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Sample records for alamos sea ice

  1. Uncertainty quantification and global sensitivity analysis of the Los Alamos sea ice model

    NASA Astrophysics Data System (ADS)

    Urrego-Blanco, Jorge R.; Urban, Nathan M.; Hunke, Elizabeth C.; Turner, Adrian K.; Jeffery, Nicole

    2016-04-01

    Changes in the high-latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with midlatitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. We present a quantitative way to assess uncertainty in complex computer models, which is a new approach in the analysis of sea ice models. We characterize parametric uncertainty in the Los Alamos sea ice model (CICE) in a standalone configuration and quantify the sensitivity of sea ice area, extent, and volume with respect to uncertainty in 39 individual model parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one at a time, this study uses a global variance-based approach in which Sobol' sequences are used to efficiently sample the full 39-dimensional parameter space. We implement a fast emulator of the sea ice model whose predictions of sea ice extent, area, and volume are used to compute the Sobol' sensitivity indices of the 39 parameters. Main effects and interactions among the most influential parameters are also estimated by a nonparametric regression technique based on generalized additive models. A ranking based on the sensitivity indices indicates that model predictions are most sensitive to snow parameters such as snow conductivity and grain size, and the drainage of melt ponds. It is recommended that research be prioritized toward more accurately determining these most influential parameter values by observational studies or by improving parameterizations in the sea ice model.

  2. MPAS-CICE: A new Los Alamos sea-ice model for regionally refined model domains

    NASA Astrophysics Data System (ADS)

    Turner, A. K.

    2015-12-01

    We present MPAS-CICE, the new Los Alamos National Laboratory sea-ice model. MPAS-CICE uses the Modeling for Prediction Across Scales (MPAS) modeling framework and has been developed to use variable resolution spherical Voronoi tessellation meshes, which allow regional refinement, as well as regular quadrilateral grids. In the later case the model physics reduces to that of the current Los Alamos model, CICE. While the velocity solver and incremental remapping advection have been written specifically for meshes composed of arbitrary shaped polygons, the model uses the column physics directly from CICE. MPAS-CICE is a component of ACME, the new Department of Energy global coupled climate model.

  3. Level-ice melt ponds in the Los Alamos sea ice model, CICE

    NASA Astrophysics Data System (ADS)

    Hunke, Elizabeth C.; Hebert, David A.; Lecomte, Olivier

    2013-11-01

    A new meltpond parameterization has been developed for the CICE sea ice model, taking advantage of the level ice tracer available in the model. The ponds evolve according to physically based process descriptions, assuming a depth-area ratio for changes in pond volume. A novel aspect of the new scheme is that the ponds are carried as tracers on the level ice area of each thickness category, thus limiting their spatial extent based on the simulated sea ice topography. This limiting is meant to approximate the horizontal drainage of melt water into depressions in ice floes. Simulated melt pond processes include collection of liquid melt water and rain into ponds, drainage through permeable sea ice or over the edges of floes, infiltration of snow by pond water, and refreezing of ponds. Furthermore, snow that falls on top of ponds whose top surface has refrozen blocks radiation from penetrating into the ponds and sea ice below. Along with a control simulation, we present a range of sensitivity tests to parameters related to each subprocess described by the parameterization. With the exception of one parameter that alters the albedo of snow-covered pond ice, results are not highly sensitive to these parameters unless an entire process is removed. The snow simulation itself is critical, because the volume of snow deposition and rate of snow melt largely determine the timing and extent of the simulated melt ponds. Nevertheless, compensating effects moderate the model's sensitivity to precipitation changes. For instance, infiltration of the snow by melt water postpones the appearance of ponds and the subsequent acceleration of melting through albedo feedback, while snow on top of refrozen pond ice also reduces the ponds' effect on the radiation budget. By construction, the model simulation of level and ridged ice is also important for this parameterization. We find that as sea ice thins, either through time or when comparing sensitivity tests, the area of level ice

  4. Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Cavalieri, Donald J.

    2005-01-01

    Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

  5. Sea Ice

    NASA Technical Reports Server (NTRS)

    Perovich, D.; Gerland, S.; Hendricks, S.; Meier, Walter N.; Nicolaus, M.; Richter-Menge, J.; Tschudi, M.

    2013-01-01

    During 2013, Arctic sea ice extent remained well below normal, but the September 2013 minimum extent was substantially higher than the record-breaking minimum in 2012. Nonetheless, the minimum was still much lower than normal and the long-term trend Arctic September extent is -13.7 per decade relative to the 1981-2010 average. The less extreme conditions this year compared to 2012 were due to cooler temperatures and wind patterns that favored retention of ice through the summer. Sea ice thickness and volume remained near record-low levels, though indications are of slightly thicker ice compared to the record low of 2012.

  6. Arctic Sea ice model sensitivities.

    SciTech Connect

    Peterson, Kara J.; Bochev, Pavel Blagoveston; Paskaleva, Biliana Stefanova

    2010-12-01

    Arctic sea ice is an important component of the global climate system and, due to feedback effects, the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice state to internal model parameters. A new sea ice model that holds some promise for improving sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of this MPM sea ice code and compare it with the Los Alamos National Laboratory CICE code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness,and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

  7. Biogeochemistry in Sea Ice: CICE model developments

    SciTech Connect

    Jeffery, Nicole; Hunke, Elizabeth; Elliott, Scott; Turner, Adrian

    2012-06-18

    Polar primary production unfolds in a dynamic sea ice environment, and the interactions of sea ice with ocean support and mediate this production. In spring, for example, fresh melt water contributes to the shoaling of the mixed layer enhancing ice edge blooms. In contrast, sea ice formation in the fall reduces light penetration to the upper ocean slowing primary production in marine waters. Polar biogeochemical modeling studies typically consider these types of ice-ocean interactions. However, sea ice itself is a biogeochemically active medium, contributing a significant and, possibly, essential source of primary production to polar regions in early spring and fall. Here we present numerical simulations using the Los Alamos Sea Ice Model (CICE) with prognostic salinity and sea ice biogeochemistry. This study investigates the relationship between sea ice multiphase physics and sea ice productivity. Of particular emphasis are the processes of gravity drainage, melt water flushing, and snow loading. During sea ice formation, desalination by gravity drainage facilitates nutrient exchange between ocean and ice maintaining ice algal blooms in early spring. Melt water flushing releases ice algae and nutrients to underlying waters limiting ice production. Finally, snow loading, particularly in the Southern Ocean, forces sea ice below the ocean surface driving an upward flow of nutrient rich water into the ice to the benefit of interior and freeboard communities. Incorporating ice microphysics in CICE has given us an important tool for assessing the importance of these processes for polar algal production at global scales.

  8. Sea ice terminology

    SciTech Connect

    Not Available

    1980-09-01

    A group of definitions of terms related to sea ice is presented, as well as a graphic representation of late winter ice zonation of the Beaufort Sea Coast. Terms included in the definition list are belt, bergy bit, bight, brash ice, calving, close pack ice, compacting, compact pack ice, concentration, consolidated pack ice, crack, diffuse ice edge, fast ice, fast-ice boundary, fast-ice edge, first-year ice, flaw, flaw lead, floe, flooded ice, fractured, fractured zone, fracturing, glacier, grey ice, grey-white ice, growler, hummock, iceberg, iceberg tongue, ice blink, ice boundary, ice cake, ice edge, ice foot, ice free, ice island, ice shelf, large fracture, lead, medium fracture, multiyear ice, nilas, old ice, open pack ice, open water, pack ice, polar ice, polynya, puddle, rafted ice, rafting, ram, ridge, rotten ice, second-year ice, shearing, shore lead, shore polynya, small fracture, strip, tabular berg, thaw holes, very close pack ice, very open pack ice, water sky, young coastal ice, and young ice.

  9. 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. PMID:24015900

  10. Operation IceBridge: Sea Ice Interlude

    NASA Video Gallery

    Sea ice comes in an array of shapes and sizes and has its own ephemeral beauty. Operation IceBridge studies sea ice at both poles, and also runs across interesting formations en route to other targ...

  11. Arctic Sea Ice Maximum 2011

    NASA Video Gallery

    AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began ...

  12. 2011 Sea Ice Minimum

    NASA Video Gallery

    This video shows Arctic sea ice from March 7, 2011, to Sept. 9, 2011, ending with a comparison of the 30-year average minimum extent, shown in yellow, and the Northwest Passage, in red. (no audio) ...

  13. Record Sea Ice Minimum

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The seasonal cycle of sea ice variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970-1989. This study focuses on the time period 1980-1989. The simulated seasonal-mean fields of sea ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric ice edge. In spring and fall, similar thermodynamic and dynamic

  15. Seafloor Control on Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Clemente-Colon, P.; Rigor, I. G.; Hall, D. K.; Neumann, G.

    2011-01-01

    The seafloor has a profound role in Arctic sea ice formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea ice on the ocean surface. Sea ice dynamics, forced by surface winds, are also guided by seafloor features in preferential directions. Here, satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics. Bathymetric effects on sea ice formation are clearly observed in the conformation between sea ice patterns and bathymetric characteristics in the peripheral seas. Beyond local features, bathymetric control appears over extensive ice-prone regions across the Arctic Ocean. The large-scale conformation between bathymetry and patterns of different synoptic sea ice classes, including seasonal and perennial sea ice, is identified. An implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable, as observed by scatterometer data in the decade of the 2000s, while the minimum ice extent has decreased drastically. Because of the geologic control, the sea ice cover can expand only as far as it reaches the seashore, the continental shelf break, or other pronounced bathymetric features in the peripheral seas. Since the seafloor does not change significantly for decades or centuries, sea ice patterns can be recurrent around certain bathymetric features, which, once identified, may help improve short-term forecast and seasonal outlook of the sea ice cover. Moreover, the seafloor can indirectly influence cloud cover by its control on sea ice distribution, which differentially modulates the latent heat flux through ice covered and open water areas.

  16. Sea ice radiative forcing, sea ice area, and climate sensitivity

    NASA Astrophysics Data System (ADS)

    Caldeira, Ken; Cvijanovic, Ivana

    2014-05-01

    Changes in sea ice cover affect climate sensitivity by modifying albedo and surface heat flux exchange, which in turn affect the absorbed solar radiation at the surface as well as cloud cover, atmospheric water content and poleward atmospheric heat transport. Here, we use a configuration of the Community Earth System Model 1.0.4 with a slab ocean model and a thermodynamic-dynamic sea ice model to investigate the overall net effect of feedbacks associated with the sea ice loss. We analyze the strength of the overall sea ice feedback in terms of two factors: the sensitivity of sea ice area to changes in temperature, and the sensitivity of sea ice radiative forcing to changes in sea ice area. In this model configuration, sea ice area decreases by ~3 × 1012 m2 per K of global warming, while the effective global radiative forcing per square meter of sea ice loss is ~0.1 × 10-12 W m-2. The product of these two terms (~0.3 W m-2 K-1) approximately equals the difference in climate feedback parameter found in simulations with sea ice response (1.05 W m-2 K-1) and simulations without sea ice response (1.31 W m-2 K-1 or 1.35 W m-2 K-1, depending on the method used to disable changes in sea ice cover). Thus, we find that in our model simulations, sea ice response accounts for about 20% to 22% of the climate sensitivity to an imposed change in radiative forcing. In our model, the additional radiative forcing resulting from a loss of all sea ice in the 'pre-industrial' state is comparable to but somewhat less than the radiative forcing from a doubling of atmospheric CO2 content.

  17. Sea Ice Radiative Forcing, Sea Ice Area, and Climate Sensitivity

    NASA Astrophysics Data System (ADS)

    Caldeira, K.; Cvijanovic, I.

    2014-12-01

    Changes in sea ice cover affect climate sensitivity by modifying albedo and surface heat flux exchange, which in turn affect the absorbed solar radiation at the surface as well as cloud cover, atmospheric water content and poleward atmospheric heat transport. Here, we use a configuration of the Community Earth System Model 1.0.4 with a slab ocean model and a thermodynamic-dynamic sea ice model to investigate the overall net effect of feedbacks associated with the sea ice loss. We analyze the strength of the overall sea ice feedback in terms of two factors: the sensitivity of sea ice area to changes in temperature, and the sensitivity of sea ice radiative forcing to changes in sea ice area. In this model configuration, sea ice area decreases by ~3 × 1012 m2 per K of global warming, while the effective global radiative forcing per unit area of sea ice loss is ~0.1 × 10-12 W m-2. The product of these two terms (~0.3 W m-2 K-1) approximately equals the difference in climate feedback parameter found in simulations with sea ice response (1.05 W m-2 K-1) and simulations without sea ice response (1.31 W m-2 K-1 or 1.35 W m-2 K-1, depending on the method used to disable the changes in sea ice cover). Thus, we find that in our model simulations, sea ice response accounts for about 20% to 22% of the climate sensitivity to an imposed change in radiative forcing. In our model, the additional radiative forcing resulting from a loss of all sea-ice in the "pre-industrial" state is comparable to but somewhat less than the radiative forcing from a doubling of atmospheric CO2 content.

  18. Sea ice/climate studies

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.

    1988-01-01

    The objectives were to determine and analyze the annual cycle of sea ice extents in the Arctic Ocean and peripheral seas and bays over the period 1973 to 1986, looking in particular for any long term trends; to examine the relationship between local sea ice covers and the surrounding atmosphere and ocean; and to examine sea ice as a potential early indicator of climate change. The work involves creating regional and hemispheric time series of sea ice variables from satellite passive microwave data and analyzing these through various intercomparisons amongst themselves and with oceanographic and atmospheric fields.

  19. Sea ice transports in the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Harms, Sabine; Fahrbach, Eberhard; Strass, Volker H.

    2001-05-01

    Time series of sea ice draft in the Weddell Sea are evaluated together with hydrographic observations, satellite passive microwave data, and ice drift for estimation of the freshwater fluxes into and out of the Weddell Sea. Ice draft is measured with moored upward looking sonars since 1990 along two transects across the Weddell Gyre. One transect, extending from the tip of the Antarctic Peninsula to Kapp Norvegia, was sampled between 1990 and 1994 and covers the flow into and out of the southern Weddell Sea. The other transect, sampled since 1996 and extending from the Antarctic continent northward along the Greenwich meridian, covers the exchange of water masses between the eastern and the western Weddell Sea. In order to relate results obtained during the different time periods, empirical relationships are established between the length of the sea ice season, derived from the satellite passive microwave data and defined as the number of days per year with the sea ice concentration exceeding 15%, and (1) the annual mean ice draft and (2) the annual mean ice volume transport. By using these empirical relationships, estimates of annual mean ice drafts and ice volume transports are derived at all mooring sites for the period February 1979 through February 1999. Wind and current force a westward ice transport in the coastal areas of the eastern Weddell Sea and a northward ice transport in the west. During the 2-year period 1991/1992 the mean ice volume export from the Weddell Sea is (50 ± 19) × 103 m3 s-1. This freshwater export is representative for a longer-term (20-year) mean and exceeds the average amount of freshwater gained by precipitation and ice shelf melt by about 19×103 m3 s-1, yielding an upper bound for the formation rate of newly ventilated bottom water in the Weddell Sea of 2.6 Sv.

  20. 2013 Arctic Sea Ice Minimum

    NASA Video Gallery

    After an unusually cold summer in the northernmost latitudes, Arctic sea ice appears to have reached its annual minimum summer extent for 2013 on Sept. 13, the NASA-supported National Snow and Ice ...

  1. Arctic Sea Ice Predictability and the Sea Ice Prediction Network

    NASA Astrophysics Data System (ADS)

    Wiggins, H. V.; Stroeve, J. C.

    2014-12-01

    Drastic reductions in Arctic sea ice cover have increased the demand for Arctic sea ice predictions by a range of stakeholders, including local communities, resource managers, industry and the public. The science of sea-ice prediction has been challenged to keep up with these developments. Efforts such as the SEARCH Sea Ice Outlook (SIO; http://www.arcus.org/sipn/sea-ice-outlook) and the Sea Ice for Walrus Outlook have provided a forum for the international sea-ice prediction and observing community to explore and compare different approaches. The SIO, originally organized by the Study of Environmental Change (SEARCH), is now managed by the new Sea Ice Prediction Network (SIPN), which is building a collaborative network of scientists and stakeholders to improve arctic sea ice prediction. The SIO synthesizes predictions from a variety of methods, including heuristic and from a statistical and/or dynamical model. In a recent study, SIO data from 2008 to 2013 were analyzed. The analysis revealed that in some years the predictions were very successful, in other years they were not. Years that were anomalous compared to the long-term trend have proven more difficult to predict, regardless of which method was employed. This year, in response to feedback from users and contributors to the SIO, several enhancements have been made to the SIO reports. One is to encourage contributors to provide spatial probability maps of sea ice cover in September and the first day each location becomes ice-free; these are an example of subseasonal to seasonal, local-scale predictions. Another enhancement is a separate analysis of the modeling contributions. In the June 2014 SIO report, 10 of 28 outlooks were produced from models that explicitly simulate sea ice from dynamic-thermodynamic sea ice models. Half of the models included fully-coupled (atmosphere, ice, and ocean) models that additionally employ data assimilation. Both of these subsets (models and coupled models with data

  2. Reducing uncertainty in high-resolution sea ice models.

    SciTech Connect

    Peterson, Kara J.; Bochev, Pavel Blagoveston

    2013-07-01

    Arctic sea ice is an important component of the global climate system, reflecting a significant amount of solar radiation, insulating the ocean from the atmosphere and influencing ocean circulation by modifying the salinity of the upper ocean. The thickness and extent of Arctic sea ice have shown a significant decline in recent decades with implications for global climate as well as regional geopolitics. Increasing interest in exploration as well as climate feedback effects make predictive mathematical modeling of sea ice a task of tremendous practical import. Satellite data obtained over the last few decades have provided a wealth of information on sea ice motion and deformation. The data clearly show that ice deformation is focused along narrow linear features and this type of deformation is not well-represented in existing models. To improve sea ice dynamics we have incorporated an anisotropic rheology into the Los Alamos National Laboratory global sea ice model, CICE. Sensitivity analyses were performed using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA) to determine the impact of material parameters on sea ice response functions. Two material strength parameters that exhibited the most significant impact on responses were further analyzed to evaluate their influence on quantitative comparisons between model output and data. The sensitivity analysis along with ten year model runs indicate that while the anisotropic rheology provides some benefit in velocity predictions, additional improvements are required to make this material model a viable alternative for global sea ice simulations.

  3. Extracting sea ice geophysical parameters from multisource data

    NASA Astrophysics Data System (ADS)

    Zakharov, I.; Prasad, S.; Qi, S.; Bobby, P.

    2014-12-01

    Sea ice monitoring is an important field of scientific research and relevant to marine operational applications. Remote sensing imagery is useful for monitoring sea ice, identifying and tracking ice features over broad spatial scales. At the same time the current satellites have limited capabilities in providing some of the important sea ice characteristics with required temporal frequency and coverage. This work investigates possibilities of model-based estimation of sea ice geophysical parameters from multisource data. The Los Alamos sea ice model (CICE) was implemented on a high resolution regional scale (up to 2km) taking model advantages, such as the possibility of including oceanographic and climatological information, in order to extract parameters and to determine the dynamic and thermodynamic behaviour of sea ice. The sea ice simulation was performed over the Baffin Bay region and the Labrador Sea demonstrating a good agreement with remote sensing measurements acquired by the microwave radiometer and altimeter satellites. The number of geophysical parameters, such as ice thickness, age, concentration, floes statistics, and ridging were extracted using model and imaging satellite data. Information on characteristics of sea ice pressure ridges was also derived from synthetic aperture radar (SAR) imagery. The method to study ice ridges was validated with detailed information from very high resolution (0.5m) optical satellites and involved 3D modelling and visualization of ridge information. The identification of various ice types, including ice deformation features and glacier ice, was performed using medium and low resolution SAR and optical satellite data as well as their fusion product.

  4. Microwave emission characteristics of sea ice

    NASA Technical Reports Server (NTRS)

    Edgerton, A. T.; Poe, G.

    1972-01-01

    A general classification is presented for sea ice brightness temperatures with categories of high and low emission, corresponding to young and weathered sea ice, respectively. A sea ice emission model was developed which allows variations of ice salinity and temperature in directions perpendicular to the ice surface.

  5. Arctic Sea Ice Minimum, 2015

    NASA Video Gallery

    This animation shows the evolution of the Arctic sea ice cover from its wintertime maximum extent, which was reached on Feb. 25, 2015, and was the lowest on record, to its apparent yearly minimum, ...

  6. Arctic Sea Ice, Summer 2014

    NASA Video Gallery

    An animation of daily Arctic sea ice extent in summer 2014, from March 21, 2014 to Sept. 17, 2014 – when the ice appeared to reach it’s minimum extent for the year. It’s the sixth lowest minimum se...

  7. Melting Ice, Rising Seas

    NASA Video Gallery

    Sea level rise is an indicator that our planet is warming. Much of the world's population lives on or near the coast, and rising seas are something worth watching. Sea level can rise for two reason...

  8. Sea Ice Concentration and Extent

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2014-01-01

    Among the most seasonal and most dynamic parameters on the surface of the Earth is sea ice which at any one time covers about 3-6% of the planet. In the Northern Hemisphere, sea ice grows in extent from about 6 x 10(exp 6) sq km to 16 x 10(exp 6) sq km, while in the Southern Hemisphere, it grows from about 3 x 10(exp 6) sq km to about 19 x 10(exp 6) sq km (Comiso, 2010; Gloersen et al., 1992). Sea ice is up to about 2-3 m thick in the Northern Hemisphere and about 1 m thick in the Southern Hemisphere (Wadhams, 2002), and compared to the average ocean depth of about 3 km, it is a relatively thin, fragile sheet that can break due to waves and winds or melt due to upwelling of warm water. Being constantly advected by winds, waves, and currents, sea ice is very dynamic and usually follows the directions of the many gyres in the polar regions. Despite its vast expanse, the sea ice cover was previously left largely unstudied and it was only in recent years that we have understood its true impact and significance as related to the Earths climate, the oceans, and marine life.

  9. Sea ice and the ocean mixed layer over the Antarctic shelf seas

    NASA Astrophysics Data System (ADS)

    Petty, A.; Holland, P.; Feltham, D. L.

    2013-12-01

    An ocean mixed layer model has been incorporated into the Los Alamos sea ice model CICE, to investigate regional variations in the surface-driven formation of Antarctic shelf sea waters. The model captures well the expected sea ice thickness distribution and produces deep (>500 m) mixed layers in the Weddell and Ross shelf seas each winter. By deconstructing the surface power input to the mixed layer, we have shown that the salt/fresh water flux from sea ice growth/melt dominates the evolution of the mixed layer in all shelf sea regions, with a smaller contribution from the mixed layer-surface heat flux. The Weddell and Ross shelf seas have the highest annual ice growth, with a large fraction exported northwards each year, whereas the Bellingshausen shelf sea experiences the highest annual ice melt, driven by the advection of ice from the northeast. Forcing the model with ERA-Interim (1980-2011) and hadGEM2-ES (1980-2099) atmospheric data allows us to look at the impact of atmospheric trends on the sea ice and ocean mixed layer. Both simulations show a shallowing of the wintertime mixed layer in the Amundsen & Bellingshausen seas, potentially increasing the access of warm CDW to ice shelves in both regions. The ERA-I hindcast simulation shows a significant freshening in the Ross and salinification in the Weddell due to surface driven trends (primarily through changes in the sea ice). The Ross freshening is smaller than observed however, highlighting the important role of ice shelf melt in the Amundsen Sea.

  10. Development, sensitivity analysis, and uncertainty quantification of high-fidelity arctic sea ice models.

    SciTech Connect

    Peterson, Kara J.; Bochev, Pavel Blagoveston; Paskaleva, Biliana S.

    2010-09-01

    Arctic sea ice is an important component of the global climate system and due to feedback effects the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice to model physical parameters. A new sea ice model that has the potential to improve sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of the Los Alamos National Laboratory CICE code and the MPM sea ice code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness, and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

  11. Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model.

    PubMed

    Tsamados, Michel; Feltham, Daniel; Petty, Alek; Schroeder, David; Flocco, Daniela

    2015-10-13

    We present a modelling study of processes controlling the summer melt of the Arctic sea ice cover. We perform a sensitivity study and focus our interest on the thermodynamics at the ice-atmosphere and ice-ocean interfaces. We use the Los Alamos community sea ice model CICE, and additionally implement and test three new parametrization schemes: (i) a prognostic mixed layer; (ii) a three equation boundary condition for the salt and heat flux at the ice-ocean interface; and (iii) a new lateral melt parametrization. Recent additions to the CICE model are also tested, including explicit melt ponds, a form drag parametrization and a halodynamic brine drainage scheme. The various sea ice parametrizations tested in this sensitivity study introduce a wide spread in the simulated sea ice characteristics. For each simulation, the total melt is decomposed into its surface, bottom and lateral melt components to assess the processes driving melt and how this varies regionally and temporally. Because this study quantifies the relative importance of several processes in driving the summer melt of sea ice, this work can serve as a guide for future research priorities. PMID:26347538

  12. AMSR2 Daily Arctic Sea Ice - 2014

    NASA Video Gallery

    In this animation, the daily Arctic sea ice and seasonal land cover change progress through time, from March 21, 2014 through the 3rd of August, 2014. Over the water, Arctic sea ice changes from da...

  13. Primary Production in Antarctic Sea Ice

    NASA Technical Reports Server (NTRS)

    Arrigo, Kevin R.; Worthen, Denise L.; Lizotte, Michael P.; Dixon, Paul; Dieckmann, Gerhard

    1997-01-01

    A numerical model shows that in Antarctic sea ice, increased flooding in regions with thick snow cover enhances primary production in the infiltration (surface) layer. Productivity in the freeboard (sea level) layer is also determined by sea ice porosity, which varies with temperature. Spatial and temporal variation in snow thickness and the proportion of first-year ice thus determine regional differences in sea ice primary production. Model results show that of the 40 tera-grams of carbon produced annually in the Antarctic ice pack, 75 percent was associated with first-year ice and nearly 50 percent was produced in the Weddell Sea.

  14. Annual sea ice. An air-sea gas exchange moderator

    SciTech Connect

    Gosink, T.A.; Kelley, J.J.

    1982-01-01

    Arctic annual sea ice, particularly when it is relatively warm (> -15/sup 0/C) permits significant gas exchange between the sea and air throughout the entire year. Sea ice, particularly annual sea ice, differs from freshwater ice with respect to its permeability to gases. The presence of brine allows for significant air-sea-ice exchange of CO/sub 2/ throughout the winter, which may significantly affect the global carbon dioxide balance. Other trace gases are also noted to be enriched in sea ice, but less is known about their importance to air-sea-interactions at this time. Both physical and biological factors cause and modify evolution of gases from the surface of sea ice. Quantitative and qualitative descriptions of the nature and physical behavior of sea ice with respect to brine and gases are discussed.

  15. Multi-year Arctic Sea Ice

    NASA Video Gallery

    The most visible change in the Arctic region in recent years has been the rapid decline of the perennial ice cover. The perennial ice is the portion of the sea ice floating on the surface of the oc...

  16. Sea ice-albedo climate feedback mechanism

    SciTech Connect

    Schramm, J.L.; Curry, J.A.; Ebert, E.E.

    1995-02-01

    The sea ice-albedo feedback mechanism over the Arctic Ocean multiyear sea ice is investigated by conducting a series of experiments using several one-dimensional models of the coupled sea ice-atmosphere system. In its simplest form, ice-albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature, further decreasing the area cover of snow and ice. It is shown that the sea ice-albedo feedback can operate even in multiyear pack ice, without the disappearance of this ice, associated with internal processes occurring within the multiyear ice pack (e.g., duration of the snow cover, ice thickness, ice distribution, lead fraction, and melt pond characteristics). The strength of the ice-albedo feedback mechanism is compared for several different thermodynamic sea ice models: a new model that includes ice thickness distribution., the Ebert and Curry model, the Mayjut and Untersteiner model, and the Semtner level-3 and level-0 models. The climate forcing is chosen to be a perturbation of the surface heat flux, and cloud and water vapor feedbacks are inoperative so that the effects of the sea ice-albedo feedback mechanism can be isolated. The inclusion of melt ponds significantly strengthens the ice-albedo feedback, while the ice thickness distribution decreases the strength of the modeled sea ice-albedo feedback. It is emphasized that accurately modeling present-day sea ice thickness is not adequate for a sea ice parameterization; the correct physical processes must be included so that the sea ice parameterization yields correct sensitivities to external forcing. 22 refs., 6 figs., 1 tab.

  17. Loss of sea ice in the Arctic.

    PubMed

    Perovich, Donald K; Richter-Menge, Jacqueline A

    2009-01-01

    The Arctic sea ice cover is in decline. The areal extent of the ice cover has been decreasing for the past few decades at an accelerating rate. Evidence also points to a decrease in sea ice thickness and a reduction in the amount of thicker perennial sea ice. A general global warming trend has made the ice cover more vulnerable to natural fluctuations in atmospheric and oceanic forcing. The observed reduction in Arctic sea ice is a consequence of both thermodynamic and dynamic processes, including such factors as preconditioning of the ice cover, overall warming trends, changes in cloud coverage, shifts in atmospheric circulation patterns, increased export of older ice out of the Arctic, advection of ocean heat from the Pacific and North Atlantic, enhanced solar heating of the ocean, and the ice-albedo feedback. The diminishing Arctic sea ice is creating social, political, economic, and ecological challenges. PMID:21141043

  18. The Sea Ice Board Game

    ERIC Educational Resources Information Center

    Bertram, Kathryn Berry

    2008-01-01

    The National Science Foundation-funded Arctic Climate Modeling Program (ACMP) provides "curriculum resource-based professional development" materials that combine current science information with practical classroom instruction embedded with "best practice" techniques for teaching science to diverse students. The Sea Ice Board Game, described…

  19. The U.S. Navy's Emerging Sea Ice Prediction Capabilities

    NASA Astrophysics Data System (ADS)

    Allard, Richard; Campbell, Tim; Hebert, David; Metzger, E. Joseph; Posey, Pamela; Wallcraft, Alan; Smedstad, Ole Martin; Gaberšek, Saša; Jin, Yi; Wang, Shouping

    2014-05-01

    The U.S. Navy's regional and global coupled sea ice modeling activities are described. The Arctic Cap Nowcast Forecast System (ACNFS) is a 3.5 km coupled sea ice-ocean model that produces 7 day forecasts of the Arctic sea ice state in all ice covered areas in the northern hemisphere (poleward of 40°N). The ocean component is the HYbrid Coordinate Ocean Model (HYCOM) and is coupled to the Los Alamos National Laboratory Community Ice CodE (CICE) via the Earth System Modeling Framework (ESMF). The ocean and sea ice models are run in an assimilative cycle with the Navy's Coupled Ocean Data Assimilation (NCODA) system. The ACNFS was transitioned to operations at the Naval Oceanographic Office in 2013 to serve its customer, the National Ice Center. The Global Ocean forecast System (GOFS3.1) is essentially an extension of ACNFS to the globe at 1/12° (equatorial) resolution, still 3.5 km in the Arctic, and it will provide sea ice predictions for the Arctic and Antarctic. Testing and validation is underway and an operational transition is planned for 2015, when GOFS3.1 will replace the ACNFS. A relocatable regional capability is being developed by coupling CICE to the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). This new system will have an advanced snow-ice albedo representation and produce coupled forecasts out to 7-10 days with resolutions for the atmosphere and sea ice models at 1-3 km. Examples of these emerging capabilities will be presented.

  20. Sea ice data for all: NSIDC's Arctic Sea Ice News & Analysis

    NASA Astrophysics Data System (ADS)

    Vizcarra, N.; Stroeve, J. C.; Serreze, M. C.; Scambos, T. A.; Meier, W.

    2014-12-01

    Arctic sea ice has long been recognized as a sensitive climate indicator and has undergone a dramatic decline over the past thirty years. The National Snow and Ice Data Center's Arctic Sea Ice News & Analysis blog continues to offer the public a transparent view of sea ice data and analysis. We have expanded our interactive sea ice graph to include Antarctic sea ice in response to increased attention from the public as a result of unexpected behavior of sea ice in the south. This poster explores the blog's new features and how other researchers, the media, and the public are currently using them.

  1. Creating Arctic Sea Ice Protected Areas?

    NASA Astrophysics Data System (ADS)

    Pfirman, S.; Hoff, K.; Temblay, B.; Fowler, C.

    2008-12-01

    As Arctic sea ice retreats and the Northwest Passage and Northern Sea Route open, the Arctic will experience more extensive human activity than it has ever encountered before. New development will put pressure on a system already struggling to adapt to a changing environment. In this analysis, locations are identified within the Arctic that could be protected from resource extraction, transportation and other development in order to create refuges and protect remnants of sea ice habitat, as the Arctic transitions to ice-free summer conditions. Arctic sea ice forms largely along the Siberian and Alaskan coasts and is advected across the North Pole towards Fram Strait, the Canadian Archipelago and the Barents Sea. In addition to the future loss of ice itself, contaminants entrained in sea ice in one part of the ocean can affect other regions as the ice drifts. Using observations and models of sea ice origins, trajectories and ages, we track sea ice from its origins towards marginal ice zones, mapping pathways and termination locations. Critical sea ice source areas and collection regions are identified with the goal of aiding in the protection of the remaining Arctic sea ice habitat for as long as possible.

  2. The role of sea ice dynamics in global climate change

    NASA Technical Reports Server (NTRS)

    Hibler, William D., III

    1992-01-01

    The topics covered include the following: general characteristics of sea ice drift; sea ice rheology; ice thickness distribution; sea ice thermodynamic models; equilibrium thermodynamic models; effect of internal brine pockets and snow cover; model simulations of Arctic Sea ice; and sensitivity of sea ice models to climate change.

  3. The dynamics of frazil ice formation in leads and its role in the mass balance of the sea ice pack.

    NASA Astrophysics Data System (ADS)

    Heorton, Harry; Feltham, Daniel

    2015-04-01

    Lead are cracks in sea ice that expose the ocean to the cold atmosphere resulting in the supercooling of the ocean and the formation of frazil ice crystals within the mixed layer. Here we present two studies of ice formation in leads: a single lead model focussing on frazil crystals of varying size within the vertical structure of the mixed layer; a new module explicitly describing frazil ice formation in leads incorporated into the Los Alamos sea ice model (CICE). Both studies consider the supercooling of the ocean, the concentration of frazil crystals within the ocean and their precipitation to the ocean surface as grease ice pushed against one of the lead edges by wind and water drag. The results from the single lead model show how the vertical structure of the mixed layer develops after the lead opens. Sensitivity studies reveal how changing wind speeds play the greatest role in the time taken to refreeze a lead. In the CICE model the new module slows down the refreezing of leads resulting in an longer period of frazil ice production when compared to the original model code. The fraction of frazil-derived sea ice increases from 10% to 50% with the inclusion of the new module. Ice formation rates are increased in areas of high ice concentration and thus has a greater impact within multiyear ice than in the marginal seas. The thickness of sea ice in the central Arctic increases by over 0.5 m whereas within the Antarctic it remains unchanged.

  4. Enhanced Sea Ice Concentration and Ice Temperature Algorithms for AMSR

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.; Manning, Will; Gersten, Robert

    1998-01-01

    Accurate quantification of sea ice concentration and ice temperature from satellite passive microwave data is important because they provide the only long term, spatially detailed and consistent data set needed to study the climatology of the polar regions. Sea ice concentration data are used to derive large-scale daily ice extents that are utilized in trend analysis of the global sea ice cover. They are also used to quantify the amount of open water and thin ice in polynya and divergence regions which together with ice temperatures are in turn needed to estimate vertical heat and salinity fluxes in these regions. Sea ice concentrations have been derived from the NASA Team and Bootstrap algorithms while a separate technique for deriving ice temperature has been reported. An integrated technique that will utilizes most of the channels of AMSR (Advanced Microwave Scanning Radiometer) has been developed. The technique uses data from the 6 GHz and 37 GHz channels at vertical polarization obtain an initial estimate of sea ice concentration and ice temperature. The derived ice temperature is then utilized to estimate the emissivities for the corresponding observations at all the other channels. A procedure for calculating the ice concentration similar to the Bootstrap technique is then used but with variables being emissivities instead of brightness temperatures to minimizes errors associated with spatial changes in ice temperatures within the ice pack. Comparative studies of ice concentration results with those from other algorithms, including the original Bootstrap algorithm and those from high resolution satellite visible and infrared data will be presented. Also, results from a simulation study that demonstrates the effectiveness of the technique in correcting for spatial variations in ice temperatures will be shown. The ice temperature results are likewise compared with satellite infrared and buoy data with the latter adjusted to account for the effects of the snow

  5. Sea ice and the ocean mixed layer over the Antarctic shelf seas

    NASA Astrophysics Data System (ADS)

    Petty, A. A.; Holland, P. R.; Feltham, D. L.

    2013-08-01

    An ocean mixed layer model has been incorporated into the Los Alamos sea ice model CICE to investigate regional variations in the surface-driven formation of Antarctic shelf waters. This model captures well the expected sea ice thickness distribution, and produces deep (> 500 m) mixed layers in the Weddell and Ross shelf seas each winter. This results in the complete destratification of the water column in deep southern coastal regions (leading to HSSW formation) and also in some shallower regions (no HSSW formation) of these seas. Shallower mixed layers are produced in the Amundsen and Bellingshausen seas. By deconstructing the surface power input to the mixed layer, we show that the freshwater flux from sea ice growth/melt dominates the evolution of the mixed layer in all seas, with a smaller contribution from the surface heat flux. The Weddell and Ross shelf seas receive an annual surplus of energy at the surface, the Amundsen shelf sea energy input in autumn/winter is balanced by energy extraction in spring/summer, and the Bellingshausen shelf sea experiences an annual surface energy deficit, through both a low energy input in autumn/winter and the highest energy loss in spring/summer. An analysis of the sea ice mass balance demonstrates the contrasting mean ice growth, melt and export in each region. The Weddell and Ross shelf seas have the highest annual ice growth, with a large fraction exported northwards each year, whereas the Bellingshausen shelf sea experiences the highest annual ice melt, driven by the advection of ice from the northeast. A linear regression analysis is performed to determine the temporal and spatial correlations between the autumn/winter mixed layer power input and several atmospheric variables. The temporal mean Weddell and Ross autumn/winter power input shows stronger spatial correlation to several atmospheric variables compared to the Amundsen and Bellingshausen. In contrast the spatial mean autumn/winter power input shows stronger

  6. Modelling the deformation and force balance of anisotropic Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Heorton, Harry; Feltham, Daniel; Tsamados, Michel; Schroeder, David

    2016-04-01

    The movement and spatial distribution of Arctic sea ice is due to its response to external forces. The deformation of Arctic sea ice is observed to have structural alignment on all length scales. By considering the alignment of diamond-shaped sea ice floes an anisotropic rheology has been developed for use in a climate sea ice model. Here we present investigations into the role of anisotropy in calculating the internal stress gradient of Arctic sea ice over climate length and time scales in a state-of-the-art climate sea ice model, the Los Alamos Sea Ice model. Our investigations are focused on the link between the external dynamical forcing and the emergent properties of sea ice such as its drift speed and thickness distribution. We analyse the model's response to external forcing over short time scales showing the characteristics of deformation events for different sea ice states and anisotropic alignment. We show how these events add up to produce the full seasonal stress balance and sea ice state over the Arctic ocean.

  7. The strength anisotropia of sea ice

    SciTech Connect

    Evdokimov, G.N.; Rogachko, S.I.

    1994-12-31

    The hydraulic-engineering structure calculations of sea ice formation force require the sea ice strength data. The strength characteristics values and the types of sea ice formations in view of water depth define the type and the design of future structures in each particular region of supposed construction. The most objective information on the sea ice physical and technical properties can be obtained by field investigations ad the existing methods of their calculations refer to a great number of errors. The accumulated bank of data on studying the sea ice formation strength properties show one that ice as a natural material is of great crystalline structure variety. The level ice fields have a number of particularities. The crystal sizes increase in ice thickness. The crystals consist of fresh-water thin plates 0.5--0.6 mm in thickness oriented by pickle-water interlayers. Difference in thickness of the sea ice cover structure is one of the main causes of the changes strength characteristics layer. Besides that the sea ice strength depends upon the destroying force direction in reference to crystal orientation which characterizes the sea ice anisotropia as a material.

  8. Sea Ice Mapping using Unmanned Aerial Systems

    NASA Astrophysics Data System (ADS)

    Solbø, S.; Storvold, R.

    2011-12-01

    Mapping of sea ice extent and sea ice features is an important task in climate research. Since the arctic coastal and oceanic areas have a high probability of cloud coverage, aerial platforms are superior to satellite measurements for high-resolution optical measurements. However, routine observations of sea ice conditions present a variety of problems using conventional piloted aircrafts. Specially, the availability of suitable aircrafts for lease does not cover the demand in major parts of the arctic. With the recent advances in unmanned aerial systems (UAS), there is a high possibility of establishing routine, cost effective aerial observations of sea ice conditions in the near future. Unmanned aerial systems can carry a wide variety of sensors useful for characterizing sea-ice features. For instance, the CryoWing UAS, a system initially designed for measurements of the cryosphere, can be equipped with digital cameras, surface thermometers and laser altimeters for measuring freeboard of ice flows. In this work we will present results from recent CryoWing sea ice flights on Svalbard, Norway. The emphasis will be on data processing for stitching together images acquired with the non-stabilized camera payload, to form high-resolution mosaics covering large spatial areas. These data are being employed to map ice conditions; including ice and lead features and melt ponds. These high-resolution mosaics are also well suited for sea-ice mechanics, classification studies and for validation of satellite sea-ice products.

  9. Growth of false bottoms under sea ice

    NASA Astrophysics Data System (ADS)

    Smith, Naomi; Feltham, Daniel; Flocco, Daniela

    2015-04-01

    In the summer months, melt water from the surface of Arctic sea ice can percolate through the relatively porous ice and collect at the ice-ocean interface, filling hollows in the base of the ice. These pools are called under-ice melt ponds. Freezing can occur at the interface between the fresh water and the oceanic mixed layer, forming a sheet of ice called a false bottom. These have been observed to thicken and migrate upwards over time. False bottoms insulate the true base of the sea ice from the ocean and their formation is a significant mechanism of Arctic sea ice summer growth. Current parameterisations of basal ablation of sea ice in climate models do not account for these processes, the inclusion of which could improve the accuracy of predictions of Arctic sea ice. In this poster, a one-dimensional thermodynamic model of the evolution of under-ice melt ponds and false bottoms is presented. Our aim is to develop a parameterisation of the impact of under ice melt ponds and false bottoms on basal ablation of Arctic sea ice appropriate for use in gridded climate models.

  10. 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.

  11. Arctic Sea Ice Changes 2011-2012

    NASA Video Gallery

    Animation showing changes in monthly Arctic sea ice volume using data from ESA's CryoSat-2 (red dots) and estimates from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) (solid li...

  12. Arctic Cyclone Breaks Up Sea Ice

    NASA Video Gallery

    A powerful storm wreaked havoc on the Arctic sea ice cover in August 2012. This visualization shows the strength and direction of the winds and their impact on the ice: the red vectors represent th...

  13. Sea Ice Friction: The Effect of Ice Rubble

    NASA Astrophysics Data System (ADS)

    Scourfield, S.; Sammonds, P. R.; Lishman, B.; Riska, K.; Marchenko, A. V.

