified with blade shank and tip openings to permit internal passage of heated air. Blade-surface and heated-air temperatures were obtained and photographic observations of Ice formations were made with variations In icing intensity and heating rate to the blades. For the conditions of Icing to which the propeller was subjected, it was found that adequate ice protection was afforded with a heating rate of 40 1 000 Btu per hour per blade. With less than 40,000 Btu per hour per blade, ice protection failed because of significant ice accretions on the leading edge. The chordwise distribution of heat was unsatisfactory with most of the available heat dissipated well back of the leading edge on both the thrust and camber face's instead of at the leading edge where it was most needed. A low utilization of available heat for icing protection is indicated by a beat-exchanger effectiveness of approximately 47 percent.

Arctic spring ozone reduction associated with projected sea ice loss

NASA Astrophysics Data System (ADS)

Deser, C.; Sun, L.; Tomas, R. A.; Polvani, L. M.

2013-12-01

The impact of Arctic sea ice loss on the stratosphere is investigated using the Whole-Atmosphere Community Climate Model (WACCM), by prescribing the sea ice in the late 20th century and late 21st century, respectively. The localized Sea Surface Temperature (SST) change associated with sea ice melt is also included in the future run. Overall, the model simulates a negative annular-mode response in the winter and spring. In the stratosphere, polar vortex strengthens from February to April, peaking in March. Consistent with it, there is an anomalous cooling in the high-latitude stratosphere, and polar cap ozone reduction is up to 20 DU. Since the difference between these two runs lies only in the sea ice and localized SST in the Arctic, the stratospheric circulation and ozone changes can be attributed to the surface forcing. Eliassen-Palm analysis reveals that the upward propagation of planetary waves is suppressed in the spring as a consequence of sea ice loss. The reduction in propagation causes less wave dissipation and thus less zonal wind deceleration in the extratropical stratosphere.

Processes influencing formation of low-salinity high-biomass lenses near the edge of the Ross Ice Shelf

NASA Astrophysics Data System (ADS)

Li, Yizhen; McGillicuddy, Dennis J.; Dinniman, Michael S.; Klinck, John M.

2017-02-01

Both remotely sensed and in situ observations in austral summer of early 2012 in the Ross Sea suggest the presence of cold, low-salinity, and high-biomass eddies along the edge of the Ross Ice Shelf (RIS). Satellite measurements include sea surface temperature and ocean color, and shipboard data sets include hydrographic profiles, towed instrumentation, and underway acoustic Doppler current profilers. Idealized model simulations are utilized to examine the processes responsible for ice shelf eddy formation. 3-D model simulations produce similar cold and fresh eddies, although the simulated vertical lenses are quantitatively thinner than observed. Model sensitivity tests show that both basal melting underneath the ice shelf and irregularity of the ice shelf edge facilitate generation of cold and fresh eddies. 2-D model simulations further suggest that both basal melting and downwelling-favorable winds play crucial roles in forming a thick layer of low-salinity water observed along the edge of the RIS. These properties may have been entrained into the observed eddies, whereas that entrainment process was not captured in the specific eddy formation events studied in our 3-D model-which may explain the discrepancy between the simulated and observed eddies, at least in part. Additional sensitivity experiments imply that uncertainties associated with background stratification and wind stress may also explain why the model underestimates the thickness of the low-salinity lens in the eddy interiors. Our study highlights the importance of incorporating accurate wind forcing, basal melting, and ice shelf irregularity for simulating eddy formation near the RIS edge. The processes responsible for generating the high phytoplankton biomass inside these eddies remain to be elucidated. Appendix B. Details for the basal melting and mechanical forcing by the ice shelf edge.

Edge of Ice Shelf

NASA Image and Video Library

2017-12-08

Edge of an ice shelf in Adelaide Island, off the Antarctic Peninsula. Credit: NASA / Maria-Jose Vinas NASA's Operation IceBridge is an airborne science mission to study Earth's polar ice. For more information about IceBridge, visit: www.nasa.gov/icebridge NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Snow accumulation on Arctic sea ice: is it a matter of how much or when?

NASA Astrophysics Data System (ADS)

Webster, M.; Petty, A.; Boisvert, L.; Markus, T.

2017-12-01

Snow on sea ice plays an important, yet sometimes opposing role in sea ice mass balance depending on the season. In autumn and winter, snow reduces the heat exchange from the ocean to the atmosphere, reducing sea ice growth. In spring and summer, snow shields sea ice from solar radiation, delaying sea ice surface melt. Changes in snow depth and distribution in any season therefore directly affect the mass balance of Arctic sea ice. In the western Arctic, a decreasing trend in spring snow depth distribution has been observed and attributed to the combined effect of peak snowfall rates in autumn and the coincident delay in sea ice freeze-up. Here, we build on this work and present an in-depth analysis on the relationship between snow accumulation and the timing of sea ice freeze-up across all Arctic regions. A newly developed two-layer snow model is forced with eight reanalysis precipitation products to: (1) identify the seasonal distribution of snowfall accumulation for different regions, (2) highlight which regions are most sensitive to the timing of sea ice freeze-up with regard to snow accumulation, and (3) show, if precipitation were to increase, which regions would be most susceptible to thicker snow covers. We also utilize a comprehensive sensitivity study to better understand the factors most important in controlling winter/spring snow depths, and to explore what could happen to snow depth on sea ice in a warming Arctic climate.

Sulfur/Carbonate Springs and Life in Glacial Ice

NASA Technical Reports Server (NTRS)

Allen, Carlton; Grasby, Stephen; Longazo, Teresa

2001-01-01

Ice in the near subsurface of Mars apparently discharges liquid water on occasion. Cold-tolerant microorganisms are known to exist within terrestrial glacial ice, and may be brought to the surface as a result of melting events. We are investigating a set of springs that deposit sulfur and carbonate minerals, as well as evidence of microbial life, on the surface of a glacier in the Canadian arctic. Additional information is contained in the original extended abstract.

Multi-epoch Detections of Water Ice Absorption in Edge-on Disks around Herbig Ae Stars: PDS 144N and PDS 453

NASA Astrophysics Data System (ADS)

Terada, Hiroshi; Tokunaga, Alan T.

2017-01-01

We report the multi-epoch detections of water ice in 2.8-4.2 μ {{m}} spectra of two Herbig Ae stars, PDS 144N (A2 IVe) and PDS 453 (F2 Ve), which have an edge-on circumstellar disk. The detected water ice absorption is found to originate from their protoplanetary disks. The spectra show a relatively shallow absorption of water ice of around 3.1 μ {{m}} for both objects. The optical depths of the water ice absorption are ˜0.1 and ˜0.2 for PDS 144N and PDS 453, respectively. Compared to the water ice previously detected in low-mass young stellar objects with an edge-on disk with a similar inclination angle, these optical depths are significantly lower. It suggests that stronger UV radiation from the central stars effectively decreases the water ice abundance around the Herbig Ae stars through photodesorption. The water ice absorption in PDS 453 shows a possible variation of the feature among the six observing epochs. This variation could be due to a change of absorption materials passing through our line of sight to the central star. The overall profile of the water ice absorption in PDS 453 is quite similar to the absorption previously reported in the edge-on disk object d216-0939, and this unique profile may be seen only at a high inclination angle in the range of 76°-80°.

A World of Snowy Dunes

NASA Image and Video Library

2017-08-21

It is spring in the Northern hemisphere when NASA's Mars Reconnaissance Orbiter took this image. Over the winter, snow and ice have inexorably covered the dunes. Unlike on Earth, this snow and ice is carbon dioxide, better known to us as dry ice. When the sun starts shining on it in the spring, the ice on the smooth surface of the dune cracks and escaping gas carries dark sand out from the dune below, often creating beautiful patterns. On the rough surface between the dunes, frost is trapped behind small sheltered ridges. https://photojournal.jpl.nasa.gov/catalog/PIA21882

Climate to fish: Synthesizing field work, data and models in a 39-year retrospective analysis of seasonal processes on the eastern Bering Sea shelf and slope

NASA Astrophysics Data System (ADS)

Ortiz, Ivonne; Aydin, Kerim; Hermann, Albert J.; Gibson, Georgina A.; Punt, André E.; Wiese, Francis K.; Eisner, Lisa B.; Ferm, Nissa; Buckley, Troy W.; Moffitt, Elizabeth A.; Ianelli, James N.; Murphy, James; Dalton, Michael; Cheng, Wei; Wang, Muyin; Hedstrom, Kate; Bond, Nicholas A.; Curchitser, Enrique N.; Boyd, Charlotte

2016-12-01

We combined field data and the output from a climate-to-fish coupled biophysical model to calculate weekly climatologies and 1971-2009 time series of physical and biological drivers for 16 distinct regions of the eastern Bering Sea shelf and slope. We focus on spatial trends and physical-biological interactions as a framework to compare model output to localized or season-specific observations. Data on pollock (≥8 cm) diet were used to evaluate energy flows and zooplankton dynamics predicted by the model. Model validation shows good agreement to sea-ice cover albeit with a one month delay in ice retreat. Likewise, the timing of spring phytoplankton blooms in the model were delayed approximately one month in the south and extend further into summer, but the relative timing between the spring and fall bloom peaks was consistent with observations. Ice-related primary producers may shift the timing of the spring bloom maximum biomass earlier in years when sea ice was still present after mid-March in the southern regions. Including the effects of explicit, dynamic fish predation on zooplankton in the model shifts the seasonal spring peak and distribution of zooplankton later in the year relative to simulations with implicit predation dependent only on zooplankton biomass and temperature; the former capturing the dynamic demand on zooplankton prey by fish. Pollock diets based on stomach samples collected in late fall and winter from 1982-2013 show overwintering euphausiids and small pollock as key prey items in the outer and southern Bering Sea shelf; a characteristic not currently present in the model. The model captured two large-scale gradients, supported by field data, characterizing the overall dynamics: 1) inshore to off-shelf physical and biological differences with a gradient in inter-annual variability from higher frequency inshore to lower frequency offshore; and 2) latitudinal gradients in the timing of events. The combined effects of length of day, bathymetry, and tides, which are consistent from year to year, and the two large-scale gradients, characterize the environment on which regional differences were based and restrict their inter-annual and seasonal variability. Thus, the relative timing and sequence of events remained consistent within regions. The combination of model outputs and observational data revealed specific ecosystem processes: (1) The spatial progression in the timing, peaks and sequence of events over the shelf is driven by wind, sea ice, and stratification and creates a seasonal expansion and contraction of the warmer pelagic and bottom habitat suitable to pollock. (2) The seasonal warming of air temperature and the spring-summer expansion of the warm pelagic and bottom habitats influence the ice retreat and the associated ice edge and open water spring blooms, as well as subsequent production/abundance of copepods and euphausiids. (3) These warmer conditions favor pelagic energy flows to pollock (≥10 cm) and allow their distribution to expand shoreward and northward along the shelf break. (4) The fall-winter expansion of the seasonal ice cover drives the contraction of warmer waters towards the outer and southwest shelf and favors benthic energy flows over most of the shelf. There, fall blooms allow for additional lipid storage by large copepods and euphausiids that sink close to the bottom where they either go into diapause or have a restricted diel migration over winter. (5) During these cold months, the preferred pollock habitat shifts and contracts towards the outer and southwest shelf where their increased density and reduced prey availability leads to winter pollock cannibalism and consumption of overwintering euphausiids. Our project highlights the benefits of linking continuous and long-term field work with the development and implementation of highly complex models. In the face of uncertainty, simulations such as these, tightly coupled to field programs, will be instrumental as testbeds for process exploration and management evaluation, increasing their relevance for future fisheries and ecosystem management and strategic planning.

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.

Arctic energy budget in relation to sea-ice variability on monthly to annual time scales

NASA Astrophysics Data System (ADS)

Krikken, Folmer; Hazeleger, Wilco

2015-04-01

The strong decrease in Arctic sea-ice in recent years has triggered a strong interest in Arctic sea-ice predictions on seasonal to decadal time scales. Hence, it is key to understand physical processes that provide enhanced predictability beyond persistence of sea ice anomalies. The authors report on an analysis of natural variability of Arctic sea-ice from an energy budget perspective, using 15 CMIP5 climate models, and comparing these results to atmospheric and oceanic reanalyses data. We quantify the persistence of sea ice anomalies and the cross-correlation with the surface and top energy budget components. The Arctic energy balance components primarily indicate the important role of the seasonal sea-ice albedo feedback, in which sea-ice anomalies in the melt season reemerge in the growth season. This is a robust anomaly reemergence mechanism among all 15 climate models. The role of ocean lies mainly in storing heat content anomalies in spring, and releasing them in autumn. Ocean heat flux variations only play a minor role. The role of clouds is further investigated. We demonstrate that there is no direct atmospheric response of clouds to spring sea-ice anomalies, but a delayed response is evident in autumn. Hence, there is no cloud-ice feedback in late spring and summer, but there is a cloud-ice feedback in autumn, which strengthens the ice-albedo feedback. Anomalies in insolation are positively correlated with sea-ice variability. This is primarily a result of reduced multiple-reflection of insolation due to an albedo decrease. This effect counteracts the sea-ice albedo effect up to 50%. ERA-Interim and ORAS4 confirm the main findings from the climate models.

Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-07-01

Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0-200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500-1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500-1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30 % in retrievals of τ and effective radius reff, respectively. With the help of Δ L, an estimate of the distance to the ice edge is given, where the retrieval uncertainties due to 3-D radiative effects are negligible.

Norwegian Young Sea Ice Experiment (N-ICE) Field Campaign Report

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

Walden, V. P.; Hudson, S. R.; Cohen, L.

The Norwegian Young Sea Ice (N-ICE) experiment was conducted aboard the R/V Lance research vessel from January through June 2015. The primary purpose of the experiment was to better understand thin, first-year sea ice. This includes understanding of how different components of the Arctic system affect sea ice, but also how changing sea ice affects the system. A major part of this effort is to characterize the atmospheric conditions throughout the experiment. A micropulse lidar (MPL) (S/N: 108) was deployed from the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility as part of the atmospheric suitemore » of instruments. The MPL operated successfully throughout the entire experiment, acquiring data from 21 January 2015 through 23 June 2015. The MPL was the essential instrument for determining the phase (water, ice or mixed) of the lower-level clouds over the sea ice. Data obtained from the MPL during the N-ICE experiment show large cloud fractions over young, thin Arctic sea ice from January through June 2015 (north of Svalbard). The winter season was characterized by frequent synoptic storms and large fluctuations in the near-surface temperature. There was much less synoptic activity in spring and summer as the near-surface temperature rose to 0 C. The cloud fraction was lower in winter (60%) than in the spring and summer (80%). Supercooled liquid clouds were observed for most of the deployment, appearing first in mid-February. Spring and summer clouds were characterized by low, thick, uniform clouds.« less

High-frequency and meso-scale winter sea-ice variability in the Southern Ocean in a high-resolution global ocean model

NASA Astrophysics Data System (ADS)

Stössel, Achim; von Storch, Jin-Song; Notz, Dirk; Haak, Helmuth; Gerdes, Rüdiger

2018-03-01

This study is on high-frequency temporal variability (HFV) and meso-scale spatial variability (MSV) of winter sea-ice drift in the Southern Ocean simulated with a global high-resolution (0.1°) sea ice-ocean model. Hourly model output is used to distinguish MSV characteristics via patterns of mean kinetic energy (MKE) and turbulent kinetic energy (TKE) of ice drift, surface currents, and wind stress, and HFV characteristics via time series of raw variables and correlations. We find that (1) along the ice edge, the MSV of ice drift coincides with that of surface currents, in particular such due to ocean eddies; (2) along the coast, the MKE of ice drift is substantially larger than its TKE and coincides with the MKE of wind stress; (3) in the interior of the ice pack, the TKE of ice drift is larger than its MKE, mostly following the TKE pattern of wind stress; (4) the HFV of ice drift is dominated by weather events, and, in the absence of tidal currents, locally and to a much smaller degree by inertial oscillations; (5) along the ice edge, the curl of the ice drift is highly correlated with that of surface currents, mostly reflecting the impact of ocean eddies. Where ocean eddies occur and the ice is relatively thin, ice velocity is characterized by enhanced relative vorticity, largely matching that of surface currents. Along the ice edge, ocean eddies produce distinct ice filaments, the realism of which is largely confirmed by high-resolution satellite passive-microwave data.

Widespread Moulin Formation During Supraglacial Lake Drainages in Greenland

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

Hoffman, Matthew J.; Perego, Mauro; Andrews, Lauren C.

Moulins permit access of surface meltwater to the glacier bed, causing basal lubrication and ice speedup in the ablation zone of western Greenland during summer. In spite of the substantial impact of moulins on ice dynamics, the conditions under which they form are poorly understood. We assimilate a time series of ice surface velocity from a network of eleven Global Positioning System receivers into an ice sheet model to estimate ice sheet stresses during winter, spring, and summer in a ~30 × 10 km region. Surface-parallel von Mises stress increases slightly during spring speedup and early summer, sufficient to allowmore » formation of 16% of moulins mapped in the study area. Conversely, 63% of moulins experience stresses over the tensile strength of ice during a short (hours) supraglacial lake drainage event. Lake drainages appear to control moulin density, which is itself a control on subglacial drainage efficiency and summer ice velocities.« less

Widespread Moulin Formation During Supraglacial Lake Drainages in Greenland

DOE PAGES

Hoffman, Matthew J.; Perego, Mauro; Andrews, Lauren C.; ...

2018-01-17

Moulins permit access of surface meltwater to the glacier bed, causing basal lubrication and ice speedup in the ablation zone of western Greenland during summer. In spite of the substantial impact of moulins on ice dynamics, the conditions under which they form are poorly understood. We assimilate a time series of ice surface velocity from a network of eleven Global Positioning System receivers into an ice sheet model to estimate ice sheet stresses during winter, spring, and summer in a ~30 × 10 km region. Surface-parallel von Mises stress increases slightly during spring speedup and early summer, sufficient to allowmore » formation of 16% of moulins mapped in the study area. Conversely, 63% of moulins experience stresses over the tensile strength of ice during a short (hours) supraglacial lake drainage event. Lake drainages appear to control moulin density, which is itself a control on subglacial drainage efficiency and summer ice velocities.« less

Widespread Moulin Formation During Supraglacial Lake Drainages in Greenland

NASA Astrophysics Data System (ADS)

Hoffman, Matthew J.; Perego, Mauro; Andrews, Lauren C.; Price, Stephen F.; Neumann, Thomas A.; Johnson, Jesse V.; Catania, Ginny; Lüthi, Martin P.

2018-01-01

Moulins permit access of surface meltwater to the glacier bed, causing basal lubrication and ice speedup in the ablation zone of western Greenland during summer. Despite the substantial impact of moulins on ice dynamics, the conditions under which they form are poorly understood. We assimilate a time series of ice surface velocity from a network of eleven Global Positioning System receivers into an ice sheet model to estimate ice sheet stresses during winter, spring, and summer in a ˜30 × 10 km region. Surface-parallel von Mises stress increases slightly during spring speedup and early summer, sufficient to allow formation of 16% of moulins mapped in the study area. In contrast, 63% of moulins experience stresses over the tensile strength of ice during a short (hours) supraglacial lake drainage event. Lake drainages appear to control moulin density, which is itself a control on subglacial drainage efficiency and summer ice velocities.

Seasonal southern hemisphere multi-variable reflection of the southern annular mode in atmosphere and ocean reanalyses

NASA Astrophysics Data System (ADS)

Zhang, Zhaoru; Uotila, Petteri; Stössel, Achim; Vihma, Timo; Liu, Hailong; Zhong, Yisen

2018-02-01

Variations of southern hemisphere (SH) climate variables are often linked to the southern annular mode (SAM) variability. We examined such linkage by seasons using state-of-the-art atmosphere and ocean/sea-ice reanalyses. The associated SAM related anomaly (SRA) fields of the climate variables, denoting anomalies corresponding to the same variation in SAM, are overall consistent across the reanalyses. Among the atmospheric products, 20CRV2 differs from ERA-interim and CFSR in the sea-level pressure SRAs over the Amundsen Sea, resulting in less warming over the Antarctic Peninsula. Among the ocean reanalyses, ORAP5 and C-GLORS exhibit the largest consistency. The major difference between them and the lower-resolution CFSR and SODA reanalyses is deeper penetration of anomalous meridional currents. Compared to the other ocean reanalyses, CFSR exhibits stronger and spatially more coherent surface-current SRAs, resulting in greater SRAs of sea-ice motion and ice thickness along the ice edges. The SRAs of sensible and total surface heat fluxes are reduced in CFSR due to ocean-atmosphere coupling. Significant sea-ice concentration SRAs are present on the west side of peninsulas along the east Antarctica coast in spring and winter, most notably in ORAP5 and C-GLORS, implying changes in new-ice production and shelf-water formation. Most atmosphere and ocean variables manifest an annular SRA pattern in summer and a non-annular pattern in the other seasons, with a wavenumber-3 structure strongest in autumn and weakest in summer. The wavenumber-3 structure should be related to the zonal wave three pattern of the SH circulation, the relation of which to SAM needs further exploration.

Skillful Spring Forecasts of September Arctic Sea Ice Extent Using Passive Microwave Data

NASA Technical Reports Server (NTRS)

Petty, A. A.; Schroder, D.; Stroeve, J. C.; Markus, Thorsten; Miller, Jeffrey A.; Kurtz, Nathan Timothy; Feltham, D. L.; Flocco, D.

2017-01-01

In this study, we demonstrate skillful spring forecasts of detrended September Arctic sea ice extent using passive microwave observations of sea ice concentration (SIC) and melt onset (MO). We compare these to forecasts produced using data from a sophisticated melt pond model, and find similar to higher skill values, where the forecast skill is calculated relative to linear trend persistence. The MO forecasts shows the highest skill in March-May, while the SIC forecasts produce the highest skill in June-August, especially when the forecasts are evaluated over recent years (since 2008). The high MO forecast skill in early spring appears to be driven primarily by the presence and timing of open water anomalies, while the high SIC forecast skill appears to be driven by both open water and surface melt processes. Spatial maps of detrended anomalies highlight the drivers of the different forecasts, and enable us to understand regions of predictive importance. Correctly capturing sea ice state anomalies, along with changes in open water coverage appear to be key processes in skillfully forecasting summer Arctic sea ice.

Topologically Nontrivial Magnon Bands in Artificial Square Spin Ices with Dzyaloshinskii-Moriya Interaction

NASA Astrophysics Data System (ADS)

Iacocca, Ezio; Heinonen, Olle

2017-09-01

Systems that exhibit topologically protected edge states are interesting both from a fundamental point of view as well as for potential applications, the latter because of the absence of backscattering and robustness to perturbations. It is desirable to be able to control and manipulate such edge states. Here, we show that artificial square ices can incorporate both features: an interfacial Dzyaloshinskii-Moriya interaction gives rise to topologically nontrivial magnon bands, and the equilibrium state of the spin ice is reconfigurable with different configurations having different magnon dispersions and topology. The topology is found to develop as odd-symmetry bulk and edge magnon bands approach each other so that constructive band inversion occurs in reciprocal space. Our results show that topologically protected bands are supported in square spin ices.

Comparison of aerosol effects on simulated spring and summer hailstorm clouds

NASA Astrophysics Data System (ADS)

Yang, Huiling; Xiao, Hui; Guo, Chunwei; Wen, Guang; Tang, Qi; Sun, Yue

2017-07-01

Numerical simulations are carried out to investigate the effect of cloud condensation nuclei (CCN) concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are: (1) The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration; (2) Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles; (3) As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail; (4) When the CCN concentration increases, the amount of total precipitation lessens, while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of ice-phase precipitation. The differences between the two storms include: (1) An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case; (2) Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case; (3) An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.

Optimizing Observations of Sea Ice Thickness and Snow Depth in the Arctic

DTIC Science & Technology

2014-09-30

changes in the thickness of sea ice, glaciers , and ice sheets. These observations are critical for predicting the response of Earth’s polar ice to...Arctic Sea Ice Conditions in Spring 2009 - 2013 Prior to Melt , Geophys. Res. Lett., 40, 5888-5893, doi: 10.1002/2013GL058011. [published, refereed

Enhanced wintertime greenhouse effect reinforcing Arctic amplification and initial sea-ice melting.

PubMed

Cao, Yunfeng; Liang, Shunlin; Chen, Xiaona; He, Tao; Wang, Dongdong; Cheng, Xiao

2017-08-16

The speeds of both Arctic surface warming and sea-ice shrinking have accelerated over recent decades. However, the causes of this unprecedented phenomenon remain unclear and are subjects of considerable debate. In this study, we report strong observational evidence, for the first time from long-term (1984-2014) spatially complete satellite records, that increased cloudiness and atmospheric water vapor in winter and spring have caused an extraordinary downward longwave radiative flux to the ice surface, which may then amplify the Arctic wintertime ice-surface warming. In addition, we also provide observed evidence that it is quite likely the enhancement of the wintertime greenhouse effect caused by water vapor and cloudiness has advanced the time of onset of ice melting in mid-May through inhibiting sea-ice refreezing in the winter and accelerating the pre-melting process in the spring, and in turn triggered the positive sea-ice albedo feedback process and accelerated the sea ice melting in the summer.

Arctic atmospheric preconditioning: do not rule out shortwave radiation just yet

NASA Astrophysics Data System (ADS)

Sedlar, J.

2017-12-01

Springtime atmospheric preconditioning of Arctic sea ice for enhanced or buffered sea ice melt during the subsequent melt year has received considerable research focus in recent years. A general consensus points to enhanced poleward atmospheric transport of moisture and heat during spring, effectively increasing the emission of longwave radiation to the surface. Studies have essentially ruled out the role of shortwave radiation as an effective preconditioning mechanism because of the relatively weak incident solar radiation and high surface albedo from sea ice and snow during spring. These conclusions, however, are derived primarily from atmospheric reanalysis data, which may not always represent an accurate depiction of the Arctic climate system. Here, observations of top of atmosphere radiation from state of the art satellite sensors are examined and compared with reanalysis and climate model data to examine the differences in the spring radiative budget over the Arctic Ocean for years with extreme low/high ice extent at the end of the ice melt season (September). Distinct biases are observed between satellite-based measurements and reanalysis/models, particularly for the amount of shortwave radiation trapped (warming effect) within the Arctic climate system during spring months. A connection between the differences in reanalysis/model surface albedo representation and the albedo observed by satellite is discussed. These results suggest that shortwave radiation should not be overlooked as a significant contributing mechanism to springtime Arctic atmospheric preconditioning.

Persistence of bacterial and archaeal communities in sea ice through an Arctic winter

PubMed Central

Collins, R Eric; Rocap, Gabrielle; Deming, Jody W

2010-01-01

The structure of bacterial communities in first-year spring and summer sea ice differs from that in source seawaters, suggesting selection during ice formation in autumn or taxon-specific mortality in the ice during winter. We tested these hypotheses by weekly sampling (January–March 2004) of first-year winter sea ice (Franklin Bay, Western Arctic) that experienced temperatures from −9°C to −26°C, generating community fingerprints and clone libraries for Bacteria and Archaea. Despite severe conditions and significant decreases in microbial abundance, no significant changes in richness or community structure were detected in the ice. Communities of Bacteria and Archaea in the ice, as in under-ice seawater, were dominated by SAR11 clade Alphaproteobacteria and Marine Group I Crenarchaeota, neither of which is known from later season sea ice. The bacterial ice library contained clones of Gammaproteobacteria from oligotrophic seawater clades (e.g. OM60, OM182) but no clones from gammaproteobacterial genera commonly detected in later season sea ice by similar methods (e.g. Colwellia, Psychrobacter). The only common sea ice bacterial genus detected in winter ice was Polaribacter. Overall, selection during ice formation and mortality during winter appear to play minor roles in the process of microbial succession that leads to distinctive spring and summer sea ice communities. PMID:20192970

CO2 flux over young and snow-covered Arctic pack ice in winter and spring

NASA Astrophysics Data System (ADS)

Nomura, Daiki; Granskog, Mats A.; Fransson, Agneta; Chierici, Melissa; Silyakova, Anna; Ohshima, Kay I.; Cohen, Lana; Delille, Bruno; Hudson, Stephen R.; Dieckmann, Gerhard S.

2018-06-01

Rare CO2 flux measurements from Arctic pack ice show that two types of ice contribute to the release of CO2 from the ice to the atmosphere during winter and spring: young, thin ice with a thin layer of snow and older (several weeks), thicker ice with thick snow cover. Young, thin sea ice is characterized by high salinity and high porosity, and snow-covered thick ice remains relatively warm ( > -7.5 °C) due to the insulating snow cover despite air temperatures as low as -40 °C. Therefore, brine volume fractions of these two ice types are high enough to provide favorable conditions for gas exchange between sea ice and the atmosphere even in mid-winter. Although the potential CO2 flux from sea ice decreased due to the presence of the snow, the snow surface is still a CO2 source to the atmosphere for low snow density and thin snow conditions. We found that young sea ice that is formed in leads without snow cover produces CO2 fluxes an order of magnitude higher than those in snow-covered older ice (+1.0 ± 0.6 mmol C m-2 day-1 for young ice and +0.2 ± 0.2 mmol C m-2 day-1 for older ice).

Bio-optical properties of Arctic drift ice and surface waters north of Svalbard from winter to spring

NASA Astrophysics Data System (ADS)

Kowalczuk, Piotr; Meler, Justyna; Kauko, Hanna M.; Pavlov, Alexey K.; Zabłocka, Monika; Peeken, Ilka; Dybwad, Christine; Castellani, Giulia; Granskog, Mats A.

2017-06-01

We have quantified absorption by CDOM, aCDOM(λ), particulate matter, ap(λ), algal pigments, aph(λ), and detrital material, aNAP(λ), coincident with chlorophyll a in sea ice and surface waters in winter and spring 2015 in the Arctic Ocean north of Svalbard. The aCDOM(λ) was low in contrast to other regions of the Arctic Ocean, while ap(λ) has the largest contribution to absorption variability in sea ice and surface waters. ap(443) was 1.4-2.8 times and 1.3-1.8 times higher than aCDOM(443) in surface water and sea ice, respectively. aph(λ) contributed 90% and 81% to ap(λ), in open leads and under-ice waters column, and much less (53%-74%) in sea ice, respectively. Both aCDOM(λ) and ap(λ) followed closely the vertical distribution of chlorophyll a in sea ice and the water column. We observed a tenfold increase of the chlorophyll a concentration and nearly twofold increase in absorption at 443 nm in sea ice from winter to spring. The aCDOM(λ) dominated the absorption budget in the UV both in sea ice and surface waters. In the visible range, absorption was dominated by aph(λ), which contributed more than 50% and aCDOM(λ), which contributed 43% to total absorption in water column. Detrital absorption contributed significantly (33%) only in surface ice layer. Algae dynamics explained more than 90% variability in ap(λ) and aph(λ) in water column, but less than 70% in the sea ice. This study presents detailed absorption budget that is relevant for modeling of radiative transfer and primary production.

Spring in Inca City I

NASA Image and Video Library

2014-11-13

Every winter a layer of carbon dioxide ice-or, dry ice-condenses in the Southern polar region, forming a seasonal polar cap less than 1 meter deep. Early in the spring the ice layer begins to sublimate (going directly from a solid to gas) from the top and bottom of the ice layer. Under the ice gas pressure builds up until a weak spot in the ice layer ruptures. The gas rushes out and as it escapes it erodes a bit of the surface. Fine particles are carried by the gas to the top of the ice and then fall out in fan-shaped deposits. The direction of the fan shows the direction either of the wind or down the slope. If the wind is not blowing a dark blotch settles around the spot the gas escaped. This region is known informally as Inca City, and it has a series of distinctive ridges. On the floor between the ridges are radially organized channels, known colloquially as spiders, more formally called "araneiforms." The channels have been carved in the surface over many years by the escaping pressurized gas. Every spring they widen just a bit. This was the first image to be acquired by NASA Mars Reconnaissance Orbiter after the sun rose on Inca City, marking the end to polar night. A few fans are visible emerging from the araneiforms. http://photojournal.jpl.nasa.gov/catalog/PIA18892

Forecast Tools for Alaska River Ice Breakup Timing and Severity

NASA Astrophysics Data System (ADS)

Moran, E. H.; Lindsey, S.; van Breukelen, C. M.; Thoman, R.

2016-12-01

Spring Breakup on the large interior rivers in Alaska means a time of nervous anticipation for many of the residents in the villages alongside those rivers. On the Yukon and Kuskokwim Rivers the record flood for most villages occurred as a result of ice jams that backed up water and dump truck sized ice floes into the village. Those floods can occur suddenly and can literally wipe out a village. The challenge is that with a limited observation network (3 automated USGS gages along the 1200 miles of the Yukon River flowing through Alaska) and the inherently transient nature of ice jam formation, prediction of the timing and severity of these events has been a tremendous challenge. Staff at the Alaska Pacific River Forecast Center as well as the Alaska Region Climate Program Manager have been developing more quantitative tools to attempt to provide a longer lead time for villages to prepare for potentially devastating flooding. In the past, a very qualitative assessment of the primary drivers of Spring Breakup (snow pack, river ice thickness and forecast spring weather) have led to the successful identification of years when flood severity was likely to be elevated or significantly decreased. These qualitative assessments have also allowed the forecasting of the probability of either a thermal or a dynamic breakup. But there has continued to be a need for an objective tool that can handle weather patterns that border on the tails of the climatic distributions as well as the timing and flood potential from weather patterns that are closer to the median of the distribution. Over the past 8 years there have been a significant number of years with anomalous spring weather patterns including cold springs followed by rapid warmups leading to record flooding from ice jams during spring breakup (2009, 2013), record late breakup (2013), record early breakup (2016), record high snowfall (2012), record snowmelt and aufeis flooding (2015) and record low snowfall (2015). The need for improved tools that can handle these events over the full breadth of the distribution has never been greater. This talk will describe efforts to incorporate climate signals into the spring breakup outlook and show results of some temperature based indices as an indicator of breakup timing.

Experimental investigation of passive infrared ice detection for helicopter applications

NASA Technical Reports Server (NTRS)

Dershowitz, Adam; Hansman, R. John, Jr.

1991-01-01

A technique is proposed to remotely detect rotor icing on helicopters. Using passive infrared (IR) thermometry it is possible to detect the warming caused by latent heat released as supercooled water freezes. During icing, the ice accretion region on the blade leading edge will be warmer than the uniced trailing edge resulting in a chordwise temperature profile characteristic of icing. Preliminary tests were conducted on a static model in the NASA Icing Research Tunnel for a variety of wet (glaze) and dry (rime) ice conditions. The characteristic chordwise temperature profiles were observed with an IR thermal video system and confirmed with thermocouple measurements. A prototype detector system was built consisting of a single point IR pyrometer, and experiments were run on a small scale rotor model. Again the characteristic chordwise temperature profiles were observed during icing, and the IR system was able to remotely detect icing. Based on the static and subscale rotor tests the passive IR technique is promising for rotor ice detection.

Experimental investigation of passive infrared ice detection for helicopter applications

NASA Technical Reports Server (NTRS)

Dershowitz, Adam; Hansman, R. John, Jr.

1991-01-01

A technique is proposed to remotely detect rotor icing on helicopters. Using passive infrared (IR) thermometry, it is possible to detect the warming caused by latent heat released as supercooled water freezes. During icing, the ice accretion region on the blade leading edge will be warmer than the uniced trailing edge, resulting in a chordwise temperature profile characteristic of icing. Preliminary tests were conducted on a static model in the NASA Icing Research Tunnel for a variety of wet (glaze) and dry (rime) ice conditions. The characteristic chordwise temperature profiles were observed with an IR thermal video system and confirmed with thermocouple measurements. A prototype detector system was built consisting of a single point IR pyrometer. Experiments were run on a small scale rotor model. Again, the characteristic chordwise temperature profiles were observed during icing, and the IR system was able to remotely detect icing. Based on the static and subscale rotor tests, the passive IR technique is promising for rotor ice detection.

Passive microwave observations of the Wedell Sea during austral winter and early spring

NASA Technical Reports Server (NTRS)

Grenfell, T. C.; Comiso, J. C.; Lange, M. A.; Eicken, H.; Wensnahan, M. R.

1994-01-01

The results of multispectral passive microwave observations (6.7 to 90-GHz) are presented from the cruises of the FS Polarstern in the Weddell Sea from July to December 1986. This paper includes primarily the analysis of radiometric observations taken at ice station sites. Averaged emissivity spectra for first-year (FY) ice were relatively constant throughout the experiment and were not statistically different from FY ice signatures in the Arctic. Detailed ice characterization was carried out at each site to compare the microwave signatures of the ice with the physical properties. Absorption optical depths of FY ice were found to be sufficiently high that only the structure in the upper portions of the ice contributed significantly to interstation emissivity variations. The emissivities at 90-GHz, e(90), had the greatest variance. Both e(90) at vertical polarization and GR(sub e)(90, 18.7)(defined as (e(sub V)(90)-e(sub V)(18.7))/e(sub V)(90 + e(sub V)(18.7)) depended on the scattering optical depth which is a function of the snow grain diameter and layer thickness. The variance showed a latitude dependence and is probably due to an increase in the strength of snow metamorphism nearer the northern edge of the ice pack. The contribution of variations of near-surface brine volume to the emissivity was not significant over the range of values encountered at the station sites. Emissivity spectra are presented for a range of thin ice types. Unsupervised principal component analysis produced three significant eigenvectors and showed a separation among four different surface types: open water, thin ice, FY ice, and FY ice with a thick snow cover. A comparison with SMMR satellite data showed that average ice concentrations derived from the ship's ice watch log were consistent with the satellite concentrations. The surface based emissivities for FY ice were also compared with emissivities calculated from scanning multichannel microwave radiometer (SMMR) satellite radiances. Best agreement was found at 6.7 and 10-GHz, while at 18 and 37-GHz, SMMR emissivities were slightly lower than surface based results. For the three lower frequencies agreement was found within a confidence limit of 95% and for 37-GHz within about 90%.

The Norwegian remote sensing experiment (Norsex) in a marginal ice zone

NASA Technical Reports Server (NTRS)

Farrelly, B.; Johannessen, J.; Johannessen, O. M.; Svendson, E.; Kloster, K.; Horjen, I.; Campbell, W. J.; Crawford, J.; Harrington, R.; Jones, L.

1981-01-01

Passive and active microwave measurements from surface based, airborne, and satellite instruments were obtained together with surface observations northwest of Svalbard. Emissivities of different ice patches in the ice edge region over the spectral range from 4.9 to 94 GHz are presented. The combination of a 6.6 GHz microwave radiometer with a 14.6 GHz scatterometer demonstrates the usefulness of an active/passive system in ice classification. A variety of mesoscale features under different meteorological conditions is revealed by a 1.36 GHz synthetic aperture radar. Ice edge location by Nimbus 7 scanning multifrequency microwave radiometer is shown accurate to 10 km when the 37 GHz horizontal polarized channel is used.

Year-Round Pack Ice in the Weddell Sea, Antarctica: Response and Sensitivity to Atmospheric and Oceanic Forcing

NASA Technical Reports Server (NTRS)

Geiger, Cathleen A.; Ackley, Stephen F.; Hibler, William D., III

1997-01-01

Using a dynamic-thermodynamic numerical sea-ice model, external oceanic and atmospheric forcings on sea ice in the Weddell Sea are examined to identify physical processes associated with the seasonal cycle of pack ice, and to identify further the parameters that coupled models need to consider in predicting the response of the pack ice to climate and ocean-circulation changes. In agreement with earlier studies, the primary influence on the winter ice-edge maximum extent is air temperature. Ocean heat flux has more impact on the minimum-ice-edge extent and in reducing pack-ice thickness, especially in the eastern-Weddell Sea. Low relative humidity enhances ice growth in thin ice and open-water regions, producing a more realistic ice edge along the coastal areas of the western-Weddell Sea where dry continental air has an impact. The modeled extent of the Weddell summer pack is equally sensitive to ocean heat flux and atmospheric relative humidity variations with the more dynamic responses being from the atmosphere. Since the atmospheric regime in the eastern Weddell is dominated by marine intrusions from lower latitudes, with high humidity already, it is unlikely that either the moisture trans- port could be further raised or that it could be significantly lowered because of its distance from the continent (the lower humidity source). Ocean heat-transport variability is shown to lead to overall ice thinning in the model response and is a known feature of the actual system, as evidenced by the occurrence of the Weddell Polynya in the mid 1970s.

The reproductive success of lake herring in habitats near shipping channels and ice-breaking operations in the St. Marys River, Michigan, USA

USGS Publications Warehouse

Blouin, Marc A.; Kostich, M.M.; Todd, T.N.; Savino, J.F.

1998-01-01

A study of the reproductive success of lake herring (Coregonus artedi) in the St. Marys River was conducted in the winters and springs of 1994, 1995, and 1996. The St. Marys River connects Lake Superior to the lower Great Lakes making it an important route for ship traffic. Recent pressure by commercial carriers to extend the shipping season by breaking ice earlier in spring, has raised concerns over the possible adverse effects on lake herring reproduction in the river caused by increased turbidity associated with vessel passage. Lake herring spawn in fall and their eggs overwinter under ice cover on the bottom of the St. Marys River. Hatching occurs in the spring after ice-out when water temperatures rise. Specialized incubators were used to hold fertilized lake herring eggs at four experimental sites, chosen to represent the range of various bottom substrate types of the St. Marys River from boulder rock reefs to soft sediments. In winter, incubators were placed under the ice on the bottom of the river at three sites each year. After ice-out, sites were relocated, and the incubators were retrieved and opened to determine the number of live and dead lake herring eggs and larvae. Survival was consistent from year to year at each site with the lowest survival percentage found at the site with the softest sediments, directly adjacent to the St. Marys River channel and downstream of the mouth of the Charlotte River. River bottom type and geographic location were the most important factors in determining egg survival. Sampling for indigenous larval lake herring was done throughout the spring hatching season in the areas adjacent to the incubator sites using nets and a diver-operated suction sampler. Result indicate that a small population (3) of larval lake herring was present throughout the sampling areas during the springs of 1994, 1995, and 1996 in the St. Marys River.

Spring snow conditions on Arctic sea ice north of Svalbard, during the Norwegian Young Sea ICE (N-ICE2015) expedition

NASA Astrophysics Data System (ADS)

Gallet, Jean-Charles; Merkouriadi, Ioanna; Liston, Glen E.; Polashenski, Chris; Hudson, Stephen; Rösel, Anja; Gerland, Sebastian

2017-10-01

Snow is crucial over sea ice due to its conflicting role in reflecting the incoming solar energy and reducing the heat transfer so that its temporal and spatial variability are important to estimate. During the Norwegian Young Sea ICE (N-ICE2015) campaign, snow physical properties and variability were examined, and results from April until mid-June 2015 are presented here. Overall, the snow thickness was about 20 cm higher than the climatology for second-year ice, with an average of 55 ± 27 cm and 32 ± 20 cm on first-year ice. The average density was 350-400 kg m-3 in spring, with higher values in June due to melting. Due to flooding in March, larger variability in snow water equivalent was observed. However, the snow structure was quite homogeneous in spring due to warmer weather and lower amount of storms passing over the field camp. The snow was mostly consisted of wind slab, faceted, and depth hoar type crystals with occasional fresh snow. These observations highlight the more dynamic character of evolution of snow properties over sea ice compared to previous observations, due to more variable sea ice and weather conditions in this area. The snowpack was isothermal as early as 10 June with the first onset of melt clearly identified in early June. Based on our observations, we estimate than snow could be accurately represented by a three to four layers modeling approach, in order to better consider the high variability of snow thickness and density together with the rapid metamorphose of the snow in springtime.

Changes in Spring Vegetation Activity over Eurasian Boreal Forest Associated with Reduction of Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Koh, Y.; Jeong, J. H.; Kim, B. M.; Park, T. W.; Jeong, S. J.

2017-12-01

Vegetation activities over the high-latitude in the Northern-Hemisphere are known to be very sensitive to climate change, which can, in turn, affect the entire climate system. This is one of the important feedback effects on global climate change. In this study, we have detected a declining trend of vegetation index in the boreal forest (Taiga) region of Eurasia in early spring from the late 1990s, and confirmed that the cause is closely related to the decrease in winter temperature linked to the Arctic sea ice change. The reduction of Arctic sea ice induces weakening of the Polar vortex around the Arctic, which has a chilling effect throughout Eurasia until the early spring (March) by strengthening the Siberian high in the Eurasian continent. The decrease of vegetation growth is caused by the extreme cold phenomenon directly affecting the growth of the boreal trees. To verify this, we used vegetation-climate coupled models to investigate climate-vegetation sensitivity to sea ice reduction. As a result, when the Arctic sea ice decreased in the model simulation, the vegetation index of the boreal forest, especially needleleaf evergreen trees, decreased as similarly detected by observations.

Life Beneath Glacial Ice - Earth(!) Mars(?) Europa(?)

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Grasby, Stephen E.; Longazo, Teresa G.; Lisle, John T.; Beauchamp, Benoit

2002-01-01

We are investigating a set of cold springs that deposit sulfur and carbonate minerals on the surface of a Canadian arctic glacier. The spring waters and mineral deposits contain microorganisms, as well as clear evidence that biological processes mediate subglacial chemistry, mineralogy, and isotope fractionation . The formation of native sulphur and associated deposits are related to bacterially mediated reduction and oxidation of sulphur below the glacier. A non-volcanic, topography driven geothermal system, harboring a microbiological community, operates in an extremely cold environment and discharges through solid ice. Microbial life can thus exist in isolated geothermal refuges despite long-term subfreezing surface conditions. Earth history includes several periods of essentially total glaciation. lee in the near subsurface of Mars may have discharged liquid water in the recent past Cracks in the ice crust of Europa have apparently allowed the release of water to the surface. Chemolithotrophic bacteria, such as those in the Canadian springs, could have survived beneath the ice of "Snowball Earth", and life forms with similar characteristics might exist beneath the ice of Mars or Europa. Discharges of water from such refuges may have brought to the surface living microbes, as well as longlasting chemical, mineralogical, and isotopic indications of subsurface life.

SAR and passive microwave observations of the Odden during Mizex '87

NASA Technical Reports Server (NTRS)

Sutherland, Laura L.; Shuchman, Robert A.; Gloersen, Per; Johannessen, Johnny A.; Johannessen, Ola M.

1989-01-01

The Odden, a protuberance of sea ice in the Greenland Sea Basin, was studied using the NIMBUS-7 scanning multichannel microwave radiometer (SMMR) satellite and an X-band (3 cm) synthetic aperture radar (SAR) aircraft. The sea ice, meteorological, and oceanographic conditions within the northern portion of the Odden were also studied in March and April 1987. The SMMR data, which were first validated with in situ ship measurements and the SAR data, showed rapid 2-4 day oscillations of the Odden ice edge. The oscillations at 74-75 deg N were several hundred kilometers in extent. The rapid oscillation of the Odden does not appear to be a result of wind-induced ice drift, but rather results from the rapid formation of thin ice off the main ice edge.

Phytoplankton in the Beaufort and Chukchi Seas: Distributions, Dynamics and Environmental Forcing

NASA Technical Reports Server (NTRS)

Wang, Jian; Cota, Glenn F.; Comiso, Josefino C.

2005-01-01

Time-series of remotely sensed distributions of phytoplankton, sea ice, surface temperature, albedo, and clouds were examined to evaluate the impact of the variability of environmental conditions and physical forcing on the phytoplankton distribution in the Beaufort and Chukchi Seas. Large-scale distributions of these parameters were studied for the first time using weekly and monthly composites from April 1998 through September 2002. The basic data set used in this study are phytoplankton pigment concentration derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), ice concentration obtained from the Special Sensor Microwave Imager (SSM/I) and surface temperature, cloud cover, and albedo derived from the Advanced Very High Resolution Radiometer (AVHRR). Seasonal variations of the sea ice cover was observed to be the dominant environmental factor as the ice edge blooms followed the retreating marginal ice zones northward. Blooms were most prominent in the southwestern Chukchi Sea, and were especially persistent immediately north of the Bering Strait in nutrient- rich Anadyr water and in some fronts. Chlorophyll concentrations are shown to increase from a nominal value during onset of melt in April to a maximum value in mid-spring or summer depending on location. Large interannual variability of ice cover and phytoplankton distributions was observed with the year 1998 being uniquely associated with an early season occurrence of a massive bloom. This is postulated to be caused in part by a rapid response of phytoplankton to an early retreat of the sea ice cover in the Beaufort Sea region. Correlation analyses showed relatively high negative correlation between chlorophyll and ice concentration with the correlation being highest in May, the correlation coefficient being -0.45. 1998 was also the warmest among the five years globally and the sea ice cover was least extensive in the Beaufort-Khukchi Sea region, partly because of the 1997-98 El Nino. Strong correlations were noted between ice extent and surface temperature, the correlation coefficient being highest at - 0.79 in April, during the onset of the bloom period

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling

DTIC Science & Technology

2015-09-30

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind- Wave Coupling Peter S. Guest (NPS Technical Contact) Naval...surface fluxes and ocean waves in coupled models in the Beaufort and Chukchi Seas. 2. Understand the physics of heat and mass transfer from the ocean...to the atmosphere. 3. Improve forecasting of waves on the open ocean and in the marginal ice zone. 2 OBJECTIVES 1. Quantifying the open-ocean

Bibliography on Cold Regions Science and Technology. Volume 40, Part 2, 1986

DTIC Science & Technology

1986-12-01

affecting teabird oc- currence in the Scotia and Weddell Seaa [1984, |> 119-121, eng] 40-22« Ice edges and seabird occurrence in Antarctica [1^36...catclunent[1989, p.Ul-147, eng] 40-2411 Brl>tM,E. Obacrvatioiu of plankton organianu obtained by bongo ueta during the Nove nber-December 1983 ice-edge...p.293-312, eng] 40-2510 Characteristics of marine icing in Canadian waten [1989, p.78-94, eng] 40-2498 Climatology of severe storms affecting

Sensitivity studies with a coupled ice-ocean model of the marginal ice zone

NASA Technical Reports Server (NTRS)

Roed, L. P.

1983-01-01

An analytical coupled ice-ocean model is considered which is forced by a specified wind stress acting on the open ocean as well as the ice. The analysis supports the conjecture that the upwelling dynamics at ice edges can be understood by means of a simple analytical model. In similarity with coastal problems it is shown that the ice edge upwelling is determined by the net mass flux at the boundaries of the considered region. The model is used to study the sensitivity of the upwelling dynamics in the marginal ice zone to variation in the controlling parameters. These parameters consist of combinations of the drag coefficients used in the parameterization of the stresses on the three interfaces atmosphere-ice, atmosphere-ocean, and ice-ocean. The response is shown to be sensitive to variations in these parameters in that one set of parameters may give upwelling while a slightly different set of parameters may give downwelling.

A 900-Year Diatom and Chrysophyte Record of Spring Mixing and Summer Stratification From Varved Lake Mina, West-Central Minnesota, USA

NASA Astrophysics Data System (ADS)

St. Jacques, J.; Cumming, B. F.; Smol, J. P.

2009-05-01

A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality data from the actual time of sediment deposition are used to interpret the high-resolution diatom and chrysophyte record of varved Lake Mina, west-central Minnesota, USA during AD 1116-2002. This direct algal seasonality information was obtained by a new technique of splitting varves into constituent winter-spring and summer lamina, and separately analyzing the siliceous algae in each layer. Analyses of integrated, continuous four-year diatom and chrysophyte samples from a sedimentary sequence show that the time period AD 1116-1478 (i.e. the Atlantic- centered Medieval Climate Anomaly (MCA)) was characterized by periods of vigorous and prolonged spring mixing, suggesting that ice-out occurred early. However, the warm summer temperatures in the MCA, particularly in a massive drought spanning AD 1300-1400, frequently caused the lake to stratify strongly, leading to nutrient depletion. During AD 1478-1870 (i.e. the Atlantic-centered Little Ice Age (LIA)), Lake Mina was characterized by weak spring circulation and increasing nutrient depletion, suggesting late ice-out conditions. Strong summer stratification and/or nutrient depletion in both time periods is shown by the occurrence of the nutrient-poor oligotrophic taxon Cyclotella pseudostelligera. The diatom and chrysophyte assemblages of the period of Euro-American settlement AD 1870-2002 show higher nutrient availability and increased spring mixing intensity, due to forest clearance and increasingly earlier ice-out (documented in regional historical records).

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.

Salmon on the Edge: Growth and Condition of Juvenile Chum and Pink Salmon in the Northeastern Bering Sea

NASA Astrophysics Data System (ADS)

McPhee, M. V.

2016-02-01

As the Arctic and Subarctic regions warm, Pacific salmon (Oncorhynchus spp.) are expected to expand their range northward during ice-free periods in the Bering and Chukchi seas. The oscillating control hypothesis, which describes energetic differences of primary consumers between ice-associated and pelagic production phases, provides a framework for understanding how juvenile salmon might respond to changing conditions at the northern edge of their marine range. Additionally, relationships between growth/condition and temperature, salinity and bottom depth will help identify marine habitats supporting growth at the Arctic-Subarctic interface. In this study, we used survey data from NOAA and Arctic Ecosystem Integrated Survey project to 1) compare growth and condition of juvenile pink (O. gorbuscha) and chum (O. keta) salmon in the NE Bering Sea between warm and cool spring phases, and 2) describe relationships between summer environmental conditions and juvenile salmon growth and condition from 2006 - 2010. Chum and pink salmon were shorter, and chum salmon exhibited greater energy density, in years with cool springs; however, no other aspects of size and condition differed significantly between phases. Over all years, longer and more energy dense individuals of both species were caught at stations with greater bottom depths and in cooler sea-surface temperatures. We found little evidence that chlorophyll-a explained much of the variation in size or condition. We used insulin-like growth factor-1 (IGF-1) concentration as an indicator of relative growth rate for fishes sampled in 2009-2012 and that found juvenile salmon exhibited higher IGF-1 concentrations in 2010-2012 than in 2009. IGF-1 concentrations tended to increase with SST in chum salmon and with bottom depth (a proxy for distance from shore) in pink salmon, but more years of data are needed to adequately describe the relationship of IGF with environmental conditions. This study, although descriptive in nature, provides a starting point for developing a mechanistic understanding of how Pacific salmon will respond to warming at the Arctic-Subarctic interface.

A passive infrared ice detection technique for helicopter applications

NASA Technical Reports Server (NTRS)

Dershowitz, Adam L.; Hansman, R. John, Jr.

1991-01-01

A technique has been developed, and successfully tested, to detect icing remotely on helicopter rotor blades. Using passive infrared (IR) thermometry it is possible to detect the warming caused by latent heat released as supercooled water freezes. During icing, the ice accretion region on the leading edge of the blade is found to be warmer than the uniced trailing edge resulting in a chordwise temperature profile characteristic of icing. Preliminary tests, using an IR Thermal video system, were conducted on a static model in the NASA Icing Research Tunnel (IRT) for a variety of wet (glaze) and dry (rime) ice conditions. A prototype detector system was built consisting of a single point IR pyrometer, and experiments were run on a small scale rotor model. Using this prototype detector, the characteristic chordwise temperature profiles were again observed for a range of icing conditions. Several signal processing methods were investigated, to allow automatic recognition of the icing signature. Additionally, several implementation issues were considered. Based on both the static and subscale rotor tests, where ice was successfully detected, the passive IR technique appears to be promising for rotor ice detection.

Icing Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48

NASA Technical Reports Server (NTRS)

Bidwell, Colin S.

2014-01-01

Icing calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated ice shapes were compared to experimental data generated in the NASA Glenn Icing Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D ice void density model which was developed to improve the prediction of swept wing ice shapes. Icing tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted mass agreed well with the experiment with an average difference of 12%. The LEWICE3D ice void density model under-predicted void density by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void density resulted in an over-prediction of ice area by an average of 115%. The LEWICE3D ice void density model produced a larger average area difference with experiment than the standard LEWICE density model, which doesn't account for the voids in the swept wing ice shape, (115% and 75% respectively) but it produced ice shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative ice shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void ice density model to the particle inertia parameter. The scallop features present on the ice shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void density model were tested. The changes improved the ice shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and icing conditions.

Icing Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48

NASA Technical Reports Server (NTRS)

Bidwell, Colin S.

2014-01-01

Icing calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated ice shapes were compared to experimental data generated in the NASA Glenn Icing Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D ice void density model which was developed to improve the prediction of swept wing ice shapes. Icing tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted mass agreed well with the experiment with an average difference of 12%. The LEWICE3D ice void density model under-predicted void density by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void density resulted in an over-prediction of ice area by an average of 115%. The LEWICE3D ice void density model produced a larger average area difference with experiment than the standard LEWICE density model, which doesn't account for the voids in the swept wing ice shape, (115% and 75% respectively) but it produced ice shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative ice shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void ice density model to the particle inertia parameter. The scallop features present on the ice shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void density model were tested. The changes improved the ice shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and icing conditions

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.

Unusual phytoplankton bloom phenology in the northern Greenland Sea during 2010

NASA Astrophysics Data System (ADS)

Qu, Bo; Gabric, Albert J.; Lu, Zhifeng; Li, Hehe; Zhao, Li

2016-12-01

Arctic marine ecosystems are disproportionately impacted by global warming. Sea ice plays an important role in the regional climate system and the loss of perennial sea ice has diverse ecological implications. Here we investigate the causes of an unusually early and strong phytoplankton bloom in the northern Greenland Sea (20°W-10°E, 75°N-80°N) during the 2010 season. In order to better understand the anomalous bloom in 2010, we examine the correlation between satellite-derived biomass and several possible environmental factors for the period 2003-2012. Results show that the timing of sea ice melt played an important role in promoting the growth of phytoplankton. Multivariate lagged regression analysis shows that phytoplankton biomass (CHL) is correlated with ice concentration (ICE) and ice melting, as well as sea surface temperature (SST) and photosynthetically active radiation (PAR). During 2010, the spring peak in biomass came much earlier and achieved a higher value than most other years in the satellite archive record, which was due to earlier and more extensive sea ice melt in that year. Relative lower SST and PAR in spring and early summer in year 2010 associated with a persistent negative North Atlantic Oscillation (NAO) index were possible drivers of the bloom. Wind direction changed from the southeast to southwest direction in spring, possibly transporting nutrient enriched melt runoff from glaciers on Greenland and other sources from the south to northern coastal regions.

South Polar Layers

NASA Image and Video Library

2016-08-25

Southern hemisphere spring has arrived at the south polar cap. The ice layers that make up the cap are easily seen in this image from NASA 2001 Mars Odyssey spacecraft. Southern hemisphere spring has arrived at the south polar cap. The ice layers that make up the cap are easily seen in this VIS image. Orbit Number: 64531 Latitude: -86.6334 Longitude: 97.7916 Instrument: VIS Captured: 2016-07-01 06:55 http://photojournal.jpl.nasa.gov/catalog/PIA20972

"Ice out": the contribution of citizen scientists to our understanding of climate change

NASA Astrophysics Data System (ADS)

Patterson, R. Timothy; Swindles, Graeme T.

2016-04-01

Long-term trends in spring 'ice out' dates (1836-2013) for twelve lakes in Maine, New Brunswick and New Hampshire, in eastern North America reveal a remarkable coherency across the region (rs=0.462-0.933, p<0.01). These data have been compiled since the early 19th century, primarily by amateur citizen scientists, for a variety of purposes, including determining fishing seasons, estimating the spring opening of ferry boat routes, community contests, and general curiosity. Ice out dates correlate closely with late-winter/early-spring, March-April (MA), instrumental temperature records from across the region (rs=0.488-0.816, p<0.01). This correlation permits use of ice out dates as a proxy to extend the shorter MA instrumental record (1876-2013). Mean ice out dates trended progressively earlier during the recovery from the Little Ice Age through to the 1940s, and gradually became later again through to the late 1970s, when ice out dates had returned to values more typical of the late nineteenth century. Post-1970's ice out dates resumed trending toward earlier dates, with the twenty-first century being characterized by the earliest ice out dates on record. Spectral and wavelet time series analysis indicate that ice out is influenced by several teleconnections including the Quasi-biennial Oscillation, El Niño-Southern Oscillation, North Atlantic Oscillation, Atlantic Multidecadal Oscillation as well as a significant correlation between inland lake records and the Arctic Oscillation. The relative influence of these teleconnections is variable with notable shifts occurring after ~1870, ~1925, and ~1980-2000. The intermittent expression of these cycles in the ice out and MA instrumental record is not only influenced by absolute changes in the intensity of the various teleconnections and other climate drivers, but by phase interference between teleconnections, which periodically damps the various signals.