    2015-12-01

    Ice deformation processes in the Arctic often generate ice rubble, and situations arise where ice fragments of varying size separate sea ice floes. While the shear forces between sea ice floes in direct contact with each other are controlled by ice-ice friction, what is not known is how the slip of the floes is affected by the presence of rubble between the sliding surfaces. We present the result of field experiments undertaken on fjord ice in Svea, Svalbard, which investigated the velocity and hold time dependence of sea ice friction involving ice gouge. Average air temperature for the duration of time in which experiments were run was -12.4°C, and the thickness of the level fjord ice was 70 cm. A double-direct-shear experiment was done on floating sea ice in the field, with the addition of rubble ice between the sliding surfaces. This was achieved by moving a floating ice block through a channel of open water whilst subjected to normal loading, which was transferred through regions of ice rubble on both sides of the mobile block. The ice rubble regions were 30 cm deep and 50 cm wide. The displacement of the block and the force needed to move the block were measured. The rate dependence of friction was investigated for speeds of 10-3 to 10-2 ms-1. To investigate the state dependence of friction, slide-hold-slide (SHS) tests were conducted for hold times ranging from 1 second to 18 hours. When comparing the results from these experiments with a model for ice friction presented by Schulson and Fortt (2013), similar behaviour is seen at low hold times, where the peak coefficient of friction has a linear relationship with the logarithm of hold time. This is not the case for long hold times, however, and we attribute this to thermal consolidation of the ice rubble region.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  16. Arctic sea ice decline: Introduction

    NASA Astrophysics Data System (ADS)

    DeWeaver, Eric T.

    By any measure, the loss of Arctic sea ice cover in September 2007 was spectacular. The National Snow and Ice Data Center (NSIDC) called it a loss "the size of Alaska and Texas combined," in comparison to the 1979-2000 September mean. Record-breaking minima in sea ice extent are not unexpected, given the declining trend of the past 30 years and its recent acceleration [e.g., Meier et al., 2007; Deser and Teng, this volume]. But the 2007 minimum was remarkable even compared to the decline, a full four standard deviations below the trend line (H. Stern, quoted by Schweiger et al. [2008]). Kerr [2007] reported an Alaska-sized loss compared to the previous record low in 2005, which was itself an Alaska-sized retreat from the value at the beginning of the satellite era in 1979. Deser and Teng point out that the loss between September 2006 and September 2007 is as large as the entire September extent loss from 1979 to 2006.

  17. The Antarctic sea ice concentration budget of an ocean-sea ice coupled model

    NASA Astrophysics Data System (ADS)

    Lecomte, Olivier; Goosse, Hugues; Fichefet, Thierry; Holland, Paul R.; Uotila, Petteri

    2015-04-01

    The Antarctic sea ice concentration budget of the NEMO-LIM ocean-sea ice coupled model is computed and analyzed. Following a previously developed method, the sea ice concentration balance over the autumn-winter seasons is decomposed into four terms, including the sea ice concentration change during the period of interest, advection, divergence and a residual accounting for the net contribution of thermodynamics and ice deformation. Preliminary results from this analysis show that the geographical patterns of all budget terms over 1992-2010 are in qualitative agreement with the observed ones. Sea ice thermodynamic growth is maintained by horizontal divergence near the continent and in the central ice pack, while melting close to the ice edge is led by sea ice advection. Quantitatively however, the inner ice pack divergence and associated sea ice freezing are much stronger, as compared to observations. The advection of sea ice in both the central pack and the marginal areas are likewise stronger, which corroborates the findings of a previous study in which the same methods were applied to a fully coupled climate model. Nonetheless, the seasonal evolution of sea ice area and total extent are reasonably well simulated, since enhanced sea ice freezing due to larger divergence in the central pack is compensated by intensified melting in the outer pack owing to faster advection. Those strong dynamic components in the sea ice concentration budget are due to ice velocities that tend to be biased high all around Antarctica and particularly near the ice edge. The obtained results show that the applied method is particularly well suited for assessing the skills of an ocean-sea ice coupled model in simulating the seasonal and regional evolution of Antarctic sea ice for the proper physical reasons.

  18. 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.

  19. Solar radiation interactions with seasonal sea ice

    NASA Astrophysics Data System (ADS)

    Ehn, Jens Kristian

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

  20. The Last Arctic Sea Ice Refuge

    NASA Astrophysics Data System (ADS)

    Pfirman, S. L.; Tremblay, B.; Newton, R.; Fowler, C.

    2010-12-01

    Summer sea ice may persist along the northern flank of Canada and Greenland for decades longer than the rest of the Arctic, raising the possibility of a naturally formed refugium for ice-associated species. Observations and models indicate that some ice in this region forms locally, while some is transported to the area by winds and ocean currents. Depending on future changes in melt patterns and sea ice transport rates, both the central Arctic and Siberian shelf seas may be sources of ice to the region. An international system of monitoring and management of the sea ice refuge, along with the ice source regions, has the potential to maintain viable habitat for ice-associated species, including polar bears, for decades into the future. Issues to consider in developing a strategy include: + the likely duration and extent of summer sea ice in this region based on observations, models and paleoenvironmental information + the extent and characteristics of the “ice shed” contributing sea ice to the refuge, including its dynamics, physical and biological characteristics as well as potential for contamination from local or long-range sources + likely assemblages of ice-associated species and their habitats + potential stressors such as transportation, tourism, resource extraction, contamination + policy, governance, and development issues including management strategies that could maintain the viability of the refuge.

  1. Variability and Trends in Sea Ice Extent and Ice Production in the Ross Sea

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino; Kwok, Ronald; Martin, Seelye; Gordon, Arnold L.

    2011-01-01

    Salt release during sea ice formation in the Ross Sea coastal regions is regarded as a primary forcing for the regional generation of Antarctic Bottom Water. Passive microwave data from November 1978 through 2008 are used to examine the detailed seasonal and interannual characteristics of the sea ice cover of the Ross Sea and the adjacent Bellingshausen and Amundsen seas. For this period the sea ice extent in the Ross Sea shows the greatest increase of all the Antarctic seas. Variability in the ice cover in these regions is linked to changes in the Southern Annular Mode and secondarily to the Antarctic Circumpolar Wave. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate of increase in the net ice export of about 30,000 sq km/yr. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 cu km/yr, which is almost identical, within error bars, to our estimate of the trend in ice production. The increase in brine rejection in the Ross Shelf Polynya associated with the estimated increase with the ice production, however, is not consistent with the reported Ross Sea salinity decrease. The locally generated sea ice enhancement of Ross Sea salinity may be offset by an increase of relatively low salinity of the water advected into the region from the Amundsen Sea, a consequence of increased precipitation and regional glacial ice melt.

  2. Fracture Networks in Sea Ice

    NASA Astrophysics Data System (ADS)

    Vevatne, Jonas; Rimstad, Eivind; Hansen, Alex; Korsnes, Reinert; Hope, Sigmund

    2014-04-01

    Fracturing and refreezing of sea ice in the Kara sea are investigated using complex networkanalysis. By going to the dual network, where the fractures are nodes and their intersectionslinks, we gain access to topological features which are easy to measure and hence comparewith modeled networks. Resulting network reveal statistical properties of the fracturing process.The dual networks have a broad degree distribution, with a scale-free tail, high clusteringand efficiency. The degree-degree correlation profile shows disassortative behavior, indicatingpreferential growth. This implies that long, dominating fractures appear earlier than shorterfractures, and that the short fractures which are created later tend to connect to the longfractures.The knowledge of the fracturing process is used to construct growing fracture network (GFN)model which provides insight into the generation of fracture networks. The GFN model isprimarily based on the observation that fractures in sea ice are likely to end when hitting existingfractures. Based on an investigation of which fractures survive over time, a simple model forrefreezing is also added to the GFN model, and the model is analyzed and compared to the realnetworks.

  3. Unlocking a Sea Ice Secret

    SciTech Connect

    Dr. Rachel Obbard

    2013-04-22

    Dr. Rachel Obbard and her research group from Dartmouth College traveled to the Antarctic to collect samples of sea ice. Next stop: the GeoSoilEnviroCARS x-ray beamline at the Advanced Photon Source at Argonne National Laboratory in Illinois. This U.S. Department of Energy Office of Science synchrotron x-ray research facility gave the Obbard team the frontier scientific tools they needed to study the path bromide takes as it travels from the ocean to the atmosphere.

  4. The importance of large scale sea ice drift and ice type distribution on ice extent in the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Schwegmann, S.; Haas, C.; Timmermann, R.; Gerdes, R.; Lemke, P.

    2009-12-01

    In austral winter large parts of Antarctic Seas are covered by sea ice. This modifies the exchange of heat, mass and momentum between ocean and atmosphere. The knowledge of ice extent and its variability is necessary for an adequate simulation of those fluxes and thus for climate modelling. The goal of this study is the observation of interannual and seasonal ice extent variations and their underlying causes. Variability is analysed by using monthly means of microwave and scatterometer satellite data. Results are correlated with ice drift variations calculated from a Finite Element Sea ice-Ocean Model (FESOM) and with satellite derived sea ice drift products to determine the dependency of ice extent on sea ice drift. An additional cause for changing ice extent could be the variability of ice type distribution, i.e. the contribution of first and second year ice to the total ice covered area. These ice types are determined on monthly time scales from scatterometer satellite data. Ice class distribution and sea ice drift variability are compared with the characteristics and variability of the Southern Annular Mode (SAM) to evaluate the relative importance of different sea ice parameters for shaping Weddell Sea ice extent and its variability.

  5. Arctic Sea Ice from March to August 2016

    NASA Video Gallery

    In this animation, the daily Arctic sea ice and seasonal land cover change progress through time, from the prior sea ice maximum March 24, 2016, through Aug. 13, 2016. The Arctic sea ice cover like...

  6. Recent State of Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.; Rigor, I. G.; Clemente-Colón, P.; Perovich, D. K.; Richter-Menge, J. A.; Chao, Y.; Neumann, G.; Ortmeyer, M.

    2008-12-01

    We present the recent state of Arctic sea ice including observations from 2008 in a context of a multi-decadal perspective. A new record has been set in the reduction of Arctic perennial sea ice extent this winter. As of 1 March 2008, the extent of perennial sea ice was reduced by one million km2 compared to that at the same time last year as observed by the NASA SeaWinds scatterometer on the QuikSCAT satellite (QSCAT). This decrease of perennial ice continues the precipitous declining trend observed in this decade. Furthermore, the perennial sea ice pattern change was deduced by buoy-based estimates with 50 years of data from drifting buoys and measurement camps to track sea ice movement around the Arctic Ocean. The combination of the satellite and surface data records confirms that the reduction of winter perennial ice extent broke the record in 2008 compared to data over the last half century. In the winter, the loss of perennial ice extent was driven by winds that compressed the ice and transported it out of the Fram Strait and Nares Strait to warmer ocean waters at lower latitudes, where the ice melted very effectively. Another historical fact is that the boundary of perennial sea ice already crossed the North Pole (NP) in February 2008, leaving the area around the NP occupied by seasonal sea ice. This is the first time, not only from the satellite data record but also in the history of sea ice charting at the National Ice Center since the 1970's, that observations indicate the seasonal ice migration into the NP area so early in winter. In the Bering Sea by 12 March 2008, the sea ice edge reached to an extent that coincided with the continental shelf break, indicating bathymetric effects on the distribution of water masses along the Aleutian North Slope, Bering Slope, Anadyr, and Kamchatka Currents that governed the pattern of sea ice formation in this region. Moreover, QSCAT observations showed that, in the 2008 winter, seasonal ice occupied the Northern Sea

  7. Trend analysis of Arctic sea ice extent

    NASA Astrophysics Data System (ADS)

    Silva, M. E.; Barbosa, S. M.; Antunes, Luís; Rocha, Conceição

    2009-04-01

    The extent of Arctic sea ice is a fundamental parameter of Arctic climate variability. In the context of climate change, the area covered by ice in the Arctic is a particularly useful indicator of recent changes in the Arctic environment. Climate models are in near universal agreement that Arctic sea ice extent will decline through the 21st century as a consequence of global warming and many studies predict a ice free Arctic as soon as 2012. Time series of satellite passive microwave observations allow to assess the temporal changes in the extent of Arctic sea ice. Much of the analysis of the ice extent time series, as in most climate studies from observational data, have been focussed on the computation of deterministic linear trends by ordinary least squares. However, many different processes, including deterministic, unit root and long-range dependent processes can engender trend like features in a time series. Several parametric tests have been developed, mainly in econometrics, to discriminate between stationarity (no trend), deterministic trend and stochastic trends. Here, these tests are applied in the trend analysis of the sea ice extent time series available at National Snow and Ice Data Center. The parametric stationary tests, Augmented Dickey-Fuller (ADF), Phillips-Perron (PP) and the KPSS, do not support an overall deterministic trend in the time series of Arctic sea ice extent. Therefore, alternative parametrizations such as long-range dependence should be considered for characterising long-term Arctic sea ice variability.

  8. A Global Sensitivity Analysis of Arctic Sea Ice to Parameter Uncertainty in the CICE v5.1 Sea Ice Model

    NASA Astrophysics Data System (ADS)

    Urrego-Blanco, J. R.; Urban, N. M.; Hunke, E. C.

    2015-12-01

    Sea ice and climate models are key to understand and predict ongoing changes in the Arctic climate system, particularly sharp reductions in sea ice area and volume. There are, however, uncertainties arising from multiple sources, including parametric uncertainty, which affect model output. The Los Alamos Sea Ice Model (CICE) includes complex parameterizations of sea ice processes with a large number of parameters for which accurate values are still not well established. To enhance the credibility of sea ice predictions, it is necessary to understand the sensitivity of model results to uncertainties in input parameters. In this work we conduct a variance-based global sensitivity analysis of sea ice extent, area, and volume. This approach allows full exploration of our 40-dimensional parametric space, and the model sensitivity is quantified in terms of main and total effects indices. The global sensitivity analysis does not require assumptions of additivity or linearity, implicit in the most commonly used one-at-a-time sensitivity analyses. A Gaussian process emulator of the sea ice model is built and then used to generate the large number of samples necessary to calculate the sensitivity indices, at a much lower computational cost than using the full model. The sensitivity indices are used to rank the most important model parameters affecting Arctic sea ice extent, area, and volume. The most important parameters contributing to the model variance include snow conductivity and grain size, and the time-scale for drainage of melt ponds. Other important parameters include the thickness of the ice radiative scattering layer, ice density, and the ice-ocean drag coefficient. We discuss physical processes that explain variations in simulated sea ice variables in terms of the first order parameter effects and the most important interactions among them.

  9. Sea ice and the ocean mixed layer over the Antarctic shelf seas

    NASA Astrophysics Data System (ADS)

    Petty, A. A.; Holland, P. R.; Feltham, D. L.

    2014-04-01

    An ocean mixed-layer model has been incorporated into the Los Alamos sea ice model CICE to investigate regional variations in the surface-driven formation of Antarctic shelf waters. This model captures well the expected sea ice thickness distribution, and produces deep (> 500 m) mixed layers in the Weddell and Ross shelf seas each winter. This results in the complete destratification of the water column in deep southern coastal regions leading to high-salinity shelf water (HSSW) formation, and also in some shallower regions (no HSSW formation) of these seas. Shallower mixed layers are produced in the Amundsen and Bellingshausen seas. By deconstructing the surface processes driving the mixed-layer depth evolution, we show that the net salt flux from sea ice growth/melt dominates the evolution of the mixed layer in all regions, with a smaller contribution from the surface heat flux and a negligible input from wind stress. The Weddell and Ross shelf seas receive an annual surplus of mixing energy at the surface; the Amundsen shelf sea energy input in autumn/winter is balanced by energy extraction in spring/summer; and the Bellingshausen shelf sea experiences an annual surface energy deficit, through both a low energy input in autumn/winter and the highest energy loss in spring/summer. An analysis of the sea ice mass balance demonstrates the contrasting mean ice growth, melt and export in each region. The Weddell and Ross shelf seas have the highest annual ice growth, with a large fraction exported northwards each year, whereas the Bellingshausen shelf sea experiences the highest annual ice melt, driven by the advection of ice from the northeast. A linear regression analysis is performed to determine the link between the autumn/winter mixed-layer deepening and several atmospheric variables. The Weddell and Ross shelf seas show stronger spatial correlations (temporal mean - intra-regional variability) between the autumn/winter mixed-layer deepening and several

  10. Sea-Ice Roughness, Morphogenesis and Kinematics --- Approaches to Learn from the Complexity of Sea Ice

    NASA Astrophysics Data System (ADS)

    Herzfeld, U. C.; Williams, S.; Maslanik, J.

    2007-12-01

    Recent studies of the alarming retreat of the Arctic sea ice have been largely based on observations of sea-ice coverage. This is not sufficient to capture changes in the sea-ice's mass, hence there is an increasing interest in measuring the thickness of sea-ice. However, the complexity of sea ice renders the latter a difficult task: (1) at any time, the sea ice has a complex form and appearance in remote-sensing observations, (2) due to ridging and rubbling, the mass of sea ice is not directly related to its thickness, (3) sea ice forms in a series of morphogenetic processes, and (4) sea ice moves. Here we present mathematical approaches to analyze spatial roughness of the surface of sea ice and of its snow-layer thickness, morphogenetic processes and deformation characteristics as a means to quantify and characterize sea-ice properties, processes and provinces. Applications include analyses of passive microwave data, SAR data, laser and radar elevation data and multispectral image data, from satellite, unmanned aerial vehicle and aircraft platforms, and field data.

  11. Seasonal change of antarctic sea ice cover.

    PubMed

    Gordon, A L; Taylor, H W

    1975-01-31

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

  12. MODIS Snow and Sea Ice Products

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.

    2004-01-01

    In this chapter, we describe the suite of Earth Observing System (EOS) Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow and sea ice products. Global, daily products, developed at Goddard Space Flight Center, are archived and distributed through the National Snow and Ice Data Center at various resolutions and on different grids useful for different communities Snow products include binary snow cover, snow albedo, and in the near future, fraction of snow in a 5OO-m pixel. Sea ice products include ice extent determined with two different algorithms, and sea ice surface temperature. The algorithms used to develop these products are described. Both the snow and sea ice products, available since February 24,2000, are useful for modelers. Validation of the products is also discussed.

  13. On the measure of sea ice area from sea ice concentration data sets

    NASA Astrophysics Data System (ADS)

    Boccolari, Mauro; Parmiggiani, Flavio

    2015-10-01

    The measure of sea ice surface variability provides a fundamental information on the climatology of the Arctic region. Sea ice extension is conventionally measured by two parameters, i.e. Sea Ice Extent (SIE) and Sea Ice Area (SIA), both parameters being derived from Sea Ice Concentration (SIC) data sets. In this work a new parameter (CSIA) is introduced, which takes into account only the compact sea-ice, which is defined as the sea-ice having concentration at least equal the 70%. Aim of this study is to compare the performances of the two parameters, SIA and CSIA, in analyzing the trends of three monthly time-series of the whole Arctic region. The SIC data set used in this study was produced by the Institute of Environmental Physics of the University of Bremen and covers the period January 2003 - December 2014, i.e. the period in which the data set is built using the new AMSR passive microwave sensor.

  14. A toy model of sea ice growth

    NASA Technical Reports Server (NTRS)

    Thorndike, Alan S.

    1992-01-01

    My purpose here is to present a simplified treatment of the growth of sea ice. By ignoring many details, it is possible to obtain several results that help to clarify the ways in which the sea ice cover will respond to climate change. Three models are discussed. The first deals with the growth of sea ice during the cold season. The second describes the cycle of growth and melting for perennial ice. The third model extends the second to account for the possibility that the ice melts away entirely in the summer. In each case, the objective is to understand what physical processes are most important, what ice properties determine the ice behavior, and to which climate variables the system is most sensitive.

  15. Record Arctic Sea Ice Loss in 2007

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This image of the Arctic was produced from sea ice observations collected by the Advanced Microwave Scanning Radiometer (AMSR-E) Instrument on NASA's Aqua satellite on September 16, overlaid on the NASA Blue Marble. The image captures ice conditions at the end of the melt season. Sea ice (white, image center) stretches across the Arctic Ocean from Greenland to Russia, but large areas of open water were apparent as well. In addition to record melt, the summer of 2007 brought an ice-free opening though the Northwest Passage that lasted several weeks. The Northeast Passage did not open during the summer of 2007, however, as a substantial tongue of ice remained in place north of the Russian coast. According to the National Snow and Ice Data Center (NSIDC), on September 16, 2007, sea ice extent dropped to 4.13 million square kilometers (1.59 million square miles)--38 percent below average and 24 percent below the 2005 record.

  16. What Can Sea Ice Reconstructions Tell Us About Recent Regional Trends in Sea Ice Around Antarctica?

    NASA Astrophysics Data System (ADS)

    Abram, N.; Mulvaney, R.; Murphy, E. J.

    2014-12-01

    Satellite observations of recent sea ice changes around Antarctica reveal regionally heterogeneous trends, but with an overall increasing trend in Antarctic-wide sea ice extent. Proposed mechanisms to account for increasing sea ice extent around Antarctica include freshening of the ocean surface due to melting of land ice and northward wind drift associated with strengthening of the Southern Ocean westerly winds. In this study we use extended, regional reconstructions of Antarctic sea ice changes from ice core chemistry and reanalysis of the South Orkney fast ice series to examine long-term relationships between Antarctic regional sea ice changes and surface winds. The formation and breakout of fast ice at the South Orkney islands (Murphy et al., 2014) indicates that westerly wind strength is an important factor in determining spring sea ice retreat in the Weddell Sea region. In contrast, autumn sea ice formation is more strongly influenced by long-lived ocean temperature anomalies and sea ice migration from the previous year, highlighting the multiple influences that act at different times of the year to determine the overall extent of winter sea ice. To assess the hypothesized role of westerly wind changes in driving opposing patterns of recent sea ice change between the Ross Sea and Bellingshausen Sea, we also present a comparison of ice core MSA evidence for sea ice changes derived from the James Ross Island (Mulvaney et al., 2012) and Erebus Saddle (Rhodes et al., 2012) ice cores, and view this in the context of trends in the Southern Annular Mode (Abram et al., 2014) over the last 200 years. References: Abram et al., 2014. Evolution of the Southern Annular Mode over the past millennium. Nature Climate Change. doi: 10.1038/nclimate2235 Mulvaney et al., 2012. Recent Antarctic Peninsula warming relative to Holocene temperature and ice-shelf history. Nature. doi: 10.1038/nature11391 Murphy et al., 2014. Variability of sea ice in the northern Weddell Sea during

  17. Sea Ice Biogeochemistry: A Guide for Modellers

    PubMed Central

    Tedesco, Letizia; Vichi, Marcello

    2014-01-01

    Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes. PMID:24586604

  18. Tortuosity of the Antarctic Sea Ice over the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Beard, J.; Heinrichs, J. F.

    2011-12-01

    The objective of the research was to mathematically characterize the edge of the Antarctic sea ice in the Weddell Sea. Because the sea ice may reflect processes involved in the atmosphere and ocean near the ice edge, it may suggest broader changes on the ice. The chosen method was to compare the tortuosity of the edge over time and across seasons. Because the sea ice may reflect processes involved in the atmosphere and ocean near the ice edge, it may suggest broader changes on the ice. Throughout the research, the shapefiles for the Antarctic sea ice were collected from the National Snow and Ice Data Center website and the coordinates were extracted using an add-in for the MapWindow GIS. These points were then put into Excel separated by year and then the distance factor (an approximation to the tortuosity) was calculated and compared by month over time. Preliminary data has shown that the closer to the winter months, the higher the tortuosity. Statistical analysis has shown that there is no clear relationship between tortuosity and the area of the sea ice, and the tortuosity exhibits a weak negative trend over the past 32 years.

  19. Monitoring Fram Strait sea ice outflow and thin ice thickness

    NASA Technical Reports Server (NTRS)

    Kwok, R.

    2001-01-01

    We propose to: 1) use sequential SAR maps to monitor the profile of sea ice motion through Fram Strait over the period 2003 throught 2005; and 2) explore the potential of using L-band polarimetric data to determine the thickness of thin ice over the same region.

  20. Investigation of radar discrimination of sea ice

    NASA Technical Reports Server (NTRS)

    Parashar, S. K.; Biggs, A. W.; Fung, A. K.; Moore, R. K.

    1974-01-01

    The ability of radar to discriminate sea ice types and their thickness was studied. Radar backscatter measurements at 400 MHz (multi-polarization) and 13.3 GHz (VV polarization) obtained from NASA Earth Resources Aircraft Program Mission 126 were analyzed in detail. The scatterometer data were separated into seven categories of sea ice according to age and thickness as interpreted from stereo aerial photographs. The variations of radar backscatter cross-section with sea ice thickness at various angles are presented at the two frequencies. There is a reversal of angular character of radar return from sea ice less than 18 cm thick at the two frequencies. Multi-year ice (sea ice greater than 180 cm thick) gives strongest return at 13.3 GHz. First-year ice (30 cm to 90 cm thick) gives strongest return at 400 MHz. Open water can be differentiated at both the frequencies. Four-polarization 16.5 GHz radar imagery was also obtained. Open water and three categories of sea ice can be identified on the images. The results of the imagery analysis are consistent with the radar scatterometer results.

  1. On the Role of Sea Ice Deformations in Arctic Climate Change

    NASA Astrophysics Data System (ADS)

    Maslowski, Wieslaw; Osinski, Robert; Roberts, Andrew; DiMaggio, Dominic

    2015-04-01

    Understanding air-sea interactions and their effects on arctic climate change requires comprehensive knowledge of the sea ice dynamics and thermodynamics at a process level. While significant advancement has been made for example in understanding and model representation of sea ice rheology, surface albedo and ice-albedo feedback, there are other processes such as sea ice deformations, which require further studies and model improvement. Of particular potential interest are leads, which control winter air-sea heat exchange and buoyancy input into the ocean, or sea ice ridging and shearing, which affect the ice-ocean coupling. Their importance in arctic climate change under an increasing first-year ice cover is yet to be determined, as global climate models commonly do not resolve such sea ice features at their actual scale, magnitude and frequency and stand-alone high-resolution atmosphere or ice-ocean models do not allow studies of air-sea-ice interactions. We use the Regional Arctic System Model (RASM), which is a fully coupled, high-resolution regional climate model, to study sea ice deformation processes and resulting coupling across the air-sea interface. RASM includes the Weather Research and Forecasting (WRF) atmospheric model, the Parallel Ocean Program (POP), the Community Ice Model (CICE) and the Variable Infiltration Capacity (VIC) land hydrology model. It is configured for the pan-Arctic region at an eddy-permitting resolution of 1/12° for the ice-ocean and 50 km for the atmosphere-land model components. In addition, all RASM components are coupled at high frequency, i.e. at a 20-minute time step. The sea ice component has been upgraded to the Los Alamos Community Ice Model version 5 (CICE5), which allows either Elastic-Viscous-Plastic (EVP) or a new anisotropic (EPA) rheology and incorporates form drag to more realistically represent sea ice morphology and estimate ice-ocean and ice-atmosphere stresses. Results from multiple RASM simulations, using

  2. Arctic sea-ice ridges—Safe heavens for sea-ice fauna during periods of extreme ice melt?

    NASA Astrophysics Data System (ADS)

    Gradinger, Rolf; Bluhm, Bodil; Iken, Katrin

    2010-01-01

    The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30 cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under-ice amphipods were counted in situ in replicate ( N=24-65 per station) 0.25 m 2 quadrats using SCUBA to a maximum water depth of 12 m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9 ind l -1 (median 0.8 ind l -1). In level ice, low ice algal pigment concentrations (<0.1-15.8 μg Chl a l -1), low brine salinities (1.8-21.7) and flushing from the melting sea ice likely explain the low ice meiofauna concentrations. Higher abundances of Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0-200 ind l -1, median 40 ind l -1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114 ind m -2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths >3 m where abundances were up to 42-fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3 m thickness). We further suggest that pressure ridges, which extend into deeper, high

  3. Satellite Remote Sensing: Passive-Microwave Measurements of Sea Ice

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    Satellite passive-microwave measurements of sea ice have provided global or near-global sea ice data for most of the period since the launch of the Nimbus 5 satellite in December 1972, and have done so with horizontal resolutions on the order of 25-50 km and a frequency of every few days. These data have been used to calculate sea ice concentrations (percent areal coverages), sea ice extents, the length of the sea ice season, sea ice temperatures, and sea ice velocities, and to determine the timing of the seasonal onset of melt as well as aspects of the ice-type composition of the sea ice cover. In each case, the calculations are based on the microwave emission characteristics of sea ice and the important contrasts between the microwave emissions of sea ice and those of the surrounding liquid-water medium.

  4. Platelet ice distribution in Antarctic sea ice and its implications for ocean - ice shelf interaction

    NASA Astrophysics Data System (ADS)

    Langhorne, P.; Hughes, K. G.; Gough, A. J.; Smith, I.; Williams, M.; Robinson, N. J.; Stevens, C. L.; Rack, W.; Price, D.; Leonard, G. H.; Mohoney, A. R.; Haas, C.; Haskell, T. G.

    2015-12-01

    Ice shelf basal melting freshens and cools the fluid in the ice shelf-ocean boundary layer, producing Ice Shelf Water (ISW). The potential temperature of ISW is below the surface freezing point. Antarctic sea ice that has been affected by supercooled Ice Shelf Water (ISW) has a unique crystallographic structure and is called platelet ice. We have synthesized platelet ice observations to construct a continent-wide map of the winter presence of ISW at the ocean surface. Where suitable observations exist, oceanic heat fluxes are derived from sub-ice platelet layer measurements and these are shown in the figure. They demonstrate that in some regions of coastal Antarctica, supercooled ISW drives a negative oceanic heat flux of approximately -30 Wm-2 that persists for several months during winter. This heat flux from the sea ice to the ocean significantly increases the sea ice thickness close to an ice shelf. In other regions, particularly where the thinning of ice shelves is believed to be greatest, platelet ice is not observed. The most extensive dataset, which includes our new results, dates back to 1902 and extends north of the combined Ross and McMurdo Ice Shelf front in the southern Ross Sea. Here the surface water is held just below its freezing point as it enters McMurdo Sound from beneath the McMurdo Ice Shelf. Despite a more recent decrease in ocean salinity consistent with observations in the south-western Ross Sea, there has been no detectable change in the volume or temperature of this supercooled ISW under sea ice since the early twentieth century. The inclusion of platelet ice into first year sea ice is an annual process. Hence it will respond immediately to changes in the sub-ice shelf circulation pattern and its export of supercooled water, emphasizing the urgent need for careful, Antarctic-wide monitoring.

  5. Stratospheric Impacts on Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Reichler, Thomas

    2016-04-01

    Long-term circulation change in the stratosphere can have substantial effects on the oceans and their circulation. In this study we investigate whether and how sea ice at the ocean surface responds to intraseasonal stratospheric variability. Our main question is whether the surface impact of stratospheric sudden warmings (SSWs) is strong and long enough to affect sea ice. A related question is whether the increased frequency of SSWs during the 2000s contributed to the rapid decrease in Arctic sea ice during this time. To this end we analyze observations of sea ice, NCEP/NCAR reanalysis, and a long control integration with a stratospherically-enhanced version of the GFDL CM2.1 climate model. From both observations and the model we find that stratospheric extreme events have a demonstrable impact on the distribution of Arctic sea ice. The areas most affected are near the edge of the climatological ice line over the North Atlantic, North Pacific, and the Arctic Ocean. The absolute changes in sea ice coverage amount to +/-10 %. Areas and magnitudes of increase and decrease are about the same. It is thus unlikely that the increased SSW frequency during the 2000s contributed to the decline of sea ice during that period. The sea ice changes are consistent with the impacts of a negative NAO at the surface and can be understood in terms of (1) dynamical change due to altered surface wind stress and (2) thermodynamical change due to altered temperature advection. Both dynamical and thermodynamical change positively reinforce each other in producing sea change. A simple advection model is used to demonstrate that most of the sea ice change can be explained from the sea ice drift due to the anomalous surface wind stress. Changes in the production or melt of sea ice by thermodynamical effects are less important. Overall, this study adds to an increasing body of evidence that the stratosphere not only impacts weather and climate of the atmosphere but also the surface and

  6. Extracellular macromolecules in sea-ice: Effects on sea-ice structure and their implications

    NASA Astrophysics Data System (ADS)

    Ewert, M.; Bayer-Giraldi, M.

    2012-04-01

    Brine inclusions within sea-ice offer a favorable environment for certain marine microorganisms which live and thrive within the ice. These assemblages are a crucial element in the polar ecosystem. Partly entrained by ice platelets into the ice sheet, microorganisms closely interact with the liquid and solid phases of this porous environment (brine and ice), likely influencing their properties. Extracellular polysaccharide substances (EPS) and antifreeze proteins (AFP) have been identified as major elements with the potential to affect ice structure and processes, due to their capability to interact with ice crystals (selected planes in the case of AFPs) and with water molecules and salt ions present in the brine. EPS present in sea water can be selectively retained in the ice during ice formation, with implications for ice structure. Likewise, EPS and AFP released by sea-ice organisms would have a local effect, altering the microenvironment for the benefit of the organism. Macroscopic and microscopic observations showed effects on ice microstructure and a possible increase in brine fraction within the ice caused by AFPs and EPS, implicating changes in ice porosity and permeability. In the following we describe some of the interactions between sea-ice macromolecules, EPS and AFP, and the sea-ice system. We show their influence in ice structure, and discuss probable implications and consequences for microbial survival, distribution of dissolved material between sea-ice and the water column, and possible effects on the seasonal evolution of the ice. All of these could be relevant to the understanding of biogeochemical processes and the limits of habitability, as well as suggest possible applications of these substances.

  7. Strong coupling among Antarctic ice shelves, ocean circulation and sea ice in a global sea-ice - ocean circulation model

    NASA Astrophysics Data System (ADS)

    Sergienko, Olga

    2016-04-01

    The thermodynamic effects of Antarctic ice shelf interaction with ocean circulation are investigated using a global, high-resolution, isopycnal ocean-circulation model coupled to a sea-ice model. The model uses NASA MERRA Reanalysis from 1992 to 2011 as atmospheric forcing. The simulated long-period variability of ice-shelf melting/freezing rates differ across geographic locations. The ice shelves in Antarctic Peninsula, Amundsen and Bellingshausen sea embayments and the Amery Ice Shelf experience an increase in melting starting from 2005. This increase in melting is due to an increase in the subsurface (100-500 m) ocean heat content in the embayments of these ice shelves, which is caused by an increase in sea-ice concentration after 2005, and consequent reduction of the heat loss to the atmosphere. Our simulations provide a strong evidence for a coupling between ocean circulation, sea ice and ice shelves.

  8. SIPEX--Exploring the Antarctic Sea Ice Zone

    ERIC Educational Resources Information Center

    Zicus, Sandra; Dobson, Jane; Worby, Anthony

    2008-01-01

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

  9. Quaternary Sea Ice Reconstruction: Proxy Data and Modeling

    NASA Astrophysics Data System (ADS)

    Gersonde, R.; De Vernal, A.; Wolff, E. W.

    2014-11-01

    The satellite-based observation of distinct contrasts between Arctic and Antarctic sea ice development provides a strong motivation to improve our knowledge of physical and biological processes governing sea ice occurrence and the role of sea ice as a polar climate amplifier. For further insight into such processes, sea ice records must be extended beyond instrumental observations.

  10. Influences of sea ice on eastern Bering Sea phytoplankton

    NASA Astrophysics Data System (ADS)

    Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui

    2015-03-01

    The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions: open water, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

  11. Mirabilite solubility in equilibrium sea ice brines

    NASA Astrophysics Data System (ADS)

    Butler, Benjamin Miles; Papadimitriou, Stathys; Santoro, Anna; Kennedy, Hilary

    2016-06-01

    The sea ice microstructure is permeated by brine channels and pockets that contain concentrated seawater-derived brine. Cooling the sea ice results in further formation of pure ice within these pockets as thermal equilibrium is attained, resulting in a smaller volume of increasingly concentrated residual brine. The coupled changes in temperature and ionic composition result in supersaturation of the brine with respect to mirabilite (Na2SO4·10H2O) at temperatures below -6.38 °C, which consequently precipitates within the sea ice microstructure. Here, mirabilite solubility in natural and synthetic seawater derived brines, representative of sea ice at thermal equilibrium, has been measured in laboratory experiments between 0.2 and -20.6 °C, and hence we present a detailed examination of mirabilite dynamics within the sea ice system. Below -6.38 °C mirabilite displays particularly large changes in solubility as the temperature decreases, and by -20.6 °C its precipitation results in 12.90% and 91.97% reductions in the total dissolved Na+ and SO42- concentrations respectively, compared to that of conservative seawater concentration. Such large non-conservative changes in brine composition could potentially impact upon the measurement of sea ice brine salinity and pH, whilst the altered osmotic conditions may create additional challenges for the sympagic organisms that inhabit the sea ice system. At temperatures above -6.38 °C, mirabilite again displays large changes in solubility that likely aid in impeding its identification in field samples of sea ice. Our solubility measurements display excellent agreement with that of the FREZCHEM model, which was therefore used to supplement our measurements to colder temperatures. Measured and modelled solubility data were incorporated into a 1D model for the growth of first-year Arctic sea ice. Model results ultimately suggest that mirabilite has a near ubiquitous presence in much of the sea ice on Earth, and illustrate the

  12. Influence of sea ice on Arctic precipitation

    PubMed Central

    Kopec, Ben G.; Feng, Xiahong; Michel, Fred A.; Posmentier, Eric S.

    2016-01-01

    Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km2 sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions. PMID:26699509

  13. Influence of sea ice on Arctic precipitation.

    PubMed

    Kopec, Ben G; Feng, Xiahong; Michel, Fred A; Posmentier, Eric S

    2016-01-01

    Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km(2) sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions. PMID:26699509

  14. Sensitivity Studies of Sea Ice Formation In The Kara Sea

    NASA Astrophysics Data System (ADS)

    Hübner, U.; Harms, I.; Backhaus, J. O.

    Sea ice formation is an important process in Arctic shelf seas because it determines environmental conditions in the whole Arctic, in particular at the coasts. Arctic shelf seas receive large amounts of freshwater which has a significant impact on ice forma- tion and which could be affected by climate change. In order to study the direct and indirect influence of river runoff on sea ice formation, a high resolution baroclinic 3-d circulation and sea ice model is applied to the Kara Sea. The model is forced with realistic atmospheric winds, surface heat fluxes, river runoff and tides. A vertical adaptive grid is used which provides high resolution in critical areas such as shallow estuaries, slopes or topographic obstacles. The surface following boundary layer is resolved uniformly in 4 m intervals in order to resolve the strong vertical stratification. The simulated melting rates are sensitive to the penetration depth of shortwave radia- tion into the water column. Peak runoff rates in the Kara Sea in spring might exceed 100.000 m3/s which causes high suspended loads in the water column and reduces the shortwave penetration depth considerably compared to ambient Arctic waters. As a result, coastal sea surface temperatures rise and ice melting is significantly enhanced. Our sensitivity studies show, that the indirect influence of river runoff on ice melting could play an important role in future studies on climate variability in the Arctic.

  15. Floating ice-algal aggregates below melting arctic sea ice.

    PubMed

    Assmy, Philipp; Ehn, Jens K; Fernández-Méndez, Mar; Hop, Haakon; Katlein, Christian; Sundfjord, Arild; Bluhm, Katrin; Daase, Malin; Engel, Anja; Fransson, Agneta; Granskog, Mats A; Hudson, Stephen R; Kristiansen, Svein; Nicolaus, Marcel; Peeken, Ilka; Renner, Angelika H H; Spreen, Gunnar; Tatarek, Agnieszka; Wiktor, Jozef

    2013-01-01

    During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year. PMID:24204642

  16. Floating Ice-Algal Aggregates below Melting Arctic Sea Ice

    PubMed Central

    Assmy, Philipp; Ehn, Jens K.; Fernández-Méndez, Mar; Hop, Haakon; Katlein, Christian; Sundfjord, Arild; Bluhm, Katrin; Daase, Malin; Engel, Anja; Fransson, Agneta; Granskog, Mats A.; Hudson, Stephen R.; Kristiansen, Svein; Nicolaus, Marcel; Peeken, Ilka; Renner, Angelika H. H.; Spreen, Gunnar; Tatarek, Agnieszka; Wiktor, Jozef

    2013-01-01

    During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year. PMID:24204642

  17. Inter-comparison of isotropic and anisotropic sea ice rheology in a fully coupled model

    NASA Astrophysics Data System (ADS)

    Roberts, A.; Cassano, J. J.; Maslowski, W.; Osinski, R.; Seefeldt, M. W.; Hughes, M.; Duvivier, A.; Nijssen, B.; Hamman, J.; Hutchings, J. K.; Hunke, E. C.

    2015-12-01

    We present the sea ice climate of the Regional Arctic System Model (RASM), using a suite of new physics available in the Los Alamos Sea Ice Model (CICE5). RASM is a high-resolution fully coupled pan-Arctic model that also includes the Parallel Ocean Program (POP), the Weather Research and Forecasting Model (WRF) and Variable Infiltration Capacity (VIC) land model. The model domain extends from ~45˚N to the North Pole and is configured to run at ~9km resolution for the ice and ocean components, coupled to 50km resolution atmosphere and land models. The baseline sea ice model configuration includes mushy-layer sea ice thermodynamics and level-ice melt ponds. Using this configuration, we compare the use of isotropic and anisotropic sea ice mechanics, and evaluate model performance using these two variants against observations including Arctic buoy drift and deformation, satellite-derived drift and deformation, and sea ice volume estimates from ICESat. We find that the isotropic rheology better approximates spatial patterns of thickness observed across the Arctic, but that both rheologies closely approximate scaling laws observed in the pack using buoys and RGPS data. A fundamental component of both ice mechanics variants, the so called Elastic-Viscous-Plastic (EVP) and Anisotropic-Elastic-Plastic (EAP), is that they are highly sensitive to the timestep used for elastic sub-cycling in an inertial-resolving coupled framework, and this has a significant affect on surface fluxes in the fully coupled framework.

  18. Maintenance of the Sea-Ice Edge.

    NASA Astrophysics Data System (ADS)

    Bitz, C. M.; Holland, M. M.; Hunke, E. C.; Moritz, R. E.

    2005-08-01

    A coupled global climate model is used to evaluate processes that determine the equilibrium location of the sea-ice edge and its climatological annual cycle. The extent to which the wintertime ice edge departs from a symmetric ring around either pole depends primarily on coastlines, ice motion, and the melt rate at the ice-ocean interface. At any location the principal drivers of the oceanic heat flux that melts sea ice are absorbed solar radiation and the convergence of heat transported by ocean currents. The distance between the ice edge and the pole and the magnitude of the ocean heat flux convergence at the ice edge are inversely related. The chief exception to this rule is in the East Greenland Current, where the ocean heat flux convergence just east of the ice edge is relatively high but ice survives due to its swift southward motion and the protection of the cold southward-flowing surface water. In regions where the ice edge extends relatively far equatorward, absorbed solar radiation is the largest component of the ocean energy budget, and the large seasonal range of insolation causes the ice edge to traverse a large distance. In contrast, at relatively high latitudes, the ocean heat flux convergence is the largest component and it has a relatively small annual range, so the ice edge traverses a much smaller distance there. When the model is subject to increased CO2 forcing up to twice preindustrial levels, the ocean heat flux convergence weakens near the ice edge in most places. This weakening reduces the heat flux from the ocean to the base of the ice and tends to offset the effects of increased radiative forcing at the ice surface, so the ice edge retreats less than it would otherwise.

  19. Comparison Graph of Sea Ice Minimum - 2010

    NASA Video Gallery

    This animated graph tracks the retreat of sea ice, measured in millions of square kilometers, averaged from the start of the satellite record in 1979 through 2000 (white). Next, the graph follows t...

  20. Approaching the 2015 Arctic Sea Ice Minimum

    NASA Video Gallery

    As the sun sets over the Arctic, the end of this year’s melt season is quickly approaching and the sea ice cover has already shrunk to the fourth lowest in the satellite record. With possibly some ...

  1. Sea Ice Thickness Comparison: 1979 vs 2013

    NASA Video Gallery

    This animation compares the difference in the area, volume and depth of the average September Arctic sea ice between 1979, shown in blue, and 2013, shown in orange. The data from these two years ha...

  2. Dynamics of Arctic sea ice discussed at workshop

    NASA Astrophysics Data System (ADS)

    Overland, James; Ukita, Jinro

    Sea ice is an interesting geophysical material: it behaves as a large-scale hardening plastic. Consider the impact of the sea-ice covers mechanical behavior on the energy and momentum exchange within the complex atmosphere-ice-ocean system. Sea ice acts as an insulator between the relatively warm ocean water and the cold polar atmosphere. Sea ice cover interacts with the atmosphere by regulating air-sea fluxes, changing surface albedo, and influencing the long-wave radiative balance.

  3. Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins

    NASA Astrophysics Data System (ADS)

    Voigt, A.; Abbot, D. S.

    2012-07-01

    The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO2, SI)*, differs greatly among climate models. Here, we revisit the initiation of a Snowball Earth in the atmosphere-ocean general circulation model ECHAM5/MPI-OM for Marinoan (~630 Ma) continents and solar insolation decreased to 94%. In its standard setup, ECHAM5/MPI-OM initiates a Snowball Earth much more easily than other climate models at (CO2, SI)* ≈ (500 ppm, 55%). Previous work has shown that the Snowball Earth bifurcation can be pushed equatorward if a low bare sea ice albedo is assumed because bare sea ice is exposed by net evaporation in the descent region of the Hadley circulation. Consistent with this, when we replace the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO2, SI)* ≈ (204 ppm, 70%). When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a much lower CO2: (CO2, SI)* ≈ (2 ppm, 85%). Therefore, both lowering the bare sea-ice albedo and disabling sea-ice dynamics increase the critical sea-ice cover in ECHAM5/MPI-OM, but sea-ice dynamics have a much larger influence on the critical CO2. For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no Jormungand bifurcation between this Jormungand-like state and states with mid-latitude sea-ice margins. Our results indicate that differences in sea-ice dynamics schemes can be as important as sea ice albedo for causing the spread in climate model's estimates of the location of the Snowball Earth bifurcation.

  4. Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins

    NASA Astrophysics Data System (ADS)

    Voigt, A.; Abbot, D. S.

    2012-12-01

    The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO2, SI)*, differs greatly among climate models. Here, we study the effect of bare sea-ice albedo, sea-ice dynamics and ocean heat transport on (CO2, SI)* in the atmosphere-ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma) continents and solar insolation (94% of modern). In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO2, SI)* ≈ (500 ppm, 55%). Replacing the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO2, SI)* ≈ (204 ppm, 70%). This is consistent with previous work and results from net evaporation and local melting near the sea-ice margin. When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO2: (CO2, SI)* ≈ (2 ppm, 85%). Therefore, the simulation of sea-ice dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO2 for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-ice cover and only slightly decreases the critical CO2. For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-ice cover therefore is a soft Snowball state rather than a true Jormungand state. Overall, our results demonstrate that differences in sea-ice dynamics schemes can be at least as important as differences in sea-ice albedo for

  5. The implementation of sea ice model on a regional high-resolution scale

    NASA Astrophysics Data System (ADS)

    Prasad, Siva; Zakharov, Igor; Bobby, Pradeep; McGuire, Peter

    2015-09-01

    The availability of high-resolution atmospheric/ocean forecast models, satellite data and access to high-performance computing clusters have provided capability to build high-resolution models for regional ice condition simulation. The paper describes the implementation of the Los Alamos sea ice model (CICE) on a regional scale at high resolution. The advantage of the model is its ability to include oceanographic parameters (e.g., currents) to provide accurate results. The sea ice simulation was performed over Baffin Bay and the Labrador Sea to retrieve important parameters such as ice concentration, thickness, ridging, and drift. Two different forcing models, one with low resolution and another with a high resolution, were used for the estimation of sensitivity of model results. Sea ice behavior over 7 years was simulated to analyze ice formation, melting, and conditions in the region. Validation was based on comparing model results with remote sensing data. The simulated ice concentration correlated well with Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Ocean and Sea Ice Satellite Application Facility (OSI-SAF) data. Visual comparison of ice thickness trends estimated from the Soil Moisture and Ocean Salinity satellite (SMOS) agreed with the simulation for year 2010-2011.

  6. Sea Ice Thickness Variability in Fram Strait

    NASA Astrophysics Data System (ADS)

    Gerland, S.; Renner, A.; Haas, C.; Nicolaus, M.; Granskog, M.; Hansen, E.; Hendricks, S.; Hudson, S. R.; Beckers, J.; Goodwin, H.

    2011-12-01

    On this poster, we show results from airborne electromagnetic (EM) sea ice thickness measurements demonstrating the temporal and spatial complexity of the ice thickness distribution in Fram Strait between Greenland and Svalbard. Knowledge about the spatial and temporal sea ice thickness distribution in the Arctic Ocean is necessary to assess the state of the sea-ice cover, and to understand relevant processes and changes. Since 2003, the Norwegian Polar Institute (NPI) has been conducting systematic in situ monitoring of sea ice thickness in the western Fram Strait, using both ground and airborne techniques. Fram Strait is a key region for large-scale ice dynamics in the Arctic. It represents the main export route for sea ice from the Arctic and the only deep strait connecting the interior Arctic Ocean and the rest of the world oceans. The ice thickness distribution in this region is the result of a combination of dynamic and thermodynamic sea ice processes. Transects for airborne EM observations were flown by NPI in spring 2005, 2008, and late summer 2010, and by the Alfred Wegener Institute in spring 2009. The regional ice thickness distributions are supplemented with ground measurements including snow thickness observations taken on ice stations during ship expeditions in spring 2005, 2007, and 2008 and annually in late summer from 2003 to 2011. From all these observations, we can show the differing characteristics of the thickness distributions in spring (2005, 2008, 2009) and late summer (2010) when the ice thickness is at its annual maximum (end of the freezing period) and minimum (end of the melting period), respectively. The ice thickness distribution can also vary spatially over short distances in north-south direction. Features such as the East Greenland Polynya, which varies in size for a given time from year to year, contribute to the spatial and temporal variability on the Greenlandic Shelf. In spring 2005, a gradient is visible across Fram Strait from

  7. Fram Strait sea ice outflow

    NASA Technical Reports Server (NTRS)

    Kwok, R.; Cunningham, G. F.; Pang, S. S.

    2004-01-01

    We summarize 24 years of ice export estimates and examine, over a 9-year record, the associated variability in the time-varying upward-looking sonar (ULS) thickness distributions of the Fram Strait. A more thorough assessment of the PMW (passive microwave) ice motion with 5 years of synthetic aperture radar (SAR)observations shows the uncertainties to be consistent with that found by Kwok and Rothrock [1999], giving greater confidence to the record of ice flux calculations.

  8. Recent changes in Antarctic Sea Ice.

    PubMed

    Turner, John; Hosking, J Scott; Bracegirdle, Thomas J; Marshall, Gareth J; Phillips, Tony

    2015-07-13

    In contrast to the Arctic, total sea ice extent (SIE) across the Southern Ocean has increased since the late 1970s, with the annual mean increasing at a rate of 186×10(3) km(2) per decade (1.5% per decade; p<0.01) for 1979-2013. However, this overall increase masks larger regional variations, most notably an increase (decrease) over the Ross (Amundsen-Bellingshausen) Sea. Sea ice variability results from changes in atmospheric and oceanic conditions, although the former is thought to be more significant, since there is a high correlation between anomalies in the ice concentration and the near-surface wind field. The Southern Ocean SIE trend is dominated by the increase in the Ross Sea sector, where the SIE is significantly correlated with the depth of the Amundsen Sea Low (ASL), which has deepened since 1979. The depth of the ASL is influenced by a number of external factors, including tropical sea surface temperatures, but the low also has a large locally driven intrinsic variability, suggesting that SIE in these areas is especially variable. Many of the current generation of coupled climate models have difficulty in simulating sea ice. However, output from the better-performing IPCC CMIP5 models suggests that the recent increase in Antarctic SIE may be within the bounds of intrinsic/internal variability. PMID:26032320

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Improving the WRF model's simulation over sea ice surface through coupling with a complex thermodynamic sea ice model

    NASA Astrophysics Data System (ADS)

    Yao, Y.; Huang, J.; Luo, Y.; Zhao, Z.

    2015-12-01

    Sea ice plays an important role in the air-ice-ocean interaction, but it is often represented simply in many regional atmospheric models. The Noah sea ice model, which has been widely used in the Weather Research and Forecasting (WRF) model, exhibits cold bias in simulating the Arctic sea ice temperature when validated against the Surface Heat Budget of the Arctic Ocean (SHEBA) in situ observations. According to sensitivity tests, this bias is attributed not only to the simulation of snow depth and turbulent fluxes but also to the heat conduction within snow and ice. Compared with the Noah sea ice model, the high-resolution thermodynamic snow and ice model (HIGHTSI) has smaller bias in simulating the sea ice temperature. HIGHTSI is further coupled with the WRF model to evaluate the possible added value from better resolving the heat transport and solar penetration in sea ice from a complex thermodynamic sea ice model. The cold bias in simulating the surface temperature over sea ice in winter by the original Polar WRF is reduced when HIGHTSI rather than Noah is coupled with the WRF model, and this also leads to a better representation of surface upward longwave radiation and 2 m air temperature. A discussion on the impact of specifying sea ice thickness in the WRF model is presented. Consistent with previous research, prescribing the sea ice thickness with observational information would result in the best simulation among the available methods. If no observational information is available, using an empirical method based on the relationship between sea ice concentration and sea ice thickness could mimic the large-scale spatial feature of sea ice thickness. The potential application of a thermodynamic sea ice model in predicting the change in sea ice thickness in a RCM is limited by the lack of sea ice dynamic processes in the model and the coarse assumption on the initial value of sea ice thickness.

  11. Sea Ice on the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Jacobs, Stanley S.

    1998-01-01

    Year-round satellite records of sea ice distribution now extend over more than two decades, providing a valuable tool to investigate related characteristics and circulations in the Southern Ocean. We have studied a variety of features indicative of oceanic and atmospheric interactions with Antarctic sea ice. In the Amundsen & Bellingshausen Seas, sea ice extent was found to have decreased by approximately 20% from 1973 through the early 1990's. This change coincided with and probably contributed to recently warmer surface conditions on the west side of the Antarctic Peninsula, where air temperatures have increased by approximately 0.5 C/decade since the mid-1940's. The sea ice decline included multiyear cycles of several years in length superimposed on high interannual variability. The retreat was strongest in summer, and would have lowered the regional mean ice thickness, with attendant impacts upon vertical heat flux and the formation of snow ice and brine. The cause of the regional warming and loss of sea ice is believed to be linked to large-scale circulation changes in the atmosphere and ocean. At the eastern end of the Weddell Gyre, the Cosmonaut Polyna revealed greater activity since 1986, a recurrence pattern during recent winters and two possible modes of formation. Persistence in polynya location was noted off Cape Ann, where the coastal current can interact more strongly with the Antarctic Circumpolar Current. As a result of vorticity conservation, locally enhanced upwelling brings warmer deep water into the mixed layer, causing divergence and melting. In the Ross Sea, ice extent fluctuates over periods of several years, with summer minima and winter maxima roughly in phase. This leads to large interannual cycles of sea ice range, which correlate positively with meridinal winds, regional air temperatures and subsequent shelf water salinities. Deep shelf waters display considerable interannual variability, but have freshened by approximately 0.03/decade

  12. The Secret of the Svalbard Sea Ice Barrier

    NASA Technical Reports Server (NTRS)

    Nghiem, Son V.; Van Woert, Michael L.; Neumann, Gregory

    2004-01-01

    An elongated sea ice feature called the Svalbard sea ice barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing navigation hazards. The secret of its formation lies in the bottom bathymetry that governs the distribution of cold Arctic waters masses, which impacts sea ice growth on the water surface.

  13. Arctic Sea Ice : Trends, Stability and Variability

    NASA Astrophysics Data System (ADS)

    Moon, W.; Wettlaufer, J. S.

    2014-12-01

    A stochastic Arctic sea-ice model is derived and analysed in detail to interpret the recent decay and associated variability of Arctic sea-ice under changes in radiative forcing. The approach begins from a deterministic model of the heat flux balance through the air/sea/ice system, which uses observed monthly-averaged heat fluxesto drive a time evolution of sea-ice thickness. This model reproduces the observed seasonal cycle of the ice cover and it is to this that stochastic noise--representing high frequency variability--is introduced.The model takes the form of a single periodic non-autonomous stochastic ordinary differential equation. The value of such a model is that it provides a relatively simple framework to examine the role of noise in the basic nonlinear interactions at play as transitions in the state of the ice cover (e.g., from perennial to seasonal) are approached. Moreover, the stability and the noise conspire to underlie the inter annual variability and how that variability changes as one approaches the deterministic bifurcations in the system.

  14. Laser Altimetry Sampling Strategies over Sea Ice

    NASA Technical Reports Server (NTRS)

    Farrell, Sinead L.; Markus, Thorsten; Kwok, Ron; Connor, Laurence

    2011-01-01

    With the conclusion of the science phase of the Ice, Cloud and land Elevation Satellite (ICESat) mission in late 2009, and the planned launch of ICESat-2 in late 2015, NASA has recently established the IceBridge program to provide continuity between missions. A major goal of IceBridge is to obtain a sea-ice thickness time series via airborne surveys over the Arctic and Southern Oceans. Typically two laser altimeters, the Airborne Topographic Mapper (ATM) and the Land, Vegetation and Ice Sensor (LVIS), are utilized during IceBridge flights. Using laser altimetry simulations of conventional analogue systems such as ICESat, LVIS and ATM, with the multi-beam system proposed for ICESat-2, we investigate differences in measurements gathered at varying spatial resolutions and the impact on sea-ice freeboard. We assess the ability of each system to reproduce the elevation distributions of two seaice models and discuss potential biases in lead detection and sea-surface elevation, arising from variable footprint size and spacing. The conventional systems accurately reproduce mean freeboard over 25km length scales, while ICESat-2 offers considerable improvements over its predecessor ICESat. In particular, its dense along-track sampling of the surface will allow flexibility in the algorithmic approaches taken to optimize the signal-to-noise ratio for accurate and precise freeboard retrieval.

  15. An optical model for the microwave properties of sea ice

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Larabee, J. K.

    1981-01-01

    The complex refractive index of sea ice is modeled and used to predict the microwave signatures of various sea ice types. Results are shown to correspond well with the observed values of the complex index inferred from dielectic constant and dielectric loss measurements performed in the field, and with observed microwave signatures of sea ice. The success of this modeling procedure vis a vis modeling of the dielectric properties of sea ice constituents used earlier by several others is explained. Multiple layer radiative transfer calculations are used to predict the microwave properties of first-year sea ice with and without snow, and multiyear sea ice.

  16. Towards Improving Sea Ice Predictabiity: Evaluating Climate Models Against Satellite Sea Ice Observations

    NASA Astrophysics Data System (ADS)

    Stroeve, J. C.

    2014-12-01

    The last four decades have seen a remarkable decline in the spatial extent of the Arctic sea ice cover, presenting both challenges and opportunities to Arctic residents, government agencies and industry. After the record low extent in September 2007 effort has increased to improve seasonal, decadal-scale and longer-term predictions of the sea ice cover. Coupled global climate models (GCMs) consistently project that if greenhouse gas concentrations continue to rise, the eventual outcome will be a complete loss of the multiyear ice cover. However, confidence in these projections depends o HoHoweon the models ability to reproduce features of the present-day climate. Comparison between models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 5 (CMIP5) and observations of sea ice extent and thickness show that (1) historical trends from 85% of the model ensemble members remain smaller than observed, and (2) spatial patterns of sea ice thickness are poorly represented in most models. Part of the explanation lies with a failure of models to represent details of the mean atmospheric circulation pattern that governs the transport and spatial distribution of sea ice. These results raise concerns regarding the ability of CMIP5 models to realistically represent the processes driving the decline of Arctic sea ice and to project the timing of when a seasonally ice-free Arctic may be realized. On shorter time-scales, seasonal sea ice prediction has been challenged to predict the sea ice extent from Arctic conditions a few months to a year in advance. Efforts such as the Sea Ice Outlook (SIO) project, originally organized through the Study of Environmental Change (SEARCH) and now managed by the Sea Ice Prediction Network project (SIPN) synthesize predictions of the September sea ice extent based on a variety of approaches, including heuristic, statistical and dynamical modeling. Analysis of SIO contributions reveals that when the

  17. Ice in Caspian Sea and Aral Sea, Kazakhstan

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this MODIS image from December 3, 2001, winter sea ice can be seen forming in the shallow waters of the northern Caspian (left) and Aral (upper right) Seas. Despite the inflow of the Volga River (upper left), the northern portion of the Caspian Sea averages only 17 ft in depth, and responds to the region's continental climate, which is cold in winter and hot and dry in the summer. The southern part of the Sea is deeper and remains ice-free throughout the winter. The dirty appearance of the ice may be due to sediment in the water, but may also be due to wind-driven dust. The wind in the region can blow at hurricane-force strength and can cause the ice to pile up in hummocks that are anchored to the sea bottom. The eastern portion of the Aral Sea is also beginning to freeze. At least two characteristics of the Aral Sea 'compete' in determining whether its waters will freeze. The Sea is shallow, which increases the likelihood of freezing, but it is also very salty, which means that lower temperatures are required to freeze it than would be required for fresh water. With average December temperatures of 18o F, it's clearly cold enough to allow ice to form. As the waters that feed the Aral Sea continue to be diverted for agriculture, the Sea becomes shallower and the regional climate becomes even more continental. This is because large bodies of water absorb and retain heat, moderating seasonal changes in temperature. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  18. Sea ice melting in the marginal ice zone.

    USGS Publications Warehouse

    Josberger, E.G.

    1983-01-01

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

  19. The sea ice thickness distribution in the northwestern Weddell Sea

    NASA Astrophysics Data System (ADS)

    Lange, M. A.; Eicken, H.

    1991-03-01

    We present new data on distribution of snow and sea ice thicknesses in the northwestern Weddell Sea. The data were obtained through direct measurements along 19 profiles, each approximately 100 m long on 17 different floes located between 54°-46°W and 59°-64°S. The overall probability density functions (PDFs) for ice thicknesses reflect the complex mixture of first-, second-, and multi-year ice to be expected in the outflowing branch of the Weddell Gyre. Further differentiation of the data reveals four distinct thickness classes which reflect differences in the formation and subsequent histories of the ice encountered. These classes (I-IV) represent strongly deformed first year ice, less deformed first- and second-year ice, and deformed second- or multi-year ice, respectively. Each of the classes is characterized by a specific set of quantities related to ice texture and surface snow characteristics and by distinct PDFs for snow and ice thicknesses. In addition, geometric surface and bottom roughness characteristics differ significantly for each of the floe classes.

  20. Tropical pacing of Antarctic sea ice increase

    NASA Astrophysics Data System (ADS)

    Schneider, D. P.

    2015-12-01

    One reason why coupled climate model simulations generally do not reproduce the observed increase in Antarctic sea ice extent may be that their internally generated climate variability does not sync with the observed phases of phenomena like the Pacific Decadal Oscillation (PDO) and ENSO. For example, it is unlikely for a free-running coupled model simulation to capture the shift of the PDO from its positive to negative phase during 1998, and the subsequent ~15 year duration of the negative PDO phase. In previously presented work based on atmospheric models forced by observed tropical SSTs and stratospheric ozone, we demonstrated that tropical variability is key to explaining the wind trends over the Southern Ocean during the past ~35 years, particularly in the Ross, Amundsen and Bellingshausen Seas, the regions of the largest trends in sea ice extent and ice season duration. Here, we extend this idea to coupled model simulations with the Community Earth System Model (CESM) in which the evolution of SST anomalies in the central and eastern tropical Pacific is constrained to match the observations. This ensemble of 10 "tropical pacemaker" simulations shows a more realistic evolution of Antarctic sea ice anomalies than does its unconstrained counterpart, the CESM Large Ensemble (both sets of runs include stratospheric ozone depletion and other time-dependent radiative forcings). In particular, the pacemaker runs show that increased sea ice in the eastern Ross Sea is associated with a deeper Amundsen Sea Low (ASL) and stronger westerlies over the south Pacific. These circulation patterns in turn are linked with the negative phase of the PDO, characterized by negative SST anomalies in the central and eastern Pacific. The timing of tropical decadal variability with respect to ozone depletion further suggests a strong role for tropical variability in the recent acceleration of the Antarctic sea ice trend, as ozone depletion stabilized by late 1990s, prior to the most

  1. Assimilation of sea ice motion in a finite-element sea ice model

    NASA Astrophysics Data System (ADS)

    Rollenhagen, K.; Timmermann, R.; Janjić, T.; SchröTer, J.; Danilov, S.

    2009-05-01

    A finite-element sea ice model (FESIM) is applied in a data assimilation study with the singular evolutive interpolated Kalman (SEIK) filter. The model has been configured for a regional Arctic domain and is forced with a combination of daily NCEP reanalysis data for 2-m air temperature and 10-m winds with monthly mean humidities from the ECMWF reanalysis and climatological fields for precipitation and cloudiness. We assimilate 3-day mean ice drift fields derived from passive microwave satellite data. Based on multivariate covariances (which describe the statistical relationship between anomalies in different model fields), the sea ice drift data assimilation produces not only direct modifications of the ice drift but also updates for sea ice concentration and thickness, which in turn yield sustainable corrections of ice drift. We use observed buoy trajectories as an independent data set to validate the analyzed sea ice drift field. A good agreement between modeled and observed tracks is achieved already in the reference simulation. Application of the SEIK filter with satellite-derived drift fields further improves the agreement. Spatial and temporal variability of ice thickness increases due to the assimilation procedure; a comparison to thickness data from a submarine-based upward looking sonar indicates that the thickness distribution becomes more realistic. Validation with regard to satellite data shows that the velocity data assimilation has only a small effect on ice concentration, but a general improvement of the ice concentration within the pack is still evident.

  2. Fram Strait sea ice outflow

    NASA Technical Reports Server (NTRS)

    Kwok, R.; Cunningham, G. F.; Pang, S. S.

    2004-01-01

    We summarize 24 years (1978??2) of ice export estimates and examine, over a 9-year record, the associated variability in the time-varying upward-looking sonar (ULS) thickness distributions of the Fram Strait.

  3. Comparative Views of Arctic Sea Ice Growth

    NASA Technical Reports Server (NTRS)

    2000-01-01

    NASA researchers have new insights into the mysteries of Arctic sea ice, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts.

    Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete ice cover of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites.

    The two images above are separated by nine days (earlier image on the left). Both images represent an area (approximately 96 by 128 kilometers; 60 by 80 miles)located in the Baufort Sea, north of the Alaskan coast. The brighter features are older thicker ice and the darker areas show young, recently formed ice. Within the nine-day span, large and extensive cracks in the ice cover have formed due to ice movement. These cracks expose the open ocean to the cold, frigid atmosphere where sea ice grows rapidly and thickens.

    Using this new information, scientists at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., can generate comprehensive maps of Arctic sea ice thickness for the first time. 'Before we knew only the extent of the ice cover,' said Dr. Ronald Kwok, JPL principal investigator of a project called Sea Ice Thickness Derived From High Resolution Radar Imagery. 'We also knew that the sea ice extent had decreased over the last 20 years, but we knew very little about ice thickness.'

    'Since sea ice is very thin, about 3 meters (10 feet) or less,'Kwok explained, 'it is very sensitive to climate change.'

    Until now, observations of polar sea ice thickness have been available for specific areas, but not for the entire polar region.

    The new radar mapping technique has also given scientists a close look at

  4. Comparative Views of Arctic Sea Ice Growth

    NASA Technical Reports Server (NTRS)

    2000-01-01

    NASA researchers have new insights into the mysteries of Arctic sea ice, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts.

    Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete ice cover of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites.

    The two images above are separated by nine days (earlier image on the left). Both images represent an area (approximately 96 by 128 kilometers; 60 by 80 miles)located in the Baufort Sea, north of the Alaskan coast. The brighter features are older thicker ice and the darker areas show young, recently formed ice. Within the nine-day span, large and extensive cracks in the ice cover have formed due to ice movement. These cracks expose the open ocean to the cold, frigid atmosphere where sea ice grows rapidly and thickens.

    Using this new information, scientists at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., can generate comprehensive maps of Arctic sea ice thickness for the first time. 'Before we knew only the extent of the ice cover,' said Dr. Ronald Kwok, JPL principal investigator of a project called Sea Ice Thickness Derived From High Resolution Radar Imagery. 'We also knew that the sea ice extent had decreased over the last 20 years, but we knew very little about ice thickness.'

    'Since sea ice is very thin, about 3 meters (10 feet) or less,'Kwok explained, 'it is very sensitive to climate change.'

    Until now, observations of polar sea ice thickness have been available for specific areas, but not for the entire polar region.

    The new radar mapping technique has also given scientists a close look at

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  6. 2008 Arctic Sea Ice from AMSR-E

    NASA Video Gallery

    Sea ice is frozen seawater floating on the surface of the ocean. Some sea ice is semi-permanent, persisting from year to year, and some is seasonal, melting and refreezing from season to season. Th...

  7. Representation of Sea Ice Processes in State of the Art Earth System Models.

    NASA Astrophysics Data System (ADS)

    Bailey, D. A.; Holland, M. M.

    2015-12-01

    The majority of Earth System Models now include thermodynamic-dynamic sea ice models with a subgridscale representation of ice thickness. The current sea ice component of the Community Earth System Model is the Los Alamos sea ice model (CICE) version 5. This new version of the model includes prognostic salinity in the vertical thermodynamic calculation as well as a representation of melt pond drainage through the sea ice. The CICE5 also includes a melt pond parameterization that takes into account the deformed and non-deformed ice within a model grid cell. Snow on sea ice processes allow for an evolving effective snow grain radius as a function of temperature, which is used in the shortwave radiative transfer and surface albedo calculation. I will discuss the results from coupled climate model sensitivity simulations that consider the subgridscale representations of some of these processes. This will include analysis of mean state and feedbacks in both the Arctic and Antarctic. Additional discussion will be provided on how we have used observations to guide these efforts.

  8. The ASIBIA sea-ice facility: First results from the Atmosphere-Sea-Ice-Biogeochemistry in the Arctic chamber

    NASA Astrophysics Data System (ADS)

    France, James L.; Thomas, Max

    2016-04-01

    Working in the natural ocean-ice-atmosphere system is very difficult, as conducting fieldwork on sea-ice presents many challenges ice including costs, safety, experimental controls and access. The new ASIBIA (Atmosphere-Sea-Ice-Biogeochemistry in the Arctic) coupled Ocean-Sea-Ice-(Snow)-Atmosphere chamber facility at the University of East Anglia, UK, we are aiming to perform controlled first-year sea-ice investigations in areas such as sea-ice physics, physicochemical and biogeochemical processes in sea-ice and quantification of the bi-directional flux of gases in various states of first-year sea-ice conditions. The facility is a medium sized chamber with programmable temperatures from -55°C to +30°C, allowing a full range of first year sea-ice growing conditions in both the Arctic and Antarctic to be simulated. The water depth can be up to 1 m (including up to 25 cm of sea-ice) and an optional 1 m tall Teflon film atmosphere on top of the sea-ice, thus creating a closed and coupled ocean-sea-ice-atmosphere mesocosm. Ice growth in the tank is well suited for studying first-year sea-ice physical properties, with in-situ ice-profile measurements of temperature, salinity, conductivity, pressure and spectral light transmission. Underwater and above ice cameras are installed to record the physical development of the sea-ice. Here, we present the data from the first suites of experiments in the ASIBIA chamber focussing on sea-ice physics and give a brief description of the capabilities of the facility going forward. The ASIBIA chamber was funded as part of an ERC consolidator grant to the late Prof. Roland von Glasow and we hope this work and further development of the facility will act as a lasting legacy.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  10. Predicting September sea ice: Ensemble skill of the SEARCH Sea Ice Outlook 2008-2013

    NASA Astrophysics Data System (ADS)

    Stroeve, Julienne; Hamilton, Lawrence C.; Bitz, Cecilia M.; Blanchard-Wrigglesworth, Edward

    2014-04-01

    Since 2008, the Study of Environmental Arctic Change Sea Ice Outlook has solicited predictions of September sea-ice extent from the Arctic research community. Individuals and teams employ a variety of modeling, statistical, and heuristic approaches to make these predictions. Viewed as monthly ensembles each with one or two dozen individual predictions, they display a bimodal pattern of success. In years when observed ice extent is near its trend, the median predictions tend to be accurate. In years when the observed extent is anomalous, the median and most individual predictions are less accurate. Statistical analysis suggests that year-to-year variability, rather than methods, dominate the variation in ensemble prediction success. Furthermore, ensemble predictions do not improve as the season evolves. We consider the role of initial ice, atmosphere and ocean conditions, and summer storms and weather in contributing to the challenge of sea-ice prediction.

  11. Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

    USGS Publications Warehouse

    Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

    2010-01-01

    Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

  12. Weddell Sea exploration from ice station

    NASA Astrophysics Data System (ADS)

    Ice Station Weddell Group of Principal Investigators; Chief Scientists; Gordon, Arnold L.

    On January 18, 1915, the Endurance and Sir Ernest Shackleton and his crew were stranded in the ice of the Weddell Sea and began one of the most famous drifts in polar exploration. Shackleton turned a failure into a triumph by leading all of his team to safety [Shackleton, 1919]. The drift track of the Endurance and the ice floe occupied by her stranded crew after the ship was lost on November 21, 1915, at 68°38.5‧S and 52°26.5‧W, carried the group along the western rim of the Weddell Gyre, representing a rare human presence in this region of perennial sea-ice cover.Seventy-seven years later, in 1992, the first intentional scientific Southern Ocean ice drift station, Ice Station Weddell-1 (ISW-1), was established in the western Weddell Sea by a joint effort of the United States and Russia. ISW-1 followed the track of the Endurance closely (Figure 1) and gathered an impressive array of data in this largely unexplored corner of the Southern Ocean, the western edge of the Weddell Gyre.

  13. Constraining the parameters of the EAP sea ice rheology from satellite observations and discrete element model

    NASA Astrophysics Data System (ADS)

    Tsamados, Michel; Heorton, Harry; Feltham, Daniel; Muir, Alan; Baker, Steven

    2016-04-01

    The new elastic-plastic anisotropic (EAP) rheology that explicitly accounts for the sub-continuum anisotropy of the sea ice cover has been implemented into the latest version of the Los Alamos sea ice model CICE. The EAP rheology is widely used in the climate modeling scientific community (i.e. CPOM stand alone, RASM high resolution regional ice-ocean model, MetOffice fully coupled model). Early results from sensitivity studies (Tsamados et al, 2013) have shown the potential for an improved representation of the observed main sea ice characteristics with a substantial change of the spatial distribution of ice thickness and ice drift relative to model runs with the reference visco-plastic (VP) rheology. The model contains one new prognostic variable, the local structure tensor, which quantifies the degree of anisotropy of the sea ice, and two parameters that set the time scale of the evolution of this tensor. Observations from high resolution satellite SAR imagery as well as numerical simulation results from a discrete element model (DEM, see Wilchinsky, 2010) have shown that these individual floes can organize under external wind and thermal forcing to form an emergent isotropic sea ice state (via thermodynamic healing, thermal cracking) or an anisotropic sea ice state (via Coulombic failure lines due to shear rupture). In this work we use for the first time in the context of sea ice research a mathematical metric, the Tensorial Minkowski functionals (Schroeder-Turk, 2010), to measure quantitatively the degree of anisotropy and alignment of the sea ice at different scales. We apply the methodology on the GlobICE Envisat satellite deformation product (www.globice.info), on a prototype modified version of GlobICE applied on Sentinel-1 Synthetic Aperture Radar (SAR) imagery and on the DEM ice floe aggregates. By comparing these independent measurements of the sea ice anisotropy as well as its temporal evolution against the EAP model we are able to constrain the

  14. Recent sea-ice reduction and possible causes

    NASA Astrophysics Data System (ADS)

    Park, Doo-Sun R.

    2016-04-01

    Arctic sea-ice extent has been rapidly declining since the late 20th century. Given the accelerating rate of the sea-ice decline, an ice-free Arctic Ocean is expected to occur within this century. This rapid sea-ice melting is attributable to various Arctic environmental changes, such as increased downward infrared radiation (IR), sea-ice preconditioning, temperate ocean water inflow, and sea-ice export. However, their relative contributions are uncertain. Assessing the relative contributions is essential for improving our prediction of the future state of the Arctic sea ice. Most of the previous research had focused on summer sea ice, which is however sensitive to previous winter sea ice, suggesting that winter sea-ice processes are also important for understanding sea-ice variability and its trend. Here we show, for the Arctic winter of 1979-2011, that a positive trend of downward IR accounts for nearly half of the sea-ice concentration (SIC) decline. Furthermore, we show that the Arctic downward IR increase is driven by horizontal atmospheric water flux into the Arctic, and not by evaporation from the Arctic Ocean. The rest of the SIC decline likely comes from warm ocean.

  15. Antarctic sea ice and temperature variations

    SciTech Connect

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

    1992-03-01

    Monthly antarctic station temperatures are used in conjunction with grids of sea ice coverage in order to evaluate temporal trends and the strength of associations between the two variables at lags of up to several seasons. The trends of temperature are predominantly positive in winter and summer, but predominantly negative in spring. The spatially aggregated trend of temperature is small but positive, while the corresponding trend of ice coverage is small but negative. Cross-correlations between concurrent anomalies of the two variables are negative over most of the continent and are strongest over the Antarctic Peninsula, especially in winter. In regions other than the Antarctic Peninsula, lag correlations between seasonal anomalies are generally stronger with ice lagging the summer temperatures and with ice leading the winter temperatures.

  16. Dynamic preconditioning of the September sea-ice extent minimum

    NASA Astrophysics Data System (ADS)

    Williams, James; Tremblay, Bruno; Newton, Robert; Allard, Richard

    2016-04-01

    There has been an increased interest in seasonal forecasting of the sea-ice extent in recent years, in particular the minimum sea-ice extent. We propose a dynamical mechanism, based on winter preconditioning through first year ice formation, that explains a significant fraction of the variance in the anomaly of the September sea-ice extent from the long-term linear trend. To this end, we use a Lagrangian trajectory model to backtrack the September sea-ice edge to any time during the previous winter and quantify the amount of sea-ice divergence along the Eurasian and Alaskan coastlines as well as the Fram Strait sea-ice export. We find that coastal divergence that occurs later in the winter (March, April and May) is highly correlated with the following September sea-ice extent minimum (r = ‑0.73). This is because the newly formed first year ice will melt earlier allowing for other feedbacks (e.g. ice albedo feedback) to start amplifying the signal early in the melt season when the solar input is large. We find that the winter mean Fram Strait sea-ice export anomaly is also correlated with the minimum sea-ice extent the following summer. Next we backtrack a synthetic ice edge initialized at the beginning of the melt season (June 1st) in order to develop hindcast models of the September sea-ice extent that do not rely on a-priori knowledge of the minimum sea-ice extent. We find that using a multi-variate regression model of the September sea-ice extent anomaly based on coastal divergence and Fram Strait ice export as predictors reduces the error by 41%. A hindcast model based on the mean DJFMA Arctic Oscillation index alone reduces the error by 24%.

  17. Variability of Arctic Sea Ice as Determined from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1999-01-01

    The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea ice now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea ice cover and its variability. The information includes data on ice concentrations (percent areal coverages of ice), ice extents, ice melt, ice velocities, the seasonal cycle of the ice, the interannual variability of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual variabilities, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum ice coverage. In spite of the large variations from year to year and region to region, overall the Arctic ice extents showed a statistically significant, 2.80% / decade negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual variability, along with spatially coherent overall trends. Linear least squares trends show the sea ice season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.

  18. Active microwave classification of sea ice

    NASA Technical Reports Server (NTRS)

    Onstott, Robert G.

    1989-01-01

    Radar backscatter studies of Arctic sea ice have been carried out over a number of years with the intent to acquire physical property information through the examination of microwave signatures. The breadth of these studies continues to expand; as an example, measurements are now conducted at frequencies from 500 MHz to about 100 GHz. One of the scientific goals of this work has been to develop an improved outstanding of the scattering processes at play. A second, equally important goal has been to apply the knowledge gained in examining the backscatter response of ice and snow made in conjunction with the detailed scene characterizations, the insight gained through theoretical modeling and parametric study, and the data entered into the radar signature library to develop procedures to convert microwave signal information (available in the very near future) into valuable data products. This should ultimately provide a better understanding of the environment. The author discusses what has been learned through the many efforts associated with the near-surface scatterometer measurement programs and how the knowledge gained is assisting in the development of future sea ice type satellite algorithms. The logic and mechanisms used in discriminating sea ice types are presented.

  19. The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice

    NASA Astrophysics Data System (ADS)

    Hoppmann, M.; Nicolaus, M.

    2011-12-01

    Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: a sub-ice layer of ice platelets and a highly stratified and thick snow cover. Ice platelets are flat, plate-like ice crystals forming and growing in a layer of super-cooled water which originates from ice shelf cavities. During growth, heat is lost to the super-cooled ocean rather than conducted to the atmosphere. The crystals accumulate beneath the solid sea-ice cover, forming a layer of loose platelets and eventually becoming incorporated into the sea-ice fabric as platelet ice. Considering the fact that the amount of platelet ice contributes between 10 and 60% to the mass of the land-fast sea ice around Antarctica, very little is known about its spatial and temporal variability. A thick and partly multi-year snow cover develops on top of the Antarctic fast ice, ultimately altering the sea-ice surface and affecting the sea-ice thermodynamics and mass balance. It typically leads to snow-ice formation, surface flooding, and the development of superimposed ice from snow melt water. In order to investigate the role of platelet ice and snow for Antarctic fast ice, we have initiated a regular observation program on the land-fast sea ice of Atka Bay as part of the international Antarctic Fast Ice Network (AFIN). We performed manual measurements of sea-ice and snow thicknesses from June to December 2010 and 2011. Additionally, a mass balance buoy and an automatic weather station were deployed in 2011 and ice cores were taken. Our measurements will reveal insight into the spatial and temporal variability of sea-ice and snow thickness distributions on Atka Bay fast ice. First results show that sea-ice thickness is lowest in the eastern part of the Bay, where a thick snow cover leads to extensive surface flooding. In the West, dynamic

  20. EOS Aqua AMSR-E Arctic Sea Ice Validation Program

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.; Markus, T.; Gasiewski, A.; Klein, M.; Maslanik, J.; Sturm, M.; Stroeve, J.; Heinrichs, J.

    2004-01-01

    A coordinated Arctic sea ice validation field campaign using the NASA Wallops P-3B aircraft was successfully completed in March 2003. This campaign was part of the program for validating the Earth Observing System (EOS) Aqua Advanced Microwave Scanning Radiometer (AMSR-E) sea ice products. The AMSR-E, designed and built by the Japanese National Space Development Agency for NASA, was launched May 4,2002 on the EOS Aqua spacecraft. The AMSR-E sea ice products include sea ice concentration, sea ice temperature, and snow depth on sea ice. The primary instrument on the P-3B aircraft was the NOAA ETL Polarimetric Scanning Radiometer (PSR) covering the same frequencies and polarizations as the AMSR-E. This paper describes the objectives of each of the seven flights, the Arctic regions overflown, and the coordination among satellite, aircraft, and surface-based measurements. Two of the seven aircraft flights were coordinated with scientists making surface measurements of snow and ice properties including sea ice temperature and snow depth on sea ice at a study area near Barrow, AK and at a Navy ice camp located in the Beaufort Sea. The remaining flights covered portions of the Bering Sea ice edge, the Chukchi Sea, and Norton Sound. Comparisons among the satellite and aircraft PSR data sets are presented.

  1. On the role of sea ice for Southern Ocean stratification

    NASA Astrophysics Data System (ADS)

    Haumann, F. Alexander; Münnich, Matthias; Gruber, Nicolas

    2013-04-01

    The formation, subsequent lateral transport, and melt of sea ice represents a key process for the determination of upper ocean stratification in the Southern Ocean. Sea ice is transported northward in large parts of the Southern Ocean by strong near-surface winds and melts along the ice edge south of the polar front, an important upwelling region. Here, it adds freshwater to the surface ocean, lowers the sea-water density, and possibly reduces upwelling by increasing the stratification. Consequently, this redistribution of freshwater in time and space affects the vertical overturning circulation which is an important determinant of the ocean-atmosphere CO2 exchange and, thus, of the global climate. We investigate the Southern Ocean sea-ice ocean system using satellite observations together with simulations with a newly developed regional ocean sea-ice model on the basis of ROMS. As it is not possible yet to derive sea-ice volume transport from remote sensing data due to a lack of ice thickness data, we quantify the freshwater flux exerted by the sea ice from the model and compare it to the observed sea-ice area transport. This shows that the transport is large in the Weddell and Ross Seas where sea ice extends to its lowest latitudes. We assess the importance of sea-ice freshwater transport on the stratification and circulation by comparing this flux to the net atmospheric freshwater flux from reanalysis data and by perturbing our model simulations.

  2. Sea Ice in the NCEP Climate Forecast System

    NASA Astrophysics Data System (ADS)

    Wu, X.; Grumbine, R. W.

    2015-12-01

    Sea ice is known to play a significant role in the global climate system. For a weather or climate forecast system (CFS), it is important that the realistic distribution of sea ice is represented. Sea ice prediction is challenging; sea ice can form or melt, it can move with wind and/or ocean current; sea ice interacts with both the air above and ocean underneath, it influences by, and has impact on the air and ocean conditions. NCEP has developed coupled CFS (version 2, CFSv2) and carried out CFS reanalysis (CFSR), which includes a coupled model with the NCEP global forecast system, a land model, an ocean model (GFDL MOM4), and a sea ice model. In this work, we present the NCEP coupled model, the CFSv2 sea ice component that includes a dynamic thermodynamic sea ice model and a simple "assimilation" scheme, how sea ice has been assimilated in CFSR, the characteristics of the sea ice from CFSR and CFSv2, and the improvements of sea ice needed for future CFS (version 3) and the CFSR.

  3. Space Radar Image of Weddell Sea Ice

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is the first calibrated, multi-frequency, multi-polarization spaceborne radar image of the seasonal sea-ice cover in the Weddell Sea, Antarctica. The multi-channel data provide scientists with details about the ice pack they cannot see any other way and indicates that the large expanse of sea-ice is, in fact, comprised of many smaller rounded ice floes, shown in blue-gray. These data are particularly useful in helping scientists estimate the thickness of the ice cover which is often extremely difficult to measure with other remote sensing systems. The extent, and especially thickness, of the polar ocean's sea-ice cover together have important implications for global climate by regulating the loss of heat from the ocean to the cold polar atmosphere. The image was acquired on October 3, 1994, by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour. This image is produced by overlaying three channels of radar data in the following colors: red (C-band, HH-polarization), green (L-band HV-polarization), and blue (L-band, HH-polarization). The image is oriented almost east-west with a center location of 58.2 degrees South and 21.6 degrees East. Image dimensions are 45 kilometers by 18 kilometers (28 miles by 11 miles). Most of the ice cover is composed of rounded, undeformed blue-gray floes, about 0.7 meters (2 feet) thick, which are surrounded by a jumble of red-tinged deformed ice pieces which are up to 2 meters (7 feet) thick. The winter cycle of ice growth and deformation often causes this ice cover to split apart, exposing open water or 'leads'. Ice growth within these openings is rapid due to the cold, brisk Antarctic atmosphere. Different stages of new-ice growth can be seen within the linear leads, resulting from continuous opening and closing. The blue lines within the leads are open water areas in new fractures which are roughened by wind. The bright red lines are an intermediate stage of new-ice

  4. Estimation of Antarctic Sea Ice Thickness From Satellite Radar Altimetry

    NASA Astrophysics Data System (ADS)

    Potter, R. C. H.; Laxon, S. W.; Peacock, N.