Effects of sea-ice and biogeochemical processes and storms on under-ice water fCO2 during the winter-spring transition in the high Arctic Ocean: Implications for sea-air CO2 fluxes

NASA Astrophysics Data System (ADS)

Fransson, Agneta; Chierici, Melissa; Skjelvan, Ingunn; Olsen, Are; Assmy, Philipp; Peterson, Algot K.; Spreen, Gunnar; Ward, Brian

2017-07-01

We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter-to-spring data set includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m-2 d-1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m-2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant.

Generation of Fullspan Leading-Edge 3D Ice Shapes for Swept-Wing Aerodynamic Testing

NASA Technical Reports Server (NTRS)

Camello, Stephanie C.; Lee, Sam; Lum, Christopher; Bragg, Michael B.

2016-01-01

The deleterious effect of ice accretion on aircraft is often assessed through dry-air flight and wind tunnel testing with artificial ice shapes. This paper describes a method to create fullspan swept-wing artificial ice shapes from partial span ice segments acquired in the NASA Glenn Icing Reserch Tunnel for aerodynamic wind-tunnel testing. Full-scale ice accretion segments were laser scanned from the Inboard, Midspan, and Outboard wing station models of the 65% scale Common Research Model (CRM65) aircraft configuration. These were interpolated and extrapolated using a weighted averaging method to generate fullspan ice shapes from the root to the tip of the CRM65 wing. The results showed that this interpolation method was able to preserve many of the highly three dimensional features typically found on swept-wing ice accretions. The interpolated fullspan ice shapes were then scaled to fit the leading edge of a 8.9% scale version of the CRM65 wing for aerodynamic wind-tunnel testing. Reduced fidelity versions of the fullspan ice shapes were also created where most of the local three-dimensional features were removed. The fullspan artificial ice shapes and the reduced fidelity versions were manufactured using stereolithography.

Historical changes in lake ice-out dates as indicators of climate change in New England, 1850-2000

USGS Publications Warehouse

Hodgkins, G.A.; James, Ivan; Huntington, T.G.

2002-01-01

Various studies have shown that changes over time in spring ice-out dates can be used as indicators of climate change. Ice-out dates from 29 lakes in New England (USA) with 64 to 163 years of record were assembled and analysed for this study. Ice-out dates have become significantly earlier in New England since the 1800s. Changes in ice-out dates between 1850 and 2000 were 9 days and 16 days in the northern/mountainous and southern regions of New England respectively. The changes in the ice-out data over time were very consistent within each of the two regions of New England, and more consistent than four air-temperature records in each region. The ice-out dates of the two regions had a different response to changes in air temperature. The inferred late winter-early spring air-temperature warming in both regions of New England since 1850, based on linear regression analysis, was about 1.5 ??C. Published in 2002 by John Wiley & Sons, Ltd.

Decadal Bering Sea seascape change: consequences for Pacific walruses and indigenous hunters.

PubMed

Ray, G Carleton; Hufford, Gary L; Overland, James E; Krupnik, Igor; McCormick-Ray, Jerry; Frey, Karen; Labunski, Elizabeth

2016-01-01

The most significant factors currently affecting the Pacific walrus (Odobenus rosmarus divergens) population are climate change and consequent changes in sea-ice morphology and dynamics. This paper integrates recent physical sea-ice change in the Bering Sea with biological and ecological conditions of walruses in their winter-spring reproductive habitat. Historically, walrus in winter-spring depended on a critical mass of sea-ice habitat to optimize social networking, reproductive fitness, feeding behavior, migration, and energetic efficiency. During 2003-2013, our cross-disciplinary, multiscale analysis from shipboard observations, satellite imagery, and ice-floe tracking, reinforced by information from indigenous subsistence hunters, documented change of sea-ice structure from a plastic continuum to a "mixing bowl" of ice floes moving more independently. This fragmentation of winter habitat preconditions the walrus population toward dispersal mortality and will also negatively affect the availability of resources for indigenous communities. We urge an expanded research and management agenda that integrates walrus natural history and habitat more completely with changing sea-ice morphology and dynamics at multiple scales, while also meeting the needs of local communities.

An active bacterial community linked to high chl-a concentrations in Antarctic winter-pack ice and evidence for the development of an anaerobic sea-ice bacterial community.

PubMed

Eronen-Rasimus, Eeva; Luhtanen, Anne-Mari; Rintala, Janne-Markus; Delille, Bruno; Dieckmann, Gerhard; Karkman, Antti; Tison, Jean-Louis

2017-10-01

Antarctic sea-ice bacterial community composition and dynamics in various developmental stages were investigated during the austral winter in 2013. Thick snow cover likely insulated the ice, leading to high (<4 μg l -1 ) chlorophyll-a (chl-a) concentrations and consequent bacterial production. Typical sea-ice bacterial genera, for example, Octadecabacter, Polaribacter and Glaciecola, often abundant in spring and summer during the sea-ice algal bloom, predominated in the communities. The variability in bacterial community composition in the different ice types was mainly explained by the chl-a concentrations, suggesting that as in spring and summer sea ice, the sea-ice bacteria and algae may also be coupled during the Antarctic winter. Coupling between the bacterial community and sea-ice algae was further supported by significant correlations between bacterial abundance and production with chl-a. In addition, sulphate-reducing bacteria (for example, Desulforhopalus) together with odour of H 2 S were observed in thick, apparently anoxic ice, suggesting that the development of the anaerobic bacterial community may occur in sea ice under suitable conditions. In all, the results show that bacterial community in Antarctic sea ice can stay active throughout the winter period and thus possible future warming of sea ice and consequent increase in bacterial production may lead to changes in bacteria-mediated processes in the Antarctic sea-ice zone.

Leaf seal for gas turbine stator shrouds and a nozzle band

DOEpatents

Burdgick, Steven Sebastian; Sexton, Brendan Francis

2002-01-01

A leaf seal assembly is secured to the trailing edge of a shroud segment for sealing between the shroud segment and the leading edge side wall of a nozzle outer band. The leaf seal includes a circumferentially elongated seal plate biased by a pair of spring clips disposed in a groove along the trailing edge of the shroud segment to maintain the seal plate in engagement with the flange on the leading edge side wall of the nozzle outer band. The leaf seal plate and spring clips receive pins tack-welded to the shroud segment to secure the leaf seal assembly in place.

Summers with low Arctic sea ice linked to persistence of spring atmospheric circulation patterns

NASA Astrophysics Data System (ADS)

Kapsch, Marie-Luise; Skific, Natasa; Graversen, Rune G.; Tjernström, Michael; Francis, Jennifer A.

2018-05-01

The declining trend of Arctic September sea ice constitutes a significant change in the Arctic climate system. Large year-to-year variations are superimposed on this sea-ice trend, with the largest variability observed in the eastern Arctic Ocean. Knowledge of the processes important for this variability may lead to an improved understanding of seasonal and long-term changes. Previous studies suggest that transport of heat and moisture into the Arctic during spring enhances downward surface longwave radiation, thereby controlling the annual melt onset, setting the stage for the September ice minimum. In agreement with these studies, we find that years with a low September sea-ice concentration (SIC) are characterized by more persistent periods in spring with enhanced energy flux to the surface in forms of net longwave radiation plus turbulent fluxes, compared to years with a high SIC. Two main atmospheric circulation patterns related to these episodes are identified: one resembles the so-called Arctic dipole anomaly that promotes transport of heat and moisture from the North Pacific, whereas the other is characterized by negative geopotential height anomalies over the Arctic, favoring cyclonic flow from Siberia and the Kara Sea into the eastern Arctic Ocean. However, differences between years with low and high September SIC appear not to be due to different spring circulation patterns; instead it is the persistence and intensity of processes associated with these patterns that distinguish the two groups of anomalous years: Years with low September SIC feature episodes that are consistently stronger and more persistent than years with high SIC.

Recession of the Northern polar cap from the PFS Mars Express observations

NASA Astrophysics Data System (ADS)

Zasova, L. V.; Formisano, V.; Moroz, V. I.; Giuranna, M.; Grassi, D.; Hansen, G.; Ignatiev, N. I.; Maturilli, A.; Pfs Team

Planetary Fourier Spectrometer (PFS) has two spectral channels, devoted to the thermal and solar reflected spectral range investigations. The first observations by PFS of the Northern hemisphere ,which includes the North pole, occurred at Ls= 342 (northern winter). Surface temperature alone the orbit shows that the CO2 ice polar cap, where the surface temperature is found around 150K and below, is extended down to about 62 N. The spectra at latitudes above 80 N are obtained at polar darkness and at latitudes below 80 at illumination by the low Sun. Retrieved temperature profiles of the atmosphere at darkness show that temperature of the atmosphere is low enough to allow the CO2 condensation up to about 25 km. Between 70 and 80 latitude the upper levels of the atmosphere are heated by the Sun, but condensation of the CO2 may occur in the near surface layer below 5 km. The water ice clouds exist at lower latitudes with maximum opacity at the edge of the polar cap. More detailed investigation of the data obtained in winter as well as of the measurements in the northern spring will be presented.

The seasonal and inter-annual variability of sea-ice, ocean circulation and marine ecosystems in the Barents Sea: model results against satellite data

NASA Astrophysics Data System (ADS)

Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Pugalova, Svetlana

2015-04-01

This study is aimed at modelling the seasonal and inter-annual variability of sea-ice, ocean circulation and marine ecosystems in the Barents Sea in the modern period. Adequate description of marine ecosystems in the ice-covered seas crucially depends on the accuracy in determining of thicknesses of ice and snow on the sea surface which control penetrating photosynthetically active radiation under the ice. One of the few models of ice able to adequately reproduce the dynamics of sea ice is the sea ice model HELMI [1], containing 7 different categories of ice. This model has been imbedded into the Princeton Ocean Model. With this coupled model 2 runs for the period 1998-2007 were performed under different atmospheric forcing prescribed from NCEP/NCAR and ERA-40 archives. For prescribing conditions at the open boundary, all the necessary information about the horizontal velocity, level, temperature and salinity of the water, ice thickness and compactness was taken from the results of the global ocean general circulation model of the Max Planck Institute for Meteorology (Hamburg, Germany) MPIOM [2]. The resulting solution with NCEP forcing with a high accuracy simulates the seasonal and inter-annual variability of sea surface temperature (SST) estimated from MODIS data. The maximum difference between the calculated and satellite-derived SSTs (averaged over 4 selected areas of the Barents Sea) during the period 2000-2007 does not exceed 1.5 °C. Seasonal and inter-annual variations in the area of ice cover are also in good agreement with satellite-derived estimates. Pelagic ecosystem model developed in [3] has been coupled into the above hydrodynamic model and used to calculate the changes in the characteristics of marine ecosystems under NCEP forcing. Preliminarily the ecosystem model has been improved by introducing a parameterization of detritus deposition on the bottom and through the selection of optimal parameters for photosynthesis and zooplankton grazing, providing a solution having acceptable agreement with SeaWiFS estimates of surface chlorophyll "a" concentration. The solution for the period 1998-2007 correctly reproduces the start and end of vegetation period, and, with satisfactory accuracy, the level of the spring phytoplankton bloom, but systematically overestimates the SeaWiFS chlorophyll concentrations in the northern part of the sea and in the summer everywhere except for the southern part. According to the results, the region of phytoplankton blooming during the spring outbreak is bounded by the western boundary of the sea and the edge of solid ice. This work was supported by RFBR project № 13-05-00652 References 1. Haapala, J., Lönnroth, N., Stössel, A., 2005. A numerical study of open water formation in sea ice. J. Geophys. Res., V. 110(C9). P.1-17: doi: 10.1029/2003JC002200. 2. Gröger M., E. Maier-Reimer, U. Mikolajewicz, A. Moll, and D. Sein, 2013. NW European shelf under climate warming: implications for open ocean - shelf exchange, primary production, and carbon absorption. Biogeosciences, vol.10, 3767-3792, doi:10.5194/bg-10-3767-2013. 3. Anderson T.R., V. A. Ryabchenko; M. J. Fasham; V. A. Gorchakov. Denitrification in the Arabian Sea: A 3D ecosystem modeling study. Deep-Sea Research, Part I, V. 54, Issue 12, 2007, 2082-2119

Tracking sea ice floes from the Lincoln Sea to Nares Strait and deriving large scale melt from coincident spring and summer (2009) aerial EM thickness surveys

NASA Astrophysics Data System (ADS)

Lange, B. A.; Haas, C.; Beckers, J.; Hendricks, S.

2011-12-01

Satellite observations demonstrate a decreasing summer Arctic sea ice extent over the past ~40 years, as well as a smaller perennial sea ice zone, with a significantly accelerated decline in the last decade. Recent ice extent observations are significantly lower than predicted by any model employed by the Intergovernmental Panel on Climate Change. The disagreement of the modeled and observed results, along with the large variability of model results, can be in part attributed to a lack of consistent and long term sea ice mass balance observations for the High Arctic. This study presents the derivation of large scale (individual floe) seasonal sea ice mass balance in the Lincoln Sea and Nares Strait. Large scale melt estimates are derived by comparing aerial borne electromagnetic induction thickness surveys conducted in spring with surveys conducted in summer 2009. The comparison of coincident floes is ensured by tracking sea ice using ENIVSAT ASAR and MODIS satellite imagery. Only EM thickness survey sections of floes that were surveyed in both spring and summer are analyzed and the resulting modal thicknesses of the distributions, which represent the most abundant ice type, are compared to determine the difference in thickness and therefore total melt (snow+basal ice+surface ice melt). Preliminary analyses demonstrate a bulk (regional ice tracking) seasonal total thickness variability of 1.1m, Lincoln Sea modal thickness 3.7m (April, 2009) and Nares Strait modal thickness 2.6m (August 2009)(Fig1). More detailed floe tracking, in depth analysis of EM surveys and removal of deformed ridged/rafted sea ice (due to inaccuracies over deformed ice) will result in more accurate melt estimates for this region and will be presented. The physical structure of deformed sea ice and the footprint of the EM instrument typically underestimate the total thicknesses observed. Seasonal variations of sea ice properties can add additional uncertainty to the response of the EM instrument over deformed ridged/rafted sea ice. Here we will present additional analysis of the data comparing total thickness to ridge height that will provide some insight into the magnitude of seasonal discrepancies experienced by the EM instrument over deformed ice.

Pack ice along the Kamchatka Peninsula, Russia as seen from STS-60

NASA Technical Reports Server (NTRS)

1994-01-01

Pack ice is documented in this photograph along the coast of the Kamchatka Peninsula of Russia in Zaliv Ozernoj. Detailed photographs of the ice provide information to scientists in both Russia and the United States about the location and fluctuation of ice edges, and how this new sea ice interacts with ocean and littoral currents.

HiRISE observations of gas sublimation-driven activity in Mars' southern polar regions: III. Models of processes involving translucent ice

USGS Publications Warehouse

Portyankina, G.; Markiewicz, W.J.; Thomas, N.; Hansen, C.J.; Milazzo, M.

2010-01-01

Enigmatic surface features, known as 'spiders', found at high southern martian latitudes, are probably caused by sublimation-driven erosion under the seasonal carbon dioxide ice cap. The Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) has imaged this terrain in unprecedented details throughout southern spring. It has been postulated [Kieffer, H.H., Titus, T.N., Mullins, K.F., Christensen, P.R., 2000. J. Geophys. Res. 105, 9653-9700] that translucent CO2 slab ice traps gas sublimating at the ice surface boundary. Wherever the pressure is released the escaping gas jet entrains loose surface material and carries it to the top of the ice where it is carried downslope and/or downwind and deposited in a fan shape. Here we model two stages of this scenario: first, the cleaning of CO2 slab ice from dust, and then, the breaking of the slab ice plate under the pressure built below it by subliming ice. Our modeling results and analysis of HiRISE images support the gas jet hypothesis and show that outbursts happen very early in spring. ?? 2009 Elsevier Inc. All rights reserved.

Observational Evidence for Enhanced Greenhouse Effect Reinforcing Wintertime Arctic Amplification and Sea Ice Melting Onset

NASA Astrophysics Data System (ADS)

Cao, Y.; Liang, S.

2017-12-01

Despite an apparent hiatus in global warming, the Arctic climate continues to experience unprecedented changes. Summer sea ice is retreating at an accelerated rate, and surface temperatures in this region are rising at a rate double that of the global average, a phenomenon known as Arctic amplification. Although a lot of efforts have been made, the causes this unprecedented phenomenon remain unclear and are subjects of considerable debate. In this study, we report strong observational evidence, for the first time from long-term (1984-2014) spatially complete satellite records, that increased cloudiness and atmospheric water vapor in winter and spring have caused an extraordinary downward longwave radiative flux to the ice surface, which may then amplify the Arctic wintertime ice-surface warming. In addition, we also provide observed evidence that it is quite likely the enhancement of the wintertime greenhouse effect caused by water vapor and cloudiness has advanced the time of onset of ice melting in mid-May through inhibiting sea-ice refreezing in the winter and accelerating the pre-melting process in the spring, and in turn triggered the positive sea-ice albedo feedback process and accelerated the sea ice melting in the summer.

Interaction of part-through cracks in a flat plate

NASA Technical Reports Server (NTRS)

Aksel, B.; Erdogan, F.

1985-01-01

The accuracy of the line spring model is determined. The effect of interaction between two and three cracks is investigated, and extensive numerical results which may be useful in applications are provided. Line spring model with Reissner's plate theory is formulated to be used for any number and configurations of cracks provided that there is symmetry. This model is used to find stress intensity factors for elliptic internal cracks, elliptic edge cracks and two opposite elliptic edge cracks. Despite the simplicity of the line spring model, the results are found to be close.

Dissolved iron and iron(II) distributions beneath the pack ice in the East Antarctic (120°E) during the winter/spring transition

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; van der Merwe, Pier; Chever, Fanny; Cullen, Jay T.; Lannuzel, Delphine; Bowie, Andrew R.

2016-09-01

Distributions of dissolved iron (dFe) and its reduced form, Fe(II), to a depth of 1000 m were investigated under the seasonal pack ice off East Antarctica during the Sea Ice Physics and Ecosystem experiment (SIPEX-2) sea-ice voyage in September-October 2012. Concentrations of dFe were elevated up to five-fold relative to Southern Ocean background concentrations and were spatially variable. The mean dFe concentration was 0.44±0.4 nM, with a range from 0.09 to 3.05 nM. Profiles of dFe were more variable within and among stations than were macronutrients, suggesting that coupling between these biologically-essential elements was weak at the time of the study. Brine rejection and drainage from sea ice are estimated to be the dominant contributors to elevated dFe concentrations in the mixed layer, but mass budget considerations indicate that estimated dFe fluxes from brine input alone are insufficient to account for all observed dFe. Melting icebergs and shelf sediments are suspected to provide the additional dFe. Fe(II) was mostly below the detection limit but elevated at depth near the continental shelf, implying that benthic processes are a source of reduced Fe in bottom waters. The data indicate that dFe builds up under the seasonal sea-ice cover during winter and that reduction of Fe may be hampered in early spring by several factors such as lack of electron donors, low biological productivity and inadequate light below the sea ice. The accumulated dFe pool in the mixed layer is expected to contribute to the formation of the spring bloom as the ice retreats.

Return of warm conditions in the southeastern Bering Sea: Physics to fluorescence

PubMed Central

Duffy-Anderson, J. T.; Eisner, L. B.; Farley, E. V.; Heintz, R. A.; Mordy, C. W.

2017-01-01

From 2007 to 2013, the southeastern Bering Sea was dominated by extensive sea ice and below-average ocean temperatures. In 2014 there was a shift to reduced sea ice on the southern shelf and above-average ocean temperatures. These conditions continued in 2015 and 2016. During these three years, the spring bloom at mooring site M4 (57.9°N, 168.9°W) occurred primarily in May, which is typical of years without sea ice. At mooring site M2 (56.9°N, 164.1°W) the spring bloom occurred earlier especially in 2016. Higher chlorophyll fluorescence was observed at M4 than at M2. In addition, these three warm years continued the pattern near St. Matthew Island of high concentrations (>1 μM) of nitrite occurring during summer in warm years. Historically, the dominant parameters controlling sea-ice extent are winds and air temperature, with the persistence of frigid, northerly winds in winter and spring resulting in extensive ice. After mid-March 2014 and 2016 there were no cold northerly or northeasterly winds. Cold northerly winds persisted into mid-April in 2015, but did not result in extensive sea ice south of 58°N. The apparent mechanism that helped limit ice on the southeastern shelf was the strong advection of warm water from the Gulf of Alaska through Unimak Pass. This pattern has been uncommon, occurring in only one other year (2003) in a 37-year record of estimated transport through Unimak Pass. During years with no sea ice on the southern shelf (e.g. 2001–2005, 2014–2016), the depth-averaged temperature there was correlated to the previous summers ocean temperature. PMID:28957386

Atmospheric components of the surface energy budget over young sea ice: Results from the N-ICE2015 campaign

NASA Astrophysics Data System (ADS)

Walden, Von P.; Hudson, Stephen R.; Cohen, Lana; Murphy, Sarah Y.; Granskog, Mats A.

2017-08-01

The Norwegian young sea ice campaign obtained the first measurements of the surface energy budget over young, thin Arctic sea ice through the seasonal transition from winter to summer. This campaign was the first of its kind in the North Atlantic sector of the Arctic. This study describes the atmospheric and surface conditions and the radiative and turbulent heat fluxes over young, thin sea ice. The shortwave albedo of the snow surface ranged from about 0.85 in winter to 0.72-0.80 in early summer. The near-surface atmosphere was typically stable in winter, unstable in spring, and near neutral in summer once the surface skin temperature reached 0°C. The daily average radiative and turbulent heat fluxes typically sum to negative values (-40 to 0 W m-2) in winter but then transition toward positive values of up to nearly +60 W m-2 as solar radiation contributes significantly to the surface energy budget. The sensible heat flux typically ranges from +20-30 W m-2 in winter (into the surface) to negative values between 0 and -20 W m-2 in spring and summer. A winter case study highlights the significant effect of synoptic storms and demonstrates the complex interplay of wind, clouds, and heat and moisture advection on the surface energy components over sea ice in winter. A spring case study contrasts a rare period of 24 h of clear-sky conditions with typical overcast conditions and highlights the impact of clouds on the surface radiation and energy budgets over young, thin sea ice.

Breakup of Pack Ice, Antarctic Ice Shelf

NASA Technical Reports Server (NTRS)

1991-01-01

Breakup of Pack Ice along the periphery of the Antarctic Ice Shelf (53.5S, 3.0E) produced this mosaic of ice floes off the Antarctic Ice Shelf. Strong offshore winds, probably associated with strong katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filamets of sea ice, icebergs, bergy bits and growlers to flow northward into the South Atlantic Ocean. 53.5S, 3.0E

Observations of sea ice and icebergs in the western Barents Sea during the winter of 1987

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

Loeset, S.; Carstens, T.

1995-12-31

A multisensor ice data acquisition program for the western Barents Sea was carried out during three field campaigns in the mid winter and fall of 1987. The main purpose of the program was to obtain comprehensive information about the ice in the area at that time. The reasoning was that prior to any oil/gas exploration and production in the Barents Sea, the physical environment has to be quantitatively surveyed in order to ensure safe operations related to human safety, the regular operability and safety of the structure and protection of the environment. Prior to this field investigation program in 1987more » data on sea ice and icebergs for engineering purposes for the western Barents Sea were meager. The present paper highlights some of the findings with emphasis on ice edge speeds, ice edge displacement and ice drift. For icebergs, the paper focuses on population, size distributions and geometric parameters.« less

Adsorption and structure of water on kaolinite surfaces: possible insight into ice nucleation from grand canonical monte carlo calculations.

PubMed

Croteau, T; Bertram, A K; Patey, G N

2008-10-30

Grand canonical Monte Carlo calculations are used to determine water adsorption and structure on defect-free kaolinite surfaces as a function of relative humidity at 235 K. This information is then used to gain insight into ice nucleation on kaolinite surfaces. Results for both the SPC/E and TIP5P-E water models are compared and demonstrate that the Al-surface [(001) plane] and both protonated and unprotonated edges [(100) plane] strongly adsorb at atmospherically relevant relative humidities. Adsorption on the Al-surface exhibits properties of a first-order process with evidence of collective behavior, whereas adsorption on the edges is essentially continuous and appears dominated by strong water lattice interactions. For the protonated and unprotonated edges no structure that matches hexagonal ice is observed. For the Al-surface some of the water molecules formed hexagonal rings. However, the a o lattice parameter for these rings is significantly different from the corresponding constant for hexagonal ice ( Ih). A misfit strain of 14.0% is calculated between the hexagonal pattern of water adsorbed on the Al-surface and the basal plane of ice Ih. Hence, the ring structures that form on the Al-surface are not expected to be good building-blocks for ice nucleation due to the large misfit strain.

Sea-ice habitat preference of the Pacific walrus (Odobenus rosmarus divergens) in the Bering Sea: A multiscaled approach

NASA Astrophysics Data System (ADS)

Sacco, Alexander Edward

The goal of this thesis is to define specific parameters of mesoscale sea-ice seascapes for which walruses show preference during important periods of their natural history. This research thesis incorporates sea-ice geophysics, marine-mammal ecology, remote sensing, computer vision techniques, and traditional ecological knowledge of indigenous subsistence hunters in order to quantitatively study walrus preference of sea ice during the spring migration in the Bering Sea. Using an approach that applies seascape ecology, or landscape ecology to the marine environment, our goal is to define specific parameters of ice patch descriptors, or mesoscale seascapes in order to evaluate and describe potential walrus preference for such ice and the ecological services it provides during an important period of their life-cycle. The importance of specific sea-ice properties to walrus occupation motivates an investigation into how walruses use sea ice at multiple spatial scales when previous research suggests that walruses do not show preference for particular floes. Analysis of aerial imagery, using image processing techniques and digital geomorphometric measurements (floe size, shape, and arrangement), demonstrated that while a particular floe may not be preferred, at larger scales a collection of floes, specifically an ice patch (< 4 km2), was preferred. This shows that walruses occupy ice patches with distinct ice features such as floe convexity, spatial density, and young ice and open water concentration. Ice patches that are occupied by adult and juvenile walruses show a small number of characteristics that vary from those ice patches that were visually unoccupied. Using synthetic aperture radar imagery, we analyzed co-located walrus observations and statistical texture analysis of radar imagery to quantify seascape preferences of walruses during the spring migration. At a coarse resolution of 100 -- 9,000 km2, seascape analysis shows that, for the years 2006 -- 2008, walruses were preferentially occupying fragmented pack ice seascapes range 50 -- 89% of the time, when, all throughout the Bering Sea, only range 41 -- 46% of seascapes consisted of fragmented pack ice. Traditional knowledge of a walrus' use of sea ice is investigated through semi-directed interviews conducted with subsistence hunters and elders from Savoonga and Gambell, two Alaskan Native communities on St. Lawrence Island, Alaska. Informants were provided with a large nautical map of the land and ocean surrounding St. Lawrence Island and 45 printed large-format aerial photographs of walruses on sea ice to stimulate discussion as questions were asked to direct the topics of conversation. Informants discussed change in sea ice conditions over time, walrus behaviors during the fall and spring subsistence hunts, and sea-ice characteristics that walruses typically occupy. These observations are compared with ice-patch preferences analyzed from aerial imagery. Floe size was found to agree with remotely-sensed ice-patch analysis results, while floe shape was not distinguishable to informants during the hunt. Ice-patch arrangement descriptors concentration and density generally agreed with ice-patch analysis results. Results include possible preference of ice-patch descriptors at the ice-patch scale and fragmented pack ice preference at the seascape scale. Traditional knowledge suggests large ice ridges are preferential sea-ice features at the ice-patch scale, which are rapidly becoming less common during the fall and spring migration of sea ice through the Bering Sea. Traditional knowledge, combined with a scientific analysis and field work to study species habitat preferences and, ultimately, habitat partitioning, can stem from these results. Future work includes increased sophistication of the synthetic aperture radar classification algorithm, experimentation with various spatial scales to determine the optimal scale for walrus' life-cycle events, and incorporation of further traditional knowledge to investigate and interface cross-cultural sea-ice observations, knowledge and science to determine sea ice importance to marine mammals in a changing Arctic.

Wave Measurements in Landfast Ice in Svalbard: Evolution of Wave Propagation following Wind Waves to Swell Transition

NASA Astrophysics Data System (ADS)

Sutherland, G.; Rabault, J.; Jensen, A.; Christensen, K. H.; Ward, B.; Marchenko, A. V.; Morozov, E.; Gundersen, O.; Halsne, T.; Lindstrøm, E.

2016-02-01

The impact of sea-ice cover on propagation of water waves has been studied over five decades, both theoretically and from measurements on the ice. Understanding the interaction between water waves and sea-ice covers is a topic of interest for a variety of purposes such as formulation of ocean models for climate, weather and sea state predictions, and the analysis of pollution dispersion in the Arctic. Our knowledge of the underlying phenomena is still partial, and more experimental data is required to gain further insight into the associated physics. Three Inertial Motion Units (IMUs) have been assessed in the lab and used to perform measurements on landfast ice over 2 days in Tempelfjorden, Svalbard during March 2015. The ice thickness in the measurement area was approximately 60 to 80 cm. Two IMUs were located close to each other (6 meters) at a distance around 180 m from the ice edge. The third IMU was placed 120 m from the ice edge. The data collected contains a transition from high frequency, wind generated waves to lower frequency swell. Drastic changes in wave propagation are observed in relation with this transition. The level of reflected energy obtained from rotational spectra is much higher before the transition to low frequency swell than later on. The correlation between the signal recorded by the IMU closer to the ice edge and the two others IMUs is low during the wind waves dominated period, and increases with incoming swell. The dispersion relation for waves in ice was found to correspond to flexural-gravity waves before the transition and deepwater gravity waves afterwards.

Earth Observations taken by the Expedition 21 Crew

NASA Image and Video Library

2009-10-25

ISS021-E-015243 (25 Oct. 2009) --- Upsala Glacier, Argentina is featured in this image photographed by an Expedition 21 crew member on the International Space Station. The Southern Patagonian Ice Field of Argentina and Chile hosts some of the most spectacular glaciers in the world, and is second only to Antarctica in size. This detailed photograph illustrates the terminus of Upsala Glacier, located on the eastern side of the ice field. This glacier is the third largest in the Southern Patagonian Ice Field and, like most other glaciers in the region, has experienced significant retreat over the past century. This image was taken during spring in the Southern Hemisphere, and calving of icebergs ? release of chunks of ice from the glacier terminus as it enters the waters of Lake Argentina - is visible at left. Two icebergs are of particular interest, as they retain fragments of the moraine that forms a dark line along the upper surface of the glacier. Moraines of the type visible in this image are formed from coarse rock and soil debris that accumulates along the front and sides of a flowing glacier; much like a bulldozer blade pushes material in front of it. When two glaciers merge together (center), debris in moraines along their edges can now form a medial moraine that is drawn out along the upper surface of the new ice mass. These moraines can be carried intact to the terminus and included in icebergs that then float away, dropping the coarse debris as the iceberg melts. While the icebergs produced by Upsala Glacier do not reach an ocean, there are many current glaciers ? as well as glaciers and ice sheets that existed in the geologic past ? capable of producing ocean-going icebergs. This process is thought to be recorded in the geologic record as layers or lenses of coarse, land-derived sediments within finer grained sea floor sediments that are located far from any current (or former) coastline.

Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

USGS Publications Warehouse

Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

2013-01-01

Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

Observations of geese foraging for clam shells during spring on the Yukon-Kuskokwim Delta, Alaska

USGS Publications Warehouse

Flint, Paul L.; Fowler, Ada C.; Bottitta, Grace E.; Schamber, Jason L.

1998-01-01

We studied the behavior of geese on exposed river ice during spring on the Yukon-Kuskokwim Delta. The predominant behavior while on the ice for both sexes was foraging; however, females foraged more than males. Visual inspection of the ice revealed no potential plant or animal food items. However, numerous small (<20 mm) clam shells (Macoma balthica) and pieces of shell were noted. It appeared that geese were foraging on empty clam shells. This potential source of calcium was available to breeding geese just prior to egg formation and geese likely stored this calcium in the form of medullary bone for use during egg formation.

Ross Ice Shelf, Antarctic Ice and Clouds

NASA Technical Reports Server (NTRS)

1991-01-01

In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.

Springtime atmospheric transport controls Arctic summer sea-ice extent

NASA Astrophysics Data System (ADS)

Kapsch, Marie; Graversen, Rune; Tjernström, Michael

2013-04-01

The sea-ice extent in the Arctic has been steadily decreasing during the satellite remote sensing era, 1979 to present, with the highest rate of retreat found in September. Contributing factors causing the ice retreat are among others: changes in surface air temperature (SAT; Lindsay and Zhang, 2005), ice circulation in response to winds/pressure patterns (Overland et al., 2008) and ocean currents (Comiso et al., 2008), as well as changes in radiative fluxes (e.g. due to changes in cloud cover; Francis and Hunter, 2006; Maksimovich and Vihma, 2012) and ocean conditions. However, large interannual variability is superimposed onto the declining trend - the ice extent by the end of the summer varies by several million square kilometer between successive years (Serreze et al., 2007). But what are the processes causing the year-to-year ice variability? A comparison of years with an anomalously large September sea-ice extent (HIYs - high ice years) with years showing an anomalously small ice extent (LIYs - low ice years) reveals that the ice variability is most pronounced in the Arctic Ocean north of Siberia (which became almost entirely ice free in September of 2007 and 2012). Significant ice-concentration anomalies of up to 30% are observed for LIYs and HIYs in this area. Focusing on this area we find that the greenhouse effect associated with clouds and water-vapor in spring is crucial for the development of the sea ice during the subsequent months. In years where the end-of-summer sea-ice extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the ice retreat is encountered. The anomalous convergence of humidity increases the cloudiness, resulting in an enhancement of the greenhouse effect. As a result, downward longwave radiation at the surface is larger than usual. In mid May, when the ice anomaly begins to appear and the surface albedo therefore becomes anomalously low, the net shortwave radiation anomaly becomes positive. The net shortwave radiation contributes during the rest of the melting season to an enhanced energy flux towards the surface. These findings lead to the conclusion that enhanced longwave radiation associated with positive humidity and cloud anomalies during spring plays a significant role in initiating the summer ice melt, whereas shortwave-radiation anomalies act as an amplifying feedback once the melt has started. References: Lindsay, R. and J. Zhang. The thinning of Arctic Sea Ice, 19882003: Have We Passed a Tipping Point?. J. Clim. 18, 48794894 (2005). Overland, J. E., M. Wang and S. Salo. The recent Arctic warm period. Tellus 60A, 589-597 (2008). Comiso, J. C., C. L. Parkinson, R. Gersten and L. Stock. Accelerated Decline in the Arctic sea ice cover. Geophys. Res. Lett. 35, L01703 (2008). Francis, J. A. and E. Hunter. New Insight Into the Disappearing Arctic Sea Ice. EOS T. Am. Geophys. Un. 87, 509511 (2006). Maksimovich, E. and T. Vihma. The effect of heat fluxes on interannual variability in the spring onset of snow melt in the central Arctic Ocean. J. Geophys. Res. 117, C07012 (2012). Serreze, M. C., M. M. Holland and J. Stroeve. Perspectives on the Arctic's Shrinking Sea-Ice Cover. Science 315, 1533-1536 (2007).

Ice, Ocean and Atmosphere Interactions in the Arctic Marginal Ice Zone

DTIC Science & Technology

2015-09-30

the northward retreat of the ice edge. Through the long-term measurement of the key oceanic, atmospheric, and sea ice processes that...began to move southward towards the Alaskan coast. In 2104 the anomalous areas of ice retreat were the region north of Alaska...and Siberia. (see figures below). This is not uncommon as these regions have seen the greatest retreat in sea ice. See http://nsidc.org

Understanding Nearshore Processes Of a Large Arctic Delta Using Combined Seabed Mapping, In Situ Observations, Remote Sensing and Modeling

NASA Astrophysics Data System (ADS)

Solomon, S. M.; Couture, N. J.; Forbes, D. L.; Hoque, A.; Jenner, K. A.; Lintern, G.; Mulligan, R. P.; Perrie, W. A.; Stevens, C. W.; Toulany, B.; Whalen, D.

2009-12-01

The Mackenzie River Delta and the adjacent continental shelf in the southeastern Beaufort Sea are known to host significant quantities of hydrocarbons. Recent environmental reviews of proposed hydrocarbon development have highlighted the need for a better understanding of the processes that control sediment transport and coastal stability. Over the past several years field surveys have been undertaken in winter, spring and summer to acquire data on seabed morphology, sediment properties, sea ice, river-ocean interaction and nearshore oceanography. These data are being used to improve conceptual models of nearshore processes and to develop and validate numerical models of waves, circulation and sediment transport. The timing and location of sediment erosion, transport and deposition is complex, driven by a combination of open water season storms and spring floods. Unlike temperate counterparts, the interaction between the Mackenzie River and the Beaufort Sea during spring freshet is mediated by the presence of ice cover. Increasing discharge exceeds the under-ice flow capacity leading to flooding of the ice surface, followed by vortex drainage through the ice and scour of the seabed below (“strudel” drainage and scour). During winter months, nearshore circulation slows beneath a thickening ice canopy. Recent surveys have shown that the low gradient inner shelf is composed of extensive shoals where ice freezes to the seabed and intervening zones which are slightly deeper than the ice is thick. The duration of ice contact with the bed determines the thermal characteristics of the seabed. Analysis of cores shows that the silts comprising the shoals are up to 6 m thick. The predominantly well sorted and cross-laminated nature of the silts at the top of the cores suggests an active delta front environment. Measurements of waves, currents, conductivity, temperature and sediment concentration during spring and late summer have been acquired. During moderate August storm events, waves attenuate rapidly inshore of the 3 m isobath. Entrainment of fine material and rapid flocculation due to the presence of brackish water may induce the transient formation of high density suspensions near the seabed which contributes to this rapid attenuation. The relatively poor performance of shallow water wave models (e.g. SWAN) in very shallow depths during storm simulations appears to be related to inaccurate formulations for wave attenuation in this environment.

CFD Analysis of the Aerodynamics of a Business-Jet Airfoil with Leading-Edge Ice Accretion

NASA Technical Reports Server (NTRS)

Chi, X.; Zhu, B.; Shih, T. I.-P.; Addy, H. E.; Choo, Y. K.

2004-01-01

For rime ice - where the ice buildup has only rough and jagged surfaces but no protruding horns - this study shows two dimensional CFD analysis based on the one-equation Spalart-Almaras (S-A) turbulence model to predict accurately the lift, drag, and pressure coefficients up to near the stall angle. For glaze ice - where the ice buildup has two or more protruding horns near the airfoil's leading edge - CFD predictions were much less satisfactory because of the large separated region produced by the horns even at zero angle of attack. This CFD study, based on the WIND and the Fluent codes, assesses the following turbulence models by comparing predictions with available experimental data: S-A, standard k-epsilon, shear-stress transport, v(exp 2)-f, and differential Reynolds stress.

Shuttle Imaging Radar B (SIR-B) Weddell Sea ice observations - A comparison of SIR-B and scanning multichannel microwave radiometer ice concentrations

NASA Technical Reports Server (NTRS)

Martin, Seelye; Holt, Benjamin; Cavalieri, Donald J.; Squire, Vernon

1987-01-01

Ice concentrations over the Weddell Sea were studied using SIR-B data obtained during the October 1984 mission, with special attention given to the effect of ocean waves on the radar return at the ice edge. Sea ice concentrations were derived from the SIR-B data using two image processing methods: the classification scheme at JPL and the manual classification method at Scott Polar Research Institute (SPRI), England. The SIR ice concentrations were compared with coincident concentrations from the Nimbus-7 SMMR. For concentrations greater than 40 percent, which was the smallest concentration observed jointly by SIR-B and the SMMR, the mean difference between the two data sets for 12 points was 2 percent. A comparison between the JPL and the SPRI SIR-B algorithms showed that the algorithms agree to within 1 percent in the interior ice pack, but the JPL algorithm gives slightly greater concentrations at the ice edge (due to the fact that the algorithm is affected by the wind waves in these areas).

Characteristics of surface roughness associated with leading edge ice accretion

NASA Technical Reports Server (NTRS)

Shin, Jaiwon

1994-01-01

Detailed size measurements of surface roughness associated with leading edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data was obtained from icing tests conducted in the Icing Research Tunnel (IRT) at NASA Lewis Research Center (LeRC) using a NACA 0012 airfoil. Measurements include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The height of roughness grows as the air temperature and the liquid water content increase, however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very initial stage of the ice accretion process.

Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

USGS Publications Warehouse

Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T.J.

2016-01-01

High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in ice-off timing. In the most well-studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

Acoustic effects of oil-production activities on bowhead and white whales visible during spring migration near Pt. Barrow, Alaska-1990 phase: sound propagation and whale responses to playbacks of continuous drilling noise from an ice platform, as studied in pack ice conditions. Final report

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

Richardson, W.J.; Greene, C.R.; Koski, W.R.

1991-10-01

The report concerns the effects of underwater noise from simulated oil production operations on the movements and behavior of bowhead and white whales migrating around northern Alaska in spring. An underwater sound projector suspended from pack ice was used to introduce recorded drilling noise and other test sounds into leads through the pack ice. These sounds were received and measured at various distances to determine the rate of sound attenuation with distance and frequency. The movements and behavior of bowhead and white whales approaching the operating projector were studied by aircraft- and ice-based observers. Some individuals of both species weremore » observed to approach well within the ensonified area. However, behavioral changes and avoidance reactions were evident when the received sound level became sufficiently high. Reactions to aircraft are also discussed.« less

Late Spring Nitrate Distributions Beneath the Ice-Covered Northeastern Chukchi Shelf

NASA Astrophysics Data System (ADS)

Arrigo, Kevin R.; Mills, Matthew M.; van Dijken, Gert L.; Lowry, Kate E.; Pickart, Robert S.; Schlitzer, Reiner

2017-09-01

Measurements of late springtime nutrient concentrations in Arctic waters are relatively rare due to the extensive sea ice cover that makes sampling difficult. During the SUBICE (Study of Under-ice Blooms In the Chukchi Ecosystem) cruise in May-June 2014, an extensive survey of hydrography and prebloom concentrations of inorganic macronutrients, oxygen, particulate organic carbon and nitrogen, and chlorophyll a was conducted in the northeastern Chukchi Sea. Cold (<-1.5°C) winter water was prevalent throughout the study area, and the water column was weakly stratified. Nitrate (NO3-) concentration averaged 12.6 ± 1.92 μM in surface waters and 14.0 ± 1.91 μM near the bottom and was significantly correlated with salinity. The highest NO3- concentrations were associated with winter water within the Central Channel flow path. NO3- concentrations were much reduced near the northern shelf break within the upper halocline waters of the Canada Basin and along the eastern side of the shelf near the Alaskan coast. Net community production (NCP), estimated as the difference in depth-integrated NO3- content between spring (this study) and summer (historical), varied from 28 to 38 g C m-2 a-1. This is much lower than previous NCP estimates that used NO3- concentrations from the southeastern Bering Sea as a baseline. These results demonstrate the importance of using profiles of NO3- measured as close to the beginning of the spring bloom as possible when estimating local NCP. They also show that once the snow melts in spring, increased light transmission through the sea ice to the waters below the ice could fuel large phytoplankton blooms over a much wider area than previously known.

Whole-stream metabolism of a perennial spring-fed aufeis field in Alaska, with coincident surface and subsurface flow

NASA Astrophysics Data System (ADS)

Hendrickson, P. J.; Gooseff, M. N.; Huryn, A. D.

2017-12-01

Aufeis (icings or naleds) are seasonal arctic and sub-arctic features that accumulate through repeated overflow and freeze events of river or spring discharge. Aufeis fields, defined as the substrate on which aufeis form and the overlaying ice, have been studied to mitigate impacts on engineering structures; however, ecological characteristics and functions of aufeis fields are poorly understood. The perennial springs that supply warm water to aufeis fields create unique fluvial habitats, and are thought to act as winter and summer oases for biota. To investigate ecosystem function, we measured whole-stream metabolism at the Kuparuk River Aufeis (North Slope, AK), a large ( 5 km2) field composed of cobble substrate and predominately subsurface flow dynamics. The single-station open channel diel oxygen method was utilized at several dissolved oxygen (DO) stations located within and downstream of the aufeis field. DO loggers were installed in August 2016, and data downloaded summer 2017. Daily ecosystem respiration (ER), gross primary production (GPP) and reaeration rates were modeled using BASE, a package freely available in the open-source software R. Preliminary results support net heterotrophy during a two-week period of DO measurements in the fall season when minimum ice extent is observed. GPP, ER, and net metabolism are greater at the upstream reach near the spring source (P/R = 0.53), and decrease as flow moves downstream. As flow exits the aufeis field, surface and subsurface flow are incorporated into the metabolism model, and indicate the stream system becomes dependent on autochthonous production (P/R = 0.91). Current work is directed towards spring and summer discharge and metabolic parameter estimation, which is associated with maximum ice extent and rapid melting of the aufeis feature.

Carbon budget of sea-ice algae in spring: Evidence of a significant transfer to zooplankton grazers

NASA Astrophysics Data System (ADS)

Michel, C.; Legendre, L.; Ingram, R. G.; Gosselin, M.; Levasseur, M.

1996-08-01

The fate of ice-bottom algae, before and after release from the first-year sea ice into the water column, was assessed during the period of ice-algal growth and decline in Resolute Passage (Canadian Arctic). During spring 1992 (from April to June), algae in the bottom ice layer and those suspended and sinking in the upper water column (top 15 m) were sampled approximately every 4 days. Ice-bottom chlorophyll a reached a maximum concentration of 160 mg m-2 in mid-May, after which it decreased to lower values. In the water column, chlorophyll a concentrations were low until the period of ice-algal decline (˜0.1 mg m-3), with most biomass in the <5-μm fraction. In both the suspended and sinking material, large increases of algal biomass occurred at the beginning of June, following the release of ice-algae into the water column. The input of ice-algal derived carbon to the upper water column and the proportions exported through sinking or remaining in suspension were assessed using a carbon budget for the two periods of ice-algal growth and decline. For each period the output terms closely balanced the input. The carbon budget showed that most of the biomass introduced into the upper water column remained suspended (>65% of total export) and that ice-algae were ingested by under-ice grazers after release from the ice. These results stress the importance of ice algae for pelagic consumers during the early stages of ice melt and show that the transfer of ice algae to higher trophic levels extends beyond the period of maximum algal production in the ice bottom.

49 CFR 213.139 - Spring rail frogs.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false Spring rail frogs. 213.139 Section 213.139..., DEPARTMENT OF TRANSPORTATION TRACK SAFETY STANDARDS Track Structure § 213.139 Spring rail frogs. (a) The outer edge of a wheel tread shall not contact the gage side of a spring wing rail. (b) The toe of each...

49 CFR 213.139 - Spring rail frogs.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Spring rail frogs. 213.139 Section 213.139..., DEPARTMENT OF TRANSPORTATION TRACK SAFETY STANDARDS Track Structure § 213.139 Spring rail frogs. (a) The outer edge of a wheel tread shall not contact the gage side of a spring wing rail. (b) The toe of each...

49 CFR 213.139 - Spring rail frogs.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 4 2013-10-01 2013-10-01 false Spring rail frogs. 213.139 Section 213.139..., DEPARTMENT OF TRANSPORTATION TRACK SAFETY STANDARDS Track Structure § 213.139 Spring rail frogs. (a) The outer edge of a wheel tread shall not contact the gage side of a spring wing rail. (b) The toe of each...

49 CFR 213.139 - Spring rail frogs.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Spring rail frogs. 213.139 Section 213.139..., DEPARTMENT OF TRANSPORTATION TRACK SAFETY STANDARDS Track Structure § 213.139 Spring rail frogs. (a) The outer edge of a wheel tread shall not contact the gage side of a spring wing rail. (b) The toe of each...

49 CFR 213.139 - Spring rail frogs.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Spring rail frogs. 213.139 Section 213.139..., DEPARTMENT OF TRANSPORTATION TRACK SAFETY STANDARDS Track Structure § 213.139 Spring rail frogs. (a) The outer edge of a wheel tread shall not contact the gage side of a spring wing rail. (b) The toe of each...

Thermomechanical Ablation

DTIC Science & Technology

1975-09-01

Ice, and Camphor (Summarized from Ref 11) . . . . . . . 16 3 Boundary Layer Edge Velocity Normalized by Free Stream Velocity for a Sphere and a...function of environmental conditions for water ice, dry ice, and camphor which are summarized in Figure 2. A low turbulence subsonic free jet was chosen

Distributed ice accretion sensor for smart aircraft structures

NASA Technical Reports Server (NTRS)

Gerardi, J. J.; Hickman, G. A.

1989-01-01

A distributed ice accretion sensor is presented, based on the concept of smart structures. Ice accretion is determined using spectral techniques to process signals from piezoelectric sensors integral to the airfoil skin. Frequency shifts in the leading edge structural skin modes are correlated to ice thickness. It is suggested that this method may be used to detect ice over large areas with minimal hardware. Results are presented from preliminary tests to measure simulated ice growth.

Acquisition of Ice Thickness and Ice Surface Characteristics in the Seasonal Ice Zone by CULPIS-X during the US Coast Guard’s Arctic Domain Awareness Program

DTIC Science & Technology

2014-09-30

OBJECTIVES • What is the volume of sea ice in the Beaufort Sea Seasonal Ice Zone (SIZ) and how does this evolve during summer as the ice edge...retreats? Recent observations suggest that the remaining ice in the Beaufort Sea is younger and thinner in recent years in part because even the oldest...surrounding ice . Recent analyses have indicated that ponds on thinner ice are often darker, accelerating the ice - albedo feedback over thin ice in summer

Icy Wonderland

NASA Image and Video Library

2015-02-04

Although the season is late spring, carbon dioxide ice still covers much of the surface at this high latitude site. It is still a chilly -128 degrees Celsius. The weak boundaries of the polygonal structure of the surface have been eroded by spring sublimation of carbon dioxide as energy from the Sun turns ice to gas. The larger troughs in this image accentuate the surface polygonal structure, while the narrow cracks show the erosion caused when carbon dioxide gas escapes from under the seasonal ice layer carrying fine material from the surface. The dark fans in this image are made up of small particles from the surface deposited on top of the seasonal layer of ice. The fans originate at a crack, a weak spot that allows the gas to escape. The material is deposited in a direction determined by the direction of the wind as the gas was escaping. http://photojournal.jpl.nasa.gov/catalog/PIA19292

Spiders from Mars?

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-426, 19 July 2003

No, this is not a picture of a giant, martian spider web. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a plethora of polygonal features on the floor of a northern hemisphere impact crater near 65.6oN, 327.7oW. The picture was acquired during spring, after the seasonal carbon dioxide frost cap had largely migrated through the region. At the time the picture was taken, remnants of seasonal frost remained on the crater rim and on the edges of the troughs that bound each of the polygons. Frost often provides a helpful hint as to where polygons and patterned ground occur. The polygons, if they were on Earth, would indicate the presence of freeze-thaw cycles in ground ice. Although uncertain, the same might be true of Mars. Sunlight illuminates the scene from the lower left.

Predictive habitat modelling of humpback (Megaptera novaeangliae) and Antarctic minke (Balaenoptera bonaerensis) whales in the Southern Ocean as a planning tool for seismic surveys

NASA Astrophysics Data System (ADS)

Bombosch, Annette; Zitterbart, Daniel P.; Van Opzeeland, Ilse; Frickenhaus, Stephan; Burkhardt, Elke; Wisz, Mary S.; Boebel, Olaf

2014-09-01

Seismic surveys are frequently a matter of concern regarding their potentially negative impacts on marine mammals. In the Southern Ocean, which provides a critical habitat for several endangered cetacean species, seismic research activities are undertaken at a circumpolar scale. In order to minimize impacts of these surveys, pre-cruise planning requires detailed, spatio-temporally resolved knowledge on the likelihood of encountering these species in the survey area. In this publication we present predictive habitat modelling as a potential tool to support decisions for survey planning. We associated opportunistic sightings (2005-2011) of humpback (Megaptera novaeangliae, N=93) and Antarctic minke whales (Balaenoptera bonaerensis, N=139) with a range of static and dynamic environmental variables. A maximum entropy algorithm (Maxent) was used to develop habitat models and to calculate daily basinwide/circumpolar prediction maps to evaluate how species-specific habitat conditions evolved throughout the spring and summer months. For both species, prediction maps revealed considerable changes in habitat suitability throughout the season. Suitable humpback whale habitat occurred predominantly in ice-free areas, expanding southwards with the retreating sea ice edge, whereas suitable Antarctic minke whale habitat was consistently predicted within sea ice covered areas. Daily, large-scale prediction maps provide a valuable tool to design layout and timing of seismic surveys as they allow the identification and consideration of potential spatio-temporal hotspots to minimize potential impacts of seismic surveys on Antarctic cetacean species.

An ice-ocean coupled model for the Northern Hemisphere

NASA Technical Reports Server (NTRS)

Cheng, Abe; Preller, Ruth

1992-01-01

The Hibler ice model has been modified and adapted to a domain that includes most of the sea ice-covered areas in the Northern Hemisphere. This model, joined with the Cox ocean model, is developed as an enhancement to the U.S. Navy's sea ice forecasting, PIPS, and is termed PIPS2.0. Generally, the modeled ice edge is consistent with the Navy-NOAA Joint Ice Center weekly analysis, and the modeled ice thickness distribution agrees with submarine sonar data in the central Arctic basin.

Sea ice and oceanic processes on the Ross Sea continental shelf

NASA Astrophysics Data System (ADS)

Jacobs, S. S.; Comiso, J. C.

1989-12-01

We have investigated the spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf, in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86% during winter with little month-to-month or interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn. Newly identified Pennell and Ross Passage polynyas near the continental shelf break appear to be maintained in part by divergence above a submarine bank and by upwelling of warmer water near the slope front. Warmer subsurface water enters the shelf region year-round and will retard ice growth and enhance heat flux to the atmosphere when entrained in the strong winter vertical circulation. Temperatures at 125-m depth on a mooring near the Ross Ice Shelf during July 1984 averaged 0.15°C above freezing, sufficient to support a vertical heat flux above 100 W/m2. Monthly average subsurface ocean temperatures along the Ross Ice Shelf lag the air temperature cycle and begin to rise several weeks before spring ice breakout. The coarse SMMR resolution and dynamic ice shelf coastlines can compromise the use of microwave sea ice data near continental boundaries.

Use of SAR imagery and other remotely-sensed data in deriving ice information during a severe ice event on the Grand Banks (Newfoundland)

NASA Technical Reports Server (NTRS)

Carsey, F. D.; Argus, S. D.

1988-01-01

Image data from synthetic aperture radar (SAR) are used to observe an ice compaction event off the East Coast of Newfoundland in spring, 1987. The information developed from sequential SAR observations is shown to do a remarkably effective job of describing the ice conditions; the difficult variable is the ice thickness which is found to be surprisingly large (2 to 4 times the thickness predictable from thermodynamic growth alone). It may be possible to model the ice thickness using SAR-derived ice motion.

Spring Melt and the Redistribution of Organochlorine Pesticides in the Sea-Ice Environment: A Comparative Study between Arctic and Antarctic Regions.

PubMed

Bigot, Marie; Hawker, Darryl W; Cropp, Roger; Muir, Derek Cg; Jensen, Bjarne; Bossi, Rossana; Bengtson Nash, Susan M

2017-08-15

Complementary sampling of air, snow, sea-ice, and seawater for a range of organochlorine pesticides (OCPs) was undertaken through the early stages of respective spring sea-ice melting at coastal sites in northeast Greenland and eastern Antarctica to investigate OCP concentrations and redistribution during this time. Mean concentrations in seawater, sea-ice and snow were generally greater at the Arctic site. For example, α-HCH was found to have the largest concentrations of all analytes in Arctic seawater and sea-ice meltwater samples (224-253 and 34.7-48.2 pg·L -1 respectively compared to 1.0-1.3 and <0.63 pg·L -1 respectively for Antarctic samples). Differences in atmospheric samples were generally not as pronounced however. Findings suggest that sea-ice OCP burdens originate from both snow and seawater. The distribution profile between seawater and sea-ice showed a compound-dependency for Arctic samples not evident with those from the Antarctic, possibly due to full submersion of sea-ice at the former. Seasonal sea-ice melt processes may alter the exchange rates of selected OCPs between air and seawater, but are not expected to reverse their direction, which fugacity modeling indicates is volatilisation in the Arctic and net deposition in the Antarctic. These predictions are consistent with the limited current observations.

Acquisition of Ice Thickness and Ice Surface Characteristics in the Seasonal Ice Zone by CULPIS-X During the US Coast Guard’s Arctic Domain Awareness Program

DTIC Science & Technology

2013-09-30

What is the volume of sea ice in the Beaufort Sea SIZ and how does this evolve during summer as the ice edge retreats? Recent observations...suggest that the remaining ice in the Beaufort Sea is younger and thinner in recent years in part because even the oldest ice advected into the region does...indicated that ponds on thinner ice are often darker, accelerating the ice - albedo feedback over thin ice in summer. During winter, leads and very

Decadal-Scale Changes of Dinoflagellates and Diatoms in the Anomalous Baltic Sea Spring Bloom

PubMed Central

Klais, Riina; Tamminen, Timo; Kremp, Anke; Spilling, Kristian; Olli, Kalle

2011-01-01

The algal spring bloom in the Baltic Sea represents an anomaly from the winter-spring bloom patterns worldwide in terms of frequent and recurring dominance of dinoflagellates over diatoms. Analysis of approximately 3500 spring bloom samples from the Baltic Sea monitoring programs revealed (i) that within the major basins the proportion of dinoflagellates varied from 0.1 (Kattegat) to >0.8 (central Baltic Proper), and (ii) substantial shifts (e.g. from 0.2 to 0.6 in the Gulf of Finland) in the dinoflagellate proportion over four decades. During a recent decade (1995–2004) the proportion of dinoflagellates increased relative to diatoms mostly in the northernmost basins (Gulf of Bothnia, from 0.1 to 0.4) and in the Gulf of Finland, (0.4 to 0.6) which are typically ice-covered areas. We hypothesize that in coastal areas a specific sequence of seasonal events, involving wintertime mixing and resuspension of benthic cysts, followed by proliferation in stratified thin layers under melting ice, favors successful seeding and accumulation of dense dinoflagellate populations over diatoms. This head-start of dinoflagellates by the onset of the spring bloom is decisive for successful competition with the faster growing diatoms. Massive cyst formation and spreading of cyst beds fuel the expanding and ever larger dinoflagellate blooms in the relatively shallow coastal waters. Shifts in the dominant spring bloom algal groups can have significant effects on major elemental fluxes and functioning of the Baltic Sea ecosystem, but also in the vast shelves and estuaries at high latitudes, where ice-associated cold-water dinoflagellates successfully compete with diatoms. PMID:21747911

Decadal-scale changes of dinoflagellates and diatoms in the anomalous baltic sea spring bloom.