    The spatial and temporal variability of Antarctic sea-ice extent and thickness are re- quired by the climate modelling community to understand the complex coupling be- tween sea ice and ocean-atmosphere. Recent investigations have provided estimates of Arctic sea ice thickness determined from satellite radar altimetry, which have been validated using Upward Looking Sonar data from submarines. In the present study, we aim to explore the potential for estimation of the thickness of Antarctic sea ice. In the boreal summer, the Arctic Ocean is pre-dominantly inhabited by old, multiyear sea-ice that may survive through each melt season and subsequently refreeze and in- crease in thickness under autumn cooling and winter growth. However, aside from the Weddell Sea, the Antarctic sea ice is subject to almost complete seasonal melt/freeze with the formation of pre-dominant first year ice. To estimate ice thickness from mea- surements of ice elevation it is necessary to establish the vertical origin of the radar echo's received over snow covered ice. Assuming reflection originates at the snow/ice interface, the ice freeboard can be estimated. The freeboard is converted to ice thick- ness using fixed densities for ice and seawater and a recently generated Antarctic Snow depth climatology. However, the developed altimetry techniques are designed for rela- tively thick Arctic sea ice and therefore may not be directly applicable to the relatively thin non-compacted first year Antarctic sea ice. In particular, snow loading owing to high precipitation rates is likely to be much larger compared to ice thickness. In ex- treme conditions this may lead to negative freeboard. Nevertheless, data on Antarctic ice thickness is even more sparse than the Arctic and hence information on thickness would be of significant value. We present preliminary results of Antarctic ice thickness estimates and validation using ULS data.

  5. Sea ice density estimation in the Bohai Sea using the hyperspectral remote sensing technology

    NASA Astrophysics Data System (ADS)

    Liu, Chengyu; Shao, Honglan; Xie, Feng; Wang, Jianyu

    2014-11-01

    Sea ice density is one of the significant physical properties of sea ice and the input parameters in the estimation of the engineering mechanical strength and aerodynamic drag coefficients; also it is an important indicator of the ice age. The sea ice in the Bohai Sea is a solid, liquid and gas-phase mixture composed of pure ice, brine pockets and bubbles, the density of which is mainly affected by the amount of brine pockets and bubbles. The more the contained brine pockets, the greater the sea ice density; the more the contained bubbles, the smaller the sea ice density. The reflectance spectrum in 350~2500 nm and density of sea ice of different thickness and ages were measured in the Liaodong Bay of the Bohai Sea during the glacial maximum in the winter of 2012-2013. According to the measured sea ice density and reflectance spectrum, the characteristic bands that can reflect the sea ice density variation were found, and the sea ice density spectrum index (SIDSI) of the sea ice in the Bohai Sea was constructed. The inversion model of sea ice density in the Bohai Sea which refers to the layer from surface to the depth of penetration by the light was proposed at last. The sea ice density in the Bohai Sea was estimated using the proposed model from Hyperion image which is a hyperspectral image. The results show that the error of the sea ice density inversion model is about 0.0004 g•cm-3. The sea ice density can be estimated through hyperspectral remote sensing images, which provide the data support to the related marine science research and application.

  6. Arctic sea ice decline and ice export in the CMIP5 historical simulations

    NASA Astrophysics Data System (ADS)

    Langehaug, H. R.; Geyer, F.; Smedsrud, L. H.; Gao, Y.

    2013-11-01

    Arctic sea ice properties and Fram Strait ice export from six CMIP5 Global Climate and Earth System Models are evaluated and investigated for the period 1957-2005. Over the last decades most ensemble members simulate a decreasing September sea ice area and a slow, general thinning of the sea ice cover. While the different ensemble members both under- and overestimate the decline in observed September sea ice area, none of the members reproduce the observed thinning. This study is a first attempt to evaluate the Fram Strait ice area export in the CMIP5 models, and the role it has played for Arctic sea ice area and thickness. Five of the six models evaluated reproduce the seasonal cycle and the inter-annual variance of the ice area export in the Fram Strait reasonably well. The simulated southward export of sea ice in the Fram Strait constitutes a major fraction of the Arctic sea ice in these five models; 10-18% of the sea ice covered Arctic Basin is annually exported. For the same models the year-to-year variability in Fram Strait ice volume export carries 35% of the year-to-year variability in the Arctic Basin sea ice volume. We have found low but significant correlations on inter-annual timescales between the Fram Strait ice export, both in terms of area and volume, and the Arctic Basin sea ice thickness. All six models show that an increase in ice area export leads a decrease in the sea ice thickness. This inverse relationship also holds when considering the long-term trends; the larger the increase in Fram Strait ice area export, the larger the thinning of the Arctic Basin sea ice cover and the larger the loss in the September sea ice area. The different ensemble members show both negative and positive ice export trends. Focusing on the model with the largest number of ensemble members (10), we have been able to quantify the effect of the ice area export on the Arctic Basin sea ice for this particular model. For this model an increase of the ice area export

  7. Multifractals, random walks and Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Agarwal, Sahil; Wettlaufer, John

    We examine the long-term correlations and multifractal properties of daily satellite retrievals of Arctic sea ice albedo, extent, and ice velocity for decadal periods. The approach harnesses a recent development called Multifractal Temporally Weighted Detrended Fluctuation Analysis (MF-TWDFA), which exploits the intuition that points closer in time are more likely to be related than distant points. In both data sets we extract multiple crossover times, as characterized by generalized Hurst exponents, ranging from synoptic to decadal. The method goes beyond treatments that assume a single decay scale process, such as a first-order autoregression, which cannot be justifiably fit to these observations. The ice extent data exhibits white noise behavior from seasonal to bi-seasonal time scales, whereas the clear fingerprints of the short (weather) and long (~ 7 and 9 year) time scales remain, the latter associated with the recent decay in the ice cover. Thus, long term persistence is reentrant beyond the seasonal scale and it is not possible to distinguish whether a given ice extent minimum/maximum will be followed by a minimum/maximum that is larger or smaller in magnitude. The ice velocity data show long term persistence in auto covariance. NASA Grant NNH13ZDA001N-CRYO and Swedish Research Council Grant No. 638-2013-9243.

  8. Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications

    NASA Astrophysics Data System (ADS)

    DeWeaver, Eric T.; Bitz, Cecilia M.; Tremblay, L.-Bruno

    This volume addresses the rapid decline of Arctic sea ice, placing recent sea ice decline in the context of past observations, climate model simulations and projections, and simple models of the climate sensitivity of sea ice. Highlights of the work presented here include • An appraisal of the role played by wind forcing in driving the decline; • A reconstruction of Arctic sea ice conditions prior to human observations, based on proxy data from sediments; • A modeling approach for assessing the impact of sea ice decline on polar bears, used as input to the U.S. Fish and Wildlife Service's decision to list the polar bear as a threatened species under the Endangered Species Act; • Contrasting studies on the existence of a "tipping point," beyond which Arctic sea ice decline will become (or has already become) irreversible, including an examination of the role of the small ice cap instability in global warming simulations; • A significant summertime atmospheric response to sea ice reduction in an atmospheric general circulation model, suggesting a positive feedback and the potential for short-term climate prediction. The book will be of interest to researchers attempting to understand the recent behavior of Arctic sea ice, model projections of future sea ice loss, and the consequences of sea ice loss for the natural and human systems of the Arctic.

  9. Influence of stochastic sea ice parametrization on climate and the role of atmosphere-sea ice-ocean interaction.

    PubMed

    Juricke, Stephan; Jung, Thomas

    2014-06-28

    The influence of a stochastic sea ice strength parametrization on the mean climate is investigated in a coupled atmosphere-sea ice-ocean model. The results are compared with an uncoupled simulation with a prescribed atmosphere. It is found that the stochastic sea ice parametrization causes an effective weakening of the sea ice. In the uncoupled model this leads to an Arctic sea ice volume increase of about 10-20% after an accumulation period of approximately 20-30 years. In the coupled model, no such increase is found. Rather, the stochastic perturbations lead to a spatial redistribution of the Arctic sea ice thickness field. A mechanism involving a slightly negative atmospheric feedback is proposed that can explain the different responses in the coupled and uncoupled system. Changes in integrated Antarctic sea ice quantities caused by the stochastic parametrization are generally small, as memory is lost during the melting season because of an almost complete loss of sea ice. However, stochastic sea ice perturbations affect regional sea ice characteristics in the Southern Hemisphere, both in the uncoupled and coupled model. Remote impacts of the stochastic sea ice parametrization on the mean climate of non-polar regions were found to be small. PMID:24842027

  10. Role of ice dynamics in anomalous ice conditions in the Beaufort Sea during 2006 and 2007

    NASA Astrophysics Data System (ADS)

    Hutchings, J. K.; Rigor, I. G.

    2012-05-01

    A new record minimum in summer sea ice extent was set in 2007 and an unusual polynya formed in the Beaufort Sea ice cover during the summer of 2006. Using a combination of visual observations from cruises, ice drift, and satellite passive microwave sea ice concentration, we show that ice dynamics during preceding years included events that preconditioned the Beaufort ice pack for the unusual patterns of opening observed in both summers. Intrusions of first year ice from the Chukchi Sea to the Northern Beaufort, and increased pole-ward ice transport from the western Arctic during summer has led to reduced replenishment of multiyear ice, older than five years, in the western Beaufort, resulting in a younger, thinner ice pack in most of the Beaufort. We find ice younger than five years melts out completely by the end of summer, south of 76N. The 2006 unusual polynya was bounded to the south by an ice tongue composed of sea ice older than 5 years, and formed when first year and second year ice melted between 76N and the older ice to the south. In this paper we demonstrate that a recent shift in ice circulation patterns in the western Arctic preconditions the Beaufort ice pack for increased seasonal ice zone extent.

  11. Antarctic Sea Ice Variability and Trends, 1979-2010

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Cavalieri, D. J.

    2012-01-01

    In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978 - December 2010 reveal an overall positive trend in ice extents of 17,100 +/- 2,300 square km/yr. Much of the increase, at 13,700 +/- 1,500 square km/yr, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has, like the Arctic, instead experienced significant sea ice decreases, with an overall ice extent trend of -8,200 +/- 1,200 square km/yr. When examined through the annual cycle over the 32-year period 1979-2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9,100 +/- 6,300 square km/yr in February to a high of 24,700 +/- 10,000 square km/yr in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and Western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but differences in the magnitudes of the two trends identify regions with overall increasing ice concentrations and others with overall decreasing ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.

  12. Development of sea ice monitoring with aerial remote sensing technology

    NASA Astrophysics Data System (ADS)

    Jiang, Xuhui; Han, Lei; Dong, Liang; Cui, Lulu; Bie, Jun; Fan, Xuewei

    2014-11-01

    In the north China Sea district, sea ice disaster is very serious every winter, which brings a lot of adverse effects to shipping transportation, offshore oil exploitation, and coastal engineering. In recent years, along with the changing of global climate, the sea ice situation becomes too critical. The monitoring of sea ice is playing a very important role in keeping human life and properties in safety, and undertaking of marine scientific research. The methods to monitor sea ice mainly include: first, shore observation; second, icebreaker monitoring; third, satellite remote sensing; and then aerial remote sensing monitoring. The marine station staffs use relevant equipments to monitor the sea ice in the shore observation. The icebreaker monitoring means: the workers complete the test of the properties of sea ice, such as density, salinity and mechanical properties. MODIS data and NOAA data are processed to get sea ice charts in the satellite remote sensing means. Besides, artificial visual monitoring method and some airborne remote sensors are adopted in the aerial remote sensing to monitor sea ice. Aerial remote sensing is an important means in sea ice monitoring because of its strong maneuverability, wide watching scale, and high resolution. In this paper, several methods in the sea ice monitoring using aerial remote sensing technology are discussed.

  13. Annual primary production in Antarctic sea ice during 2005-2006 from a sea ice state estimate

    NASA Astrophysics Data System (ADS)

    Saenz, Benjamin T.; Arrigo, Kevin R.

    2014-06-01

    Using the data-bounded Sea Ice Ecosystem State (SIESTA) model, we estimate total Antarctic sea ice algal primary production to be 23.7 Tg C a-1 for the period July 2005-June 2006, of which 80% occurred in the bottom 0.2 m of ice. Simulated sea ice primary production would constitute 12% of total annual primary production in the Antarctic sea ice zone, and ˜1% of annual Southern Ocean primary production. Model sea ice algal growth was net nutrient limited, rather than light limited, for the vast majority of the sunlit season. The seasonal distribution of integrated ice algal biomass matches available observations. The vertical algal distribution was weighted toward the ice bottom compared to observations, indicating that interior ice algal communities may be under-predicted in the model, and that nutrient delivery via gravity-induced convection is not sufficient to sustain summertime algal biomass. Bottom ice algae were most productive in ice of 0.36 m thickness, whereas interior algal communities were most productive in ice of 1.10 m thickness. Sensitivity analyses that tested different atmospheric forcing inputs, sea ice parameterizations, and nutrient availability caused mean and regional shifts in sea ice state and ice algal production even when sea extent and motion was specified. The spatial heterogeneity of both ice state and algal production highlight the sensitivity of the sea ice ecosystem to physical perturbation, and demonstrate the importance of quality input data and appropriate parameterizations to models of sea ice and associated biology.

  14. Examining Differences in Arctic and Antarctic Sea Ice Change

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.; Rigor, I. G.; Clemente-Colon, P.; Neumann, G.; Li, P.

    2015-12-01

    The paradox of the rapid reduction of Arctic sea ice versus the stability (or slight increase) of Antarctic sea ice remains a challenge in the cryospheric science research community. Here we start by reviewing a number of explanations that have been suggested by different researchers and authors. One suggestion is that stratospheric ozone depletion may affect atmospheric circulation and wind patterns such as the Southern Annular Mode, and thereby sustaining the Antarctic sea ice cover. The reduction of salinity and density in the near-surface layer may weaken the convective mixing of cold and warmer waters, and thus maintaining regions of no warming around the Antarctic. A decrease in sea ice growth may reduce salt rejection and upper-ocean density to enhance thermohalocline stratification, and thus supporting Antarctic sea ice production. Melt water from Antarctic ice shelves collects in a cool and fresh surface layer to shield the surface ocean from the warmer deeper waters, and thus leading to an expansion of Antarctic sea ice. Also, wind effects may positively contribute to Antarctic sea ice growth. Moreover, Antarctica lacks of additional heat sources such as warm river discharge to melt sea ice as opposed to the case in the Arctic. Despite of these suggested explanations, factors that can consistently and persistently maintains the stability of sea ice still need to be identified for the Antarctic, which are opposed to factors that help accelerate sea ice loss in the Arctic. In this respect, using decadal observations from multiple satellite datasets, we examine differences in sea ice properties and distributions, together with dynamic and thermodynamic processes and interactions with land, ocean, and atmosphere, causing differences in Arctic and Antarctic sea ice change to contribute to resolving the Arctic-Antarctic sea ice paradox.

  15. Implementation of a Combined Elastic-Viscous-Plastic and Collisional Sea Ice Rheology

    NASA Astrophysics Data System (ADS)

    Rynders, Stefanie; Aksenov, Yevgeny; Feltham, Daniel

    2015-04-01

    The Marginal Ice Zone (MIZ) is a transitional area between the open ocean and pack ice. The MIZ is present in the Arctic and Southern Ocean and measures up to several hundred kilometers across. It is characterized by high surface ocean waves and consists of severely fragmented sea ice with ice floes less than 100m in diameter. With declining summer Arctic sea ice cover and increased wave heights in the Arctic Ocean, in the Arctic the MIZ widened by about 40 percent during the last three decades. The changes in sea ice and growing economic activity in the Polar Oceans necessitate new climate and forecasting models that can simulate the MIZ. Current models are not fit for the purpose since they do not model the surface ocean waves, which determine the MIZ width, or the sea ice rheology that represents MIZ ice dynamics. This study presents an implementation of collisional ice rheology that takes into account jostling of ice floes and also includes the effects of the ice floe distribution on internal ice stresses. The collisional contribution is derived from the magnitude of velocity fluctuations of ice floes. These are calculated from a kinetic energy evolution equation for the ice floes. Properties taken from a coupled wave-in-ice module determine the maximum floe size. This information is taken form a coupled wave-in-ice module. The rheology is derived in the framework of the Elastic-Viscous-Plastic rheology. This allows combination with the Elastic-Viscous-Plastic rheology and thus formulation of a unified sea ice rheology suitable for both the central pack ice and MIZ. The combined ice rheology is implemented in the Los Alamos CICE model and tested in the 2-degree resolution global NEMO Ocean General Circulation model. The 10-year run is forced by CORE2 climatological forcing. Prelimary results show that in the Arctic the new rheology decreases ice thicknesses near the coasts where ice is stationary. Overall, the change in the basin-scale Arctic ice thickness is

  16. Theory of the Sea Ice Thickness Distribution.

    PubMed

    Toppaladoddi, Srikanth; Wettlaufer, J S

    2015-10-01

    We use concepts from statistical physics to transform the original evolution equation for the sea ice thickness distribution g(h) from Thorndike et al. into a Fokker-Planck-like conservation law. The steady solution is g(h)=N(q)h(q)e(-h/H), where q and H are expressible in terms of moments over the transition probabilities between thickness categories. The solution exhibits the functional form used in observational fits and shows that for h≪1, g(h) is controlled by both thermodynamics and mechanics, whereas for h≫1 only mechanics controls g(h). Finally, we derive the underlying Langevin equation governing the dynamics of the ice thickness h, from which we predict the observed g(h). The genericity of our approach provides a framework for studying the geophysical-scale structure of the ice pack using methods of broad relevance in statistical mechanics. PMID:26551827

  17. Theory of the Sea Ice Thickness Distribution

    NASA Astrophysics Data System (ADS)

    Toppaladoddi, Srikanth; Wettlaufer, J. S.

    2015-10-01

    We use concepts from statistical physics to transform the original evolution equation for the sea ice thickness distribution g (h ) from Thorndike et al. into a Fokker-Planck-like conservation law. The steady solution is g (h )=N (q )hqe-h /H, where q and H are expressible in terms of moments over the transition probabilities between thickness categories. The solution exhibits the functional form used in observational fits and shows that for h ≪1 , g (h ) is controlled by both thermodynamics and mechanics, whereas for h ≫1 only mechanics controls g (h ). Finally, we derive the underlying Langevin equation governing the dynamics of the ice thickness h , from which we predict the observed g (h ). The genericity of our approach provides a framework for studying the geophysical-scale structure of the ice pack using methods of broad relevance in statistical mechanics.

  18. Sea Ice Microorganisms: Environmental Constraints and Extracellular Responses

    PubMed Central

    Ewert, Marcela; Deming, Jody W.

    2013-01-01

    Inherent to sea ice, like other high latitude environments, is the strong seasonality driven by changes in insolation throughout the year. Sea-ice organisms are exposed to shifting, sometimes limiting, conditions of temperature and salinity. An array of adaptations to survive these and other challenges has been acquired by those organisms that inhabit the ice. One key adaptive response is the production of extracellular polymeric substances (EPS), which play multiple roles in the entrapment, retention and survival of microorganisms in sea ice. In this concept paper we consider two main areas of sea-ice microbiology: the physico-chemical properties that define sea ice as a microbial habitat, imparting particular advantages and limits; and extracellular responses elicited in microbial inhabitants as they exploit or survive these conditions. Emphasis is placed on protective strategies used in the face of fluctuating and extreme environmental conditions in sea ice. Gaps in knowledge and testable hypotheses are identified for future research. PMID:24832800

  19. Arctic sea ice decline: Projected changes in timing and extent of sea ice in the Bering and Chukchi Seas

    USGS Publications Warehouse

    Douglas, D.C.

    2010-01-01

    The Arctic region is warming faster than most regions of the world due in part to increasing greenhouse gases and positive feedbacks associated with the loss of snow and ice cover. One consequence has been a rapid decline in Arctic sea ice over the past 3 decades?a decline that is projected to continue by state-of-the-art models. Many stakeholders are therefore interested in how global warming may change the timing and extent of sea ice Arctic-wide, and for specific regions. To inform the public and decision makers of anticipated environmental changes, scientists are striving to better understand how sea ice influences ecosystem structure, local weather, and global climate. Here, projected changes in the Bering and Chukchi Seas are examined because sea ice influences the presence of, or accessibility to, a variety of local resources of commercial and cultural value. In this study, 21st century sea ice conditions in the Bering and Chukchi Seas are based on projections by 18 general circulation models (GCMs) prepared for the fourth reporting period by the Intergovernmental Panel on Climate Change (IPCC) in 2007. Sea ice projections are analyzed for each of two IPCC greenhouse gas forcing scenarios: the A1B `business as usual? scenario and the A2 scenario that is somewhat more aggressive in its CO2 emissions during the second half of the century. A large spread of uncertainty among projections by all 18 models was constrained by creating model subsets that excluded GCMs that poorly simulated the 1979-2008 satellite record of ice extent and seasonality. At the end of the 21st century (2090-2099), median sea ice projections among all combinations of model ensemble and forcing scenario were qualitatively similar. June is projected to experience the least amount of sea ice loss among all months. For the Chukchi Sea, projections show extensive ice melt during July and ice-free conditions during August, September, and October by the end of the century, with high agreement

  20. Monthly average polar sea-ice concentration

    USGS Publications Warehouse

    Schweitzer, Peter N.

    1995-01-01

    The data contained in this CD-ROM depict monthly averages of sea-ice concentration in the modern polar oceans. These averages were derived from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) instruments aboard satellites of the U.S. Air Force Defense Meteorological Satellite Program from 1978 through 1992. The data are provided as 8-bit images using the Hierarchical Data Format (HDF) developed by the National Center for Supercomputing Applications.

  1. Sea ice and polar climate in the NCAR CSM

    SciTech Connect

    Weatherly, J.W.; Briegleb, B.P.; Large, W.G.; Maslanik, J.A.

    1998-06-01

    The Climate System Model (CSM) consists of atmosphere, ocean, land, and sea-ice components linked by a flux coupler, which computes fluxes of energy and momentum between components. The sea-ice component consists of a thermodynamic formulation for ice, snow, and leads within the ice pack, and ice dynamics using the cavitating-fluid ice rheology, which allows for the compressive strength of ice but ignores shear viscosity. The results of a 300-yr climate simulation are presented, with the focus on sea ice and the atmospheric forcing over sea ice in the polar regions. The atmospheric model results are compared to analyses from the European Centre for Medium-Range Weather Forecasts and other observational sources. The sea-ice concentrations and velocities are compared to satellite observational data. The atmospheric sea level pressure (SLP) in CSM exhibits a high in the central Arctic displaced poleward from the observed Beaufort high. The Southern Hemisphere SLP over sea ice is generally 5 mb lower than observed. Air temperatures over sea ice in both hemispheres exhibit cold biases of 2--4 K. The precipitation-minus-evaporation fields in both hemispheres are greatly improved over those from earlier versions of the atmospheric GCM.

  2. Modal Behavior of Hemispheric Sea Ice Covers

    NASA Technical Reports Server (NTRS)

    Gloersen, Per; Huang, Norden; Shen, Zheng

    1998-01-01

    Recent papers have described 18-year trends and annual oscillations in the Arctic and Antarctic sea ice extents, areas, and enclosed open water areas based on a newly-formulated 18.2-year ice concentration time series. This time series includes data for the entire Arctic and Antarctic ice covers, as well as for previously defined subregions consisting of 5 sectors in the Antarctic and 9 regions in the Arctic. It was obtained by fine-tuning the sea ice algorithm tie points individually for each of the four sensors used to acquire the data. In this paper, we extend these analyses to an examination of the intrinsic modes of these time series, obtained by means of Empirical Mode Decomposition, with emphasis on periodicities greater than the annual cycle. Quasibiennial and quasiquadrennial oscillations observed with a different technique and reported earlier for the first 8.8 years of this time series were also observed in the present series. However, the intrinsic modes were not monochromatic; they feature frequency as well as amplitude modulation within their respective frequency bands. Modal periods of up to 18 years are observed, with important implications for the trend analyses published earlier. These results are compared with the oscillations in the Length-of-Day and North Atlantic Oscillation parameters similarly determined for the same 18.2-year period.

  3. Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

    1995-01-01

    Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

  4. Polarimetric signatures of sea ice. 1: Theoretical model

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

    1995-01-01

    Physical, structral, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarmetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies to interpretation of sea ice polarimetric signatures.

  5. Validation and evaluation of a workstation for monitoring sea ice

    NASA Astrophysics Data System (ADS)

    McIntyre, Neil; Boardman, Diane; Darwin, David; Sullivan, Ken

    1994-12-01

    Demand for reliable sea ice information comes from many quarters including ship routing and resource exploitation companies, weather forecasting agencies and glaciological research institution. For operational purposes, this information is typically required for local regions on short timescales. To explore this market a prototype sea ice workstation has been developed. The workstation uses data from several current earth observation sensors, combining the advantages of regional survey, all-weather capability and high-resolution imagery. The output from the workstation is an integrated sea ice chart which can be used to display combinations of ice edge, ice type, ice concentrations, ice motion vectors and sea surface temperatures. During the course of its development significant new progress in automated ice classification has been achieved together with the enhancement of existing ice motion algorithms. The quality of the sea ice information from each geophysical algorithm was assessed through validation campaigns which collected independent datasets. The results of this analysis show the ice type classification to be most accurate in identifying multi-year ice; this is probably the most critical ice category for navigational purposes. A program of end-user evaluation has also been started in which sea ice charts are supplied to operational organizations and value-added services. This will continue during 1994 and provide feedback on the use of the workstation in a semi-operational environment.

  6. Modeling of Antarctic sea ice in a general circulation model

    SciTech Connect

    Wu, Xingren; Budd, W.F.; Simmonds, I.

    1997-04-01

    A dynamic-thermodynamic sea ice model is developed and coupled with the Melbourne University general circulation model to simulate the seasonal cycle of the Antarctic sea ice distributions The model is efficient, rapid to compute, and useful for a range of climate studies. The thermodynamic part of the sea ice model is similar to that developed by Parkinson and Washington, the dynamics contain a simplified ice rheology that resists compression. The thermodynamics is based on energy conservation at the top surface of the ice/snow, the ice/water interface, and the open water area to determine the ice formation, accretion, and ablation. A lead parameterization is introduced with an effective partitioning scheme for freezing between and under the ice floes. The dynamic calculation determines the motion of ice, which is forced with the atmospheric wind, taking account of ice resistance and rafting. The simulated sea ice distribution compares reasonably well with observations. The seasonal cycle of ice extent is well simulated in phase as well as in magnitude. Simulated sea ice thickness and concentration are also in good agreement with observations over most regions and serve to indicate the importance of advection and ocean drift in the determination of the sea ice distribution. 64 refs., 15 figs., 2 tabs.

  7. Radar image interpretation techniques applied to sea ice geophysical problems

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.

    1983-01-01

    The geophysical science problems in the sea ice area which at present concern understanding the ice budget, where ice is formed, how thick it grows and where it melts, and the processes which control the interaction of air-sea and ice at the ice margins is discussed. The science problems relate to basic questions of sea ice: how much is there, thickness, drift rate, production rate, determination of the morphology of the ice margin, storms feeling for the ice, storms and influence at the margin to alter the pack, and ocean response to a storm at the margin. Some of these questions are descriptive and some require complex modeling of interactions between the ice, the ocean, the atmosphere and the radiation fields. All involve measurements of the character of the ice pack, and SAR plays a significant role in the measurements.

  8. Storm-induced sea-ice breakup and the implications for ice extent.

    PubMed

    Kohout, A L; Williams, M J M; Dean, S M; Meylan, M H

    2014-05-29

    The propagation of large, storm-generated waves through sea ice has so far not been measured, limiting our understanding of how ocean waves break sea ice. Without improved knowledge of ice breakup, we are unable to understand recent changes, or predict future changes, in Arctic and Antarctic sea ice. Here we show that storm-generated ocean waves propagating through Antarctic sea ice are able to transport enough energy to break sea ice hundreds of kilometres from the ice edge. Our results, which are based on concurrent observations at multiple locations, establish that large waves break sea ice much farther from the ice edge than would be predicted by the commonly assumed exponential decay. We observed the wave height decay to be almost linear for large waves--those with a significant wave height greater than three metres--and to be exponential only for small waves. This implies a more prominent role for large ocean waves in sea-ice breakup and retreat than previously thought. We examine the wider relevance of this by comparing observed Antarctic sea-ice edge positions with changes in modelled significant wave heights for the Southern Ocean between 1997 and 2009, and find that the retreat and expansion of the sea-ice edge correlate with mean significant wave height increases and decreases, respectively. This includes capturing the spatial variability in sea-ice trends found in the Ross and Amundsen-Bellingshausen seas. Climate models fail to capture recent changes in sea ice in both polar regions. Our results suggest that the incorporation of explicit or parameterized interactions between ocean waves and sea ice may resolve this problem. PMID:24870546

  9. Sea ice concentration and sea ice drift for the Arctic summer using C- and L-band SAR

    NASA Astrophysics Data System (ADS)

    Johansson, Malin; Berg, Anders; Eriksson, Leif

    2014-05-01

    The decreasing amount of sea ice and changes from multi-year ice to first year ice within the Arctic Ocean opens up for increased maritime activities. These activities include transportation, fishing and tourism. One of the major threats for the shipping is the presence of sea ice. Should an oil spill occur, the search and rescue is heavily dependent on constant updates of sea ice movements, both to enable a safer working environment and to potentially prevent the oil from reaching the sea ice. It is therefore necessary to have accurate and updated sea ice charts for the Arctic Ocean during the entire year. During the melt season that ice is subject to melting conditions making satellite observations of sea ice more difficult. This period coincides with the peak in marine shipping activities and therefore requires highly accurate sea ice concentration estimates. Synthetic Aperture Radar (SAR) are not hindered by clouds and do not require daylight. The continuous record and high temporal resolution makes C-band data preferable as input data for operational sea ice mapping. However, with C-band SAR it is sometimes difficult to distinguish between a wet sea ice surface and surrounding open water. L-band SAR has a larger penetration depth and has been shown to be less sensitive to less sensitive than C-band to the melt season. Inclusion of L-band data into sea chart estimates during the melt season in particular could therefore improve sea ice monitoring. We compare sea ice concentration melt season observations using Advanced Land Observing Satellite (ALOS) L-band images with Envisat ASAR C-band images. We evaluate if L-band images can be used to improve separation of wet surface ice from open water and compare with results for C-band.

  10. Sea ice trends and cyclone activity in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Coggins, Jack; McDonald, Adrian; Rack, Wolfgang; Dale, Ethan

    2015-04-01

    Significant trends in the extent of Southern Hemisphere sea ice have been noted over the course of the satellite record, with highly variable trends between different seasons and regions. In this presentation, we describe efforts to assess the impact of cyclones on these trends. Employing a maximum cross-correlation method, we derive Southern Ocean ice-motion vectors from daily gridded SSMI 85.5 GHz brightness temperatures. We then derive a sea ice budget from the NASA-Team 25 km square daily sea ice concentrations. The budget quantifies the total daily change in sea ice area, and includes terms representing the effects of ice advection and divergence. A residual term represents the processes of rafting, ridging, freezing and thawing. We employ a cyclone tracking algorithm developed at the University of Canterbury to determine the timing, location, size and strength of Southern Hemisphere cyclones from mean sea-level pressure fields of the ERA-Interim reanalysis. We then form composites of the of sea ice budget below the location of cyclones. Unsurprisingly, we find that clockwise atmospheric flow around Southern Hemisphere cyclones exerts a strong influence on the movement of sea ice, an effect which is visible in the advection and divergence terms. Further, we assess the climatological importance of cyclones by comparing seasons of sea ice advance for periods with varying numbers of cyclones. This analysis is performed independently for each sea ice concentration pixel, thus affording us insight into the geographical importance of storm systems. We find that Southern Hemisphere sea ice extent is highly sensitive to the presence of cyclones in the periphery of the pack in the advance season. Notably, the sensitivity is particularly high in the northern Ross Sea, an area with a marked positive trend in sea ice extent. We discuss whether trends in cyclone activity in the Southern Ocean may have contributed to sea ice extent trends in this region.

  11. Mapping Arctic sea ice from the Earth Resources Technology Satellite

    NASA Technical Reports Server (NTRS)

    Barnes, J. C. (Principal Investigator); Bowley, C. J.

    1973-01-01

    The author has identified the following significant results. Methods of detecting ice and for distinguishing between ice and clouds are discussed, and examples of ERTS-1 data showing ice distributions in northern Hudson Bay, M'Clure Strait, the eastern Beaufort Sea, and the Greenland Sea are presented. The results of the initial analysis of ERTS-1 data indicate that the locations of ice edges and ice concentrations can be accurately mapped, and that considerable information on ice type can be derived through use of the various spectral bands. Ice features as small as 80 to 100 m width can be mapped.

  12. Combined Satellite - and ULS-Derived Sea-Ice Flux in the Weddell Sea

    NASA Technical Reports Server (NTRS)

    Drinkwater, M.; Liu, X.; Harms, S.

    2000-01-01

    Several years of daily microwave satellite ice-drift are combined with moored Upward Looking Sonar (ULS) ice-drafts into an ice volume flux record at points along a flux gate across the Weddell Sea, Antarctica.

  13. Arctic Sea Ice and Its Changes during the Satellite Period

    NASA Astrophysics Data System (ADS)

    Wang, X.; Liu, Y.; Key, J. R.

    2009-12-01

    Sea ice is a very important indicator and an effective modulator of regional and global climate change. Changes in sea ice will significantly affect the complex exchanges of momentum, heat, and mass between sea and the atmosphere, along with profound socio-economic influences due to its role in transportation, fisheries, hunting, polar animal habitat. Over the last two decades of the 20th century, the Arctic underwent significant changes in sea ice as part of the accelerated global warming of that period. More accurate, consistent, and detailed ice thickness, extent, and volume data are critical for a wide range of applications including climate change detection, climate modeling, and operational applications such as shipping and hazard mitigation. Satellite data provide an unprecedented opportunity to estimate and monitor Arctic sea ice routinely with relatively high spatial and temporal resolutions. In this study, a One-dimensional Thermodynamic Ice Model (OTIM) has been developed to estimate sea ice thickness based on the surface energy balance at a thermo-equilibrium state, containing all components of the surface energy balance. The OTIM has been extensively validated against submarine Upward-Looking Sonar (ULS) measurements, meteorological station measurements, and comprehensive numerical model simulations. Overall, OTIM-estimated sea ice thickness is accurate to within about 20% error when compared to submarine ULS ice thickness measurements and Canadian meteorological station measurements for ice less than 3 m. Along with sea ice extent information from the SSM/I, the Arctic sea ice volume can be estimated for the satellite period from 1984 to 2004. The OTIM has been used with satellite data from the extended Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP-x) products for the Arctic sea ice thickness, and sequentially sea ice volume estimations, and following statistical analysis of spatial and temporal distribution and trends in sea

  14. Influence of Sea Ice on Arctic Marine Sulfur Biogeochemistry in the Community Climate System Model

    SciTech Connect

    Deal, Clara; Jin, Meibing

    2013-06-30

    Global climate models (GCMs) have not effectively considered how responses of arctic marine ecosystems to a warming climate will influence the global climate system. A key response of arctic marine ecosystems that may substantially influence energy exchange in the Arctic is a change in dimethylsulfide (DMS) emissions, because DMS emissions influence cloud albedo. This response is closely tied to sea ice through its impacts on marine ecosystem carbon and sulfur cycling, and the ice-albedo feedback implicated in accelerated arctic warming. To reduce the uncertainty in predictions from coupled climate simulations, important model components of the climate system, such as feedbacks between arctic marine biogeochemistry and climate, need to be reasonably and realistically modeled. This research first involved model development to improve the representation of marine sulfur biogeochemistry simulations to understand/diagnose the control of sea-ice-related processes on the variability of DMS dynamics. This study will help build GCM predictions that quantify the relative current and possible future influences of arctic marine ecosystems on the global climate system. Our overall research objective was to improve arctic marine biogeochemistry in the Community Climate System Model (CCSM, now CESM). Working closely with the Climate Ocean Sea Ice Model (COSIM) team at Los Alamos National Laboratory (LANL), we added 1 sea-ice algae and arctic DMS production and related biogeochemistry to the global Parallel Ocean Program model (POP) coupled to the LANL sea ice model (CICE). Both CICE and POP are core components of CESM. Our specific research objectives were: 1) Develop a state-of-the-art ice-ocean DMS model for application in climate models, using observations to constrain the most crucial parameters; 2) Improve the global marine sulfur model used in CESM by including DMS biogeochemistry in the Arctic; and 3) Assess how sea ice influences DMS dynamics in the arctic marine

  15. The application of ERTS imagery to monitoring Arctic sea ice. [mapping ice in Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

    NASA Technical Reports Server (NTRS)

    Barnes, J. C. (Principal Investigator); Bowley, C. J.

    1974-01-01

    The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

  16. Sea ice pCO2 dynamics and air-ice CO2 fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment - Bellingshausen Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Geilfus, N.-X.; Tison, J.-L.; Ackley, S. F.; Galley, R. J.; Rysgaard, S.; Miller, L. A.; Delille, B.

    2014-12-01

    Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls the CO2 system in the ice. During the survey, cyclical warming and cooling strongly influenced the physical, chemical, and thermodynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the second site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We show that each cooling/warming event was associated with an increase/decrease in the brine salinity, total alkalinity (TA), total dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers reduced the amplitude of these changes: snow cover influences the sea ice carbonate system by modulating the temperature and therefore the salinity of the sea ice cover. Results indicate that pCO2 was undersaturated with respect to the atmosphere both in the in situ bulk ice (from 10 to 193 μatm) and brine (from 65 to 293 μatm), causing the sea ice to act as a sink for atmospheric CO2 (up to 2.9 mmol m-2 d-1), despite supersaturation of the underlying seawater (up to 462 μatm).

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

    NASA Astrophysics Data System (ADS)

    Riihelä, A.

    2015-12-01

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

  18. Optical properties of melting first-year Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Light, Bonnie; Perovich, Donald K.; Webster, Melinda A.; Polashenski, Christopher; Dadic, Ruzica

    2015-11-01

    The albedo and transmittance of melting, first-year Arctic sea ice were measured during two cruises of the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, ice physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first-year Arctic sea ice. Ponded ice was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare ice. The ubiquitous surface-scattering layer and drained layer present on bare, melting sea ice are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior. Bare ice reflects nearly three-quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded ice absorbs or transmits to the ocean more than three-quarters of the incident sunlight. Characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage, and light transmittance through ponded ice shows strong contrast between first-year and multiyear Arctic ice covers.

  19. Atmosphere - Sea Ice Coupling in the Navy's Global Coupled Modeling System: Diagnosing Polar Prediction using the sea ice models, CICE4 and CICE5, coupled with the NAVGEM Atmospheric Model.

    NASA Astrophysics Data System (ADS)

    Barton, N. P.; Chen, J.; Whitcomb, T.

    2015-12-01

    The United States Naval Research Laboratory is developing a global coupled model for sub-seasonal to seasonal predictions under the Earth System Prediction Capability national program. The Navy's full Earth System coupled model has a dynamic atmosphere, ocean, and sea ice. This presentation only examines atmosphere - sea ice coupling without using a dynamic ocean to isolate interactions. The Navy's Global Environmental Model (NAVGEM) is used for the atmospheric model and two versions of the Los Alamos National Laboratory's Community sea ICe Code (CICE version 4 and 5) are used for sea ice model. Data assimilative five day hindcasts are performed from March 2014 to September 2014 using NAVGEM-CICE4 and NAVGEM-CICE5 configurations. Differences in sea ice and low-level temperatures are examined in detail. The NAVGEM-CICE5 configuration results in a larger coverage of sea ice compared to the NAVGEM-CICE4 configuration, and this is consistent with thicker sea ice in the NAVGEM-CICE5 runs. Low-level temperatures in the NAVGEM-CICE4 are greater during Northern Hemisphere spring compared to the NAVGEM-CICE5 configuration. NAVGEM-CICE5 has larger albedos compared to the NAVGEM-CICE4 configuration and may be a primary cause in the lower low-level temperatures. Lastly, these results are discussed in relation to the stand-alone NAVGEM.

  20. 30-Year Satellite Record Reveals Accelerated Arctic Sea Ice Loss, Antarctic Sea Ice Trend Reversal

    NASA Technical Reports Server (NTRS)

    Cavalieri, Donald J.; Parkinson, C. L.; Vinnikov, K. Y.

    2003-01-01

    Arctic sea ice extent decreased by 0.30 plus or minus 0.03 x 10(exp 6) square kilometers per decade from 1972 through 2002, but decreased by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per decade from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast to the Arctic, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased, with an overall 30-year trend of -0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent observed in the early 1970's.

  1. The impact of under-ice melt ponds on Arctic sea ice volume

    NASA Astrophysics Data System (ADS)

    Smith, Naomi; Flocco, Daniela; Feltham, Daniel

    2016-04-01

    A one-dimensional, thermodynamic model of Arctic sea ice [Flocco et al, 2015] has been adapted to study the evolution of under-ice melt ponds, pools of fresh water that are found below the Arctic sea ice, and false bottoms, sheets of ice that form at the boundary between the under-ice melt pond and the oceanic mixed layer. Over time, either the under-ice melt pond freezes or the false bottom is completely ablated. We have been investigating the impact that these features have on the growth or ablation of sea ice during the time that they are present. The sensitivity of our model to a range of parameters has been tested, revealing some interesting effects of the thermodynamic processes taking place during the life-cycle of these phenomena. For example, the under-ice melt pond and its associated false bottom can insulate the sea ice layer from ocean, increasing the thickness of sea ice present at the end of the time frame considered. A comparison of the results of the model of under-ice melt pond evolution with that of sea ice with a bare base has been used to estimate the impact of under-ice melt ponds on sea ice volume towards the end of the melt season. We find that the under-ice melt ponds could have a significant impact on the mass balance of the sea ice, suggesting that it could be desirable to include a parameterisation of the effects of under-ice melt pond in the sea ice components of climate models.

  2. Evolution of a Coupled Marine Ice Sheet - Sea Level Model

    NASA Astrophysics Data System (ADS)

    Gomez, N.; Pollard, D.; Mitrovica, J. X.; Huybers, P.; Clark, P. U.

    2012-04-01

    An instability mechanism is widely predicted for marine ice sheets resting upon reversed bed slopes whereby ice-sheet thinning or rising sea level is thought to lead to irreversible retreat of the grounding line. Previous analyses of marine ice-sheet stability have considered the influence of a sea-level perturbation on ice-sheet stability by assuming a geographically uniform, or eustatic, change in sea level. However, gravitational, deformational and rotational effects associated with changes in the volume of grounded ice lead to markedly non-uniform spatial patterns of sea-level change. In particular, a gravitationally self-consistent sea-level theory predicts a sea-level fall in the vicinity of a shrinking ice sheet that is an order of magnitude greater amplitude than the sea-level rise that would be predicted assuming eustasy. We highlight the stabilizing influence of local sea-level changes on marine ice sheets by incorporating gravitationally self-consistent sea-level changes into a steady state model of ice sheet stability (Gomez et. al., Nature Geoscience, 2010). In addition, we develop a dynamic coupled ice sheet - sea level model to consider the impact of this stabilizing mechanism on the timescale of ice sheet retreat. The coupled system combines a sea-level model valid for a self-gravitating, viscoelastically deforming Earth to a 1D, dynamic marine ice sheet-shelf model. The evolution of the coupled model is explored for a suite of simulations in which we vary the bed slope and the forcing that initiates retreat. We find that the sea-level fall at the grounding line associated with a retreating ice sheet acts to slow the retreat; in simulations with shallow reversed bed slopes and/or small initial forcing, the drop in sea level can be sufficient to halt the retreat. The rate of sea-level change at the grounding line has an elastic component due to ongoing changes in ice-sheet geometry, and a viscous component due to past ice and ocean load changes. When

  3. A destabilizing thermohaline circulation-atmosphere-sea ice feedback

    SciTech Connect

    Jayne, S.R.; Marotzke, J.

    1999-02-01

    Some of the interactions and feedbacks between the atmosphere, thermohaline circulation, and sea ice are illustrated using a simple process model. A simplified version of the annual-mean coupled ocean-atmosphere box model of Nakamura, Stone, and Marotzke is modified to include a parameterization of sea ice. The model includes the thermodynamic effects of sea ice and allows for variable coverage. It is found that the addition of sea ice introduces feedbacks that have a destabilizing influence on the thermohaline circulation: Sea ice insulates the ocean from the atmosphere, creating colder air temperatures at high latitudes, which cause larger atmospheric eddy heat and moisture transports and weaker oceanic heat transports. These in turn lead to thicker ice coverage and hence establish a positive feedback. The results indicate that generally in colder climates, the presence of sea ice may lead to a significant destabilization of the thermohaline circulation. Brine rejection by sea ice plays no important role in this model`s dynamics. The net destabilizing effect of sea ice in this model is the result of two positive feedbacks and one negative feedback and is shown to be model dependent. To date, the destabilizing feedback between atmospheric and oceanic heat fluxes, mediated by sea ice, has largely been neglected in conceptual studies of thermohaline circulation stability, but it warrants further investigation in more realistic models.

  4. Summer Arctic Sea Ice Retreat: May - August 2013

    NASA Video Gallery

    The melting of sea ice in the Arctic is well on its way toward its annual "minimum," that time when the floating ice cap covers less of the Arctic Ocean than at any other period during the year. 20...

  5. Passive microwave in situ observations of winter Weddell Sea ice

    NASA Technical Reports Server (NTRS)

    Comiso, J. C.; Grenfell, T. C.; Bell, D. L.; Lange, M. A.; Ackley, S. F.

    1989-01-01

    Results are presented on the microwave radiative characteristics of Antarctic sea ice measured during the 1986 Winter Weddell Sea Project with a set of portable radiometers. Radiometer measurements at 6, 10, 18, 37, and 90 GHz in vertical and horizontal polarizations were supplemented by near-simultaneous measurements of the ice physical characteristics (including ice thickness, salinity, temperature, snow cover, and density) made during two cruises, lasting 3 months each. Measurements were obtained on various types of sea ice over a large portion of the Weddell-Sea ice cover, including four transects across the entire ice pack. Data analysis shows a large variability in the multispectral microwave emissivities of different ice types, especially at 90 GHz, demonstrating a strong potential of the use of the 90-GHz channel, in combination with lower-frequency channels, for detailed characterizations of the ice cover.

  6. The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss

    PubMed Central

    Notz, Dirk

    2009-01-01

    We discuss the existence of cryospheric “tipping points” in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea ice and the retreat of ice sheets: Once these ice masses have shrunk below an anticipated critical extent, the ice–albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea ice. Hence, in a cooler climate, sea ice could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea ice might largely be a consequence of a slow shift in ice-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-ice extent. This variability will render seasonal forecasts of the Arctic summer sea-ice extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea ice, a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet. PMID:19884496

  7. Contrasts in Arctic shelf sea-ice regimes and some implications: Beaufort Sea versus Laptev Sea

    USGS Publications Warehouse

    Reimnitz, E.; Dethleff, D.; Nurnberg, D.

    1994-01-01

    The winter ice-regime of the 500 km) from the mainland than in the Beaufort Sea. As a result, the annual freeze-up does not incorporate old, deep-draft ice, and with a lack of compression, such deep-draft ice is not generated in situ, as on the Beaufort Sea shelf. The Laptev Sea has as much as 1000 km of fetch at the end of summer, when freezing storms move in and large (6 m) waves can form. Also, for the first three winter months, the polynya lies inshore at a water depth of only 10 m. Turbulence and freezing are excellent conditions for sediment entrainment by frazil and anchor ice, when compared to conditions in the short-fetched Beaufort Sea. We expect entrainment to occur yearly. Different from the intensely ice-gouged Beaufort Sea shelf, hydraulic bedforms probably dominate in the Laptev Sea. Corresponding with the large volume of ice produced, more dense water is generated in the Laptev Sea, possibly accompanied by downslope sediment transport. Thermohaline convection at the midshelf polynya, together with the reduced rate of bottom disruption by ice keels, may enhance benthic productivity and permit establishment of open-shelf benthic communities which in the Beaufort Sea can thrive only in the protection of barrier islands. Indirect evidence for high benthic productivity is found in the presence of walrus, who also require year-round open water. By contrast, lack of a suitable environment restricts walrus from the Beaufort Sea, although over 700 km farther to the south. We could speculate on other consequences of the different ice regimes in the Beaufort and Laptev Seas, but these few examples serve to point out the dangers of exptrapolating from knowledge gained in the North American Arctic to other shallow Arctic shelf settings. ?? 1994.

  8. Global coupled sea ice-ocean state estimation

    NASA Astrophysics Data System (ADS)

    Fenty, Ian; Menemenlis, Dimitris; Zhang, Hong

    2015-09-01

    We study the impact of synthesizing ocean and sea ice concentration data with a global, eddying coupled sea ice-ocean configuration of the Massachusetts Institute of Technology general circulation model with the goal of reproducing the 2004 three-dimensional time-evolving ice-ocean state. This work builds on the state estimation framework developed in the Estimating the Circulation and Climate of the Ocean consortium by seeking a reconstruction of the global sea ice-ocean system that is simultaneously consistent with (1) a suite of in situ and remotely-sensed ocean and ice data and (2) the physics encoded in the numerical model. This dual consistency is successfully achieved here by adjusting only the model's initial hydrographic state and its atmospheric boundary conditions such that misfits between the model and data are minimized in a least-squares sense. We show that synthesizing both ocean and sea ice concentration data is required for the model to adequately reproduce the observed details of the sea ice annual cycle in both hemispheres. Surprisingly, only modest adjustments to our first-guess atmospheric state and ocean initial conditions are necessary to achieve model-data consistency, suggesting that atmospheric reanalysis products remain a leading source of errors for sea ice-ocean model hindcasts and reanalyses. The synthesis of sea ice data is found to ameliorate misfits in the high latitude ocean, especially with respect to upper ocean stratification, temperature, and salinity. Constraining the model to sea ice concentration modestly reduces ICESat-derived Arctic ice thickness errors by improving the temporal and spatial evolution of seasonal ice. Further increases in the accuracy of global sea ice thickness in the model likely require the direct synthesis of sea ice thickness data.

  9. Arctic and Antarctic Ice Pack Changes during the Past Decade from a High Resolution Global Coupled Sea Ice-Ocean Model

    NASA Astrophysics Data System (ADS)

    Ivanova, D. P.; McClean, J. L.; Thoppil, P.; Hunke, E.; Stark, D.; Maltrud, M. E.; Lipscomb, W.

    2004-12-01

    Changes over the past decade in the global ice pack are analyzed using a coupled ice-ocean model and observational data sets. The model consists of the latest versions of the Los Alamos Parallel Ocean Program (POP) and sea ice model (CICE) and is configured on a moderately high-resolution global grid (0.4° and 40 vertical levels). A model simulation forced with high frequency daily NCEP/NCAR atmospheric fields was integrated for 23 years (1979-2002). Following a decade-long ice spin-up, the model's ability to reproduce observed ice extent, ice thickness and ice drift distributions is evaluated by statistical comparisons using satellite, upward looking sonar and ice drift buoy data. In particular, the realism of the ice mean state and variability on time scales from daily to interannual are examined. To better understand ocean-ice interaction processes, coupled model results are compared to stand alone integrations of the ice and ocean models. Mean ice states are examined during the positive/negative phases of the North Atlantic Oscillation and Arctic Oscillation in the last decade of the coupled simulation. Particularly ice export from the Fram and Bering Straits during these phases will be considered.

  10. On the relationship of sea ice thickness and sea ice classes in Fram Strait and north of Svalbard

    NASA Astrophysics Data System (ADS)

    Renner, A.; Dumont, M.; Gerland, S.; Beckers, J.; Granskog, M.; Goodwin, H.; Haas, C.

    2011-12-01

    In this poster, we present results from sea ice thickness surveys conducted during several scientific cruises in 2010 and 2011 in the region north of Svalbard and along 79° N in Fram Strait using a helicopter-borne electromagnetic device (EM-bird) in combination with aerial photography. A camera was mounted in the helicopter looking downwards at the EM-bird and the sea ice underneath and photos were taken every five seconds. A method based on discriminant analysis was developed to retrieve the fractions of the different ice types from the aerial photos. These fractions of open water, ice, thin ice, melt ponds and submerged ice were then combined with the ice thickness simultaneously measured by the EM-bird. The combination of ice thickness and ice type information provides insight into the characteristics of the different ice regimes and changes within these regimes. For example in Fram Strait in late summer 2010, the modal ice thickness was 1.2 m with the exception of a flight over the fast ice off the east coast of Greenland. There, the modal thickness was 2.9 m for a wide section of heavily ridged ice in front of the smoother, 1 m thick, level fast ice. As usual for the season, the sea ice was largely covered by melt ponds. However, the photo analyses show no significant difference between the fraction of melt ponds over ridged and level fast ice for this summer. The ice was thinner than expected, indicating the export of younger ice from the inner Arctic Ocean than in previous years. While the sea ice in Fram Strait is dominated by ice exported from the north, the ice cover north of Svalbard consists mostly of first-year ice. In summer 2010, this was visible in a narrower thickness distribution than in Fram Strait and a different distribution of the ice class fractions from the photographs.

  11. Active laser system for sea ice control

    NASA Astrophysics Data System (ADS)

    Evtikhiev, Nickolay N.; Gaponov, Alexandr E.; Kuluba, Yury N.; Matous, Vladislav I.; Radominov, Oleg E.; Tuzikov, Vladimir Z.; Vargaftic, Vasiliy N.

    1997-01-01

    The airborne systems are used for complex investigations of coastline very successfully, for example it can be used to measure the depth of the sea, to discover the reefs and so on. Such information may be used in navigation too. The specific conditions of navigation in the North and Pole seas defines the necessity of exact knowledge about the ice cracks in order to find the possible direction of the ship movement. The active optical system, working in the near IR region, has many advantages before the passive one, especially if it is necessary to work during the polar night and at bad weather conditions. In this article we discuss the demands to the laser active airborne systems, that given the accurate picture of the ice with high resolution in the daytime and nighttime conditions. Such system based on the laser, mechanical scanner and avalanche photodiode is very compact, reliable and informative. The picture of the ice surface can be shown on the TV monitor, can be written to the memory and can be delivered to the processing center by the radiochannel. The experimental results are shown together with results of this system probing in the conditions of the North Pole Ocean.

  12. Interferometric System for Measuring Thickness of Sea Ice

    NASA Technical Reports Server (NTRS)

    Hussein, Ziad; Jordan, Rolando; McDonald, Kyle; Holt, Benjamin; Huang, John; Kugo, Yasuo; Ishimaru, Akira; Jaruwatanadilok, Semsak; Akins, Torry; Gogineni, Prasad

    2006-01-01

    The cryospheric advanced sensor (CAS) is a developmental airborne (and, potentially, spaceborne) radar-based instrumentation system for measuring and mapping the thickness of sea ice. A planned future version of the system would also provide data on the thickness of snow covering sea ice. Frequent measurements of the thickness of polar ocean sea ice and its snow cover on a synoptic scale are critical to understanding global climate change and ocean circulation.

  13. Modeling ocean wave propagation under sea ice covers

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  14. North Pacific climate variability and Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Linkin, Megan E.

    Boreal winter North Pacific climate variability strongly influences North American hydroclimate and Arctic sea ice distribution in the marginal Arctic seas. Two modes of atmospheric variability explaining 53% of the variance in the Pacific Ocean sea level pressure (SLP) field are extracted and identified: the Pacific-North American (PNA) teleconnection and the North Pacific Oscillation/West Pacific (NPO/WP) teleconnection. The NPO/WP, a dipole in North Pacific SLP and geopotential heights, is affiliated with latitudinal displacements of the Asian Pacific jet and an intensification of the Pacific stormtrack. The North American hydroclimate impacts of the NPO/WP are substantial; its impact on Alaska, Pacific Northwest and Great Plains precipitation is more influential than both the PNA and the El Nino-Southern Oscillation (ENSO). The NPO/WP is also strongly associated with a contemporaneous extension of the marginal ice zone (MIZ) in the western Bering Sea and Sea of Okhotsk and MIZ retreat in the eastern Bering Sea. Wintertime climate variability also significantly impacts the distribution of Arctic sea ice during the subsequent summer months, due to the hysteretic nature of the ice cap. The North Atlantic Oscillation (NAO) is known for its effects on summer sea ice distribution; this study extends into the Pacific and finds that circulation anomalies related to Pacific sea surface temperature (SST) variability also strongly impact summer Arctic sea ice. The NAO and ENSO are related to sea ice decline in the Eastern Siberian Sea, where the linear trend since 1979 is 25% per decade. PDV affects sea ice in the eastern Arctic, a region which displays no linear trend since 1979. The low frequency of PDV variability and the persistent positive NAO during the 1980s and 1990s results in natural variability being aliased into the total linear trend in summer sea ice calculated from satellite-based sea ice concentration. Since 1979, natural variability accounts for 30% of

  15. Arctic and Antarctic Sea Ice Changes and Impacts (Invited)

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.

    2013-12-01

    The extent of springtime Arctic perennial sea ice, important to preconditioning summer melt and to polar sunrise photochemistry, continues its precipitous reduction in the last decade marked by a record low in 2012, as the Bromine, Ozone, and Mercury Experiment (BROMEX) was conducted around Barrow, Alaska, to investigate impacts of sea ice reduction on photochemical processes, transport, and distribution in the polar environment. In spring 2013, there was further loss of perennial sea ice, as it was not observed in the ocean region adjacent to the Alaskan north coast, where there was a stretch of perennial sea ice in 2012 in the Beaufort Sea and Chukchi Sea. In contrast to the rapid and extensive loss of sea ice in the Arctic, Antarctic sea ice has a trend of a slight increase in the past three decades. Given the significant variability in time and in space together with uncertainties in satellite observations, the increasing trend of Antarctic sea ice may arguably be considered as having a low confidence level; however, there was no overall reduction of Antarctic sea ice extent anywhere close to the decreasing rate of Arctic sea ice. There exist publications presenting various factors driving changes in Arctic and Antarctic sea ice. After a short review of these published factors, new observations and atmospheric, oceanic, hydrological, and geological mechanisms contributed to different behaviors of sea ice changes in the Arctic and Antarctic are presented. The contribution from of hydrologic factors may provide a linkage to and enhance thermal impacts from lower latitudes. While geological factors may affect the sensitivity of sea ice response to climate change, these factors can serve as the long-term memory in the system that should be exploited to improve future projections or predictions of sea ice changes. Furthermore, similarities and differences in chemical impacts of Arctic and Antarctic sea ice changes are discussed. Understanding sea ice changes and

  16. Arctic sea ice freeboard heights from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Renganathan, Vidyavathy

    The Arctic sea ice cover is most sensitive to climate change and variability, mainly due to the ice-albedo feedback effect. With an increase in the average temperature across the Arctic during the past few decades, sea ice has been melting rapidly. The decline in the sea ice extent was estimated as 10% per decade since satellite observations began in 1979. Sea ice thickness is an important parameter that moderates the heat exchange between the ocean and the atmosphere, extent of sea ice deformation and sea ice circulation in the Arctic Ocean. In addition, sea ice thermodynamics and dynamics depend on the thickness of the sea ice cover. In order to estimate the trend in the sea ice volume, both the extent and thickness must be known. Hence, it is important to measure the sea ice freeboard (a representative fraction of the thickness) distribution in the Arctic Ocean. In this thesis, the total ice freeboards (height of the snow/ice surface above the sea level) were derived from satellite laser altimetry. NASA's Ice Cloud and Land Elevation Satellite (ICESat) carries a Geoscience Laser Altimetry System (GLAS) onboard, and provides dense coverage of snow (or sea ice) surface heights in the Arctic Ocean up to 86° N. The total freeboard height at each ICESat footprint location was computed by removing the instantaneous sea surface height from the ice/snow surface height. In this study, the instantaneous sea surface heights were modeled using a combination of geodetic and oceanographic models. In order to improve the accuracy of the freeboard estimation, an accuracy assessment of the ocean tide models (one of the component models in the sea surface height estimation) in the Arctic Ocean was performed. The Arctic Ocean Tide Inverse Model (AOTIM-5) was found to have the best accuracy in the Arctic Ocean and was, therefore, used in the sea ice freeboard estimation. It was also shown that the present generation of ocean tide models have ignored the ice-tide interaction

  17. Seasonal Evolution of Snow Cover on Antarctic Sea Ice

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  18. neXtSIM: a new Lagrangian sea ice model

    NASA Astrophysics Data System (ADS)

    Rampal, P.; Bouillon, S.; Ólason, E.; Morlighem, M.

    2015-10-01

    The Arctic sea ice cover has changed drastically over the last decades. Associated with these changes is a shift in dynamical regime seen by an increase of extreme fracturing events and an acceleration of sea ice drift. The highly non-linear dynamical response of sea ice to external forcing makes modelling these changes, and the future evolution of Arctic sea ice a challenge for current models. It is, however, increasingly important that this challenge be better met, both because of the important role of sea ice in the climate system and because of the steady increase of industrial operations in the Arctic. In this paper we present a new dynamical/thermodynamical sea ice model, called neXtSIM in order to address this. neXtSIM is a continuous and fully Lagrangian model, and the equations are discretised with the finite-element method. In this model, sea ice physics are driven by a synergic combination of two core components: a model for sea ice dynamics built on a new mechanical framework using an elasto-brittle rheology, and a model for sea ice thermodynamics providing damage healing for the mechanical framework. The results of a thorough evaluation of the model performance for the Arctic are presented for the period September 2007 to October 2008. They show that observed multi-scale statistical properties of sea ice drift and deformation are well captured as well as the seasonal cycles of ice volume, area, and extent. These results show that neXtSIM is a very promising tool for simulating the sea ice over a wide range of spatial and temporal scales.

  19. neXtSIM: a new Lagrangian sea ice model

    NASA Astrophysics Data System (ADS)

    Rampal, Pierre; Bouillon, Sylvain; Ólason, Einar; Morlighem, Mathieu

    2016-05-01

    The Arctic sea ice cover has changed drastically over the last decades. Associated with these changes is a shift in dynamical regime seen by an increase of extreme fracturing events and an acceleration of sea ice drift. The highly non-linear dynamical response of sea ice to external forcing makes modelling these changes and the future evolution of Arctic sea ice a challenge for current models. It is, however, increasingly important that this challenge be better met, both because of the important role of sea ice in the climate system and because of the steady increase of industrial operations in the Arctic. In this paper we present a new dynamical/thermodynamical sea ice model called neXtSIM that is designed to address this challenge. neXtSIM is a continuous and fully Lagrangian model, whose momentum equation is discretised with the finite-element method. In this model, sea ice physics are driven by the combination of two core components: a model for sea ice dynamics built on a mechanical framework using an elasto-brittle rheology, and a model for sea ice thermodynamics providing damage healing for the mechanical framework. The evaluation of the model performance for the Arctic is presented for the period September 2007 to October 2008 and shows that observed multi-scale statistical properties of sea ice drift and deformation are well captured as well as the seasonal cycles of ice volume, area, and extent. These results show that neXtSIM is an appropriate tool for simulating sea ice over a wide range of spatial and temporal scales.

  20. Influence of ice thickness and surface properties on light transmission through Arctic sea ice.

    NASA Astrophysics Data System (ADS)

    Katlein, Christian; Arndt, Stefanie; Nicolaus, Marcel; Jakuba, Michael V.; Laney, Samuel; Elliott, Stephen; Whitcomb, Louis L.; McFarland, Christopher J.; Suman, Stefano; Gerdes, Rüdiger; Boetius, Antje; German, Christopher R.

    2015-04-01

    The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy balance of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy and thus plays a crucial role for sea-ice-melt as well as for the amount and timing of under-ice primary production. Recent developments in underwater technology provide new opportunities to undertake challenging research at the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance onboard the new Nereid Under-Ice (Nereid-UI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. Nereid-UI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely-piloted and autonomous surveys underneath fixed and moving sea ice. Here we present results from the first comprehensive scientific dive of Nereid-UI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance on floe scale. Our results indicate that surface properties dominate the spatial distribution of the under-ice light field, while sea ice-thickness and snow-depth are most important for mean light levels.

  1. Modelling Sea Ice and Surface Wave Interactions in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, L.; Aksenov, Y.; Coward, A.; Williams, T.; Bertino, L.; Nurser, A. J. G.

    2015-12-01

    In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with a widening of up to 39% in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model (OGCM) NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to scattering and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to flexural stresses. This fragmentation modifies the floe size distribution and impacts the sea ice thermodynamics by increasing lateral melting and thus affecting momentum and heat transfer between sea ice and the upper ocean. In addition, the dynamics of the sea ice is modified by a combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 and 0.25 degree resolution with a wave-ice interaction module. The module introduces two new diagnostics previously unavailable in OGCM's: surface wave spectra in sea ice covered areas, and floe size distribution (FSD) due to wave-induced fragmentation. We evaluate the sea ice and wave simulations with available observational estimates, and analyze the impact of these MIZ processes on the ocean and sea ice state. We focus on ocean mixing, stratification, circulation and the role of the MIZ in ocean

  2. Comparison of automatic segmentation of full polarimetric SAR sea ice images with manually drawn ice charts

    NASA Astrophysics Data System (ADS)

    Moen, M.-A. N.; Doulgeris, A. P.; Anfinsen, S. N.; Renner, A. H. H.; Hughes, N.; Gerland, S.; Eltoft, T.

    2013-06-01

    In this paper we investigate the performance of an algorithm for automatic segmentation of full polarimetric, synthetic aperture radar (SAR) sea ice scenes. The algorithm uses statistical and polarimetric properties of the backscattered radar signals to segment the SAR image into a specified number of classes. This number was determined in advance from visual inspection of the SAR image and by available in-situ measurements. The segmentation result was then compared to ice charts drawn by ice service analysts. The comparison revealed big discrepancies between the charts of the analysts, and between the manual and the automatic segmentations. In the succeeding analysis, the automatic segmentation chart was labeled into ice types by sea ice experts, and the SAR features used in the segmentation were interpreted in terms of physical sea ice properties. Studies of automatic and robust estimation of the number of ice classes in SAR sea ice scenes will be highly relevant for future work.

  3. Polar sea ice observations by means of microwave radiometry

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Chang, T. C.; Wilheit, T. T.; Campbell, W. J.

    1973-01-01

    Principles pertinent to the utilization of 1.55 cm wavelength radiation emanating from the surface of the earth for studying the changing characteristics of polar sea ice are briefly reviewed. Recent data obtained at that wavelength with an imaging radiometer on-board the Nimbus 5 satellite are used to illustrate how the seasonal changes in extent of sea ice in both polar regions may be monitored free of atmospheric interference. Within a season, changes in the compactness of the sea ice are also observed from the satellite. Some substantial areas of the Arctic sea ice canopy identified as first-year ice in the past winter were observed not to melt this summer, a graphic illustration of the eventual formation of multiyear ice in the Arctic. Finally, the microwave emissivity of some of the multiyear ice areas near the North Pole was found to increase significantly in the summer, probably due to liquid water content in the firm layer.

  4. Biological Response to Recent Pacific Arctic Sea Ice Retreats

    NASA Astrophysics Data System (ADS)

    Grebmeier, Jacqueline M.; Moore, Sue E.; Overland, James E.; Frey, Karen E.; Gradinger, Rolf

    2010-05-01

    Although recent major changes in the physical domain of the Arctic region, such as extreme retreats of summer sea ice since 2007, are well documented, large uncertainties remain regarding responses in the biological domain. In the Pacific Arctic north of Bering Strait, reduction in sea ice extent has been seasonally asymmetric, with minimal changes until the end of June and delayed sea ice formation in late autumn. The effect of extreme ice retreats and seasonal asymmetry in sea ice loss on primary production is uncertain, with no clear shift over time (2003-2008) in satellite-derived chlorophyll concentrations. However, clear changes have occurred during summer in species ranges for zooplankton, bottom-dwelling organisms (benthos), and fish, as well as through the loss of sea ice as habitat and platform for marine mammals.

  5. Iodocarbons and Bromocarbons Associated with Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Roscoe, H. K.; Obbard, R. W.; Atkinson, H. M.; Hughes, C.; Liss, P. S.

    2015-12-01

    Short-lived halocarbons were measured in Arctic sea-ice brine, seawater and air above the Greenland and Norwegian seas at about 81°N in mid-summer, from a melting ice floe at the edge of the ice pack. In the ice floe, concentrations of C2H5I, 2-C3H7I and CH2Br2 showed significant enhancement in the sea ice brine, of average factors of 1.7, 1.4 and 2.5 times respectively, compared to the water underneath and after normalising to brine volume. Concentrations of mono-iodocarbons in air are the highest ever reported, and our calculations suggest increased fluxes of halocarbons to the atmosphere may result from their sea-ice enhancement. Laboratory measurements suggest that sea-ice diatoms produce iodocarbons in response to salinity stress. Concentrations of halocarbons in the Arctic ice were similar to those in earlier work in Antarctic sea ice that was similarly warm and porous. As climate warms and Arctic sea ice becomes more like that of the Antarctic, our results lead us to expect the production of iodocarbons and so of reactive iodine gases to increase.

  6. Coincident multiscale estimates of Arctic sea ice thickness

    NASA Astrophysics Data System (ADS)

    Gardner, Joan; Richter-Menge, Jackie; Farrell, Sinead; Brozena, John

    2012-02-01

    Recent dramatic changes in the characteristics of the Arctic sea ice cover have sparked interest and concern from a wide range of disciplines including socioeconomics, maritime safety and security, and resource management, as well as basic research science. Though driven by different priorities, common to all is the demand for an improved ability to monitor and forecast changes in the sea ice cover. Key to meeting this demand is further improvement in the quality of observations collected from remote platforms. Satellites provide an important platform for instruments designed to monitor basin-wide changes in the volume of the ice cover, a function of ice extent and thickness. Remote techniques to monitor sea ice extent in all seasons are well developed—these observations reveal a dramatic decline in summer sea ice extent since 1979, when satellite records became available. Further, they indicate that the decline has been facilitated by a dramatic decrease in the extent of perennial (i.e., multiyear) ice. Combined estimates of ice thickness derived from submarine records between 1958 and 2000, and Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry from 2003 to 2008, provide the longest-term record of sea ice thickness observations. These data suggest a decrease in the mean overall thickness of the sea ice over a region covering about 38% of the Arctic Ocean.

  7. Controls on Arctic sea ice from first-year and multi-year ice survival rates

    NASA Astrophysics Data System (ADS)

    Armour, K.; Bitz, C. M.; Hunke, E. C.; Thompson, L.

    2009-12-01

    The recent decrease in Arctic sea ice cover has transpired with a significant loss of multi-year (MY) ice. The transition to an Arctic that is populated by thinner first-year (FY) sea ice has important implications for future trends in area and volume. We develop a reduced model for Arctic sea ice with which we investigate how the survivability of FY and MY ice control various aspects of the sea-ice system. We demonstrate that Arctic sea-ice area and volume behave approximately as first-order autoregressive processes, which allows for a simple interpretation of September sea-ice in which its mean state, variability, and sensitivity to climate forcing can be described naturally in terms of the average survival rates of FY and MY ice. This model, used in concert with a sea-ice simulation that traces FY and MY ice areas to estimate the survival rates, reveals that small trends in the ice survival rates explain the decline in total Arctic ice area, and the relatively larger loss of MY ice area, over the period 1979-2006. Additionally, our model allows for a calculation of the persistence time scales of September area and volume anomalies. A relatively short memory time scale for ice area (~ 1 year) implies that Arctic ice area is nearly in equilibrium with long-term climate forcing at all times, and therefore observed trends in area are a clear indication of a changing climate. A longer memory time scale for ice volume (~ 5 years) suggests that volume can be out of equilibrium with climate forcing for long periods of time, and therefore trends in ice volume are difficult to distinguish from its natural variability. With our reduced model, we demonstrate the connection between memory time scale and sensitivity to climate forcing, and discuss the implications that a changing memory time scale has on the trajectory of ice area and volume in a warming climate. Our findings indicate that it is unlikely that a “tipping point” in September ice area and volume will be

  8. Arctic Summer Sea-Ice Extent: How Free is Free?

    NASA Astrophysics Data System (ADS)

    Tremblay, B.; Cullather, R. I.; DeRepentigny, P.; Pfirman, S. L.; Newton, R.

    2015-12-01

    As Northern Hemisphere perennial sea ice cover continues a long-term downward trend, attention has begun to focus on the implications of the changing conditions. A summertime ice-free Arctic Ocean is frequently indicated as a signature milestone for these changes, however "ice-free" has a substantially different meaning among scientists and interested stakeholders. To climate scientists it may mean when there is so little sea ice that it plays a minimal role in the climate system. To those interested in development, it may mean a threshold where icebreaker support is not required. To coastal communities it may mean so little ice that hunting is not possible. To species dependent on sea ice, it may mean the point where they cannot find sufficient habitat to survive from spring until fall. In this contribution we document the projected seasonality of the sea ice retreat and address the following questions. For how long will the Arctic Ocean be ice free on average each year? What is the impact of such changes in the seasonality of the sea ice cover on species that are dependent on sea ice? To this end, we analyze the seasonal cycle in the sea-ice extent simulated by the Community Earth System Model 1 - Large Ensemble (CESM1-LE) output for the 21st century. CESM1-LE simulates a realistic late 20th, early 21st century Arctic climate with a seasonal cycle in sea ice extent and rate of decline in good agreement with observations. Results from this model show that even by the end of the 21st century, the length of the ice-free season is relatively short, with ice-free conditions mainly present for 2-3 months between August and October. The result is a much larger amplitude seasonal cycle when compared with the late 20th century climate.

  9. Revisiting Observations of Arctic Sea-ice Motion and Deformation To Investigate Bounds of Sea-ice Variability.

    NASA Astrophysics Data System (ADS)

    Heil, P.

    The Arctic sea ice is an important part of the northern polar climate system. Individual records of sea-ice drift in the Arctic were obtained through the last century. Observa- tions with high spatial or temporal coverage start in the 1970's when remote observa- tions of sea-ice motion are available from satellite-based instruments and in situ from drifting buoys. In the climatology of Arctic sea-ice drift the clockwise Beaufort Gyre, a northward motion off the Siberian Coast, and a south-eastward drift from the North Pole towards Fram Strait, have been identified. During recent decades this picture of Arctic ice motion has shifted away from the baseline state in response to changed at- mospheric conditions. Here we investigate high-resolution time-series of ice motion derived from IABP drifting buoys to identify further patterns of preferred ice motion in the Arctic. These can be associated with atmospheric regimes by correlating the two- dimensional variance of the buoy-derived ice velocities with the horizontal gradient of the mean sea-level pressure. Changes in the spatial pattern of regional meander coeffi- cients for the sea-ice motion provide further evidence for repeated transitions between patterns of ice motion in dependence to the atmospheric forcing. This is supported by dynamic frequency spectra of sea-ice divergence, which suggest damping of subdaily deformation cycles during low AO years. For regions with persistent buoy coverage (e.g., the western Arctic) time-series of sea-ice motion and deformation characteris- tics have been constructed. The identification of a dominant spatial pattern of sea-ice motion and deformation in response to changing atmospheric forcing is then used to explain the variability seen in Arctic ice extent and volume.

  10. Interdecadal changes in snow depth on Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Webster, Melinda A.; Rigor, Ignatius G.; Nghiem, Son V.; Kurtz, Nathan T.; Farrell, Sinead L.; Perovich, Donald K.; Sturm, Matthew

    2014-08-01

    Snow plays a key role in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from cold air temperatures, slowing sea ice growth. From spring to summer, the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean, impacting ice melt processes. Knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume, and for understanding and modeling sea ice thermodynamics in the changing Arctic. This study assesses spring snow depth distribution on Arctic sea ice using airborne radar observations from Operation IceBridge for 2009-2013. Data were validated using coordinated in situ measurements taken in March 2012 during the Bromine, Ozone, and Mercury Experiment (BROMEX) field campaign. We find a correlation of 0.59 and root-mean-square error of 5.8 cm between the airborne and in situ data. Using this relationship and IceBridge snow thickness products, we compared the recent results with data from the 1937, 1954-1991 Soviet drifting ice stations. The comparison shows thinning of the snowpack, from 35.1 ± 9.4 to 22.2 ± 1.9 cm in the western Arctic, and from 32.8 ± 9.4 to 14.5 ± 1.9 cm in the Beaufort and Chukchi seas. These changes suggest a snow depth decline of 37 ± 29% in the western Arctic and 56 ± 33% in the Beaufort and Chukchi seas. Thinning is negatively correlated with the delayed onset of sea ice freezeup during autumn.

  11. Evolution of a Coupled Marine Ice Sheet - Sea Level Model

    NASA Astrophysics Data System (ADS)

    Gomez, N.; Pollard, D.; Mitrovica, J. X.; Huybers, P.; Clark, P. U.

    2011-12-01

    An instability mechanism is widely predicted for marine ice sheets resting upon reversed bed slopes. In this case, ice-sheet thinning or rising sea level is thought to lead to irreversible retreat of the grounding line. Previous analyses of marine ice-sheet stability have considered the influence of a sea-level perturbation on ice-sheet stability by assuming a geographically uniform, or eustatic, change in sea level. However, gravitational and deformational effects associated with changes in the volume of grounded ice lead to markedly non-uniform spatial patterns of sea-level change. In particular, a gravitationally self-consistent sea-level theory predicts a near-field sea-level change of opposite sign, and an order of magnitude greater amplitude, than would be predicted assuming eustasy. In recent work (Gomez et. al., Nature Geoscience, 2010), we highlighted the potential importance of this stabilizing sea-level mechanism by incorporating gravitationally self-consistent sea-level changes into a steady state ice sheet model. We extend this earlier analysis to investigate the influence of this stabilization mechanism on the timescale of ice-sheet retreat by coupling a sea-level model valid for a self-gravitating, viscoelastically deforming Earth to a 1D, dynamic marine ice sheet-shelf model. The evolution of the coupled model is explored for a suite of simulations in which we vary the bed slope and the forcing that initiates retreat. We find that the sea-level fall at the grounding line associated with a retreating ice sheet acts to slow the retreat; in simulations with shallow reversed bed slopes and/or small initial forcing, the drop in sea level can be sufficient to halt the retreat. The rate of sea-level change at the grounding line has an elastic component due to ongoing changes in ice-sheet geometry, and a viscous component due to past ice and ocean load changes. When the ice-sheet model is forced from steady state, on short timescales (< ~500 years), viscous

  12. A microwave radiometer weather-correcting sea ice algorithm

    NASA Technical Reports Server (NTRS)

    Walters, J. M.; Ruf, C.; Swift, C. T.

    1987-01-01

    A new algorithm for estimating the proportions of the multiyear and first-year sea ice types under variable atmospheric and sea surface conditions is presented, which uses all six channels of the SMMR. The algorithm is specifically tuned to derive sea ice parameters while accepting error in the auxiliary parameters of surface temperature, ocean surface wind speed, atmospheric water vapor, and cloud liquid water content. Not only does the algorithm naturally correct for changes in these weather conditions, but it retrieves sea ice parameters to the extent that gross errors in atmospheric conditions propagate only small errors into the sea ice retrievals. A preliminary evaluation indicates that the weather-correcting algorithm provides a better data product than the 'UMass-AES' algorithm, whose quality has been cross checked with independent surface observations. The algorithm performs best when the sea ice concentration is less than 20 percent.

  13. Arctic Sea Ice Deformation in Satellite Remote Sensing Data and in a Coupled Sea Ice-Ocean Model

    NASA Astrophysics Data System (ADS)

    Spreen, G.; Kwok, R.; Menemenlis, D.; Nguyen, A. T.

    2010-12-01

    Sea ice movement is driven by surface wind and ocean currents. The spatial inhomogeneity of these forces causes internal sea ice stress gradients, which eventually cause ice to ridge or break up. This sea ice deformation is an important process for (1) the sea ice mass balance, (2) brine rejection into the ocean, (3) regulation of ocean-to-air heat and gas fluxes, and (4) altering the air and water drag coefficients and transfer of momentum at the ice ocean interface.. Sea ice deformation occurs across a broad range of spatial scales. Most noticeable are linear kinematic features (LKFs) that have lengths of hundreds to thousands of kilometers and a typical lifetime of days to weeks. In addition, as inferred from data, sea ice deformation a) has a spatial distribution with higher deformation rates in the seasonal ice zone than for perennial sea ice, and b) does not scale linearly with the length scale over which it is integrated but follows a power law. Consecutive observations provided by RADARSAT Synthetic Aperture Radar (SAR) are used to derive sea ice velocity fields by a maximum-cross-correlation method. From these velocity fields the fields of divergence, shear and vorticity are obtained. These datasets are products of the RADARSAT Geophysical Processor System (RGPS). These RGPS sea ice deformation fields are compared to solutions of a coupled sea ice-ocean model. Arctic sea ice-ocean simulations from the MIT general circulation model (MITgcm) with 4.5, 9, and 18 km horizontal grid spacing were carried. The model setup uses a viscous-plastic sea ice rheology with an elliptical yield curve. Such models can reproduce some aspects of sea ice drift but it remains unclear whether the model physics are suitable to reproduce the observed sea ice deformation features. First comparisons with satellite remote sensing data reveal big differences in the shape, frequency of occurrence, and spatial distribution of LKFs. In this study three main questions are addressed: (1

  14. NWS Alaska Sea Ice Program: Operations and Decision Support Services

    NASA Astrophysics Data System (ADS)

    Schreck, M. B.; Nelson, J. A., Jr.; Heim, R.

    2015-12-01

    The National Weather Service's Alaska Sea Ice Program is designed to service customers and partners operating and planning operations within Alaska waters. The Alaska Sea Ice Program offers daily sea ice and sea surface temperature analysis products. The program also delivers a five day sea ice forecast 3 times each week, provides a 3 month sea ice outlook at the end of each month, and has staff available to respond to sea ice related information inquiries. These analysis and forecast products are utilized by many entities around the state of Alaska and nationally for safety of navigation and community strategic planning. The list of current customers stem from academia and research institutions, to local state and federal agencies, to resupply barges, to coastal subsistence hunters, to gold dredgers, to fisheries, to the general public. Due to a longer sea ice free season over recent years, activity in the waters around Alaska has increased. This has led to a rise in decision support services from the Alaska Sea Ice Program. The ASIP is in constant contact with the National Ice Center as well as the United States Coast Guard (USCG) for safety of navigation. In the past, the ASIP provided briefings to the USCG when in support of search and rescue efforts. Currently, not only does that support remain, but our team is also briefing on sea ice outlooks into the next few months. As traffic in the Arctic increases, the ASIP will be called upon to provide more and more services on varying time scales to meet customer needs. This talk will address the many facets of the current Alaska Sea Ice Program as well as delve into what we see as the future of the ASIP.

  15. First Results from the ASIBIA (Arctic Sea-Ice, snow, Biogeochemistry and Impacts on the Atmosphere) Sea-Ice Chamber

    NASA Astrophysics Data System (ADS)

    Frey, M. M.; France, J.; von Glasow, R.; Thomas, M.

    2015-12-01

    The ocean-ice-atmosphere system is very complex, and there are numerous challenges with conducting fieldwork on sea-ice including costs, safety, experimental controls and access. By creating a new coupled Ocean-Sea-Ice-(Snow)-Atmosphere facility at the University of East Anglia, UK, we are able to perform controlled investigations in areas such as sea-ice physics, physicochemical and biogeochemical processes in sea-ice, and to quantify the bi-directional flux of gases in established, freezing and melting sea-ice. The environmental chamber is capable of controlled programmable temperatures from -55°C to +30°C, allowing a full range of first year sea-ice growing conditions in both the Arctic and Antarctic to be simulated. The sea-ice tank within the chamber measures 2.4 m x 1.4 m x 1 m water depth, with an identically sized Teflon film atmosphere on top of the tank. The tank and atmosphere forms a coupled, isolated mesocosm. Above the atmosphere is a light bank with dimmable solar simulation LEDs, and UVA and UVB broadband fluorescent battens, providing light for a range of experiments such as under ice biogeochemistry and photochemistry. Ice growth in the tank will be ideally suited for studying first-year sea-ice physical properties, with in-situ ice-profile measurements of temperature, salinity, conductivity, pressure and spectral light transmission. Under water and above ice cameras are installed to observe the physical development of the sea-ice. The ASIBIA facility is also well equipped for gas exchange and diffusion studies through sea-ice with a suite of climate relevant gas measuring instruments (CH4, CO2, O3, NOx, NOy permanently installed, further instruments available) able to measure either directly in the atmospheric component, or via a membrane for water side dissolved gases. Here, we present the first results from the ASIBIA sea-ice chamber, focussing on the physical development of first-year sea-ice and show the future plans for the facility over

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

    NASA Astrophysics Data System (ADS)

    Gerland, S.; Spreen, G.; Granskog, M. A.; Divine, D.; Ehn, J. K.; Eltoft, T.; Gallet, J. C.; Haapala, J. J.; Hudson, S. R.; Hughes, N. E.; Itkin, P.; King, J.; Krumpen, T.; Kustov, V. Y.; Liston, G. E.; Mundy, C. J.; Nicolaus, M.; Pavlov, A.; Polashenski, C.; Provost, C.; Richter-Menge, J.; Rösel, A.; Sennechael, N.; Shestov, A.; Taskjelle, T.; Wilkinson, J.; Steen, H.

    2015-12-01

    Arctic sea ice is changing, and for improving the understanding of the cryosphere, data is needed to describe the status and processes controlling current seasonal sea ice growth, change and decay. We present preliminary results from in-situ observations on sea ice in the Arctic Basin north of Svalbard from January to June 2015. Over that time, the Norwegian research vessel «Lance» was moored to in total four ice floes, drifting with the sea ice and allowing an international group of scientists to conduct detailed research. Each drift lasted until the ship reached the marginal ice zone and ice started to break up, before moving further north and starting the next drift. The ship stayed within the area approximately 80°-83° N and 5°-25° E. While the expedition covered measurements in the atmosphere, the snow and sea ice system, and in the ocean, as well as biological studies, in this presentation we focus on physics of snow and sea ice. Different ice types could be investigated: young ice in refrozen leads, first year ice, and old ice. Snow surveys included regular snow pits with standardized measurements of physical properties and sampling. Snow and ice thickness were measured at stake fields, along transects with electromagnetics, and in drillholes. For quantifying ice physical properties and texture, ice cores were obtained regularly and analyzed. Optical properties of snow and ice were measured both with fixed installed radiometers, and from mobile systems, a sledge and an ROV. For six weeks, the surface topography was scanned with a ground LIDAR system. Spatial scales of surveys ranged from spot measurements to regional surveys from helicopter (ice thickness, photography) during two months of the expedition, and by means of an array of autonomous buoys in the region. Other regional information was obtained from SAR satellite imagery and from satellite based radar altimetry. The analysis of the data collected has started, and first results will be

  17. The discrimination of sea ice types using SAR backscatter statistics

    NASA Technical Reports Server (NTRS)

    Shuchman, Robert A.; Wackerman, Christopher C.; Maffett, Andrew L.; Onstott, Robert G.; Sutherland, Laura L.