PubMed

Klais, Riina; Tamminen, Timo; Kremp, Anke; Spilling, Kristian; Olli, Kalle

2011-01-01

The algal spring bloom in the Baltic Sea represents an anomaly from the winter-spring bloom patterns worldwide in terms of frequent and recurring dominance of dinoflagellates over diatoms. Analysis of approximately 3500 spring bloom samples from the Baltic Sea monitoring programs revealed (i) that within the major basins the proportion of dinoflagellates varied from 0.1 (Kattegat) to >0.8 (central Baltic Proper), and (ii) substantial shifts (e.g. from 0.2 to 0.6 in the Gulf of Finland) in the dinoflagellate proportion over four decades. During a recent decade (1995-2004) the proportion of dinoflagellates increased relative to diatoms mostly in the northernmost basins (Gulf of Bothnia, from 0.1 to 0.4) and in the Gulf of Finland, (0.4 to 0.6) which are typically ice-covered areas. We hypothesize that in coastal areas a specific sequence of seasonal events, involving wintertime mixing and resuspension of benthic cysts, followed by proliferation in stratified thin layers under melting ice, favors successful seeding and accumulation of dense dinoflagellate populations over diatoms. This head-start of dinoflagellates by the onset of the spring bloom is decisive for successful competition with the faster growing diatoms. Massive cyst formation and spreading of cyst beds fuel the expanding and ever larger dinoflagellate blooms in the relatively shallow coastal waters. Shifts in the dominant spring bloom algal groups can have significant effects on major elemental fluxes and functioning of the Baltic Sea ecosystem, but also in the vast shelves and estuaries at high latitudes, where ice-associated cold-water dinoflagellates successfully compete with diatoms.

Breakup of Pack Ice, Antarctic Ice Shelf

NASA Image and Video Library

1991-09-18

STS048-152-007 (12-18 Sept 1991) --- The periphery of the Antarctic ice shelf and the Antarctic Peninsula were photographed by the STS 48 crew members. Strong offshore winds, probably associated with katabatic winds from the interior of the continent, are peeling off the edges of the ice shelf into ribbons of sea ice, icebergs, bergy bits and growlers into the cold waters of the circum-Antarctic southern ocean.

Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration

NASA Astrophysics Data System (ADS)

Edinburgh, Tom; Day, Jonathan J.

2016-11-01

In stark contrast to the sharp decline in Arctic sea ice, there has been a steady increase in ice extent around Antarctica during the last three decades, especially in the Weddell and Ross seas. In general, climate models do not to capture this trend and a lack of information about sea ice coverage in the pre-satellite period limits our ability to quantify the sensitivity of sea ice to climate change and robustly validate climate models. However, evidence of the presence and nature of sea ice was often recorded during early Antarctic exploration, though these sources have not previously been explored or exploited until now. We have analysed observations of the summer sea ice edge from the ship logbooks of explorers such as Robert Falcon Scott, Ernest Shackleton and their contemporaries during the Heroic Age of Antarctic Exploration (1897-1917), and in this study we compare these to satellite observations from the period 1989-2014, offering insight into the ice conditions of this period, from direct observations, for the first time. This comparison shows that the summer sea ice edge was between 1.0 and 1.7° further north in the Weddell Sea during this period but that ice conditions were surprisingly comparable to the present day in other sectors.

Ocean-ice interaction in the marginal ice zone

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Peng, Chich Y.

1994-01-01

Ocean ice interaction processes in the Marginal Ice Zone (MIZ) by wind, waves, and mesoscale features, such as upwelling and eddies, are studied using ERS-1 Synthetic Aperture Radar (SAR) images and ocean ice interaction model. A sequence of SAR images of the Chukchi Sea MIZ with three days interval are studied 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.

An experimental investigation of multi-element airfoil ice accretion and resulting performance degradation

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Berkowitz, Brian M.

1989-01-01

An investigation of the ice accretion pattern and performance characteristics of a multi-element airfoil was undertaken in the NASA Lewis 6- by 9-Foot Icing Research Tunnel. Several configurations of main airfoil, slat, and flaps were employed to examine the effects of ice accretion and provide further experimental information for code validation purposes. The text matrix consisted of glaze, rime, and mixed icing conditions. Airflow and icing cloud conditions were set to correspond to those typical of the operating environment anticipated tor a commercial transport vehicle. Results obtained included ice profile tracings, photographs of the ice accretions, and force balance measurements obtained both during the accretion process and in a post-accretion evaluation over a range of angles of attack. The tracings and photographs indicated significant accretions on the slat leading edge, in gaps between slat or flaps and the main wing, on the flap leading-edge surfaces, and on flap lower surfaces. Force measurments indicate the possibility of severe performance degradation, especially near C sub Lmax, for both light and heavy ice accretion and performance analysis codes presently in use. The LEWICE code was used to evaluate the ice accretion shape developed during one of the rime ice tests. The actual ice shape was then evaluated, using a Navier-Strokes code, for changes in performance characteristics. These predicted results were compared to the measured results and indicate very good agreement.

Spring Slide

NASA Image and Video Library

2013-10-30

The North Polar region of Mars is capped with layers of water ice and dust, called the polar layered deposits. This permanent polar cap is covered in the winter with a layer of seasonal carbon dioxide ice as seen by NASA Mars Reconnaissance Orbiter.

Parallel algorithm for determining motion vectors in ice floe images by matching edge features

NASA Technical Reports Server (NTRS)

Manohar, M.; Ramapriyan, H. K.; Strong, J. P.

1988-01-01

A parallel algorithm is described to determine motion vectors of ice floes using time sequences of images of the Arctic ocean obtained from the Synthetic Aperture Radar (SAR) instrument flown on-board the SEASAT spacecraft. Researchers describe a parallel algorithm which is implemented on the MPP for locating corresponding objects based on their translationally and rotationally invariant features. The algorithm first approximates the edges in the images by polygons or sets of connected straight-line segments. Each such edge structure is then reduced to a seed point. Associated with each seed point are the descriptions (lengths, orientations and sequence numbers) of the lines constituting the corresponding edge structure. A parallel matching algorithm is used to match packed arrays of such descriptions to identify corresponding seed points in the two images. The matching algorithm is designed such that fragmentation and merging of ice floes are taken into account by accepting partial matches. The technique has been demonstrated to work on synthetic test patterns and real image pairs from SEASAT in times ranging from .5 to 0.7 seconds for 128 x 128 images.

Late summer and fall wave climate in the Beaufort and Chukchi Seas, 2000-2014

NASA Astrophysics Data System (ADS)

Fan, Y.; Rogers, W.; Thomson, J.; Stopa, J.

2016-02-01

Jim Thomson, Applied Physics Laboratory, University of Washington, Seattle, WA According to IPCC, "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world." Some regions within the Arctic have warmed even more rapidly, with Alaska and western Canada's temperature rising by 3 to 4 °C (5.40 to 7.20 °F). Arctic ice is getting thinner, melting and rupturing. The polar ice cap as a whole is shrinking. Images from NASA satellites show that the area of permanent ice cover is contracting at a rate of 9 percent each decade. If this trend continues, summers in the Arctic could become ice-free by the end of the century. Arctic storms thus have the potential to create large waves in the region. Ocean waves can also penetrate remarkable distances into ice fields and impact sea-ice thermodynamics by breaking up ice floes and accelerating ice melting during the summer (Asplin et al 2012); or influencing sea-ice growth and hence the morphology of the mature ice sheet during the winter (Lange et al 1989). Waves breaking on the shore could also affect the coastlines, where melting permafrost is already making shores more vulnerable to erosion. Preliminary wave model results from four selected years suggests that the sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. In particular, larger waves are more common in years with low or late sea ice cover. Trends in amount of wave energy impinging on the ice edge, however, are inconclusive. To better understand the potential effect of surface wave on the advance/retreat of ice edges and the coastlines. 15 years (2000 to 2014) of surface wave simulations in the Arctic Ocean using WAVEWATCH III will be conducted. Wind and ice forcing are obtained from the ERA-interim global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). Wave energy flux arriving at the ice edges and land boundaries will be analyzed and histograms and fitted Weibull probability distribution functions will used to identify similarities and differences during the 15 year period. The potential effect of surface waves on ice advance/retreat and land erosion will be explored and discussed.

Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century.

PubMed

Castro de la Guardia, Laura; Derocher, Andrew E; Myers, Paul G; Terwisscha van Scheltinga, Arjen D; Lunn, Nick J

2013-09-01

The primary habitat of polar bears is sea ice, but in Western Hudson Bay (WH), the seasonal ice cycle forces polar bears ashore each summer. Survival of bears on land in WH is correlated with breakup and the ice-free season length, and studies suggest that exceeding thresholds in these variables will lead to large declines in the WH population. To estimate when anthropogenic warming may have progressed sufficiently to threaten the persistence of polar bears in WH, we predict changes in the ice cycle and the sea ice concentration (SIC) in spring (the primary feeding period of polar bears) with a high-resolution sea ice-ocean model and warming forced with 21st century IPCC greenhouse gas (GHG) emission scenarios: B1 (low), A1B (medium), and A2 (high). We define critical years for polar bears based on proposed thresholds in breakup and ice-free season and we assess when ice-cycle conditions cross these thresholds. In the three scenarios, critical years occur more commonly after 2050. From 2001 to 2050, 2 critical years occur under B1 and A2, and 4 under A1B; from 2051 to 2100, 8 critical years occur under B1, 35 under A1B and 41 under A2. Spring SIC in WH is high (>90%) in all three scenarios between 2001 and 2050, but declines rapidly after 2050 in A1B and A2. From 2090 to 2100, the mean spring SIC is 84 (±7)% in B1, 56 (±26)% in A1B and 20 (±13)% in A2. Our predictions suggest that the habitat of polar bears in WH will deteriorate in the 21st century. Ice predictions in A1B and A2 suggest that the polar bear population may struggle to persist after ca. 2050. Predictions under B1 suggest that reducing GHG emissions could allow polar bears to persist in WH throughout the 21st century. © 2013 John Wiley & Sons Ltd.

A novel method for automated grid generation of ice shapes for local-flow analysis

NASA Astrophysics Data System (ADS)

Ogretim, Egemen; Huebsch, Wade W.

2004-02-01

Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading-edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine-cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness.

Navier-Stokes analysis of airfoils with leading edge ice accretions

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.

1993-01-01

A numerical analysis of the flowfield characteristics and the performance degradation of an airfoil with leading edge ice accretions was performed. The important fluid dynamic processes were identified and calculated. Among these were the leading edge separation bubble at low angles of attack, complete separation on the low pressure surface resulting in premature shell, drag rise due to the ice shape, and the effects of angle of attack on the separated flow field. Comparisons to experimental results were conducted to confirm these calculations. A computer code which solves the Navier-Stokes equations in two dimensions, ARC2D, was used to perform the calculations. A Modified Mixing Length turbulence model was developed to produce grids for several ice shape and airfoil combinations. Results indicate that the ability to predict overall performance characteristics, such as lift and drag, at low angles of attack is excellent. Transition location is important for accurately determining separation bubble shape. Details of the flowfield in and downstream of the separated regions requires some modifications. Calculations for the stalled airfoil indicate periodic shedding of vorticity that was generated aft of the ice accretion. Time averaged pressure values produce results which compare favorably with experimental information. A turbulence model which accounts for the history effects in the flow may be justified.

Icebergs Adrift in the Amundsen Sea

NASA Image and Video Library

2002-03-27

The Thwaites Ice Tongue is a large sheet of glacial ice extending from the West Antarctic mainland into the southern Amundsen Sea. A large crack in the Thwaites Tongue was discovered in imagery from Terra's Moderate Resolution Imaging SpectroRadiometer (MODIS). Subsequent widening of the crack led to the calving of a large iceberg. The development of this berg, designated B-22 by the National Ice Center, can be observed in these images from the Multi-angle Imaging SpectroRadiometer, also aboard Terra. The two views were acquired by MISR's nadir (vertical-viewing) camera on March 10 and 24, 2002. The B-22 iceberg, located below and to the left of image center, measures approximately 82 kilometers long x 62 kilometers wide. Comparison of the two images shows the berg to have drifted away from the ice shelf edge. The breakup of ice near the shelf edge, in the area surrounding B-22, is also visible in the later image. These natural-color images were acquired during Terra orbits 11843 and 12047, respectively. At the right-hand edge is Pine Island Bay, where the calving of another large iceberg (B-21) occurred in November 2001. B-21 subsequently split into two smaller bergs, both of which are visible to the right of B-22. http://photojournal.jpl.nasa.gov/catalog/PIA03700

Flexible Volumetric Structure

NASA Technical Reports Server (NTRS)

Cagle, Christopher M. (Inventor); Schlecht, Robin W. (Inventor)

2014-01-01

A flexible volumetric structure has a first spring that defines a three-dimensional volume and includes a serpentine structure elongatable and compressible along a length thereof. A second spring is coupled to at least one outboard edge region of the first spring. The second spring is a sheet-like structure capable of elongation along an in-plane dimension thereof. The second spring is oriented such that its in-plane dimension is aligned with the length of the first spring's serpentine structure.

Short-term sea ice forecasting: An assessment of ice concentration and ice drift forecasts using the U.S. Navy's Arctic Cap Nowcast/Forecast System

NASA Astrophysics Data System (ADS)

Hebert, David A.; Allard, Richard A.; Metzger, E. Joseph; Posey, Pamela G.; Preller, Ruth H.; Wallcraft, Alan J.; Phelps, Michael W.; Smedstad, Ole Martin

2015-12-01

In this study the forecast skill of the U.S. Navy operational Arctic sea ice forecast system, the Arctic Cap Nowcast/Forecast System (ACNFS), is presented for the period February 2014 to June 2015. ACNFS is designed to provide short term, 1-7 day forecasts of Arctic sea ice and ocean conditions. Many quantities are forecast by ACNFS; the most commonly used include ice concentration, ice thickness, ice velocity, sea surface temperature, sea surface salinity, and sea surface velocities. Ice concentration forecast skill is compared to a persistent ice state and historical sea ice climatology. Skill scores are focused on areas where ice concentration changes by ±5% or more, and are therefore limited to primarily the marginal ice zone. We demonstrate that ACNFS forecasts are skilful compared to assuming a persistent ice state, especially beyond 24 h. ACNFS is also shown to be particularly skilful compared to a climatologic state for forecasts up to 102 h. Modeled ice drift velocity is compared to observed buoy data from the International Arctic Buoy Programme. A seasonal bias is shown where ACNFS is slower than IABP velocity in the summer months and faster in the winter months. In February 2015, ACNFS began to assimilate a blended ice concentration derived from Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Interactive Multisensor Snow and Ice Mapping System (IMS). Preliminary results show that assimilating AMSR2 blended with IMS improves the short-term forecast skill and ice edge location compared to the independently derived National Ice Center Ice Edge product.

Helicopter rotor noise investigation during ice accretion

NASA Astrophysics Data System (ADS)

Cheng, Baofeng

An investigation of helicopter rotor noise during ice accretion is conducted using experimental, theoretical, and numerical methods. This research is the acoustic part of a joint helicopter rotor icing physics, modeling, and detection project at The Pennsylvania State University Vertical Lift Research Center of Excellence (VLRCOE). The current research aims to provide acoustic insight and understanding of the rotor icing physics and investigate the feasibility of detecting rotor icing through noise measurements, especially at the early stage of ice accretion. All helicopter main rotor noise source mechanisms and their change during ice accretion are discussed. Changes of the thickness noise, steady loading noise, and especially the turbulent boundary layer - trailing edge (TBL-TE) noise due to ice accretion are identified and studied. The change of the discrete frequency noise (thickness noise and steady loading noise) due to ice accretion is calculated by using PSU-WOPWOP, an advanced rotorcraft acoustic prediction code. The change is noticeable, but too small to be used in icing detection. The small thickness noise change is due to the small volume of the accreted ice compared to that of the entire blade, although a large iced airfoil shape is used. For the loading noise calculation, two simplified methods are used to generate the loading on the rotor blades, which is the input for the loading noise calculation: 1) compact loading from blade element momentum theory, icing effects are considered by increasing the drag coefficient; and 2) pressure loading from the 2-D CFD simulation, icing effects are considered by using the iced airfoil shape. Comprehensive rotor broadband noise measurements are carried out on rotor blades with different roughness sizes and rotation speeds in two facilities: the Adverse Environment Rotor Test Stand (AERTS) facility at The Pennsylvania State University, and The University of Maryland Acoustic Chamber (UMAC). In both facilities the measured high-frequency broadband noise increases significantly with increasing surface roughness heights, which indicates that it is feasible to quantify helicopter rotor ice-induced surface roughness through acoustic measurements. Comprehensive broadband noise measurements based on different accreted ice roughness at AERTS are then used to form the data base from which a correlation between the ice-induced surface roughness and the broadband noise level is developed. Two parameters, the arithmetic average roughness height, Ra, and the averaged roughness height, based on the integrated ice thickness at the blade tip, are introduced to describe the ice-induced surface roughness at the early stage of the ice accretion. The ice roughness measurements are correlated to the measured broadband noise level. Strong correlations (absolute mean deviations of 9.3% and 11.2% for correlation using Ra and the averaged roughness height respectively) between the ice roughness and the broadband noise level are obtained, which can be used as a tool to determine the accreted ice roughness in the AERTS facility through acoustic measurement. It might be possible to use a similar approach to develop an early ice accretion detection tool for helicopters, as well as to quantify the ice-induced roughness at the early stage of rotor ice accretion. Rotor broadband noise source identification is conducted and the broadband noise related to ice accretion is argued to be turbulent boundary layer - trailing edge (TBL-TE) noise. Theory suggests TBL-TE noise scales with Mach number to the fifth power, which is also observed in the experimental data. The trailing edge noise theories developed by Ffowcs Williams and Hall, and Howe both identify two important parameters: boundary layer thickness and turbulence intensity. Numerical studies of 2-D airfoils with different ice-induced surface roughness heights are conducted to investigate the extent that surface roughness impacts the boundary layer thickness and turbulence intensity (and ultimately the TBL-TE noise). The results show that boundary layer thickness and turbulence intensity at the trailing edge increase with the increased roughness height. Using Howe's trailing edge noise model, the increased sound pressure level (SPL) of the trailing edge noise due to the increased displacement thickness and normalized integrated turbulence intensity are 6.2 dB and 1.6 dB for large and small accreted ice roughness heights, respectively. The estimated increased SPL values agree well with the experimental results, which are 5.8 dB and 2.6 dB for large and small roughness height, respectively. Finally a detailed broadband noise spectral scaling for all measured broadband noise in both AERTS and UMAC facilities is conducted. The magnitude and the frequency spectrum of the measured broadband noise are scaled on characteristic velocity and length. The peak of the laminar boundary layer - vortex shedding (LBL-VS) noise coalesces well on the Strouhal scaling in those cases. For the measured broadband noise from a rotor with relatively large roughness heights, no contribution of the LBL-VS noise is observed. The velocity scaling shows that the TBL-TE noise, which is the dominant source mechanism, scales with Mach number to the fifth power based on the absolute frequency. The length scaling shows that the TBL-TE noise scales well on the absolute roughness height based on Howe's TE noise theory.

Interannual variation in seasonal diatom dynamics - what information is preserved in an annual sediment record?

NASA Astrophysics Data System (ADS)

Maier, D. B.; Bigler, C.; Diehl, S.

2017-12-01

Diatom sediment assemblages are among the most important proxies for past climate and ecological condition reconstruction in aquatic environments, but the role of seasonality in the formation of diatom records is poorly understood. In this study we combine the diatom record of a varved sediment with year-round physico-chemical water column monitoring and the corresponding sequential sediment trap diatom record to disentangle the process information contained in a diatom sediment signal. The comparison of three consecutive annual diatom records indicates that the entire annual diatom sediment signal can be driven by winter air temperature induced timing of ice and snow melt and persistent under-ice stratification promoting an early diatom bloom under ice before spring lake over-turn. By contrast, in a year of late ice thinning when the chlorophyll a maximum occurred after spring lake over-turn, a more annually integrated diatom sediment signal was built buy a continuous diatom flux. The contrasting diatom records produced during years of different winter conditions have important implications for diatom based paleoecological reconstructions. Decadal records of sediment trap samples as well as long-term varved sediment records provide further support for the role of late winter and early spring weather conditions in determining sediment diatom assemblages.

Long-term record of Barents Sea Ice Sheet advance to the shelf edge from a 140,000 year record

NASA Astrophysics Data System (ADS)

Pope, Ed L.; Talling, Peter J.; Hunt, James E.; Dowdeswell, Julian A.; Allin, Joshua R.; Cartigny, Matthieu J. B.; Long, David; Mozzato, Alessandro; Stanford, Jennifer D.; Tappin, David R.; Watts, Millie

2016-10-01

The full-glacial extent and deglacial behaviour of marine-based ice sheets, such as the Barents Sea Ice Sheet, is well documented since the Last Glacial Maximum about 20,000 years ago. However, reworking of older sea-floor sediments and landforms during repeated Quaternary advances across the shelf typically obscures their longer-term behaviour, which hampers our understanding. Here, we provide the first detailed long-term record of Barents Sea Ice Sheet advances, using the timing of debris-flows on the Bear Island Trough-Mouth Fan. Ice advanced to the shelf edge during four distinct periods over the last 140,000 years. By far the largest sediment volumes were delivered during the oldest advance more than 128,000 years ago. Later advances occurred from 68,000 to 60,000, 39,400 to 36,000 and 26,000 to 20,900 years before present. The debris-flows indicate that the dynamics of the Saalian and the Weichselian Barents Sea Ice Sheet were very different. The repeated ice advance and retreat cycles during the Weichselian were shorter lived than those seen in the Saalian. Sediment composition shows the configuration of the ice sheet was also different between the two glacial periods, implying that the ice feeding the Bear Island Ice stream came predominantly from Scandinavia during the Saalian, whilst it drained more ice from east of Svalbard during the Weichselian.

Operationally Merged Satellite Visible/IR and Passive Microwave Sea Ice Information for Improved Sea Ice Forecasts and Ship Routing

DTIC Science & Technology

2015-09-30

microwave sea ice information for improved sea ice forecasts and ship routing W. Meier NASA Goddard Space Flight Center, Cryospheric Sciences Laboratory...updating the initial ice concentration analysis fields along the ice edge. In the past year, NASA Goddard and NRL have generated a merged 4 km AMSR-E...collaborations of three groups: NASA Goddard Space Flight Center ( NASA /GSFC) in Greenbelt, MD, NRL/Oceanography Division located at Stennis Space Center (SSC

Influence of the sea-ice edge on the Arctic nearshore environment

NASA Astrophysics Data System (ADS)

Barnhart, K. R.; Overeem, I.; Anderson, R. S.

2013-12-01

Coasts form the dynamic interface of the terrestrial and oceanic systems. In the Arctic, and in much of the world, the coast is a zone of relatively high population, infrastructure, biodiversity, and ecosystem services. A significant difference between Arctic and temperate coasts is the presence of sea ice. Sea ice influences Arctic coasts in two main ways: (1) the length of the sea ice-free season controls the length of time over which nearshore water can interact with the land, and (2) the sea ice edge controls the fetch over which storm winds can blow over open water, resulting in changes in nearshore water level and wave field. The resulting nearshore hydrodynamic environment impacts all aspects of the coastal system. Here, we use satellite records of sea ice along with a simple model for wind-driven storm surge and waves to document how changes in the length and character of the sea ice-free season have impacted the nearshore hydrodynamic environment. For our sea ice analysis we primarily use the Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS. We make whole-Arctic maps of sea ice change in the coastal zone. In addition to evaluating changes in length of the sea ice-free season at the coast, we look at changes segmented by azimuth. This allows us to consider changes in the sea ice in the context of the wind field. For our storm surge and wave field analysis we focus on the Beaufort Sea region. This region has experienced some of the greatest changes in both sea ice cover and coastal erosion rates in the Arctic and is anticipated to experience significant change in the future. In addition, the NOAA ESRL GMD has observed the wind field at Barrow since extends to 1977. In our past work on the rapid and accelerating coastal erosion, we have shown that one may model storm surge with a 2D numerical bathystrophic model, and that waves are well represented by the Shore Protection Manual methods for shallow-water fetch-limited waves. We use these models to explore the effect of increasing fetch on water level set up and wave generation. As increasing the fetch is one of the main effects of the changing sea ice cover, this allows us to connect changes in the sea ice cover to changes in the nearshore hydrodynamic environment. The long wind record allows for us to investigate changes in extreme wind and associated storm events. Preliminary analysis of Barrow and Drew Point indicate that at Drew Point the sea ice-free season has expanded by ˜17 days/decade while at Barrow it has expanded by ˜22 days/decade. We find the increase in the number of days when the sea ice edge is far away from the coast makes up a large proportion of the total increase in the duration of the sea ice-free season. For these days the sea ice edge does not provide a limit on the fetch over which water level set up and waves are generated.

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

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Manufacture of conical springs with elastic medium technology improvement

NASA Astrophysics Data System (ADS)

Kurguzov, S. A.; Mikhailova, U. V.; Kalugina, O. B.

2018-01-01

This article considers the manufacturing technology improvement by using an elastic medium in the stamping tool forming space to improve the conical springs performance characteristics and reduce the costs of their production. Estimation technique of disk spring operational properties is developed by mathematical modeling of the compression process during the operation of a spring. A technique for optimizing the design parameters of a conical spring is developed, which ensures a minimum voltage value when operated in the edge of the spring opening.

A dynamic spar numerical model for passive shape change

NASA Astrophysics Data System (ADS)

Calogero, J. P.; Frecker, M. I.; Hasnain, Z.; Hubbard, J. E., Jr.

2016-10-01

A three-dimensional constraint-driven dynamic rigid-link numerical model of a flapping wing structure with compliant joints (CJs) called the dynamic spar numerical model is introduced and implemented. CJs are modeled as spherical joints with distributed mass and spring-dampers with coupled nonlinear spring and damping coefficients, which models compliant mechanisms spatially distributed in the structure while greatly reducing computation time compared to a finite element model. The constraints are established, followed by the formulation of a state model used in conjunction with a forward time integrator, an experiment to verify a rigid-link assumption and determine a flapping angle function, and finally several example runs. Modeling the CJs as coupled bi-linear springs shows the wing is able to flex more during upstroke than downstroke. Coupling the spring stiffnesses allows an angular deformation about one axis to induce an angular deformation about another axis, where the magnitude is proportional to the coupling term. Modeling both the leading edge and diagonal spars shows that the diagonal spar changes the kinematics of the leading edge spar verses only considering the leading edge spar, causing much larger axial rotations in the leading edge spar. The kinematics are very sensitive to CJ location, where moving the CJ toward the wing root causes a stronger response, and adding multiple CJs on the leading edge spar with a CJ on the diagonal spar allows the wing to deform with larger magnitude in all directions. This model lays a framework for a tool which can be used to understand flapping wing flight.

Air-ice CO2 fluxes and pCO2 dynamics in the Arctic coastal area (Amundsen Gulf, Canada)

NASA Astrophysics Data System (ADS)

Geilfus, Nicolas-Xavier; Tison, Jean Louis; Carnat, Gauthier; Else, Brent; Borges, Alberto V.; Thomas, Helmuth; Shadwick, Elizabeth; Delille, Bruno

2010-05-01

Sea ice covers about 7% of the Earth surface at its maximum seasonal extent. For decades sea ice was assumed to be an impermeable and inert barrier for air - sea exchange of CO2 so that global climate models do not include CO2 exchange between the oceans and the atmosphere in the polar regions. However, uptake of atmospheric CO2 by sea ice cover was recently reported raising the need to further investigate pCO2 dynamics in the marine cryosphere realm and related air-ice CO2 fluxes. In addition, budget of CO2 fluxes are poorly constrained in high latitudes continental shelves [Borges et al., 2006]. We report measurements of air-ice CO2 fluxes above the Canadian continental shelf and compare them to previous measurements carried out in Antarctica. We carried out measurements of pCO2 within brines and bulk ice, and related air-ice CO2 fluxes (chamber method) in Antarctic first year pack ice ("Sea Ice Mass Balance in Antarctica -SIMBA" drifting station experiment September - October 2007) and in Arctic first year land fast ice ("Circumpolar Flaw Lead" - CFL, April - June 2008). These 2 experiments were carried out in contrasted sites. SIMBA was carried out on sea ice in early spring while CFL was carried out in from the middle of the winter to the late spring while sea ice was melting. Both in Arctic and Antarctic, no air-ice CO2 fluxes were detected when sea ice interface was below -10°C. Slightly above -10°C, fluxes toward the atmosphere were observed. In contrast, at -7°C fluxes from the atmosphere to the ice were significant. The pCO2 of the brine exhibits a same trend in both hemispheres with a strong decrease of the pCO2 anti-correlated with the increase of sea ice temperature. The pCO2 shifted from a large over-saturation at low temperature to a marked under-saturation at high temperature. These air-ice CO2 fluxes are partly controlled by the permeability of the air-ice interface, which depends of the temperature of this one. Moreover, air-ice CO2 fluxes are driven by the air-ice pCO2 gradient. Hence, while the temperature is a leading factor in controlling magnitude of air-ice CO2 fluxes, pCO2 of the ice controls both magnitude and direction of fluxes. However, pCO2 in Arctic is significantly higher than in Antarctica. This difference could be due to a higher level of organic matter in Arctic. The degradation of this organic matter fuel CO2 efflux from the ice to the atmosphere in early spring. We observed evidence of CaCO3 precipitation, but only at the top of the ice. Implications in term of air-ice CO2 transfer of such CaCO3 precipitation will be discussed. In addition, salt-rich snow appears to strongly affect air-ice CO2 fluxes in the arctic. Borges, A. V., et al. (2006), Carbon dioxide in European coastal waters, Estuar. Coast. Shelf Sci., 70(3), 375-387.

Atmospheric Modeling of the Martian Polar Regions: CRISM EPF Coverage During the South Polar Spring Recession

NASA Astrophysics Data System (ADS)

Brown, A. J.; McGuire, P.; Wolff, M. J.

2008-03-01

We describe efforts to model dust and ice aerosols content and soils and icy surface reflectance in the Martian southern polar region during spring recession (Ls = 152-320) using CRISM emission phase function (EPF) observations.

Linear magnetic spring and spring/motor combination

NASA Technical Reports Server (NTRS)

Patt, Paul J. (Inventor); Stolfi, Fred R. (Inventor)

1991-01-01

A magnetic spring, or a spring and motor combination, providing a linear spring force characteristic in each direction from a neutral position, in which the spring action may occur for any desired coordinate of a typical orthogonal coordinate system. A set of magnets are disposed, preferably symmetrically about a coordinate axis, poled orthogonally to the desired force direction. A second set of magnets, respectively poled opposite the first set, are arranged on the sprung article. The magnets of one of the sets are spaced a greater distance apart than those of the other, such that an end magnet from each set forms a pair having preferably planar faces parallel to the direction of spring force, the faces being offset so that in a neutral position the outer edge of the closer spaced magnet set is aligned with the inner edge of the greater spaced magnet set. For use as a motor, a coil can be arranged with conductors orthogonal to both the magnet pole directions and the direction of desired spring force, located across from the magnets of one set and fixed with respect to the magnets of the other set. In a cylindrical coordinate system having axial spring force, the magnets are radially poled and motor coils are concentric with the cylinder axis.

PIA21258

NASA Image and Video Library

2016-12-20

These five images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter show different Martian features of progressively greater size and complexity, all thought to result from thawing of seasonal carbon-dioxide ice that covers large areas near Mars' south pole during winter. The sequence illustrates possible stages in development of a type of Martian terrain called "araneiform," from Latin for spider-shaped. They range from a depression with one trough (upper left) to a broad network of "spiders" (lower right). Each image has a scale bar in meters, from 20 meters (66 feet) in the upper-left image to 300 meters (984 feet) in the lower-right one. Each image also includes dark "fans" that result from the same thawing process. Carbon-dioxide ice, better known as "dry ice," does not occur naturally on Earth. On Mars, sheets of it cover the ground during winter in areas near both poles, including the south-polar regions with spidery terrain. The dark fans appear in these areas each spring. Spring sunshine penetrates the ice to warm the ground underneath, causing some carbon dioxide on the bottom of the sheet to thaw into gas. The trapped gas builds pressure until a crack forms in the ice sheet. Gas erupts out, and gas beneath the ice rushes toward the vent, picking up particles of sand and dust. This erodes the ground and also supplies the geyser with particles that fall back to the surface, downwind, and appear as the dark spring fans. These five images are excerpts from HiRISE observations PSP_002718_0950, taken Feb. 24, 2007, at 85 degrees south latitude, 82 degrees east longitude, and ESP_011842_0980, taken Feb. 4, 2009, at 81 degrees south latitude, 76 degrees east longitude. http://photojournal.jpl.nasa.gov/catalog/PIA21258

Export of Algal Communities from Land Fast Arctic Sea Ice Influenced by Overlying Snow Depth and Episodic Rain Events

NASA Astrophysics Data System (ADS)

Neuer, S.; Juhl, A. R.; Aumack, C.; McHugh, C.; Wolverton, M. A.; Kinzler, K.

2016-02-01

Sea ice algal communities dominate primary production of the coastal Arctic Ocean in spring. As the sea ice bloom terminates, algae are released from the ice into the underlying, nutrient-rich waters, potentially seeding blooms and feeding higher trophic levels in the water column and benthos. We studied the sea ice community including export events over four consecutive field seasons (2011-2014) during the spring ice algae bloom in land-fast ice near Barrow, Alaska, allowing us to investigate both seasonal and interannual differences. Within each year, we observed a delay in algal export from ice in areas covered by thicker snow compared to areas with thinner snow coverage. Variability in snow cover therefore resulted in a prolonged supply of organic matter to the underlying water column. Earlier export in 2012 was followed by a shift in the diatom community within the ice from pennates to centrics. During an unusual warm period in early May 2014, precipitation falling as rain substantially decreased the snow cover thickness (from snow depth > 20 cm down to 0-2 cm). After the early snowmelt, algae were rapidly lost from the sea ice, and a subsequent bloom of taxonomically-distinct, under-ice phytoplankton developed a few days later. The typical immured sea ice diatoms never recovered in terms of biomass, though pennate diatoms (predominantly Nitzschia frigida) did regrow to some extent near the ice bottom. Sinking rates of the under-ice phytoplankton were much more variable than those of ice algae particles, which would potentially impact residence time in the water column, and fluxes to the benthos. Thus, the early melt episode, triggered by rain, transitioned directly into the seasonal melt and the release of biomass from the ice, shifting production from sea ice to the water column, with as-of-yet unknown consequences for the springtime Arctic food web.

Numerical study on the aerodynamic characteristics of both static and flapping wing with attachments

NASA Astrophysics Data System (ADS)

Xie, Lingwang; Zhang, Xingwei; Luo, Pan; Huang, Panpan

2017-10-01

The purpose of this paper is to investigate the aerodynamic mechanism of airfoils under different icing situations which are different icing type, different icing time, and different icing position. Numerical simulation is carried out by using the finite volume method for both static and flapping airfoils, when Reynolds number is kept at 135000. The difference of aerodynamic performance between the airfoil with attachments and without attachments are be investigated by comparing the force coefficients, lift-to-drag ratios and flow field contour. The present simulations reveal that some influences of attachment are similar in the static airfoil and the flapping airfoil. Specifically, the airfoil with the attachment derived from glaze ice type causes the worse aerodynamic performance than that derived from rime ice type. The longer the icing time, the greater influence of aerodynamic performance the attachment causes. The attachments on the leading-edge have the greater influence of aerodynamic performance than other positions. Moreover, there are little differences between the static airfoil and the flapping airfoil. Compared with the static airfoil, the flapping airfoil which attachment located on the trailing edge causes a worse aerodynamic performance. Both attachments derived from rime ice type and glaze ice type all will deteriorate the aerodynamic performance of the asymmetrical airfoils. Present work provides the systematic and comprehensive study about icing blade which is conducive to the development of the wind power generation technology.

Effect of Ice Formations on Section Drag of Swept NACA 63A-009 Airfoil with Partial-Span Leading-Edge Slat for Various Modes of Thermal Ice Protection

NASA Technical Reports Server (NTRS)

VonGlahn, Uwe H.; Gray, Vernon H.

1954-01-01

The effects of primary and runback ice formations on the section drag of a 36 deg swept NACA 63A-009 airfoil section with a partial-span leading-edge slat were studied over a range of angles of attack from 2 to 8 deg and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.39 to 1.23 grams per cubic meter and datum air temperatures from 10 to 25 F. The results with slat retracted showed that glaze-ice formations caused large and rapid increases in section drag coefficient and that the rate of change in section drag coefficient for the swept 63A-009 airfoil was about 2-1 times that for an unswept 651-212 airfoil. Removal of the primary ice formations by cyclic de-icing caused the drag to return almost to the bare-airfoil drag value. A comprehensive study of the slat icing and de-icing characteristics was prevented by limitations of the heating system and wake interference caused by the slat tracks and hot-gas supply duct to the slat. In general, the studies showed that icing on a thin swept airfoil will result in more detrimental aerodynamic characteristics than on a thick unswept airfoil.

Observing the advection of sea ice in the Weddell Sea using buoy and satellite passive microwave data

NASA Technical Reports Server (NTRS)

Massom, Robert A.

1992-01-01

Data from four buoys tracked by Nimbus 6 and concurrent ice concentrations retrieved from Nimbus 7 scanning multichannel microwave radiometer data are used to investigate the progress and behavior of an area of sea ice as it drifts from the southwestern Weddell Sea. The overall drift characteristics and their relationship to ice edge displacement are examined within the framework of four zones. Three phases are identified in the large-scale behavior of the Weddell Sea ice cover, namely, a rapid equatorward and eastward advance, a quasi-equilibrium phase, and a period of rapid recession. Outbreaks of cold continental air alternate with incursions of relatively warm air from the north; warm conditions are recorded as far as 1200 km in from the ice edge in winter. Closed loops in the buoy trajectories, which are clockwise to the south of 63 deg S, reverse to become anticlockwise to the north. A coherence is observed in the response of the buoys to the passage of storms, even though the buoys separated by a distance of over 100 km.

Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition (N-ICE2015)

NASA Astrophysics Data System (ADS)

Kayser, Markus; Maturilli, Marion; Graham, Robert M.; Hudson, Stephen R.; Rinke, Annette; Cohen, Lana; Kim, Joo-Hong; Park, Sang-Jong; Moon, Woosok; Granskog, Mats A.

2017-10-01

The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively "clear" and "opaque" atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Ålesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Ålesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Ålesund generate great differences below. The long-term radiosonde record (1993-2014) from Ny-Ålesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1-3°C warmer than the climatology during winter.

Emerging trends in the sea state of the Beaufort and Chukchi seas

NASA Astrophysics Data System (ADS)

Thomson, Jim; Fan, Yalin; Stammerjohn, Sharon; Stopa, Justin; Rogers, W. Erick; Girard-Ardhuin, Fanny; Ardhuin, Fabrice; Shen, Hayley; Perrie, Will; Shen, Hui; Ackley, Steve; Babanin, Alex; Liu, Qingxiang; Guest, Peter; Maksym, Ted; Wadhams, Peter; Fairall, Chris; Persson, Ola; Doble, Martin; Graber, Hans; Lund, Bjoern; Squire, Vernon; Gemmrich, Johannes; Lehner, Susanne; Holt, Benjamin; Meylan, Mike; Brozena, John; Bidlot, Jean-Raymond

2016-09-01

The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.

Managing Annual Flood Risk and Reducing Socioeconomic Flood Impacts in Rural Arctic through Science-Community Collaborations

NASA Astrophysics Data System (ADS)

Kontar, Y. Y.

2016-12-01

Multiple Arctic riverine communities face flood risk every spring. Within hours floodwater and ice debris destroy entire communities, displacing hundreds of people. In FY 2015-2016 an international project entitled Reducing Spring Flood Impacts for Wellbeing of Communities of the North was successfully conducted with the goal to identify best practices in managing the risk and reducing the socioeconomic impacts of floods associated with spring river ice breakup. In this presentation, we will elaborate on socioeconomic impacts of breakup floods, including long-term evacuation of population, loss of means of livelihoods, and ecosystem resource loss. We will also compare and contrast spring flood risk management and reduction strategies and their effectiveness in Alaska and Sakha Republic (Siberia), Russia. The findings are based on surveys completed by the representatives of adverse populations in two flood-prone communities in Alaska and Sakha Republic, as well as a series of roundtable discussions and interviews between social and geoscientists, emergency managers, and community leaders.

Ice erosion of a sea-floor knickpoint at the inner edge of the stamukhi zone, Beaufort Sea, Alaska

USGS Publications Warehouse

Barnes, P.W.; Asbury, J.L.; Rearic, D.M.; Ross, C.R.

1987-01-01

In 1981 and 1982, detailed bathymetric and side-scan sonar surveys were made of an area of the sea floor north of Prudhoe Bay, Alaska, to study the changing characteristics of the seabed at the inner boundary of the stamukhi zone, the coast-parallel zone of grounded ice ridges that occurs in water depths between 15 and 50 m in the arctic. The fathograms and sonographs resolved 10-cm features and electronic navigation gave relocations accurate to about 10 m. Year after year an ice boundary develops at the inner edge of the stamukhi zone where major shear and pressure deformation occur in about the same location. Associated with this ice boundary, the bathymetry shows a pronounced break in slope - the knickpoint - on the shelf profile at about 20 m depth. The 2-3 m-high knickpoint is cut in a consolidated gravelly mud of pre-Holocene age. A well-defined gravel and cobble shoal a few meters high usually occurs at the inshore edge of the knickpoint. The sonograph mosaic shows that seaward of the knickpoint, ice gouges saturate the sea floor and are well defined; inshore the gouges are fewer in number and are poorly defined on the records. Few gouges can be traced from the seaward side of the knickpoint across the shoals to the inshore side of the knickpoint. Studies of ice gouging rates in two seabed corridors that cross the stamukhi zone reveal the highest rates of gouging seaward of the knickpoint. We believe that the knickpoint results from ice erosion at the inner boundary of the stamukhi zone. Intensified currents associated with this boundary winnow away fine sediments. Ice bulldozing and currents shape the shoals, which perch atop the knickpoint. The knickpoint helps to limit ice forces on the seabed inshore of the stamukhi zone. ?? 1987.

Pan-Arctic sea ice-algal chl a biomass and suitable habitat are largely underestimated for multiyear ice.

PubMed

Lange, Benjamin A; Flores, Hauke; Michel, Christine; Beckers, Justin F; Bublitz, Anne; Casey, John Alec; Castellani, Giulia; Hatam, Ido; Reppchen, Anke; Rudolph, Svenja A; Haas, Christian

2017-11-01

There is mounting evidence that multiyear ice (MYI) is a unique component of the Arctic Ocean and may play a more important ecological role than previously assumed. This study improves our understanding of the potential of MYI as a suitable habitat for sea ice algae on a pan-Arctic scale. We sampled sea ice cores from MYI and first-year sea ice (FYI) within the Lincoln Sea during four consecutive spring seasons. This included four MYI hummocks with a mean chl a biomass of 2.0 mg/m 2 , a value significantly higher than FYI and MYI refrozen ponds. Our results support the hypothesis that MYI hummocks can host substantial ice-algal biomass and represent a reliable ice-algal habitat due to the (quasi-) permanent low-snow surface of these features. We identified an ice-algal habitat threshold value for calculated light transmittance of 0.014%. Ice classes and coverage of suitable ice-algal habitat were determined from snow and ice surveys. These ice classes and associated coverage of suitable habitat were applied to pan-Arctic CryoSat-2 snow and ice thickness data products. This habitat classification accounted for the variability of the snow and ice properties and showed an areal coverage of suitable ice-algal habitat within the MYI-covered region of 0.54 million km 2 (8.5% of total ice area). This is 27 times greater than the areal coverage of 0.02 million km 2 (0.3% of total ice area) determined using the conventional block-model classification, which assigns single-parameter values to each grid cell and does not account for subgrid cell variability. This emphasizes the importance of accounting for variable snow and ice conditions in all sea ice studies. Furthermore, our results indicate the loss of MYI will also mean the loss of reliable ice-algal habitat during spring when food is sparse and many organisms depend on ice-algae. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Icing Management for Coast Guard Assets

DTIC Science & Technology

2013-04-01

Homola et al. (2006) summarized many ice detection concepts and assessed their near-term application potential to wind turbines . This re- port will...is attached, using adhe- sive, to the leading edge of an airfoil, aircraft or wind turbine , or any other surface that must be protected from icing...for ap- plication to wind turbines . ERDC/CRREL TR-13-7 287 Five optical ice detectors are currently mature technologies, but not all are

MDA Ice Detection and Measurement Camera Development and Validation for NASA-KSC (2004-2007)

DTIC Science & Technology

2007-08-17

various densities, ice formed on metals, and ice made from Atlantic Ocean salt water that may be more representative of ice formed in the salt air... clam squ den app det n). a. d b. h so that they enough to support the Kaman sensor head without crushing. Some th throughout this process is... clam s, may be considered compensated for by the extra ice that can form on the edge of the test el. In such a case where there is no ice extending

Action of a Local Time-Periodic Load on an Ice Sheet with a Crack

NASA Astrophysics Data System (ADS)

Tkacheva, L. A.

2017-11-01

The problem of vibrations of an ice sheet with a rectilinear crack on the surface of an ideal incompressible fluid of finite depth under the action of a time-periodic local load is solved analytically using the Wiener-Hopf technique. Ice cover is simulated by two thin elastic semi-infinite plates of constant thickness. The thickness of the plates may be different on the opposite sides of the crack. Various boundary conditions on the edges of the plates are considered. For the case of contact of plates of the same thickness, a solution in explicit form is obtained. The asymptotics of the deflection of the plates in the far field is studied. It is shown that in the case of contact of two plates of different thickness, predominant directions of wave propagation at an angle to the crack can be identified in the far field. In the case of contact of plates of the same thickness with free edges and with free overlap, an edge waveguide mode propagating along the crack is excited. It is shown that the edge mode propagates with maximum amplitude if the vertical wall is in contact with the plate. Examples of calculations are given.

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.

Cross Flow Effects on Glaze Ice Roughness Formation

NASA Technical Reports Server (NTRS)

Tsao, Jen-Ching

2004-01-01

The present study examines the impact of large-scale cross flow on the creation of ice roughness elements on the leading edge of a swept wing under glaze icing conditions. A three-dimensional triple-deck structure is developed to describe the local interaction of a 3 D air boundary layer with ice sheets and liquid films. A linear stability analysis is presented here. It is found that, as the sweep angle increases, the local icing instabilities enhance and the most linearly unstable modes are strictly three dimensional.

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

USGS Publications Warehouse

Belchansky, Gennady I.; Douglas, David C.

2002-01-01

The Special Sensor Microwave Imager (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 synthetic aperture radar (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 Sea, 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% (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 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 highly correlated during winter, spring, and fall, with mean differences of less than 8.1% (S.D.<15%) for the NASA Team algorithm, and less than 2.8% (S.D.<13.8%) for the Bootstrap algorithm. Respective differences between SSM/I NASA Team and SSM/I Bootstrap total concentrations were less than 5.3% (S.D.<6.9%). Monthly mean differences between SSM/I and OKEAN differed annually by less than 6%, with smaller differences primarily in winter. The NASA Team and Bootstrap algorithms underestimated the total sea ice concentrations relative to the RADARSAT ScanSAR no more than 3.0% (S.D.<9%) and 1.2% (S.D.<7.5%) during cold months, and no more than 12% and 7% during summer, respectively. ScanSAR tended to estimate higher ice concentrations for ice concentrations greater than 50%, when compared to SSM/I during all months. ScanSAR underestimated total sea ice concentration by 2% compared to the OKEAN-01 algorithm during cold months, and gave an overestimation by 2% during spring and summer months. Total NASA Team and Bootstrap sea ice concentration estimates derived from coincident SSM/I and OKEAN-01 data demonstrated mean differences of no more than 5.3% (S.D.<7%), 3.1% (S.D.<5.5%), 2.0% (S.D.<5.5%), and 7.3% (S.D.<10%) for fall, winter, spring, and summer periods, respectively. Large disagreements were observed between the OKEAN and NASA Team results in spring and summer for estimates of the first-year (FY) and multiyear (MY) age classes. The OKEAN-01 algorithm and data tended to estimate, on average, lower concentrations of young or FY ice and higher concentrations of total and MY ice for all months and seasons. Our results contribute to the growing body of documentation about the levels of disparity obtained when seasonal sea ice concentrations are estimated using various types of satellite data and algorithms.

Summer Drivers of Atmospheric Variability Affecting Ice Shelf Thinning in the Amundsen Sea Embayment, West Antarctica

NASA Astrophysics Data System (ADS)

Deb, Pranab; Orr, Andrew; Bromwich, David H.; Nicolas, Julien P.; Turner, John; Hosking, J. Scott

2018-05-01

Satellite data and a 35-year hindcast of the Amundsen Sea Embayment summer climate using the Weather Research and Forecasting model are used to understand how regional and large-scale atmospheric variability affects thinning of ice shelves in this sector of West Antarctica by melting from above and below (linked to intrusions of warm water caused by anomalous westerlies over the continental shelf edge). El Niño episodes are associated with an increase in surface melt but do not have a statistically significant impact on westerly winds over the continental shelf edge. The location of the Amundsen Sea Low and the polarity of the Southern Annular Mode (SAM) have negligible impact on surface melting, although a positive SAM and eastward shift of the Amundsen Sea Low cause anomalous westerlies over the continental shelf edge. The projected future increase in El Niño episodes and positive SAM could therefore increase the risk of disintegration of West Antarctic ice shelves.

Anatomy of a late spring snowfall on sea ice

NASA Astrophysics Data System (ADS)

Perovich, Donald; Polashenski, Christopher; Arntsen, Alexandra; Stwertka, Carolyn

2017-03-01

Spring melt initiation is a critical process for Arctic sea ice. Melting conditions decrease surface albedo at a time of high insolation, triggering powerful albedo feedback. Weather events during melt initiation, such as new snowfalls, can stop or reverse the albedo decline, however. Here we present field observations of such a snow event and demonstrate its enduring impact through summer. Snow fell 3-6 June 2014 in the Chukchi Sea, halting melt onset. The snow not only raised albedo but also provided a significant negative latent heat flux, averaging -51 W m-2 from 3 to 6 June. The snowfall delayed sustained melt by 11 days, creating cascading impacts on surface energy balance that totaled some 135 MJ/m2 by mid-August. The findings highlight the sensitivity of sea ice conditions on seasonal time scales to melt initiation processes.

The Sea-Ice Floe Size Distribution

NASA Astrophysics Data System (ADS)

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

2017-12-01

The size distribution of ice floes in the polar seas affects the dynamics and thermodynamics of the ice cover and its interaction with the ocean and atmosphere. Ice-ocean models are now beginning to include the floe size distribution (FSD) in their simulations. In order to characterize seasonal changes of the FSD and provide validation data for our ice-ocean model, we calculated the FSD in the Beaufort and Chukchi seas over two spring-summer-fall seasons (2013 and 2014) using more than 250 cloud-free visible-band scenes from the MODIS sensors on NASA's Terra and Aqua satellites, identifying nearly 250,000 ice floes between 2 and 30 km in diameter. We found that the FSD follows a power-law distribution at all locations, with a seasonally varying exponent that reflects floe break-up in spring, loss of smaller floes in summer, and the return of larger floes after fall freeze-up. We extended the results to floe sizes from 10 m to 2 km at selected time/space locations using more than 50 high-resolution radar and visible-band satellite images. Our analysis used more data and applied greater statistical rigor than any previous study of the FSD. The incorporation of the FSD into our ice-ocean model resulted in reduced sea-ice thickness, mainly in the marginal ice zone, which improved the simulation of sea-ice extent and yielded an earlier ice retreat. We also examined results from 17 previous studies of the FSD, most of which report power-law FSDs but with widely varying exponents. It is difficult to reconcile the range of results due to different study areas, seasons, and methods of analysis. We review the power-law representation of the FSD in these studies and discuss some mathematical details that are important to consider in any future analysis.

Low temperature and high field regimes of connected kagome artificial spin ice: the role of domain wall topology.

PubMed

Zeissler, Katharina; Chadha, Megha; Lovell, Edmund; Cohen, Lesley F; Branford, Will R

2016-07-22

Artificial spin ices are frustrated magnetic nanostructures where single domain nanobars act as macrosized spins. In connected kagome artificial spin ice arrays, reversal occurs along one-dimensional chains by propagation of ferromagnetic domain walls through Y-shaped vertices. Both the vertices and the walls are complex chiral objects with well-defined topological edge-charges. At room temperature, it is established that the topological edge-charges determine the exact switching reversal path taken. However, magnetic reversal at low temperatures has received much less attention and how these chiral objects interact at reduced temperature is unknown. In this study we use magnetic force microscopy to image the magnetic reversal process at low temperatures revealing the formation of quite remarkable high energy remanence states and a change in the dynamics of the reversal process. The implication is the breakdown of the artificial spin ice regime in these connected structures at low temperatures.

Topologically Nontrivial Magnon Bands in Artificial Square Spin Ices with Dzyaloshinskii-Moriya Interaction [Topologically Non-Trivial Magnon Bands in Artificial Square Spin Ices Subject to Dzyaloshinskii-Moriya Interaction

DOE PAGES

Iacocca, Ezio; Heinonen, Olle

2017-09-20

Systems that exhibit topologically protected edge states are interesting both from a fundamental point of view as well as for potential applications, the latter because of the absence of backscattering and robustness to perturbations. It is desirable to be able to control and manipulate such edge states. Here, we demonstrate using a semi-analytical model that artificial square ices can incorporate both features: an interfacial Dzyaloshinksii-Moriya gives rise to topologically non-trivial magnon bands, and the equilibrium state of the spin ice is reconfigurable with different states having different magnon dispersions and topology. Micromagnetic simulations are used to determine the magnetization equilibriummore » states and to validate the semi-analytical model. Lastly, our results are amenable to experimental verification via, e.g., lithographic patterning and micro-focused Brillouin light scattering.« less

Topologically Nontrivial Magnon Bands in Artificial Square Spin Ices with Dzyaloshinskii-Moriya Interaction [Topologically Non-Trivial Magnon Bands in Artificial Square Spin Ices Subject to Dzyaloshinskii-Moriya Interaction

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

Iacocca, Ezio; Heinonen, Olle

Systems that exhibit topologically protected edge states are interesting both from a fundamental point of view as well as for potential applications, the latter because of the absence of backscattering and robustness to perturbations. It is desirable to be able to control and manipulate such edge states. Here, we demonstrate using a semi-analytical model that artificial square ices can incorporate both features: an interfacial Dzyaloshinksii-Moriya gives rise to topologically non-trivial magnon bands, and the equilibrium state of the spin ice is reconfigurable with different states having different magnon dispersions and topology. Micromagnetic simulations are used to determine the magnetization equilibriummore » states and to validate the semi-analytical model. Lastly, our results are amenable to experimental verification via, e.g., lithographic patterning and micro-focused Brillouin light scattering.« less

Seasonality of vertical flux and sinking particle characteristics in an ice-free high arctic fjord-Different from subarctic fjords?

NASA Astrophysics Data System (ADS)

Wiedmann, Ingrid; Reigstad, Marit; Marquardt, Miriam; Vader, Anna; Gabrielsen, Tove M.

2016-02-01

The arctic Adventfjorden (78°N, 15°E, Svalbard) used to be seasonally ice-covered but has mostly been ice-free since 2007. We used this ice-free arctic fjord as a model area to investigate (1) how the vertical flux of biomass (chlorophyll a and particulate organic carbon, POC) follows the seasonality of suspended material, (2) how sinking particle characteristics change seasonally and affect the vertical flux, and (3) if the vertical flux in the ice-free arctic fjord with glacial runoff resembles the flux in subarctic ice-free fjords. During seven field investigations (December 2011-September 2012), suspended biomass was determined (5, 15, 25, and 60 m), and short-term sediment traps were deployed (20, 30, 40, and 60 m), partly modified with gel-filled jars to study the size and frequency distribution of sinking particles. During winter, resuspension from the seafloor resulted in large, detrital sinking particles. Intense sedimentation of fresh biomass occurred during the spring bloom. The highest POC flux was found during autumn (770-1530 mg POC m- 2 d- 1), associated with sediment-loaded glacial runoff and high pteropod abundances. The vertical biomass flux in the ice-free arctic Adventfjorden thus resembled that in subarctic fjords during winter and spring, but a higher POC sedimentation was observed during autumn.

Mars Global Surveyor Thermal Emission Spectrometer (TES) Observations of Dust Opacity During Aerobraking and Science Phasing

NASA Technical Reports Server (NTRS)

Smith, Michael D.; Pearl, John C.; Conrath, Barney J.; Christensen, Philip R.

1999-01-01

The Mars Global Surveyor (MGS) arrived at Mars in September 1997 near Mars southern spring equinox and has now provided monitoring of conditions in the Mars atmosphere for more than half a Mars year. The large majority of the spectra taken by the Thermal Emission Spectrometer (TES) are in a nadir geometry (downward looking mode) where Mars is observed through the atmosphere. Most of these contain the distinct spectral signature of atmospheric dust. For these nadir-geometry spectra we retrieve column-integrated infrared aerosol (dust) opacities. TES observations during the aerobraking and science-phasing portions of the MGS mission cover the seasonal range L(sub s)=184 deg - 28 deg. Excellent spatial coverage was obtained in the southern hemisphere. Northern hemisphere coverage is generally limited to narrow strips taken during the periapsis pass but is still very valuable. At the beginning of the mission the 9-(micron)meter dust opacity at midsouthern latitudes was low (0.15-0.25). As the season advanced through southern spring and into summer, TES observed several regional dust storms (including the Noachis dust storm of November 1997) where peak 9-(micron)meter dust opacities approached or exceeded unity, as well as numerous smaller local storms. Both large and small dust storms exhibited significant changes in both spatial coverage and intensity over a timescale of a day. Throughout southern spring and summer the region at the edge of the retreating southern seasonal polar ice cap was observed to be consistently more dusty than other latitudes.

How Gas Carves Channels

NASA Image and Video Library

2017-01-24

NASA Mars Reconnaissance Orbiter spies a layer of dry ice covering Mars south polar layer. In the spring, gas created from heating of the dry ice escapes through ruptures in the overlying seasonal ice, entraining material from the ground below. The gas erodes channels in the surface, generally exploiting weaker material. The ground likely started as polygonal patterned ground (common in water-ice-rich surfaces), and then escaping gas widened the channels. Fans of dark material are bits of the surface carried onto the top of the seasonal ice layer and deposited in a direction determined by local winds. http://photojournal.jpl.nasa.gov/catalog/PIA11706

Seasonal origins of air masses transported to Mount Wrangell, Alaska, and comparison with the past atmospheric dust and tritium variations in its ice core

NASA Astrophysics Data System (ADS)

Yasunari, T. J.; Shiraiwa, T.; Kanamori, S.; Fujii, Y.; Igarashi, M.; Yamazaki, K.; Benson, C. S.; Hondoh, T.

2006-12-01

The North Pacific region is subject to various climatic phenomena such as the Pacific Decadal Oscillation (PDO), the El Niño-Southern Oscillation (ENSO), and the Arctic Oscillation (AO), significantly affecting the ocean and the atmosphere. Additionally, material circulation is also very active in this region such as spring dust storms in the desert and arid regions of East Asia and forest fires in Siberia and Alaska. Understanding the complex connections among the climatic phenomena and the material circulation would help in attempts to predict future climate changes. For this subject, we drilled a 50-m ice core at the summit of Mount Wrangell, which is located near the coast of Alaska (62°162'170"162°171'N, 144°162'170"162;°171'W, and 4100-m). We analyzed dust particle number density, tritium concentration, and 171 171 171 171 170 162 171 D in the core. The ice core spanned the years from 1992 to 2002 and we finally divided the years into five parts (early-spring; late-spring; summer; fall; winter). Dust and tritium amounts varied annually and intra-annually. For further understanding of the factors on those variations, we should know the origins of the seasonal dust and tritium. Hence, we examined their origins by the calculation of everyday 10-days backward trajectory analysis from January 1992 to August 2002 with 3-D wind data of the European Center for Medium-Range Weather Forecast (ECMWF). In early spring, the air mass from East Asia increased and it also explained dust increases in springtime, although the air contribution in winter increased too. In late spring, the air mass from the stratosphere increased, and it also corresponded to the stratospheric tritium increase in the ice core. The air masses from Siberia and the North Pacific in the mid-latitude always significantly contributed to Mount Wrangell, although those maximum contributions were fall and summer, respectively. The air mass originating in the interior of Alaska and North America did not contribute to Mount Wrangell so much. Intra-annual data of ice core is important for the discussion of detailed-seasonal climate variations in the periods when there are no meteorological data. Our preliminary study suggests that we may be able to obtain an important perspective on seasonal climate change in the past by connecting meteorological analysis with ice core data.