    1989-01-01

    X-band (HH) synthetic aperture radar (SAR) data of sea ice collected during the Marginal Ice Zone Experiment in March and April of 1987 was statistically analyzed with respect to discriminating open water, first-year ice, multiyear ice, and Odden. Odden are large expanses of nilas ice that rapidly form in the Greenland Sea and transform into pancake ice. A first-order statistical analysis indicated that mean versus variance can segment out open water and first-year ice, and skewness versus modified skewness can segment the Odden and multilayer categories. In additions to first-order statistics, a model has been generated for the distribution function of the SAR ice data. Segmentation of ice types was also attempted using textural measurements. In this case, the general co-occurency matrix was evaluated. The textural method did not generate better results than the first-order statistical approach.

  18. Uncertainty Quantification and Sensitivity Analysis in the CICE v5.1 Sea Ice Model

    NASA Astrophysics Data System (ADS)

    Urrego-Blanco, J. R.; Urban, N. M.

    2015-12-01

    Changes in the high latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with mid latitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. In this work we characterize parametric uncertainty in Los Alamos Sea Ice model (CICE) and quantify the sensitivity of sea ice area, extent and volume with respect to uncertainty in about 40 individual model parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one-at-a-time, this study uses a global variance-based approach in which Sobol sequences are used to efficiently sample the full 40-dimensional parameter space. This approach requires a very large number of model evaluations, which are expensive to run. A more computationally efficient approach is implemented by training and cross-validating a surrogate (emulator) of the sea ice model with model output from 400 model runs. The emulator is used to make predictions of sea ice extent, area, and volume at several model configurations, which are then used to compute the Sobol sensitivity indices of the 40 parameters. A ranking based on the sensitivity indices indicates that model output is most sensitive to snow parameters such as conductivity and grain size, and the drainage of melt ponds. The main effects and interactions among the most influential parameters are also estimated by a non-parametric regression technique based on generalized additive models. It is recommended research to be prioritized towards more accurately determining these most influential parameters values by observational studies or by improving existing parameterizations in the sea ice model.

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

    NASA Astrophysics Data System (ADS)

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

    1989-08-01

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

  20. Observed platelet ice distributions in Antarctic sea ice: An index for ocean-ice shelf heat flux

    NASA Astrophysics Data System (ADS)

    Langhorne, P. J.; Hughes, K. G.; Gough, A. J.; Smith, I. J.; Williams, M. J. M.; Robinson, N. J.; Stevens, C. L.; Rack, W.; Price, D.; Leonard, G. H.; Mahoney, A. R.; Haas, C.; Haskell, T. G.

    2015-07-01

    Antarctic sea ice that has been affected by supercooled Ice Shelf Water (ISW) has a unique crystallographic structure and is called platelet ice. In this paper we synthesize platelet ice observations to construct a continent-wide map of the winter presence of ISW at the ocean surface. The observations demonstrate that, in some regions of coastal Antarctica, supercooled ISW drives a negative oceanic heat flux of -30 Wm-2 that persists for several months during winter, significantly affecting sea ice thickness. In other regions, particularly where the thinning of ice shelves is believed to be greatest, platelet ice is not observed. Our new data set includes the longest ice-ocean record for Antarctica, which dates back to 1902 near the McMurdo Ice Shelf. These historical data indicate that, over the past 100 years, any change in the volume of very cold surface outflow from this ice shelf is less than the uncertainties in the measurements.

  1. Age characteristics in a multidecadal Arctic sea ice simulation

    SciTech Connect

    Hunke, Elizabeth C; Bitz, Cecllia M

    2008-01-01

    Results from adding a tracer for age of sea ice to a sophisticated sea ice model that is widely used for climate studies are presented. The consistent simulation of ice age, dynamics, and thermodynamics in the model shows explicitly that the loss of Arctic perennial ice has accelerated in the past three decades, as has been seen in satellite-derived observations. Our model shows that the September ice age average across the Northern Hemisphere varies from about 5 to 8 years, and the ice is much younger (about 2--3 years) in late winter because of the expansion of first-year ice. We find seasonal ice on average comprises about 5% of the total ice area in September, but as much as 1.34 x 10{sup 6} km{sup 2} survives in some years. Our simulated ice age in the late 1980s and early 1990s declined markedly in agreement with other studies. After this period of decline, the ice age began to recover, but in the final years of the simulation very little young ice remains after the melt season, a strong indication that the age of the pack will again decline in the future as older ice classes fail to be replenished. The Arctic ice pack has fluctuated between older and younger ice types over the past 30 years, while ice area, thickness, and volume all declined over the same period, with an apparent acceleration in the last decade.

  2. Rapid formation of a sea ice barrier east of Svalbard

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.; van Woert, M. L.; Neumann, G.

    2005-11-01

    Daily SeaWinds scatterometer images acquired by the QuikSCAT satellite show an elongated sea ice feature that formed very rapidly (˜1-2 days) in November 2001 east of Svalbard over the Barents Sea. This sea ice structure, called "the Svalbard sea ice barrier," spanning approximately 10° in longitude and 2° in latitude, restricts the sea route and poses a significant navigation hazard. The secret of its formation appears to lie in the bottom of the sea: A comparison between bathymetry from the International Bathymetric Chart of the Arctic Ocean data and the pattern of sea ice formation from scatterometer data reveals that the sea ice barrier conforms well with and stretches above a deep elongated channel connecting the Franz Josef-Victoria Trough to the Hinlopen Basin between Svalbard and Franz Josef Land. Historic hydrographic data from this area indicate that this sea channel contains cold Arctic water less than 50 m below the surface. Strong and persistent cold northerly winds force strong heat loss from this shallow surface layer, leading to the rapid formation of the sea ice barrier. Heat transfer rates estimated from European Centre for Medium-Range Weather Forecasts temperature and wind data over this region suggest that the surface water along the deep channel can be rapidly cooled to the freezing point. Scatterometer results in 1999-2003 show that sea ice forms in this area between October and December. Understanding the ice formation mechanisms helps to select appropriate locations for deployment of buoys measuring wind and air-sea temperature profile and to facilitate ice monitoring, modeling, and forecasting.

  3. Relationships in Areal Variability: The Ross Sea Polynya and Ice

    NASA Astrophysics Data System (ADS)

    Ward, Jason Michael

    General increases in Antarctic sea ice coverage occur primarily in the Ross Sea. This study investigates the Ross Sea Polynya's relationship with the Ross Sea ice areal coverage. A unique, relatively long term Ross Sea Polynya area dataset was created through the application of the Polynya Signature Simulation Method (PSSM) onto Special Sensor Microwave Imager (SSM/I) data inputs. Bivariate regression analyses were used to determine the relationships, at the 95% confidence level, between Ross Sea Polynya and ice areal trends, annual seasonalities, and anomalies at the full temporal scale as well as the monthly level. Polynya and sea ice have significant positive relationships in the late austral summer and early spring (February to March), and a significant negative relationship in the late austral winter (August). The areal anomalies only had a significant relationship in February, while the trends were not correlated at any time.

  4. Atmospheric circulation and Arctic sea ice: Forcing of sea ice loss by remote teleconnnections and central Arctic responses / feedbacks

    NASA Astrophysics Data System (ADS)

    Wettstein, J. J.; Deser, C.

    2012-12-01

    Continued declines in Arctic sea ice volume and summer sea ice extent are generally anticipated for the coming decades, based upon their trajectory in available observations and within a wide variety of model projections. Substantial uncertainty regarding the magnitude of twenty-first century ice loss remains, however. Two studies focused on processes leading to uncertainty in 21st century Arctic sea ice loss projections are presented: 1) the role of large-scale atmospheric teleconnections in forcing Arctic sea ice loss and 2) coupled thermodynamic and dynamic atmospheric responses to and feedbacks on Arctic sea ice loss. A fully-coupled 39-member ensemble initialized by identical ocean, land and ice conditions and slightly different atmospheric initial conditions is the primary dataset used in these studies. Observations, reanalyses and other coupled and uncoupled simulations corroborate and add context to the large ensemble results. Internal variability is a leading factor influencing the magnitude of 21st century Arctic sea ice loss. Internal variability in ice loss is linked to a large-scale pattern of atmospheric circulation variability over the Pacific. A Rossby wavetrain emanates from the tropical Pacific and extends all the way into an ``Arctic Dipole'' sea level pressure pattern over the central Arctic. A trans-polar drift in ice velocity and ice advection out of the central Arctic through Fram Strait result. These physical ``forcing'' associations are qualitatively consistent across a wide range of time scales, in observations and in other coupled models. Arctic sea ice loss is also associated with two coupled ice-ocean-atmosphere responses and feedbacks. The first feedback involves upper ocean heating resulting from increased solar absorption directly beneath anomalous summer sea ice loss. Some of the anomalous ocean heat melts the overlying sea ice and delays winter freeze-up. A second coupled thermodynamic / dynamic feedback results because much of the

  5. Observation of Sea Ice Surface Thermal States Under Cloud Cover

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Perovich, D. K.; Gow, A. J.; Kwok, R.; Barber, D. G.; Comiso, J. C.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    Clouds interfere with the distribution of short-wave and long-wave radiations over sea ice, and thereby strongly affect the surface energy balance in polar regions. To evaluate the overall effects of clouds on climatic feedback processes in the atmosphere-ice-ocean system, the challenge is to observe sea ice surface thermal states under both clear sky and cloudy conditions. From laboratory experiments, we show that C-band radar (transparent to clouds) backscatter is very sensitive to the surface temperature of first-year sea ice. The effect of sea ice surface temperature on the magnitude of backscatter change depends on the thermal regimes of sea ice thermodynamic states. For the temperature range above the mirabilite (Na2SO4.10H20) crystallization point (-8.2 C), C-band data show sea ice backscatter changes by 8-10 dB for incident angles from 20 to 35 deg at both horizontal and vertical polarizations. For temperatures below the mirabilite point but above the crystallization point of MgCl2.8H2O (-18.0 C), relatively strong backwater changes between 4-6 dB are observed. These backscatter changes correspond to approximately 8 C change in temperature for both cases. The backscattering mechanism is related to the temperature which determines the thermodynamic distribution of brine volume in the sea ice surface layer. The backscatter is positively correlated to temperature and the process is reversible with thermodynamic variations such as diurnal insolation effects. From two different dates in May 1993 with clear and overcast conditions determined by the Advanced Very High Resolution Radiometer (AVHRR), concurrent Earth Resources Satellite 1 (ERS-1) C-band ice observed with increases in backscatter over first-year sea ice, and verified by increases in in-situ sea ice surface temperatures measured at the Collaborative-Interdisciplinary Cryosphere Experiment (C-ICE) site.

  6. Impact of ice temperature on microwave emissivity of thin newly formed sea ice

    NASA Astrophysics Data System (ADS)

    Hwang, Byong Jun; Ehn, Jens K.; Barber, David G.

    2008-02-01

    This study examines the impact of ice temperature on microwave emissivity over thin, newly formed sea ice at 6, 19, and 37 GHz during October 2003 in the southern Beaufort Sea, where the physical properties of newly formed sea ice were coincidently measured with microwave emissions. Six ice stations with distinct properties were selected and divided according to ice surface temperature into warm (above -3°C) or cold (below -3°C) stations. The warm stations had a lower emissivity at the vertical polarization by 0.1 than the cold stations and a corresponding difference in brine volume and dielectric properties. Significant correlations were observed between brine volume and ice emissivity (R2 = 0.8, p value < 0.05). A sensitivity study showed that decreasing ice temperatures from -2.1° to -5.0°C explained the observed difference of 0.1 in ice emissivity between warm and cold stations. The results suggest that the temperature of thin bare ice could be the critical factor in determining ice emissivity near the melting point (about -2°C). Furthermore, a slight decrease in ice temperature (i.e., from -2° to -5°C) significantly reduces the brine volume, thus resulting in high ice emissivity. Finally, we demonstrate the potential of newly formed ice to cause errors in estimating sea ice concentrations using Advanced Microwave Scanning Radiometer-E data.

  7. Radiative transfer in atmosphere-sea ice-ocean system

    SciTech Connect

    Jin, Z.; Stamnes, K.; Weeks, W.F.; Tsay, S.C.

    1996-04-01

    Radiative energy is critical in controlling the heat and mass balance of sea ice, which significantly affects the polar climate. In the polar oceans, light transmission through the atmosphere and sea ice is essential to the growth of plankton and algae and, consequently, to the microbial community both in the ice and in the ocean. Therefore, the study of radiative transfer in the polar atmosphere, sea ice, and ocean system is of particular importance. Lacking a properly coupled radiative transfer model for the atmosphere-sea ice-ocean system, a consistent study of the radiative transfer in the polar atmosphere, snow, sea ice, and ocean system has not been undertaken before. The radiative transfer processes in the atmosphere and in the ice and ocean have been treated separately. Because the radiation processes in the atmosphere, sea ice, and ocean depend on each other, this separate treatment is inconsistent. To study the radiative interaction between the atmosphere, clouds, snow, sea ice, and ocean, a radiative transfer model with consistent treatment of radiation in the coupled system is needed and is under development.

  8. Characteristics of sea ice deformation in high-resolution viscous-plastic sea ice models

    NASA Astrophysics Data System (ADS)

    Hutter, Nils; Losch, Martin

    2016-04-01

    Most climate models use a rheology of the viscous-plastic type to simulate sea ice dynamics. With this rheology, large scale velocity and thickness fields can be realistically simulated, but the representation of small scale deformation rates and Linear Kinematic Features (LKF) is thought to be inadequate. Here, the spatial grid spacing of a traditional VP sea ice model is gradually reduced to 1 km in order to investigate how LKFs emerge with increasing resolution and to explore spatial and temporal scaling laws for sea ice deformation. Increasing the spatial resolution localizes the strain rates along the LKFs. At 1 km grid spacing, the distributions of strain rates have power-law tails that clearly deviate from the basin of attraction of Gaussian distributions and, in this sense, agree with satellite observations and results obtained with the elasto-brittle rheology. Increasing the resolution of the wind forcing leads to more small scale strain rate events in the ice and improves the agreement with observational spatial scaling laws.

  9. What can bromine in ice cores tell us about Arctic sea ice in the past?

    NASA Astrophysics Data System (ADS)

    Vallelonga, Paul; Spolaor, Andrea; Maffazzoli, Niccolo; Kjær, Helle; Barbante, Carlo; Saiz-Lopez, Alfonso

    2016-04-01

    Bromine is of interest as a potential sea ice proxy due to its role in polar atmospheric chemistry, particularly the photochemical "bromine explosion" events which occur over the seasonal sea ice surface. A growing body of literature has demonstrated that bromine is reliably deposited and preserved in polar ice caps and can be used to investigate variability over timescales varying from seasonal to multimillenial. For sea ice reconstructions, bromine and sodium are usually evaluated with respect to their relative abundances in seawater. Competing processes of bromine enrichment due to the bromine explosion, and bromine depletion due to scavenging and deposition, must be taken into account when comparing results from coastal and inland sampling sites. We will review existing bromine-based sea ice reconstructions and present new data for locations from Svalbard, Severnaya Zemlya, Northwest Greenland (NEEM ice core) and central East Greenland (Renland ice core).

  10. Physical characteristics of summer sea ice across the Arctic Ocean

    USGS Publications Warehouse

    Tucker, W. B., III; Gow, A.J.; Meese, D.A.; Bosworth, H.W.; Reimnitz, E.

    1999-01-01

    Sea ice characteristics were investigated during July and August on the 1994 transect across the Arctic Ocean. Properties examined from ice cores included salinity, temperature, and ice structure. Salinities measured near zero at the surface, increasing to 3-4??? at the ice-water interface. Ice crystal texture was dominated by columnar ice, comprising 90% of the ice sampled. Surface albedos of various ice types, measured with radiometers, showed integrated shortwave albedos of 0.1 to 0.3 for melt ponds, 0.5 for bare, discolored ice, and 0.6 to 0.8 for a deteriorated surface or snow-covered ice. Aerial photography was utilized to document the distribution of open melt ponds, which decreased from 12% coverage of the ice surface in late July at 76??N to almost none in mid-August at 88??N. Most melt ponds were shallow, and depth bore no relationship to size. Sediment was pervasive from the southern Chukchi Sea to the north pole, occurring in bands or patches. It was absent in the Eurasian Arctic, where it had been observed on earlier expeditions. Calculations of reverse trajectories of the sediment-bearing floes suggest that the southernmost sediment was entrained during ice formation in the Beaufort Sea while more northerly samples probably originated in the East Siberian Sea, some as far west as the New Siberian Islands.

  11. Characterizing Arctic sea ice topography using high-resolution IceBridge data

    NASA Astrophysics Data System (ADS)

    Petty, Alek A.; Tsamados, Michel C.; Kurtz, Nathan T.; Farrell, Sinead L.; Newman, Thomas; Harbeck, Jeremy P.; Feltham, Daniel L.; Richter-Menge, Jackie A.

    2016-05-01

    We present an analysis of Arctic sea ice topography using high-resolution, three-dimensional surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009 to 2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes. The results demonstrate that Arctic sea ice topography exhibits significant spatial variability, mainly driven by the increased surface feature height and volume (per unit area) of the multi-year ice that dominates the Central Arctic region. The multi-year ice topography exhibits greater interannual variability compared to the first-year ice regimes, which dominates the total ice topography variability across both regions. The ice topography also shows a clear coastal dependency, with the feature height and volume increasing as a function of proximity to the nearest coastline, especially north of Greenland and the Canadian Archipelago. A strong correlation between ice topography and ice thickness (from the IceBridge sea ice product) is found, using a square-root relationship. The results allude to the importance of ice deformation variability in the total sea ice mass balance, and provide crucial information regarding the tail of the ice thickness distribution across the western Arctic. Future research priorities associated with this new data set are presented and discussed, especially in relation to calculations of atmospheric form drag.

  12. 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.

  13. Sea ice thickness in the Weddell Sea, inferred from upward looking sonar measurements

    NASA Astrophysics Data System (ADS)

    Behrendt, Axel; Dierking, Wolfgang; Witte, Hannelore

    2014-05-01

    Sea ice has been routinely monitored by satellites since 1979. However, thickness measurements of sea ice are still very sparse, especially in the Southern Hemisphere. Satellite altimetry still provides relatively uncertain estimates of ice thickness. Today, the only tool for monitoring sea ice thickness over long time periods with highest accuracy (5-10 cm) are moored upward looking sonars (ULS). The instruments measure the subsurface portion (draft) of the ice, which can be converted into total ice thickness. We present a data set of ULS time series from 13 positions in the Atlantic sector of the Southern Ocean (Weddell Sea), which were made in different years between 1990 and 2010. Monthly mean sea ice draft shows high interannual variability and can reach more than 3 m in the dynamic coastal regions of the eastern and western Weddell Sea. The thinnest ice is found away from the coast in the eastern Weddell Sea and rarely exceeds 1 m in the monthly mean. In single years the ULS data allow for a clear discrimination between thermodynamic ice growth and dynamic ice growth due to rafting and ridging of the floes. We demonstrate that the thermodynamic ice thickness can reach its theoretical maximum value of 1 m in the central Weddell basin. Despite significant gaps, the presented data set provides an important validation tool for satellite algorithms and sea ice models.

  14. Sea Ice Thickness, Freeboard, and Snow Depth products from Operation IceBridge Airborne Data

    NASA Technical Reports Server (NTRS)

    Kurtz, N. T.; Farrell, S. L.; Studinger, M.; Galin, N.; Harbeck, J. P.; Lindsay, R.; Onana, V. D.; Panzer, B.; Sonntag, J. G.

    2013-01-01

    The study of sea ice using airborne remote sensing platforms provides unique capabilities to measure a wide variety of sea ice properties. These measurements are useful for a variety of topics including model evaluation and improvement, assessment of satellite retrievals, and incorporation into climate data records for analysis of interannual variability and long-term trends in sea ice properties. In this paper we describe methods for the retrieval of sea ice thickness, freeboard, and snow depth using data from a multisensor suite of instruments on NASA's Operation IceBridge airborne campaign. We assess the consistency of the results through comparison with independent data sets that demonstrate that the IceBridge products are capable of providing a reliable record of snow depth and sea ice thickness. We explore the impact of inter-campaign instrument changes and associated algorithm adaptations as well as the applicability of the adapted algorithms to the ongoing IceBridge mission. The uncertainties associated with the retrieval methods are determined and placed in the context of their impact on the retrieved sea ice thickness. Lastly, we present results for the 2009 and 2010 IceBridge campaigns, which are currently available in product form via the National Snow and Ice Data Center

  15. Comparison of radar backscatter from Antarctic and Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Hosseinmostafa, R.; Lytle, V.

    1992-01-01

    Two ship-based step-frequency radars, one at C-band (5.3 GHz) and one at Ku-band (13.9 GHz), measured backscatter from ice in the Weddell Sea. Most of the backscatter data were from first-year (FY) and second-year (SY) ice at the ice stations where the ship was stationary and detailed snow and ice characterizations were performed. The presence of a slush layer at the snow-ice interface masks the distinction between FY and SY ice in the Weddell Sea, whereas in the Arctic the separation is quite distinct. The effect of snow-covered ice on backscattering coefficients (sigma0) from the Weddell Sea region indicates that surface scattering is the dominant factor. Measured sigma0 values were compared with Kirchhoff and regression-analysis models. The Weibull power-density function was used to fit the measured backscattering coefficients at 45 deg.

  16. Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

    USGS Publications Warehouse

    Alexeev, Vladimir; Arp, Christopher D.; Jones, Benjamin M.; Cai, Lei

    2016-01-01

    Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well (r = +0.69,p < 0.001) to this lake regime shift. To understand how and to what extent sea ice affects lakes, we conducted model experiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent for which we also had field measurements and satellite imagery characterizing lake ice conditions. A lake ice growth model forced with Weather Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter 'ocean-effect' snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

  17. Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

    NASA Astrophysics Data System (ADS)

    Alexeev, Vladimir A.; Arp, Christopher D.; Jones, Benjamin M.; Cai, Lei

    2016-07-01

    Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well (r = +0.69, p < 0.001) to this lake regime shift. To understand how and to what extent sea ice affects lakes, we conducted model experiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent for which we also had field measurements and satellite imagery characterizing lake ice conditions. A lake ice growth model forced with Weather Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter ‘ocean-effect’ snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

  18. Recent summer sea ice thickness surveys in Fram Strait and associated ice volume fluxes

    NASA Astrophysics Data System (ADS)

    Krumpen, T.; Gerdes, R.; Haas, C.; Hendricks, S.; Herber, A.; Selyuzhenok, V.; Smedsrud, L.; Spreen, G.

    2016-03-01

    Fram Strait is the main gateway for sea ice export out of the Arctic Ocean, and therefore observations there give insight into the composition and properties of Arctic sea ice in general and how it varies over time. A data set of ground-based and airborne electromagnetic ice thickness measurements collected during summer between 2001 and 2012 is presented here, including long transects well into the southern part of the Transpolar Drift obtained using fixed-wing aircrafts. The primary source of the surveyed sea ice leaving Fram Strait is the Laptev Sea and its age has decreased from 3 to 2 years between 1990 and 2012. The thickness data consistently also show a general thinning of sea ice for the last decade, with a decrease in modal thickness of second year and multiyear ice, and a decrease in mean thickness and fraction of ice thicker than 3 m. Local melting in the strait was investigated in two surveys performed in the downstream direction, showing a decrease in sea ice thickness of 0.19 m degree-1 latitude south of 81° N. Further north variability in ice thickness is more related to differences in age and deformation. The thickness observations were combined with ice area export estimates to calculate summer volume fluxes of sea ice. While satellite data show that monthly ice area export had positive trends since 1980 (10.9 × 103 km2 decade-1), the summer (July and August) ice area export is low with high uncertainties. The average volume export amounts to 16.78 km3. Naturally, the volume flux estimates are limited to the period when airborne thickness surveys are available. Nevertheless, we could show that the combination of satellite data and airborne observations can be used to determine volume fluxes through Fram Strait and as such, can be used to bridge the lack of satellite-based sea ice thickness information in summer.

  19. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, Victor C.; McNamara, Daniel E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75–90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means.

  20. Sea-ice switches and abrupt climate change.

    PubMed

    Gildor, Hezi; Tziperman, Eli

    2003-09-15

    We propose that past abrupt climate changes were probably a result of rapid and extensive variations in sea-ice cover. We explain why this seems a perhaps more likely explanation than a purely thermohaline circulation mechanism. We emphasize that because of the significant influence of sea ice on the climate system, it seems that high priority should be given to developing ways for reconstructing high-resolution (in space and time) sea-ice extent for past climate-change events. If proxy data can confirm that sea ice was indeed the major player in past abrupt climate-change events, it seems less likely that such dramatic abrupt changes will occur due to global warming, when extensive sea-ice cover will not be present. PMID:14558902

  1. Sediment transport by sea ice in the Chukchi and Beaufort Seas: Increasing importance due to changing ice conditions?

    NASA Astrophysics Data System (ADS)

    Eicken, H.; Gradinger, R.; Gaylord, A.; Mahoney, A.; Rigor, I.; Melling, H.

    2005-12-01

    Sediment-laden sea ice is widespread over the shallow, wide Siberian Arctic shelves, with off-shelf export from the Laptev and East Siberian Seas contributing substantially to the Arctic Ocean's sediment budget. By contrast, the North American shelves, owing to their narrow width and greater water depths, have not been deemed as important for basin-wide sediment transport by sea ice. Observations over the Chukchi and Beaufort shelves in 2001/02 revealed the widespread occurrence of sediment-laden ice over an area of more than 100,000 km 2 between 68 and 74°N and 155 and 170°W. Ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed, multiple layers of rafted nilas, indicative of a flaw-lead environment adjacent to the landfast ice of the Chukchi and Beaufort Seas. This is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern Chukchi Sea in February of 2002 as well as formation of sediment-laden ice along the Beaufort Sea coast as far eastward as the Mackenzie shelf. Moored upward-looking sonar on the Mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment. Analysis of Radarsat Synthetic Aperture (SAR) imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment (>20 m for the Chukchi Sea). Sediment loads averaged at 128 t km -2, with sediment occurring in layers of roughly 0.5 m thickness, mostly in the lower ice layers. The total amount of sediment transported by sea ice (mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment) is at minimum 4×10 6 t in the sampling area and is estimated at 5-8×10 6 t over the entire Chukchi and Beaufort shelves in 2001/02, representing a significant term in the sediment budget of the western Arctic Ocean. Recent

  2. Variability in categories of Arctic sea ice in Fram Strait

    NASA Astrophysics Data System (ADS)

    Hansen, E.; Ekeberg, O.-C.; Gerland, S.; Pavlova, O.; Spreen, G.; Tschudi, M.

    2014-10-01

    An attempt to quantify the temporal variability in the volume composition of Arctic sea ice is presented. Categories of sea ice in the Transpolar Drift in Fram Strait are derived from monthly ice thickness distributions obtained by moored sonars (1990-2011). The inflection points on each side of the old ice modal peak are used to separate modal ice from ice which is thinner and thicker than ice in the modal range. The volume composition is then quantified through the relative amount of ice belonging to each of the three categories thin, modal, and thick ice in the monthly ice thickness distributions. The trend of thin ice was estimated to be negative at -8.8% per decade (relative to the long-term mean), which was compensated for by increasing trends in modal and thick ice of 7.9% and 4.7% per decade, respectively. A 7-8 year cycle is apparent in the thin and thick ice records, which may explain a loss of deformed ice since 2007. We also quantify how the categories contribute to the mean ice thickness over time. Thick (predominantly deformed) ice dominates the mean ice thickness, constituting on average 66% of the total mean. Following the loss of deformed ice since 2007, the contribution of thick ice to the mean decreased from 75% to 52% at the end of the record. Thin deformed ice did not contribute to this reduction; it was pressure ridges thicker than 5 m that were lost and hence caused the decrease in mean ice thickness.

  3. Sea Ice Kinematics and Thickness from RGPS: Observations and Theory

    NASA Technical Reports Server (NTRS)

    Stern, Harry; Lindsay, Ron; Yu, Yan-Ling; Moritz, Richard; Rothrock, Drew

    2005-01-01

    The RADARSAT Geophysical Processor System (RGPS) has produced a wealth of data on Arctic sea ice motion, deformation, and thickness with broad geographical coverage and good temporal resolution. These data provide unprecedented spatial detail of the structure and evolution of the sea ice cover. The broad purpose of this study was to take advantage of the strengths of the RGPS data set to investigate sea ice kinematics and thickness, which affect the climate through their influence on ice production, ridging, and transport (i.e. mass balance); heat flux to the atmosphere; and structure of the upper ocean mixed layer. The objectives of this study were to: (1) Explain the relationship between the discontinuous motion of the ice cover and the large-scale, smooth wind field that drives the ice; (2) Characterize the sea ice deformation in the Arctic at different temporal and spatial scales, and compare it with deformation predicted by a state-of-theart ice/ocean model; and (3) Compare RGPS-derived sea ice thickness with other data, and investigate the thinning of the Arctic sea ice cover as seen in ULS data obtained by U.S. Navy submarines. We briefly review the results of our work below, separated into the topics of sea ice deformation and sea ice thickness. This is followed by a list of publications, meetings and presentations, and other activities supported under this grant. We are attaching to this report copies of all the listed publications. Finally, we would like to point out our community service to NASA through our involvement with the ASF User Working Group and the RGPS Science Working Group, as evidenced in the list of meetings and presentations below.

  4. Natural Variability of Arctic Sea Ice Over the Holocene

    NASA Astrophysics Data System (ADS)

    Fisher, David; Dyke, Art; Koerner, Roy; Bourgeois, Jocelyne; Kinnard, Christophe; Zdanowicz, Christian; de Vernal, Anne; Hillaire-Marcel, Claude; Savelle, James; Rochon, André

    2006-07-01

    The area and volume of sea ice in the ArcticOcean is decreasing, with some predictingice-free summers by 2100 A.D. Johannessenet al., 2004. The implications ofthese trends for transportation and ecosystemsare profound; for example, summershipping through the Northwest Passagecould be possible, while loss of sea icecould cause stress for polar bears. Moreover,global climate may be affected throughalbedo feedbacks and increased sea ice productionand export. With more open water,more new sea ice forms in winter, whichmelts and/or gets exported out of the Arctic.

  5. Seasonal evolution of melt ponds on Arctic sea ice

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  6. Observed and Modeled Trends in Southern Ocean Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2003-01-01

    Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong

  7. 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

    2002-03-01

    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. PMID:11884754

  8. Global warming releases microplastic legacy frozen in Arctic Sea ice

    NASA Astrophysics Data System (ADS)

    Obbard, Rachel W.; Sadri, Saeed; Wong, Ying Qi; Khitun, Alexandra A.; Baker, Ian; Thompson, Richard C.

    2014-06-01

    When sea ice forms it scavenges and concentrates particulates from the water column, which then become trapped until the ice melts. In recent years, melting has led to record lows in Arctic Sea ice extent, the most recent in September 2012. Global climate models, such as that of Gregory et al. (2002), suggest that the decline in Arctic Sea ice volume (3.4% per decade) will actually exceed the decline in sea ice extent, something that Laxon et al. (2013) have shown supported by satellite data. The extent to which melting ice could release anthropogenic particulates back to the open ocean has not yet been examined. Here we show that Arctic Sea ice from remote locations contains concentrations of microplastics at least two orders of magnitude greater than those that have been previously reported in highly contaminated surface waters, such as those of the Pacific Gyre. Our findings indicate that microplastics have accumulated far from population centers and that polar sea ice represents a major historic global sink of man-made particulates. The potential for substantial quantities of legacy microplastic contamination to be released to the ocean as the ice melts therefore needs to be evaluated, as do the physical and toxicological effects of plastics on marine life.

  9. Extraction of sea ice concentration based on spectral unmixing method

    NASA Astrophysics Data System (ADS)

    Zhang, Dong; Ke, Changqing; Sun, Bo; Lei, Ruibo; Tang, Xueyuan

    2011-01-01

    The traditional methods to derive sea ice concentration are mainly from low resolution microwave data, which is disadvantageous to meet the grid size requirement of high resolution climate models. In this paper, moderate resolution imaging spectroradiometer (MODIS)/Terra calibrated radiances Level-1B (MOD02HKM) data with 500 m resolution in the vicinity of the Abbot Ice Shelf, Antarctica, is unmixed, respectively, by two neural networks to extract the sea ice concentration. After two different neural network models and MODIS potential open water algorithm (MPA) are introduced, a MOD02HKM image is unmixed using these neural networks and sea ice concentration maps are derived. At the same time, sea ice concentration for the same area is extracted by MPA from MODIS/Terra sea ice extent (MOD29) data with 1 km resolution. Comparisons among sea ice concentration results of the three algorithms showed that a spectral unmixing method is suitable for the extraction of sea ice concentration with high resolution and the accuracy of radial basis function neural network is better than that of backpropagation.

  10. Optical properties of sea ice in Liaodong Bay, China

    NASA Astrophysics Data System (ADS)

    Xu, Zhantang; Yang, Yuezhong; Wang, Guifen; Cao, Wenxi; Li, Zhijun; Sun, Zhaohua

    2012-03-01

    Many industrial, agricultural, and residential areas surrounding Liaodong Bay are responsible for much of the particulate matter (PM) and colored dissolved organic matter (CDOM) found in the sea ice in the bay. Understanding the optical properties of "dirty" sea ice is important for analyzing remote sensing data and calculating energy balances. We designed a hyperspectral radiation instrument to observe the optical properties of sea ice. The results show that albedo peaks ranged from 0.3 to 0.85 and that the peaks shifted to a longer wavelength for high PM and CDOM concentrations. The absorption and scattering coefficients for sea ice were obtained. The bulk absorption coefficient shows that bulk absorption is primarily determined by PM and CDOM at shorter wavelengths, while pure ice and brine pockets become more important at longer wavelengths. Scattering coefficients for sea ice ranged from 197 to 1072 m-1, and showed consistent variations with gas bubble and brine pocket concentrations. The effects of PM and CDOM on the bulk absorption coefficient of sea ice were studied. At 440 nm, particulates accounted for 55-98% and CDOM accounted for 2-37% of the bulk absorption. Ratios between particulate absorption and bulk absorption for sea ice were almost constant from 400 to 550 nm, and began to decrease sharply for wavelengths >550 nm. Ratios between CDOM and bulk absorption decreased almost linearly with increasing wavelength.

  11. Antarctic sea ice change and variability - Physical and ecological implications

    NASA Astrophysics Data System (ADS)

    Massom, Robert A.; Stammerjohn, Sharon E.

    2010-08-01

    Although Antarctic sea ice is undergoing a slight increase in overall extent, major regional changes are occurring in its spatio-temporal characteristics (most notably in sea ice seasonality). Biologically significant aspects of Antarctic sea ice are evaluated, emphasising the importance of scale and thermodynamics versus dynamics. Changing sea ice coverage is having major direct and indirect though regionally-dependent effects on ecosystem structure and function, with the most dramatic known effects to date occurring in the West Antarctic Peninsula region. There is mounting evidence that loss of sea ice has affected multiple levels of the marine food web in a complex fashion and has triggered cascading effects. Impacts on primary production, Antarctic krill, fish, marine mammals and birds are assessed, and are both negative and positive. The review includes recent analysis of change/variability in polynyas and fast ice, and also highlights the significance of extreme events (which have paradoxical impacts). Possible future scenarios are investigated in the light of the predicted decline in sea ice by 2100 e.g. increased storminess/waviness, numbers of icebergs and snowfall. Our current lack of knowledge on many aspects of sea ice-related change and biological response is emphasised.

  12. Sea ice circulation around the Beaufort Gyre: The changing role of wind forcing and the sea ice state

    NASA Astrophysics Data System (ADS)

    Petty, Alek A.; Hutchings, Jennifer K.; Richter-Menge, Jacqueline A.; Tschudi, Mark A.

    2016-05-01

    Sea ice drift estimates from feature tracking of satellite passive microwave data are used to investigate seasonal trends and variability in the ice circulation around the Beaufort Gyre, over the multidecadal period 1980-2013. Our results suggest an amplified response of the Beaufort Gyre ice circulation to wind forcing, especially during the late 2000s. We find increasing anticyclonic ice drift across all seasons, with the strongest trend in autumn, associated with increased ice export out of the southern Beaufort Sea (into the Chukchi Sea). A flux gate analysis highlights consistency across a suite of drift products. Despite these seasonal anticyclonic ice drift trends, a significant anticyclonic wind trend occurs in summer only, driven, in-part, by anomalously anticyclonic winds in 2007. Across all seasons, the ice drift curl is more anticyclonic than predicted from a linear relationship to the wind curl in the 2000s, compared to the 1980s/1990s. The strength of this anticyclonic ice drift curl amplification is strongest in autumn and appears to have increased since the 1980s (up to 2010). In spring and summer, the ice drift curl amplification occurs mainly between 2007 and 2010. These results suggest nonlinear ice interaction feedbacks (e.g., a weaker, more mobile sea ice pack), enhanced atmospheric drag, and/or an increased role of the ocean. The results also show a weakening of the anticyclonic wind and ice circulation since 2010.

  13. Antarctic Sea Ice Patterns and Its Relationship with Climate

    NASA Astrophysics Data System (ADS)

    Barreira, S.

    2015-12-01

    Antarctic sea ice concentration fields show a strong seasonal and interannual variation closely tied to changes in climate patterns. The Ross, Amundsen, Bellingshausen, and Weddell Seas during Summer-Autumn and the Southern Ocean regions north of these areas during Winter-Spring have the greatest sea ice variability. Principal components analysis in T- mode, Varimax-rotated applied on Antarctic monthly sea ice concentration anomaly (SICA) fields for 1979-2015 (NASA Team algorithm data sets available at nsidc.org) revealed the main spatial characteristics of Antarctic sea ice patterns and their relationship with atmospheric circulation. This analysis yielded five patterns of sea ice for winter-spring and three patterns for summer-autumn, each of which has a positive and negative phase. To understand the links between the SICA patterns and climate, we extracted the mean pressure and temperature fields for the months with high loadings (positive or negative) of the sea ice patterns. The first pattern of winter-spring sea ice concentration is a dipole structure between the Drake Passage and northern regions of the Bellingshausen and Weddell Seas and, the South Atlantic Ocean. The negative phase shows a strong negative SICA over the Atlantic basin. This pattern can be associated with to the atmospheric structures related to a positive SAM index and a wave-3 arrangement around the continent. That is, a strong negative pressure anomaly centered over the Bellingshausen Sea accompanied by three positive pressure anomalies in middle-latitudes. For summer-autumn, the first pattern shows two strong positive SICA areas, in the eastern Weddell Sea and the northwestern Ross Sea. A negative SICA covers the Amundsen-Bellingshausen Seas and northwest of the Antarctic Peninsula. This pattern, frequently seen in summers since 2008, is associated with cool conditions over the Weddell Sea but warmer temperatures and high surface air pressure west, north and northwest of the Peninsula.

  14. On the sea-ice cover of the Nordic Seas in an idealized MITgcm-setup

    NASA Astrophysics Data System (ADS)

    Jensen, Mari F.; Spall, Michael A.; Nisancioglu, Kerim H.

    2016-04-01

    Changes in the sea-ice cover of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. However, with its proximity to the warm Atlantic water, how a sea-ice cover can persist in the Nordic Seas is not well understood. In this study, we apply an eddy-resolving configuration of the Massachusetts Institute of Technology general circulation model with an idealized topography to study the presence of sea ice in a Nordic Seas-like domain. The sea-surface temperatures are restored toward cold, atmospheric temperatures, and as a result, sea ice is present in the interior of the domain. However, the warm, cyclonic boundary current prevents sea ice from being formed along the boundaries. Preliminary results suggest that freshwater inputs at the margins can introduce sea ice in the warm, cyclonic boundary. In addition, a reduction in the meridional heat transport and a shift in the vertical location of the warm inflowing water is observed when freshwater is introduced. The magnitude and location of the freshwater input will be studied, along with changes in the temperature of the inflowing warm water. Results suggest a threshold value in the freshwater forcing for when sea ice is present in the boundaries, and a sea-ice cover which is sensitive to the temperature of the inflowing, warm water.

  15. Fine-resolution simulation of surface current and sea ice in the Arctic Mediterranean Seas

    NASA Astrophysics Data System (ADS)

    Liu, Xiying; Zhang, Xuehong; Yu, Rucong; Liu, Hailong; Li, Wei

    2007-04-01

    A fine-resolution model is developed for ocean circulation simulation in the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Chinese Academy of Sciences, and is applied to simulate surface current and sea ice variations in the Arctic Mediterranean Seas. A dynamic sea ice model in elastic-viscous-plastic rheology and a thermodynamic sea ice model are employed. A 200-year simulation is performed and a dimatological average of a 10-year period (141st 150th) is presented with focus on sea ice concentration and surface current variations in the Arctic Mediterranean Seas. The model is able to simulate well the East Greenland Current, Beaufort Gyre and the Transpolar Drift, but the simulated West Spitsbergen Current is small and weak. In the March climatology, the sea ice coverage can be simulated well except for a bit more ice in east of Spitsbergen Island. The result is also good for the September scenario except for less ice concentration east of Greenland and greater ice concentration near the ice margin. The extra ice east of Spitsbergen Island is caused by sea ice current convergence forced by atmospheric wind stress.

  16. Influence of ice thickness and surface properties on light transmission through Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Katlein, C.; Arndt, S.; Nicolaus, M.; Perovich, D. K.; Jakuba, M.; Suman, S.; Elliott, S.; Whitcomb, L. L.; McFarland, C.; Gerdes, R.; Boetius, A.

    2015-12-01

    The changes in physical properties of sea ice such as decreased thickness and increased melt pond cover observed over the last decades severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role in the amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to undertake challenging research at the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance onboard the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely-piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three-dimensional under-ice topography and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties during summer on the spatial variability of light transmittance. Results show that surface properties dominate the spatial distribution of the under-ice light field on small scales (<1000m²), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we suggest an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

  17. Influence of ice thickness and surface properties on light transmission through Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Katlein, Christian; Arndt, Stefanie; Nicolaus, Marcel; Perovich, Donald K.; Jakuba, Michael V.; Suman, Stefano; Elliott, Stephen; Whitcomb, Louis L.; McFarland, Christopher J.; Gerdes, Rüdiger; Boetius, Antje; German, Christopher R.

    2015-09-01

    The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance using the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under-ice light field on small scales (<1000 m2), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

  18. Victoria Land, Ross Sea, and Ross Ice Shelf, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On December 19, 2001, MODIS acquired data that produced this image of Antarctica's Victoria Land, Ross Ice Shelf, and the Ross Sea. The coastline that runs up and down along the left side of the image denotes where Victoria Land (left) meets the Ross Ice Shelf (right). The Ross Ice Shelf is the world's largest floating body of ice, approximately the same size as France. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  19. Pacific Walrus Response to Arctic Sea Ice Losses

    USGS Publications Warehouse

    Jay, Chadwick V.; Fischbach, Anthony S.

    2008-01-01

    Sea ice plays an important role in the life of the Pacific walrus (Odobenus rosmarus divergens). U.S. Geological Survey (USGS) scientists are seeking to understand how losses of sea ice during summer over important foraging grounds in the Chukchi Sea will affect walruses. USGS scientists recently modified a remotely deployed satellite radio-tag that will aid in studying walrus foraging habitats and behaviors. Information from the tags will help USGS understand how walruses are responding to their changing environment.

  20. Results of the Sea Ice Model Intercomparison Project: Evaluation of sea ice rheology schemes for use in climate simulations

    NASA Astrophysics Data System (ADS)

    Kreyscher, Martin; Harder, Markus; Lemke, Peter; Flato, Gregory M.

    2000-05-01

    A hierarchy of sea ice rheologies is evaluated on the basis of a comprehensive set of observational data. The investigations are part of the Sea Ice Model Intercomparison Project (SIMIP). Four different sea ice rheology schemes are compared: a viscous-plastic rheology, a cavitating-fluid model, a compressible Newtonian fluid, and a simple free drift approach with velocity correction. The same grid, land boundaries, and forcing fields are applied to all models. As verification data, there are (1) ice thickness data from upward looking sonars (ULS), (2) ice concentration data from the passive microwave radiometers SMMR and SSM/I, (3) daily buoy drift data obtained by the International Arctic Buoy Program (IABP), and (4) satellite-derived ice drift fields based on the 85 GHz channel of SSM/I. All models are optimized individually with respect to mean drift speed and daily drift speed statistics. The impact of ice strength on the ice cover is best revealed by the spatial pattern of ice thickness, ice drift on different timescales, daily drift speed statistics, and the drift velocities in Fram Strait. Overall, the viscous-plastic rheology yields the most realistic simulation. In contrast, the results of the very simple free-drift model with velocity correction clearly show large errors in simulated ice drift as well as in ice thicknesses and ice export through Fram Strait compared to observation. The compressible Newtonian fluid cannot prevent excessive ice thickness buildup in the central Arctic and overestimates the internal forces in Fram Strait. Because of the lack of shear strength, the cavitating-fluid model shows marked differences to the statistics of observed ice drift and the observed spatial pattern of ice thickness. Comparison of required computer resources demonstrates that the additional cost for the viscous-plastic sea ice rheology is minor compared with the atmospheric and oceanic model components in global climate simulations.

  1. Variability of Antarctic Sea Ice 1979-1998

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Comiso, Josefino C.; Parkinson, Claire L.; Cavalieri, Donald J.; Gloersen, Per; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    The principal characteristics of the variability of Antarctic sea ice cover as previously described from satellite passive-microwave observations are also evident in a systematically-calibrated and analyzed data set for 20.2 years (1979-1998). The total Antarctic sea ice extent (concentration > 15 %) increased by 13,440 +/- 4180 sq km/year (+1.18 +/- 0.37%/decade). The area of sea ice within the extent boundary increased by 16,960 +/- 3,840 sq km/year (+1.96 +/- 0.44%/decade). Regionally, the trends in extent are positive in the Weddell Sea (1.5 +/- 0.9%/decade), Pacific Ocean (2.4 +/- 1.4%/decade), and Ross (6.9 +/- 1.1 %/decade) sectors, slightly negative in the Indian Ocean (-1.5 +/- 1.8%/decade, and strongly negative in the Bellingshausen-Amundsen Seas sector (-9.5 +/- 1.5%/decade). For the entire ice pack, small ice increases occur in all seasons with the largest increase during autumn. On a regional basis, the trends differ season to season. During summer and fall, the trends are positive or near zero in all sectors except the Bellingshausen-Amundsen Seas sector. During winter and spring, the trends are negative or near zero in all sectors except the Ross Sea, which has positive trends in all seasons. Components of interannual variability with periods of about 3 to 5 years are regionally large, but tend to counterbalance each other in the total ice pack. The interannual variability of the annual mean sea-ice extent is only 1.6% overall, compared to 5% to 9% in each of five regional sectors. Analysis of the relation between regional sea ice extents and spatially-averaged surface temperatures over the ice pack gives an overall sensitivity between winter ice cover and temperature of -0.7% change in sea ice extent per K. For summer, some regional ice extents vary positively with temperature and others negatively. The observed increase in Antarctic sea ice cover is counter to the observed decreases in the Arctic. It is also qualitatively consistent with the

  2. Antarctic sea ice carbon dioxide system and controls

    NASA Astrophysics Data System (ADS)

    Fransson, Agneta; Chierici, Melissa; Yager, Patricia L.; Smith, Walker O., Jr.

    2011-12-01

    In austral summer, from December 2008 to January 2009, we investigated the sea-ice carbon dioxide (CO2) system and CO2 controls in the Amundsen and Ross Seas, Antarctica. We sampled seawater, brine and sea ice for the measurements of total alkalinity (AT), total inorganic carbon (DIC), pH, inorganic nutrients, particulate organic carbon (POC) and nitrogen (PON), chlorophyll a, pigments, salinity and temperature. Large variability in all measured parameters was observed in time and space due to the complex sea-ice dynamics. We discuss the controls of the sea-ice CO2 system, such as brine rejection, biological processes, calcium carbonate (CaCO3) precipitation/dissolution and CO2 exchange. Most (80 to 90%) of the DIC loss was due to brine rejection, which suggests that the sea ice acted as an efficient DIC sink from 0.8 and 2.6 mol m-2 yr-1 (9.6-31 g C m-2 yr-1). The remaining change in DIC was to a large extent explained by net biological production. The AT:DIC ratio in the sea ice was higher than in the under-ice water (UIW), with ratios reaching 1.7, which indicated CaCO3 precipitation and concomitant DIC loss in the sea ice. Elevated AT:DIC ratios and carbonate concentrations were also observed in the UIW, which reflect the solid CaCO3 rejected from the ice during melt. The potential for uptake of atmospheric CO2 in the mixed layer increased by approximately 56 μatm due to the combined effect of CaCO3 precipitation during ice formation, and ice melt in summer.

  3. Radiation Transport in the Atmosphere - Sea Ice - Ocean System.

    NASA Astrophysics Data System (ADS)

    Jin, Zhonghai

    1995-01-01

    A comprehensive radiative transfer model for the coupled atmosphere-sea ice-ocean system has been developed. The theoretical work required for constructing such a coupled model is described first. This work extends the discrete ordinate method, which has been proven to be effective in studies of radiative transfer in the atmosphere, to solve the radiative transfer problem pertaining to a system consisting of two strata with different indices of refraction, such as the atmosphere-ocean system and the atmosphere -sea ice-ocean system. The relevant changes (as compared to the standard problem with constant index of refraction throughout the medium) in formulation and solution of the radiative transfer equation, including the proper application of interface and boundary conditions, are presented. This solution is then applied to the atmosphere -sea ice-ocean system to study the solar energy balance in this coupled system. The input parameters required by the model are observable physical properties (e.g., the profiles of temperature and gas concentrations in the atmosphere, and the profiles of temperature, density, and salinity in the ice). The atmosphere, sea ice and ocean are each divided into a sufficient number of layers in the vertical to adequately resolve changes in their optical properties. This model rigorously accounts for the multiple scattering and absorption by atmospheric molecules, clouds, snow and sea water, as well as inclusions in the sea ice, such as brine pockets and air bubbles. The effects of various factors on the solar energy distribution in the entire system have been studied quantitatively. These factors include the ice salinity and density variations, cloud microphysics as well as variations in melt ponds and snow cover on the ice surface. Finally, the coupled radiative transfer model is used to study the impacts of clouds, snow and ice algae on the light transport in sea ice and in the ocean, as well as to simulate spectral irradiance and

  4. Measurements of sea ice proxies from Antarctic coastal shallow cores

    NASA Astrophysics Data System (ADS)

    Maffezzoli, Niccolò; Vallelonga, Paul; Spolaor, Andrea; Barbante, Carlo; Frezzotti, Massimo

    2015-04-01

    Despite its close relationship with climate, the climatic impact of sea ice remains only partially understood: an indication of this is the Arctic sea ice which is declining at a faster rate than models predict. Thus, the need for reliable sea ice proxies is of crucial importance. Among the sea ice proxies that can be extracted from ice cores, interest has recently been shown in the halogens Iodine (I) and Bromine (Br) (Spolaor, A., et al., 2013a, 2013b). The production of sea ice is a source of Sodium and Bromine aerosols through frost flower crystal formation and sublimation of salty blowing snow, while Iodine is emitted by the algae living underneath sea ice. We present here the results of Na, Br and I measurements in Antarctic shallow cores, drilled during a traverse made in late 2013 - early 2014 from Talos Dome (72° 00'S, 159°12'E) to GV7 (70° 41'S, 158° 51'E) seeking for sea ice signature. The samples were kept frozen until the analyses, that were carried out by Sector Field Mass Spectroscopy Inductive Coupled Plasma (SFMS-ICP): special precautions and experimental steps were adopted for the detection of such elements. The coastal location of the cores allows a clear signal from the nearby sea ice masses. The multiple cores are located about 50 km from each other and can help us to infer the provenance of the sea ice that contributed to the proxy signature. Moreover, by simultaneously determining other chemical elements and compounds in the snow, it is possible to determine the relative timing of their deposition, thus helping us to understand their processes of emission and deposition.

  5. A mechanism for biologically induced iodine emissions from sea ice

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, A.; Blaszczak-Boxe, C. S.; Carpenter, L. J.

    2015-09-01

    Ground- and satellite-based measurements have reported high concentrations of iodine monoxide (IO) in coastal Antarctica. The sources of such a large iodine burden in the coastal Antarctic atmosphere remain unknown. We propose a mechanism for iodine release from sea ice based on the premise that micro-algae are the primary source of iodine emissions in this environment. The emissions are triggered by the biological production of iodide (I-) and hypoiodous acid (HOI) from micro-algae (contained within and underneath sea ice) and their diffusion through sea-ice brine channels, ultimately accumulating in a thin brine layer (BL) on the surface of sea ice. Prior to reaching the BL, the diffusion timescale of iodine within sea ice is depth-dependent. The BL is also a vital component of the proposed mechanism as it enhances the chemical kinetics of iodine-related reactions, which allows for the efficient release of iodine to the polar boundary layer. We suggest that iodine is released to the atmosphere via three possible pathways: (1) emitted from the BL and then transported throughout snow atop sea ice, from where it is released to the atmosphere; (2) released directly from the BL to the atmosphere in regions of sea ice that are not covered with snowpack; or (3) emitted to the atmosphere directly through fractures in the sea-ice pack. To investigate the proposed biology-ice-atmosphere coupling at coastal Antarctica we use a multiphase model that incorporates the transport of iodine species, via diffusion, at variable depths, within brine channels of sea ice. Model simulations were conducted to interpret observations of elevated springtime IO in the coastal Antarctic, around the Weddell Sea. While a lack of experimental and observational data adds uncertainty to the model predictions, the results nevertheless show that the levels of inorganic iodine (i.e. I2, IBr, ICl) released from sea ice through this mechanism could account for the observed IO concentrations during

  6. Variability of Arctic Sea Ice as Viewed from Space

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1998-01-01

    Over the past 20 years, satellite passive-microwave radiometry has provided a marvelous means for obtaining information about the variability of the Arctic sea ice cover and particularly about sea ice concentrations (% areal coverages) and from them ice extents and the lengths of the sea ice season. This ability derives from the sharp contrast between the microwave emissions of sea ice versus liquid water and allows routine monitoring of the vast Arctic sea ice cover, which typically varies in extent from a minimum of about 8,000,000 sq km in September to a maximum of about 15,000,000 sq km in March, the latter value being over 1.5 times the area of either the United States or Canada. The vast Arctic ice cover has many impacts, including hindering heat, mass, and y momentum exchanges between the oceans and the atmosphere, reducing the amount of solar radiation absorbed at the Earth's surface, affecting freshwater transports and ocean circulation, and serving as a vital surface for many species of polar animals. These direct impacts also lead to indirect impacts, including effects on local and perhaps global atmospheric temperatures, effects that are being examined in general circulation modeling studies, where preliminary results indicate that changes on the order of a few percent sea ice concentration can lead to temperature changes of 1 K or greater even in local areas outside of the sea ice region. Satellite passive-microwave data for November 1978 through December 1996 reveal marked regional and interannual variabilities in both the ice extents and the lengths of the sea ice season, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 km(2), while individual regions showed much greater percentage variations, e.g., with the Greenland Sea experiencing a range of 740,000 - 1,1110,000 km(2) in its yearly maximum ice coverage. Although variations from year to

  7. Airborne radar surveys of snow depth over Antarctic sea ice during Operation IceBridge

    NASA Astrophysics Data System (ADS)

    Panzer, B.; Gomez-Garcia, D.; Leuschen, C.; Paden, J. D.; Gogineni, P. S.

    2012-12-01

    Over the last decade, multiple satellite-based laser and radar altimeters, optimized for polar observations, have been launched with one of the major objectives being the determination of global sea ice thickness and distribution [5, 6]. Estimation of sea-ice thickness from these altimeters relies on freeboard measurements and the presence of snow cover on sea ice affects this estimate. Current means of estimating the snow depth rely on daily precipitation products and/or data from passive microwave sensors [2, 7]. Even a small uncertainty in the snow depth leads to a large uncertainty in the sea-ice thickness estimate. To improve the accuracy of the sea-ice thickness estimates and provide validation for measurements from satellite-based sensors, the Center for Remote Sensing of Ice Sheets deploys the Snow Radar as a part of NASA Operation IceBridge. The Snow Radar is an ultra-wideband, frequency-modulated, continuous-wave radar capable of resolving snow depth on sea ice from 5 cm to more than 2 meters from long-range, airborne platforms [4]. This paper will discuss the algorithm used to directly extract snow depth estimates exclusively using the Snow Radar data set by tracking both the air-snow and snow-ice interfaces. Prior work in this regard used data from a laser altimeter for tracking the air-snow interface or worked under the assumption that the return from the snow-ice interface was greater than that from the air-snow interface due to a larger dielectric contrast, which is not true for thick or higher loss snow cover [1, 3]. This paper will also present snow depth estimates from Snow Radar data during the NASA Operation IceBridge 2010-2011 Antarctic campaigns. In 2010, three sea ice flights were flown, two in the Weddell Sea and one in the Amundsen and Bellingshausen Seas. All three flight lines were repeated in 2011, allowing an annual comparison of snow depth. In 2011, a repeat pass of an earlier flight in the Weddell Sea was flown, allowing for a

  8. 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.

  9. Arctic sea ice albedo from AVHRR

    SciTech Connect

    Lindsay, R.W.; Rothrock, D.A.

    1994-11-01

    The seasonal cycle of surface albedo of sea ice in the Arctic is estimated from measurements made with the Advanced Very High Resolution Radiometer (AVHRR) on the polar-orbiting satellites NOAA-10 and NOAA-11. The albedos of 145 200-km-square cells are analyzed. The cells are from March through September 1989 and include only those for which the sun is more than 10 deg above the horizon. Cloud masking is performed manually. Corrections are applied for instrument calibration, nonisotropic reflection, atmospheric interference, narrowband to broadband conversion, and normalization to a common solar zenith angle. The estimated albedos are relative, with the instrument gain set to give an albedo of 0.80 for ice floes in March and April. The mean values for the cloud-free portions of individual cells range from 0.18 to 0.91. Monthly averages of cells in the central Arctic range from 0.76 in April to 0.47 in August. The monthly averages of the within-cell standard deviations in the central Arctic are 0.04 in April and 0.06 in September. The surface albedo and surface temperature are correlated most strongly in March (R = -0.77) with little correlation in the summer. The monthly average lead fraction is determined from the mean potential open water, a scaled representation of the temperature or albedo between 0.0 (for ice) and 1.0 (for water); in the central Arctic it rises from an average 0.025 in the spring to 0.06 in September. Sparse data on aerosols, ozone, and water vapor in the atmospheric column contribute uncertainties to instantaneous, area-average albedos of 0.13, 0.04, and 0.08. Uncertainties in monthly average albedos are not this large. Contemporaneous estimation of these variables could reduce the uncertainty in the estimated albedo considerably.

  10. A neural network algorithm for sea ice edge classification

    SciTech Connect

    Alhumaidi, S.M.; Ferguson, S.M.; Jones, W.L.; Park, J.D.

    1997-07-01

    The NASA Scatterometer (NSCAT), launched in August 1996, is designed to measure wind vectors over ice-free oceans. To prevent contamination f the wind measurements, by the presence of sea ice, algorithms based on neural network technology have been developed to classify ice-free ocean surfaces. Neural networks trained using polarized alone and polarized plus multi-azimuth look Ku-band backscatter are described. Algorithm skill in locating the sea ice edge around Antarctica is experimentally evaluated using backscatter data from the Seasat-A Satellite Scatterometer that operated in 1978. Comparisons between the algorithms demonstrate a slight advantage of combined polarization and multi-look over using co-polarized backscatter alone. Classification skill is evaluated by comparisons with surface truth (sea ice maps), subjective ice classification, and independent over lapping scatterometer measurements (consecutive revolutions).

  11. Aquarius Retrieval of Sea Ice Thickness: Initial Results

    NASA Technical Reports Server (NTRS)

    De Matthaeis, Paolo; Utku, C.; Le Vine, David M.; Moyer, A.

    2014-01-01

    Aquarius brightness temperature data are used to calculate sea ice thickness in the Arctic region. The method is based on the inversion of a radiative transfer model for icecovered sea. Using this technique, the initial sea ice thickness values retrieved from Aquarius data are compared to the SMOSIce Data as well as to estimates from NASA's Operation IceBridge. The results show similar trends between the SMOS- and Aquarius-derived sea ice thickness, however the Aquarius estimates tend to be higher and noisier than the corresponding SMOS values. The accuracy of retrieved Aquarius ice thickness is possibly influenced by uncertainties in the ancillary input parameters and by the coarser resolutions of Aquarius.

  12. Tradition and Technology: Sea Ice Science on Inuit Sleds

    NASA Astrophysics Data System (ADS)

    Wilkinson, Jeremy P.; Hanson, Susanne; Hughes, Nick E.; James, Alistair; Jones, Bryn; MacKinnon, Rory; Rysgaard, Søren; Toudal, Leif

    2011-01-01

    The Arctic is home to a circumpolar community of native people whose culture and traditions have enabled them to thrive in what most would perceive as a totally inhospitable and untenable environment. In many ways, sea ice can be viewed as the glue that binds these northern communities together; it is utilized in all aspects of their daily life. Sea ice acts as highways of the north; indeed, one can travel on these highways with dogsleds and snowmobiles. These travels over the frozen ocean occur at all periods of the sea ice cycle and over different ice types and ages. Excursions may be hunting trips to remote regions or social visits to nearby villages. Furthermore, hunting on the sea ice contributes to the health, culture, and commercial income of a community.

  13. Regional Changes in the Sea Ice Cover and Ice Production in the Antarctic

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2011-01-01

    Coastal polynyas around the Antarctic continent have been regarded as sea ice factories because of high ice production rates in these regions. The observation of a positive trend in the extent of Antarctic sea ice during the satellite era has been intriguing in light of the observed rapid decline of the ice extent in the Arctic. The results of analysis of the time series of passive microwave data indicate large regional variability with the trends being strongly positive in the Ross Sea, strongly negative in the Bellingshausen/Amundsen Seas and close to zero in the other regions. The atmospheric circulation in the Antarctic is controlled mainly by the Southern Annular Mode (SAM) and the marginal ice zone around the continent shows an alternating pattern of advance and retreat suggesting the presence of a propagating wave (called Antarctic Circumpolar Wave) around the circumpolar region. The results of analysis of the passive microwave data suggest that the positive trend in the Antarctic sea ice cover could be caused primarily by enhanced ice production in the Ross Sea that may be associated with more persistent and larger coastal polynyas in the region. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate-of-increase in the net ice export of about 30,000 km2 per year. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 km3/year, which is almost identical, within error bars, to our estimate of the trend in ice production. In addition to the possibility of changes in SAM, modeling studies have also indicated that the ozone hole may have a role in that it causes the deepening of the lows in the western Antarctic region thereby causing strong winds to occur offthe Ross-ice shelf.

  14. Albedo feedback enhanced by smoother Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Landy, Jack C.; Ehn, Jens K.; Barber, David G.

    2015-12-01

    The ICESat operational period 2003-2008 coincided with a dramatic decline in Arctic sea ice—linked to prolonged melt season duration and enhanced melt pond coverage. Although melt ponds evolve in stages, sea ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice-albedo and accelerating further melt. Here we develop this theory into a quantitative relationship between premelt sea ice surface roughness and summer melt pond coverage. Our method, applied to ICESat observations of the end-of-winter sea ice roughness, can account for 85% of the variance in advanced very high resolution radiometer (AVHRR) observations of the summer ice-albedo. An Arctic-wide reduction in sea ice roughness from 2003 to 2008 explains a drop in ice-albedo that resulted in a 16% increase in solar heat input to the sea ice cover, which represents ten times the heat input contributed by earlier melt onset timing over the same period.

  15. Antartic sea ice, 1973 - 1976: Satellite passive-microwave observations

    NASA Technical Reports Server (NTRS)

    Zwally, H. J.; Comiso, J. C.; Parkinson, C. L.; Campbell, W. J.; Carsey, F. D.; Gloersen, P.

    1983-01-01

    Data from the Electrically Scanning Microwave Radiometer (ESMR) on the Nimbus 5 satellite are used to determine the extent and distribution of Antarctic sea ice. The characteristics of the southern ocean, the mathematical formulas used to obtain quantitative sea ice concentrations, the general characteristics of the seasonal sea ice growth/decay cycle and regional differences, and the observed seasonal growth/decay cycle for individual years and interannual variations of the ice cover are discussed. The sea ice data from the ESMR are presented in the form of color-coded maps of the Antarctic and the southern oceans. The maps show brightness temperatures and concentrations of pack ice averaged for each month, 4-year monthly averages, and month-to-month changes. Graphs summarizing the results, such as areas of sea ice as a function of time in the various sectors of the southern ocean are included. The images demonstrate that satellite microwave data provide unique information on large-scale sea ice conditions for determining climatic conditions in polar regions and possible global climatic changes.

  16. Spring Snow Depth on Arctic Sea Ice using the IceBridge Snow Depth Product (Invited)

    NASA Astrophysics Data System (ADS)

    Webster, M.; Rigor, I. G.; Nghiem, S. V.; Kurtz, N. T.; Farrell, S. L.

    2013-12-01

    Snow has dual roles in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from colder air temperatures, slowing its growth. From spring into summer, the albedo of snow determines how much insolation is transmitted through the sea ice and into the underlying ocean, ultimately impacting the progression of the summer ice melt. Knowing the snow thickness and distribution are essential for understanding and modeling sea ice thermodynamics and the surface heat budget. Therefore, an accurate assessment of the snow cover is necessary for identifying its impacts in the changing Arctic. This study assesses springtime snow conditions on Arctic sea ice using airborne snow thickness measurements from Operation IceBridge (2009-2012). The 2012 data were validated with coordinated in situ measurements taken in March 2012 during the BRomine, Ozone, and Mercury EXperiment field campaign. We find a statistically significant correlation coefficient of 0.59 and RMS error of 5.8 cm. The comparison between the IceBridge snow thickness product and the 1937, 1954-1991 Soviet drifting ice station data suggests that the snow cover has thinned by 33% in the western Arctic and 44% in the Beaufort and Chukchi Seas. A rudimentary estimation shows that a thinner snow cover in the Beaufort and Chukchi Seas translates to a mid-December surface heat flux as high as 81 W/m2 compared to 32 W/m2. The relationship between the 2009-2012 thinner snow depth distribution and later sea ice freeze-up is statistically significant, with a correlation coefficient of 0.59. These results may help us better understand the surface energy budget in the changing Arctic, and may improve our ability to predict the future state of the sea ice cover.

  17. Physically-based Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

    NASA Astrophysics Data System (ADS)

    Li, Li; Gaiser, Peter; Allard, Richard; Posey, Pamela; Hebert, David; Richter-Menge, Jacqueline; Polashenski, Christopher; Claffey, Keran

    2016-04-01

    The observations of sea ice thickness and ice surface roughness are critical for our understanding of the state of the changing Arctic. Currently, the Radar and/or LiDAR data of sea ice freeboard are used to infer sea ice thickness via isostasy. The underlying assumption is that the LiDAR signal returns at the air/snow interface and radar signal at the snow/ice interface. The elevations of these interfaces are determined based on LiDAR/Radar return waveforms. However, the commonly used threshold-based surface detection techniques are empirical in nature and work well only over level/smooth sea ice. Rough sea ice surfaces can modify the return waveforms, resulting in significant Electromagnetic (EM) bias in the estimated surface elevations, and thus large errors in the ice thickness retrievals. To understand and quantify such sea ice surface roughness effects, a combined EM rough surface and volume scattering model was developed to simulate radar returns from the rough sea ice 'layer cake' structure. A waveform matching technique was also developed to fit observed waveforms to a physically-based waveform model and subsequently correct the roughness induced EM bias in the estimated freeboard. This new EM Bias Corrected (EMBC) algorithm was able to better retrieve surface elevations and estimate the surface roughness parameter simultaneously. Both the ice thickness and surface roughness retrievals are validated using in-situ data. For the surface roughness retrievals, we applied this EMBC algorithm to co-incident LiDAR/Radar measurements collected during a Cryosat-2 under-flight by the NASA IceBridge missions. Results show that not only does the waveform model fit very well to the measured radar waveform, but also the roughness parameters derived independently from the LiDAR and radar data agree very well for both level and deformed sea ice. For sea ice thickness retrievals, validation based on in-situ data from the coordinated CRREL/NRL field campaign demonstrates

  18. On large outflows of Arctic sea ice into the Barents Sea

    NASA Technical Reports Server (NTRS)

    Kwok, Ron; Maslowski, Wieslaw; Laxon, Seymour W.

    2005-01-01

    Winter outflows of Arctic sea ice into the Barents Sea are estimated using a 10-year record of satellite ice motion and thickness. The mean winter volume export through the Svalbard/Franz Josef Land passage is 40 km3, and ranges from -280 km3 to 340 km3. A large outflow in 2003 is preconditioned by an unusually high concentration of thick perennial ice over the Nansen Basin at the end of the 2002 summer. With a deep atmospheric low situated over the eastern Barents Sea in winter, the result is an increased export of Arctic ice. The Oct-Mar ice area flux, at 110 x 10 to the third power km3, is not only unusual in magnitude but also remarkable in that >70% of the area is multiyear ice; the ice volume flux at340 km3 is almost one-fifth of the ice flux through the Fram Strait. Another large outflow of Arctic sea ice through this passage, comparable to that in 2003, is found in 1996. This southward flux of sea ice represents one of two major sources of freshwater in the Barents Sea; the other is the eastward flux of water via the Norwegian Coastal Current. The possible consequences of variable freshwater input on the Barents Sea hydrography and its impact on transformation of Atlantic Water en route to the Arctic Ocean are examined with a 25-year coupled ice-ocean model.

  19. Radar Interferometric Possibilities for Determining Sea Ice Thickness

    NASA Astrophysics Data System (ADS)

    Hensley, S.; Holt, B.; Jaruwatanadilok, S.; Steward, J.; Oveisgharan, S.; Moller, D.; Mahoney, A. R.; Reis, J.

    2014-12-01

    Sea ice thickness is a primary indicator of climate change in the polar oceans, as the thickness is a time-integrated result of both thermodynamic and dynamic processes. The large-scale ocean and atmospheric forcing acts on the fine-scale (a few to 10s of meters) opening and closing of the sea ice cover along fractures. The mean thickness and variance of sea thickness at km scales (50 cm uncertainty) are derived from recent spaceborne observations from the ICESat lidar and in the Arctic from sporadic upward looking sonar measurements. However, accurate measurements of sea ice thickness at the fine-scales at which the forcing is occurring are virtually non-existent. In this paper we explore two potential radar interferometric means of obtaining sea ice thickness. One method uses high frequency Ka-band (8.5 mm wavelength) to infer sea ice thickness by measuring elevations to the surface of the ice and to the ocean surface in nearby open leads. Data from the NASA Glistin radar is used to illustrate this methodology. Alternatively, we consider the use of dual frequency X-band and P-band (3 cm and 85 cm wavelengths) to exploit the differential penetration of longer versus shorter wavelength to estimate sea ice thickness. This technique is illustrated with data collected by the Furgo Earthdata GeoSAR system. Portions of this research were conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  20. Arctic sea ice and Eurasian climate: A review

    NASA Astrophysics Data System (ADS)

    Gao, Yongqi; Sun, Jianqi; Li, Fei; He, Shengping; Sandven, Stein; Yan, Qing; Zhang, Zhongshi; Lohmann, Katja; Keenlyside, Noel; Furevik, Tore; Suo, Lingling

    2015-01-01

    The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades, including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate. Paleo, observational and modelling studies are covered to summarize several major themes, including: the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era, as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response (e.g., atmospheric circulation, air temperature) to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research.

  1. Techniques for Sea Ice Characteristics Extraction and Sea Ice Monitoring Using Multi-Sensor Satellite Data in the Bohai Sea

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Zhang, Jie

    2014-11-01

    In this paper we present information on various aspects of the sea ice project carried out as part of the Dragon-3 Programme. Details are given on the motivation for the project, the team composition, and the results achieved in the middle term period. A brief overview of future plans concludes the paper.

  2. Performance of a Southern Ocean sea ice forecast model

    NASA Astrophysics Data System (ADS)

    Heil, P.; Roberts, A.; Budd, W.

    2003-12-01

    The presentation examines the forecast peformance of an oriented fracture sea ice model applied to the Southern Ocean to predict sea ice state up to five days in advance. The model includes a modified Coulombic elastic-viscous-plastic rheology, enthalpy conserving thermodynamics and a new method of parameterising thickness distribution mechanics. 15 ice thickness classes are employed within each grid cell with a horizontal resolution of 50km. The model provides considerable insight into the thickness evolution and climatology of Antarctic sea ice. To date, thickness evolution of the Southern Ocean sea ice zone has mostly been assessed using course two-category models in climate simulations and results presented in this talk provide much greater detail over some existing model output. Simulations are presented from the model driven with NCEP-2 atmospheric analyses, NOAA sea surface temperatures, and mean climatogological currents generated using an eddy resolving ocean model. Analyses are generated by nudging ice concentrations with daily satellite derived open water fractions, and simulations using this method are compared to those without. There are important considerations in assimilating passive microwave ice concentration data into thickness distribution models, and particular attention is given to the treatment of lead ice and the impact this has on estimated total Southern Ocean sea ice volume. It is shown that nudging the model with satellite derived concentrations has an impact on ice mechanics as judged from simulated buoy tracks. A comparison with sonar soundings of sea ice draft is also favourable but shows variation with location. Whilst 5 day forecasts are reasonably skilled, predictive performance changes with season. Application of this research to operational ocean data assimilation systems is discussed in the final stages of the talk.

  3. Sea ice and surface water circulation, Alaskan Continental Shelf

    NASA Technical Reports Server (NTRS)

    Wright, F. F. (Principal Investigator); Sharma, G. D.; Burn, J. J.

    1973-01-01

    The author has identified the following significant results. The boundaries of land-fast ice, distribution of pack ice, and major polynya were studied in the vicinity of the Bering Strait. Movement of pack ice during 24 hours was determined by plotting the distinctly identifiable ice floes on ERTS-1 imagery obtained from two consecutive passes. Considerably large shallow area along the western Seward Peninsula just north of the Bering Strait is covered by land fast ice. This ice hinders the movement of ice formed in eastern Chukchi Sea southward through the Bering Strait. The movement of ice along the Russian coast is relatively faster. Plotting of some of the ice floes indicated movement of ice in excess of 30 km in and south of the Bering Strait between 6 and 7 March, 1973. North of the Bering Strait the movement approached 18 km. The movement of ice observed during March 6 and 7 considerably altered the distribution and extent of polynya. These features when continually plotted should be of considerable aid in navigation of ice breakers. The movement of ice will also help delineate the migration and distribution of sea mammals.

  4. Diatom vertical migration within land-fast Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Aumack, C. F.; Juhl, A. R.; Krembs, C.

    2014-11-01

    Light levels inside first-year, landfast sea ice were experimentally altered by manipulating overlying snow depths. Irradiance available for ice algae growing near the ice-bottom, and under the ice, was highly dependent on snow depths ranging from 0 to > 30 cm. Importantly, algal vertical distributions also changed under different irradiances. Under thick snow (low light), the majority of algae were found several cm above the ice-seawater interface, while progressively more were found nearer the interface at locations with thinner overlying snow (higher light). Short-term field experiments suggested that ice algae were able to reposition themselves within the ice column within 3 days after manipulating snow depths. Laboratory gliding rate measurements of a cultured ice diatom suggested that it is capable of daily cm-scale movement. Vertical migration may help ice diatoms balance opposing light and nutrient resource gradients, similar to strategies used by some benthic and pelagic algae. Moreover, when ice algae congregate near the ice-seawater interface, they may be especially susceptible to loss from the ice environment. Vertical repositioning in response to changing light dynamics may be a mechanism to optimize between vertically-opposing environmental factors and help explain the connection between melting snow cover and export of biomass from sea ice.

  5. Scaling properties of sea ice deformation during winter and summer

    NASA Astrophysics Data System (ADS)

    Hutchings, J. K.; Heil, P.; Roberts, A.

    2009-12-01

    We investigate sea ice deformation observed with ice drifting buoy arrays during two field campaigns. Ice Station POLarstern [ISPOL], deployed in the western Weddell Sea during November 2004 to January 2005, included a study of small-scale (sub-synoptic) variability in sea ice velocity and deformation using an array of 24 buoys. Upon deployment the ISPOL buoy array measured 70 km in both zonal and meridional extent, and consisted of sub-arrays that resolved sea ice deformation on scales from 10 to 70 km. The Sea Ice Experiment: Dynamic Nature of the Arctic (SEDNA) used two nested arrays of six buoys each as a backbone for the experiment, that were deployed in late March 2007. The two arrays were circular with diameter 140 km and 20 km. ISPOL and SEDNA provide insight into the scaling properties of sea ice deformation over scales of 10 to 200 km during early Astral summer and late Boreal winter. The ISPOL and SEDNA arrays were split into sets of sub-arrays with varying length scales. We find that variance of divergence decreases as the length scale increases. The mean divergence for each length scale set follows a log-linear scaling relationship with length scale. This is an independent verification of a previous result of Marsden, Stern, Lindsay and Weiss (2004). This scaling is indicative of a fractal process. Deformation occurs at linear features (cracks, leads and ridges) in the ice pack, that are distributed with scales that range from meter to hundreds of kilometers in length. The magnitude of deformation at these linear features varies by two orders of magnitude across scales. We demonstrate that the deformation at all these scales is important in the mass balance of sea ice. Which has important implications for the design of sea ice deformation monitoring systems.

  6. Modeling Abrupt Change in Global Sea Level Arising from Ocean - Ice-Sheet Interaction

    SciTech Connect

    Holland, David M

    2011-09-24

    It is proposed to develop, validate, and apply a coupled ocean ice-sheet model to simulate possible, abrupt future change in global sea level. This research is to be carried out collaboratively between an academic institute and a Department of Energy Laboratory (DOE), namely, the PI and a graduate student at New York University (NYU) and climate model researchers at the Los Alamos National Laboratory (LANL). The NYU contribution is mainly in the area of incorporating new physical processes into the model, while the LANL efforts are focused on improved numerics and overall model development. NYU and LANL will work together on applying the model to a variety of modeling scenarios of recent past and possible near-future abrupt change to the configuration of the periphery of the major ice sheets. The project's ultimate goal is to provide a robust, accurate prediction of future global sea level change, a feat that no fully-coupled climate model is currently capable of producing. This proposal seeks to advance that ultimate goal by developing, validating, and applying a regional model that can simulate the detailed processes involved in sea-level change due to ocean ice-sheet interaction. Directly modeling ocean ice-sheet processes in a fully-coupled global climate model is not a feasible activity at present given the near-complete absence of development of any such causal mechanism in these models to date.

  7. Sea Ice and Hydrographic Variability in the Northwest North Atlantic

    NASA Astrophysics Data System (ADS)

    Fenty, I. G.; Heimbach, P.; Wunsch, C. I.

    2010-12-01

    Sea ice anomalies in the Northwest North Atlantic's Labrador Sea are of climatic interest because of known and hypothesized feedbacks with hydrographic anomalies, deep convection/mode water formation, and Northern Hemisphere atmospheric patterns. As greenhouse gas concentrations increase, hydrographic anomalies formed in the Arctic Ocean associated with warming will propagate into the Labrador Sea via the Fram Strait/West Greenland Current and the Canadian Archipelago/Baffin Island Current. Therefore, understanding the dynamical response of sea ice in the basin to hydrographic anomalies is essential for the prediction and interpretation of future high-latitude climate change. Historically, efforts to quantify the link between the observed sea ice and hydrographic variability in the region has been limited due to in situ observation paucity and technical challenges associated with synthesizing ocean and sea ice observations with numerical models. To elaborate the relationship between sea ice and ocean variability, we create three one-year (1992-1993, 1996-1997, 2003-2004) three-dimensional time-varying reconstructions of the ocean and sea ice state in Labrador Sea and Baffin Bay. The reconstructions are syntheses of a regional coupled 32 km ocean-sea ice model with a suite of contemporary in situ and satellite hydrographic and ice data using the adjoint method. The model and data are made consistent, in a least-squares sense, by iteratively adjusting several model control variables (e.g., ocean initial and lateral boundary conditions and the atmospheric state) to minimize an uncertainty-weighted model-data misfit cost function. The reconstructions reveal that the ice pack attains a state of quasi-equilibrium in mid-March (the annual sea ice maximum) in which the total ice-covered area reaches a steady state -ice production and dynamical divergence along the coasts balances dynamical convergence and melt along the pack’s seaward edge. Sea ice advected to the

  8. Skill improvement of dynamical seasonal Arctic sea ice forecasts

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  9. Can regional climate engineering save the summer Arctic sea ice?

    NASA Astrophysics Data System (ADS)

    Tilmes, S.; Jahn, Alexandra; Kay, Jennifer E.; Holland, Marika; Lamarque, Jean-Francois

    2014-02-01

    Rapid declines in summer Arctic sea ice extent are projected under high-forcing future climate scenarios. Regional Arctic climate engineering has been suggested as an emergency strategy to save the sea ice. Model simulations of idealized regional dimming experiments compared to a business-as-usual greenhouse gas emission simulation demonstrate the importance of both local and remote feedback mechanisms to the surface energy budget in high latitudes. With increasing artificial reduction in incoming shortwave radiation, the positive surface albedo feedback from Arctic sea ice loss is reduced. However, changes in Arctic clouds and the strongly increasing northward heat transport both counteract the direct dimming effects. A 4 times stronger local reduction in solar radiation compared to a global experiment is required to preserve summer Arctic sea ice area. Even with regional Arctic dimming, a reduction in the strength of the oceanic meridional overturning circulation and a shut down of Labrador Sea deep convection are possible.

  10. Strong thermodynamic coupling between sub-ice-shelf melting and sea ice in a high-resolution global sea-ice-ocean isopycnal model

    NASA Astrophysics Data System (ADS)

    Sergienko, O. V.

    2015-12-01

    Sub-ice-shelf melting(freezing) of the Antarctic ice shelves acts as a source(sink) of freshwater, therefore, affects ocean water properties and circulation. In its turn, sub-ice-shelf melting/freezing is controlled by the ocean water properties that reach the sub-ice-shelf cavities. The properties of these water masses are determined by heat and fresh-water exchange with sea ice and atmosphere. Simulations of a high-resolution (1/8 deg) global sea-ice-ocean isopycnal model capable to resolve the ocean circulation in sub-ice-shelf cavities of Antarctic ice shelves and account for the thermodynamic interaction of the circulation with ice shelves show that melting/freezing rates have a strong seasonal cycle with highest melting rates observed in the Austral Fall. On the continental shelf, subsurface ocean temperatures (100-300 m) have a similar seasonal cycle which is lagged with respect to the surface. Shelf temperatures peak in the summertime, followed by rapid cooling towards the freezing point as seasonal ice cover increases. The lagged warming in the subsurface is attributable to reduced heat loss to the atmosphere in the presence of seasonal sea ice. This suggests that the seasonal cycle in melt rates is controlled by the phasing of subsurface temperatures on the continental shelf, which is in turn dominated by sea ice. The outflowing fresh, cold and light meltwater formed in sub-ice-shelf cavities remains in the mixed layer and promotes formation of sea ice and its longer persistence into the Austral Summer. These processes suggest the presence of strong mutual feedbacks between sub-ice-shelf melting and sea ice formation around Antarctic ice shelves.

  11. Use of ERTS data for mapping Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Barnes, J. C. (Principal Investigator); Bowley, C. J.

    1973-01-01

    The author has identified the following significant results. Data from ERTS passes crossing the Bering Sea in early March have been correlated with ice observations collected in the Bering Sea Experiment (BESEX). On two flights of the NASA CV-990 aircraft, the ice conditions in the vicinity of St. Lawrence Island reported by the onboard observer are in close agreement with the ice conditions mapped from the corresponding ERTS imagery. The ice features identified in ERTS imagery and substantiated by the aerial observer include the locations of boundaries between areas consisting of mostly grey ice and of mostly first and multi-year ice, the existence of shearing leads, and the occurrence of open water with the associated development of stratus cloud streaks. The BESEX correlative ice formation verifies the potential of practical applications of ERTS data.

  12. Aircraft measurements of microwave emission from Arctic Sea ice

    USGS Publications Warehouse

    Wilheit, T.; Nordberg, W.; Blinn, J.; Campbell, W.; Edgerton, A.

    1971-01-01

    Measurements of the microwave emission from Arctic Sea ice were made with aircraft at 8 wavelengths ranging from 0.510 to 2.81 cm. The expected contrast in emissivities between ice and water was observed at all wavelengths. Distributions of sea ice and open water were mapped from altitudes up to 11 km in the presence of dense cloud cover. Different forms of ice also exhibited strong contrasts in emissivity. Emissivity differences of up to 0.2 were observed between two types of ice at the 0.811-cm wavelength. The higher emissivity ice type is tentatively identified as having been formed more recently than the lower emissivity ice. ?? 1971.

  13. 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.

  14. The role of sea ice in slowly rotating aquaplanet simulations

    NASA Astrophysics Data System (ADS)

    Salameh, Josiane; Popp, Max; Marotzke, Jochem

    2016-04-01

    A large fraction of recently discovered exoplanets are found in close orbit from their star. Their rotation period is expected to be slow due to important tidal forces. Therefore, in order to assess the habitability of slowly rotating planets, it is imperative to understand how slow rotation periods affect the climate. Under different Earth-like configurations, previous studies focused on the special case of synchronous rotation where the orbital and planetary rotation periods are identical. In addition, simulations with non-synchronous rotations did not account for sea ice. Therefore, we turn on the thermodynamics sea-ice model in the state-of-the-art atmospheric general circulation model ECHAM6 coupled to a mixed-layer ocean and investigate the aquaplanet's climate across rotation periods between one and 365 Earth days. Simulations with the sea-ice model turned on show a global-mean surface temperature up to 25 K lower than simulations with the sea-ice model turned off, particularly for rotation periods between 64 and 300 days. For both type of experiments, the climate cools with increasing rotation period. However, when sea ice is included, the significant drop in the global-mean surface temperature is due to sea-ice reaching low latitudes. Then, beyond a 200 days rotation period, sea ice grows over the equatorial region during the nighttime and persists well into the daytime. This causes a high contribution of the sea-ice albedo to the planetary albedo. Our study illustrates, thus, that sea-ice plays a crucial role in shaping the climate on slowly rotating planets.

  15. Environmental predictors of ice seal presence in the Bering Sea.

    PubMed

    Miksis-Olds, Jennifer L; Madden, Laura E

    2014-01-01

    Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20-30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season. PMID:25229453

  16. Environmental Predictors of Ice Seal Presence in the Bering Sea

    PubMed Central

    Miksis-Olds, Jennifer L.