Wave propagation in the marginal ice zone - Model predictions and comparisons with buoy and synthetic aperture radar data

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Holt, Benjamin; Vachon, Paris W.

1991-01-01

Ocean wave dispersion relation and viscous attenuation by a sea ice cover are studied for waves propagating into the marginal ice zone (MIZ). The Labrador ice margin experiment (LIMEX), conducted on the MIZ off the east coast of Newfoundland, Canada in March 1987, provided aircraft SAR imagery, ice property and wave buoy data. Wave energy attenuation rates are estimated from SAR data and the ice motion package data that were deployed at the ice edge and into the ice pack, and compared with a model. It is shown that the model data comparisons are quite good for the ice conditions observed during LIMEX 1987.

UpTempO Buoys for Understanding and Predictions

DTIC Science & Technology

2016-02-28

fall cooling, and interannually as sea ice retreats and the warming season lengthens. The effort was a contribution to the multi-investigator ONR...relationships between sea ice retreat and upper ocean warming. ACCOMPLISHED I. Buoy deployments and data: We worked with the Pacific Gyre (PG...have for the first time investigated the daily variation in ice edge retreat speed from a pan-arctic perspective. We have found that the pace of ice

Southeast Michigan Snow and Ice Management (SEMSIM) : final evaluation at end of winter season, year 2004

DOT National Transportation Integrated Search

2004-08-01

In the early spring of 1999, the Detroit Department of Public Works, the Road Commission of Macomb County, the Road Commission for Oakland County, and the Wayne County Department of Public Services formed the Southeast Michigan Snow and Ice Managemen...

Impact behavior of graphite-epoxy simulated fan blades

NASA Technical Reports Server (NTRS)

Cook, T. S.; Preston, J. L., Jr.

1977-01-01

The response of a graphite-epoxy material, Modmor II/PR-286, to foreign object impact was investigated by impacting spherical projectiles of three different materials - gelatin, ice, and steel - on simulated blade specimens. Visual and metallographic inspection revealed three damage mechanisms: penetration, leading edge bending failure, and stress wave delamination and cracking. The steel projectiles caused penetration damage regardless of the impact location and angle. For the ice and gelatin particles impacting the leading edge, failure was due to large local bending strains, resulting in significant material removal and delamination damage.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, Craig; Rainville, Luc; Perry, Mary Jane

2016-04-01

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. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice 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 ice 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 ice extent, and evolution over the summer to the start of freeze up.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, C.; Rainville, L.; Perry, M. J.

2016-02-01

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. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice 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 kg m-3, just above the PSW, consistently thickens near the ice 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 ice extent, and evolution over the summer to the start of freeze up.

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.

Vigorous convection as the explanation for Pluto's polygonal terrain.

PubMed

Trowbridge, A J; Melosh, H J; Steckloff, J K; Freed, A M

2016-06-02

Pluto's surface is surprisingly young and geologically active. One of its youngest terrains is the near-equatorial region informally named Sputnik Planum, which is a topographic basin filled by nitrogen (N2) ice mixed with minor amounts of CH4 and CO ices. Nearly the entire surface of the region is divided into irregular polygons about 20-30 kilometres in diameter, whose centres rise tens of metres above their sides. The edges of this region exhibit bulk flow features without polygons. Both thermal contraction and convection have been proposed to explain this terrain, but polygons formed from thermal contraction (analogous to ice-wedges or mud-crack networks) of N2 are inconsistent with the observations on Pluto of non-brittle deformation within the N2-ice sheet. Here we report a parameterized convection model to compute the Rayleigh number of the N2 ice and show that it is vigorously convecting, making Rayleigh-Bénard convection the most likely explanation for these polygons. The diameter of Sputnik Planum's polygons and the dimensions of the 'floating mountains' (the hills of of water ice along the edges of the polygons) suggest that its N2 ice is about ten kilometres thick. The estimated convection velocity of 1.5 centimetres a year indicates a surface age of only around a million years.

LANDSAT survey of near-shore ice conditions along the Arctic coast of Alaska

NASA Technical Reports Server (NTRS)

Stringer, W. J. (Principal Investigator); Barrett, S. A.

1978-01-01

The author has identified the following significant results. Winter and spring near-shore ice conditions were analyzed for the Beaufort Sea 1973-77, and the Chukchi Sea 1973-76. LANDSAT imagery was utilized to map major ice features related to regional ice morphology. Significant features from individual LANDSAT image maps were combined to yield regional maps of major ice ridge systems for each year of study and maps of flaw lead systems for representative seasons during each year. These regional maps were, in turn, used to prepare seasonal ice morphology maps. These maps showed, in terms of a zonal analysis, regions of statistically uniform ice behavior. The behavioral characteristics of each zone were described in terms of coastal processes and bathymetric configuration.

Future Interannual Variability of Arctic Sea Ice Area and its Implications for Marine Navigation

NASA Astrophysics Data System (ADS)

Vavrus, S. J.; Mioduszewski, J.; Holland, M. M.; Wang, M.; Landrum, L.

2016-12-01

As both a symbol and driver of ongoing climate change, the diminishing Arctic sea ice pack has been widely studied in a variety of contexts. Most research, however, has focused on time-mean changes in sea ice, rather than on short-term variations that also have important physical and societal consequences. In this study we test the hypothesis that interannual Arctic sea ice variability will increase in the future by utilizing a set of 40 independent simulations from the Community Earth System Model's Large Ensemble for the 1920-2100 period. The model projects that ice variability will indeed grow substantially in all months but with a strong seasonal dependence in magnitude and timing. The variability increases most during late autumn (November-December) and least during spring. This increase proceeds in a time-transgressive manner over the course of the year, peaking soonest (2020s) in late-summer months and latest (2090s) during late spring. The variability in every month is inversely correlated with the average melt rate, resulting in an eventual decline in both terms as the ice pack becomes seasonal by late century. These projected changes in sea ice variations will likely have significant consequences for marine navigation, which we assess with the empirical Ice Numeral (IN) metric. A function of ice concentration and thickness, the IN quantifies the difficulty in traversing a transect of sea ice-covered ocean as a function of vessel strength. Our results show that although increasingly open Arctic seas will mean generally more favorable conditions for navigation, the concurrent rise in the variability of ice cover poses a competing risk. In particular, future intervals featuring the most rapid declines in ice area that coincide with the highest interannual ice variations will offer more inviting shipping opportunities tempered by less predictable navigational conditions.

Sea-ice indicators of polar bear habitat

NASA Astrophysics Data System (ADS)

Stern, Harry L.; Laidre, Kristin L.

2016-09-01

Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology - the cycle of biological events - is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979-2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from -3 to -9 days decade-1 in spring and from +3 to +9 days decade-1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days) and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of -7 to -19 days decade-1, with larger trends in the Barents Sea and central Arctic Basin. The June-October sea-ice concentration is declining in all regions at rates ranging from -1 to -9 percent decade-1. These sea-ice metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.

Towards an Ice-Free Arctic Ocean in Summertime

NASA Astrophysics Data System (ADS)

Gascard, Jean Claude

2014-05-01

Dividing the Arctic Ocean in two parts, the so-called Atlantic versus the Pacific sector, two distinct modes of variability appear for characterizing the Arctic sea-ice extent from 70°N up to 80°N in both sectors. The Atlantic sector seasonal sea-ice extent is characterized by a longer time scale than the Pacific sector with a break up melting season starting in May and reaching a peak in June-July, one month earlier than the Pacific sector of the Arctic Ocean revealing a faster time evolution and a larger spatial amplitude than the Atlantic sector. During recent years like 2007, sea-ice extent with sea-ice concentration above 15% retreated from 4 millions km2 to about 1 million km2 in the Arctic Pacific sector between 70° and 80°N except for 2012 when most of sea-ice melted away in this region. That explained most of the differences between the two extreme years 2007 and 2012. In the Atlantic sector, Arctic sea-ice retreated from 2 millions km2 to nearly 0 during recent years including 2007 and 2012. The Atlantic inflow North of Svalbard and Franz Josef Land is more likely responsible for a northward retreat of the ice edge in that region. The important factor is not only that the Arctic summer sea-ice minimum extent decreased by 3 or 4 millions km2 over the past 10 years but also that the melting period was steadily increasing by one to two days every year during that period. An important factor concerns the strength of the freezing that can be quantified in terms of Freezing Degree Days FDD accumulated during the winter-spring season and the strength of the melting (MDD) that can be accumulated during the summer season. FDD and MDD have been calculated for the past 30 years all over the Arctic Ocean using ERA Interim Reanalysis surface temperature at 2m height in the atmosphere. It is clear that FDD decreased significantly by more than 2000 FDD between 1980 and 2012 which is equivalent to the sensible heat flux corresponding to more than a meter of sea-ice thickness. During the same period MDD increased steadily mainly due to an increase of the melting period rather than an increase in summer temperatures. Due to uncertainties in sea-ice thickness distribution, an estimated 66% up to 75% of sea-ice mass or volume melted away during recent summers compare to previous 20 or 30 years. How long would it take to melt away the 1/4 or 1/3 of Arctic sea-ice left in summer? A root mean square extrapolation based on the last 10 years summer sea-ice minimum extent would lead to an ice-free Arctic Ocean by 2035.

Ice Floe Breaking in Contemporary Third Generation Operational Wave Models

NASA Astrophysics Data System (ADS)

Sévigny, C.; Baudry, J.; Gauthier, J. C.; Dumont, D.

2016-02-01

The dynamical zone observed at the edge of the consolidated ice area where are found the wave-fractured floes (i.e. marginal ice zone or MIZ) has become an important topic in ocean modeling. As both operational and climate ocean models now seek to reproduce the complex atmosphere-ice-ocean system with realistic coupling processes, many theoretical and numerical studies have focused on understanding and modeling this zone. Few attempts have been made to embed wave-ice interactions specific to the MIZ within a two-dimensional model, giving the possibility to calculate both the attenuation of surface waves by sea ice and the concomitant breaking of the sea ice-cover into smaller floes. One of the first challenges consists in improving the parameterization of wave-ice dynamics in contemporary third generation operational wave models. A simple waves-in-ice model (WIM) similar to the one proposed by Williams et al. (2013a,b) was implemented in WAVEWATCH III. This WIM considers ice floes as floating elastic plates and predicts the dimensionless attenuation coefficient by the use of a lookup-table-based, wave scattering scheme. As in Dumont et al. (2011), the different frequencies are treated individually and floe breaking occurs for a particular frequency when the expected wave amplitude exceeds the allowed strain amplitude, which considers ice floes properties and wavelength in ice field. The model is here further refined and tested in idealized two-dimensional cases, giving preliminary results of the performance and sensitivity of the parameterization to initial wave and ice conditions. The effects of the wave-ice coupling over the incident wave spectrum are analyzed as well as the resulting floe size distribution. The model gives prognostic values of the lateral extent of the marginal ice zone with maximum ice floe diameter that progressively increases with distance from the ice edge.

Contrasting population trends of piscivorous seabirds in the Pribilof Islands: A 30-year perspective

USGS Publications Warehouse

Byrd, G.V.; Schmutz, J.A.; Renner, H.M.

2008-01-01

The Pribilof Islands provide nesting habitat for one of the largest concentrations of piscivorous seabirds in the North Pacific region. Pribilof breeding populations of black-legged and red-legged kittiwakes (Rissa tridactyla and Rissa brevirostris), and common and thick-billed murres (Uria aalge and Uria lomvia) are supported by a highly productive marine food web. Productivity and temperature in this area are influenced by winter sea ice that frequently reaches its maximum extent near the Pribilofs. Although St. George and St. Paul islands, the two largest of the Pribilof group, are situated only 60 km apart, St. George is within 25 km of the shelf break, but St. Paul is approximately 90 km away. In contrast, the local contribution of sea ice-edge productivity in the spring is frequently closer to St. Paul than to St. George. Central place foraging piscivorous seabirds nesting at St. Paul and St. George are likely differentially affected by the relative contributions of the shelf break and ice-edge environments based on juxtaposition. Within the past decade or so, sea ice in the Bering Sea has failed to reach the vicinity of the Pribilofs in some years, and predictions of warming in the future suggest the possibility that direct effects of the ice on the immediate Pribilof environment will be reduced. To evaluate the response of kittiwakes and murres on the two islands to conditions in their foraging environments, we examined population trends over the past 30 years based on data from the seabird monitoring program conducted by the Alaska Maritime National Wildlife Refuge and others. Spatial differences in trends have been more consistent than differences among species, with populations at St. Paul having more enduring declines than those at St. George. At St. George, black-legged kittiwakes and common murres have remained stable. Red-legged kittiwakes and thick-billed murres both declined, but began to rebound in the late 1980s, such that in 2005 population numbers for all four species at St. George were approximately equivalent to those observed in 1976. In contrast, at St. Paul Island, all four species have declined for most of this 30-year time series, with only black-legged kittiwakes showing increases in the past decade but still remaining far below 1976 numbers. Interestingly, rates of productivity for kittiwakes and for murres were similar between the two islands, suggesting similar responses to summer conditions and implicating differential mortality of post-fledging juveniles or adults from the two islands (i.e., if summer food stress was insufficient to cause differences in productivity, but sufficient to cause physiological consequences that reduced survival. Another possibility is immigration from St. Paul to St. George, probably by juveniles. ?? 2008 Elsevier Ltd.

Fixture aids soldering of electronic components on circuit board

NASA Technical Reports Server (NTRS)

Ross, M. H.

1966-01-01

Spring clamp fixture holds small electronic components in a desired position while they are being soldered on a circuit board. The spring clamp is clipped on the edge of the circuit board and an adjustable spring-steel boom holds components against the board. The felt pad at the end of the boom is replaced with different attachments for other holding tasks.

Discrimination of first year sea ice thickness classes from a quad-Pol SAR image.

NASA Astrophysics Data System (ADS)

Hudier, E. J. J.

2016-12-01

Several methods have been developed to relate the average scattering represented by a T3 matrix into a dominant physical mechanism. These decomposition theorems rewrite the coherency matrix as the sum of physical components. Data extracted through these methods can then be used to classify ice areas according to a similarity in the statistics regarding those components. As the ice sheet is still thin enough to rupture under compressive forces, wind and current drag forces erect ridges at the periphery of un-deformed ice plates while opening up leads in which a an ice cover quickly develops. Freeze up under colder temperatures cause the ice to retain more salt in its upper layers therefore altering radar scattering compared to older ice areas. The statistics presented in the result section were computed implementing an eigenvalue/eigenvector decomposition method coupled with a whishart classifier on RadarSat II images of a late spring sea ice. It first shows a good resolution of the different ice environments characterized as a) linear ridges, b) rubble fields, c) old un-deformed ice and, d) young (thus thinner) un-deformed ice. The alpha angle parameter is coherent with a dominant surface scattering mechanism all over the scene which is consistent with a late spring sea ice and leads us to anticipate a classification mostly linked to surface roughness and ice surface orientation (in ridges). It is thus interesting to note than un-deformed ice areas result in two separate classes. We observe that areas of ice formed later during the winter season are well identified and their limits clearly delineated. Whereas, other ice areas display a certain diversity in term of scattering mechanisms, this type of ice turned out to be an almost perfect forward scatterer. While the main factor allowing to separate this type of ice from the rest of the sea ice may be the salt content of the surface layer, it gives an indirect way to discriminate sea ice areas of different thicknesses. Within areas of older ice, it worth noticing that continuous pressure ridges are resolved essentially as broken lines. Ridge extraction resulting mostly from the occurrence that one or several ice blocks within a target be oriented in a way that may cause single and double bounce scattering, odds remain high that such an occurrence do not happen.

Spider Web Pattern

NASA Technical Reports Server (NTRS)

2006-01-01

A delicate pattern, like that of a spider web, appears on top of the Mars residual polar cap, after the seasonal carbon-dioxide ice slab has disappeared. Next spring, these will likely mark the sites of vents when the carbon-dioxide ice cap returns. This Mars Global Surveyor, Mars Orbiter Camera image is about 3-kilometers wide (2-miles).

4. Porch Framing Details, Porch Railing and Floor Edge, Newel ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. Porch Framing Details, Porch Railing and Floor Edge, Newel Post and Handrail at Ramp - National Home for Disabled Volunteer Soldiers - Battle Mountain Sanitarium, Ward 4, 500 North Fifth Street, Hot Springs, Fall River County, SD

Sea ice and oceanic processes on the Ross Sea continental shelf

NASA Technical Reports Server (NTRS)

Jacobs, S. S.; Comiso, J. C.

1989-01-01

The spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf have been investigated in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86 percent during winter with little month-to-month of interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn.

The importance of tidewater glaciers for marine mammals and seabirds in Svalbard, Norway

NASA Astrophysics Data System (ADS)

Lydersen, Christian; Assmy, Philipp; Falk-Petersen, Stig; Kohler, Jack; Kovacs, Kit M.; Reigstad, Marit; Steen, Harald; Strøm, Hallvard; Sundfjord, Arild; Varpe, Øystein; Walczowski, Waldek; Weslawski, Jan Marcin; Zajaczkowski, Marek

2014-01-01

Approximately 60% of Svalbard's land areas are glaciated at the present time. The Archipelago has more than 1100 glaciers (> 1 km2) and 163 of these are “tidewater glaciers” - that is glaciers that terminate (with their calving front) at the sea. It has been known for a long time that these glacier front areas are important feeding areas for seabirds and marine mammals. Herein, we review current knowledge regarding the importance of these areas for these animals and reflect upon the processes that create these apparent “hotspots”. Kittiwakes Rissa tridactyla, routinely dominate avian assemblages in front of glaciers in Svalbard, but fulmars Fulmarus glacialis, ivory gulls Pagophila eburnea and glaucous gulls Larus hyperboreus also contribute to aggregations, which can sometimes comprise many thousands of individuals. The birds are often found in the so-called “brown zone”, which is an area in front of tidewater glaciers that is ice-free due to currents and muddy due to suspended sediments. Animals at these sites typically have their stomachs full of large zooplankton or fish. These brown zones are also foraging hotspots for Svalbard's ringed seals (Pusa hispida) and white whales (Delphinapterus leucas). Prime breeding habitat for ringed seals in Svalbard occurs deep in the fjords where ice pieces calved from the glacier fronts become frozen into land-fast sea-ice, promoting the accumulation of snow to a depth suitable for ringed seal females to dig out birth lairs above breathing holes in the ice. These pupping areas are important hunting areas for polar bears (Ursus maritimus) in spring, especially female bears with cubs of the year during the period following emergence from the winter/birthing den. Glacier-ice pieces floating in coastal areas are also important for all seal species in the region as dry platforms during moulting and also as general resting platforms for both birds and seals. During the last decade there have been several years with a complete lack of spring sea ice in many of the fjords along the west coast of Spitsbergen. During the spring periods in these years, bearded seals (Erignathus barbatus) have replaced their regular sea-ice platform with glacier ice, using it as a solid substrate for both birthing and nursing as well as general resting. The mechanisms that create foraging hotspots at the fronts of tidewater glaciers are related to the massive subsurface plumes of freshwater discharged from the glacier fronts. As these plumes rise towards the surface they entrain large volumes of ambient water, tens to hundreds of times the original discharge volume. This water is drawn from all depth levels as the plume ascends. This entrainment ensures a continuous resupply of intermediate depth waters from the outer parts of the fjords towards the glacier front and greatly amplifies the general estuarine circulation. The intermediate water masses carry plankton from a broad area, including the outer fjord, into the glacier front area, where they get entrained in the plume rising towards the surface, and often become stunned or die from freshwater osmotic shock. These small animals fall as an easy prey to the surface feeding predators. Large, strong swimming marine zooplankton species can sometimes escape by swimming below the inflow of marine water. But, they then become concentrated in a water layer near the bottom, making them of interest and susceptible to predators. The intermediate water masses also bring nutrients towards the glacier fronts where they are transported up to the surface layer where they can subsequently be utilized for post-bloom primary production. However, this tends to have greatest influence some distance away from the glacier front, when much of the outflow sediment has settled out. Currently, the mass balance for Svalbard glaciers is negative and climate change predictions for the future suggest continued warming, and hence continued glacial retreat. This will result in a reduction in both the number of glaciers calving into the ocean in Svalbard and the total length of calving fronts around the Archipelago. Similar to the retraction of the northern sea-ice edge (which is another diminishing foraging hotspot for these same arctic vertebrates), the climate-warming-induced changes in glaciers will likely lead to substantial distributional shifts and abundance reductions for many arctic species.

Sea ice ecosystems.

PubMed

Arrigo, Kevin R

2014-01-01

Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

Autumn leaf subsidies influence spring dynamics of freshwater plankton communities.

PubMed

Fey, Samuel B; Mertens, Andrew N; Cottingham, Kathryn L

2015-07-01

While ecologists primarily focus on the immediate impact of ecological subsidies, understanding the importance of ecological subsidies requires quantifying the long-term temporal dynamics of subsidies on recipient ecosystems. Deciduous leaf litter transferred from terrestrial to aquatic ecosystems exerts both immediate and lasting effects on stream food webs. Recently, deciduous leaf additions have also been shown to be important subsidies for planktonic food webs in ponds during autumn; however, the inter-seasonal effects of autumn leaf subsidies on planktonic food webs have not been studied. We hypothesized that autumn leaf drop will affect the spring dynamics of freshwater pond food webs by altering the availability of resources, water transparency, and the metabolic state of ponds. We created leaf-added and no-leaf-added field mesocosms in autumn 2012, allowed mesocosms to ice-over for the winter, and began sampling the physical, chemical, and biological properties of mesocosms immediately following ice-off in spring 2013. At ice-off, leaf additions reduced dissolved oxygen, elevated total phosphorus concentrations and dissolved materials, and did not alter temperature or total nitrogen. These initial abiotic effects contributed to higher bacterial densities and lower chlorophyll concentrations, but by the end of spring, the abiotic environment, chlorophyll and bacterial densities converged. By contrast, zooplankton densities diverged between treatments during the spring, with leaf additions stimulating copepods but inhibiting cladocerans. We hypothesized that these differences between zooplankton orders resulted from resource shifts following leaf additions. These results suggest that leaf subsidies can alter both the short- and long-term dynamics of planktonic food webs, and highlight the importance of fully understanding how ecological subsidies are integrated into recipient food webs.

Biogeochemical probing of microbial communities in a basalt-hosted hot spring at Kverkfjöll volcano, Iceland.

PubMed

Cousins, Claire R; Fogel, Marilyn; Bowden, Roxane; Crawford, Ian; Boyce, Adrian; Cockell, Charles; Gunn, Matthew

2018-06-01

We investigated bacterial and archaeal communities along an ice-fed surficial hot spring at Kverkfjöll volcano-a partially ice-covered basaltic volcano at Vatnajökull glacier, Iceland, using biomolecular (16S rRNA, apsA, mcrA, amoA, nifH genes) and stable isotope techniques. The hot spring environment is characterized by high temperatures and low dissolved oxygen concentrations at the source (68°C and <1 mg/L (±0.1%)) changing to lower temperatures and higher dissolved oxygen downstream (34.7°C and 5.9 mg/L), with sulfate the dominant anion (225 mg/L at the source). Sediments are comprised of detrital basalt, low-temperature alteration phases and pyrite, with <0.4 wt. % total organic carbon (TOC). 16S rRNA gene profiles reveal that organisms affiliated with Hydrogenobaculum (54%-87% bacterial population) and Thermoproteales (35%-63% archaeal population) dominate the micro-oxic hot spring source, while sulfur-oxidizing archaea (Sulfolobales, 57%-82%), and putative sulfur-oxidizing and heterotrophic bacterial groups dominate oxic downstream environments. The δ 13 C org (‰ V-PDB) values for sediment TOC and microbial biomass range from -9.4‰ at the spring's source decreasing to -12.6‰ downstream. A reverse effect isotope fractionation of ~3‰ between sediment sulfide (δ 34 S ~0‰) and dissolved water sulfate (δ 34 S +3.2‰), and δ 18 O values of ~ -5.3‰ suggest pyrite forms abiogenically from volcanic sulfide, followed by abiogenic and microbial oxidation. These environments represent an unexplored surficial geothermal environment analogous to transient volcanogenic habitats during putative "snowball Earth" scenarios and volcano-ice geothermal environments on Mars. © 2018 John Wiley & Sons Ltd.

Climatic effects on ice-jam flooding of the Peace-Athabasca Delta

NASA Astrophysics Data System (ADS)

Beltaos, S.; Prowse, T.; Bonsal, B.; Mackay, R.; Romolo, L.; Pietroniro, A.; Toth, B.

2006-12-01

The Peace-Athabasca Delta (PAD) in northern Alberta is one of the world's largest inland freshwater deltas, home to large populations of waterfowl, muskrat, beaver, and free-ranging wood bison. In recent decades, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the PAD region. Building on previous work that has identified the salient hydro-climatic factors, the frequency of ice-jam floods is considered under present (1961-1990) and future (2070-2099) climatic conditions. The latter are determined using temperature and precipitation output from the Canadian Climate Centre's second-generation Global Climate Model (CGCM2) for two different greenhouse-gas/sulphate emission scenarios. The analysis indicates that the ice season is likely to be reduced by 2-4 weeks, while future ice covers would be slightly thinner than they are at present. More importantly, a large part of the Peace River basin is expected to experience frequent and sustained mid-winter thaws, leading to significant melt and depleted snowpacks in the spring. Using an empirical relationship between ice-jam flood occurrence and size of the spring snowpack, a severe reduction in the frequency of ice-jam flooding is predicted under both future-climate scenarios that were considered. In turn, this trend is likely to accelerate the loss of aquatic habitat in the PAD region. Implications for potential mitigation and adaptation strategies are discussed. Copyright

The First Results of Monitoring the Formation and Destruction of the Ice Cover in Winter 2014-2015 on Ilmen Lake according to the Measurements of Dual-Frequency Precipitation Radar

NASA Astrophysics Data System (ADS)

Karaev, V. Yu.; Panfilova, M. A.; Titchenko, Yu. A.; Meshkov, E. M.; Balandina, G. N.; Andreeva, Z. V.

2017-12-01

The launch of the Dual-frequency Precipitation Radar (DPR) opens up new opportunities for studying and monitoring the land and inland waters. It is the first time radar with a swath (±65°) covering regions with cold climate where waters are covered with ice and land with snow for prolonged periods of time has been used. It is also the first time that the remote sensing is carried out at small incidence angles (less than 19°) at two frequencies (13.6 and 35.5 GHz). The high spatial resolution (4-5 km) significantly increases the number of objects that can be studied using the new radar. Ilmen Lake is chosen as the first test object for the development of complex programs for processing and analyzing data obtained by the DPR. The problem of diagnostics of ice-cover formation and destruction according to DPR data has been considered. It is shown that the dependence of the radar backscatter cross section on the incidence angle for autumn ice is different from that of spring ice, and can be used for classification. A comparison with scattering on the water surface has shown that, at incidence angles exceeding 10°, it is possible to discern all three types of reflecting surfaces: open water, autumn ice, and spring ice, under the condition of making repeated measurements to avoid possible ambiguity caused by wind.

Sub-daily sea ice motion and deformation from RADARSAT observations

NASA Technical Reports Server (NTRS)

Kwok, R.; Cunningham, G. F.

2003-01-01

We find a persistent level of oscillatory sea ice motion and deformation, superimposed on the large-scale wind-driven field, in May 2002 (spring) and February 2003 (mid-winter), in the high Arctic over a region centered at approx.(85degreeN, 135degreeW). At this latitude, the RADARSAT wide-swath SAR coverage provides 4??equential observations every day, for ice motion retrieval, with a sampling interval at the orbital period of approx. 101 minutes.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

USGS Publications Warehouse

Rode, Karyn D.; Wilson, Ryan R.; Douglas, David C.; Muhlenbruch, Vanessa L; Atwood, Todd C.; Regehr, Eric V.; Richardson, Evan; Pilfold, Nicholas; Derocher, Andrew E.; Durner, George M.; Stirling, Ian; Amstrup, Steven C.; St Martin, Michelle; Pagano, Anthony M.; Simac, Kristin

2018-01-01

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983–1999 and 2000–2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity.

PubMed

Rode, Karyn D; Wilson, Ryan R; Douglas, David C; Muhlenbruch, Vanessa; Atwood, Todd C; Regehr, Eric V; Richardson, Evan S; Pilfold, Nicholas W; Derocher, Andrew E; Durner, George M; Stirling, Ian; Amstrup, Steven C; St Martin, Michelle; Pagano, Anthony M; Simac, Kristin

2018-01-01

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Dynamics, rate and nature of retreat of the British Irish Ice-Sheet offshore of NW Ireland following the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Weilbach, K.; O'Cofaigh, C.; Lloyd, J. M.; Benetti, S.; Dunlop, P.

2016-12-01

Recent studies of the British and Irish Ice Sheet (BIIS) have identified evidence of ice extending to the continental shelf edge along the western margin of the ice sheet off NW Ireland. While this advance is assumed to have occurred during the LGM, exact timing of maximum advance, and the timing and nature of the subsequent retreat is not well constrained. The location of the north-western sector of the BIIS adjacent to the North Atlantic makes this area ideal to study the ice sheet dynamics of a major marine terminating ice sheet, and the rate and nature of its retreat following the LGM. High resolution swath bathymetry and sub-bottom profiler (SBP) data along with sedimentological, micropalaeontological and geochronological investigations of sediment cores, collected across the NW Irish shelf, have been used to establish the extent, timing and nature of retreat of this sector of the BIIS. Swath bathymetry show glacial landforms on the shelf, and SBP-data along with twenty seven vibro-cores were collected in east-west oriented transects across a series of arcuate recessional moraines stretching from the shelf edge to Donegal Bay. These moraines record progressive still stands of a lobate ice margin during its retreat from the shelf edge, and are therefore ideal for the investigation of ice-sheet dynamics and chronology during retreat. Twenty two radiocarbon dates from foraminifera and macrofossils, sampled from the sediment cores, indicate that maximum ice sheet extent occurred around 26200 y cal BP, with an initial rapid retreat across the shelf. Visual logging, X-ray imagery, MSCL data and palaeoenvironmental analyses of the sediment cores, indicate that retreat happened in a glacimarine environment, and was punctuated by multiple stillstands and possible readvances across the mid and inner shelf, forming the arcuate moraines. The radiocarbon dates suggest that final retreat occurred after 17857 y. cal BP, which is consistent with onshore cosmogenic exposure ages from NW Ireland, showing de-glaciation around 17400 y cal BP.

Meteorological conditions in a thinner Arctic sea ice regime from winter to summer during the Norwegian Young Sea Ice expedition (N-ICE2015)

NASA Astrophysics Data System (ADS)

Cohen, Lana; Hudson, Stephen R.; Walden, Von P.; Graham, Robert M.; Granskog, Mats A.

2017-07-01

Atmospheric measurements were made over Arctic sea ice north of Svalbard from winter to early summer (January-June) 2015 during the Norwegian Young Sea Ice (N-ICE2015) expedition. These measurements, which are available publicly, represent a comprehensive meteorological data set covering the seasonal transition in the Arctic Basin over the new, thinner sea ice regime. Winter was characterized by a succession of storms that produced short-lived (less than 48 h) temperature increases of 20 to 30 K at the surface. These storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering North Atlantic storms into the high Arctic. Nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling ("radiatively clear state"). The strength and depth of these inversions were similar to those during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. In contrast, atmospheric profiles during the "opaquely cloudy state" were different to those from SHEBA due to differences in the synoptic conditions and location within the ice pack. Storm events observed during spring/summer were the result of synoptic systems located in the Barents Sea and the Arctic Basin rather than passing directly over N-ICE2015. These synoptic systems were driven by a large-scale circulation pattern typical of recent years, with an Arctic Dipole pattern developing during June. Surface temperatures became near-constant 0°C on 1 June marking the beginning of summer. Atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes.

Early Student Support to Investigate the Role of Sea Ice Albedo Feedback in Sea Ice Predictions

DTIC Science & Technology

2015-09-30

time periods: 1925-1960, 1970-2005, 2015-2050, and 2060 -2095. Model runs from the first two time periods had historical radiative forcing, whereas the...of the Arctic exhibits the relationship seen near the sea ice edge in the late 20th century. • Between 2015-2050 and 2060 -2095, there is a regime...1980). Ice-free summers are not found until 2060s . • From the linear regressions, air temperatures decrease in importance over time as good

Proving and Improving Wave Models in the Arctic Ocean and its MIZ

DTIC Science & Technology

2014-09-30

on a giant ice island in Baffin Bay, in which the response to a breakup event was measured and the size of the broken-out iceberg fragment tested...2014), In situ measurements and analysis of ocean waves in the Antarctic marginal ice zone, Geophys. Res. Lett., 41, 5046–5051, doi:10.1002...Symposium on Ice, Singapore, August 11 to 15, 2014. Doble, M. J., and J.-R. Bidlot, 2013. Wave buoy measurements at the Antarctic sea ice edge

Deuterium enrichment of polycyclic aromatic hydrocarbons by photochemically induced exchange with deuterium-rich cosmic ices

NASA Technical Reports Server (NTRS)

Sandford, S. A.; Bernstein, M. P.; Allamandola, L. J.; Gillette, J. S.; Zare, R. N.

2000-01-01

The polycyclic aromatic hydrocarbon (PAH) coronene (C24H12) frozen in D2O ice in a ratio of less than 1 part in 500 rapidly exchanges its hydrogen atoms with the deuterium in the ice at interstellar temperatures and pressures when exposed to ultraviolet radiation. Exchange occurs via three different chemical processes: D atom addition, D atom exchange at oxidized edge sites, and D atom exchange at aromatic edge sites. Observed exchange rates for coronene (C24H12)-D2O and d12-coronene (C24D12)-H2O isotopic substitution experiments show that PAHs in interstellar ices could easily attain the D/H levels observed in meteorites. These results may have important consequences for the abundance of deuterium observed in aromatic materials in the interstellar medium and in meteorites. These exchange mechanisms produce deuteration in characteristic molecular locations on the PAHs that may distinguish them from previously postulated processes for D enrichment of PAHs.

Wind Tunnel Measured Effects on a Twin-Engine Short-Haul Transport Caused by Simulated Ice Accretions

NASA Technical Reports Server (NTRS)

Reehorst, Andrew; Potapczuk, Mark; Ratvasky, Thomas; Laflin, Brenda Gile

1996-01-01

A series of wind tunnel tests were conducted to assess the effects of leading edge ice contamination upon the performance of a short-haul transport. The wind tunnel test was conducted in the NASA Langley 14 by 22 foot facility. The test article was a 1/8 scale twin-engine short-haul jet transport model. Two separate leading edge ice contamination configurations were tested in addition to the uncontaminated baseline configuration. Several aircraft configurations were examined including various flap and slat deflections, with and without landing gear. Data gathered included force measurements via an internal six-component force balance, pressure measurements through 700 electronically scanned wing pressure ports, and wing surface flow visualization measurements. The artificial ice contamination caused significant performance degradation and caused visible changes demonstrated by the flow visualization. The data presented here is just a portion of the data gathered. A more complete data report is planned for publication as a NASA Technical Memorandum and data supplement.

X-Ray Absorption Spectra of Amorphous Ices from GW Quasiparticle Calculation

NASA Astrophysics Data System (ADS)

Kong, Lingzhu; Car, Roberto

2013-03-01

We use a GW approach[2] to compute the x-ray absorption spectra of model low- and high-density amorphous ice structures(LDA and HDA)[3]. We include the structural effects of quantum zero point motion using colored-noise Langevin molecular dynamics[4]. The calculated spectra differences in the main and post edge region between LDA and HDA agree well with experimental observations. We attribute these differences to the presence of interstitial molecules within the first coordination shell range in HDA. This assignment is further supported by a calculation of the spectrum of ice VIII, a high-pressure structure that maximizes the number of interstitial molecules and, accordingly, shows a much weaker post-edge feature. We further rationalize the spectral similarity between HDA and liquid water, and between LDA and ice Ih in terms of the respective similarities in the H-bond network topology and bond angle distributions. Supported by grants DOE-DE-SC0005180, DOE DE-SC0008626 and NSF-CHE-0956500.

Ice Water Classification Using Statistical Distribution Based Conditional Random Fields in RADARSAT-2 Dual Polarization Imagery

NASA Astrophysics Data System (ADS)

Zhang, Y.; Li, F.; Zhang, S.; Hao, W.; Zhu, T.; Yuan, L.; Xiao, F.

2017-09-01

In this paper, Statistical Distribution based Conditional Random Fields (STA-CRF) algorithm is exploited for improving marginal ice-water classification. Pixel level ice concentration is presented as the comparison of methods based on CRF. Furthermore, in order to explore the effective statistical distribution model to be integrated into STA-CRF, five statistical distribution models are investigated. The STA-CRF methods are tested on 2 scenes around Prydz Bay and Adélie Depression, where contain a variety of ice types during melt season. Experimental results indicate that the proposed method can resolve sea ice edge well in Marginal Ice Zone (MIZ) and show a robust distinction of ice and water.

Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats

NASA Astrophysics Data System (ADS)

Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.

2017-12-01

The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from autonomous profilers provide insight into the hydrographic state of the Ross Sea at the start of the spring period of sea-ice breakup, and how ocean mixing and sea ice interact to initiate the summer open-water season.

Late Summer Frazil Ice-Associated Algal Blooms around Antarctica

NASA Astrophysics Data System (ADS)

DeJong, Hans B.; Dunbar, Robert B.; Lyons, Evan A.

2018-01-01

Antarctic continental shelf waters are the most biologically productive in the Southern Ocean. Although satellite-derived algorithms report peak productivity during the austral spring/early summer, recent studies provide evidence for substantial late summer productivity that is associated with green colored frazil ice. Here we analyze daily Moderate Resolution Imaging Spectroradiometer satellite images for February and March from 2003 to 2017 to identify green colored frazil ice hot spots. Green frazil ice is concentrated in 11 of the 13 major sea ice production polynyas, with the greenest frazil ice in the Terra Nova Bay and Cape Darnley polynyas. While there is substantial interannual variability, green frazil ice is present over greater than 300,000 km2 during March. Late summer frazil ice-associated algal productivity may be a major phenomenon around Antarctica that is not considered in regional carbon and ecosystem models.

Results of low power deicer tests on a swept inlet component in the NASA Lewis icing research tunnel

NASA Technical Reports Server (NTRS)

Bond, Thomas H.; Shin, Jaiwon

1993-01-01

Tests were conducted under a USAF/NASA Low Power Deicer program on two expulsive technologies to examine system performance on hardware representative of a modern aircraft part. The BF Goodrich Electro-Expulsive Deicing System and Pneumatic Impulse Ice Protection System were installed on a swept, compound curve, engine inlet component with varying leading edge radius, and tested through a range of icing and system operating conditions in the NASA Lewis Icing Research Tunnel. A description of the experimental procedure and results, including residual ice thickness, shed ice particle size, and changes in system energy/pressure characteristics are presented.

Results of Low Power Deicer tests on a swept inlet component in the NASA Lewis Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Bond, Thomas H.; Shin, Jaiwon

1993-01-01

Tests were conducted under a USAF/NASA Low Power Deicer program on two expulsive technologies to examine system performance on hardware representative of a modern aircraft part. The BF Goodrich Electro-Expulsive Deicing System and Pneumatic Impulse Ice Protection system were installed on a swept, compound curve, engine inlet component with varying leading edge radius, and tested through a range of icing and system operating conditions in the NASA Lewis Icing Research Tunnel. A description of the experimental procedure and results, including residual ice thickness, shed ice particle size, and changes in system energy/pressure characteristics are presented.

Aircraft and satellite passive microwave observations of the Bering Sea ice cover during MIZEX West

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Gloersen, P.; Wilheit, T. T., Jr.

1986-01-01

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 ice types.

Sea Ice, Climate and Fram Strait

NASA Technical Reports Server (NTRS)

Hunkins, K.

1984-01-01

When sea ice is formed the albedo of the ocean surface increases from its open water value of about 0.1 to a value as high as 0.8. This albedo change effects the radiation balance and thus has the potential to alter climate. Sea ice also partially seals off the ocean from the atmosphere, reducing the exchange of gases such as carbon dioxide. This is another possible mechanism by which climate might be affected. The Marginal Ice Zone Experiment (MIZEX 83 to 84) is an international, multidisciplinary study of processes controlling the edge of the ice pack in that area including the interactions between sea, air and ice.

Ice from the Solar System Edge Artist Concept

NASA Image and Video Library

2012-09-18

Researchers are brewing up icy, organic concoctions in the lab to mimic materials at the edge of our solar system and beyond. The lab is shown at right, and a very young solar system, with its swirling planet-forming disk is at left.

Arctic melt ponds and bifurcations in the climate system

NASA Astrophysics Data System (ADS)

Sudakov, I.; Vakulenko, S. A.; Golden, K. M.

2015-05-01

Understanding how sea ice melts is critical to climate projections. In the Arctic, melt ponds that develop on the surface of sea ice floes during the late spring and summer largely determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a bifurcation point - an irreversible critical threshold as the system warms, by incorporating geometric information about melt pond evolution. This study is based on a bifurcation analysis of the energy balance climate model with ice-albedo feedback as the key mechanism driving the system to bifurcation points.

ASPECTS OF ARCTIC SEA ICE OBSERVABLE BY SEQUENTIAL PASSIVE MICROWAVE OBSERVATIONS FROM THE NIMBUS-5 SATELLITE.

USGS Publications Warehouse

Campbell, William J.; Gloersen, Per; Zwally, H. Jay; ,

1984-01-01

Observations made from 1972 to 1976 with the Electrically Scanning Microwave Radiometer on board the Nimbus-5 satellite provide sequential synoptic information of the Arctic sea ice cover. This four-year data set was used to construct a fairly continuous series of three-day average 19-GHz passive microwave images which has become a valuable source of polar information, yielding many anticipated and unanticipated discoveries of the sea ice canopy observed in its entirety through the clouds and during the polar night. Short-term, seasonal, and annual variations of key sea ice parameters, such as ice edge position, ice types, mixtures of ice types, ice concentrations, and snow melt on the ice, are presented for various parts of the Arctic.

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

NASA Astrophysics Data System (ADS)

sugihara, K.; Nakatsugawa, M.

2013-12-01

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

Geomorphological analysis of boulders and polygons on Martian periglacial patterned ground terrains

NASA Astrophysics Data System (ADS)

Orloff, Travis C.

Images from the High Resolution Imaging Science Experiment Camera onboard the Mars Reconnaisance Orbiter show the surface in higher detail than previously capable. I look at a landscape on Mars called permafrost patterned ground which covers ˜10 million square kilometers of the surface at high latitudes (>50°). Using the new high resolution images available we objectively characterize permafrost patterned ground terrains as an alternative to observational surveys which while detailed suffer from subjective bias. I take two dimensional Fourier transforms of individual images of Martian permafrost patterned ground to find the scale most representative of the terrain. This scale acts as a proxy for the size of the polygons themselves. Then I look at the distribution of spectral scales in the northern hemisphere between 50-70° and find correlations to previous studies and with the extent of ground ice in the surface. The high resolution images also show boulders clustering with respect to the underlying pattern. I make the first detailed observations of these clustered boulders and use crater counting to place constraints on the time it takes for boulders to cluster. Finally, I present a potential mechanism for the process that clusters the boulders that takes the specifics of the Martian environment to account. Boulders lying on the surface get trapped in seasonal CO2 frost while ice in the near surface contracts in the winter. The CO2 frost sublimates in spring/summer allowing the boulders to move when the near surface ice expands in summer. Repeated iterations lead to boulders that cluster in the polygon edges. Using a thermal model of the subsurface with Mars conditions and an elastic model of a polygon I show boulders could move as much as ˜0.1mm per year in the present day.

Concentration gradients and growth/decay characteristics of the seasonal sea ice cover

NASA Technical Reports Server (NTRS)

Comiso, J. C.; Zwally, H. J.

1984-01-01

The characteristics of sea ice cover in both hemispheres are analyzed and compared. The areal sea ice cover in the entire polar regions and in various geographical sectors is quantified for various concentration intervals and is analyzed in a consistent manner. Radial profiles of brightness temperatures from the poles across the marginal zone are also evaluated at different transects along regular longitudinal intervals during different times of the year. These radial profiles provide statistical information about the ice concentration gradients and the rates at which the ice edge advances or retreats during a complete annual cycle.

Weddell-Scotia sea marginal ice zone observations from space, October 1984

NASA Technical Reports Server (NTRS)

Carsey, F. D.; Holt, B.; Martin, S.; Rothrock, D. A.; Mcnutt, L.

1986-01-01

Imagery from the Shuttle imaging radar-B experiment as well as other satellite and meteorological data are examined to learn more about the open sea ice margin of the Weddell-Scotia Seas region. At the ice edge, the ice forms into bandlike aggregates of small ice floes similar to those observed in the Bering Sea. The radar backscatter characteristics of these bands suggest that their upper surface is wet. Further into the pack, the radar imagery shows a transition to large floes. In the open sea, large icebergs and long surface gravity waves are discernable in the radar images.

Supraglacial sulfur springs and associated biological activity in the Canadian high arctic - signs of life beneath the ice

USGS Publications Warehouse

Grasby, Stephen E.; Allen, Carlton C.; Longazo, Teresa G.; Lisle, John T.; Griffin, Dale W.; Beauchamp, Benoit

2003-01-01

Unique springs, discharging from the surface of an arctic glacier, release H2S and deposit native sulfur, gypsum, and calcite. The presence of sulfur in three oxidation states indicates a complex series of redox reactions. Physical and chemical conditions of the spring water and surrounding environment, as well as mineralogical and isotopic signatures, suggest biologically mediated reactions. Cell counts and DNA analyses confirm bacteria are present in the spring system, and a limited number of sequenced isolates suggests that complex communities of bacteria live within the glacial system.

Vigorous convection as the explanation for Pluto’s polygonal terrain

NASA Astrophysics Data System (ADS)

Trowbridge, A. J.; Melosh, H. J.; Steckloff, J. K.; Freed, A. M.

2016-06-01

Pluto’s surface is surprisingly young and geologically active. One of its youngest terrains is the near-equatorial region informally named Sputnik Planum, which is a topographic basin filled by nitrogen (N2) ice mixed with minor amounts of CH4 and CO ices. Nearly the entire surface of the region is divided into irregular polygons about 20-30 kilometres in diameter, whose centres rise tens of metres above their sides. The edges of this region exhibit bulk flow features without polygons. Both thermal contraction and convection have been proposed to explain this terrain, but polygons formed from thermal contraction (analogous to ice-wedges or mud-crack networks) of N2 are inconsistent with the observations on Pluto of non-brittle deformation within the N2-ice sheet. Here we report a parameterized convection model to compute the Rayleigh number of the N2 ice and show that it is vigorously convecting, making Rayleigh-Bénard convection the most likely explanation for these polygons. The diameter of Sputnik Planum’s polygons and the dimensions of the ‘floating mountains’ (the hills of of water ice along the edges of the polygons) suggest that its N2 ice is about ten kilometres thick. The estimated convection velocity of 1.5 centimetres a year indicates a surface age of only around a million years.

Development of a model for the ice scraping process.

DOT National Transportation Integrated Search

1996-10-01

A laboratory study has been conducted with two aims in mind. The first goal was : to develop a description of how a cutting edge scrapes ice from the road surface. The : second goal was to investigate the extent, if any, to which serrated blades were...

Insights into the effects of patchy ice layers on water balance heterogeneity in peatlands

NASA Astrophysics Data System (ADS)

Dixon, Simon; Kettridge, Nicholas; Devito, Kevin; Petrone, Rich; Mendoza, Carl; Waddington, Mike

2017-04-01

Peatlands in boreal and sub-arctic settings are characterised by a high degree of seasonality. During winter soils are frozen and snow covers the surface preventing peat moss growth. Conversely, in summer, soils unfreeze and rain and evapotranspiration drive moss productivity. Although advances have been made in understanding growing season water balance and moss dynamics in northern peatlands, there remains a gap in knowledge of inter-seasonal water balance as layers of ice break up during the spring thaw. Understanding the effects of ice layers on spring water balance is important as this coincides with periods of high wildfire risk, such as the devastating Fort McMurrary wildfire of May, 2016. We hypothesise that shallow layers of ice disconnect the growing surface of moss from a falling water table, and prevent water from being supplied from depth. A disconnect between the evaporating surface and deeper water storage will lead to the drying out of the surface layer of moss and a greater risk of severe spring wildfires. We utilise the unsaturated flow model Hydrus 2D to explore water balance in peat layers with an impermeable layer representing ice. Additionally we create models to represent the heterogeneous break up of ice layers observed in Canadian boreal peatlands; these models explore the ability of breaks in an ice layer to connect the evaporating surface to a deeper water table. Results show that peatlands with slower rates of moss growth respond to dry periods by limiting evapotranspiration and thus maintain moist conditions in the sub-surface and a water table above the ice layer. Peatlands which are more productive continue to grow moss and evaporate during dry periods; this results in the near surface mosses drying out and the water table dropping below the level of the ice. Where there are breaks in the ice layer the evaporating surface is able to maintain contact with a falling water table, but connectivity is limited to above the breaks, with limited lateral transfer of water above the ice. Conceptually this means that peatlands which tend to have lower rates of growth are largely unaffected by the presence of a shallow ice layer in the early growing season, and are able to maintain moist sub-surface conditions in the absence of precipitation. They will thus be more resistant to severe wildfire. Conversely, peatlands which tend towards higher levels of moss productivity are able to maintain moss growth during dry periods. In the presence of an ice layer this greater productivity leads to a disconnection from deep water sources, extensive drying out of moss above the ice, and a greater susceptibility to severe wildfires. Our study gives important insights into the mechanisms behind heterogeneity in burning and depth of burn in northern peatland wildfires, as well as into burn heterogeneity within peatland microtopography.

Wide, Branching Channels

NASA Image and Video Library

2017-01-11

Southern spring on Mars brings sublimation of the seasonal dry ice polar cap. Gas trapped under the seasonal ice sheet carves channels on its way to escaping to the atmosphere. At this site, the channels are wider than we see elsewhere on Mars, perhaps meaning that the spider-like (or more scientifically, "araneiform") terrain here is older, or that the surface is more easily eroded. Seasonal fans of eroded surface material, pointed in two different directions, are deposited on the remaining ice. http://photojournal.jpl.nasa.gov/catalog/PIA13151

A Preliminary Study of the Prevention of Ice on Aircraft by the Use of Engine-exhaust Heat

NASA Technical Reports Server (NTRS)

Rodert, Lewis A

1939-01-01

An investigation was made in the N.A.C.A. ice tunnel at air temperatures from 20 degrees to 28 degrees Fahrenheit and at a velocity of 80 miles per hour to determine whether ice formations on a model wing could be prevented by the use of the heat from the engine-exhaust gas. Various spanwise duct systems were tested in a 6-foot-chord N.A.C.A. 23012 wing model. The formation of ice over the entire wing chord was prevented by the direct heating of the forward 10 percent of the wing by hot air, which was passed through leading-edge ducts. Under dry conditions, enough heat to maintain the temperature of the forward 10 percent of the wing at about 200 degrees Fahrenheit above that of the ambient air was required for the prevention of ice formation. The air temperature in the ducts that was necessary to produce these skin temperatures varied from 360 degrees to 834 degrees Fahrenheit; the corresponding air velocities in the duct were 152 and 45 feet per second. Ice formations at the leading edge were locally prevented by air that passed over the interior of the wing surface at a velocity of 30 feet per second and a temperature of 122 degrees Fahrenheit.

Lake Stability and Winter-Spring Transitions: Decoupled Ice Duration and Winter Stratification

NASA Astrophysics Data System (ADS)

Daly, J.; Dana, S.; Neal, B.

2016-12-01

Ice-out is an important historical record demonstrating the impact of warmer air temperatures on lake ice. To better understand regional differences in ice-out trends, to characterize the thermal dynamics of smaller mountain lakes, and to develop baseline data for Maine's high elevations landscapes, sub-hourly water temperatures have been collected in over a dozen of Maine's mountain lakes since 2010. Both surface water and hypolimnion temperature data are recorded year-round, facilitating the determination of ice-in, ice-out, and the duration of winter stratification. The multi-year record from sites across as 250 km transect allows us to compare spatial variability related to lake morphometry and location with inter-annual variability related to local weather. All of the study lakes are large enough to stratify during the summer and mix extensively during the fall. Most years, our data show that the onset of winter stratification is nearly synchronous across the study area and is associated with cold air temperatures. Winter stratification can begin days to weeks before ice-in; the timing of ice-in shows more variability, with both elevation and basin aspect influencing the timing. Ice-out shows both the anticipated spatial and interannual variability; some years there is strong coherence between locations while other years show high variability, possibly a function of differences in snowpack. Ice-out is not always immediately followed by the end of winter stratification, there is sometimes a lag of days to weeks before the lakes mix. If the warm temperatures that lead to ice-out are followed by calm days without significant wind, the surface of some lakes begins to warm quickly maintaining the density difference and prolonging winter stratification. The longer the lag time, the stronger the density difference becomes which may also result in a very brief period of mixing in the spring prior to set-up of summer stratification. This year's El Niño event resulted in very late ice-in, leading to an unusually short ice duration period at most sites. However, ice-out for these sites was within the range observed previous years and there may not be a significant impact on summer water temperatures.

Growth and condition of juvenile chum and pink salmon in the northeastern Bering Sea

NASA Astrophysics Data System (ADS)

Wechter, Melissa E.; Beckman, Brian R.; Andrews, Alexander G., III; Beaudreau, Anne H.; McPhee, Megan V.

2017-01-01

As the Arctic continues to warm, abundances of juvenile Pacific salmon (Oncorhynchus spp.) in the northern Bering Sea are expected to increase. However, information regarding the growth and condition of juvenile salmon in these waters is limited. The first objective of this study was to describe relationships between size, growth, and condition of juvenile chum (O. keta) and pink (O. gorbuscha) salmon and environmental conditions using data collected in the northeastern Bering Sea (NEBS) from 2003-2007 and 2009-2012. Salmon collected at stations with greater bottom depths and cooler sea-surface temperature (SST) were longer, reflecting their movement further offshore out of the warmer Alaska Coastal Water mass, as the season progressed. Energy density, after accounting for fish length, followed similar relationships with SST and bottom depth while greater condition (weight-length residuals) was associated with warm SST and shallower stations. We used insulin-like growth factor-1 (IGF-1) concentrations as an indicator of relative growth rate for fishes sampled in 2009-2012 and that found fish exhibited higher IGF-1 concentrations in 2010-2012 than in 2009, although these differences were not clearly attributable to environmental conditions. Our second objective was to compare size and condition of juvenile chum and pink salmon in the NEBS between warm and cool spring thermal regimes of the southeastern Bering Sea (SEBS). This comparison was based on a hypothesis informed by the strong role of sea-ice retreat in the spring for production dynamics in the SEBS and prevailing northward currents, suggesting that feeding conditions in the NEBS may be influenced by production in the SEBS. We found greater length (both species) and condition (pink salmon) in years with warm thermal regimes; however, both of these responses changed more rapidly with day of year in years with cool springs. Finally, we compared indicators of energy allocation between even and odd brood-year stocks of juvenile pink salmon, finding support for the idea that the even-year stock allocates more energy to storage, as opposed to growth, than does the odd-year stock. Over all, our results support the idea that sea-ice dynamics influence energy allocation and growth of juvenile salmon in the northern Bering Sea and provide a foundation for further understanding of how environmental conditions influence juvenile salmon at the northern edge of their range.

Using high-resolution HiRISE digital elevation models to study early activity in polar regions

NASA Astrophysics Data System (ADS)

Portyankina, G.; Pommerol, A.; Aye, K.; Thomas, N.; Mattson, S.; Hansen, C. J.

2013-12-01

Martian polar areas are known for their very dynamic seasonal activity. It is believed that many observed seasonal phenomena here (cold CO2 jets, seasonal ice cracks, fan deposits, blotches) are produced by spring sublimation of CO2 slab ice. The Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) has exceptional capabilities to image polar areas at times when surface processes there are most active, i.e. in early local spring. HiRISE data can be also used to create digital elevation models (DEMs) of the martian surface if two images with similar lighting but different observation geometry are available. Polar areas pose some specific problems in this because of the oblique illumination conditions and seasonally changing ice cover. Nevertheless, HiRISE DEMs with spatial resolution up to 1 meter were produced for a few polar locations with active spring sublimation. These DEMs improve our ability to directly compare observations from different local times, sols, seasons and martian years. These observations may now be orthorectified by projecting them onto the well-defined topography thus eliminating the ambiguities of different observational geometries. In addition, the DEM can serve as a link between the observations and models of seasonal activity. Observations of martian polar areas in springs of multiple martian years have led to the hypothesis that meter-scale topography is triggering the activity in early spring. Solar energy input is critical for the timing of spring activity. In this context, variations of surface inclination are important especially in early spring, when orientation towards the sun is one of critical parameters determining the level of solar energy input, the amount of CO2 sublimation, and hence the level of any activity connected to it. In the present study existing DEMs of two polar locations serve as model terrains to test the previously proposed hypothesis of early initialization of CO2 activity by solar illumination. We use the NAIF SPICE system to calculate precise energy input to each surface facet accounting for their slope and aspect orientation and shadowing by neighbor terrains. We show that the energy distribution over the surface is highly heterogeneous and maximized on the sides of the channels and other small topographical features. Our study supports the hypothesis that solar energy input in polar areas in spring is directly related to the activity observed.

The Effects of Changing Sea Ice on Marine Mammals and Their Hunters in Northern Alaska

NASA Astrophysics Data System (ADS)

Huntington, H.; Quakenbush, L.; Nelson, M.

2015-12-01

Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information and insight relevant to ecological understanding, conservation action, and the regulation of human activity. We interviewed hunters in villages from northern Bering Sea to the Beaufort Sea, focusing on bowhead whales, walrus, and ice seals. Hunters reported extensive changes in sea ice, with resulting effects on the timing of marine mammal migrations, the distribution and behavior of the animals, and the efficacy of certain hunting methods, for example the difficulty of finding ice thick enough to support a bowhead whale for butchering. At the same time, hunters acknowledged impacts and potential impacts from changing technology such as more powerful outboard engines and from industrial activity such as shipping and oil and gas development. Hunters have been able to adapt to some changes, for example by hunting bowhead whales in fall as well as spring on St. Lawrence Island, or by focusing their hunt in a shorter period in Nuiqsut to accommodate work schedules and worse weather. Other changes, such as reduced availability of ice seals due to rapid retreat of pack ice after spring break-up, continue to defy easy responses. Continued environmental changes, increased disturbance from human activity, and the introduction of new regulations for hunting may further challenge the ability of hunters to provide food as they have done to date, though innovation and flexibility may also provide new sources of adaptation.

Seasonal variability in ice-front position, glacier speed, and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016

NASA Astrophysics Data System (ADS)

Kehrl, L. M.; Joughin, I. R.; Shean, D. E.

2016-12-01

Marine-terminating glaciers can be very sensitive to changes in ice-front position, depending on their geometry. If a nearly grounded glacier retreats into deeper water, the glacier typically must speed up to produce the additional longitudinal and lateral stress gradients necessary to restore force balance. This speedup often causes thinning, which can increase the glacier's susceptibility to further retreat. In this study, we combine satellite observations and numerical modeling (Elmer/Ice) to investigate how seasonal changes in ice-front position affect glacier speed and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016. Helheim's calving front position fluctuated about a mean position from 2010-2016. During 2010/11, 2013/14, and 2015/16, Helheim seasonally retreated and advanced along a reverse bed slope by > 3 km. During these years, the glacier retreated from winter/spring to late summer and then readvanced until winter/spring. During the retreat, Helheim sped up by 20-30% and thinned by 20 m near its calving front. This thinning caused the calving front to unground, and a floating ice tongue was then able to readvance over the following winter with limited iceberg calving. The advance, which continued until the glacier reached the top of the bathymetric high, caused the glacier to slow and thicken. During years when Helheim likely did not form a floating ice tongue, iceberg calving continued throughout the winter. Consequently, the formation of this floating ice tongue may have helped stabilize Helheim after periods of rapid retreat and dynamic thinning. Helheim's rapid retreat from 2001-2005 also ended when a floating ice tongue formed and readvanced over the 2005/06 winter. These seasonal retreat/advance cycles may therefore be important for understanding Helheim's long-term behavior.

Variation in annual production of copepods, euphausiids, and juvenile walleye pollock in the southeastern Bering Sea

NASA Astrophysics Data System (ADS)

Sigler, Michael F.; Napp, Jeffrey M.; Stabeno, Phyllis J.; Heintz, Ronald A.; Lomas, Michael W.; Hunt, George L.

2016-12-01

We synthesize recent research on variation in annual production of copepods (Calanus spp.), euphausiids (Thysanoessa spp.), and juvenile walleye pollock (Gadus chalcogrammus) in the southeastern Bering Sea. We reach five conclusions: 1) the timing of the spring bloom is more important than the amount of annual primary production for the transfer of primary to secondary production (i.e., timing matters); 2) summer and fall, not just spring, matter: organisms must maximize energy intake devoted to somatic growth and storage of lipids and minimize energy expenditures during each season; 3) stored lipids are important for the overwinter survival of both zooplankton and age-0 walleye pollock; 4) variation in ice extent and timing of ice retreat affect the spatial distributions of phytoplankton, zooplankton, and age-0 walleye pollock; when these spatial distributions match in late-ice-retreat years, the annual production of copepods, euphausiids, and juvenile walleye pollock often increases (i.e., location matters); 5) if years with late ice retreat, which favor copepod, euphausiid, and juvenile walleye pollock production, occur in succession, top-down control increases. These conclusions help to explain annual variation in production of copepods, euphausiids and juvenile walleye pollock. Copepods and euphausiids often are more abundant in cold years with late ice retreat than in warm years with early ice retreat due to bloom timing and the availability of ice algae during years with late ice retreat. As a consequence, age-0 walleye pollock consume lipid-enriched prey in cold years, better preparing them for their first winter and their overwinter survival is greater. In addition, there is a spatial match of primary production, zooplankton, and age-0 walleye pollock in cold years and a mismatch in warm years.

Trends in the Sea Ice Cover Using Enhanced and Compatible AMSR-E, SSM/I and SMMR Data

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Nishio, Fumihiko

2007-01-01

Arguably, the most remarkable manifestation of change in the polar regions is the rapid decline (of about -10 %/decade) in the Arctic perennial ice cover. Changes in the global sea ice cover, however, are more modest, being slightly positive in the Southern Hemisphere and slightly negative in the Northern Hemisphere, the significance of which has not been adequately assessed because of unknown errors in the satellite historical data. We take advantage of the recent and more accurate AMSR-E data to evaluate the true seasonal and interannual variability of the sea ice cover, assess the accuracy of historical data, and determine the real trend. Consistently derived ice concentrations from AMSR-E, SSM/I, and SMMR data were analyzed and a slight bias is observed between AMSR-E and SSM/I data mainly because of differences in resolution. Analysis of the combine SMMR, SSM/I and AMSR-E data set, with the bias corrected, shows that the trends in extent and area of sea ice in the Arctic region is -3.4 +/- 0.2 and -4.0 +/- 0.2 % per decade, respectively, while the corresponding values for the Antarctic region is 0.9 +/- 0.2 and 1.7 .+/- 0.3 % per decade. The higher resolution of the AMSR-E provides an improved determination of the location of the ice edge while the SSM/I data show an ice edge about 6 to 12 km further away from the ice pack. Although the current record of AMSR-E is less than 5 years, the data can be utilized in combination with historical data for more accurate determination of the variability and trends in the ice cover.

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.

Tidewater terminus tug-of-war

NASA Astrophysics Data System (ADS)

Bartholomaus, T. C.; Larsen, C. F.; O'Neel, S.; West, M. E.

2012-12-01

When a glacier terminus recedes, not only does the glacier lose the ice between the former and present terminus, but the terminal reach of the glacier can steepen, causing ice flow out of the glacier interior increases. The increased flow will continue, thinning the glacier, until the glacier geometry and ice flow reach a new equilibrium. Yahtse Glacier is an advancing tidewater glacier on the Gulf of Alaska coast. To better understand the controls on its terminus position, we use a suite of seismic, geodetic and oceanographic data. Both calving and submarine melt contribute to frontal ablation, however, at Yahtse Glacier the ice is too fractured to support undercutting below the water line, nor does a persistent submarine toe develop. Thus the terminus retreats as fast as subaerial calving occurs. Previous work at Yahtse Glacier demonstrated that locally recorded seismic events between 1 and 5 Hz are predominantly the result of subaerial iceberg calving. Therefore, we use seismicity as a proxy for the frontal ablation rate. We measure the near-terminus glacier velocity with oblique photogrammetry, calibrated with ~10 day intervals of surveyed ice velocity. These methods reveal an annually-averaged terminus velocity of 6.9 km/yr. The frontal ablation rate and the terminus ice velocity are nearly in phase and reach maximum values twice per year: in the spring and fall. Integrating the difference between frontal ablation rate and terminus ice velocity reveals a pattern of terminus positions with a single annual cycle, quite similar to that which we observe in the field. GPS measurements 10 km from the terminus indicate that ice velocities peak in May and decrease through the summer. Oceanographic measurements show that near-shore surface water temperatures in the Gulf of Alaska are greatest in the fall. We suggest that the spring peak in terminus velocity is set by higher rates of ice delivery from up-glacier; calving rate increases in a compensatory way, to nearly match the ice velocity. In the fall, ice melt increases terminus undercutting, leading to increased subaerial iceberg calving. Near-terminus ice velocity experiences a compensatory response. Thus the oceanographic and up-glacier ice flux trade off control of the terminus seasonally.

Early Spring Phytoplankton Dynamics in the Western Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Arrigo, Kevin R.; van Dijken, Gert L.; Alderkamp, Anne-Carlijn; Erickson, Zachary K.; Lewis, Kate M.; Lowry, Kate E.; Joy-Warren, Hannah L.; Middag, Rob; Nash-Arrigo, Janice E.; Selz, Virginia; van de Poll, Willem

2017-12-01

The Palmer Long-Term Ecological Research program has sampled waters of the western Antarctic Peninsula (wAP) annually each summer since 1990. However, information about the wAP prior to the peak of the phytoplankton bloom in January is sparse. Here we present results from a spring process cruise that sampled the wAP in the early stages of phytoplankton bloom development in 2014. Sea ice concentrations were high on the shelf relative to nonshelf waters, especially toward the south. Macronutrients were high and nonlimiting to phytoplankton growth in both shelf and nonshelf waters, while dissolved iron concentrations were high only on the shelf. Phytoplankton were in good physiological condition throughout the wAP, although biomass on the shelf was uniformly low, presumably because of heavy sea ice cover. In contrast, an early stage phytoplankton bloom was observed beneath variable sea ice cover just seaward of the shelf break. Chlorophyll a concentrations in the bloom reached 2 mg m-3 within a 100-150 km band between the SBACC and SACCF. The location of the bloom appeared to be controlled by a balance between enhanced vertical mixing at the position of the two fronts and increased stratification due to melting sea ice between them. Unlike summer, when diatoms overwhelmingly dominate the phytoplankton population of the wAP, the haptophyte Phaeocystis antarctica dominated in spring, although diatoms were common. These results suggest that factors controlling phytoplankton abundance and composition change seasonally and may differentially affect phytoplankton populations as environmental conditions within the wAP region continue to change.

Passive infrared ice detection for helicopter applications

NASA Technical Reports Server (NTRS)

Dershowitz, Adam L.; Hansman, R. John, Jr.

1990-01-01

A technique is proposed to remotely detect rotor icing on helicopters by using passive IR thermometry to detect the warming caused by latent heat release as supercooled water freezes. During icing, the ice accretion region will be warmer than the uniced trailing edge, resulting in a characteristic chordwise temperature profile. Preliminary tests were conducted on a static model in the NASA Icing Research Tunnel for a variety of wet (glaze) and dry (rime) ice conditions. The chordwise temperature profiles were confirmed by observation with an IR thermal video system and thermocouple observations. The IR observations were consistent with predictions of the LEWICE ice accretion code, which was used to extrapolate the observations to rotor icing conditions. Based on the static observations, the passive IR ice detection technique appears promising; however, further testing or rotating blades is required.

Wave evolution in the marginal ice zone - Model predictions and comparisons with on-site and remote data

NASA Technical Reports Server (NTRS)

Liu, A. K.; Holt, B.; Vachon, P. W.

1989-01-01

The ocean-wave dispersion relation and viscous attenuation by a sea ice cover were studied for waves in the marginal ice zone (MIZ). The Labrador ice margin experiment (Limex), conducted off the east coast of Newfoundland, Canada in March 1987, provided aircraft SAR, wave buoy, and ice property data. Based on the wave number spectrum from SAR data, the concurrent wave frequency spectrum from ocean buoy data, and accelerometer data on the ice during Limex '87, the dispersion relation has been derived and compared with the model. Accelerometers were deployed at the ice edge and into the ice pack. Data from the accelerometers were used to estimate wave energy attenuation rates and compared with the model. The model-data comparisons are reasonably good for the ice conditions observed during Limex' 87.

Late Pliocene/Pleistocene changes in Arctic sea-ice cover: Biomarker and dinoflagellate records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)

NASA Astrophysics Data System (ADS)

Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens

2014-05-01

Sea ice is a critical component in the (global) climate system that contributes to changes in the Earth's albedo (heat reduction) and biological processes (primary productivity), as well as deep-water formation, a driving mechanism for global thermohaline circulation. Thus, understanding the processes controlling Arctic sea ice variability is of overall interest and significance. Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-ice conditions was developed and is based on the determination of a highly-branched isoprenoid with 25 carbons (IP25; Belt et al., 2007; PIP25 when combined with open-water phytoplankton biomarkers; Müller et al., 2011). Here, we present biomarker data from Ocean Drilling Program (ODP) Sites 911 and 912, recovered from the southern Yermak Plateau and representing information of sea-ice variability, changes in primary productivity and terrigenous input during the last about 3.5 Ma. As Sites 911 and 912 are close to the modern sea-ice edge, their sedimentary records seem to be optimal for studying past variability in sea-ice coverage and testing the applicability of IP25 and PIP25 in older sedimentary sequences. In general, our biomarker records correlate quite well with other climate and sea-ice proxies (e.g., dinoflagellates, IRD, etc.). The main results can be summarized as follows: (1) The novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea ice studies covering at least the last 3.5 Ma, i.e., the time interval including the onset (intensification) of major Northern Hemisphere Glaciation (NHG). (2) These data indicate that sea ice of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. (3) Elevated IP25/PIP25 values indicative for an extended spring sea-ice cover, already occurred between 3.6 and 2.9 Ma, i.e., prior to the onset of major NHG. This may suggest that sea-ice and related albedo effects might have been important for general cooling and ice-sheet build-up. (4) Maxima in sea ice occurred near 3.3, 2.7, 2.1, 1.7 and during the last 1.2 Ma whereas between about 2.6 and 2.2 Ma the sea-ice cover was surprisingly reduced. The IP25 maxima are similar to those determined for the late Holocene. (5) Both, dinoflagellate and IP25/PIP25 data indicate that also during the Late Pliocene Warming Event at least occasionally sea ice must have occurred. (6) This low-resolution pilot study motivates to carry out further detailed high-resolution sea-ice biomarker research on ODP/IODP material in order to prove or disprove these preliminary interpretations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38, 16-27. Müller, J., Wagner, A., Fahl, K., Stein, R., Prange, M., Lohmann, G., 2011. Towards quantitative sea ice reconstructions in the northern North Atlantic: A combined biomarker and numerical modelling approach. Earth Planetary Science Letters 306, 137-148.

Mixing rates and vertical heat fluxes north of Svalbard from Arctic winter to spring

NASA Astrophysics Data System (ADS)

Meyer, Amelie; Fer, Ilker; Sundfjord, Arild; Peterson, Algot K.

2017-06-01

Mixing and heat flux rates collected in the Eurasian Basin north of Svalbard during the N-ICE2015 drift expedition are presented. The observations cover the deep Nansen Basin, the Svalbard continental slope, and the shallow Yermak Plateau from winter to summer. Mean quiescent winter heat flux values in the Nansen Basin are 2 W m-2 at the ice-ocean interface, 3 W m-2 in the pycnocline, and 1 W m-2 below the pycnocline. Large heat fluxes exceeding 300 W m-2 are observed in the late spring close to the surface over the Yermak Plateau. The data consisting of 588 microstructure profiles and 50 days of high-resolution under-ice turbulence measurements are used to quantify the impact of several forcing factors on turbulent dissipation and heat flux rates. Wind forcing increases turbulent dissipation seven times in the upper 50 m, and doubles heat fluxes at the ice-ocean interface. The presence of warm Atlantic Water close to the surface increases the temperature gradient in the water column, leading to enhanced heat flux rates within the pycnocline. Steep topography consistently enhances dissipation rates by a factor of four and episodically increases heat flux at depth. It is, however, the combination of storms and shallow Atlantic Water that leads to the highest heat flux rates observed: ice-ocean interface heat fluxes average 100 W m-2 during peak events and are associated with rapid basal sea ice melt, reaching 25 cm/d.

A laser-based ice shape profilometer for use in icing wind tunnels

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.; Vargas, Mario

1995-01-01

A laser-based profilometer was developed to measure the thickness and shape of ice accretions on the leading edge of airfoils and other models in icing wind tunnels. The instrument is a hand held device that is connected to a desk top computer with a 10 meter cable. It projects a laser line onto an ice shape and used solid state cameras to detect the light scattered by the ice. The instrument corrects the image for camera angle distortions, displays an outline of the ice shape on the computer screen, saves the data on a disk, and can print a full scale drawing of the ice shape. The profilometer has undergone extensive testing in the laboratory and in the NASA Lewis Icing Research Tunnel. Results of the tests show very good agreement between profilometer measurements and known simulated ice shapes and fair agreement between profilometer measurements and hand tracing techniques.

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.

Using Sediment Provenance to Study Ice Streams in the Weddell Sea Embayment of Antarctica

NASA Astrophysics Data System (ADS)

Hemming, S. R.; Williams, T.; Boswell, S.; Licht, K.; Agrios, L.; Brachfeld, S. A.; van de Flierdt, T.; Kuhn, G.; Hillenbrand, C. D.; Zhai, X.

2016-12-01

The geochemical and geochronological fingerprint of rock debris eroded and carried by ice streams may be used to identify the provenance of iceberg-rafted debris (IRD) in the marine sediment record. During deglacial times it has been shown that there is an increase in IRD accumulation in marine sediments underlying the western limb of the Weddell Gyre. We seek to find the provenance of this IRD, identify the ice streams contributing to the IRD load, and interpret the geographic sequence of ice sheet retreat in the Weddell Sea embayment for the last three deglaciations. In December 2014 we conducted fieldwork to collect samples of rock and sediment debris carried by three of the major ice streams draining the Weddell Sea embayment: the Foundation Ice Stream, the Academy Glacier, and the Recovery Glacier. We sampled both modern moraines at the edges of the ice streams and older till on hillsides next to the ice streams. In addition to rocks representing the geology of local outcrops, we found that each of the three ice streams carries a characteristic set of erratic lithologies from further upstream, giving clues to the geology hidden under the ice sheet. Downstream, subglacial till and proximal glaciomarine sediment from existing core sites located at the edge of the Filchner and Ronne Ice Shelves, collected on past expeditions of the RV Polarstern, characterize the geochemical and geochronological fingerprint along ice flow lines extending from the ice streams. Finally, two deep-water RV Polarstern sites contain a continuous record of IRD sourced from the set of Weddell embayment ice streams over the last few glacial cycles. Here we present new 40Ar/39Ar hornblende and biotite thermochronological data from individual mineral grains, K-Ar from the silt fraction, and U-Pb zircon geochronology from the onshore tills and offshore sediments. Using this data we will discuss provenance matching between the IRD and the ice streams, and the possibilities for using provenance to understand ice sheet dynamics over the course of glacial cycles.

Exposed water ice discovered near the south pole of Mars

USGS Publications Warehouse

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

2003-01-01

The Mars Odyssey Thermal Emission Imaging System (THEMIS) has discovered water ice exposed near the edge of Mars' southern perennial polar cap. The surface H2O ice was first observed by THEMIS as a region that was cooler than expected for dry soil at that latitude during the summer season. Diurnal and seasonal temperature trends derived from Mars Global Surveyor Thermal Emission Spectrometer observations indicate that there is H2O ice at the surface. Viking observations, and the few other relevant THEMIS observations, indicate that surface H2O ice may be widespread around and under the perennial CO2 cap.

Potential flow analysis of glaze ice accretions on an airfoil

NASA Technical Reports Server (NTRS)

Zaguli, R. J.

1984-01-01

The results of an analytical/experimental study of the flow fields about an airfoil with leading edge glaze ice accretion shapes are presented. Tests were conducted in the Icing Research Tunnel to measure surface pressure distributions and boundary layer separation reattachment characteristics on a general aviation wing section to which was affixed wooden ice shapes which approximated typical glaze ice accretions. Comparisons were made with predicted pressure distributions using current airfoil analysis codes as well as the Bristow mixed analysis/design airfoil panel code. The Bristow code was also used to predict the separation reattachment dividing streamline by inputting the appropriate experimental surface pressure distribution.

Evolution of a Directional Wave Spectrum in a 3D Marginal Ice Zone with Random Floe Size Distribution

NASA Astrophysics Data System (ADS)

Montiel, F.; Squire, V. A.

2013-12-01

A new ocean wave/sea-ice interaction model is proposed that simulates how a directional wave spectrum evolves as it travels through a realistic marginal ice zone (MIZ), where wave/ice dynamics are entirely governed by coherent conservative wave scattering effects. Field experiments conducted by Wadhams et al. (1986) in the Greenland Sea generated important data on wave attenuation in the MIZ and, particularly, on whether the wave spectrum spreads directionally or collimates with distance from the ice edge. The data suggest that angular isotropy, arising from multiple scattering by ice floes, occurs close to the edge and thenceforth dominates wave propagation throughout the MIZ. Although several attempts have been made to replicate this finding theoretically, including by the use of numerical models, none have confronted this problem in a 3D MIZ with fully randomised floe distribution properties. We construct such a model by subdividing the discontinuous ice cover into adjacent infinite slabs of finite width parallel to the ice edge. Each slab contains an arbitrary (but finite) number of circular ice floes with randomly distributed properties. Ice floes are modeled as thin elastic plates with uniform thickness and finite draught. We consider a directional wave spectrum with harmonic time dependence incident on the MIZ from the open ocean, defined as a continuous superposition of plane waves traveling at different angles. The scattering problem within each slab is then solved using Graf's interaction theory for an arbitrary incident directional plane wave spectrum. Using an appropriate integral representation of the Hankel function of the first kind (see Cincotti et al., 1993), we map the outgoing circular wave field from each floe on the slab boundaries into a directional spectrum of plane waves, which characterizes the slab reflected and transmitted fields. Discretizing the angular spectrum, we can obtain a scattering matrix for each slab. Standard recursive techniques are then used to solve the problem for the full MIZ. Wave attenuation data are obtained using ensemble averaging and preliminary comparisons with field experiment data will be given in the presentation. The model also offers important insights in regards to the spreading of the directional wave spectrum as it penetrates deeper into the MIZ. Cincotti, G., Gori, F., Santarsiero, M., Frezza, F., Furno, F., and Schettini, G. (1993). Plane wave expansion of cylindrical functions. Opt. Commun., 95(4):192-198. Wadhams, P., Squire, V. A., Ewing, J. A., and Pascal, R. W. (1986). The effect of the marginal ice zone on the directional wave spectrum of the ocean. J. Phys. Oceanogr., 16:358-376.

Little ice bodies, huge ice lands, and the up-going of the big water body

NASA Astrophysics Data System (ADS)

Ultee, E.; Bassis, J. N.

2017-12-01

Ice moving out of the huge ice lands causes the big water body to go up. That can cause bad things to happen in places close to the big water body - the land might even disappear! If that happens, people living close to the big water body might lose their homes. Knowing how much ice will come out of the huge ice lands, and when, can help the world plan for the up-going of the big water body. We study the huge ice land closest to us. All around the edge of that huge ice land, there are smaller ice bodies that control how much ice makes it into the big water body. Most ways of studying the huge ice land with computers struggle to tell the computer about those little ice bodies, but we have found a new way. We will talk about our way of studying little ice bodies and how their moving brings about up-going of the big water.

Controlling condensation and frost growth with chemical micropatterns.

PubMed

Boreyko, Jonathan B; Hansen, Ryan R; Murphy, Kevin R; Nath, Saurabh; Retterer, Scott T; Collier, C Patrick

2016-01-22

In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events.

The Effects of the Critical Ice Accretion on Airfoil and Wing Performance

NASA Technical Reports Server (NTRS)

Selig, Michael S.; Bragg, Michael B.; Saeed, Farooq

1998-01-01

In support of the NASA Lewis Modern Airfoils Ice Accretion Test Program, the University of Illinois at Urbana-Champaign provided expertise in airfoil design and aerodynamic analysis to determine the aerodynamic effect of ice accretion on modern airfoil sections. The effort has concentrated on establishing a design/testing methodology for "hybrid airfoils" or "sub-scale airfoils," that is, airfoils having a full-scale leading edge together with a specially designed and foreshortened aft section. The basic approach of using a full-scale leading edge with a foreshortened aft section was considered to a limited extent over 40 years ago. However, it was believed that the range of application of the method had not been fully exploited. Thus a systematic study was being undertaken to investigate and explore the range of application of the method so as to determine its overall potential.

Controlling condensation and frost growth with chemical micropatterns

PubMed Central

Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; Nath, Saurabh; Retterer, Scott T.; Collier, C. Patrick

2016-01-01

In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events. PMID:26796663

Broken vertex symmetry and finite zero-point entropy in the artificial square ice ground state

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

Gliga, Sebastian; Kákay, Attila; Heyderman, Laura J.

In this paper, we study degeneracy and entropy in the ground state of artificial square ice. In theoretical models, individual nanomagnets are typically treated as single spins with only two degrees of freedom, leading to a twofold degenerate ground state with intensive entropy and thus no zero-point entropy. Here, we show that the internal degrees of freedom of the nanostructures can result, through edge bending of the magnetization and breaking of local magnetic symmetry at the vertices, in a transition to a highly degenerate ground state with finite zero-point entropy, similar to that of the pyrochlore spin ices. Finally, wemore » find that these additional degrees of freedom have observable consequences in the resonant spectrum of the lattice, and predict the occurrence of edge “melting” above a critical temperature at which the magnetic symmetry is restored.« less

Broken vertex symmetry and finite zero-point entropy in the artificial square ice ground state

DOE PAGES

Gliga, Sebastian; Kákay, Attila; Heyderman, Laura J.; ...

2015-08-26

In this paper, we study degeneracy and entropy in the ground state of artificial square ice. In theoretical models, individual nanomagnets are typically treated as single spins with only two degrees of freedom, leading to a twofold degenerate ground state with intensive entropy and thus no zero-point entropy. Here, we show that the internal degrees of freedom of the nanostructures can result, through edge bending of the magnetization and breaking of local magnetic symmetry at the vertices, in a transition to a highly degenerate ground state with finite zero-point entropy, similar to that of the pyrochlore spin ices. Finally, wemore » find that these additional degrees of freedom have observable consequences in the resonant spectrum of the lattice, and predict the occurrence of edge “melting” above a critical temperature at which the magnetic symmetry is restored.« less

Monitoring Antarctic ice sheet surface melting with TIMESAT algorithm

NASA Astrophysics Data System (ADS)

Ye, Y.; Cheng, X.; Li, X.; Liang, L.

2011-12-01

Antarctic ice sheet contributes significantly to the global heat budget by controlling the exchange of heat, moisture, and momentum at the surface-atmosphere interface, which directly influence the global atmospheric circulation and climate change. Ice sheet melting will cause snow humidity increase, which will accelerate the disintegration and movement of ice sheet. As a result, detecting Antarctic ice sheet melting is essential for global climate change research. In the past decades, various methods have been proposed for extracting snowmelt information from multi-channel satellite passive microwave data. Some methods are based on brightness temperature values or a composite index of them, and others are based on edge detection. TIMESAT (Time-series of Satellite sensor data) is an algorithm for extracting seasonality information from time-series of satellite sensor data. With TIMESAT long-time series brightness temperature (SSM/I 19H) is simulated by Double Logistic function. Snow is classified to wet and dry snow with generalized Gaussian model. The results were compared with those from a wavelet algorithm. On this basis, Antarctic automatic weather station data were used for ground verification. It shows that this algorithm is effective in ice sheet melting detection. The spatial distribution of melting areas(Fig.1) shows that, the majority of melting areas are located on the edge of Antarctic ice shelf region. It is affected by land cover type, surface elevation and geographic location (latitude). In addition, the Antarctic ice sheet melting varies with seasons. It is particularly acute in summer, peaking at December and January, staying low in March. In summary, from 1988 to 2008, Ross Ice Shelf and Ronnie Ice Shelf have the greatest interannual variability in amount of melting, which largely determines the overall interannual variability in Antarctica. Other regions, especially Larsen Ice Shelf and Wilkins Ice Shelf, which is in the Antarctic Peninsula region, have relative stable and consistent melt occurrence from year to year.

Habitat selection by two beluga whale populations in the Chukchi and Beaufort seas.

PubMed

Hauser, Donna D W; Laidre, Kristin L; Stern, Harry L; Moore, Sue E; Suydam, Robert S; Richard, Pierre R

2017-01-01

There has been extensive sea ice loss in the Chukchi and Beaufort seas where two beluga whale (Delphinapterus leucas) populations occur between July-November. Our goal was to develop population-specific beluga habitat selection models that quantify relative use of sea ice and bathymetric features related to oceanographic processes, which can provide context to the importance of changing sea ice conditions. We established habitat selection models that incorporated daily sea ice measures (sea ice concentration, proximity to ice edge and dense ice) and bathymetric features (slope, depth, proximity to the continental slope, Barrow Canyon, and shore) to establish quantitative estimates of habitat use for the Eastern Chukchi Sea ('Chukchi') and Eastern Beaufort Sea ('Beaufort') populations. We applied 'used v. available' resource selection functions to locations of 65 whales tagged from 1993-2012, revealing large variations in seasonal habitat selection that were distinct between sex and population groups. Chukchi whales of both sexes were predicted to use areas in close proximity to Barrow Canyon (typically <200 km) as well as the continental slope in summer, although deeper water and denser ice were stronger predictors for males than females. Habitat selection differed more between sexes for Beaufort belugas. Beaufort males selected higher ice concentrations (≥40%) than females (0-40%) in July-August. Proximity to shore (<200 km) strongly predicted summer habitat of Beaufort females, while distance to the ice edge was important for male habitat selection, especially during westward migration in September. Overall, our results indicate that sea ice variables were rarely the primary drivers of beluga summer-fall habitat selection. While diminished sea ice may indirectly affect belugas through changes in the ecosystem, associations with bathymetric features that affect prey availability seemed key to habitat selection during summer and fall. These results provide a benchmark by which to assess future changes in beluga habitat use of the Pacific Arctic.

Habitat selection by two beluga whale populations in the Chukchi and Beaufort seas

PubMed Central

Laidre, Kristin L.; Stern, Harry L.; Moore, Sue E.; Suydam, Robert S.; Richard, Pierre R.

2017-01-01

There has been extensive sea ice loss in the Chukchi and Beaufort seas where two beluga whale (Delphinapterus leucas) populations occur between July-November. Our goal was to develop population-specific beluga habitat selection models that quantify relative use of sea ice and bathymetric features related to oceanographic processes, which can provide context to the importance of changing sea ice conditions. We established habitat selection models that incorporated daily sea ice measures (sea ice concentration, proximity to ice edge and dense ice) and bathymetric features (slope, depth, proximity to the continental slope, Barrow Canyon, and shore) to establish quantitative estimates of habitat use for the Eastern Chukchi Sea (‘Chukchi’) and Eastern Beaufort Sea (‘Beaufort’) populations. We applied ‘used v. available’ resource selection functions to locations of 65 whales tagged from 1993–2012, revealing large variations in seasonal habitat selection that were distinct between sex and population groups. Chukchi whales of both sexes were predicted to use areas in close proximity to Barrow Canyon (typically <200 km) as well as the continental slope in summer, although deeper water and denser ice were stronger predictors for males than females. Habitat selection differed more between sexes for Beaufort belugas. Beaufort males selected higher ice concentrations (≥40%) than females (0–40%) in July-August. Proximity to shore (<200 km) strongly predicted summer habitat of Beaufort females, while distance to the ice edge was important for male habitat selection, especially during westward migration in September. Overall, our results indicate that sea ice variables were rarely the primary drivers of beluga summer-fall habitat selection. While diminished sea ice may indirectly affect belugas through changes in the ecosystem, associations with bathymetric features that affect prey availability seemed key to habitat selection during summer and fall. These results provide a benchmark by which to assess future changes in beluga habitat use of the Pacific Arctic. PMID:28235041

Stable isotope fractionation at a glacial hydrothermal field: implications for biogeochemistry and biosignatures on Mars

NASA Astrophysics Data System (ADS)

Cousins, C.; Bowden, R.; Fogel, M.; Cockell, C.; Crawford, I.; Gunn, M.; Karlsson, M. T.; Thorsteinsson, T.

2012-12-01

Hydrothermal environments that arise through the interaction between volcanogenic heat and glacial ice are ideal sites for understanding microbial biogeochemical processes on Earth, and also potentially on Mars where similar volcano-cryosphere interactions are thought to have occurred in the past. The Kverkfjöll subglacial basaltic volcano in central Iceland is geographically isolated, with little influence from flora, fauna, and human activity. Major environmental inputs include geothermal heat, meltwater from ice and snow, and outgassing of CO2, H2S, and SO2. Large physiochemical gradients exist, from steaming fumaroles and boiling hydrothermal pools, to frozen geothermal ground and glacial ice. Stable isotope measurements of total organic carbon, total sulphur, and total nitrogen were coupled with metagenomic analysis of the residing microbial communities, with the aim to identify biogeochemical relationships and processes operating within the Kverkfjöll geothermal environment, and also to identify any isotopic biosignatures that could be preserved within geothermal sediments. This study focused on a variety of samples taken along a hot spring stream that fed into a large ice-confined geothermal lake. Samples analysed range from unconsolidated hot spring sediments, well-developed microbial mats, and dissolved sulphate from hot spring fluids. From the anoxic spring source, the stream water increases in dissolved oxygen, decreases in temperature, yet maintains a pH of ~4. The spring environment is dominated by dissolved sulphate (~2.3 mM), with lower levels of nitrate (~50 μM), phosphorus (~5μM), and ammonium (~1.5 μM). Stable S isotope analysis reveals a fractionation of ~3.2 ‰ between sediment sulphide (as pyrite; δ34S ~0‰), and dissolved water sulphate (δ34S ~3.2 ‰) consistently along the hot spring stream, indicating the presence of an active sulphur cycle, although not one dominated by sulphate reduction (e.g. very negative sulphide δ34S). This fractionation trend was absent within lake sediments, possibly due to a number of mixed sources feeding into the lake, in addition to the spring stream. δ13C in sediments becomes increasingly more negative going downstream, along with increasing removal of TOC. Microbial mats were largely similar with very positive C isotope ratios (δ13C -9.4 to -12.6 ‰) typical of sulphur oxidizing microbes. Bulk genomic DNA was extracted from sediments and mats in order to identify firstly the community composition via 454-pyrosequencing, and secondly the functional diversity within these physiochemically varied environments. This metagenomic data will be combined with stable isotope patterns to elucidate the metabolic potential of hydrothermal environments at Kverkfjöll, which can be used to infer potential biogeochemical pathways of signatures of such pathways on Mars in similar, past environments.

Laminar flow control leading edge glove flight test article development

NASA Technical Reports Server (NTRS)

Pearce, W. E.; Mcnay, D. E.; Thelander, J. A.

1984-01-01

A laminar flow control (LFC) flight test article was designed and fabricated to fit into the right leading edge of a JetStar aircraft. The article was designed to attach to the front spar and fill in approx. 70 inches of the leading edge that are normally occupied by the large slipper fuel tank. The outer contour of the test article was constrained to align with an external fairing aft of the front spar which provided a surface pressure distribution over the test region representative of an LFC airfoil. LFC is achieved by applying suction through a finely perforated surface, which removes a small fraction of the boundary layer. The LFC test article has a retractable high lift shield to protect the laminar surface from contamination by airborne debris during takeoff and low altitude operation. The shield is designed to intercept insects and other particles that could otherwise impact the leading edge. Because the shield will intercept freezing rain and ice, a oozing glycol ice protection system is installed on the shield leading edge. In addition to the shield, a liquid freezing point depressant can be sprayed on the back of the shield.

Interannual Variability of Snow and Ice and Impact on the Carbon Cycle

NASA Technical Reports Server (NTRS)

Yung, Yuk L.

2004-01-01

The goal of this research is to assess the impact of the interannual variability in snow/ice using global satellite data sets acquired in the last two decades. This variability will be used as input to simulate the CO2 interannual variability at high latitudes using a biospheric model. The progress in the past few years is summarized as follows: 1) Albedo decrease related to spring snow retreat; 2) Observed effects of interannual summertime sea ice variations on the polar reflectance; 3) The Northern Annular Mode response to Arctic sea ice loss and the sensitivity of troposphere-stratosphere interaction; 4) The effect of Arctic warming and sea ice loss on the growing season in northern terrestrial ecosystem.

Ice Wedges as Winter Climate Archives - New Results from the Northeast Siberian Arctic and Discussion of the Paleoclimatic Value of Ice Wedges

NASA Astrophysics Data System (ADS)

Opel, T.; Meyer, H.; Laepple, T.; Rehfeld, K.; Mollenhauer, G.; Alexander, D.; Murton, J.

2017-12-01

Arctic climate has experienced major changes over the past millennia that are yet not fully understood in terms of external and internal controls, spatial, temporal, and seasonal patterns. The interpretation of stable isotope data in permafrost ice wedges provides unique information on past winter climate, not or not sufficiently captured by other Arctic climate archives. Ice wedges grow in polygonal patterns owing to frost cracking of the frozen ground in winter and frost-crack filling mostly by snowmelt in spring. Their oxygen isotope values are indicative of temperatures in the cold period of the year (meteorological winter and spring). Recently, an ice-wedge record from the Lena River Delta suggested for the first time, that Siberian winter temperatures were warming throughout the Holocene, contradicting most other Arctic paleoclimate reconstructions. As this was based on a single record, the representativity and spatial extent of the reconstructed winter warming signal remained unclear. In this two-part contribution, we first present a new ice-wedge δ18O record from the Oyogos Yar mainland coast (Northeast Siberian Arctic) and then discuss more generally the paleoclimatic value of ice wedges. The new Oyogos Yar ice-wedge record is based on paired stable-isotope and radiocarbon-age data and spans the last two millennia. It confirms the long-term winter warming signal as well as the unprecedented temperature rise in the last decades. This demonstrates that winter warming over the last millennia is a coherent feature in the Northeastern Siberian Arctic, supporting the hypothesis of an insolation-driven seasonal Holocene temperature evolution followed by a strong warming most likely related to anthropogenic forcing. Considering additional ice-wedge data from the Siberian Laptev Sea region we discuss the paleoclimatic value of ice wedges as high-quality winter climate archive. We assess potentials and challenges of this so far rather understudied source of paleoclimate information that remains to be evaluated systematically. In addition, we outline priorities for future ice-wedge research in order to fully exploit the potential of ice wedges for paleoclimate reconstruction, including e.g. better process understanding, dating, and data-model comparison.

NASA/FAA Tailplane Icing Program: Flight Test Report

NASA Technical Reports Server (NTRS)

Ratvasky, Thomas P.; VanZante, Judith Foss; Sim, Alex

2000-01-01

This report presents results from research flights that explored the characteristics of an ice-contaminated tailplane using various simulated ice shapes attached to the leading edge of the horizontal tailplane. A clean leading edge provided the baseline case, then three ice shapes were flown in order of increasing severity. Flight tests included both steady state and dynamic maneuvers. The steady state points were 1G wings level and steady heading sideslips. The primary dynamic maneuvers were pushovers to various G-levels; elevator doublets; and thrust transitions. These maneuvers were conducted for a full range of flap positions and aircraft angle of attack where possible. The analysis of this data set has clearly demonstrated the detrimental effects of ice contamination on aircraft stability and controllability. Paths to tailplane stall were revealed through parameter isolation and transition studies. These paths are (1) increasing ice shape severity, (2) increasing flap deflection, (3) high or low speeds, depending on whether the aircraft is in a steady state (high speed) or pushover maneuver (low speed), and (4) increasing thrust. The flight research effort was very comprehensive, but did not examine effects of tailplane design and location, or other aircraft geometry configuration effects. However, this effort provided the role of some of the parameters in promoting tailplane stall. The lessons learned will provide guidance to regulatory agencies, aircraft manufacturers, and operators on ice-contaminated tailplane stall in the effort to increase aviation safety and reduce the fatal accident rate.

AKARI Near-infrared Spectroscopic Observations of Interstellar Ices in the Edge-on Starburst Galaxy NGC 253

NASA Astrophysics Data System (ADS)

Yamagishi, Mitsuyoshi; Kaneda, Hidehiro; Ishihara, Daisuke; Oyabu, Shinki; Onaka, Takashi; Shimonishi, Takashi; Suzuki, Toyoaki

2011-04-01

We present the spatially resolved near-infrared (2.5-5.0 μm) spectra of the edge-on starburst galaxy NGC 253 obtained with the Infrared Camera on board AKARI. Near the center of the galaxy, we clearly detect the absorption features of interstellar ices (H2O: 3.05 μm, CO2: 4.27 μm, and XCN: 4.62 μm) and the emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 μm and the hydrogen recombination line Brα at 4.05 μm. We find that the distributions of the ices differ from those of the PAH and gas. We calculate the column densities of the ices and derive the abundance ratios of N(CO2)/N(H2O) = 0.17 ± 0.05. They are similar to those obtained around the massive young stellar objects in our Galaxy (0.17 ± 0.03), although a much stronger interstellar radiation field and higher dust temperature are expected near the center of NGC 253.

Impact resistance of fiber composite blades used in aircraft turbine engines

NASA Technical Reports Server (NTRS)

Friedrich, L. A.; Preston, J. L., Jr.

1973-01-01

Resistance of advanced fiber reinforced epoxy matrix composite materials to ballistic impact was investigated as a function of impacting projectile characteristics, and composite material properties. Ballistic impact damage due to normal impacts, was classified as transverse (stress wave delamination and splitting), penetrative, or structural (gross failure). Steel projectiles were found to be gelatin ice projectiles in causing penetrative damage leading to reduced tensile strength. Gelatin and ice projectiles caused either transverse or structural damage, depending upon projectile mass and velocity. Improved composite transverse tensile strength, use of dispersed ply lay-ups, and inclusion of PRD-49-1 or S-glass fibers correlated with improved resistance of composite materials to transverse damage. In non-normal impacts against simulated blade shapes, the normal velocity component of the impact was used to correlate damage results with normal impact results. Stiffening the leading edge of simulated blade specimens led to reduced ballistic damage, while addition of a metallic leading edge provided nearly complete protection against 0.64 cm diameter steel, and 1.27 cm diameter ice and gelatin projectiles, and partial protection against 2.54 cm diameter projectiles of ice and gelatin.

Vibration characteristics and optimization for panel elastically supported in mobile phone

NASA Astrophysics Data System (ADS)

Kaito, Y.; Honda, S.; Narita, Y.

2016-09-01

In recent years, usage of smartphones and tablet terminals have spread around the world. These devices using touchscreen as a user interface are currently mainstream. Also, in order to let information of input or output surely know to users, there are some types of equipment having vibrational function in touchscreen. Here, the material of touchscreen consists of glass and the glass panel is fixed to a mobile phone's body by adhesive tapes along the edge of the panel. However, due to the difficulty of design of vibration, it needs investigation with a vast number of manufacturing prototypes. Moreover, the vibration characteristic of panels is not enough regarding intensity and a tactile impression. Therefore, in this study, the authors consider the vibration characteristic of glass panel elastically fixed by adhesive tapes along edges. First, they show modeling of adhesive tapes along edges of panel by using translational and rotational springs. Second, they show formulating vibration characteristic by using an energy method. Third, they optimize spring constants of translational and rotational springs by using Genetic Algorithm(GA) from the obtained expression. Finally, they consider natural frequencies and eigenmodes which were acquired from experiments and simulations.

Seasonal variations in the major chemical species of snow at the South East Dome in Greenland

NASA Astrophysics Data System (ADS)

Oyabu, Ikumi; Matoba, Sumito; Yamasaki, Tetsuhide; Kadota, Moe; Iizuka, Yoshinori

2016-03-01

We analyze snow-pit samples collected in May 2015 at the South East Dome (SE Dome) on the Greenland ice sheet. The analysis includes high-resolution records of δD and δ18O, as well as the major ions, CH3SO3-, Cl-, NO3-, SO42-, Na+, NH4+, K+, Ma2+, and Ca2+. We find that the 3.55-m snow pit recorded temperature and aerosol proxies back to summer or autumn of 2014. This indicates a higher accumulation rate than those at other major drilling sites in Greenland. Due to this high accumulation rate, ion concentrations except Na+ are lower than those typical of the central Greenland ice sheet. Concerning seasonal variability, the Na+, Cl-, Ca2+, Mg2+, and NO3- vary similarly to other sites in Greenland, with the Na+ and Cl- peaking in winter to early spring, Ca2+ peaking in spring, Mg2+ peaking in winter to spring, and NO3- towards a peak in summer while showing smaller peaks in winter to spring. The NH4+ increased in spring, and SO42- increased in autumn to winter at SE Dome. On the other hand, the seasonal trend in the Cl-/Na+ ratio differs from those in the inland region. As we did not fully recover one seasonal cycle, some seasonal peaks may have been missed.

Potential Influence of Arctic Sea Ice to the Inter-annual Variations of East Asian Spring Precipitation

NASA Astrophysics Data System (ADS)

Li, Xinxin; Wu, Zhiwei; Li, Yanjie

2016-04-01

Arctic sea ice (ASI) and its potential climatic impacts have received increasing attention during the past decades, yet the relevant mechanisms are far from being understood, particularly on how anomalous ASI affects climate in midlatitudes. The spring precipitation takes up as much as 30% of the annual total and has significant influences to agriculture in East Asia. Here, observed evidence and numerical experiment results manifest that the ASI variability in the Norwegian Sea and the Barents Sea in preceding winter is intimately connected with interannual variations of the East Asian spring precipitation (EAP). The former can explain about 14% of the total variances of the latter. The ASI anomalies persist from winter through the ensuing spring and excite downstream tele-connections of a distinct Rossby wave train prevailing over the Eurasian continent. For the reduced ASI, such a wave train pattern is usually associated with an anomalous low pressure center over Mongolian Plateau, which accelerates the East Asian subtropical westerly jet. The intensified subtropical westerly jet, concurrent with lower-level convergence and upper-level divergence, enhances the local convection and consequently favors rich spring precipitation over East Asia. For the excessive ASI, the situation tends to be opposite. Given that seasonal prediction of the EAP remains a challenging issue, the winter ASI variability may provide another potential predictability source besides El Niño-Southern Oscillation.

Icebergs Adrift in the Amundsen Sea

NASA Technical Reports Server (NTRS)

2002-01-01

The Thwaites Ice Tongue is a large sheet of glacial ice extending from the West Antarctic mainland into the southern Amundsen Sea. A large crack in the Thwaites Tongue was discovered in imagery from Terra's Moderate Resolution Imaging Spectroradiometer (MODIS). Subsequent widening of the crack led to the calving of a large iceberg. The development of this berg, designated B-22 by the National Ice Center, can be observed in these images from the Multi-angle Imaging SpectroRadiometer, also aboard Terra. The two views were acquired by MISR's nadir (vertical-viewing) camera on March 10 and 24, 2002. The B-22 iceberg, located below and to the left of image center, measures approximately 82 kilometers long x 62 kilometers wide. Comparison of the two images shows the berg to have drifted away from the ice shelf edge. The breakup of ice near the shelf edge, in the area surrounding B-22, is also visible in the later image. These natural-color images were acquired during Terra orbits 11843 and 12047, respectively. At the right-hand edge is Pine Island Bay, where the calving of another large iceberg (B-21) occurred in November 2001. B-21 subsequently split into two smaller bergs, both of which are visible to the right of B-22. Antarctic researchers have reported an increase in the frequency of iceberg calvings in recent years. Whether this is the result of a regional climate variation, or connected to the global warming trend, has not yet been established. MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology. Image credit: NASA/GSFC/LaRC/JPL, MISR Team.

Icebergs Adrift in the Amundsen Sea

NASA Technical Reports Server (NTRS)

2002-01-01

The Thwaites Ice Tongue is a large sheet of glacial ice extending from the West Antarctic mainland into the southern Amundsen Sea. A large crack in the Thwaites Tongue was discovered in imagery from Terra's Moderate Resolution Imaging SpectroRadiometer (MODIS). Subsequent widening of the crack led to the calving of a large iceberg. The development of this berg, designated B-22 by the National Ice Center, can be observed in these images from the Multi-angle Imaging SpectroRadiometer, also aboard Terra. The two views were acquired by MISR's nadir (vertical-viewing)camera on March 10 and 24, 2002.

The B-22 iceberg, located below and to the left of image center, measures approximately 82 kilometers long x 62 kilometers wide. Comparison of the two images shows the berg to have drifted away from the ice shelf edge. The breakup of ice near the shelf edge, in the area surrounding B-22, is also visible in the later image.

These natural-color images were acquired during Terra orbits 11843 and 12047, respectively. At the right-hand edge is Pine Island Bay, where the calving of another large iceberg (B-21) occurred in November 2001. B-21 subsequently split into two smaller bergs, both of which are visible to the right of B-22.

Antarctic researchers have reported an increase in the frequency of iceberg calvings in recent years. Whether this is the result of a regional climate variation, or connected to the global warming trend, has not yet been established.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Polar Climate: Arctic sea ice

USGS Publications Warehouse

Stone, R.S.; Douglas, David C.; Belchansky, G.I.; Drobot, S.D.

2005-01-01

Recent decreases in snow and sea ice cover in the high northern latitudes are among the most notable indicators of climate change. Northern Hemisphere sea ice extent for the year as a whole was the third lowest on record dating back to 1973, behind 1995 (lowest) and 1990 (second lowest; Hadley Center–NCEP). September sea ice extent, which is at the end of the summer melt season and is typically the month with the lowest sea ice extent of the year, has decreased by about 19% since the late 1970s (Fig. 5.2), with a record minimum observed in 2002 (Serreze et al. 2003). A record low extent also occurred in spring (Chapman 2005, personal communication), and 2004 marked the third consecutive year of anomalously extreme sea ice retreat in the Arctic (Stroeve et al. 2005). Some model simulations indicate that ice-free summers will occur in the Arctic by the year 2070 (ACIA 2004).

A multisensor approach to sea ice classification for the validation of DMSP-SSM/I passive microwave derived sea ice products

NASA Technical Reports Server (NTRS)

Steffen, K.; Schweiger, A. J.

1990-01-01

The validation of sea ice products derived from the Special Sensor Microwave Imager (SSM/I) on board a DMSP platform is examined using data from the Landsat MSS and NOAA-AVHRR sensors. Image processing techniques for retrieving ice concentrations from each type of imagery are developed and results are intercompared to determine the ice parameter retrieval accuracy of the SSM/I NASA-Team algorithm. For case studies in the Beaufort Sea and East Greenland Sea, average retrieval errors of the SSM/I algorithm are between 1.7 percent for spring conditions and 4.3 percent during freeze up in comparison with Landsat derived ice concentrations. For a case study in the East Greenland Sea, SSM/I derived ice concentration in comparison with AVHRR imagery display a mean error of 9.6 percent.

Investigation of Ice Dynamics in the Marginal Zone.

DTIC Science & Technology

1983-12-01

Unclassified SECURITV CLASSIFICATIGON OF THIS PAGE (111mon Dole Rntormi) Unclassified MTY CLASMSFICATION OF THIS PA6SS16M POW & 6m " trength rather...modeling work, two points are recognized to need a deep consideration: transient cases and stochastic modeling. It is not certain how the velocity...if the thickness effect is indeed significant. The nature of the ice edge jet should be shown: is it transient or steady, forced or caused by ice

Ocean forces Greenland and Greenland forces the ocean: a two-way exchange at Greenland's marine margins

NASA Astrophysics Data System (ADS)

Straneo, F.

2017-12-01

The widespread speed up of Greenland's glaciers, over the last two decades, was unpredicted, revealing major gaps in our understanding of how ice sheets respond to a changing climate. Increased submarine melting at the edge of glaciers has emerged as a key trigger - indicating that glacier/ocean exchanges must be accounted for in ice sheet variability reconstructions and predictions. In parallel, the increasing freshwater discharge into the ocean, associated with Greenland's ice loss, has the potential to impact the North Atlantic's circulation and climate. Thus glacier/ocean exchanges are also relevant to understanding drivers of past and future changes in the North Atlantic Ocean's circulation. Here, I present recent findings from observations collected at the edge of several Greenland glaciers that reveal how melting is caused by intrusions of warm, subtropical waters into the fjords and enhanced by the release of surface melt hundreds of meters below sea level. Similarly, hydrographic and tracer data collected at the glaciers' margins, and within the glacial fjords, reveal how Greenland meltwater are exported in the form of highly diluted glacially modified waters, often subsurface, and temporally lagged with respect to the meltwater release. These findings underline the need for improved representation of ice/ocean exchanges in models in order understand and predict the ice sheet's impact on the ocean and the ocean's impact on the ice sheet.

Ocean forces Greenland and Greenland forces the ocean: a two-way exchange at Greenland's marine margins

NASA Astrophysics Data System (ADS)

Stanley, V.; Schoephoester, P.; Lodge, R. W. D.

2016-12-01

The widespread speed up of Greenland's glaciers, over the last two decades, was unpredicted, revealing major gaps in our understanding of how ice sheets respond to a changing climate. Increased submarine melting at the edge of glaciers has emerged as a key trigger - indicating that glacier/ocean exchanges must be accounted for in ice sheet variability reconstructions and predictions. In parallel, the increasing freshwater discharge into the ocean, associated with Greenland's ice loss, has the potential to impact the North Atlantic's circulation and climate. Thus glacier/ocean exchanges are also relevant to understanding drivers of past and future changes in the North Atlantic Ocean's circulation. Here, I present recent findings from observations collected at the edge of several Greenland glaciers that reveal how melting is caused by intrusions of warm, subtropical waters into the fjords and enhanced by the release of surface melt hundreds of meters below sea level. Similarly, hydrographic and tracer data collected at the glaciers' margins, and within the glacial fjords, reveal how Greenland meltwater are exported in the form of highly diluted glacially modified waters, often subsurface, and temporally lagged with respect to the meltwater release. These findings underline the need for improved representation of ice/ocean exchanges in models in order understand and predict the ice sheet's impact on the ocean and the ocean's impact on the ice sheet.

Flexural-gravity Wave Attenuation in a Thick Ice Shelf

NASA Astrophysics Data System (ADS)

Stephen, R. A.; Bromirski, P. D.; Gerstoft, P.; Chen, Z.; Wiens, D.; Aster, R. C.; Nyblade, A.

2016-12-01

A thirty-four station broadband seismic array was deployed on the Ross Ice Shelf, Antarctica from November 2014 to November 2017. Analyses indicate that phase speeds of infra-gravity wave and tsunami excitation in the 0.003 to 0.02 Hz band are 70 m/s, corresponding to the low frequency limit of flexural-gravity waves. Median spectral amplitudes in this band decay exponentially with distance from the shelf edge in a manner consistent with intrinsic attenuation. Seismic Q is typically 7-9, with an RMS amplitude decay of 0.04-0.05dB/km and an e-folding distance of 175-220 km. Amplitudes do not appear to drop crossing crevasse fields. Vertical and horizontal acceleration levels at stations on the floating ice shelf are 50 dB higher than those on grounded ice. Horizontal accelerations are about 15 dB higher than vertical accelerations. Median spectral levels at 0.003 Hz are within 6 dB for stations from 2 to 430 km from the shelf edge. In contrast, the levels drop by 90 dB at 0.02 Hz. Ocean gravity wave excitation has been proposed as a mechanism that can weaken ice shelves and potentially trigger disintegration events. These measurements indicate that the propensity for shelf weakening and disintegration decays exponentially with distance from the ice front for gravity waves in the 0.003 to 0.02Hz band.

Ice damage effects on an old-field, thinned and fertilized loblolly pine stand in South Carolina

Treesearch

Bryan C. McElvany; Beth W. Richardson; E. David Dickens

2006-01-01

On January 26, 2004, an ice storm impacted 15 South Carolina counties. An established fertilization study area in Clarendon County, SC, was in the affected region. This old-field, thinned, loblolly pine (Pinus taeda L.) stand was fertilized in the spring of 1998. Treatments consisted of: (1) control; (2) poultry litter (7 tons acre-1); and (3)...

Linkages between sea-ice coverage, pelagic-benthic coupling, and the distribution of spectacled eiders: observations in March 2008, 2009 and 2010, northern Bering Sea

USGS Publications Warehouse

Cooper, L.W.; Sexson, M.G.; Grebmeier, J.M.; Gradinger, R.; Mordy, C.W.; Lovvorn, J.R.

2013-01-01

Icebreaker-based sampling in the northern Bering Sea south of St. Lawrence Island in March of 2008, 2009, and 2010 has provided new data on overall ecosystem function early in the annual productive cycle. While water-column chlorophyll concentrations (−2 integrated over the whole water column) are two orders of magnitude lower than observed during the spring bloom in May, sea-ice algal inventories of chlorophyll are high (up to 1 g m−3 in the bottom 2-cm of sea-ice). Vertical fluxes of chlorophyll as measured in sediment traps were between 0.3 to 3.7 mg m−2 d−1 and were consistent with the recent deposition (days to weeks time scale) of chlorophyll to the surface sediments (0–25 mg m−2 present at 0–1 cm). Sediment oxygen respiration rates were lower than previous measurements that followed the spring bloom, but were highest in areas of known high benthic biomass. Early spring release of sedimentary ammonium occurs, particularly southeast of St. Lawrence Island, leading to bottom-water ammonium concentrations of >5 µM. These data, together with other physical, biological, and nutrient data are presented here in conjunction with observed sea-ice dynamics and the distribution of an apex predator, the Spectacled Eider (Somateria fischeri). Sea-ice dynamics in addition to benthic food availability, as determined by sedimentation processes, play a role in the distribution of spectacled eiders, which cannot always access the greatest biomass of their preferred bivalve prey. Overall, the data and observations indicate that the northern Bering Sea is biologically active in late winter, but with strong atmospheric and hydrographic controls. These controls pre-determine nutrient and chlorophyll distributions, water-column mixing, as well as pelagic-benthic coupling.

OVERVIEW OF GOLD HILL MILL, ROAD, AND WHITE PINE TALC ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

OVERVIEW OF GOLD HILL MILL, ROAD, AND WHITE PINE TALC MINE LOOKING EAST. THE OPENING TO THE TALC MINE IS IN THE DARK AREA AT CENTER LEFT EDGE. WARM SPRINGS CAMP IS OUT OF FRAME TO THE RIGHT. - Gold Hill Mill, Warm Spring Canyon Road, Death Valley Junction, Inyo County, CA

Benthic Food Webs of the Chukchi and Beaufort Seas: Relative Importance of Ultimate Carbon Sources in a Changing Climate

NASA Astrophysics Data System (ADS)

Dunton, K. H.; Schonberg, S. V.; Mctigue, N.; Bucolo, P. A.; Connelly, T. L.; McClelland, J. W.

2014-12-01

Changes in sea-ice cover, coastal erosion, and freshwater run-off have the potential to greatly influence carbon assimilation pathways and affect trophic structure in benthic communities across the western Arctic. In the Chukchi Sea, variations in the duration and timing of ice cover affect the delivery of ice algae to a relatively shallow (40-50 m) shelf benthos. Although ice algae are known as an important spring carbon subsidy for marine benthic fauna, ice algal contributions may also help initiate productivity of an active microphytobenthos. Recent studies provide clear evidence that the microphytobenthos are photosynthetically active, and have sufficient light and nutrients for in situ growth. The assimilation of benthic diatoms from both sources may explain the 13C enrichment observed in benthic primary consumers throughout the northern Chukchi. On the eastern Beaufort Sea coast, shallow (2-4 m) estuarine lagoon systems receive massive subsidies of terrestrial carbon that is assimilated by a benthic fauna of significant importance to upper trophic level species, but again, distinct 13C enrichment in benthic primary consumers suggests the existence of an uncharacterized food source. Since ice algae are absent, we believe the 13C enrichment in benthic fauna is caused by the assimilation of benthic microalgae, as reflected in seasonally high benthic chlorophyll in spring under replete light and nutrient conditions. Our observations suggest that changes in ice cover, on both temporal and spatial scales, are likely to have significant effects on the magnitude and timing of organic matter delivery to both shelf and nearshore systems, and that locally produced organic matter may become an increasingly important carbon subsidy that affects trophic assimilation and secondary ecosystem productivity.

The Impact of Stratospheric Circulation Extremes on Minimum Arctic Sea Ice Extent

NASA Astrophysics Data System (ADS)

Smith, K. L.; Polvani, L. M.; Tremblay, B.

2017-12-01

The interannual variability of summertime Arctic sea ice extent (SIE) is anti-correlated with the leading mode of extratropical atmospheric variability in preceding winter, the Arctic Oscillation (AO). Given this relationship and the need for better seasonal predictions of Arctic SIE, we here examine the role of stratospheric circulation extremes and stratosphere-troposphere coupling in linking the AO and Arctic SIE variability. We show that extremes in the stratospheric circulation during the winter season, namely stratospheric sudden warming (SSW) and strong polar vortex (SPV) events, are associated with significant anomalies in sea ice concentration in the Bering Straight and the Sea of Okhotsk in winter, the Barents Sea in spring and along the Eurasian coastline in summer in both observations and a fully-coupled, stratosphere-resolving general circulation model. The accompanying figure shows the composite mean sea ice concentration anomalies from the Whole Atmosphere Community Climate Model (WACCM) for SSWs (N = 126, top row) and SPVs (N = 99, bottom row) for winter (a,d), spring (b,e) and summer (c,f). Consistent with previous work on the AO, we find that SSWs, which are followed by the negative phase of the AO at the surface, result in sea ice growth, whereas SPVs, which are followed by the positive phase of the AO at the surface, result in sea ice loss, although the dynamic and thermodynamic processes driving these sea ice anomalies in the three Arctic regions, noted above, are different. Our analysis suggests that the presence or absence of stratospheric circulation extremes in winter may play a non-trivial role in determining total September Arctic SIE when combined with other factors.

Chemical characterization of individual particles and residuals of cloud droplets and ice crystals collected on board research aircraft in the ISDAC 2008 study

NASA Astrophysics Data System (ADS)

Hiranuma, N.; Brooks, S. D.; Moffet, R. C.; Glen, A.; Laskin, A.; Gilles, M. K.; Liu, P.; MacDonald, A. M.; Strapp, J. W.; McFarquhar, G. M.

2013-06-01

Ambient particles and the dry residuals of mixed-phase cloud droplets and ice crystals were collected during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) near Barrow, Alaska, in spring of 2008. The collected particles were analyzed using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy to identify physico-chemical properties that differentiate cloud-nucleating particles from the total aerosol population. A wide range of individually mixed components was identified in the ambient particles and residuals including organic carbon compounds, inorganics, carbonates, and black carbon. Our results show that cloud droplet residuals differ from the ambient particles in both size and composition, suggesting that both properties may impact the cloud-nucleating ability of aerosols in mixed-phase clouds. The percentage of residual particles which contained carbonates (47%) was almost four times higher than those in ambient samples. Residual populations were also enhanced in sea salt and black carbon and reduced in organic compounds relative to the ambient particles. Further, our measurements suggest that chemical processing of aerosols may improve their cloud-nucleating ability. Comparison of results for various time periods within ISDAC suggests that the number and composition of cloud-nucleating particles over Alaska can be influenced by episodic events bringing aerosols from both the local vicinity and as far away as Siberia.

Modelling radiative transfer through ponded first-year Arctic sea ice with a plane-parallel model

NASA Astrophysics Data System (ADS)

Taskjelle, Torbjørn; Hudson, Stephen R.; Granskog, Mats A.; Hamre, Børge

2017-09-01

Under-ice irradiance measurements were done on ponded first-year pack ice along three transects during the ICE12 expedition north of Svalbard. Bulk transmittances (400-900 nm) were found to be on average 0.15-0.20 under bare ice, and 0.39-0.46 under ponded ice. Radiative transfer modelling was done with a plane-parallel model. While simulated transmittances deviate significantly from measured transmittances close to the edge of ponds, spatially averaged bulk transmittances agree well. That is, transect-average bulk transmittances, calculated using typical simulated transmittances for ponded and bare ice weighted by the fractional coverage of the two surface types, are in good agreement with the measured values. Radiative heating rates calculated from model output indicates that about 20 % of the incident solar energy is absorbed in bare ice, and 50 % in ponded ice (35 % in pond itself, 15 % in the underlying ice). This large difference is due to the highly scattering surface scattering layer (SSL) increasing the albedo of the bare ice.

Fundamental Ice Crystal Accretion Physics Studies

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-Ching; Vargas, Mario; Wright, William B.; Currie, Tom; Knezevici, Danny; Fuleki, Dan

2012-01-01

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 g/m3, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 mm in 3 min. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Fundamental Ice Crystal Accretion Physics Studies

NASA Technical Reports Server (NTRS)

Currie, Tom; Knezevici, Danny; Fuleki, Dan; Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-ching; Vargas, Mario; Wright, William

2011-01-01

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice-crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 grams per cubic meter, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 millimeters in 3 minutes. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Export of Ice-Cavity Water from Pine Island Ice Shelf, West Antarctica

NASA Astrophysics Data System (ADS)

Thurnherr, Andreas; Jacobs, Stanley; Dutrieux, Pierre

2013-04-01

Stability of the West Antarctic Ice Sheet is sensitive to changes in melting at the bottom of floating ice shelves that form the seaward extensions of Antarctic glaciers flowing into the ocean. Not least because observations in the cavities beneath ice shelves are difficult, heat fluxes and melt rates have been inferred from oceanographic measurements obtained near the ice edge (calving fronts). Here, we report on a set of hydrographic and velocity data collected in early 2009 near the calving front of the Amundsen Sea's fast-moving and (until recently) accelerating Pine Island Glacier and its associated ice shelf. CTD profiles collected along the southern half of the meridionally-trending ice front show clear evidence for export of ice-cavity water. That water was carried in the upper ocean along the ice front by a southward current that is possibly related to a striking clockwise gyre that dominated the (summertime) upper-ocean circulation in Pine Island Bay. Signatures of ice-cavity water appear unrelated to current direction along most of the ice front, suggesting that cross-frontal exchange is dominated by temporal variability. However, repeated hydrographic and velocity measurements in a small "ice cove" at the southern end of the calving front show a persistent strong (mean velocity peaking near 0.5 ms-1) outflow of ice-cavity water in the upper 500 m. While surface features (boils) suggested upwelling from deep below the ice shelf, vertical velocity measurements reveal 1) that the mean upwelling within the confines of the cove was too weak to feed the observed outflow, and 2) that large high-frequency internal waves dominated the vertical motion of water inside the cove. These observations indicate that water exchange between the Pine Island Ice Shelf cavity and the Amundsen sea is strongly asymmetric with weak broad inflow at depth and concentrated surface-intensified outflow of melt-laden deep water at the southern edge of the calving front. The lack of significant mean upward motion within the cove strongly suggests that the upwelling takes place within the highly fractured ice along the southern shear margin of the ice shelf. If so, the upwelling water is likely to contribute to both the volume of apparent "basal" melting and to the weakness of that shear margin.

Light Absorption in Arctic Sea Ice - Black Carbon vs Chlorophyll

NASA Astrophysics Data System (ADS)

Ogunro, O. O.; Wingenter, O. W.; Elliott, S.; Hunke, E. C.; Flanner, M.; Wang, H.; Dubey, M. K.; Jeffery, N.

2015-12-01

The fingerprint of climate change is more obvious in the Arctic than any other place on Earth. This is not only because the surface temperature there has increased at twice the rate of global mean temperature but also because Arctic sea ice extent has reached a record low of 49% reduction relative to the 1979-2000 climatology. Radiation absorption through black carbon (BC) deposited on Arctic snow and sea ice surface is one of the major hypothesized contributors to the decline. However, we note that chlorophyll-a absorption owing to increasing biology activity in this region could be a major competitor during boreal spring. Modeling of sea-ice physical and biological processes together with experiments and field observations promise rapid progress in the quality of Arctic ice predictions. Here we develop a dynamic ice system module to investigate discrete absorption of both BC and chlorophyll in the Arctic, using BC deposition fields from version 5 of Community Atmosphere Model (CAM5) and vertically distributed layers of chlorophyll concentrations from Sea Ice Model (CICE). To this point, our black carbon mixing ratios compare well with available in situ data. Both results are in the same order of magnitude. Estimates from our calculations show that sea ice and snow around the Canadian Arctic Archipelago and Baffin Bay has the least black carbon absorption while values at the ice-ocean perimeter in the region of the Barents Sea peak significantly. With regard to pigment concentrations, high amounts of chlorophyll are produced in Arctic sea ice by the bottom microbial community, and also within the columnar pack wherever substantial biological activity takes place in the presence of moderate light. We show that the percentage of photons absorbed by chlorophyll in the spring is comparable to the amount attributed to BC, especially in areas where the total deposition rates are decreasing with time on interannual timescale. We expect a continuous increase in chlorophyll absorption as the biological activity becomes stronger in thin ice toward the center of the Arctic basin. Alternatively, a shift in relative importance could occur as total BC mixing ratios are reduced because of environmental advocacy.

NASA Sea Ice Validation Program for the Defense Meteorological Satellite Program Special Sensor Microwave Imager

NASA Technical Reports Server (NTRS)

Cavalieri, Donald J. (Editor); Crawford, John P.; Drinkwater, Mark R.; Emery, William J.; Eppler, Duane T.; Farmer, L. Dennis; Fowler, Charles W.; Goodberlet, Mark; Jentz, Robert R.; Milman, Andrew

1992-01-01

The history of the program is described along with the SSM/I sensor, including its calibration and geolocation correction procedures used by NASA, SSM/I data flow, and the NASA program to distribute polar gridded SSM/I radiances and sea ice concentrations (SIC) on CD-ROMs. Following a discussion of the NASA algorithm used to convert SSM/I radiances to SICs, results of 95 SSM/I-MSS Landsat IC comparisons for regions in both the Arctic and the Antarctic are presented. The Landsat comparisons show that the overall algorithm accuracy under winter conditions is 7 pct. on average with 4 pct. negative bias. Next, high resolution active and passive microwave image mosaics from coordinated NASA and Navy aircraft underflights over regions of the Beaufort and Chukchi seas in March 1988 were used to show that the algorithm multiyear IC accuracy is 11 pct. on average with a positive bias of 12 pct. Ice edge crossings of the Bering Sea by the NASA DC-8 aircraft were used to show that the SSM/I 15 pct. ice concentration contour corresponds best to the location of the initial bands at the ice edge. Finally, a summary of results and recommendations for improving the SIC retrievals from spaceborne radiometers are provided.

Movement of a female polar bear (Ursus maritimus) in the Kara Sea during the summer sea-ice break-up.

PubMed

Rozhnov, V V; Platonov, N G; Naidenko, S V; Mordvintsev, I N; Ivanov, E A

2017-01-01

The polar bear movement trajectory in relation to onset date of the sea-ice break-up was studied in the coastal zone of the Taimyr Peninsula, eastern part of the Kara Sea, using as an example a female polar bear tagged by a radio collar with an Argos satellite transmitter. Analysis of the long-term pattern of ice melting and tracking, by means of satellite telemetry, of the female polar bear who followed the ice-edge outgoing in the north-eastern direction (in summer 2012) suggests that direction of the polar bear movement depends precisely on the direction of the sea-ice cover break-up.

Frosted Crater

NASA Image and Video Library

2002-08-05

This image from NASA Mars Odyssey spacecraft displays a frosted crater in the Martian northern hemisphere. It was taken during the northern spring, when the CO2 ice cap starts to sublimate and recede.

Evolution of Mars' northern polar seasonal CO2 deposits: Variations in surface brightness and bulk density

NASA Astrophysics Data System (ADS)

Mount, Christopher P.; Titus, Timothy N.

2015-07-01

Small-scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct end-members across the NPSC: (1) Snow deposits may anneal to form an overlying slab layer that fractures. These low-density deposits maintain relatively constant densities over springtime. (2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high-density deposits dramatically increase in density over time. The end-members appear to be correlated with latitude.

Spring in Inca City IV

NASA Image and Video Library

2014-11-13

At certain times in spring, fans take on a gray or blue appearance. This is the time in Inca City when this phenomenon happens, as seen in this image acquired by NASA Mars Reconnaissance Orbiter. On the ridge at the top of the image fans have lengthened and now look more gray than the blotches on the araneiforms. At the bottom of the image they are distinctly blue in color. Two theories have been suggested: perhaps fine particles sink into the seasonal layer of ice so they no longer appear dark. Or, maybe the gas that is released from under the ice condenses and falls to the surface as a bright fresh layer of frost. It is quite likely that both of these theories are correct. http://photojournal.jpl.nasa.gov/catalog/PIA18895

Evolution of Mars’ Northern Polar Seasonal CO2 deposits: variations in surface brightness and bulk density

USGS Publications Warehouse

Mount, Christopher P.; Titus, Timothy N.

2015-01-01

Small scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct endmembers across the NPSC: 1) Snow deposits may anneal to form an overlying slab layer that fractures. These low density deposits maintain relatively constant densities over springtime. 2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high density deposits dramatically increase in density over time. The endmembers appear to be correlated with latitude.

Biological aerosol effects on clouds and precipitation

NASA Astrophysics Data System (ADS)

Hallar, A. Gannet; Huffman, J. Alex; Fridlind, Ann

2012-12-01

Bioaerosol Effects on Clouds Workshop;Steamboat Springs, Colorado, 5-6August 2012 Bioaerosols such as bacteria have been proposed as significant contributors to cloud ice nucleation, but too little is known about the properties and impacts of bioaerosol and other ice nuclei to make reliable conclusions about their wide-scale impact on clouds and precipitation. During late summer an international group of 40 participants met at a Steamboat Springs ski resort to share perspectives on bioaerosol sources, activity, and influence on clouds. Participants who were invited collectively spanned a broad range of expertise, including atmospheric chemistry, microbiology, micrometeorology, and cloud physics, as well as a broad range of research approaches, including laboratory measurement, field measurement, and modeling. Tours of Storm Peak Laboratory (http://www.stormpeak.dri.edu) were offered before and after the workshop.

Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China

NASA Astrophysics Data System (ADS)

Yang, S.; Shi, Y.

2015-10-01

Ice caves exist in locations where annual average air temperature is higher than 0 °C. An example is Ningwu ice cave, Shanxi Province, the largest ice cave in China. In order to quantitatively investigate the mechanism of formation and preservation of the ice cave, we use the finite-element method to simulate the heat transfer process at this ice cave. There are two major control factors. First, there is the seasonal asymmetric heat transfer. Heat is transferred into the ice cave from outside very inefficiently by conduction in spring, summer and fall. In winter, thermal convection occurs that transfers heat very efficiently out of the ice cave, thus cooling it down. Secondly, ice-water phase change provides a heat barrier for heat transfer into the cave in summer. The calculation also helps to evaluate effects of global warming, tourists, colored lights, climatic conditions, etc. for sustainable development of the ice cave as a tourism resource. In some other ice caves in China, managers have installed airtight doors at these ice caves' entrances with the intention of "protecting" these caves, but this in fact prevents cooling in winter and these cave ices will entirely melt within tens of years.

Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China

NASA Astrophysics Data System (ADS)

Yang, S.; Shi, Y.

2015-04-01

Ice caves exist in locations where annual average temperature in higher than 0 °C. An example is Ningwu ice cave, Shanxi Province, the largest ice cave in China. In order to quantitatively explain the mechanism of formation and preservation of the ice cave, we use Finite Element Method to simulate the heat transfer process at this ice cave. There are two major control factors. First, there is the seasonal asymmetric heat transfer. Heat is transferred into the ice cave from outside, very inefficiently by conduction in spring, summer and fall. In winter, thermal convection occurs that transfers heat very efficiently out of the ice cave, thus cooling it down. Secondly, ice-water phase change provides a heat barrier for heat transfer into the cave in summer. The calculation also helps to evaluate effects of global warming, tourists, etc. for sustainable development of ice cave as tourism resource. In some other ice caves in China, managers installed air-tight doors at these ice caves entrance intending to "protect" these caves, but this prevent cooling down these caves in winters and these cave ices will entirely melt within tens of years.

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

Bishop, James K.B.; Wood, Todd

Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Fourmore » hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.« less

Evaluation of factors affecting ice forces at selected bridges in South Dakota

USGS Publications Warehouse

Niehus, Colin A.

2002-01-01

During 1998-2002, the U.S. Geological Survey, in cooperation with the South Dakota Department of Transportation (SDDOT), conducted a study to evaluate factors affecting ice forces at selected bridges in South Dakota. The focus of this ice-force evaluation was on maximum ice thickness and ice-crushing strength, which are the most important variables in the SDDOT bridge-design equations for ice forces in South Dakota. Six sites, the James River at Huron, the James River near Scotland, the White River near Oacoma/Presho, the Grand River at Little Eagle, the Oahe Reservoir near Mobridge, and the Lake Francis Case at the Platte-Winner Bridge, were selected for collection of ice-thickness and ice-crushing-strength data. Ice thickness was measured at the six sites from February 1999 until April 2001. This period is representative of the climate extremes of record in South Dakota because it included both one of the warmest and one of the coldest winters on record. The 2000 and 2001 winters were the 8th warmest and 11th coldest winters, respectively, on record at Sioux Falls, South Dakota, which was used to represent the climate at all bridges in South Dakota. Ice thickness measured at the James River sites at Huron and Scotland during 1999-2001 ranged from 0.7 to 2.3 feet and 0 to 1.7 feet, respectively, and ice thickness measured at the White River near Oacoma/Presho site during 2000-01 ranged from 0.1 to 1.5 feet. At the Grand River at Little Eagle site, ice thickness was measured at 1.2 feet in 1999, ranged from 0.5 to 1.2 feet in 2000, and ranged from 0.2 to 1.4 feet in 2001. Ice thickness measured at the Oahe Reservoir near Mobridge site ranged from 1.7 to 1.8 feet in 1999, 0.9 to 1.2 feet in 2000, and 0 to 2.2 feet in 2001. At the Lake Francis Case at the Platte-Winner Bridge site, ice thickness ranged from 1.2 to 1.8 feet in 2001. Historical ice-thickness data measured by the U.S. Geological Survey (USGS) at eight selected streamflow-gaging stations in South Dakota were compiled for 1970-97. The gaging stations included the Grand River at Little Eagle, the White River near Oacoma, the James River near Scotland, the James River near Yankton, the Vermillion River near Wakonda, the Vermillion River near Vermillion, the Big Sioux River near Brookings, and the Big Sioux River near Dell Rapids. Three ice-thickness-estimation equations that potentially could be used for bridge design in South Dakota were selected and included the Accumulative Freezing Degree Day (AFDD), Incremental Accumulative Freezing Degree Day (IAFDD), and Simplified Energy Budget (SEB) equations. These three equations were evaluated by comparing study-collected and historical ice-thickness measurements to equation-estimated ice thicknesses. Input data required by the equations either were collected or compiled for the study or were obtained from the National Weather Service (NWS). An analysis of the data indicated that the AFDD equation best estimated ice thickness in South Dakota using available data sources with an average variation about the measured value of about 0.4 foot. Maximum potential ice thickness was estimated using the AFDD equation at 19 NWS stations located throughout South Dakota. The 1979 winter (the coldest winter on record at Sioux Falls) was the winter used to estimate the maximum potential ice thickness. The estimated maximum potential ice thicknesses generally are largest in northeastern South Dakota at about 3 feet and are smallest in southwestern and south-central South Dakota at about 2 feet. From 1999 to 2001, ice-crushing strength was measured at the same six sites where ice thickness was measured. Ice-crushing-strength measurements were done both in the middle of the winter and near spring breakup. The maximum ice-crushing strengths were measured in the mid- to late winter before the spring thaw. Measured ice-crushing strengths were much smaller near spring breakup. Ice-crushing strength measured at the six sites

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.

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

STS-48 ESC Earth observation of ice pack, Antarctic Ice Shelf

NASA Technical Reports Server (NTRS)

1991-01-01

STS-48 Earth observation taken aboard Discovery, Orbiter Vehicle (OV) 103, is of the breakup of pack ice along the periphery of the Antarctic Ice Shelf. Strong offshore winds, probably associated with katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filaments of sea ice, icebergs, bergy bits, and growlers to flow northward into the South Atlantic Ocean. These photos are used to study ocean wind, tide and current patterns. Similar views photographed during previous missions, when analyzed with these recent views may yield information about regional ice drift and breakup of ice packs. The image was captured using an electronic still camera (ESC), was stored on a removable hard disk or small optical disk, and was converted to a format suitable for downlink transmission. The ESC documentation was part of Development Test Objective (DTO) 648, Electronic Still Photography.

Analysis of iced wings

NASA Technical Reports Server (NTRS)

Cebeci, T.; Chen, H. H.; Kaups, K.; Schimke, S.; Shin, J.

1992-01-01

A method for computing ice shapes along the leading edge of a wing and a method for predicting its aerodynamic performance degradation due to icing is described. Ice shapes are computed using an extension of the LEWICE code which was developed for airfoils. The aerodynamic properties of the iced wing are determined with an interactive scheme in which the solutions of the inviscid flow equations are obtained from a panel method and the solutions of the viscous flow equations are obtained from an inverse three-dimensional finite-difference boundary-layer method. A new interaction law is used to couple the inviscid and viscous flow solutions. The application of the LEWICE wing code to the calculation of ice shapes on a MS-317 swept wing shows good agreement with measurements. The interactive boundary-layer method is applied to a tapered ice wing in order to study the effect of icing on the aerodynamic properties of the wing at several angles of attack.

Coaxial connector for use with printed circuit board edge connector

DOEpatents

Howard, Donald R.; MacGill, Robert A.

1989-01-01

A coaxial cable connector for interfacing with an edge connector for a printed circuit board whereby a coaxial cable can be interconnected with a printed circuit board through the edge connector. The coaxial connector includes a body having two leg portions extending from one side for receiving the edge connector therebetween, and a tubular portion extending from an opposing side for receiving a coaxial cable. A cavity within the body receives a lug of the edge connector and the center conductor of the coaxial cable. Adjacent lugs of the edge connector can be bend around the edge connector housing to function as spring-loaded contacts for receiving the coaxial connector. The lugs also function to facilitate shielding of the center conductor where fastened to the edge connector lug.

Oceanographic influences on the sea ice cover in the Sea of Okhotsk

NASA Technical Reports Server (NTRS)

Gratz, A. J.; Parkinson, C. L.

1981-01-01

Sea ice conditions in the Sea of Okhotsk, as determined by satellite images from the electrically scanning microwave radiometer on board Nimbus 5, were analyzed in conjunction with the known oceanography. In particular, the sea ice coverage was compared with the bottom bathymetry and the surface currents, water temperatures, and salinity. It is found that ice forms first in cold, shallow, low salinity waters. Once formed, the ice seems to drift in a direction approximating the Okhotsk-Kuril current system. Two basic patterns of ice edge positioning which persist for significant periods were identified as a rectangular structure and a wedge structure. Each of these is strongly correlated with the bathymetry of the region and with the known current system, suggesting that convective depth and ocean currents play an important role in determining ice patterns.

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.

Aerogeophysical evidence for complex subglacial geology below the Rutford drainage basin,WestAntarctica

NASA Astrophysics Data System (ADS)

Jones, P.; Ferraccioli, F.; Corr, H.; Smith, A. M.; King, E.; Vaughan, D.

2003-12-01

A significant part of the West Antarctic Ice Sheet appears to be imposed upon a complex and still largely unknown continental rift system, perhaps featuring sedimentary basins, thin crust and high heat flow. Subglacial geology has been postulated to strongly modulate the dynamics and stability of the ice sheet itself. Specifically, recent aerogeophysics collected over central West Antarctica at edge of the Whitmore Mountains crustal block show that narrow subglacial rift basins with thick sedimentary infill may control the onsets and lateral margins of ice streams. The British Antarctic Survey flew an aerogeophysical survey during the 2001-02 field season: the main aim was to investigate what factors control the location and dynamics of the onset region of the Rutford Ice stream. Airborne radar, aerogravity and aeromagnetic data were simultaneously collected over the drainage basin of the Rutford Ice Stream. The new bedrock elevation grid for the area shows that the Rutford Ice Stream is constrained by a deep bedrock trough with a N-S to NE-SW trend. The onset region appears however to lie within an E-W bedrock trough at the edge of the Ellsworth Mountains crustal block. Bouguer gravity maps do not reveal typical signatures for a coincident deep rift basin at this location. However, a sharp NE-SW trending gradient, likely separating crustal blocks with contrasting crustal thickness is revealed. Aeromagnetic data image NE-SW trends north of the Rutford Ice Stream. In the onset region, these trends appear to be truncated by a NNW-SSE trend, lying on strike with the Ellsworth Mountains. Hence, the new aerogeophysical data suggests greater complexity in the subglacial geology and structure of an onset region of an ice stream compared to previous investigations.

77 FR 16145 - Airworthiness Directives; Bombardier, Inc.

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-20

... chamfer of the upper edge of each leaf spring, and rework if necessary. This AD also requires installing a... [rework] the springs as applicable, and SB 8-76-02 Rev. A to replace the pre-SB 8-76-2 (Mod 8/ 0443... Bulletin A8-76-32, dated January 27, 2012. Do all applicable rework before further flight, in accordance...

Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

USGS Publications Warehouse

Reimnitz, E.; Toimil, L.; Barnes, P.

1978-01-01

Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom processes. A proposed ice zonation, including zones of (1) bottom-fast ice, (2) floating fast ice, (3) stamukhi, and (4) seasonal pack ice, emphasizes ice interaction with the shelf surface and differs from previous zonation. Certain aspects of the results reported here are directly applicable to planned offshore developments in the Prudhoe Bay oil field. Properly placed artificial structures similar to offshore shoals should be able to withstand the forces of the ice, serve to modify the observed ice zonation, and might be used to make the environment less hostile to human activities. ?? 1978.

Frozen waterfall (or ice cascade) growth and decay: a thermodynamic approach

NASA Astrophysics Data System (ADS)

Gauthier, Francis; Montagnat, Maurine; Weiss, Jérôme; Allard, Michel; Hétu, Bernard

2013-04-01

The ice volume evolution of an ice cascade was studied using a thermodynamic model. The model was developed from meteorological data collected in the vicinity of the waterfall and validated from ice volume measurements estimated from terrestrial LiDAR images. The ice cascade forms over a 45 m high rockwall located in northern Gaspésie, Québec, Canada. Two stages of formation were identified. During the first stage, the growth is mainly controlled by air convection around the flowing and freefalling water. The ice cascade growth rate increases with the decreasing air temperature below 0°C and when the water flow reaches its lowest level. During the second stage, the ice cascade covers the entire rockwall surface, water flow is isolated from the outside environment and ice volume increases asymptotically. Heat is evacuated from the water flow through the ice cover by conduction. The growth is mainly controlled by the radiation energy balance but more specifically by the longwave radiation emitted at the ice surface during the night. In spring, melting of the ice cascade is clearly dependant on the sensible heat carried by the increasing water flow and the diffuse solar radiation received at the ice surface during the day.

Test and Analysis Correlation of High Speed Impacts of Ice Cylinders

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Boitnott, Richard L.; Kellas, Sotiris

2006-01-01

During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that could predict the threshold of critical damage to the orbiter s wing leading edge from ice debris impacts. Hence, an experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material models. A high-speed drop tower was configured to capture force time-histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice. However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent force-time history curves were much less dependent on the internal crystalline structure.

Dynamic Crush Characterization of Ice

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Boitnott, Richard L.; Kellas, Sotiris

2006-01-01

During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that could predict the threshold of critical damage to the orbiter's wing leading edge from ice debris impacts. Hence, an experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material models. A high-speed drop tower was configured to capture force time histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice. However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent force-time history curves were much less dependent on the internal crystalline structure.

Ice friction of flared ice hockey skate blades.

PubMed

Federolf, Peter A; Mills, Robert; Nigg, Benno

2008-09-01

In ice hockey, skating performance depends on the skill and physical conditioning of the players and on the characteristics of their equipment. CT Edge have recently designed a new skate blade that angles outward near the bottom of the blade. The objective of this study was to compare the frictional characteristics of three CT Edge blades (with blade angles of 4 degrees, 60, and 8 degrees, respectively) with the frictional characteristics of a standard skate blade. The friction coefficients of the blades were determined by measuring the deceleration of an aluminium test sled equipped with three test blades. The measurements were conducted with an initial sled speed of 1.8 m s(-1) and with a load of 53 kg on each blade. The friction coefficient of the standard blades was 0.0071 (s = 0.0005). For the CT Edge blades with blade angles of 4 degrees, 6 degrees, and 8 degrees, friction coefficients were lower by about 13%, 21%, and 22%, respectively. Furthermore, the friction coefficients decreased with increasing load. The results of this study show that widely accepted paradigms such as "thinner blades cause less friction" need to be revisited. New blade designs might also be able to reduce friction in speed skating, figure skating, bobsledding, and luge.

Nelson River and Hudson Bay

NASA Technical Reports Server (NTRS)

2002-01-01

Rivers that empty into large bodies of water can have a significant impact on the thawing of nearshore winter ice. This true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from May 18, 2001, shows the Nelson River emptying spring runoff from the Manitoba province to the south into the southwestern corner of Canada's Hudson Bay. The warmer waters from more southern latitudes hasten melting of ice near the shore, though some still remained, perhaps because in shallow coastal waters, the ice could have been anchored to the bottom. High volumes of sediment in the runoff turned the inflow brown, and the rim of the retreating ice has taken on a dirty appearance even far to the east of the river's entrance into the Bay. The sediment would have further hastened the melting of the ice because its darker color would have absorbed more solar radiation than cleaner, whiter ice. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Seasonal Thermal Dynamics of Three High Elevation Lakes in the Trinity Alps Wilderness, California

NASA Astrophysics Data System (ADS)

Barnes, J. M.; Huggett, B. W.

2012-12-01

High elevation lakes experience isothermal equilibrium, often called turnover, twice a year: preceding the onset of winter ice cover and following the melt of spring ice cover. The dynamics and evolution of the thermal regime are a function of meteorological forcings (air temperature, wind speed), climate (variable onset of winter and spring), and topographic constraints (access to direct insolation). We have deployed numerous water and air temperature sensors in Emerald, Sapphire and Echo lakes in the Trinity Alps Wilderness of northern California over two hydrologic years in an attempt to determine the onset of turnover events, the duration of turnover and the ice-free season, and to characterize the evolution of the thermocline and its stability over time. Our findings detail thermocline structures in all lakes that vary on hourly to weekly timescales. We also report on our techniques to develop bathymetric maps for each lake and how the use of off-the-shelf technologies and robust GIS analysis can allow the collection of heretofore uncollected baseline data for remote, mountainous regions.

Spring Snow Melt Timing and Changes over Arctic Lands

NASA Technical Reports Server (NTRS)

Foster, J. L.; Robinson, D. A.; Hall, D. K.; Estilow, T. W.

2006-01-01

Spring snow cover over Arctic lands has, on average, melted approximately 4-7 days earlier since the late 1980s compared to the previous 20 years. The earlier disappearance of snow has been identified in non-mountainous regions at the 60 deg and 70 deg N parallels over Eurasia and North America using visible satellite observations of continental snow cover extent (SCE) mapped by the National Oceanic and Atmospheric Administration. The change was greater in the farthest north continental locations. Northern hemisphere SCE declined by almost 10% (May) to 20% (June) between the two intervals. At latitude 70 deg N, eight segments of longitude (each 10 deg in width) show significant (negative) trends. However, only two longitudinal segments at 60 deg N show significant trends, (one positive and one negative). SCE changes coincide with increasing spring warmth and the earlier diminution of sea ice in the last several decades. However, while sea ice has continued to decrease during this recent interval, snowmelt dates in the Arctic changed in a step-like fashion during the mid to late 1980s and have remained much the same since that time.

Flooding of the Taz, Pur, and Yenisey Rivers, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

Each spring and summer, rivers across Siberia experience flooding as the waters in the south begin to melt and run before the ice has retreated from the northern limits. The ice causes jams which are sometimes loosened up using explosives. This pair of MODIS images from June 18, 2002, shows flooding on the Pur (left), Taz (center), and Yenisey (right) Rivers in central Siberia. In the false-color image, ice and snow are red, clouds are white, water is black, and vegetation is green. Bare soil is brown. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

Long-range-transported bioaerosols captured in snow cover on Mount Tateyama, Japan: impacts of Asian-dust events on airborne bacterial dynamics relating to ice-nucleation activities

NASA Astrophysics Data System (ADS)

Maki, Teruya; Furumoto, Shogo; Asahi, Yuya; Lee, Kevin C.; Watanabe, Koichi; Aoki, Kazuma; Murakami, Masataka; Tajiri, Takuya; Hasegawa, Hiroshi; Mashio, Asami; Iwasaka, Yasunobu

2018-06-01

The westerly wind travelling at high altitudes over eastern Asia transports aerosols from the Asian deserts and urban areas to downwind areas such as Japan. These long-range-transported aerosols include not only mineral particles but also microbial particles (bioaerosols), that impact the ice-cloud formation processes as ice nuclei. However, the detailed relations of airborne bacterial dynamics to ice nucleation in high-elevation aerosols have not been investigated. Here, we used the aerosol particles captured in the snow cover at altitudes of 2450 m on Mt Tateyama to investigate sequential changes in the ice-nucleation activities and bacterial communities in aerosols and elucidate the relationships between the two processes. After stratification of the snow layers formed on the walls of a snow pit on Mt Tateyama, snow samples, including aerosol particles, were collected from 70 layers at the lower (winter accumulation) and upper (spring accumulation) parts of the snow wall. The aerosols recorded in the lower parts mainly came from Siberia (Russia), northern Asia and the Sea of Japan, whereas those in the upper parts showed an increase in Asian dust particles originating from the desert regions and industrial coasts of Asia. The snow samples exhibited high levels of ice nucleation corresponding to the increase in Asian dust particles. Amplicon sequencing analysis using 16S rRNA genes revealed that the bacterial communities in the snow samples predominately included plant associated and marine bacteria (phyla Proteobacteria) during winter, whereas during spring, when dust events arrived frequently, the majority were terrestrial bacteria of phyla Actinobacteria and Firmicutes. The relative abundances of Firmicutes (Bacilli) showed a significant positive relationship with the ice nucleation in snow samples. Presumably, Asian dust events change the airborne bacterial communities over Mt Tateyama and carry terrestrial bacterial populations, which possibly induce ice-nucleation activities, thereby indirectly impacting climate change.

Flooding on Russia's Lena River

NASA Technical Reports Server (NTRS)

2002-01-01

Nearly every year in the late spring, ice blocks the flow of water at the mouth of the Lena River in northeastern Russia and gives rise to floods across the Siberian plains. This year's floods can be seen in this image taken on June 2, 2002, by the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument aboard the Terra satellite. The river runs down the left side of the image, and its delta is shrouded in ice (red) at the top of the image. Normally, the river would resemble a thin black line in MODIS imagery. The river, which is Russia's longest, flows 2,641 miles (4,250 kilometers) south to north through Siberia and into the Laptev Sea. In the winter, the river becomes nearly frozen. In the spring, however, water upstream thaws earlier than water at the mouth of the river. As the southern end of the river begins to melt, blocks of ice travel downstream to the still frozen delta, pile up, and often obstruct the flow of water. Flooding doesn't always occur on the same parts of the river. The floods hit further south last year. If the flooding grows severe enough, explosive charges are typically used to break up the ice jams. In these false-color images land areas are a dull, light green or tan, and water is black. Clouds appear pink, and ice comes across as bright red. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Thermonuclear instabilities and plasma edge transport in tokamaks

NASA Astrophysics Data System (ADS)

Fulop, Tunde Maria

High-energy ions generated by fusion reactions in a burning fusion plasma may give rise to different types of wave instabilities. The present thesis investigates two types of such instabilities which recently have been observed in fusion experiments: the Toroidal Alfvén Eigenmode (TAE) instability and the magnetoacoustic cyclotron instability (MCI) which is predicted to give rise to ion cyclotron emission (ICE). The TAE instability may degrade the confinement of fusion-produced high energy alpha particles and adversely affect the possibilities of reaching ignition. The present work derives it generalized expression for the linear growth rate of the instability, by including the effects of finite orbit width and finite Larmor radius of energetic particles, as well as the effects of mode localization and the possible mode excitation by both passing and trapped energetic ions. ICE does not threaten the plasma performance, but it might be useful as a fast ion diagnostic. The ICE originates from the MCI involving fast magnetoacoustic waves driven unstable by toroidicity-affected cyclotron resonance with fast ions. In the present thesis a detailed numerical and analytical investigation of this instability is presented, that explains most of the experimental ICE features observed in JET and TFTR. Moreover, the radial and poloidal localization of the fast magnetoacoustic eigenmodes is investigated, including the effects of toroidicity, ellipticity, the presence of a subpopulation of high energy ions and various profiles of the bulk ion density. In a fusion reactor, the transport of the particles near the edge have a strong influence on the global confinement of the plasma. In the edge region, where neutral atoms and impurity ions are abundant and the temperature and density gradients are large, the assumptions of the standard neoclassical theory break down. In this thesis, we explore the effect of neutral particles on the ion flow shear in the edge region. Furthermore, the neoclassical transport theory in an impure, toroidally rotating plasma is extended to allow for steeper pressure and temperature gradients than are usually considered.

Sediment features at the grounding zone and beneath Ekström Ice Shelf, East Antarctica, imaged using on-ice vibroseis.

NASA Astrophysics Data System (ADS)

Smith, Emma C.; Eisen, Olaf; Hofstede, Coen; Lambrecht, Astrid; Mayer, Christoph

2017-04-01

The grounding zone, where an ice sheet becomes a floating ice shelf, is known to be a key threshold region for ice flow and stability. A better understanding of ice dynamics and sediment transport across such zones will improve knowledge about contemporary and palaeo ice flow, as well as past ice extent. Here we present a set of seismic reflection profiles crossing the grounding zone and continuing to the shelf edge of Ekström Ice Shelf, East Antarctica. Using an on-ice vibroseis source combined with a snowstreamer we have imaged a range of sub-glacial and sub-shelf sedimentary and geomorphological features; from layered sediment deposits to elongated flow features. The acoustic properties of the features as well as their morphology allow us to draw conclusions as to their material properties and origin. These results will eventually be integrated with numerical models of ice dynamics to quantify past and present interactions between ice and the solid Earth in East Antarctica; leading to a better understanding of future contributions of this region to sea-level rise.

Factors driving mercury variability in the Arctic atmosphere and ocean over the past 30 years

NASA Astrophysics Data System (ADS)

Fisher, Jenny A.; Jacob, Daniel J.; Soerensen, Anne L.; Amos, Helen M.; Corbitt, Elizabeth S.; Streets, David G.; Wang, Qiaoqiao; Yantosca, Robert M.; Sunderland, Elsie M.

2013-12-01

observations at Arctic sites (Alert and Zeppelin) show large interannual variability (IAV) in atmospheric mercury (Hg), implying a strong sensitivity of Hg to environmental factors and potentially to climate change. We use the GEOS-Chem global biogeochemical Hg model to interpret these observations and identify the principal drivers of spring and summer IAV in the Arctic atmosphere and surface ocean from 1979-2008. The model has moderate skill in simulating the observed atmospheric IAV at the two sites (r 0.4) and successfully reproduces a long-term shift at Alert in the timing of the spring minimum from May to April (r = 0.7). Principal component analysis indicates that much of the IAV in the model can be explained by a single climate mode with high temperatures, low sea ice fraction, low cloudiness, and shallow boundary layer. This mode drives decreased bromine-driven deposition in spring and increased ocean evasion in summer. In the Arctic surface ocean, we find that the IAV for modeled total Hg is dominated by the meltwater flux of Hg previously deposited to sea ice, which is largest in years with high solar radiation (clear skies) and cold spring air temperature. Climate change in the Arctic is projected to result in increased cloudiness and strong warming in spring, which may thus lead to decreased Hg inputs to the Arctic Ocean. The effect of climate change on Hg discharges from Arctic rivers remains a major source of uncertainty.

Effects of Blank Curvature and Tool Conditions on the Spring Back of Thin Sheet Panel Formed through Local Embossing and Edge L-Bending

NASA Astrophysics Data System (ADS)

Park, Keecheol; Park, Jongyoun; Nam, Jaebok

2011-08-01

Due to the application of thinner sheet steels, the stamped panels in the forming process, generally, are severely distorted. The wavy shape of embossed panel finally converted to residual stress embedded in the panel at final forming (edge L-bending) and it is known as the cause of twisting and oil canning of spring backed panel. Another important source of stamped shape deviation is the curvature of blank. The effects of blank curvature on the shape defects (panel curvature and twisting) after stamping were investigated from defective panel analysis, model experiment and stamping simulation. And the effect of tool conditions (BHF and bead height change) on spring backed shape of real TV bottom chassis were studied. The initial curvature of blank was remained in the flat area of stamped panels as width directional curvature. It converted from length direction curvature of blank. The curvature of initial blank reduced the wavy shape after local emboss forming, but twisting after edge L-bending was increased at large blank curvature cases. The effects of emboss forming conditions, the forming heights and blank holding force were studied and it was found that the wavy shape of stamped sheet was rapidly changed although the forming conditions altered very small amount.

Amplitude-dependent topological edge states in nonlinear phononic lattices

NASA Astrophysics Data System (ADS)

Pal, Raj Kumar; Vila, Javier; Leamy, Michael; Ruzzene, Massimo

2018-03-01

This work investigates the effect of nonlinearities on topologically protected edge states in one- and two-dimensional phononic lattices. We first show that localized modes arise at the interface between two spring-mass chains that are inverted copies of each other. Explicit expressions derived for the frequencies of the localized modes guide the study of the effect of cubic nonlinearities on the resonant characteristics of the interface, which are shown to be described by a Duffing-like equation. Nonlinearities produce amplitude-dependent frequency shifts, which in the case of a softening nonlinearity cause the localized mode to migrate to the bulk spectrum. The case of a hexagonal lattice implementing a phononic analog of a crystal exhibiting the quantum spin Hall effect is also investigated in the presence of weakly nonlinear cubic springs. An asymptotic analysis provides estimates of the amplitude dependence of the localized modes, while numerical simulations illustrate how the lattice response transitions from bulk-to-edge mode-dominated by varying the excitation amplitude. In contrast with the interface mode of the first example studies, this occurs both for hardening and softening springs. The results of this study provide a theoretical framework for the investigation of nonlinear effects that induce and control topologically protected wave modes through nonlinear interactions and amplitude tuning.

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill.

PubMed

Meyer, Bettina; Freier, Ulrich; Grimm, Volker; Groeneveld, Jürgen; Hunt, Brian P V; Kerwath, Sven; King, Rob; Klaas, Christine; Pakhomov, Evgeny; Meiners, Klaus M; Melbourne-Thomas, Jessica; Murphy, Eugene J; Thorpe, Sally E; Stammerjohn, Sharon; Wolf-Gladrow, Dieter; Auerswald, Lutz; Götz, Albrecht; Halbach, Laura; Jarman, Simon; Kawaguchi, So; Krumpen, Thomas; Nehrke, Gernot; Ricker, Robert; Sumner, Michael; Teschke, Mathias; Trebilco, Rowan; Yilmaz, Noyan I

2017-12-01

A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

An Integrated Retrieval Framework for AMSR2: Implications for Light Precipitation and Sea Ice Edge Detectability

NASA Astrophysics Data System (ADS)

Duncan, D.; Kummerow, C. D.; Meier, W.

2016-12-01

Over the lifetime of AMSR-E, operational retrieval algorithms were developed and run for precipitation, ocean suite (SST, wind speed, cloud liquid water path, and column water vapor over ocean), sea ice, snow water equivalent, and soil moisture. With a separate algorithm for each group, the retrievals were never interactive or integrated in any way despite many co-sensitivities. AMSR2, the follow-on mission to AMSR-E, retrieves the same parameters at a slightly higher spatial resolution. We have combined the operational algorithms for AMSR2 in a way that facilitates sharing information between the retrievals. Difficulties that arose were mainly related to calibration, spatial resolution, coastlines, and order of processing. The integration of all algorithms for AMSR2 has numerous benefits, including better detection of light precipitation and sea ice, fewer screened out pixels, and better quality flags. Integrating the algorithms opens up avenues for investigating the limits of detectability for precipitation from a passive microwave radiometer and the impact of spatial resolution on sea ice edge detection; these are investigated using CloudSat and MODIS coincident observations from the A-Train constellation.

Automatic, Satellite-Linked "Webcams" as a Tool in Ice-Shelf and Iceberg Research.

NASA Astrophysics Data System (ADS)

Ross, R.; Okal, M. H.; Thom, J. E.; Macayeal, D. R.

2004-12-01

Important dynamic events governing the behavior of ice shelves and icebergs are episodic in time and small in scale, making them difficult to observe. Traditional satellite imagery is acquired on a rigid schedule with coarse spatial resolution and this means that collisions between icebergs or the processes which create ice "mélange" that fills detachment rifts leading to ice-shelf calving, to give examples, cannot be readily observed. To overcome the temporal and spatial gaps in traditional remote sensing, we have deployed cameras at locations in Antarctica where research is conducted on the calving and subsequent evolution of icebergs. One camera is located at the edge of iceberg C16 in the Ross Sea, and is positioned to capture visual imagery of collisions between C16 and neighboring B15A. The second camera is located within the anticipated detachment rift of a "nascent" iceberg on the Ross Ice Shelf. The second camera is positioned to capture visual imagery of the rift's propagation and the in-fill of ice mélange, which constrains the mechanical influence of such rifts on the surrounding ice shelf. Both cameras are designed for connection to the internet (hence are referred to as "webcams") and possess variable image qualities and image-control technology. The cameras are also connected to data servers via the Iridium satellite telephone network and produce a daily image that is transmitted to the internet through the Iridium connection. Results of the initial trial deployments will be presented as a means of assessing both the techniques involved and the value of the scientific information acquired by these webcams. In the case of the iceberg webcam, several collisions between B15A and C16 were monitored over the period between January, 2003 and December, 2004. The time-lapse imagery obtained through this period showed giant "push mounds" of damaged firn on the edge and surface of the icebergs within the zones of contact as a consequence of the collisions. The push mounds were subsequently unstable, and calved as small scale ice debris soon after the collision, thereby returning the iceberg edge to a clean, vertical cliff-like appearance. A correlation between the iceberg collision record available from the webcam and data from a seismometer located on C16 is anticipated once the seismometer data is recovered. The webcam associated with the detachment rift of the nascent iceberg on the Ross Ice Shelf is planned to be deployed in early November, 2004. If results are available from this deployment, they too will be discussed.

The zooplankton food web under East Antarctic pack ice - A stable isotope study

NASA Astrophysics Data System (ADS)

Jia, Zhongnan; Swadling, Kerrie M.; Meiners, Klaus M.; Kawaguchi, So; Virtue, Patti

2016-09-01

Understanding how sea ice serves zooplankton species during the food-limited season is crucial information to evaluate the potential responses of pelagic food webs to changes in sea-ice conditions in the Southern Ocean. Stable isotope analyses (13C/12C and 15N/14N) were used to compare the dietary preferences and trophic relationships of major zooplankton species under pack ice during two winter-spring transitions (2007 and 2012). During sampling, furcilia of Euphausia superba demonstrated dietary plasticity between years, herbivory when feeding on sea-ice biota, and with a more heterotrophic diet when feeding from both the sea ice and the water column. Carbon isotope signatures suggested that the pteropod Limacina helicina, small copepods Oithona spp., ostracods and amphipods relied heavily on sea-ice biota. Post larval E. superba and omnivorous krill Thysanoessa macrura consumed both water column and ice biota, but further investigations are needed to estimate the contribution from each source. Large copepods and chaetognaths overwintered on a water column-based diet. Our study suggests that warm and permeable sea ice is more likely to provide food for zooplankton species under the ice than the colder ice.

Dynamic and thermodynamic impacts of the winter Arctic Oscillation on summer sea ice extent.

NASA Astrophysics Data System (ADS)

Park, H. S.; Stewart, A.

2017-12-01

Arctic summer sea ice extent exhibits substantial interannual variability, as is highlighted by the remarkable recovery in sea ice extent in 2013 following the record minimum in the summer of 2012. Here, we explore the mechanism via which Arctic Oscillation (AO)-induced ice thickness changes impact summer sea ice, using observations and reanalysis data. A positive AO weakens the basin-scale anticyclonic sea ice drift and decreases the winter ice thickness by 15cm and 10cm in the Eurasian and the Pacific sectors of the Arctic respectively. Three reanalysis datasets show that the (upward) surface heat fluxes are reduced over wide areas of the Arctic, suppressing the ice growth during the positive AO winters. The winter dynamic and thermodynamic thinning preconditions the ice for enhanced radiative forcing via the ice-albedo feedback in late spring-summer, leading to an additional 8-10 cm of thinning over the Pacific sector of the Arctic. Because of these winter AO-induced dynamic and thermodynamics effects, the winter AO explains about 22% (r = -0.48) of the interannual variance of September sea ice extent from year 1980 to 2015.

Strain in shore fast ice due to incoming ocean waves and swell

NASA Astrophysics Data System (ADS)

Fox, Colin; Squire, Vernon A.

1991-03-01

Using a development from the theoretical model presented by Fox and Squire (1990), this paper investigates the strain field generated in shore fast ice by normally incident ocean waves and swell. After a brief description of the model and its convergence, normalized absolute strain (relative to a 1-m incident wave) is found as a function of distance from the ice edge for various wave periods, ice thicknesses, and water depths. The squared transfer function, giving the relative ability of incident waves of different periods to generate strain in the ice, is calculated, and its consequences are discussed. The ice is then forced with a Pierson-Moskowitz spectrum, and the consequent strain spectra are plotted as a function of penetration into the ice sheet. Finally, rms strain, computed as the incoherent sum of the strains resulting from energy in the open water spectrum, is found. The results have implications to the breakup of shore fast ice and hence to the floe size distribution of the marginal ice zone.

Two new ways of mapping sea ice thickness using ocean waves

NASA Astrophysics Data System (ADS)

Wadhams, P.

2010-12-01

TWO NEW METHODS OF MAPPING SEA ICE THICKNESS USING OCEAN WAVES. P. Wadhams (1,2), Martin Doble (1,2) and F. Parmiggiani (3) (1) Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK. (2) Laboratoire d’Océanographie de Villefranche, Université Pierre et Marie Curie, 06234 Villefranche-sur-Mer, France (2) ISAC-CNR, Bologna, Italy Two new methods of mapping ice thickness have been recently developed and tested, both making use of the dispersion relation of ocean waves in ice of radically different types. In frazil-pancake ice, a young ice type in which cakes less than 5 m across float in a suspension of individual ice crystals, the propagation of waves has been successfully modelled by treating the ice layer as a highly viscous fluid. The model predicts a shortening of wavelengths within the ice. Two-dimensional Fourier analysis of successive SAR subscenes to track the directional spectrum of a wave field as it enters an ice edge shows that waves do indeed shorten within the ice, and the change has been successfully used to predict the thickness of the frazil-pancake layer. Concurrent shipborne sampling in the Antarctic has shown that the method is accurate, and we now propose its use throughout the important frazil-pancake regimes in the world ocean (Antarctic circumpolar ice edge zone, Greenland Sea, Bering Sea and others). A radically different type of dispersion occurs when ocean waves enter the continuous icefields of the central Arctic, when they couple with the elastic ice cover to propagate as a flexural-gravity wave. A two-axis tiltmeter array has been used to measure the resulting change in the dispersion relation for long ocean swell (15-30 s) originating from storms in the Greenland Sea. The dispersion relation is slightly different from swell in the open ocean, so if two such arrays are placed a substantial distance (100s of km) apart and used to observe the changing wave period of arrivals from a given storm, the time delay between the arrival of the same frequency at two sites gives the dispersion, and hence the modal ice thickness along the great circle route connecting the arrays. The two quite different methods thus share the use of ocean wave dispersion to infer sea ice thickness.

Polar Bears Across the Arctic Face Shorter Sea Ice Season

NASA Image and Video Library

2017-12-08

Polar bears already face shorter ice seasons - limiting prime hunting and breeding opportunities. Nineteen separate polar bear subpopulations live throughout the Arctic, spending their winters and springs roaming on sea ice and hunting. The bears have evolved mainly to eat seals, which provide necessary fats and nutrients in the harsh Arctic environment. Polar bears can't outswim their prey, so instead they perch on the ice as a platform and ambush seals at breathing holes or break through the ice to access their dens. The total number of ice-covered days declined at the rate of seven to 19 days per decade between 1979 and 2014. The decline was even greater in the Barents Sea and the Arctic basin. Sea ice concentration during the summer months — an important measure because summertime is when some subpopulations are forced to fast on land — also declined in all regions, by 1 percent to 9 percent per decade. Read more: go.nasa.gov/2cIZSSc Photo credit: Mario Hoppmann

Satellite Observations of Antarctic Sea Ice Thickness and Volume

NASA Technical Reports Server (NTRS)

Kurtz, Nathan; Markus, Thorsten

2012-01-01

We utilize satellite laser altimetry data from ICESat combined with passive microwave measurements to analyze basin-wide changes in Antarctic sea ice thickness and volume over a 5 year period from 2003-2008. Sea ice thickness exhibits a small negative trend while area increases in the summer and fall balanced losses in thickness leading to small overall volume changes. Using a five year time-series, we show that only small ice thickness changes of less than -0.03 m/yr and volume changes of -266 cu km/yr and 160 cu km/yr occurred for the spring and summer periods, respectively. The calculated thickness and volume trends are small compared to the observational time period and interannual variability which masks the determination of long-term trend or cyclical variability in the sea ice cover. These results are in stark contrast to the much greater observed losses in Arctic sea ice volume and illustrate the different hemispheric changes of the polar sea ice covers in recent years.

The role of water ice clouds in the Martian hydrologic cycle

NASA Technical Reports Server (NTRS)

James, Philip B.

1990-01-01

A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

Episodic Upwelling of Zooplankton within a Bowhead Whale Feeding Area Near Barrow, AK

DTIC Science & Technology

2011-09-30

the Beaufort year-round. Bowhead whales vocalize using both calls and songs . There was distinct seasonal variability in the detection of the...different species’ calls/ songs . Calls/ songs from whale species were detected in fall and declined as ice concentration in the mooring vicinity increased...Figs. 4 & 5). In the spring, however, whale calls/ songs were detected beginning in April when the region was still covered with ice, and continued

Experimental study of performance degradation of a model helicopter main rotor with simulated ice shapes

NASA Technical Reports Server (NTRS)

Korkan, K. D.; Cross, E. J., Jr.; Cornell, C. C.

1984-01-01

An experimental study utilizing a remote controlled model helicopter has been conducted to measure the performance degradation due to simulated ice accretion on the leading edge of the main rotor for hover and forward flight. The 53.375 inch diameter main rotor incorporates a NACA 0012 airfoil with a generic ice shape corresponding to a specified natural ice condition. Thrust coefficients and torque coefficients about the main rotor were measured as a function of velocity, main rotor RPM, angle-of-incidence of the fuselage, collective pitch angle, and extent of spanwise ice accretion. An experimental airfoil data bank has been determined using a two-dimensional twenty-one inch NACA 0012 airfoil with scaled ice accretion shapes identical to that used on the model helicopter main rotor. The corresponding experimental data are discussed with emphasis on Reynolds number effects and ice accretion scale model testing.

Seasonal to interannual Arctic sea ice predictability in current global climate models

NASA Astrophysics Data System (ADS)

Tietsche, S.; Day, J. J.; Guemas, V.; Hurlin, W. J.; Keeley, S. P. E.; Matei, D.; Msadek, R.; Collins, M.; Hawkins, E.

2014-02-01

We establish the first intermodel comparison of seasonal to interannual predictability of present-day Arctic climate by performing coordinated sets of idealized ensemble predictions with four state-of-the-art global climate models. For Arctic sea ice extent and volume, there is potential predictive skill for lead times of up to 3 years, and potential prediction errors have similar growth rates and magnitudes across the models. Spatial patterns of potential prediction errors differ substantially between the models, but some features are robust. Sea ice concentration errors are largest in the marginal ice zone, and in winter they are almost zero away from the ice edge. Sea ice thickness errors are amplified along the coasts of the Arctic Ocean, an effect that is dominated by sea ice advection. These results give an upper bound on the ability of current global climate models to predict important aspects of Arctic climate.

Organochlorine compounds in ice melt water from Italian Alpine rivers.

PubMed

Villa, Sara; Negrelli, Christian; Finizio, Antonio; Flora, Onelio; Vighi, Marco

2006-01-01

Organochlorine chemicals (OCs) (dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes, and hexachlorobenzene) were measured in ice melt water from five glaciers in the Italian Alps. Even though the data collected may not be sufficient for a precise description of persistent organic pollutant release patterns from glacier melting, they have, however, highlighted the potential for surface water contamination. Concentrations were of the same order of magnitude in all glacial streams, indicating comparable contamination levels in different glaciers of the alpine region. OC levels in nonglacial springs sampled in the same areas are usually lower. Even if differences during the melting season (from spring to autumn) have been identified, a regular seasonal pattern in OC concentrations was not observed. Risk for the aquatic environment is excluded through direct water exposure, but it is likely to occur through biomagnification and secondary poisoning exposure.

Comparison of glacial and non-glacial-fed streams to evaluate the loading of persistent organic pollutants through seasonal snow/ice melt.

PubMed

Bizzotto, E C; Villa, S; Vaj, C; Vighi, M

2009-02-01

The release of persistent organic pollutants (PCBs, HCB, HCHs and DDTs) accumulated in Alpine glaciers, was studied during spring-summer 2006 on the Frodolfo glacial-fed stream (Italian Alps). Samples were also taken on a non-glacial stream in the same valley, to compare POP contribution from different water sources (glacier ice, recent snow and spring). In late spring and early summer (May, June) recent snow melting is the most important process. POP contamination is more affected by local emissions and transport, and comparable levels have been measured in both streams for all studied compounds. In late summer and autumn (July-October), the contribution of ice melting strongly increases. In the glacial-fed stream the concentration of chlorinated pesticides (HCHs and DDTs) is about one order of magnitude higher than in the non-glacial-fed. A different behaviour was observed for PCBs, characterised by a peak in June showing, in both streams, concentrations three orders of magnitude higher than the background levels measured in May and in October. This result should be attributed to local emissions rather than long range atmospheric transport (LRAT). This hypothesis is supported by the PCB congener profile in June strictly comparable to the most commonly used Aroclor technical mixtures. The different seasonal behaviour observed for the different groups of chemicals indicates the POP loading in glacial streams is a combined role of long range atmospheric transport and local emission.

Horizontal sliding of kilometre-scale hot spring area during the 2016 Kumamoto earthquake

PubMed Central

Tsuji, Takeshi; Ishibashi, Jun’ichiro; Ishitsuka, Kazuya; Kamata, Ryuichi

2017-01-01

We report horizontal sliding of the kilometre-scale geologic block under the Aso hot springs (Uchinomaki area) caused by vibrations from the 2016 Kumamoto earthquake (Mw 7.0). Direct borehole observations demonstrate the sliding along the horizontal geological formation at ~50 m depth, which is where the shallowest hydrothermal reservoir developed. Owing to >1 m northwest movement of the geologic block, as shown by differential interferometric synthetic aperture radar (DInSAR), extensional open fissures were generated at the southeastern edge of the horizontal sliding block, and compressional deformation and spontaneous fluid emission from wells were observed at the northwestern edge of the block. The temporal and spatial variation of the hot spring supply during the earthquake can be explained by the horizontal sliding and borehole failures. Because there was no strain accumulation around the hot spring area prior to the earthquake and gravitational instability could be ignored, the horizontal sliding along the low-frictional formation was likely caused by seismic forces from the remote earthquake. The insights derived from our field-scale observations may assist further research into geologic block sliding in horizontal geological formations. PMID:28218298

Azimuthal Structure of the Sand Erg that Encircles the North Polar Water-Ice Cap

NASA Astrophysics Data System (ADS)

Teodoro, L. A.; Elphic, R. C.; Eke, V. R.; Feldman, W. C.; Maurice, S.; Pathare, A.

2011-12-01

The sand erg that completely encircles the perennial water-ice cap that covers the Martian north geographic pole displays considerable azimuthal structure as seen in visible and near-IR images. Much of this structure is associated with the terminations of the many steep troughs that cut spiral the approximately 3 km thick polar ice cap. Other contributions come from the katabatic winds that spill over steep-sided edges of the cap, such as what bounds the largest set of dunes that comprise Olympia Undae. During the spring and summer months when these winds initiate from the higher altitudes that contain sublimating CO2 ice, which is very cold and dry, heat adiabatically when they compress as they lose altitude. These winds should then remove H2O moisture from the uppermost layer of the sand dunes that are directly in their path. Two likely locations where this desiccation may occur preferentially is at the termination of Chasma Boreale and the ice cap at Olympia Undae. We will search for this effect by sharpening the spatial structure of the epithermal neutron counting rates measured at northern high latitudes using the Mars Odyssey Neutron Spectrometer (MONS). The epithermal range of neutron energies is nearly uniquely sensitive to the hydrogen content of surface soils, which should likely be in the form of H2O/OH molecules/radicals. We therefore convert epithermal counting rates in terms of Water-Equivalent-Hydrogen, WEH. However, MONS counting-rate data have a FWHM of ~550 km., which is sufficiently broad to prevent a close association of WEH variability with images of geological features. In this study, we reduce spurious features in the instrument smeared neutron counting rates through deconvolution. We choose the PIXON numerical deconvolution technique for this purpose. This technique uses a statistical approach (Pina 2001, Eke 2001), which is capable of removing spurious features in the data in the presence of noise. We have previously carried out a detailed study of the martian polar regions applying such a methodology to Martian epithermal neutrons (e.g. Teodoro 2010, 2011). In the present study, we will apply this technique to the recent reanalysis of MONS epithermal data (Maurice et al., 2011), which is marked by significantly lower statistical and systematic uncertainties that have plagued older versions of these data.

Changes in winter air temperatures near Lake Michigan, 1851-1993, as determined from regional lake-ice records

USGS Publications Warehouse

Assel, R.A.; Robertson, Dale M.

1995-01-01

Records of freezeup and breakup dates for Grand Traverse Bay, Michigan, and Lake Mendota, Wisconsin, are among the longest ice records available near the Great Lakes, beginning in 185 1 and 1855, respectively. The timing of freezeup and breakup results from an integration of meteorological conditions (primarily air temperature) that occur before these events. Changes in the average timing of these ice-events are translated into changes in air temperature by the use of empirical and process-driven models. The timing of freezeup and breakup at the two locations represents an integration of air temperatures over slightly different seasons (months). Records from both locations indicate that the early winter period before about 1890 was - 15°C cooler than the early winter period after that time; the mean temperature has, however, remained relatively constant since about 1890. Changes in breakup dates demonstrate a similar 1.0-1 .5”C increase in late winter and early spring air temperatures about 1890. More recent average breakup dates at both locations have been earlier than during 1890-1940, indicating an additional warming of 1.2”C in March since about 1940 and a warming of 1 . 1°C in January-March since about 1980. Ice records at these sites will continue to provide an early indication of the anticipated climatic warming, not only because of the large response of ice cover to small changes in air temperature but also because these records integrate climatic conditions during the seasons (winter-spring) when most warming is forecast to occur. Future reductions in ice cover may strongly affect the winter ecology of the Great Lakes by reducing the stable environment required by various levels of the food chain. 

Methane excess in Arctic surface water-triggered by sea ice formation and melting.

PubMed

Damm, E; Rudels, B; Schauer, U; Mau, S; Dieckmann, G

2015-11-10

Arctic amplification of global warming has led to increased summer sea ice retreat, which influences gas exchange between the Arctic Ocean and the atmosphere where sea ice previously acted as a physical barrier. Indeed, recently observed enhanced atmospheric methane concentrations in Arctic regions with fractional sea-ice cover point to unexpected feedbacks in cycling of methane. We report on methane excess in sea ice-influenced water masses in the interior Arctic Ocean and provide evidence that sea ice is a potential source. We show that methane release from sea ice into the ocean occurs via brine drainage during freezing and melting i.e. in winter and spring. In summer under a fractional sea ice cover, reduced turbulence restricts gas transfer, then seawater acts as buffer in which methane remains entrained. However, in autumn and winter surface convection initiates pronounced efflux of methane from the ice covered ocean to the atmosphere. Our results demonstrate that sea ice-sourced methane cycles seasonally between sea ice, sea-ice-influenced seawater and the atmosphere, while the deeper ocean remains decoupled. Freshening due to summer sea ice retreat will enhance this decoupling, which restricts the capacity of the deeper Arctic Ocean to act as a sink for this greenhouse gas.

Interaction of acidic trace gases with ice from a surface science perspective

NASA Astrophysics Data System (ADS)

Waldner, A.; Kong, X.; Ammann, M.; Orlando, F.; Birrer, M.; Artiglia, L.; Bartels-Rausch, T.

2016-12-01

Acidic trace gases, such as HCOOH, HCl and HONO, play important roles in atmospheric chemistry. The presence of ice is known to have the capability to modify this chemistry (Neu et al. 2012). The molecular level processes of the interaction of acidic trace gases with ice are still a matter of debate and a quantification of the uptake is difficult (Dash et al. 2006, Bartels-Rausch et al. 2014, Huthwelker et al. 2006). This hampers a proper inclusion of ice as a substrate in models of various scales as for example in global chemistry climate models that would among others allow predicting large-scale effects of ice clouds. So far, direct observations of the ice surface and of the interaction with trace gases at temperatures and concentrations relevant to the environment are very limited. In this study, we take advantage of the surface and analytical sensitivity as well as the chemical selectivity of photoemission and absorption spectroscopy performed at ambient pressure using the near ambient pressure photoemission endstation (NAPP) at Swiss Light Source to overcome this limitation in environmental science (Orlando et al. 2016). Specifically, ambient pressure X-ray Photoelectron Spectroscopy (XPS) allows us to get information about chemical state and concentration depth profiles of dopants. The combination of XPS with auger electron yield Near-Edge X-ray Absorption Fine Structure (NEXAFS) enables us to locate the dopant and analyse wheather the interaction leads to enhanced surface disorder and to what extent different disorders influences the uptake of the trace gas. For the first time, this study looks directly at the interaction of HCOOH, the strongest organic acid, with ice at 2 different temperatures (233 and 253 K) relevant for environmental science by means of electron spectroscopy. XPS depth profiles indicate that the HCOOH basically remains within the topmost ice layers and O K-edge NEXAFS analysis show that the interaction ice-HCOOH does not lead to enhanced surface disorder at environmentally relevant conditions.

Sparse ice: Geophysical, biological and Indigenous knowledge perspectives on a habitat for ice-associated fauna

NASA Astrophysics Data System (ADS)

Lee, O. A.; Eicken, H.; Weyapuk, W., Jr.; Adams, B.; Mohoney, A. R.

2015-12-01

The significance of highly dispersed, remnant Arctic sea ice as a platform for marine mammals and indigenous hunters in spring and summer may have increased disproportionately with changes in the ice cover. As dispersed remnant ice becomes more common in the future it will be increasingly important to understand its ecological role for upper trophic levels such as marine mammals and its role for supporting primary productivity of ice-associated algae. Potential sparse ice habitat at sea ice concentrations below 15% is difficult to detect using remote sensing data alone. A combination of high resolution satellite imagery (including Synthetic Aperture Radar), data from the Barrow sea ice radar, and local observations from indigenous sea ice experts was used to detect sparse sea ice in the Alaska Arctic. Traditional knowledge on sea ice use by marine mammals was used to delimit the scales where sparse ice could still be used as habitat for seals and walrus. Potential sparse ice habitat was quantified with respect to overall spatial extent, size of ice floes, and density of floes. Sparse ice persistence offshore did not prevent the occurrence of large coastal walrus haul outs, but the lack of sparse ice and early sea ice retreat coincided with local observations of ringed seal pup mortality. Observations from indigenous hunters will continue to be an important source of information for validating remote sensing detections of sparse ice, and improving understanding of marine mammal adaptations to sea ice change.

Persistent Ice on Lake Superior

NASA Image and Video Library

2017-12-08

Though North America is a full month into astronomical spring, the Great Lakes have been slow to give up on winter. As of April 22, 2014, the Great Lakes were 33.9 percent ice covered. The lake they call Superior dominated the pack. In the early afternoon on April 20, 2014, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of Lake Superior, which straddles the United States–Canada border. At the time Aqua passed over, the lake was 63.5 percent ice covered, according to the NOAA Great Lakes Environmental Research Lab (GLERL). Averaged across Lake Superior, ice was 22.6 centimeters (8.9 inches) thick; it was as much as twice that thickness in some locations. GLERL researcher George Leshkevich affirmed that ice cover this spring is significantly above normal. For comparison, Lake Superior had 3.6 percent ice cover on April 20, 2013; in 2012, ice was completely gone by April 12. In the last winter that ice cover grew so thick on Lake Superior (2009), it reached 93.7 percent on March 2 but was down to 6.7 percent by April 21. Average water temperatures on all of the Great Lakes have been rising over the past 30 to 40 years and ice cover has generally been shrinking. (Lake Superior ice was down about 79 percent since the 1970s.) But chilled by persistent polar air masses throughout the 2013-14 winter, ice cover reached 88.4 percent on February 13 and 92.2 percent on March 6, 2014, the second highest level in four decades of record-keeping. Air temperatures in the Great Lakes region were well below normal for March, and the cool pattern is being reinforced along the coasts because the water is absorbing less sunlight and warming less than in typical spring conditions. The graph below, based on data from Environment Canada, shows the 2014 conditions for all of the Great Lakes in mid-April compared to the past 33 years. Lake Superior ice cover got as high as 95.3 percent on March 19. By April 22, it was reported at 59.9 percent; Lake Huron was nearly 30.4 percent. News outlets noted that as many as 70 ships have been backed up in Lakes Michigan, Huron, and Erie, waiting for passage into ports on Lake Superior. The U.S. Coast Guard has been grouping ships together into small convoys after they pass through locks at Sault Ste. Marie, in order to maximize ice-breaking efficiency and to protect ships from damage. Superior is the world’s largest freshwater lake by area (82,100 square kilometers or 31,700 square miles) and the third largest by volume. The waters average 147 meters (483 feet) in depth, and the basin is believed to hold about 10 percent of the world’s liquid fresh water. NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Caption by Mike Carlowicz. Read more: earthobservatory.nasa.gov/IOTD/view.php?id=83541&eocn... Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

BRITICE-CHRONO: Constraining rates and style of marine-influenced ice sheet decay to provide a data-rich playground for ice sheet modellers

NASA Astrophysics Data System (ADS)

Clark, Chris

2014-05-01

Uncertainty exists regarding the fate of the Antarctic and Greenland ice sheets and how they will respond to forcings from sea level and atmospheric and ocean temperatures. If we want to know more about the mechanisms and rate of change of shrinking ice sheets, then why not examine an ice sheet that has fully disappeared and track its retreat through time? If achieved in enough detail such information could become a data-rich playground for improving the next breed of numerical ice sheet models to be used in ice and sea level forecasting. We regard that the last British-Irish Ice Sheet is a good target for this work, on account of its small size, density of information and with its numerous researchers already investigating it. BRITICE-CHRONO is a large (>45 researchers) NERC-funded consortium project comprising Quaternary scientists and glaciologists who will search the seafloor around Britain and Ireland and parts of the landmass in order to find and extract samples of sand, rock and organic matter that can be dated (OSL; Cosmogenic; 14C) to reveal the timing and rate of change of the collapsing British-Irish Ice Sheet. The purpose is to produce a high resolution dataset on the demise on an ice sheet - from the continental shelf edge and across the marine to terrestrial transition. Some 800 new date assessments will be added to those that already exist. This poster reports on the hypotheses that underpin the work. Data on retreat will be collected by focusing on 8 transects running from the continental shelf edge to a short distance (10s km) onshore and acquiring marine and terrestrial samples for geochronometric dating. The project includes funding for 587 radiocarbon, 140 OSL and 158 TCN samples for surface exposure dating; with sampling accomplished by two research cruises and 16 fieldwork campaigns. Results will reveal the timing and rate of change of ice margin recession for each transect, and combined with existing landform and dating databases, will be used to build an ice sheet-wide empirical reconstruction of retreat incorporating Bayesian analysis to assess uncertainty. We invite and encourage ice sheet modellers to use our data for modelling experiments and in particular to explore the role of bed topography in modulating ice retreat.

Ocean forcing of Ice Sheet retreat in central west Greenland from LGM to the early Holocene

NASA Astrophysics Data System (ADS)

Jennings, Anne E.; Andrews, John T.; Ó Cofaigh, Colm; Onge, Guillaume St.; Sheldon, Christina; Belt, Simon T.; Cabedo-Sanz, Patricia; Hillaire-Marcel, Claude

2017-08-01

Three radiocarbon dated sediment cores from trough mouth fans on the central west Greenland continental slope were studied to determine the timing and processes of Greenland Ice Sheet (GIS) retreat from the shelf edge during the last deglaciation and to test the role of ocean forcing (i.e. warm ocean water) thereon. Analyses of lithofacies, quantitative x-ray diffraction mineralogy, benthic foraminiferal assemblages, the sea-ice biomarker IP25, and δ18 O of the planktonic foraminifera Neogloboquadrina pachyderma sinistral from sediments in the interval from 17.5-10.8 cal ka BP provide consistent evidence for ocean and ice sheet interactions during central west Greenland (CWG) deglaciation. The Disko and Uummannaq ice streams both retreated from the shelf edge after the last glacial maximum (LGM) under the influence of subsurface, warm Atlantic Water. The warm subsurface water was limited to depths below the ice stream grounding lines during the LGM, when the GIS terminated as a floating ice shelf in a sea-ice covered Baffin Bay. The deeper Uummannaq ice stream retreated first (ca. 17.1 cal ka BP), while the shallower Disko ice stream retreated at ca. 16.2 cal ka BP. The grounding lines were protected from accelerating mass loss (calving) by a buttressing ice shelf and by landward shallowing bathymetry on the outer shelf. Calving retreat was delayed until ca. 15.3 cal ka BP in the Uummannaq Trough and until 15.1 cal ka BP in the Disko Trough, during another interval of ocean warming. Instabilities in the Laurentide, Innuitian and Greenland ice sheets with outlets draining into northern Baffin Bay periodically released cold, fresh water that enhanced sea ice formation and slowed GIS melt. During the Younger Dryas, the CWG records document strong cooling, lack of GIS meltwater, and an increase in iceberg rafted material from northern Baffin Bay. The ice sheet remained in the cross-shelf troughs until the early Holocene, when it retreated rapidly by calving and strong melting under the influence of atmosphere and ocean warming and a steep reverse slope toward the deep fjords. We conclude that ocean warming played an important role in the palaeo-retreat dynamics of the GIS during the last deglaciation.

Pit Where a Scarp Exposes an Underground Deposit of Martian Ice

NASA Image and Video Library

2018-01-11

At this wedge-shaped pit on Mars, the steep slope (or scarp) at the northern edge (toward the top of the image) exposes a cross-section of a thick sheet of underground water ice. The image is from the High Resolution Imaging Stereo Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The gray-scale portions on left and right are from a single waveband in the red-light portion of the visible spectrum. The middle section, in enhanced color, combines data from red, near-infrared and blue-green wavebands. The scene covers an area about three miles (five kilometers) wide. Figure 1 includes a one-kilometer scale bar. One kilometer is about six-tenths of a mile. The ice-exposing scarp at the northern edge of the pit has a steepness of about 45 to 55 degrees, plunging from the relatively level ground outside the pit. The HiRISE observation ESP_022389_1230 was made on May 7, 2011, at 56.6 degrees south latitude, 114.1 degrees east longitude. In January 2018, in the journal Science, researchers reported finding and studying eight such ice-exposing scarps in the middle latitudes of Mars. The presence of vast underground ice deposits in Mars' middle latitudes was known previously. The report of unusual sites where they are exposed provides new information about their depth and layering. It also identifies potential water resources for future Mars missions and possibilities for studying Martian climate history by examining the ice layers holding a record of past climate cycles. The ice may have been deposited as snow when the tilt of Mars' rotation axis was greater than it is now. https://photojournal.jpl.nasa.gov/catalog/PIA22078

Estimation of ice activation parameters within a particle tracking Lagrangian cloud model using the ensemble Kalman filter to match ISCDAC golden case observations

NASA Astrophysics Data System (ADS)

Reisner, J. M.; Dubey, M. K.

2010-12-01

To both quantify and reduce uncertainty in ice activation parameterizations for stratus clouds occurring in the temperature range between -5 to -10 C ensemble simulations of an ISDAC golden case have been conducted. To formulate the ensemble, three parameters found within an ice activation model have been sampled using a Latin hypercube technique over a parameter range that induces large variability in both number and mass of ice. The ice activation model is contained within a Lagrangian cloud model that simulates particle number as a function of radius for cloud ice, snow, graupel, cloud, and rain particles. A unique aspect of this model is that it produces very low levels of numerical diffusion that enable the model to accurately resolve the sharp cloud edges associated with the ISDAC stratus deck. Another important aspect of the model is that near the cloud edges the number of particles can be significantly increased to reduce sampling errors and accurately resolve physical processes such as collision-coalescence that occur in this region. Thus, given these relatively low numerical errors, as compared to traditional bin models, the sensitivity of a stratus deck to changes in parameters found within the activation model can be examined without fear of numerical contamination. Likewise, once the ensemble has been completed, ISDAC observations can be incorporated into a Kalman filter to optimally estimate the ice activation parameters and reduce overall model uncertainty. Hence, this work will highlight the ability of an ensemble Kalman filter system coupled to a highly accurate numerical model to estimate important parameters found within microphysical parameterizations containing high uncertainty.

Uncovering the glacial history of the Irish continental shelf (Invited)

NASA Astrophysics Data System (ADS)

Dunlop, P.; Benetti, S.; OCofaigh, C.

2013-12-01

In 1999 the Irish Government initiated a €32 million survey of its territorial waters known as the Irish National Seabed Survey (INSS). The INSS is amongst the largest marine mapping programmes ever undertaken anywhere in the world and provides high-resolution multibeam, backscatter and seismic data of the seabed around Ireland. These data have been used to provide the first clear evidence for extensive glaciation of the continental shelf west and northwest of Ireland. Streamlined drumlins on the mid to outer shelf record former offshore-directed ice flow towards the shelf edge and show that the ice sheet was grounded in a zone of confluence where ice flowing onto the shelf from northwest Ireland merged with ice flowing across the Malin Shelf from southwest Scotland. The major glacial features on the shelf are well developed nested arcuate moraine systems that mark the position of the ice sheet margin and confirm that the former British Irish Ice Sheet was grounded as far as the shelf edge around 100 km offshore of west Donegal at the last glacial maximum. Distal to the moraines, on the outermost shelf, prominent zones of iceberg plough marks give way to the Barra/Donegal fan and a well developed system of gullies and canyons which incise the continental slope. Since 2008 several scientific cruises have retrieved cores from the shelf and slope to help build a more detailed understanding of glacial events in this region. This presentation will provide an overview of the glacial history of the Irish shelf and will discuss ongoing research programmes that are building on the initial research findings to produce a better understanding of the nature and timing of ice sheet events in this region.

"Crystals within Crystals: The Story of Sea Ice". A Classroom-Based Outreach Project Communicating Cutting-Edge Ocean Science to School Pupils

NASA Astrophysics Data System (ADS)

Butler, B.

2016-02-01

'Crystals within Crystals: The story of sea ice' is a UK based outreach project based that uses a range practical tools to engage school students with cutting edge scientific research that relates to the use of some of the world's most powerful X-rays in sea ice research. The project is delivered in the form of a classroom workshop that first introduces school pupils (aged 11-14) to seawater and the salts that give it a salinity. The pupils are then shown how the presence of salts within seawater results in very important physical changes when the liquid freezes, which includes different structural and optical properties of the ice. The properties of the ice are then linked to the presence of countless microscopic salt crystals that are trapped within the microstructure of the frozen seawater, which is explained with use of a novel crystal growth demonstration. Given that there is currently no way of successfully removing these salt crystals from the ice, the workshop culminates in explaining how some of the worlds most powerful X-rays can be used to investigate processes that otherwise remain elusive. The workshop introduces students to the fundamental principles of scientific enquiry, the sea ice environment, and the power of X-rays in investigating the properties of crystals. Here we present information that outlines a host of practical and project management tools that are applicacble to outreach projects in the the field of ocean sciences, with the aim of seeding ideas and interest for other graduate student to enage with the public during their studies.

Alaska North Shore Ocean Acoustics Study

DTIC Science & Technology

2015-09-30

effects of changing ice cover, wind patterns and circulation/upwelling on underwater sound propagation and ambient noise in the areas of continental ...noise field along the edge of Arctic continental shelf. Underwater sound propagation in Arctic oceans with ice cover is influenced by the elastic...von der Heydt has been implmenting the following system upgrades: 1. Replacing the existing Seascan timebase ( drift 2 to 3ms/day) with a

Depositional environments of the Rock Springs Formation, southwest flank of the Rock Springs Uplift, Wyoming.

USGS Publications Warehouse

Kirschbaum, M.A.

1986-01-01

This deltaic Upper Cretaceous Rock Springs Formation of the Mesaverde Group was deposited during early Campanian time near the end of the regressive phase of the Niobrara cyclothem. On the southwest end of the Uplift, part of the delta system is exposed near the seaward edge of a series of transgressive/regressive sequences, which consist of intertonguing prodelta, delta-front, and delta-plain deposits. Eight major delta-front sandstones are vertically stacked and laterally continuous throughout the main study area.-from Author

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, noted previously by HST in 1995 and Mariner 9 in 1972; this may be due to topography, which isn't well known, or to wave structure in the circulation. This map was assembled from WFPC2 images obtained between Dec. 30, 1996 and Jan. 4, 1997.

March 30, 1997 (early summer): The cap has fully retreated to its remnant core of water-ice. This residual cap is actually almost cut into two by a large, horn-shaped canyon called Chasma Borealis which is cut deeply into the polar terrain. The HST images also reveal a curious layered terrain which is evidence of past climatic changes on Mars. The sublimation of all of the carbon dioxide has exposed the ring of dark sand dunes which encircle the North Polar Cap. Outliers of ice persist south of the polar sand sea (between the 3 o'clock and 9 o'clock positions). The bright circular features at 3, 6, and 9 o'clock are ice-filled craters.

All images were taken with the Wide Field and Planetary Camera 2. The color is constructed from images taken in red (673 nm) , blue (410 nm) and green (502 nm) light. The resolution at the North Pole ranges from about 115 km/pixel in October '96 to about 45 km/pixel in March '97.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Sea-ice eukaryotes of the Gulf of Finland, Baltic Sea, and evidence for herbivory on weakly shade-adapted ice algae.

PubMed

Majaneva, Markus; Blomster, Jaanika; Müller, Susann; Autio, Riitta; Majaneva, Sanna; Hyytiäinen, Kirsi; Nagai, Satoshi; Rintala, Janne-Markus

2017-02-01

To determine community composition and physiological status of early spring sea-ice organisms, we collected sea-ice, slush and under-ice water samples from the Baltic Sea. We combined light microscopy, HPLC pigment analysis and pyrosequencing, and related the biomass and physiological status of sea-ice algae with the protistan community composition in a new way in the area. In terms of biomass, centric diatoms including a distinct Melosira arctica bloom in the upper intermediate section of the fast ice, dinoflagellates, euglenoids and the cyanobacterium Aphanizomenon sp. predominated in the sea-ice sections and unidentified flagellates in the slush. Based on pigment analyses, the ice-algal communities showed no adjusted photosynthetic pigment pools throughout the sea ice, and the bottom-ice communities were not shade-adapted. The sea ice included more characteristic phototrophic taxa (49%) than did slush (18%) and under-ice water (37%). Cercozoans and ciliates were the richest taxon groups, and the differences among the communities arose mainly from the various phagotrophic protistan taxa inhabiting the communities. The presence of pheophytin a coincided with an elevated ciliate biomass and read abundance in the drift ice and with a high Eurytemora affinis read abundance in the pack ice, indicating that ciliates and Eurytemora affinis were grazing on algae. Copyright © 2016 Elsevier GmbH. All rights reserved.

Impact Testing on Reinforced Carbon-Carbon Flat Panels with Ice Projectiles for the Space Shuttle Return to Flight Program

NASA Technical Reports Server (NTRS)

Melis, Matthew E.; Revilock, Duane M.; Pereira, Michael J.; Lyle, Karen H.

2009-01-01

Following the tragedy of the Orbiter Columbia (STS-107) on February 1, 2003, a major effort commenced to develop a better understanding of debris impacts and their effect on the space shuttle subsystems. An initiative to develop and validate physics-based computer models to predict damage from such impacts was a fundamental component of this effort. To develop the models it was necessary to physically characterize reinforced carbon-carbon (RCC) along with ice and foam debris materials, which could shed on ascent and impact the orbiter RCC leading edges. The validated models enabled the launch system community to use the impact analysis software LS-DYNA (Livermore Software Technology Corp.) to predict damage by potential and actual impact events on the orbiter leading edge and nose cap thermal protection systems. Validation of the material models was done through a three-level approach: Level 1--fundamental tests to obtain independent static and dynamic constitutive model properties of materials of interest, Level 2--subcomponent impact tests to provide highly controlled impact test data for the correlation and validation of the models, and Level 3--full-scale orbiter leading-edge impact tests to establish the final level of confidence for the analysis methodology. This report discusses the Level 2 test program conducted in the NASA Glenn Research Center (GRC) Ballistic Impact Laboratory with ice projectile impact tests on flat RCC panels, and presents the data observed. The Level 2 testing consisted of 54 impact tests in the NASA GRC Ballistic Impact Laboratory on 6- by 6-in. and 6- by 12-in. flat plates of RCC and evaluated three types of debris projectiles: Single-crystal, polycrystal, and "soft" ice. These impact tests helped determine the level of damage generated in the RCC flat plates by each projectile and validated the use of the ice and RCC models for use in LS-DYNA.

Tidal Modulation of Ice-shelf Flow: a Viscous Model of the Ross Ice Shelf

NASA Technical Reports Server (NTRS)

Brunt, Kelly M.; MacAyeal, Douglas R.

2014-01-01

Three stations near the calving front of the Ross Ice Shelf, Antarctica, recorded GPS data through a full spring-neap tidal cycle in November 2005. The data revealed a diurnal horizontal motion that varied both along and transverse to the long-term average velocity direction, similar to tidal signals observed in other ice shelves and ice streams. Based on its periodicity, it was hypothesized that the signal represents a flow response of the Ross Ice Shelf to the diurnal tides of the Ross Sea. To assess the influence of the tide on the ice-shelf motion, two hypotheses were developed. The first addressed the direct response of the ice shelf to tidal forcing, such as forces due to sea-surface slopes or forces due to sub-ice-shelf currents. The second involved the indirect response of ice-shelf flow to the tidal signals observed in the ice streams that source the ice shelf. A finite-element model, based on viscous creep flow, was developed to test these hypotheses, but succeeded only in falsifying both hypotheses, i.e. showing that direct tidal effects produce too small a response, and indirect tidal effects produce a response that is not smooth in time. This nullification suggests that a combination of viscous and elastic deformation is required to explain the observations.

Time-dependence of sea-ice concentration and multiyear ice fraction in the Arctic Basin

USGS Publications Warehouse

Gloersen, P.; Zwally, H.J.; Chang, A.T.C.; Hall, D.K.; Campbell, W.J.; Ramseier, R.O.

1978-01-01

The time variation of the sea-ice concentration and multiyear ice fraction within the pack ice in the Arctic Basin is examined, using microwave images of sea ice recently acquired by the Nimbus-5 spacecraft and the NASA CV-990 airborne laboratory. The images used for these studies were constructed from data acquired from the Electrically Scanned Microwave Radiometer (ESMR) which records radiation from earth and its atmosphere at a wavelength of 1.55 cm. Data are analyzed for four seasons during 1973-1975 to illustrate some basic differences in the properties of the sea ice during those times. Spacecraft data are compared with corresponding NASA CV-990 airborne laboratory data obtained over wide areas in the Arctic Basin during the Main Arctic Ice Dynamics Joint Experiment (1975) to illustrate the applicability of passive-microwave remote sensing for monitoring the time dependence of sea-ice concentration (divergence). These observations indicate significant variations in the sea-ice concentration in the spring, late fall and early winter. In addition, deep in the interior of the Arctic polar sea-ice pack, heretofore unobserved large areas, several hundred kilometers in extent, of sea-ice concentrations as low as 50% are indicated. ?? 1978 D. Reidel Publishing Company.

Structure and stability of pyrophyllite edge surfaces: Effect of temperature and water chemical potential

NASA Astrophysics Data System (ADS)

Kwon, Kideok D.; Newton, Aric G.

2016-10-01

The surfaces of clay minerals, which are abundant in atmospheric mineral dust, serve as an important medium to catalyze ice nucleation. The lateral edge surface of 2:1 clay minerals is postulated to be a potential site for ice nucleation. However, experimental investigations of the edge surface structure itself have been limited compared to the basal planes of clay minerals. Density functional theory (DFT) computational studies have provided insights into the pyrophyllite edge surface. Pyrophyllite is an ideal surrogate mineral for the edge surfaces of 2:1 clay minerals as it possesses no or little structural charge. Of the two most-common hydrated edge surfaces, the AC edge, (1 1 0) surface in the monoclinic polytype notation, is predicted to be more stable than the B edge, (0 1 0) surface. These stabilities, however, were determined based on the total energies calculated at 0 K and did not consider environmental effects such as temperature and humidity. In this study, atomistic thermodynamics based on periodic DFT electronic calculations was applied to examine the effects of environmental variables on the structure and thermodynamic stability of the common edge surfaces in equilibrium with bulk pyrophyllite and water vapor. We demonstrate that the temperature-dependent vibrational energy of sorbed water molecules at the edge surface is a significant component of the surface free energy and cannot be neglected when determining the surface stability of pyrophyllite. The surface free energies were calculated as a function of temperature from 240 to 600 K and water chemical potential corresponding to conditions from ultrahigh vacuum to the saturation vapor pressure of water. We show that at lower water chemical potentials (dry conditions), the AC and B edge surfaces possessed similar stabilities; at higher chemical potentials (humid conditions) the AC edge surface was more stable than the B edge surface. At high temperatures, both surfaces showed similar stabilities regardless of the water chemical potential. The equilibrium morphology of pyrophyllite crystals is also expected to be dependent on these two environmental variables. Surface defects may impact the surface reactivity. We discuss the thermodynamic stability of a possible Si cation vacancy defect which provides additional hydroxyl group on the surface.

Alaskan Ice Core Shows Relationship Between Asian Dust Storm And The Stratosphere Troposphere Exchange

NASA Astrophysics Data System (ADS)

Yasunari, T. J.; Shiraiwa, T.; Kanamori, S.; Fujii, Y.; Igarashi, M.; Yamazaki, K.; Benson, C. S.; Hondoh, T.

2005-12-01

Atmospheric dust absorbs and scatters solar radiation, and affects global radiative balance. Dust storm in arid and semi-arid regions in East Asia is main dust source in the northern hemisphere. Asian dust has large effect on radiative balance in the northern hemisphere and its long range transport to Alaskan region frequently occurs in springtime. On the other hand, the stratosphere-troposphere exchange (STE) is a important phenomenon for material exchange among the spheres. Some parameters such as tritium, ozone and beryllium can be transferred from the stratosphere into the troposphere under some conditions such as tropopause folding outbreaks, cut-off low developing and cyclonic activities. STE has a seasonal exchange with maximum in springtime. In June 2003, a 50m ice core was drilled at the summit of Mount Wrangell volcano (60N, 144W, 4100 m), Alaska. Dust particle concentration, tritium content and ratio of stable hydrogen isotope were analyzed. Tritium is the stratospheric tracer recently because the effect of nuclear tests in 1960s has faded these days, and its concentration is highest north of 30th parallel. Therefore, the ice core drilled here is ideal to assess both the Asian dust transport and STE. The core covers 1992-2002 with divided four seasons (winter, spring, late-spring and summer). Fine dust less than one micro meter generally represents long range transport increased in springtime every year. The drastic fine and coarse dust flux increases after 2000 correspond to recent increase of Asian Dust outbreaks. These indicate that Asian dust storm largely affects Mount Wrangell every year. Here we show the fact that highest positive correlation between tritium and fine dust fluxes was seen in the term from late-spring to summer (also high correlation between tritium and coarse dust fluxes in this term), suggesting that the stratosphere-troposphere exchange was most intensified by Asian dust storms in this transient season from spring to summer. Asian dust and STE are dominant in springtime. However, our results showed that these activities related each other the most from late-spring to summer. Asian dust storm and STE are not active in summer. Hence, our results are assumed to mainly reflect late-spring relationship between Asian dust storm and STE. Asian dust outbreaks with severe weather would impact on vertical and horizontal material circulation from the stratosphere to the troposphere. Further studies for Asian dust and STE especially focused on late-spring may lead to elucidate the mechanism of material circulation and assess the radiative forcing of Asian dust in springtime.

Modeling experiments on the deceleration and reactivation of Kangerlussuup Sermusa, West Greenland

NASA Astrophysics Data System (ADS)

Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.; Catania, G. A.

2015-12-01

Seasonal variations in outlet glacier velocity due to basal sliding are well-documented and typically involve acceleration early in the melt season due to enhanced sliding as a result of inefficient drainage of surface water reaching the bed. However, velocity observations from Kangerlussuup Sermusa (KS) in West Greenland contradict this pattern. Instead, ice velocity at KS shows no significant change in early spring compared with the previous winter. This sluggish response of the glacier to spring melt is often followed by an extreme, and short-lived, deceleration. For example, in August 2010, the lower 20 km of the trunk decelerated from about 1600 m a-1 to less than 250 m a-1; this event was followed by a rapid reactivation back to the previous velocity in less than 60 days. Available records since 2006 show that the sequence of steady spring velocity, followed by summer deceleration, and rapid fall reactivation occurs annually; however, the magnitudes of deceleration vary. In this regard, the response of KS to regional environmental forcings is unique compared to its neighboring glaciers. In this study, we investigate whether the unique behavior of KS can be explained by the interaction between changes in basal conditions and the local geometry of the glacier. We model the glacier flow by solving full-Stokes equations using the finite element method in the open-source FEniCS framework. Assuming isothermal ice within the lower trunk, we run experiments on the mechanical properties and boundary conditions of the glacier. These experiments include spatio-temporal changes in basal slipperiness, periodic melt-water influx to the bed, and ice viscosity variations due to changes in melt-water supply to the bed. We also conduct sensitivity analyses on the glacier flow with different ice geometries (e.g. thickness and surface slope) to investigate conditions under which we can produce the unique seasonal behavior of KS. Finally, we assess the impact of the combination of these parameters on the ice flow and evaluate the credibility of our hypothetical scenarios based on available measurements.

Near-Record Early Snowmelt and Signs of Environmental Change in Barrow, Alaska

NASA Astrophysics Data System (ADS)

Stanitski, D.; Cox, C.; Sweeney, C.; Divoky, G.; George, C.; Stone, R.

2015-12-01

The 2015 spring transition in Barrow, AK, was notable with the second earliest date of snow melt on record (JD148, May 28) and earliest ice free conditions on a local lagoon (JD178, June 27). The 73-year time series from the NOAA Global Monitoring Division's Barrow Observatory (BRW) has shown a trend toward earlier spring snowmelt, reinforced in 2015. Anomalous early snowmelt was also observed at nearby Cooper Island where a colony of sea birds, the Black Guillemot, nests each year once snow disappears. The appearance of "first egg" is well correlated with the date of snowmelt at BRW (Fig. 1), as is the ice-out date at the Isaktoak Lagoon (ISK). In 2015, the first egg was observed on JD159 (June 8), the earliest in the 40-year record (source: Friends of Cooper Island, http://cooperisland.org/). Each day of advance in the melt date at BRW results in an annual net radiation increase at the surface of about 1%. The documented changes can influence biogeochemical cycles, permafrost temperatures, and potentially the release of stored carbon. By mid July 2015, a 1°C increase in soil temperature at 0.5-m depth was measured compared to prior years; therefore, the active layer is expected to be unusually deep by autumn. The anomalous warmth that prevailed during spring 2015 can be attributed, in part, to atmospheric circulation, influenced by two typhoons in the North Pacific and the onset of El Niño. Warming was likely amplified locally as the early melting of snow increased absorption of solar radiation. Key factors influencing the trend toward earlier spring snowmelt will be presented as well as those contributing to the anomalous 2015 spring at BRW (e.g., winter snowfall, cloud cover, advection, local sea ice extent), and the impact early melt had on the 2015 summer surface radiation budget. Analysis of interactions underlying this anomaly will aid in developing strategies for improving predictability of interannual variability of the melt season and long-term change.

An Arctic Ice/Ocean Coupled Model with Wave Interactions

DTIC Science & Technology

2013-09-30

motion in the presence of currents and waves. In the wave attenuation experiments, between 35 and 80 ‘ice floes’ (0.99 m diameter wooden disks) were...moored with springs to the tank floor and plane waves were sent down, with an array of wave probes to measure the reflected and transmitted waves...waves propagating in the MIZ as opposed to the acoustic wave solution shown. This outcome offers significant new capabilities for tracking fully

Seasonal Forcing of Summer Dissolved Inorganic Carbon and Chlorophyll a on the Western Shelf of the Antarctic Peninsula

DTIC Science & Technology

2010-03-30

Click Here for Full Article Seasonal forcing of summer dissolved inorganic carbon and chlorophyll a on the western shelf of the Antarctic Peninsula... season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of these wind...Stammerjohn, and O. Schofield (2010), Seasonal forcing of summer dissolved inorganic carbon and chlorophyll a on the western shelf of the Antarctic

Microwave signatures of snow and fresh water ice

NASA Technical Reports Server (NTRS)

Schmugge, T.; Wilheit, T. T.; Gloersen, P.; Meier, M. F.; Frank, D.; Dirmhirn, I.

1973-01-01

During March of 1971, the NASA Convair 990 Airborne Observatory carrying microwave radiometers in the wavelength range 0.8 to 21 cm was flown over dry snow with different substrata: Lake ice at Bear Lake in Utah; wet soil in the Yampa River Valley near Steamboat Springs, Colorado; and glacier ice, firm and wet snow on the South Cascade Glacier in Washington. The data presented indicate that the transparency of the snow cover is a function of wavelength. False-color images of microwave brightness temperatures obtained from a scanning radiometer operating at a wavelength of 1.55 cm demonstrate the capability of scanning radiometers for mapping snowfields.

The nitrogen cycles on Pluto over seasonal and astronomical timescales

NASA Astrophysics Data System (ADS)

Bertrand, T.; Forget, F.; Umurhan, O. M.; Grundy, W. M.; Schmitt, B.; Protopapa, S.; Zangari, A. M.; White, O. L.; Schenk, P. M.; Singer, K. N.; Stern, A.; Weaver, H. A.; Young, L. A.; Ennico, K.; Olkin, C. B.

2018-07-01

Pluto's landscape is shaped by the endless condensation and sublimation cycles of the volatile ices covering its surface. In particular, the Sputnik Planitia ice sheet, which is thought to be the main reservoir of nitrogen ice, displays a large diversity of terrains, with bright and dark plains, small pits and troughs, topographic depressions and evidences of recent and past glacial flows. Outside Sputnik Planitia, New Horizons also revealed numerous nitrogen ice deposits, in the eastern side of Tombaugh Regio and at mid-northern latitudes. These observations suggest a complex history involving volatile and glacial processes occurring on different timescales. We present numerical simulations of volatile transport on Pluto performed with a model designed to simulate the nitrogen cycle over millions of years, taking into account the changes of obliquity, solar longitude of perihelion and eccentricity as experienced by Pluto. Using this model, we first explore how the volatile and glacial activity of nitrogen within Sputnik Planitia has been impacted by the diurnal, seasonal and astronomical cycles of Pluto. Results show that the obliquity dominates the N2 cycle and that over one obliquity cycle, the latitudes of Sputnik Planitia between 25°S-30°N are dominated by N2 condensation, while the northern regions between 30°N and -50°N are dominated by N2 sublimation. We find that a net amount of 1 km of ice has sublimed at the northern edge of Sputnik Planitia during the last 2 millions of years. It must have been compensated by a viscous flow of the thick ice sheet. By comparing these results with the observed geology of Sputnik Planitia, we can relate the formation of the small pits and the brightness of the ice at the center of Sputnik Planitia to the sublimation and condensation of ice occurring at the annual timescale, while the glacial flows at its eastern edge and the erosion of the water ice mountains all around the ice sheet are instead related to the astronomical timescale. We also perform simulations including a glacial flow scheme which shows that the Sputnik Planitia ice sheet is currently at its minimum extent at the northern and southern edges. We also explore the stability of N2 ice deposits outside the latitudes and longitudes of the Sputnik Planitia basin. Results show that N2 ice is not stable at the poles but rather in the equatorial regions, in particular in depressions, where thick deposits may persist over tens of millions of years, before being trapped in Sputnik Planitia. Finally, another key result is that the minimum and maximum surface pressures obtained over the simulated millions of years remain in the range of milli-Pascals and Pascals, respectively. This suggests that Pluto never encountered conditions allowing liquid nitrogen to flow directly on its surface. Instead, we suggest that the numerous geomorphological evidences of past liquid flow observed on Pluto's surface are the result of liquid nitrogen that flowed at the base of thick ancient nitrogen glaciers, which have since disappeared.

Evaluation and Validation of the Messinger Freezing Fraction

NASA Technical Reports Server (NTRS)

Anderson, David N.; Tsao, Jen-Ching

2005-01-01

One of the most important non-dimensional parameters used in ice-accretion modeling and scaling studies is the freezing fraction defined by the heat-balance analysis of Messinger. For fifty years this parameter has been used to indicate how rapidly freezing takes place when super-cooled water strikes a solid body. The value ranges from 0 (no freezing) to 1 (water freezes immediately on impact), and the magnitude has been shown to play a major role in determining the physical appearance of the accreted ice. Because of its importance to ice shape, this parameter and the physics underlying the expressions used to calculate it have been questioned from time to time. Until now, there has been no strong evidence either validating or casting doubt on the current expressions. This paper presents experimental measurements of the leading-edge thickness of a number of ice shapes for a variety of test conditions with nominal freezing fractions from 0.3 to 1.0. From these thickness measurements, experimental freezing fractions were calculated and compared with values found from the Messinger analysis as applied by Ruff. Within the experimental uncertainty of measuring the leading-edge thickness, agreement of the experimental and analytical freezing fraction was very good. It is also shown that values of analytical freezing fraction were entirely consistent with observed ice shapes at and near rime conditions: At an analytical freezing fraction of unity, experimental ice shapes displayed the classic rime shape, while for conditions producing analytical freezing fractions slightly lower than unity, glaze features started to appear.

Predictions of vertical uplift caused by changing polar ice volumes on a viscoelastic earth

NASA Technical Reports Server (NTRS)

Wahr, John; Dazhong, Han; Trupin, Andrew

1995-01-01

Measurements of crustal uplift from bedrock around the edges of Antarctica or Greenland could help constrain the mass balance of those ice caps. Present-day changes in ice could cause vertical displacement rates of several mm/yr around Antarctica and up to 10-15 mm/yr around Greenland. Horizontal displacement rates are likely to be about 1/3 the vertical rates. The viscoelastic response of the earth to past changes in ice could cause uplift rates that are several times larger. By measuring both gravity and vertical displacements, it is possible to remove the viscoelastic effects, so that the observations can be used to constrain present-day thickness changes.

A Flight Investigation of Exhaust-heat De-icing

NASA Technical Reports Server (NTRS)

Jones, Alun R; Rodert, Lewis A

1940-01-01

The National Advisory Committee for Aeronautics conducted exhaust-heat de-icing tests in flight to provide data needed in the application of this method. The capacity to extract heat from the exhaust gas for de-icing purposes, the quantity of heat required, and other factors were examined. The results indicate that a wing-heating system employing a spanwise exhaust tube within the leading edge of the wing removed 30 to 35 percent of the heat from exhaust gas entering the wing. Data are given from which the heat required for ice prevention can be calculated. Sample calculations have been made on the basis of existing engine power/wing area ratios to show that sufficient heating can be obtained for ice protection on modern transportation airplanes, provided that uniform distribution of the heat can be secured.

Ice sculpture in the Martian outflow channels

NASA Technical Reports Server (NTRS)

Lucchitta, B. K.

1982-01-01

Viking Orbiter and terrestrial satellite images are examined at similar resolution to compare features of the Martian outflow channels with features produced by the movement of ice on earth, and many resemblances are found. These include the anastomoses, sinuosities, and U-shaped cross profiles of valleys; hanging valleys; linear scour marks on valley walls; grooves and ridges on valley floors; and the streamlining of bedrock highs. Attention is given to the question whether ice could have moved in the Martian environment. It is envisaged that springs or small catastrophic outbursts discharged fluids from structural outlets or chaotic terrains. These fluids built icings that may have grown into substantial masses and eventually flowed like glaciers down preexisting valleys. An alternative is that the fluids formed rivers or floods that in turn formed ice jams and consolidated into icy masses in places where obstacles blocked their flow.

Progression of the 2011-2012 Surge of Bering Glacier and Bagley Ice Field, Alaska

NASA Astrophysics Data System (ADS)

Herzfeld, U. C.; McDonald, B.; Stachura, M.; Hale, R.; Trantow, T.; Weltman, A.; Chen, P.

2012-12-01

Bering Glacier, Alaska, started a surge in late spring 2011. The surge reached the ice front in May 2011 and extended into Bagley Ice Field by summer 2011. New surge-related crevassing was observed in July 2012. We collected aerial observations, including systematic videographic and photographic imagery, GPS data and laser altimeter data in September 2011 and in July 2012. In this talk, an analysis of surge progression and comparison to the early, mature and late stages of the 1993-1995 surge of Bering Glacier and Bagley Ice Field will be presented. A suite of approaches will be used to this end: Analysis of elevation changes based on CryoSat data, 2009 and 2010 IceBridge data and 2011 and 2012 laser altimeter data collected by our group, geostatistical classification of crevasse types based on imagery, classification of laser altimeter data and analysis of high-resolution satellite imagery (Worldview and GEOS).

EBSD in Antarctic and Greenland Ice

NASA Astrophysics Data System (ADS)

Weikusat, Ilka; Kuiper, Ernst-Jan; Pennock, Gill; Sepp, Kipfstuhl; Drury, Martyn

2017-04-01

Ice, particularly the extensive amounts found in the polar ice sheets, impacts directly on the global climate by changing the albedo and indirectly by supplying an enormous water reservoir that affects sea level change. The discharge of material into the oceans is partly controlled by the melt excess over snow accumulation, partly by the dynamic flow of ice. In addition to sliding over bedrock, an ice body deforms gravitationally under its own weight. In order to improve our description of this flow, ice microstructure studies are needed that elucidate the dominant deformation and recrystallization mechanisms involved. Deformation of hexagonal ice is highly anisotropic: ice is easily sheared in the basal plane and is about two orders of magnitude harder parallel to the c-axis. As dislocation creep is the dominant deformation mechanism in polar ice this strong anisotropy needs to be understood in terms of dislocation activity. The high anisotropy of the ice crystal is usually ascribed to a particular behaviour of dislocations in ice, namely the extension of dislocations into partials on the basal plane. Analysis of EBSD data can help our understanding of dislocation activity by characterizing subgrain boundary types thus providing a tool for comprehensive dislocation characterization in polar ice. Cryo-EBSD microstructure in combination with light microscopy measurements from ice core material from Antarctica (EPICA-DML deep ice core) and Greenland (NEEM deep ice core) are presented and interpreted regarding substructure identification and characterization. We examined one depth for each ice core (EDML: 656 m, NEEM: 719 m) to obtain the first comparison of slip system activity from the two ice sheets. The subgrain boundary to grain boundary threshold misorientation was taken to be 3-5° (Weikusat et al. 2011). EBSD analyses suggest that a large portion of edge dislocations with slip systems basal gliding on the basal plane were indeed involved in forming subgrain boundaries. However, an almost equal number of tilt subgrain boundaries were measured, involving dislocations gliding on non-basal planes (prism or prism slip). A few subgrain boundaries involving prism edge dislocation glide, as well as boundaries involving basal twist dislocation slip, were also identified. The finding that subgrain boundaries built up by dislocations gliding on non-basal planes are as frequent as those originating from basal plane slip is surprising and has impact on the discussion on rate-controlling processes for the ice flow descriptions of large ice masses with respect to sea-level evolution. Weikusat, I.; Miyamoto, A.; Faria, S. H.; Kipfstuhl, S.; Azuma, N. & Hondoh, T.: Subgrain boundaries in Antarctic ice quantified by X-ray Laue diffraction J. Glaciol., 2011, 57, 85-94

Estimating Spring Condensation on the Great Lakes

NASA Astrophysics Data System (ADS)

Meyer, A.; Welp, L.

2017-12-01

The Laurentian Great Lakes region provides opportunities for shipping, recreation, and consumptive water use to a large part of the United States and Canada. Water levels in the lakes fluctuate yearly, but attempts to model the system are inadequate because the water and energy budgets are still not fully understood. For example, water levels in the Great Lakes experienced a 15-year low period ending in 2013, the recovery of which has been attributed partially to decreased evaporation and increased precipitation and runoff. Unlike precipitation, the exchange of water vapor between the lake and the atmosphere through evaporation or condensation is difficult to measure directly. However, estimates have been constructed using off-shore eddy covariance direct measurements of latent heat fluxes, remote sensing observations, and a small network of monitoring buoys. When the lake surface temperature is colder than air temperature as it is in spring, condensation is larger than evaporation. This is a relatively small component of the net annual water budget of the lakes, but the total amount of condensation may be important for seasonal energy fluxes and atmospheric deposition of pollutants and nutrients to the lakes. Seasonal energy fluxes determine, and are influenced by, ice cover, water and air temperatures, and evaporation in the Great Lakes. We aim to quantify the amount of spring condensation on the Great Lakes using the National Center for Atmospheric Prediction North American Regional Reanalysis (NCEP NARR) Data for Winter 2013 to Spring 2017 and compare the condensation values of spring seasons following high volume, high duration and low volume, low duration ice cover.

FDC Mentor-Mentee Mixer Breaks the Ice Between Investigators and Trainees | Poster

Cancer.gov

The Frederick Diversity Committee’s mentor-mentee mixer gave research trainees, senior investigators, scientists, and administrative staff a chance to meet and mingle over refreshments and games following the Spring Research Festival.

Phoenix Lander Amid Disappearing Spring Ice

NASA Image and Video Library

2010-01-11

NASA Phoenix Mars Lander, its backshell and heatshield visible within this enhanced-color image of the Phoenix landing site taken on Jan. 6, 2010 by the High Resolution Imaging Science Experiment HiRISE camera on NASA Mars Reconnaissance Orbiter.

The Landsat Image Mosaic of Antarctica (LIMA): A Cutting-Edge Way for Students and Teachers to Learn about Antarctica

ERIC Educational Resources Information Center

Campbell, Brian; Bindschadler, Robert

2009-01-01

By studying Antarctica via satellite and through ground-truthing research, we can learn where the ice is melting and why. The Landsat Image Mosaic of Antarctica (LIMA), a new and cutting-edge way for scientists, researchers, educators, students, and the public to look at Antarctica, supports this research and allows for unprecedented views of our…

Polar stratospheric clouds and ozone depletion

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Turco, Richard P.

1991-01-01

A review is presented of investigations into the correlation between the depletion of ozone and the formation of polar stratospheric clouds (PSCs). Satellite measurements from Nimbus 7 showed that over the years the depletion from austral spring to austral spring has generally worsened. Approximately 70 percent of the ozone above Antarctica, which equals about 3 percent of the earth's ozone, is lost during September and October. Various hypotheses for ozone depletion are discussed including the theory suggesting that chlorine compounds might be responsible for the ozone hole, whereby chlorine enters the atmosphere as a component of chlorofluorocarbons produced by humans. The three types of PSCs, nitric acid trihydrate, slowly cooling water-ice, and rapidly cooling water-ice clouds act as important components of the Antarctic ozone depletion. It is indicated that destruction of the ozone will be more severe each year for the next few decades, leading to a doubling in area of the Antarctic ozone hole.

Fault detection and diagnosis of diesel engine valve trains

NASA Astrophysics Data System (ADS)

Flett, Justin; Bone, Gary M.

2016-05-01

This paper presents the development of a fault detection and diagnosis (FDD) system for use with a diesel internal combustion engine (ICE) valve train. A novel feature is generated for each of the valve closing and combustion impacts. Deformed valve spring faults and abnormal valve clearance faults were seeded on a diesel engine instrumented with one accelerometer. Five classification methods were implemented experimentally and compared. The FDD system using the Naïve-Bayes classification method produced the best overall performance, with a lowest detection accuracy (DA) of 99.95% and a lowest classification accuracy (CA) of 99.95% for the spring faults occurring on individual valves. The lowest DA and CA values for multiple faults occurring simultaneously were 99.95% and 92.45%, respectively. The DA and CA results demonstrate the accuracy of our FDD system for diesel ICE valve train fault scenarios not previously addressed in the literature.

Notable increases in nutrient concentrations in a shallow lake during seasonal ice growth.

PubMed

Fang, Yang; Changyou, Li; Leppäranta, Matti; Xiaonghong, Shi; Shengnan, Zhao; Chengfu, Zhang

2016-12-01

Nutrients may be eliminated from ice when liquid water is freezing, resulting in enhanced concentrations in the unfrozen water. The nutrients diluted from the ice may contribute to accumulated concentrations in sediment during winter and an increased risk of algae blooms during the following spring and summer. The objective of this study was to evaluate the influence of ice cover on nitrogen (N) and phosphorus (P) concentrations in the water and sediment of a shallow lake, through an examination of Ulansuhai Lake, northern China, from the period of open water to ice season in 2011-2013. The N and P concentrations were between two and five times higher, and between two and eight times higher, than in unfrozen lakes, respectively. As the ice thickness grew, contents of total N and total P showed C-shaped profiles in the ice, and were lower in the middle layer and higher in the bottom and surface layers. Most of the nutrients were released from the ice to liquid water. The results confirm that ice can cause the nutrient concentrations in water and sediment during winter to increase dramatically, thereby significantly impacting on processes in the water environment of shallow lakes.

Quantification of ikaite in Antarctic sea ice

NASA Astrophysics Data System (ADS)

Fischer, M.; Thomas, D. N.; Krell, A.; Nehrke, G.; Göttlicher, J.; Norman, L.; Riaux-Gobin, C.; Dieckmann, G. S.

2012-02-01

Calcium carbonate precipitation in sea ice can increase pCO2 during precipitation in winter and decrease pCO2 during dissolution in spring. CaCO3 precipitation in sea ice is thought to potentially drive significant CO2 uptake by the ocean. However, little is known about the quantitative spatial and temporal distribution of CaCO3 within sea ice. This is the first quantitative study of hydrous calcium carbonate, as ikaite, in sea ice and discusses its potential significance for the carbon cycle in polar oceans. Ice cores and brine samples were collected from pack and land fast sea ice between September and December 2007 during an expedition in the East Antarctic and another off Terre Adélie, Antarctica. Samples were analysed for CaCO3, Salinity, DOC, DON, Phosphate, and total alkalinity. A relationship between the measured parameters and CaCO3 precipitation could not be observed. We found calcium carbonate, as ikaite, mostly in the top layer of sea ice with values up to 126 mg ikaite per liter melted sea ice. This potentially represents a contribution between 0.12 and 9 Tg C to the annual carbon flux in polar oceans. The horizontal distribution of ikaite in sea ice was heterogenous. We also found the precipitate in the snow on top of the sea ice.

Effects of an Arctic under-ice phytoplankton bloom on bio-optical properties of surface waters during the Norwegian Young Sea Ice Cruise (N-ICE2015)

NASA Astrophysics Data System (ADS)

Pavlov, A. K.; Granskog, M. A.; Hudson, S. R.; Taskjelle, T.; Kauko, H.; Hamre, B.; Assmy, P.; Mundy, C. J.; Nicolaus, M.; Kowalczuk, P.; Stedmon, C. A.; Fernandez Mendez, M.

2016-02-01

A thinner and younger Arctic sea-ice cover has led to an increase in solar light transmission into the surface ocean, especially during late spring and summer. A description of the seasonal evolution of polar surface water optical properties is essential, in order to understand how changes are affecting light availability for photosynthetic organisms and the surface ocean energy budget. The development of the bio-optical properties of Arctic surface waters under predominantly first-year sea ice in the southern Nansen Basin were studied from January to June 2015 during the Norwegian Young Sea Ice Cruise (N-ICE2015). Observations included inherent optical properties, absorption by colored dissolved organic matter and particles, as well as radiometric measurements. We documented a rapid transition from relatively clear and transparent waters in winter to turbid waters in late May and June. This transition was associated with a strong under-ice phytoplankton bloom detected first under the compact ice pack and then monitored during drift across the marginal ice zone. We discuss potential implications of underwater light availability for photosynthesis, heat redistribution in the upper ocean layer, and energy budget of the sea-ice - ocean system.

Ice tracking techniques, implementation, performance, and applications

NASA Technical Reports Server (NTRS)

Rothrock, D. A.; Carsey, F. D.; Curlander, J. C.; Holt, B.; Kwok, R.; Weeks, W. F.

1992-01-01

Present techniques of ice tracking make use both of cross-correlation and of edge tracking, the former being more successful in heavy pack ice, the latter being critical for the broken ice of the pack margins. Algorithms must assume some constraints on the spatial variations of displacements to eliminate fliers, but must avoid introducing any errors into the spatial statistics of the measured displacement field. We draw our illustrations from the implementation of an automated tracking system for kinematic analyses of ERS-1 and JERS-1 SAR imagery at the University of Alaska - the Alaska SAR Facility's Geophysical Processor System. Analyses of the ice kinematic data that might have some general interest to analysts of cloud-derived wind fields are the spatial structure of the fields, and the evaluation and variability of average deformation and its invariants: divergence, vorticity and shear. Many problems in sea ice dynamics and mechanics can be addressed with the kinematic data from SAR.

Multi-frequency SAR, SSM/I and AVHRR derived geophysical information of the marginal ice zone

NASA Technical Reports Server (NTRS)

Shuchman, R. A.; Onstott, R. G.; Wackerman, C. C.; Russel, C. A.; Sutherland, L. L.; Johannessen, O. M.; Johannessen, J. A.; Sandven, S.; Gloerson, P.

1991-01-01

A description is given of the fusion of synthetic aperture radar (SAR), special sensor microwave imager (SSM/I), and NOAA Advanced Very High Resolution Radiometer (AVHRR) data to study arctic processes. These data were collected during the SIZEX/CEAREX experiments that occurred in the Greenland Sea in March of 1989. Detailed comparisons between the SAR, AVHRR, and SSM/I indicated: (1) The ice edge position was in agreement to within 25 km, (2) The SSM/I SAR total ice concentration compared favorably, however, the SSM/I significantly underpredicted the multiyear fraction, (3) Combining high resolution SAR with SSM/I can potentially map open water and new ice features in the marginal ice zone (MIZ) which cannot be mapped by the single sensors, and (4) The combination of all three sensors provides accurate ice information as well as sea surface temperature and wind speeds.

Correlation Between Geometric Similarity of Ice Shapes and the Resulting Aerodynamic Performance Degradation: A Preliminary Investigation Using WIND

NASA Technical Reports Server (NTRS)

Wright, William B.; Chung, James

1999-01-01

Aerodynamic performance calculations were performed using WIND on ten experimental ice shapes and the corresponding ten ice shapes predicted by LEWICE 2.0. The resulting data for lift coefficient and drag coefficient are presented. The difference in aerodynamic results between the experimental ice shapes and the LEWICE ice shapes were compared to the quantitative difference in ice shape geometry presented in an earlier report. Correlations were generated to determine the geometric features which have the most effect on performance degradation. Results show that maximum lift and stall angle can be correlated to the upper horn angle and the leading edge minimum thickness. Drag coefficient can be correlated to the upper horn angle and the frequency-weighted average of the Fourier coefficients. Pitching moment correlated with the upper horn angle and to a much lesser extent to the upper and lower horn thicknesses.

Deformation, warming and softening of Greenland’s ice by refreezing meltwater

NASA Astrophysics Data System (ADS)

Bell, Robin E.; Tinto, Kirsteen; Das, Indrani; Wolovick, Michael; Chu, Winnie; Creyts, Timothy T.; Frearson, Nicholas; Abdi, Abdulhakim; Paden, John D.

2014-07-01

Meltwater beneath the large ice sheets can influence ice flow by lubrication at the base or by softening when meltwater refreezes to form relatively warm ice. Refreezing has produced large basal ice units in East Antarctica. Bubble-free basal ice units also outcrop at the edge of the Greenland ice sheet, but the extent of refreezing and its influence on Greenland’s ice flow dynamics are unknown. Here we demonstrate that refreezing of meltwater produces distinct basal ice units throughout northern Greenland with thicknesses of up to 1,100 m. We compare airborne gravity data with modelled gravity anomalies to show that these basal units are ice. Using radar data we determine the extent of the units, which significantly disrupt the overlying ice sheet stratigraphy. The units consist of refrozen basal water commonly surrounded by heavily deformed meteoric ice derived from snowfall. We map these units along the ice sheet margins where surface melt is the largest source of water, as well as in the interior where basal melting is the only source of water. Beneath Petermann Glacier, basal units coincide with the onset of fast flow and channels in the floating ice tongue. We suggest that refreezing of meltwater and the resulting deformation of the surrounding basal ice warms the Greenland ice sheet, modifying the temperature structure of the ice column and influencing ice flow and grounding line melting.

Ecology of southern ocean pack ice.

PubMed

Brierley, Andrew S; Thomas, David N

2002-01-01

Around Antarctica the annual five-fold growth and decay of sea ice is the most prominent physical process and has a profound impact on marine life there. In winter the pack ice canopy extends to cover almost 20 million square kilometres--some 8% of the southern hemisphere and an area larger than the Antarctic continent itself (13.2 million square kilometres)--and is one of the largest, most dynamic ecosystems on earth. Biological activity is associated with all physical components of the sea-ice system: the sea-ice surface; the internal sea-ice matrix and brine channel system; the underside of sea ice and the waters in the vicinity of sea ice that are modified by the presence of sea ice. Microbial and microalgal communities proliferate on and within sea ice and are grazed by a wide range of proto- and macrozooplankton that inhabit the sea ice in large concentrations. Grazing organisms also exploit biogenic material released from the sea ice at ice break-up or melt. Although rates of primary production in the underlying water column are often low because of shading by sea-ice cover, sea ice itself forms a substratum that provides standing stocks of bacteria, algae and grazers significantly higher than those in ice-free areas. Decay of sea ice in summer releases particulate and dissolved organic matter to the water column, playing a major role in biogeochemical cycling as well as seeding water column phytoplankton blooms. Numerous zooplankton species graze sea-ice algae, benefiting additionally because the overlying sea-ice ceiling provides a refuge from surface predators. Sea ice is an important nursery habitat for Antarctic krill, the pivotal species in the Southern Ocean marine ecosystem. Some deep-water fish migrate to shallow depths beneath sea ice to exploit the elevated concentrations of some zooplankton there. The increased secondary production associated with pack ice and the sea-ice edge is exploited by many higher predators, with seals, seabirds and whales aggregating there. As a result, much of the Southern Ocean pelagic whaling was concentrated at the edge of the marginal ice zone. The extent and duration of sea ice fluctuate periodically under the influence of global climatic phenomena including the El Niño Southern Oscillation. Life cycles of some associated species may reflect this periodicity. With evidence for climatic warming in some regions of Antarctica, there is concern that ecosystem change may be induced by changes in sea-ice extent. The relative abundance of krill and salps appears to change interannually with sea-ice extent, and in warm years, when salps proliferate, krill are scarce and dependent predators suffer severely. Further research on the Southern Ocean sea-ice system is required, not only to further our basic understanding of the ecology, but also to provide ecosystem managers with the information necessary for the development of strategies in response to short- and medium-term environmental changes in Antarctica. Technological advances are delivering new sampling platforms such as autonomous underwater vehicles that are improving vastly our ability to sample the Antarctic under sea-ice environment. Data from such platforms will enhance greatly our understanding of the globally important Southern Ocean sea-ice ecosystem.

Evolution of the Marginal Ice Zone: Adaptive Sampling with Autonomous Gliders

DTIC Science & Technology

2015-09-30

kinetic energy (ε). Gliders also sampled dissolved oxygen, optical backscatter ( chlorophyll and CDOM fluorescence) and multi-spectral downwelling...Fig. 2). In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become...Sections across the ice edge just prior to recovery, during freeze-up, reveal elevated chlorophyll fluorescence throughout the mixed layer (Fig. 4

Scaling Methods for Simulating Aircraft In-Flight Icing Encounters

NASA Technical Reports Server (NTRS)

Anderson, David N.; Ruff, Gary A.

1997-01-01

This paper discusses scaling methods which permit the use of subscale models in icing wind tunnels to simulate natural flight in icing. Natural icing conditions exist when air temperatures are below freezing but cloud water droplets are super-cooled liquid. Aircraft flying through such clouds are susceptible to the accretion of ice on the leading edges of unprotected components such as wings, tailplane and engine inlets. To establish the aerodynamic penalties of such ice accretion and to determine what parts need to be protected from ice accretion (by heating, for example), extensive flight and wind-tunnel testing is necessary for new aircraft and components. Testing in icing tunnels is less expensive than flight testing, is safer, and permits better control of the test conditions. However, because of limitations on both model size and operating conditions in wind tunnels, it is often necessary to perform tests with either size or test conditions scaled. This paper describes the theoretical background to the development of icing scaling methods, discusses four methods, and presents results of tests to validate them.

Implications of Surface Morphologies for the Distribution of Shallow Subsurface Ice in Arcadia Planitia, Mars

NASA Astrophysics Data System (ADS)

Williams, N. R.; Hibbard, S. M.; Golombek, M. P.

2017-12-01

The plains of Arcadia Planitia on Mars at 40°N and 200°E straddle the southern boundary of a latitude-dependent mantle (LDM) of shallow water-ice that holds key records for the planet's climate. Ice is not stable at mid-latitude surfaces today, but is expected to have precipitated in the past during different obliquities and climatic conditions with remnant excess ice preserved in the subsurface under a veneer of soil partially isolating it from the atmosphere. Previous work has documented evidence for substantial ice in Arcadia using gamma ray spectrometry; ground-penetrating radar reflections and dielectric constants; and surface morphologies of lobate debris aprons, expanded secondary craters, terraced craters, and surface polygons. New high-resolution orbital images have been acquired that resolve meter-scale ice-related morphologies. In particular, Arcadia exhibits widespread polygonal patterned ground created by cryoturbation, and large areas of crenulated "brain coral" terrain for which the sinuous troughs have already undergone sublimation while the sinuous ridges are still ice-rich. We examined over 200 High Resolution Imaging Science Experiment (HiRISE) 25 cm/pixel images that resolve these morphologies indicating a complex transition of progressive ice loss at the edge of the LDM. HiRISE coverage is sparse across Arcadia; however, 6 m/pixel Context Camera (CTX) image coverage is nearly complete and fills in the gaps for terrain units with distinct textures. We find that crenulated terrain is restricted to a narrow latitude band at 38°N-43°N. Isolated shallow pits also occur northward of 40°N, and in many cases interconnect to form crenulations as part of a transitional morphologic continuum. Polygonal surface morphologies are ubiquitous farther north, but become increasingly sparse and more degraded farther south. These pits, crenulations, and polygons are sensitive to ice at depths of centimeters to a few meters, which could be easily accessible for future in-situ resource utilization. The latitude band of 38°N-43°N where these fine-scale morphologies occur represents the southern edge of the LDM where significant remnant ice is stored in the shallow subsurface.

Validation of EOS Aqua AMSR Sea Ice Products for East Antarctica

NASA Technical Reports Server (NTRS)

Massom, Rob; Lytle, Vicky; Allison, Ian; Worby, Tony; Markus, Thorsten; Scambos, Ted; Haran, Terry; Enomoto, Hiro; Tateyama, Kazu; Pfaffling, Andi

2004-01-01

This paper presents results from AMSR-E validation activities during a collaborative international cruise onboard the RV Aurora Australis to the East Antarctic sea ice zone (64-65 deg.S, 110-120 deg.E) in the early Austral spring of 2003. The validation strategy entailed an IS-day survey of the statistical characteristics of sea ice and snowcover over a Lagrangian grid 100 x 50 km in size (demarcated by 9 drifting ice beacons) i.e. at a scale representative of Ah4SR pixels. Ice conditions ranged h m consolidated first-year ice to a large polynya offshore from Casey Base. Data sets collected include: snow depth and snow-ice interface temperatures on 24 (?) randomly-selected floes in grid cells within a 10 x 50 km area (using helicopters); detailed snow and ice measurements at 13 dedicated ice stations, one of which lasted for 4 days; time-series measurements of snow temperature and thickness at selected sites; 8 aerial photography and thermal-IR radiometer flights; other satellite products (SAR, AVHRR, MODIS, MISR, ASTER and Envisat MERIS); ice drift data; and ancillary meteorological (ship-based, meteorological buoys, twice-daily radiosondes). These data are applied to a validation of standard AMSR-E ice concentration, snowcover thickness and ice-temperature products. In addition, a validation is carried out of ice-surface skin temperature products h m the NOAA AVHRR and EOS MODIS datasets.

Large Scale Variability of Phytoplankton Blooms in the Arctic and Peripheral Seas: Relationships with Sea Ice, Temperature, Clouds, and Wind

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Cota, Glenn F.

2004-01-01

Spatially detailed satellite data of mean color, sea ice concentration, surface temperature, clouds, and wind have been analyzed to quantify and study the large scale regional and temporal variability of phytoplankton blooms in the Arctic and peripheral seas from 1998 to 2002. In the Arctic basin, phytoplankton chlorophyll displays a large symmetry with the Eastern Arctic having about fivefold higher concentrations than those of the Western Arctic. Large monthly and yearly variability is also observed in the peripheral seas with the largest blooms occurring in the Bering Sea, Sea of Okhotsk, and the Barents Sea during spring. There is large interannual and seasonal variability in biomass with average chlorophyll concentrations in 2002 and 2001 being higher than earlier years in spring and summer. The seasonality in the latitudinal distribution of blooms is also very different such that the North Atlantic is usually most expansive in spring while the North Pacific is more extensive in autumn. Environmental factors that influence phytoplankton growth were examined, and results show relatively high negative correlation with sea ice retreat and strong positive correlation with temperature in early spring. Plankton growth, as indicated by biomass accumulation, in the Arctic and subarctic increases up to a threshold surface temperature of about 276-277 degree K (3-4 degree C) beyond which the concentrations start to decrease suggesting an optimal temperature or nutrient depletion. The correlation with clouds is significant in some areas but negligible in other areas, while the correlations with wind speed and its components are generally weak. The effects of clouds and winds are less predictable with weekly climatologies because of unknown effects of averaging variable and intermittent physical forcing (e.g. over storm event scales with mixing and upwelling of nutrients) and the time scales of acclimation by the phytoplankton.

Late Weichselian ice-sheet dynamics and deglaciation history of the northern Svalbard margin

NASA Astrophysics Data System (ADS)

Fransner, O.; Noormets, R. R. N. N.; Flink, A.; Hogan, K.; Dowdeswell, J. A.; O'Regan, M.; Jakobsson, M.

2016-12-01

The glacial evolution of the northern Svalbard margin is poorly known compared with the western margin. Gravity cores, swath bathymetric, sub-bottom acoustic and 2D airgun data are used to investigate the Late Weichselian Svalbard-Barents Ice Sheet history on the northern Svalbard margin. Prograding sequences in Kvitøya and Albertini trough mouths (TMs) indicate ice streaming to the shelf edge multiple times during the Quaternary. While Kvitøya Trough has an associated trough-mouth fan (TMF), Albertini TM is cut back into the shelf edge. Down-faulted bedrock below Albertini TM suggests larger sediment accommodation space there, explaining the absence of a TMF. The bathymetry indicates that ice flow in Albertini Trough was sourced from Duvefjorden and Albertinibukta. Exposed crystalline bedrock likely kept the two ice flows separated before merging north of Karl XII-Øya. Subglacial landforms in Rijpfjorden and Duvefjorden indicate that both fjords accommodated northward-flowing ice streams during the LGM. The deeper fjord basin and higher elongation ratios of landforms in Duvefjorden suggest a more focused and/or larger ice flow there. Easily erodible sedimentary rocks are common in Duvefjorden, which may explain different ice flow dynamics in these fjords. Kvitøya TMF is flanked by gullies, probably formed through erosive downslope gravity flows triggered by sediment-laden meltwater during early deglaciation. Glacial landforms in Albertini Trough comprise retreat-related landforms indicating slow deglaciation. Iceberg scours in Albertini Trough suggest the importance of calving for mass-loss. Sets of De Geer moraines in Rijpfjorden imply that slow, grounded retreat continued in <210 m water depth. Lack of retreat-related landforms in deeper areas of Rijpfjorden and in Duvefjorden indicates floating glacier fronts influenced by calving. 14C ages suggest that deglaciation of inner Rijpfjorden and central Duvefjorden were complete before 10,434 cal a BP and 10,779 cal a BP respectively.

Efficient meltwater drainage through supraglacial streams and rivers on the southwest Greenland ice sheet.

PubMed

Smith, Laurence C; Chu, Vena W; Yang, Kang; Gleason, Colin J; Pitcher, Lincoln H; Rennermalm, Asa K; Legleiter, Carl J; Behar, Alberto E; Overstreet, Brandon T; Moustafa, Samiah E; Tedesco, Marco; Forster, Richard R; LeWinter, Adam L; Finnegan, David C; Sheng, Yongwei; Balog, James

2015-01-27

Thermally incised meltwater channels that flow each summer across melt-prone surfaces of the Greenland ice sheet have received little direct study. We use high-resolution WorldView-1/2 satellite mapping and in situ measurements to characterize supraglacial water storage, drainage pattern, and discharge across 6,812 km(2) of southwest Greenland in July 2012, after a record melt event. Efficient surface drainage was routed through 523 high-order stream/river channel networks, all of which terminated in moulins before reaching the ice edge. Low surface water storage (3.6 ± 0.9 cm), negligible impoundment by supraglacial lakes or topographic depressions, and high discharge to moulins (2.54-2.81 cm⋅d(-1)) indicate that the surface drainage system conveyed its own storage volume every <2 d to the bed. Moulin discharges mapped inside ∼52% of the source ice watershed for Isortoq, a major proglacial river, totaled ∼41-98% of observed proglacial discharge, highlighting the importance of supraglacial river drainage to true outflow from the ice edge. However, Isortoq discharges tended lower than runoff simulations from the Modèle Atmosphérique Régional (MAR) regional climate model (0.056-0.112 km(3)⋅d(-1) vs. ∼0.103 km(3)⋅d(-1)), and when integrated over the melt season, totaled just 37-75% of MAR, suggesting nontrivial subglacial water storage even in this melt-prone region of the ice sheet. We conclude that (i) the interior surface of the ice sheet can be efficiently drained under optimal conditions, (ii) that digital elevation models alone cannot fully describe supraglacial drainage and its connection to subglacial systems, and (iii) that predicting outflow from climate models alone, without recognition of subglacial processes, may overestimate true meltwater export from the ice sheet to the ocean.

Efficient meltwater drainage through supraglacial streams and rivers on the southwest Greenland ice sheet

PubMed Central

Smith, Laurence C.; Chu, Vena W.; Yang, Kang; Gleason, Colin J.; Pitcher, Lincoln H.; Rennermalm, Asa K.; Legleiter, Carl J.; Behar, Alberto E.; Overstreet, Brandon T.; Moustafa, Samiah E.; Tedesco, Marco; Forster, Richard R.; LeWinter, Adam L.; Finnegan, David C.; Sheng, Yongwei; Balog, James

2015-01-01

Thermally incised meltwater channels that flow each summer across melt-prone surfaces of the Greenland ice sheet have received little direct study. We use high-resolution WorldView-1/2 satellite mapping and in situ measurements to characterize supraglacial water storage, drainage pattern, and discharge across 6,812 km2 of southwest Greenland in July 2012, after a record melt event. Efficient surface drainage was routed through 523 high-order stream/river channel networks, all of which terminated in moulins before reaching the ice edge. Low surface water storage (3.6 ± 0.9 cm), negligible impoundment by supraglacial lakes or topographic depressions, and high discharge to moulins (2.54–2.81 cm⋅d−1) indicate that the surface drainage system conveyed its own storage volume every <2 d to the bed. Moulin discharges mapped inside ∼52% of the source ice watershed for Isortoq, a major proglacial river, totaled ∼41–98% of observed proglacial discharge, highlighting the importance of supraglacial river drainage to true outflow from the ice edge. However, Isortoq discharges tended lower than runoff simulations from the Modèle Atmosphérique Régional (MAR) regional climate model (0.056–0.112 km3⋅d−1 vs. ∼0.103 km3⋅d−1), and when integrated over the melt season, totaled just 37–75% of MAR, suggesting nontrivial subglacial water storage even in this melt-prone region of the ice sheet. We conclude that (i) the interior surface of the ice sheet can be efficiently drained under optimal conditions, (ii) that digital elevation models alone cannot fully describe supraglacial drainage and its connection to subglacial systems, and (iii) that predicting outflow from climate models alone, without recognition of subglacial processes, may overestimate true meltwater export from the ice sheet to the ocean. PMID:25583477

The characteristics of dissolved organic matter (DOM) and chromophoric dissolved organic matter (CDOM) in Antarctic sea ice

NASA Astrophysics Data System (ADS)

Norman, Louiza; Thomas, David N.; Stedmon, Colin A.; Granskog, Mats A.; Papadimitriou, Stathys; Krapp, Rupert H.; Meiners, Klaus M.; Lannuzel, Delphine; van der Merwe, Pier; Dieckmann, Gerhard S.

2011-05-01

An investigation of coloured dissolved organic matter (CDOM) and its relationships to physical and biogeochemical parameters in Antarctic sea ice and oceanic water have indicated that ice melt may both alter the spectral characteristics of CDOM in Antarctic surface waters and serve as a likely source of fresh autochthonous CDOM and labile DOC. Samples were collected from melted bulk sea ice, sea ice brines, surface gap layer waters, and seawater during three expeditions: one during the spring to summer and two during the winter to spring transition period. Variability in both physical (temperature and salinity) and biogeochemical parameters (dissolved and particulate organic carbon and nitrogen, as well as chlorophyll a) was observed during and between studies, but CDOM absorption coefficients measured at 375 nm (a 375) did not differ significantly. Distinct peaked absorption spectra were consistently observed for bulk ice, brine, and gap water, but were absent in the seawater samples. Correlation with the measured physical and biogeochemical parameters could not resolve the source of these peaks, but the shoulders and peaks observed between 260 and 280 nm and between 320 to 330 nm respectively, particularly in the samples taken from high light-exposed gap layer environment, suggest a possible link to aromatic and mycosporine-like amino acids. Sea ice CDOM susceptibility to photo-bleaching was demonstrated in an in situ 120 hour exposure, during which we observed a loss in CDOM absorption of 53% at 280 nm, 58% at 330 nm, and 30% at 375 nm. No overall coincidental loss of DOC or DON was measured during the experimental period. A relationship between the spectral slope (S) and carbon-specific absorption (a *375) indicated that the characteristics of CDOM can be described by the mixing of two broad end-members; and aged material, present in brine and seawater samples characterised by high S values and low a *375; and a fresh material, due to elevated in situ production, present in the bulk ice samples characterised by low S and high a *375. The DOC data reported here have been used to estimate that approximately 8 Tg C yr -1 (˜11% of annual sea ice algae primary production) may be exported to the surface ocean during seasonal sea ice melt in the form of DOC.

Links between ocean properties, ice cover, and plankton dynamics on interannual time scales in the Canadian Arctic Archipelago

NASA Astrophysics Data System (ADS)

Hamilton, James M.; Collins, Kate; Prinsenberg, Simon J.

2013-10-01

A decade of instrumented mooring data from Barrow Strait in the eastern Canadian Arctic Archipelago reveals connections between sea ice, water characteristics, and zooplankton dynamics on interannual time scales. On the North side of the Strait, the timing of breakup is positively related to the timing of freezeup in the previous year and negatively related to spring water temperature. This suggests that an early freezeup insulates the ocean from a cold autumn atmosphere, allowing heat to be retained until spring when it contributes to early sea ice erosion. There is also a very strong negative association between the timing of freezeup and late summer salinity, suggesting that monitoring of salinity in real time could be used to predict freezeup. A zooplankton biomass index derived from acoustic Doppler current profiler echo intensity data is used to demonstrate that on the North side there are also strong connections between early summer water temperature and the start, length, and productivity of the zooplankton growth season. On the South side of the Strait where currents are stronger, the relationships seen on the North side were not observed. But here integrated zooplankton biomass index and measured currents are used to identify interannual variability in the zooplankton biomass being delivered downstream into Lancaster Sound. Also on the South side, two yearlong records of daily fluorescence profiles reveal a large difference in the phytoplankton biomass being delivered downstream between years and demonstrate a strong relationship between the timing of the spring phytoplankton bloom and that of breakup.

Identification of contrasting seasonal sea ice conditions during the Younger Dryas

NASA Astrophysics Data System (ADS)

Cabedo-Sanz, P.; Belt, S. T.; Knies, J.

2012-12-01

The presence of the sea ice diatom biomarker IP25 in Arctic marine sediments has been used in previous studies as a proxy for past spring sea ice occurrence and as an indicator of wider palaeoenvironmental conditions for different regions of the Arctic over various timescales [e.g. 1, 2]. The current study focuses on high-resolution palaeo sea ice reconstructions for northern Norway during the last ca. 15 cal. kyr BP. Within this study, particular emphasis has been placed on the identification of the sea ice conditions during the Younger Dryas and the application of different biomarker-based proxies to both identify and quantify seasonal sea ice conditions. Firstly, the appearance of the specific sea ice diatom proxy IP25 at ca. 12.9 cal. kyr BP in a marine sediment core (JM99-1200) obtained from Andfjorden has provided an unambiguous but qualitative measure of seasonal sea ice and thus the onset of the Younger Dryas stadial. The near continuous occurrence of IP25 for the next ca. 1400 yr demonstrates seasonal sea ice during this interval, although variable abundances suggest that the recurrent conditions in the early-mid Younger Dryas (ca. 12.9 - 11.9 cal. kyr BP) changed significantly from stable to highly variable sea ice conditions at ca. 11.9 cal. kyr BP and this instability in sea ice prevailed for the subsequent ca. 400 yr. At ca. 11.5 cal. kyr BP, IP25 disappeared from the record indicating ice-free conditions that signified the beginning of the Holocene. Similarly, a high resolution record from the Kveithola Through, western Barents Sea, showed clearly higher IP25 concentrations during the Younger Dryas stadial compared to the Holocene. For both marine records, the IP25 concentrations were also combined with those of the open water phytoplankton biomarker brassicasterol to generate PBIP25 data from which more quantitative measurements of sea ice were determined. The contrasting seasonal sea ice conditions during the Younger Dryas were further verified through a comparison of the concentrations of IP25 with those of another highly branched isoprenoid (HBI) alkene that is di-unsaturated and believed to also be produced by sea ice diatoms. The ratio of the HBI diene to IP25, termed DIP25, is believed to provide a useful indicator of stability or variability in sea ice conditions and complements the outcomes from the IP25 and PBIP25 index data. 1. Belt, S.T., Vare, L.L., Massé, G., Manners, H.R., Price, J.C., MacLachlan, S.E., Andrews, J.T. , Schmidt, S., 2010. Striking similarities in temporal changes to spring sea ice occurrence across the central Canadian Arctic Archipelago over the last 7000 years. Quaternary Science Reviews 29, 3489-3504. 2. Müller, J., Massé, G., Stein, R., Belt, S.T., 2009. Variability of sea-ice conditions in the Fram Strait over the past 30,000 years. Nature Geoscience 2, 772-776.

Frontal destabilization of Stonebreen, Edgeøya, Svalbard

NASA Astrophysics Data System (ADS)

Strozzi, Tazio; Kääb, Andreas; Schellenberger, Thomas

2017-02-01

In consideration of the strong atmospheric warming that has been observed since the 1990s in polar regions there is a need to quantify mass loss of Arctic ice caps and glaciers and their contribution to sea level rise. In polar regions a large part of glacier ablation is through calving of tidewater glaciers driven by ice velocities and their variations. The Svalbard region is characterized by glaciers with rapid dynamic fluctuations of different types, including irreversible adjustments of calving fronts to a changing mass balance and reversible, surge-type activities. For large areas, however, we do not have much past and current information on glacier dynamic fluctuations. Recently, through frequent monitoring based on repeat optical and synthetic aperture radar (SAR) satellite data, a number of zones of velocity increases have been observed at formerly slow-flowing calving fronts on Svalbard. Here we present the dynamic evolution of the southern lobe of Stonebreen on Edgeøya. We observe a slowly steady retreat of the glacier front from 1971 until 2011, followed by a strong increase in ice surface velocity along with a decrease of volume and frontal extension since 2012. The considerable losses in ice thickness could have made the tide-water calving glacier, which is grounded below sea level some 6 km inland from the 2014 front, more sensitive to surface meltwater reaching its bed and/or warm ocean water increasing frontal ablation with subsequent strong multi-annual ice-flow acceleration.

Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present

PubMed Central

Hoff, Ulrike; Rasmussen, Tine L.; Stein, Ruediger; Ezat, Mohamed M.; Fahl, Kirsten

2016-01-01

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland–Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean. PMID:27456826

Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present.

PubMed

Hoff, Ulrike; Rasmussen, Tine L; Stein, Ruediger; Ezat, Mohamed M; Fahl, Kirsten

2016-07-26

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland-Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.

Sharing Remote and Local Information for Tracking Spring Breakup in the Mackenzie Delta and Beaufort Sea

NASA Astrophysics Data System (ADS)

Forbes, D. L.; Whalen, D.; Fraser, P.

2015-12-01

The Mackenzie Delta is the second largest on the Arctic Ocean, covering 13 000 km2. The annual flood regime in the delta is dominated by the spring snowmelt freshet and associated ice breakup, as water from the south arrives in the ice-covered delta and spreads over bottomfast and adjacent floating sea ice at the delta front. The complex processes of water-ice interaction, flow partitioning, and overbank flooding to replenish waters in 43 000 delta lakes threaten community, transportation, subsistence, and energy infrastructure in the delta. The annual breakup season is a time of rejuvenation, excitement, and anxiety for delta residents and stakeholders. To track the progress of breakup and meet the need for knowledge dissemination to the local communities, a Mackenzie-Beaufort breakup newsletter has been produced by Natural Resources Canada on a quasi-daily basis during the May-June spring flood season for 10 years, and distributed to an e-mail list that grew to over 300 subscribers. This provides near real-time tracking of water levels and breakup using on-line gauges (Environment Canada), daily MODIS satellite imagery (NASA), Landsat imagery (USGS) and intermittent radar imagery (various sources). In earlier years, information was also supplied from field programs operating in the delta during breakup, but changing priorities and funding have reduced the number of outside researchers present during these critical weeks. Meanwhile the number of local contributors has grown, providing observations and photographs to share with the local, regional and global readership. In this way the newsletter evolved into a two-way communication tool and community portal. The newsletter is a chronicle of each breakup season and a key resource for territorial and municipal managers, subsistence organizations, and emergency response agencies, with routine requests for specific imagery in areas of concern. With the completion of 10 years under the present model, we are exploring alternative approaches to enable more direct involvement in the region. The new model will be supported by the Circumpolar Coastal Communities Observatory Network (CACCON), Future Earth Coasts, and ArcticNet, and co-designed and co-managed with regional users to share timely information on the transformative event of each spring season in the delta.

CO2 (dry ice) cleaning system

NASA Technical Reports Server (NTRS)

Barnett, Donald M.

1995-01-01

Tomco Equipment Company has participated in the dry ice (solid carbon dioxide, CO2) cleaning industry for over ten years as a pioneer in the manufacturer of high density, dry ice cleaning pellet production equipment. For over four years Tomco high density pelletizers have been available to the dry ice cleaning industry. Approximately one year ago Tomco introduced the DI-250, a new dry ice blast unit making Tomco a single source supplier for sublimable media, particle blast, cleaning systems. This new blast unit is an all pneumatic, single discharge hose device. It meters the insertion of 1/8 inch diameter (or smaller), high density, dry ice pellets into a high pressure, propellant gas stream. The dry ice and propellant streams are controlled and mixed from the blast cabinet. From there the mixture is transported to the nozzle where the pellets are accelerated to an appropriate blasting velocity. When directed to impact upon a target area, these dry ice pellets have sufficient energy to effectively remove most surface coatings through dry, abrasive contact. The meta-stable, dry ice pellets used for CO2 cleaning, while labeled 'high density,' are less dense than alternate, abrasive, particle blast media. In addition, after contacting the target surface, they return to their equilibrium condition: a superheated gas state. Most currently used grit blasting media are silicon dioxide based, which possess a sharp tetrahedral molecular structure. Silicon dioxide crystal structures will always produce smaller sharp-edged replicas of the original crystal upon fracture. Larger, softer dry ice pellets do not share the same sharp-edged crystalline structures as their non-sublimable counterparts when broken. In fact, upon contact with the target surface, dry ice pellets will plastically deform and break apart. As such, dry ice cleaning is less harmful to sensitive substrates, workers and the environment than chemical or abrasive cleaning systems. Dry ice cleaning system components include: a dry ice pellet supply, a non-reactive propellant gas source, a pellet and propellant metering device, and a media transport and acceleration hose and nozzle arrangement. Dry ice cleaning system operating parameters include: choice of propellant gas, its pressure and temperature, dry ice mass flow rate, dry ice pellet size and shape, and acceleration nozzle configuration. These parameters may be modified to fit different applications. The growth of the dry ice cleaning industry will depend upon timely data acquisition of the effects that independent changes in these parameters have on cleaning rates, with respect to different surface coating and substrate combinations. With this data, optimization of cleaning rates for particular applications will be possible. The analysis of the applicable range of modulation of these parameters, within system component mechanical constraints, has just begun.

Demography and behavior of polar bears summering on land in Alaska

USGS Publications Warehouse

Peacock, Lily

2014-01-01

Polar bears (Ursus maritimus) in the southern Beaufort Sea population (SB) are spending increased time on the coastal North Slope of Alaska between July and October (Gleason and Rode 2010). The duration spent on land by polar bears, satellite collared on the sea-ice in the spring, during the summer and fall has also increased (USGS, unpublished data; Figure 1). This change in polar bear ecology has relevance for human-bear interactions, subsistence harvest, prevalence of defense kills, and disturbance associated with existing land-based development [e.g., National Petroleum Reserve of Alaska (NPRA), Arctic National Wildlife Refuge (ANWR)], Native Alaskan communities, recreation (ANWR) and tourism (e.g., bear viewing in Kaktovik, AK). These activities have the potential to impact, in new ways, the status of the entire SB population. Concomitantly, the change in polar bear ecology will impact these human activities, and a base-line characterization of this phenomenon can better inform mitigation (e.g., industry permitting under the Endangered Species Act and Marine Mammal Protection Act). In this study we aim to characterize the demography, habitat-use, and aspects of foraging ecology and health of polar bears spending fall on land. The SB population is characterized by a divergent-sea ice ecology, where polar bears typically spend most of the year on the sea-ice, even as the pack ice retreats northward, away from the coast, to its minimal extent in September (Amstrup et al. 2008; Durner et al. 2009). From 2000 – 2005, using coastal aerial surveys, Schliebe et al. (2008) observed between 3.7 and 8% of polar bears from SB (~ 60 – 120 of 1526, Regher et al. 2006) on land during the autumn. Sighting probability was not estimated in these surveys, and therefore the numbers represent minimum numbers of bears on land. Our analysis of USGS data suggest an annual average of 15% (± 3%, SE) of polar bears satellite-tagged on the spring-time sea ice (total n = 18 of 124 satellite tags, 2003 – 2009) come to land during July – October. Based on these data, and an assumption that bears satellite-tagged on the spring time sea ice are representative of the entire SB population of independent bears, there would be an average of 230 bears on land each fall. In contrast to the SB population, in five of the world’s 19 polar bear populations (Obbard et al. 2010), polar bears spend significant periods of time on land (1 – 5 months) when ice completely melts. In these seasonal-ice populations (Amstrup et al. 2008), polar bears are largely in a hypophagic condition (e.g., Hobson et al. 2009), relying on fat stores from the spring hyperphagic season, when ringed seals (Phoca hispida) pup. In general, these seasonal-ice populations are demographically productive (Taylor et al. 2005), although recently an increase in the ice-free season has resulted in a population decline in western Hudson Bay (Stirling et al. 1999; Regehr et al. 2007). There have been measured declines in the body condition and productivity of polar bears in SB, and changes in these parameters have been linked to declining optimal ice habitat (e.g., Durner et al. 2009; Regehr et al. 2010). We do not understand the relationship between land-use and the overall status of the population. Individual polar bears that use land may have increased or decreased fitness, in comparison to polar bears that remain on ice in the autumn. This project, which focuses on the biology of animals that spend time on-shore, will help address this question. This project is funded by the Bureau of Ocean Energy Management (BOEM) under Agreement No. M09PG00025 and the USGS Outer Continental Shelf Program (OCS) for FY 2009-2014. Parts of this study are also funded by US Fish and Wildlife Service, Office of Marine Mammals Management; the Bureau of Land Management; and the North Slope Borough, Department of Wildlife Management. This report is comprehensive, describing results for achieving the overlap

Estimation of degree of sea ice ridging based on dual-polarized C-band SAR data

NASA Astrophysics Data System (ADS)

Gegiuc, Alexandru; Similä, Markku; Karvonen, Juha; Lensu, Mikko; Mäkynen, Marko; Vainio, Jouni

2018-01-01

For ship navigation in the Baltic Sea ice, parameters such as ice edge, ice concentration, ice thickness and degree of ridging are usually reported daily in manually prepared ice charts. These charts provide icebreakers with essential information for route optimization and fuel calculations. However, manual ice charting requires long analysis times, and detailed analysis of large areas (e.g. Arctic Ocean) is not feasible. Here, we propose a method for automatic estimation of the degree of ice ridging in the Baltic Sea region, based on RADARSAT-2 C-band dual-polarized (HH/HV channels) SAR texture features and sea ice concentration information extracted from Finnish ice charts. The SAR images were first segmented and then several texture features were extracted for each segment. Using the random forest method, we classified them into four classes of ridging intensity and compared them to the reference data extracted from the digitized ice charts. The overall agreement between the ice-chart-based degree of ice ridging and the automated results varied monthly, being 83, 63 and 81 % in January, February and March 2013, respectively. The correspondence between the degree of ice ridging reported in the ice charts and the actual ridge density was validated with data collected during a field campaign in March 2011. In principle the method can be applied to the seasonal sea ice regime in the Arctic Ocean.

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.

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

PubMed Central

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

2017-01-01

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

Icy Layers in Craters

NASA Image and Video Library

2018-02-20

In this image from NASA's Mars Reconnaissance Rover (MRO) we can see the edge of a mound of ice in one of these mid-latitude craters. Some of it has already been removed, so we can see layering that used to be in the crater's interior. Scientists use ice deposits like these to figure out how the climate has changed on Mars. Another upside of recognizing this ice is that future astronauts will have plenty of drinking water. Scientists now realize that ice is very common on the Martian surface. It often fills up craters and valleys in the mid-latitudes in older climates, although when it's covered in dust it can be hard to recognize. Today the climate on Mars makes this ice unstable and some of it has evaporated away. https://photojournal.jpl.nasa.gov/catalog/PIA22255

Multiple-layer printed-wiring trace connector

NASA Technical Reports Server (NTRS)

Pizzeck, D. E.

1977-01-01

Nickel-plated spring-steel foil connector is hollow pin, with lengthwise slit, that is inserted into improperly plated-through holes. Edges of connector make positive contact with copper pads within hole.

Modulation of Sea Ice Melt Onset and Retreat in the Laptev Sea by the Timing of Snow Retreat in the West Siberian Plain

NASA Astrophysics Data System (ADS)

Crawford, A. D.; Stroeve, J.; Serreze, M. C.; Rajagopalan, B.; Horvath, S.

2017-12-01

As much of the Arctic Ocean transitions to ice-free conditions in summer, efforts have increased to improve seasonal forecasts of not only sea ice extent, but also the timing of melt onset and retreat. This research investigates the potential of regional terrestrial snow retreat in spring as a predictor for subsequent sea ice melt onset and retreat in Arctic seas. One pathway involves earlier snow retreat enhancing atmospheric moisture content, which increases downwelling longwave radiation over sea ice cover downstream. Another pathway involves manipulation of jet stream behavior, which may affect the sea ice pack via both dynamic and thermodynamic processes. Although several possible connections between snow and sea ice regions are identified using a mutual information criterion, the physical mechanisms linking snow retreat and sea ice phenology are most clearly exemplified by variability of snow retreat in the West Siberian Plain impacting melt onset and sea ice retreat in the Laptev Sea. The detrended time series of snow retreat in the West Siberian Plain explains 26% of the detrended variance in Laptev Sea melt onset (29% for sea ice retreat). With modest predictive skill and an average time lag of 53 (88) days between snow retreat and sea ice melt onset (retreat), West Siberian Plains snow retreat is useful for refining seasonal sea ice predictions in the Laptev Sea.

A Design Method for Topologically Insulating Metamaterials

NASA Astrophysics Data System (ADS)

Matlack, Kathryn; Serra-Garcia, Marc; Palermo, Antonio; Huber, Sebastian; Daraio, Chiara

Topological insulators are a unique class of electronic materials that exhibit protected edge states that are insulating in the bulk, and immune to back-scattering and defects. Discrete models, such as mass-spring systems, provide a means to translate these properties, based on the quantum hall spin effect, to the mechanical domain. This talk will present how to engineer a 2D mechanical metamaterial that supports topologically-protected and defect-immune edge states, directly from the mass-spring model of a topological insulator. The design method uses combinatorial searches plus gradient-based optimizations to determine the configuration of the metamaterials building blocks that leads to the global behavior specified by the target mass-spring model. We use metamaterials with weakly coupled unit cells to isolate the dynamics within our frequency range of interest and to enable a systematic design process. This approach can generally be applied to implement behaviors of a discrete model directly in mechanical, acoustic, or photonic metamaterials within the weak-coupling regime. This work was partially supported by the ETH Postdoctoral Fellowship, and by the Swiss National Science Foundation.

Travertine Hot Springs, Mono County, California

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

Chesterman, C.W.; Kleinhampl, F.J.

1991-08-01

This article is an abridgement of Special Report 172, Travertine Hot Springs at Bridgeport, Mono County, California, in preparation at the California Division of Mines and Geology. The Travertine Hot Springs area is on the northern edge of what many consider to be one of the most tectonically active areas in the United States. There is abundant geothermal and seismic activity. The landscape is dotted with volcanic features- cones, craters, domes, flows, fumaroles and hot springs-indicators of unrest in the present as well as reminders of activity in the past. Travertine, also known as calcareous sinter, is limestone formed bymore » chemical precipitation of calcium carbonate (CaCO{sub 3}) from ground or surface waters. It forms stalactites and stalagmites in caves, fills some veins and spring conduits and can also be found at the mouths of springs, especially hot springs. The less compact variety is called tufa and the dense, banded variety is known as Mexican onyx, or onyx marble. True onyx, however, is a banded silicate.« less

Seasonal Study of Mercury Species in the Antarctic Sea Ice Environment.

PubMed

Nerentorp Mastromonaco, Michelle G; Gårdfeldt, Katarina; Langer, Sarka; Dommergue, Aurélien

2016-12-06

Limited studies have been conducted on mercury concentrations in the polar cryosphere and the factors affecting the distribution of mercury within sea ice and snow are poorly understood. Here we present the first comprehensive seasonal study of elemental and total mercury concentrations in the Antarctic sea ice environment covering data from measurements in air, sea ice, seawater, snow, frost flowers, and brine. The average concentration of total mercury in sea ice decreased from winter (9.7 ng L -1 ) to spring (4.7 ng L -1 ) while the average elemental mercury concentration increased from winter (0.07 ng L -1 ) to summer (0.105 ng L -1 ). The opposite trends suggest potential photo- or dark oxidation/reduction processes within the ice and an eventual loss of mercury via brine drainage or gas evasion of elemental mercury. Our results indicate a seasonal variation of mercury species in the polar sea ice environment probably due to varying factors such as solar radiation, temperature, brine volume, and atmospheric deposition. This study shows that the sea ice environment is a significant interphase between the polar ocean and the atmosphere and should be accounted for when studying how climate change may affect the mercury cycle in polar regions.

NASA's Observes Effects of Summer Melt on Greenland Ice Sheet

NASA Image and Video Library

2017-12-08

NASA's IceBridge, an airborne survey of polar ice, flew over the Helheim/Kangerdlugssuaq region of Greenland on Sept. 11, 2016. This photograph from the flight captures Greenland's Steenstrup Glacier, with the midmorning sun glinting off of the Denmark Strait in the background. IceBridge completed the final flight of the summer campaign to observe the impact of the summer melt season on the ice sheet on Sept. 16. The IceBridge flights, which began on Aug. 27, are mostly repeats of lines that the team flew in early May, so that scientists can observe changes in ice elevation between the spring and late summer. For this short, end-of-summer campaign, the IceBridge scientists flew aboard an HU-25A Guardian aircraft from NASA's Langley Research Center in Hampton, Virginia. Credit: NASA/John Sonntag NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Experimental and analytical investigation of a freezing point depressant fluid ice protection system. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Albright, A. E.

1984-01-01

A glycol-exuding porous leading edge ice protection system was tested in the NASA Icing Research Tunnel. Stainless steel mesh, laser drilled titanium, and composite panels were tested on two general aviation wing sections. Two different glycol-water solutions were evaluated. Minimum glycol flow rates required for anti-icing were obtained as a function of angle of attack, liquid water content, volume median drop diameter, temperature, and velocity. Ice accretions formed after five minutes of icing were shed in three minutes or less using a glycol fluid flow equal to the anti-ice flow rate. Two methods of predicting anti-ice flow rates are presented and compared with a large experimental data base of anti-ice flow rates over a wide range of icing conditions. The first method presented in the ADS-4 document typically predicts flow rates lower than the experimental flow rates. The second method, originally published in 1983, typically predicts flow rates up to 25 percent higher than the experimental flow rates. This method proved to be more consistent between wing-panel configurations. Significant correlation coefficients between the predicted flow rates and the experimental flow rates ranged from .867 to .947.

The right wing of the LEFT airplane

NASA Technical Reports Server (NTRS)

Powell, Arthur G.

1987-01-01

The NASA Leading-Edge Flight Test (LEFT) program addressed the environmental issues which were potential problems in the application of Laminar Flow Control (LFC) to transport aircraft. These included contamination of the LFC surface due to dirt, rain, insect remains, snow, and ice, in the critical leading-edge region. Douglas Aircraft Company designed and built a test article which was mounted on the right wing of the C-140 JetStar aircraft. The test article featured a retractable leading-edge high-lift shield for contamination protection and suction through perforations on the upper surface for LFC. Following a period of developmental flight testing, the aircraft entered simulated airline service, which included exposure to airborne insects, heavy rain, snow, and icing conditions both in the air and on the ground. During the roughly 3 years of flight testing, the test article has consistently demonstrated laminar flow in cruising flight. The experience with the LEFT experiment was summarized with emphasis on significant test findings. The following items were discussed: test article design and features; suction distribution; instrumentation and transition point reckoning; problems and fixes; system performance and maintenance requirements.

Aircraft Observations of the Atmospheric Boundary Layer in the Vicinity of the Marginal Ice Zone Under Conditions of Flow Parallel to the Ice Edge

DTIC Science & Technology

1990-09-01

iNaval P’ostgraduate School (if applicable) MIR Naval l’ostgraduate School 6c Address (city, stair’. and ZIP codr) 7b Address (elty, stai, and ZIP’ codr...Lieutenant, United States Navy B.A., Ithaca College, 1975 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN

Evaluation of Droplet Splashing Algorithm in LEWICE 3.0

NASA Technical Reports Server (NTRS)

Homenko, Hilary N.

2004-01-01

The Icing Branch at NASA Glenn Research has developed a computer program to simulate ice formation on the leading edge of an aircraft wing during flight through cold, moist air. As part of the branch's current research, members have developed software known as LEWICE. This program is capable of predicting the formation of ice under designated weather conditions. The success of LEWICE is an asset to airplane manufacturers, ice protection system manufacturers, and the airline industry. Simulations of ice formation conducted in the tunnel and in flight is costly and time consuming. However, the danger of in-flight icing continues to be a concern for both commercial and military pilots. The LEWICE software is a step towards inexpensive and time efficient prediction of ice collection. In the most recent version of the program, LEWICE contains an algorithm for droplet splashing. Droplet splashing is a natural occurrence that causes accumulation of ice on aircraft surfaces. At impingement water droplets lose a portion of their mass to splashing. With part of each droplet joining the airflow and failing to freeze, early versions of LEWICE without the splashing algorithm over-predicted the collection of ice on the leading edge. The objective of my project was to determine whether the revised version of LEWICE accurately reflected the ice collection data obtained from the Icing Research Tunnel (IRT). The experimental data from the IRT was collected by Mark Potapczuk in January, March and July of 2001 and April and December of 2002. Experimental data points were the result of ice tracings conducted shortly after testing in the tunnel. Run sheets, which included a record of velocity, temperature, liquid water content and droplet diameter, served as the input of the LEWICE computer program. Parameters identical to the tunnel conditions were used to run LEWICE 2.0 and LEWICE 3.0. The results from IRT and versions of LEWICE were compared graphically. After entering the raw experimental data and computer output into a spread sheet, I mapped each ice formation onto a clean airfoil. The LEWICE output provided the data points to graphically depict ice formations developed by the program. weather conditions of runs conducted in January 2001, it was evident that the splashing algorithm of LEWICE 3.0 predicts ice formations more accurately than LEWICE 2.0. Especially at conditions with droplet size between 80 and 160 microns, the splashing algorithm of the new LEWICE version compensated for the loss of droplet mass as a result of splashing. In contrast, LEWICE 2.0 consistently over-predicted the mass of the ice in conditions with droplet size exceeding 80 microns. This evidence confirms that changes made to algorithms of LEWICE 3.0 have increased the accuracy of predicting ice collection.

Clouds

NASA Image and Video Library

2010-09-14

Clouds are common near the north polar caps throughout the spring and summer. The clouds typically cause a haze over the extensive dune fields. This image from NASA Mars Odyssey shows the edge of the cloud front.

Torsion fracture of carbon nanocoils

NASA Astrophysics Data System (ADS)

Yonemura, Taiichiro; Suda, Yoshiyuki; Tanoue, Hideto; Takikawa, Hirofumi; Ue, Hitoshi; Shimizu, Kazuki; Umeda, Yoshito

2012-10-01

We fix a carbon nanocoil (CNC) on a substrate in a focused ion beam instrument and then fracture the CNC with a tensile load. Using the CNC spring index, we estimate the maximum to average stress ratio on the fractured surface to range from 1.3 to 1.7, indicating stress concentration on the coil wire inner edge. Scanning electron microscopy confirms a hollow region on the inner edge of all fractured surfaces.

The Formation each Winter of the Circumpolar Wave in the Sea Ice around Antarctica

NASA Technical Reports Server (NTRS)

Gloersen, Per; White, Warren B.

1999-01-01

Seeking to improve upon the visualization of the Antarctic Circumpolar Wave (ACW) , we compare a 16-year sequence of 6-month winter averages of Antarctic sea ice extents and concentrations with those of adjacent sea surface temperatures (SSTs). Here we follow SSTs around the globe along the maximum sea ice edge rather than in a zonal band equatorward of it. The results are similar to the earlier ones, but the ACWs do not propagate with equal amplitude or speed. Additionally in a sequence of 4 polar stereographic plots of these SSTs and sea ice concentrations, we find a remarkable correlation between SST minima and sea ice concentration maxima, even to the extent of matching contours across the ice-sea boundary, in the sector between 900E and the Palmer Peninsula. Based on these observations, we suggest that the memory of the ACW in the sea ice is carried from one Austral winter to the next by the neighboring SSTS, since the sea ice is nearly absent in the Austral summer.

Wind-sea surface temperature-sea ice relationship in the Chukchi-Beaufort Seas during autumn

NASA Astrophysics Data System (ADS)

Zhang, Jing; Stegall, Steve T.; Zhang, Xiangdong

2018-03-01

Dramatic climate changes, especially the largest sea ice retreat during September and October, in the Chukchi-Beaufort Seas could be a consequence of, and further enhance, complex air-ice-sea interactions. To detect these interaction signals, statistical relationships between surface wind speed, sea surface temperature (SST), and sea ice concentration (SIC) were analyzed. The results show a negative correlation between wind speed and SIC. The relationships between wind speed and SST are complicated by the presence of sea ice, with a negative correlation over open water but a positive correlation in sea ice dominated areas. The examination of spatial structures indicates that wind speed tends to increase when approaching the ice edge from open water and the area fully covered by sea ice. The anomalous downward radiation and thermal advection, as well as their regional distribution, play important roles in shaping these relationships, though wind-driven sub-grid scale boundary layer processes may also have contributions. Considering the feedback loop involved in the wind-SST-SIC relationships, climate model experiments would be required to further untangle the underlying complex physical processes.

17 CFR 150.2 - Position limits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... Hard Red Spring Wheat 600 12,000 12,000 ICE Futures U.S. Cotton No. 2 300 5,000 5,000 Kansas City Board of Trade Hard Winter Wheat 600 12,000 12,000 1 For purposes of compliance with these limits...

17 CFR 150.2 - Position limits.

Code of Federal Regulations, 2012 CFR

2012-04-01

... Hard Red Spring Wheat 600 12,000 12,000 ICE Futures U.S. Cotton No. 2 300 5,000 5,000 Kansas City Board of Trade Hard Winter Wheat 600 12,000 12,000 1 For purposes of compliance with these limits...

17 CFR 150.2 - Position limits.

Code of Federal Regulations, 2014 CFR

2014-04-01

... Hard Red Spring Wheat 600 12,000 12,000 ICE Futures U.S. Cotton No. 2 300 5,000 5,000 Kansas City Board of Trade Hard Winter Wheat 600 12,000 12,000 1 For purposes of compliance with these limits...

Spring in Inca City III

NASA Image and Video Library

2014-11-13

This image, acquired by NASA Mars Reconnaissance Orbiter, shows there are a few more fans on the ridge as spring activity progresses in Inca City. In Inca City another week has passed, and there are a few more fans on the ridge. We are studying the sequence of spring activity with the help of citizen scientists at the Planetfour website, sponsored by Zooniverse. Citizens of planet Earth log on and identify and measure fans and blotches in the South polar region of Mars imaged by HiRISE. With their help we can study the polar weather by looking at how the fan directions change through the spring. We see how the number of fans and blotches depends on the thickness of the ice layer and how high the sun is in the sky. http://photojournal.jpl.nasa.gov/catalog/PIA18894

eMontage: An Architecture for Rapid Integration of Situational Awareness Data at the Edge

DTIC Science & Technology

2013-05-01

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An Experimental Study of the Aerodynamics of a Swept and Unswept Semispan Wing with a Simulated Glaze Ice Accretion

NASA Technical Reports Server (NTRS)

Bragg, Michael B.

1994-01-01

Two semispan wings, one with a rectangular planform and one with 30 degrees of leading edge sweep were tested. Both had a NACA 0012 airfoil section, and both were tested clean and with simulated glaze ice shapes on their leading edges. Several surface roughness were tested. Each model geometry is documented and each surface roughness is explained. Aerodynamic performance of the wing in the form of sectional lift and integrated three-dimensional lift is documented through pressure measurements obtained from rows of surface pressure taps placed at five span locations on the wing. For the rectangular wing, sectional drag near the midspan is obtained from wake total pressure profiles. The data is presented in tabular and graphical form and is also available on computer disk.

Percolation blockage: A process that enables melt pond formation on first year Arctic sea ice

NASA Astrophysics Data System (ADS)

Polashenski, Chris; Golden, Kenneth M.; Perovich, Donald K.; Skyllingstad, Eric; Arnsten, Alexandra; Stwertka, Carolyn; Wright, Nicholas

2017-01-01

Melt pond formation atop Arctic sea ice is a primary control of shortwave energy balance in the Arctic Ocean. During late spring and summer, the ponds determine sea ice albedo and how much solar radiation is transmitted into the upper ocean through the sea ice. The initial formation of ponds requires that melt water be retained above sea level on the ice surface. Both theory and observations, however, show that first year sea ice is so highly porous prior to the formation of melt ponds that multiday retention of water above hydraulic equilibrium should not be possible. Here we present results of percolation experiments that identify and directly demonstrate a mechanism allowing melt pond formation. The infiltration of fresh water into the pore structure of sea ice is responsible for blocking percolation pathways with ice, sealing the ice against water percolation, and allowing water to pool above sea level. We demonstrate that this mechanism is dependent on fresh water availability, known to be predominantly from snowmelt, and ice temperature at melt onset. We argue that the blockage process has the potential to exert significant control over interannual variability in ice albedo. Finally, we suggest that incorporating the mechanism into models would enhance their physical realism. Full treatment would be complex. We provide a simple temperature threshold-based scheme that may be used to incorporate percolation blockage behavior into existing model frameworks.

Method to Generate Full-Span Ice Shape on Swept Wing Using Icing Tunnel Data

NASA Technical Reports Server (NTRS)

Lee, Sam; Camello, Stephanie

2015-01-01

There is a collaborative research program by NASA, FAA, ONERA, and university partners to improve the fidelity of experimental and computational simulation methods for swept-wing ice accretion formulations and resultant aerodynamic effects on large transport aircraft. This research utilizes a 65 scale Common Research Model as the baseline configuration. In order to generate the ice shapes for the aerodynamic testing, ice-accretion testing will be conducted in the NASA Icing Research Tunnel utilizing hybrid model from the 20, 64, and 83 spanwise locations. The models will have full-scale leading edges with truncated chord in order to fit the IRT test section. The ice shapes from the IRT tests will be digitized using a commercially available articulated-arm 3D laser scanning system. The methodology to acquire 3D ice shapes using a laser scanner was developed and validated in a previous research effort. Each of these models will yield a 1.5ft span of ice than can be used. However, a full-span ice accretion will require 75 ft span of ice. This means there will be large gaps between these spanwise ice sections that must be filled, while maintaining all of the important aerodynamic features. A method was developed to generate a full-span ice shape from the three 1.5 ft span ice shapes from the three models.

SUCCESS Evidence for Cirrus Cloud Ice Nucleation Mechanisms

NASA Technical Reports Server (NTRS)

Jensen, Eric; Gore, Warren J. Y. (Technical Monitor)

1997-01-01

During the SUCCESS mission, several measurements were made which should improve our understanding of ice nucleation processes in cirrus clouds. Temperature and water vapor concentration were made with a variety of instruments on the NASA DC-8. These observations should provide accurate upper tropospheric humidities. In particular, we will evaluate what humidities are required for ice nucleation. Preliminary results suggest that substantial supersaturations frequently exist in the upper troposphere. The leading-edge region of wave-clouds (where ice nucleation occurs) was sampled extensively at temperatures near -40 and -60C. These observations should give precise information about conditions required for ice nucleation. In addition, we will relate the observed aerosol composition and size distributions to the ice formation observed to evaluate the role of soot or mineral particles on ice nucleation. As an alternative technique for determining what particles act as ice nuclei, numerous samples of aerosols inside ice crystals were taken. In some cases, large numbers of aerosols were detected in each crystal, indicating that efficient scavenging occurred. Analysis of aerosols in ice crystals when only one particle per crystal was detected should help with the ice nucleation issue. Direct measurements of the ice nucleating activity of ambient aerosols drawn into airborne cloud chambers were also made. Finally, measurements of aerosols and ice crystals in contrails should indicate whether aircraft exhaust soot particles are effective ice nuclei.

Genetic profiling links changing sea-ice to shifting beluga whale migration patterns

PubMed Central

Mahoney, Andrew R.; Suydam, Robert; Quakenbush, Lori; Whiting, Alex; Lowry, Lloyd; Harwood, Lois

2016-01-01

There is increasing concern over how Arctic fauna will adapt to climate related changes in sea-ice. We used long-term sighting and genetic data on beluga whales (Delphinapterus leucas) in conjunction with multi-decadal patterns of sea-ice in the Pacific Arctic to investigate the influence of sea-ice on spring migration and summer residency patterns. Substantial variations in sea-ice conditions were detected across seasons, years and sub-regions, revealing ice–ocean dynamics more complex than Arctic-wide trends suggest. This variation contrasted with a highly consistent pattern of migration and residency by several populations, indicating that belugas can accommodate widely varying sea-ice conditions to perpetuate philopatry to coastal migration destinations. However, a number of anomalous migration and residency events were detected and coincided with anomalous ice years, and in one case with an increase in killer whale (Orcinus orca) sightings and reported predation on beluga whales. The behavioural shifts were likely driven by changing sea-ice and associated changes in resource dispersion and predation risk. Continued reductions in sea-ice may result in increased predation at key aggregation areas and shifts in beluga whale behaviour with implications for population viability, ecosystem structure and the subsistence cultures that rely on them.

Seasonality and edge effect determine herbivory risk according to different plant association models.

PubMed

Miranda, M; Díaz, L; Sicilia, M; Cristóbal, I; Cassinello, J

2011-01-01

We report evidence of hierarchical resource selection by large herbivores and plant neighbouring effects in a Mediterranean ecosystem. Plant palatability was assessed according to herbivore foraging decisions. We hypothesize that under natural conditions large herbivores follow a hierarchical foraging pattern, starting at the landscape scale, and then selecting patches and individual plants. A between- and within-patch selection study was carried out in an area formed by scrubland and pasture patches, connected by habitat edges. With regard to between-patch selection, quality-dependent resource selection is reported: herbivores mainly consume pasture in spring and woody plants in winter. Within-patch selection was also observed in scrub habitats, influenced by season, relative patch palatability and edge effect. We defined a Proximity Index (PI) between palatable and unpalatable plants, which allowed verification of neighbouring effects. In spring, when the preferred food resource (i.e. herbs) is abundant, we observed that in habitat edges large herbivores basically select the relatively scarce palatable shrubs, whereas inside scrubland, unpalatable shrub consumption was related to increasing PI. In winter, a very different picture was observed; there was low consumption of palatable species surrounded by unpalatable species in habitat edges, where the latter were more abundant. These outcomes could be explained though different plant associations described in the literature. We conclude that optimal foraging theory provides a conceptual framework behind the observed interactions between plants and large herbivores in Mediterranean ecosystems. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

Geophysical investigations of the geologic and hydrothermal framework of the Pilgrim Springs Geothermal Area, Alaska

USGS Publications Warehouse

Glen, Jonathan; McPhee, Darcy K.; Bedrosian, Paul A.

2014-01-01

Pilgrim Hot Springs, located on the Seward Peninsula in west-central Alaska, is characterized by hot springs, surrounding thawed regions, and elevated lake temperatures. The area is of interest because of its potential for providing renewable energy for Nome and nearby rural communities. We performed ground and airborne geophysical investigations of the Pilgrim Springs geothermal area to identify areas indicative of high heat flow and saline geothermal fluids, and to map key structures controlling hydrothermal fluid flow. Studies included ground gravity and magnetic measurements, as well as an airborne magnetic and frequency-domain electromagnetic (EM) survey. The structural and conceptual framework developed from this study provides critical information for future development of this resource and is relevant more generally to our understanding of geothermal systems in active extensional basins. Potential field data reveal the Pilgrim area displays a complex geophysical fabric reflecting a network of intersecting fault and fracture sets ranging from inherited basement structures to Tertiary faults. Resistivity models derived from the airborne EM data reveal resistivity anomalies in the upper 100 m of the subsurface that suggest elevated temperatures and the presence of saline fluids. A northwest trending fabric across the northeastern portion of the survey area parallels structures to the east that may be related to accommodation between the two major mountain ranges south (Kigluaik) and east (Bendeleben) of Pilgrim Springs. The area from the springs southward to the range front, however, is characterized by east-west trending, range-front-parallel anomalies likely caused by late Cenozoic structures associated with north-south extension that formed the basin. The area around the springs (~10 km2 ) is coincident with a circular magnetic high punctuated by several east-west trending magnetic lows, the most prominent occurring directly over the springs. These features possibly result from hydrothermal alteration imposed by fluids migrating along intra-basin faults related to recent north-south extension. The Pilgrim River valley is characterized by a NE-elongate gravity low that reveals a basin extending to depths of ~300 m beneath Pilgrim Springs and deepening to ~800 m to the southwest. The margins of the gravity low are sharply defined by northeasttrending gradients that probably reflect the edges of fault-bounded structural blocks. The southeastern edge of the low, which lies very close to the springs, also corresponds with prominent NE-striking anomalies seen in magnetic and resistivity models. Together, these features define a structure we refer to as the Northeast Fault. The location of the hot springs appears to be related to the intersection of the Northeast Fault with a N-oriented structure marked by the abrupt western edge of a resistivity low surrounding the hot springs. While the hot springs represent the primary outflow of geothermal fluids, additional outflow extends from the springs northeast along the Northeast fault to another thaw zone that we interpret to be a secondary region of concentrated upflow of geothermal fluids. The Northeast Fault apparently controls shallow geothermal fluid flow, and may also provide an important pathway conveying deep fluids to the shallow subsurface. We suggest that geothermal fluids may derive from a reservoir residing beneath the sediment basin southwest of the springs. If so, the shape of the basin, which narrows and shallows towards the springs, may funnel fluids beneath the springs where they intersect the Northeast Fault allowing them to reach the surface. An alternative pathway for reservoir fluids to reach intermediate to shallow depths may be afforded by the main Kigluaik range front fault that coincides with a resistivity anomaly possibly resulting from fluid flow and associated hydrothermal mineralization occurring within the fault zone.

The Future Is Coming: Electronic Health Records

MedlinePlus

... Current Issue Past Issues The Future Is Coming: Electronic Health Records Past Issues / Spring 2009 Table of ... special conference on the cutting-edge topic of electronic health records (EHR) on May 20-21, 2009, ...

Interior view, perspective view looking from the east southeast to ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior view, perspective view looking from the east southeast to fireplace and mantel - National Park Seminary, Music Hall, Linden Lane at western edge of campus, Silver Spring, Montgomery County, MD

Interior view, room 1103 northeast anteroom, general view to show ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior view, room 1103 northeast anteroom, general view to show fireplace and windows - National Park Seminary, Music Hall, Linden Lane at western edge of campus, Silver Spring, Montgomery County, MD