    2014-01-01

    Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20–30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season. PMID:25229453

  17. Comparison of Envisat ASAR and Submarine Sea Ice Thickness Statistics

    NASA Astrophysics Data System (ADS)

    Hughes, Nicolas E.; Rodrigues, Joao; Wadhams, Peter

    2010-12-01

    In April 2004 and March 2007 the Royal Navy sent the submarine HMS Tireless on missions into the Arctic Ocean. On both occasions the submarine traversed the area of remaining multi-year sea ice at latitude 85°N north of Greenland acquiring ice draft measurements using upward-looking sonar. The area is outside of the "Gore Box" used for the release of U.S. Submarine data and was beyond the latitude range of the radar altimeter satellites available at that time. This paper compares ice draft statistics with contemporary data from Envisat ASAR to evaluate the level of correlation between SAR backscatter and sea ice thickness. The decline in sea ice volume over the past decade has predominantly been caused by the loss of old multi-year ice due to increased outflow through Fram Strait. Although Tireless found little decrease in the overall ice thickness between 2004 and 2007, the ice rheology was significantly changed with greatly increased quantities of first- and second-year ice in 2007 than had been encountered in 2004. These are evident in changes to the ice draft probability density functions (PDFs) and the ice appearance as seen by the SAR, and presented here.

  18. On the characteristics of sea ice divergence/convergence in the Southern Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Lukovich, J. V.; Babb, D. G.; Galley, R. J.; Raddatz, R. L.; Barber, D. G.

    2014-07-01

    An understanding of spatial gradients in sea ice motion, or deformation, is essential to understanding of ocean-sea-ice-atmosphere interactions and realistic representations of sea ice in models used for the purposes of prediction. This is particularly true for the southern Beaufort Sea, where significant offshore hydrocarbon resource development increases the risk of oil and other contaminants dispersing into the marginal ice zone. In this study, sea ice deformation is examined through evaluation of ice beacon triplets from September to November 2009 in the southern Beaufort Sea (SBS), defined according to distance from the coastline on deployment. Results from this analysis illustrate that ice beacon triplets in the SBS demonstrate spatiotemporal differences in their evolution at the periphery and interior of the ice pack. The time rate of change in triplet area highlights two intervals of enhanced divergence and convergence in fall, 2009. Investigation of sea ice and atmospheric conditions during these intervals shows that until mid-September, all triplets respond to northerly flow, while during the second interval of enhanced divergence/convergence in October only one triplet responds to persistent northeasterly flow due to its proximity to the ice edge, in contrast to triplets located at the interior of the pack. Differences in sea ice deformation and dispersion near the pack ice edge and interior are further demonstrated in the behavior of triplets B and C in late October/early November. The results from this analysis highlight differences in dispersion and deformation characteristics based on triplet proximity to the southernmost ice edge and coastline, with implications for modeling studies pertaining to sea ice dynamics and dispersion.

  19. Hierarchy and sea ice mechanics: A case study from the Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Overland, James E.; Walter, Bernard A.; Curtin, Thomas B.; Turet, Philip

    1995-03-01

    Hierarchy implies that the study of sea ice can be divided into analysis of subsets of processes based on scale and their interaction with adjacent scales. We apply these concepts to regional sea ice dynamics. The apparent self-similar property of ice floes seen in aircraft or satellite images argues for an aggregate nature of sea ice, that viscouslike regional behavior arises from discrete floe interactions. However, for some regions and some times, characteristic behavior, where lead patterns seen in basin-wide advanced very high resolution radiometer images appear to be related to coastal orientation hundreds of kilometers away, suggests that small regional scale processes O(10 km) and discontinuities in the velocity or stress state along boundaries can affect the larger-scale sea ice distribution and dynamics O(500 km). Thus sea ice displays both aggregate type behavior and discontinuous type behavior based on the history of forcing and shape of the enclosing basin. The appropriate matching of atmospheric processes to sea ice processes in air-ice interaction is through the sea ice deformation field rather than the response of ice velocity to the local wind. This is because atmospheric forcing and sea ice deformation have matching energetic scales at several hundred kilometers and timescales of days. An example of northerly winds during the April 1992 Arctic Leads Experiment period suggests discontinuous type behavior upwind of the Alaska coast followed by a general opening behavior with easterly winds. There appear to be natural scale divisions between climate scale sea ice processes of O(100-300 km) which resolve aggregate behavior, regional scale O(10-50 km) which is necessary to resolve observed shearing behavior, and the floe scale O(1 km). Because the climate scale is two levels removed from the floe scale, care must be exercised in using ice properties from the floe scale in climate scale models; ice strength is an example of such a scale dependent

  20. Macrofauna under sea ice and in the open surface layer of the Lazarev Sea, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Flores, Hauke; van Franeker, Jan-Andries; Cisewski, Boris; Leach, Harry; Van de Putte, Anton P.; Meesters, Erik (H. W. G.); Bathmann, Ulrich; Wolff, Wim J.

    2011-10-01

    A new fishing gear was used to sample the macrozooplankton and micronekton community in the surface layer (0-2 m) under ice and in open water, the Surface and Under Ice Trawl (SUIT). In total, 57 quantitative hauls were conducted in the Lazarev Sea (Southern Ocean) during 3 different seasons (autumn 2004, winter 2006, summer 2007/2008). At least 46 species from eight phyla were caught in all 3 seasons combined. Biomass density was dominated by Antarctic krill Euphausia superba. The average biomass density was highest under the winter sea ice and lowest under the young ice in autumn. In summer, macrozooplankton biomass was dominated by ctenophores in open water and by Antarctic krill under ice. The community composition varied significantly among seasons, and according to the presence of sea ice. The response of the community composition to the presence of sea ice was influenced by species that were significantly more abundant in open water than under ice ( Cyllopus lucasii, Hyperiella dilatata), only seasonally abundant under ice ( Clione antarctica), or significantly associated with sea ice ( Eusirus laticarpus). A number of abundant species showed distinct diel patterns in the surface occurrence both under ice and in open water, indicating that the surface layer serves as a foraging ground predominantly at night. Our results emphasize the potential of a number of non-euphausiid macrozooplankton and micronekton species to act as energy transmitters between the production of sea ice biota and the pelagic food web. By providing a regional-scale quantitative record of macrofauna under Antarctic sea ice covering 3 seasons, this study adds new and direct evidence that the ice-water interface layer is a major functional node in the ecosystem of the Antarctic seasonal sea ice zone.

  1. Sea ice investigations from Seasat to the present

    NASA Technical Reports Server (NTRS)

    Holt, Benjamin; Kwok, Ron

    2003-01-01

    In this paper, we provide a short review of sea ice investigations starting from Seasat. We focus particularly on the detailed and quantitative measurements of the sea ice motion field, which were some of the earliest results from Seasat and have sugsequently been shown to be of critical value to the derivation of several key climatically important variables. Other key investigations discussed include examination of the seasonal melt cycle, ice extent and concentration, and estimates of thickness from the proxy measurements of ice type and age and more directly from freeboard. We end with a brief discussion on how thse measurements might be improved in the future.

  2. Temporal variatiions of Sea ice cover in the Baltic Sea derived from operational sea ice products used in NWP.

    NASA Astrophysics Data System (ADS)

    Lange, Martin; Paul, Gerhard; Potthast, Roland

    2014-05-01

    Sea ice cover is a crucial parameter for surface fluxes of heat and moisture over water areas. The isolating effect and the much higher albedo strongly reduces the turbulent exchange of heat and moisture from the surface to the atmosphere and allows for cold and dry air mass flow with strong impact on the stability of the whole boundary layer and consequently cloud formation as well as precipitation in the downstream regions. Numerical weather centers as, ECMWF, MetoFrance or DWD use external products to initialize SST and sea ice cover in their NWP models. To the knowledge of the author there are mainly two global sea ice products well established with operational availability, one from NOAA NCEP that combines measurements with satellite data, and the other from OSI-SAF derived from SSMI/S sensors. The latter one is used in the Ostia product. DWD additionally uses a regional product for the Baltic Sea provided by the national center for shipping and hydrografie which combines observations from ships (and icebreakers) for the German part of the Baltic Sea and model analysis from the hydrodynamic HIROMB model of the Swedish meteorological service for the rest of the domain. The temporal evolution of the three different products are compared for a cold period in Februar 2012. Goods and bads will be presented and suggestions for a harmonization of strong day to day jumps over large areas are suggested.

  3. Sea ice near-inertial response to atmospheric storms

    NASA Astrophysics Data System (ADS)

    Stoudt, Chase A.

    A moored oceanographic array was deployed on the Beaufort Sea continental slope from August 2008-August 2009 to measure Arctic sea ice near-inertial motion in response to rapidly changing wind stress. Upward looking Acoustic Doppler Current Profilers detected sea ice and measured ice drift using a combination of bottom track and error velocity. An analysis of in-situ mooring data in conjunction with data from National Center for Environmental Prediction (NCEP) reanalysis suggest that many high and low pressure systems cross the Beaufort in winter, but not all of these create a near-inertial ice response. Two unusually strong low pressure systems that passed near the array in December 2008 and February/March 2009 were accompanied by elevated levels of near-inertial kinetic energy in the ice. The analysis suggests pressure systems which have a diameter to ground track velocity ratio close to 3/4 of the local inertial period can excite a large near-inertial response in the sea ice. It is conjectured that this results from the combined effect of resonance arising from similar intrinsic timescales of the storm and the local inertial period and from stresses that are able to overcome the damping of sea ice arising from ice-mechanics and damping in the ice-ocean boundary layer. Those systems whose intrinsic times scales do not approach resonance with the local inertial period did not excite a large near- inertial response in the sea ice. From an analysis of two storms in February 2009, and two in December 2008, it appears that wind stresses associated with previous low pressure systems preconditioned the ice pack, allowing for larger near-inertial response during subsequent events.

  4. ICESat Observations of Arctic Sea Ice: A First Look

    NASA Technical Reports Server (NTRS)

    Kwok, Ron; Zwally, H. Jay; Yi, Donghui

    2004-01-01

    Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm. Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice freeboard along the altimeter tracks. This step is necessitated by the large uncertainties in the sea surface topography compared to that required for accurate determination of freeboard. Unknown snow depth introduces the largest uncertainty in the conversion of freeboard to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track. Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint of approx. 70 m.

  5. ICESat Observations of Arctic Sea Ice: A First Look

    NASA Technical Reports Server (NTRS)

    Kwok, Ron; Zwally, H. Jay; Yi, Dong-Hui

    2004-01-01

    Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice free-board along the altimeter tracks. This step is necessitated by the large uncertainties in the time-varying sea surface topography compared to that required for accurate determination of free-board. Unknown snow depth introduces the largest uncertainty in the conversion of free-board to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint.

  6. Applying Archimedes' Law to Ice Melting in Sea Water

    NASA Astrophysics Data System (ADS)

    Noerdlinger, Peter D.; Brower, K. R.

    2006-12-01

    Archimedes stated that a floating body displaces its own weight of liquid, but his law has been widely misapplied to ice floating in the oceans by scientists who assumed that equal weights correspond to equal liquid volumes. It is often said that when floating ice melts, the sea level does not rise "because of Archimedes' law." True when ice floats in fresh water, but a myth for ice in oceans! Most ice floating in the oceans is nearly pure water. When it melts, the pure water produced has about 2.6% more volume than the salt water that was displaced, and the ocean slightly rises. It is often suggested that students demonstrate the "fact" of no rise in the sea surface by melting ice cubes floating in a glass of water; such a demonstration even appears in the movie "An Inconvenient Truth." Let's teach students to spot such errors. We highlight a couple more "surprise issues." First, the density of the floating ice, if it is free of salt and dirt, is irrelevant, so long as it floats. Next, when "grounded" ice (resting on land), enters the sea, it initially displaces less water than its melted form will eventually add to the sea. Thus, an event of that kind, such as formation of an iceberg, produces a rise of the sea level in two stages. We conclude with a series of thought-experiments that could help teachers and students discern the correct result, and a photo of a demonstration.

  7. Remote Sensing of Sea Ice in the Northern Sea Route: Studies and Applications

    NASA Astrophysics Data System (ADS)

    Barry, Roger G.

    2008-07-01

    Given the rapid changes that are under way in Arctic sea ice extent, Remote Sensing of Sea Ice in the Northern Sea Route is a timely work. The Northern Sea Route (NSR), along the Arctic coast of Russia, has a long history, dating back to 1932, when the Soviet Union established the NSR administration to develop hydrometeorological services. Shipping along the sea route peaked in the 1980s, but there is renewed interest associated with a lengthening ice-free season and mineral exploitation. Since July 1991, the NSR has been open to all merchant vessels.

  8. Resolution of sea ice microstructure using cross borehole resistivity tomography

    NASA Astrophysics Data System (ADS)

    Ingham, M.; Jones, K.; Pringle, D. J.; Eicken, H.

    2009-12-01

    As an inhomogeneous mixture of pure ice, brine, air and solid salts, the physical properties of sea ice depend on its highly temperature-dependent microstructure. Understanding the microstructure and the way it responds to variations not only in temperature but also salinity, is crucial in developing an improved understanding of the role that sea ice plays in climate. However progress in this is hindered by the difficulty in obtaining meaningful measurements of sea ice physical properties without disturbing the natural state of the ice. We have recently developed an application of cross-borehole dc resistivity tomography to make in-situ measurements which resolve the anisotropic resistivity structure of first-year landfast sea ice. We present results from measurements made in 2008 at Barrow, Alaska which demonstrate the evolution of the ice microstructure over the period of spring warming. Key conclusions are that a much greater degree of vertical electrical connectivity of brine channels appears to exist even when the ice is very cold, whereas a much higher horizontal component of resistivity indicates that horizontal connectivity is only established as the ice warms and brine inclusions expand.

  9. Study of sea ice regions using AltiKa measurements

    NASA Astrophysics Data System (ADS)

    Poisson, Jean-Christophe; Thibaut, Pierre; Hoang, Duc; Boy, François; Guillot, Amandine; Picot, Nicolas

    2015-04-01

    Since the launch of the SARAL/AltiKa mission on February 25th, 2013, altimeter measurements of excellent quality are acquired all over the globe for the first time in Ka-band. One of the main benefits of the Ka-band is to have a very low penetration length in the ice (unlike the Ku-band historically used by previous altimetry missions), which allows to significantly reduce measurements uncertainties of the sea ice topography. Flying on the Envisat orbit and providing measurements at 40 Hz, the exploitation of AltiKa waveforms on sea ice is of great interest. Sea ice covered regions are characterized by a large number of different surfaces with a multitude of backscattering properties rapidly evolving with time. Thanks to the high resolution and precision of the AltiKa measurements, backscattering properties from each of these surfaces (first year ice, multiyear ice, fast ice, leads, polynyas, etc. …) can be observed through rapid changes of the returned echo shape. In the framework of the PEACHI project (Prototype for Expertise on AltiKa, for Coastal, Hydrology and Ice funded by CNES) which aims at analyzing and improving AltiKa measurements, a waveform processing based on an altimeter echo classification is developed and performed on all available AltiKa data in the Arctic ocean. Through this processing a study is conducted on the the evolution of the sea ice cover observed in Ka-band.

  10. Visualizing Glaciers and Sea Ice via Google Earth

    NASA Astrophysics Data System (ADS)

    Ballagh, L. M.; Fetterer, F.; Haran, T. M.; Pharris, K.

    2006-12-01

    The NOAA team at NSIDC manages over 60 distinct cryospheric and related data products. With an emphasis on data rescue and in situ data, these products hold value for both the scientific and non-scientific user communities. The overarching goal of this presentation is to promote products from two components of the cryosphere (glaciers and sea ice). Our Online Glacier Photograph Database contains approximately 3,000 photographs taken over many decades, exemplifying change in the glacier terminus over time. The sea ice product shows sea ice extent and concentration along with anomalies and trends. This Sea Ice Index product, which starts in 1979 and is updated monthly, provides visuals of the current state of sea ice in both hemispheres with trends and anomalies. The long time period covered by the data set means that many of the trends in ice extent and concentration shown in this product are statistically significant despite the large natural variability in sea ice. The minimum arctic sea ice extent has been a record low in September 2002 and 2005, contributing to an accelerated trend in sea ice reduction. With increasing world-wide interest in indicators of global climate change, and the upcoming International Polar Year, these data products are of interest to a broad audience. To further extend the impact of these data, we have made them viewable through Google Earth via the Keyhole Markup Language (KML). This presents an opportunity to branch out to a more diverse audience by using a new and innovative tool that allows spatial representation of data of significant scientific and educational interest.

  11. Effect of Tides On Sea Ice Deformation and Growth Rate

    NASA Astrophysics Data System (ADS)

    Hutchings, J.; Heil, P.; Hibler, W. D.

    Due to high ice strength in present formulations of non-linear plastic sea ice dynamic models, the relatively small tides in the Arctic Basin produces little relative motion. However, recent work with a stand alone sea ice model including a more realistic for- mulation of ice-ocean coupling [Heil & Hibler, accepted] has produced more realistic inertial motion in agreement with observations. With such improved model physics, we expect tidal motion of the ice pack to have a more pronounced effect on simulated periodic lead opening and closing, enhancing winter ice growth rate. To investigate this process, tidal forcing [Kowalik 1998] is included in the momentum balance of a stand alone sea ice model [Heil & Hibler, accepted]. The model includes a modi- fied coulombic rheology, hourly interpolated NCEP reanalysis atmospheric forcing, climatological cloud fraction [Gorshkov,1980] , oceanic currents and heat flux from Polyakov et al. [1998] and inertial embedding as Hibler et al. [1998]. Arctic sea ice is simulated for the period 1948-2000 and compared to a control without tidal forcing. It is investigated how tidal motion and inertial motion interact. As the inertial period is close to the major semi-diurnal tidal period we expect ice deformation in tidally active regions (such as the Barents Sea) to be amplified through inertial resonance. The tidal influence on ice mass balance is estimated. The interannual variability of ice mass is examined to show how tidal influence differs between years of high Arctic Oscillation (AO) index, when ice divergence is increased and trans-polar transport widened, and low AO index, when the Arctic high dominates and convergent motion prevails.

  12. Improving Surface Mass Balance Over Ice Sheets and Snow Depth on Sea Ice

    NASA Technical Reports Server (NTRS)

    Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan

    2013-01-01

    Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea ice cover. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland ice sheet and the smallest satellite-recorded Arctic sea ice extent, making this meeting both timely and relevant.

  13. Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse.

    PubMed

    Holloway, Max D; Sime, Louise C; Singarayer, Joy S; Tindall, Julia C; Bunch, Pete; Valdes, Paul J

    2016-01-01

    Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming. PMID:27526639

  14. Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse

    PubMed Central

    Holloway, Max D.; Sime, Louise C.; Singarayer, Joy S.; Tindall, Julia C.; Bunch, Pete; Valdes, Paul J.

    2016-01-01

    Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming. PMID:27526639

  15. Effects of Mackenzie River Discharge and Bathymetry on Sea Ice in the Beaufort Sea

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Hall, D. K.; Rigor, I. G; Li, P.; Neumann, G.

    2014-01-01

    Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open water area about 316,000 sq km. Surface temperature in a common open water area increased by 6.5 C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.

  16. An analysis of space scales for sea ice drift

    SciTech Connect

    Carrieres, T.

    1994-12-31

    Sea ice presents a hazard to navigation off Canada`s east coast from January to June. The Ice Centre Environment Canada (ICEC) which is part of the Atmospheric Environment Service monitors ice conditions in order to assist safe and efficient operations through or around the ice. The ice program depends on an advanced data acquisition, analysis and forecasting effort. Support for the latter is provided by kinematic models as well as a fairly simple dynamic sea ice model. In order to improve ICEC`s forecasting capabilities, the Department of Fisheries and Oceans (DFO) conducts ice modelling research and regular field experiments. The experiments provide a better understanding of the ice and also allow models to be validated and refined. The Bedford Institute of Oceanography (BIO, part of DFO) regularly deploys beacons on ice floes off the Labrador and Newfoundland coasts. These beacons provide environmental as well as location information through Service ARGOS. Documentation on the accuracy and information of the sensors is documented in Prinsenberg, 1993. The beacon locations are used here to infer an relatively unbiased representation of sea ice drift.

  17. On the Role of Arctic Sea Ice Deformations: An Evaluation of the Regional Arctic System Model Results with Observations.

    NASA Astrophysics Data System (ADS)

    Osinski, Robert; Maslowski, Wieslaw; Roberts, Andrew

    2016-04-01

    The atmosphere - sea ice - ocean fluxes and their contribution to rapid changes in the Arctic system are not well understood and generally are not resolved by global climate models (GCMs). While many significant model refinements have been made in the recent past, including the representation of sea ice rheology, surface albedo and ice-albedo feedback, other processes such as sea ice deformations, still require further studies and model advancements. Of particular potential interest here are linear kinematic features (LKFs), which control winter air-sea heat exchange and affect buoyancy forces in the ocean. Their importance in Arctic climate change, especially under an increasing first-year ice cover, is yet to be determined and their simulation requires representation of processes currently at sub-grid scale of most GCMs. To address some of the GCM limitations and to better understand the role of LKFs in air-sea exchange we use the Regional Arctic System Model (RASM), which allows high spatio-temporal resolution and regional focus on the Arctic. RASM is a fully coupled regional climate model, developed to study dynamic and thermodynamic processes and their coupling across the atmosphere-sea ice-ocean interface. It consists of the Weather Research and Forecasting (WRF) atmospheric model, the Parallel Ocean Program (POP), the Community Ice Model (CICE) and the Variable Infiltration Capacity (VIC) land hydrology model. The sea ice component has been upgraded to the Los Alamos Community Ice Model version 5.1 (CICE5.1), which allows either Elastic-Viscous-Plastic (EVP) or a new anisotropic (EPA) rheology. RASM's domain is pan-Arctic, with the ocean and sea ice components configured at an eddy-permitting horizontal resolution of 1/12-degree as well as 1/48-degree, for limited simulations. The atmosphere and land model components are configured at 50-km grids. All the components are coupled at a 20-minute time step. Results from multiple RASM simulations are analyzed and

  18. Relating Regional Arctic Sea Ice and climate extremes over Europe

    NASA Astrophysics Data System (ADS)

    Ionita-Scholz, Monica; Grosfeld, Klaus; Lohmann, Gerrit; Scholz, Patrick

    2016-04-01

    The potential increase of temperature extremes under climate change is a major threat to society, as temperature extremes have a deep impact on environment, hydrology, agriculture, society and economy. Hence, the analysis of the mechanisms underlying their occurrence, including their relationships with the large-scale atmospheric circulation and sea ice concentration, is of major importance. At the same time, the decline in Arctic sea ice cover during the last 30 years has been widely documented and it is clear that this change is having profound impacts at regional as well as planetary scale. As such, this study aims to investigate the relation between the autumn regional sea ice concentration variability and cold winters in Europe, as identified by the numbers of cold nights (TN10p), cold days (TX10p), ice days (ID) and consecutive frost days (CFD). We analyze the relationship between Arctic sea ice variation in autumn (September-October-November) averaged over eight different Arctic regions (Barents/Kara Seas, Beaufort Sea, Chukchi/Bering Seas, Central Arctic, Greenland Sea, Labrador Sea/Baffin Bay, Laptev/East Siberian Seas and Northern Hemisphere) and variations in atmospheric circulation and climate extreme indices in the following winter season over Europe using composite map analysis. Based on the composite map analysis it is shown that the response of the winter extreme temperatures over Europe is highly correlated/connected to changes in Arctic sea ice variability. However, this signal is not symmetrical for the case of high and low sea ice years. Moreover, the response of temperatures extreme over Europe to sea ice variability over the different Arctic regions differs substantially. The regions which have the strongest impact on the extreme winter temperature over Europe are: Barents/Kara Seas, Beaufort Sea, Central Arctic and the Northern Hemisphere. For the years of high sea ice concentration in the Barents/Kara Seas there is a reduction in the number

  19. Sea-ice interaction with the thermohaline circulation

    SciTech Connect

    Jiayan Yang; Neelin, J.D. )

    1993-02-05

    Linkages have been suggested between observed interdecadal variability of sea-ice and salinity in the North Atlantic. A plausible mechanism for generating such variability through the interaction of sea-ice and the thermohaline circulation (THC) is examined in a zonally-averaged THC model coupled to a thermodynamic ice model. A self-sustaining interdecadal oscillation arises through the feedbacks between salinity anomalies induced by the sea-ice melting-freezing process and anomalous meridional heat transport associated with the THC. The oscillation time scale is not associated with any oceanic time scales but fundamentally depends on ice-THC coupling. The period is quite robust to stochastic forcing, although the regularity is strongly affected. 25 refs., 7 figs.

  20. Late Cenozoic Arctic Ocean sea ice and terrestrial paleoclimate.

    USGS Publications Warehouse

    Carter, L.D.; Brigham-Grette, J.; Marincovich, L., Jr.; Pease, V.L.; Hillhouse, J.W.

    1986-01-01

    Sea otter remains found in deposits of two marine transgressions (Bigbendian and Fishcreekian) of the Alaskan Arctic Coastal Plain which occurred between 2.4 and 3 Ma suggest that during these two events the southern limit of seasonal sea ice was at least 1600 km farther north than at present in Alaskan waters. Perennial sea ice must have been severely restricted or absent, and winters were warmer than at present during these two sea-level highstands. Paleomagnetic, faunal, and palynological data indicate that the later transgression (Fishcreekian) occurred during the early part of the Matuyama Reversed-Polarity Chron. -from Authors

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  2. Large-Scale Surveys of Snow Depth on Arctic Sea Ice from Operation IceBridge

    NASA Technical Reports Server (NTRS)

    Kurtz, Nathan T.; Farrell, Sinead L.

    2011-01-01

    We show the first results of a large ]scale survey of snow depth on Arctic sea ice from NASA fs Operation IceBridge snow radar system for the 2009 season and compare the data to climatological snow depth values established over the 1954.1991 time period. For multiyear ice, the mean radar derived snow depth is 33.1 cm and the corresponding mean climatological snow depth is 33.4 cm. The small mean difference suggests consistency between contemporary estimates of snow depth with the historical climatology for the multiyear ice region of the Arctic. A 16.5 cm mean difference (climatology minus radar) is observed for first year ice areas suggesting that the increasingly seasonal sea ice cover of the Arctic Ocean has led to an overall loss of snow as the region has transitioned away from a dominantly multiyear ice cover.

  3. Sea Ice Prediction Has Easy and Difficult Years

    NASA Technical Reports Server (NTRS)

    Hamilton, Lawrence C.; Bitz, Cecilia M.; Blanchard-Wrigglesworth, Edward; Cutler, Matthew; Kay, Jennifer; Meier, Walter N.; Stroeve, Julienne; Wiggins, Helen

    2014-01-01

    Arctic sea ice follows an annual cycle, reaching its low point in September each year. The extent of sea ice remaining at this low point has been trending downwards for decades as the Arctic warms. Around the long-term downward trend, however, there is significant variation in the minimum extent from one year to the next. Accurate forecasts of yearly conditions would have great value to Arctic residents, shipping companies, and other stakeholders and are the subject of much current research. Since 2008 the Sea Ice Outlook (SIO) (http://www.arcus.org/search-program/seaiceoutlook) organized by the Study of Environmental Arctic Change (SEARCH) (http://www.arcus.org/search-program) has invited predictions of the September Arctic sea ice minimum extent, which are contributed from the Arctic research community. Individual predictions, based on a variety of approaches, are solicited in three cycles each year in early June, July, and August. (SEARCH 2013).

  4. An attempt at multibeam imaging of laboratory sea ice

    NASA Astrophysics Data System (ADS)

    Chayes, D. N.; Schmidt, V. E.

    2015-12-01

    Sea ice was grown in a wave tank at the Hamburgische Schiffbau-Versuchsanstalt GmbH (HSVA) in Hamburg, Germany from December 12-20, 2013 as part of an EU-funded effort to understand the behavior of crude oil under sea ice. As an add-on to that experiment, we borrowed a Teledyne ODOM MB1 multibeam sonar that works in the frequency range from 170 to 220 kHz, mounted it on a moveable trolly, and collected beamformed and time series data with it looking upward at sea ice grown under various conditions.The water depth between the sonar transducer and the bottom of the sea ice was shallower than expected so the sonar was operating in the vicinity of the near field boundary. The experimental setup, data processing methods, and results will be presented in this poster.

  5. Arctic Daily Sea Ice, March 2012 to Feb. 2013

    NASA Video Gallery

    This animation shows the seasonal change in the extent of the Arctic sea ice between March 1, 2012 and February 28, 2013. The annual cycle starts with the maximum extent reached on March 15, 2012. ...

  6. Diurnal Thermal Cycling Effects on Backscatter of Thin Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Gow, A. J.; Perovich, D. K.; Hsu, C. C.; Ding, K. H.; Kong, J. A.; Grenfell, T. C.

    1996-01-01

    To invesigate effects on polarimetric backscatter of sea ice grown under diurnal cycling conditions, we carried out an experiment inJanuary 1994 at the outdoor Geophysical Research Facility in the Cold Regions Research and Engineering Laboratory.

  7. Photophysiology and cellular composition of sea ice algae

    SciTech Connect

    Lizotte, M.P.

    1989-01-01

    The productivity of sea ice algae depends on their physiological capabilities and the environmental conditions within various microhabitats. Pack ice is the dominant form of sea ice, but the photosynthetic activity of associated algae has rarely been studied. Biomass and photosynthetic rates of ice algae of the Weddell-Scotia Sea were investigated during autumn and winter, the period when ice cover grows from its minimum to maximum. Biomass-specific photosynthetic rates typically ranged from 0.3 to 3.0 {mu}g C {center dot} {mu}g chl{sup {minus}1} {center dot} h{sup {minus}1} higher than land-fast ice algae but similar to Antarctic phytoplankton. Primary production in the pack ice during winter may be minor compared to annual phytoplankton production, but could represent a vital seasonal contribution to the Antarctic ecosystem. Nutrient supply may limit the productivity of ice algae. In McMurdo Sound, congelation ice algae appeared to be more nutrient deficient than underlying platelet ice algae based on: lower nitrogen:carbon, chlorophyll:carbon, and protein:carbohydrate; and {sup 14}C-photosynthate distribution to proteins and phospholipids was lower, while distribution to polysaccharides and neutral lipids was higher. Depletion of nitrate led to decreased nitrogen:carbon, chlorophyll:carbon, protein:carbohydrate, and {sup 14}C-photosynthate to proteins. Studied were conducted during the spring bloom; therefore, nutrient limitation may only apply to dense ice algal communities. Growth limiting conditions may be alleviated when algae are released into seawater during the seasonal recession of the ice cover. To continue growth, algae must adapt to the variable light field encountered in a mixed water column. Photoadaptation was studied in surface ice communities and in bottom ice communities.

  8. Sea Ice Characteristics and the Open-Linked Data World

    NASA Astrophysics Data System (ADS)

    Khalsa, S. J. S.; McGuinness, D. L.; Duerr, R.; Pulsifer, P. L.; Fox, P. A.; Thompson, C.; Yan, R.

    2014-12-01

    The audience for sea ice data sets has broadened dramatically over the past several decades. Initially the National Snow and Ice Data Center (NSIDC) sea ice products were used primarily by sea ice specialists. However, now they are in demand by researchers in many different domains and some are used by the public. This growth in the number and type of users has presented challenges to content providers aimed particularly at supporting interdisciplinary and multidisciplinary data use. In our experience, it is generally insufficient to simply make the data available as originally formatted. New audiences typically need data in different forms; forms that meet their needs, that work with their specific tools. Moreover, simple data reformatting is rarely enough. The data needs to be aggregated, transformed or otherwise converted into forms that better serve the needs of the new audience. The Semantic Sea Ice Interoperability Initiative (SSIII) is an NSF-funded research project aimed at making sea ice data more useful to more people using semantic technologies. The team includes domain and science data experts as well as knowledge representation and linked data experts. Beginning with a series of workshops involving members of the operations, sea ice research and modeling communities, as well as members of local communities in Alaska, a suite of ontologies describing the physical characteristics of sea ice have been developed and used to provide one of NSIDC's data sets, the operational Arctic sea ice charts obtained from the Canadian Ice Center, as open-linked data. These data extend nearly a decade into the past and can now be queried either directly through a publicly available SPARQL end point (for those who are familiar with open-linked data) or through a simple Open Geospatial Consortium (OGC) standards map-based query tool. Questions like "What were the characteristics (i.e., sea ice concentration, form and stage of development) of the sea ice in the region

  9. The Satellite Passive-Microwave Record of Sea Ice in the Ross Sea Since Late 1978

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2009-01-01

    Satellites have provided us with a remarkable ability to monitor many aspects of the globe day-in and day-out and sea ice is one of numerous variables that by now have quite substantial satellite records. Passive-microwave data have been particularly valuable in sea ice monitoring, with a record that extends back to August 1987 on daily basis (for most of the period), to November 1970 on a less complete basis (again for most of the period), and to December 1972 on a less complete basis. For the period since November 1970, Ross Sea sea ice imagery is available at spatial resolution of approximately 25 km. This allows good depictions of the seasonal advance and retreat of the ice cover each year, along with its marked interannual variability. The Ross Sea ice extent typically reaches a minimum of approximately 0.7 x 10(exp 6) square kilometers in February, rising to a maximum of approximately 4.0 x 10(exp 6) square kilometers in September, with much variability among years for both those numbers. The Ross Sea images show clearly the day-by-day activity greatly from year to year. Animations of the data help to highlight the dynamic nature of the Ross Sea ice cover. The satellite data also allow calculation of trends in the ice cover over the period of the satellite record. Using linear least-squares fits, the Ross Sea ice extent increased at an average rate of 12,600 plus or minus 1,800 square kilometers per year between November 1978 and December 2007, with every month exhibiting increased ice extent and the rates of increase ranging from a low of 7,500 plus or minus 5,000 square kilometers per year for the February ice extents to a high of 20,300 plus or minus 6,100 kilometers per year for the October ice extents. On a yearly average basis, for 1979-2007 the Ross Sea ice extent increased at a rate of 4.8 plus or minus 1.6 % per decade. Placing the Ross Sea in the context of the Southern Ocean as a whole, over the November 1978-December 2007 period the Ross Sea had

  10. Arctic Sea Ice Motion from Wavelet Analysis of Satellite Data

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Zhao, Yunhe

    1998-01-01

    Wavelet analysis of DMSP SSM/I (Special Sensor Microwave/Imager) 85 GHz and 37 GHz radiance data, SMMR (Scanning Multichannel Microwave Radiometer) 37 GHz, and NSCAT (NASA Scatterometer) 13.9 GHZ data can be used to obtain daily sea ice drift information for both the northern and southern polar regions. The derived maps of sea ice drift provide both improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution over techniques utilizing data from satellite synthetic aperture radars (SAR). Examples of derived ice-drift maps in the Arctic illustrate large-scale circulation reversals within a period of a couple weeks. Comparisons with ice displacements derived from buoys show good quantitative agreement. NASA Scatterometer (NSCAT) 13.9 GHZ data have been also used for wavelet analysis to derive sea-ice drift. First, the 40' incidence-angle, sigma-zero (surface roughness) daily map of whole Arctic region with 25 km of pixel size from satellite's 600 km swath has been constructed. Then, the similar wavelet transform procedure to SSM/I data can be applied. Various scales of wavelet transform and threshold have been tested. By overlaying , neighbor filtering, and block-averaging the results of multiscale wavelet transforms, the final sea ice drift vectors are much smooth and representative to the sea ice motion. This wavelet analysis procedure is robust and can make a major contribution to the understanding of ice motion over large areas at relatively high temporal resolutions. The results of wavelet analysis of SSM/I and NSCAT images and buoy data can be merged by some data fusion techniques and will help to improve our current knowledge of sea ice drift and related processes through the data assimilation of ocean-ice numerical model.

  11. Antarctic Sea ice--a habitat for extremophiles.

    PubMed

    Thomas, D N; Dieckmann, G S

    2002-01-25

    The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice-covered extraterrestrial bodies. PMID:11809961

  12. Antarctic Sea Ice-a Habitat for Extremophiles

    NASA Astrophysics Data System (ADS)

    Thomas, D. N.; Dieckmann, G. S.

    2002-01-01

    The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice-covered extraterrestrial bodies.

  13. Ice gouge processes in the Alaskan Beaufort Sea

    USGS Publications Warehouse

    Rearic, Douglas M.; Ticken, Edward J.

    1988-01-01

    A generalized picture of ice gouge characteristics from shallow inshore depths to the outer shelf at about 60 m of water is presented. Data from recent studies show that the size and quantity of gouging increases in an offshore direction to depths of about 45 m where this trend then reverses and the features decrease in size and quantity as the shelf break is approached. Ice gouges are oriented east-west and this suggests that most gouging is caused by ice approaching from the east, possibly driven by the Beaufort Sea gyre. The most intense gouging occurs in the stamukhi zone, between 20 and 40 m of water, and is caused by a high rate of ice keel production owing to shearing forces between mobile and stable sea ice. Inshore of the stamukhi zone, ice gouging still presents a significant hazard but their greatly decreased size and number make it possible to design against this hazard.

  14. CLIVAR Exchanges No. 62: Sea Level Rise, Ocean/Ice Shelf Interactions and Ice Sheets

    SciTech Connect

    Pirani, Anna; Danabasoglu, Gokhan; Griffies, Stephen; Marsland, Simon

    2013-08-01

    This special issue of CLIVAR Exchanges is devoted to presenting a selection of the science contributed by both speakers and poster presenters at the CLIVAR Workshop on Sea Level Rise, Ocean/Ice Shelf Interactions and Ice Sheets at CSIRO Marine and Atmospheric Research in Hobart, Australia, on 18-20 February 2013. The workshop brought together leading international scientists and early-career researchers from the ocean, ice-sheet, ice-shelf, and sea-level rise modelling and observational communities to explore the state-of-science and emerging pathways for development of the next generation of coupled climate models.

  15. Sensitivity study of a dynamic thermodynamic sea ice model

    SciTech Connect

    Holland, D.M.; Mysak, L.A.; Manak, D.K. )

    1993-02-15

    A numerical simulation of the seasonal sea ice cover in the Arctic Ocean and the Greenland, Iceland, and Norwegian seas is presented. The sea ice model is extracted from Oberhuber's (1990) coupled sea ice-mixed layer-isopycnal general circulation model and is written in spherical coordinates. The advantage of such a model over previous sea ice models is that it can be easily coupled to either global atmospheric or ocean general circulation models written in spherical coordinates. In this model, the thermodynamics are a modification of that of Parkinson and Washington, while the dynamics use the full Hibler viscous-plastic rheology. Monthly thermodynamic and dynamic forcing fields for the atmosphere and ocean are specified. The simulations of the seasonal cycle of ice thickness, compactness, and velocity, for a control set of parameters, compare favorably with the known seasonal characteristics of these fields. A sensitivity study of the control simulation of the seasonal sea ice cover is presented. The sensitivity runs are carried out under three different themes, namely, numerical conditions, parameter values, and physical processes. This last theme refers to experiments in which physical processes are either newly added or completely removed from the model. Approximately 80 sensitivity runs have been performed in which a change from the control run environment has been implemented. Comparisons have been made between the control run and a particular sensitivity run based on time series of the seasonal cycle of the domain-averaged ice thickness, compactness, areal coverage, and kinetic energy. In addition, spatially varying fields of ice thickness, compactness, velocity, and surface temperature for each season are presented for selected experiments. A brief description and discussion of the more interesting experiments are presented. The simulation of the seasonal cycle of Arctic sea ice cover is shown to be robust. 31 refs., 20 figs., 5 tabs.

  16. Sub-Regional Sea Ice Preferences of Pacific Walrus in the Bering Sea Using SAR Data

    NASA Astrophysics Data System (ADS)

    Sacco, A.; Mahoney, A. R.; Eicken, H.; Johnson, M. A.; Ray, C.

    2014-12-01

    The Pacific walrus (O. r. divergens) uses winter sea ice in the Bering Sea for numerous parts of its natural history including courtship, foraging, and migration. Recent and predicted loss of sea ice has caused the Pacific walrus to be considered for an elevated status under the Endangered Species Act. Study of the ice conditions during this period is required to investigate changes in the Bering Sea ice pack and its effects on walrus sustainability. Using Radarsat-1 data and second-order texture statistics, a classification system was devised to separate sea ice into three distinguishable classes based on walrus needs of open water availability in the pack ice: discontinuous pack ice, continuous pack ice, and open water. Classifications are performed on sub-regional image areas to facilitate classification of heterogeneous seascapes which are thought to be distinguishable by walrus. Spatial, as well as temporal, changes in the seascape cover, based on the classification, are achieved. These results are then combined with ship-based observations of walrus to quantify walrus habitat preference. The three-class algorithm has a success rate of 94% for the discontinuous ice and continuous pack ice. Radarsat-1 images from 2004 - 2008 were analyzed for changes in seasonal and annual discontinuous ice extent. After classification, the spatial extent of discontinuous ice was found to vary throughout 2004 - 2008 in the Bering Sea shelf. Walrus are also shown to prefer discontinuous pack far from the southernmost ice edge. Maps of walrus habitat preference and persistent areas of sea ice seascapes are created and then can be used for the walrus' status consideration under the Endangered Species Act in addition to general species management issues.

  17. Divergent movements of walrus and sea ice in the Nothern Bering Sea

    USGS Publications Warehouse

    Jay, Chadwick V.; Udevitz, Mark S.; Kwok, Ron; Fischbach, Anthony S.; Douglas, David C.

    2010-01-01

    The Pacific walrus Odobenus rosmarus divergens is a large Arctic pinniped of the Chukchi and Bering Seas. Reductions of sea ice projected to occur in the Arctic by mid-century raise concerns for conservation of the Pacific walrus. To understand the significance of sea ice loss to the viability of walruses, it would be useful to better understand the spatial associations between the movements of sea ice and walruses. We investigated whether local-scale (~1 to 100 km) walrus movements correspond to movements of sea ice in the Bering Sea in early spring, using locations from radio-tracked walruses and measures of ice floe movements from processed synthetic aperture radar satellite imagery. We used generalized linear mixed-effects models to analyze the angle between walrus and ice floe movement vectors and the distance between the final geographic position of walruses and their associated ice floes (displacement), as functions of observation duration, proportion of time the walrus was in water, and geographic region. Analyses were based on 121 walrus-ice vector pairs and observations lasting 12 to 36 h. Angles and displacements increased with observation duration, proportion of time the walrus spent in the water, and varied among regions (regional mean angles ranged from 40° to 81° and mean displacements ranged from 15 to 35 km). Our results indicated a lack of correspondence between walruses and their initially associated ice floes, suggesting that local areas of walrus activities were independent of the movement of ice floes.

  18. Estimation of Sea Ice Thickness through Maximum Covariance Analysis

    NASA Astrophysics Data System (ADS)

    Dirkson, A.; Monahan, A. H.; Merryfield, W. J.

    2014-12-01

    Arctic sea ice is an important constituent of the global climate system and has undergone significant changes in recent years. Both a decrease in sea ice extent, especially over the summer months, as well as an overall thinning of the ice pack have been observed. Superimposed on the decreasing trend is considerable interannual variability which has proven difficult to predict, particularly when the variability deviates far from the trend. One of the challenges for model based seasonal predictions of sea ice is an accurate representation of sea ice initial conditions, particularly the distribution of sea ice thickness (SIT), for which the observational record is sparse. As a possible means of filling this gap and establishing an improved method for initializing SIT in the Canadian Seasonal to Interannual Prediction System (CanSIPS), this research aims to investigate how accurately SIT can be estimated in real time using better observed and physically relevant predictors. In this study sea ice concentration (SIC), sea level pressure (SLP), and combined SIC/SLP are used to construct a predictor-predictand model using maximum covariance analysis (MCA). The model parameters are determined over a period of 15 years prior to the initialization year, and an estimation of the SIT field is made by applying this statistical model to the anomalies of the predictor for the year of interest. Sea ice data from the Polar Science Center PIOMAS product are used to construct and test the model, and estimations of SIT over the period 1995-2012 are examined. Monte Carlo experiments are performed to test the statistical significance of the SIT prediction as a function of the predictors and how many statistical modes are retained.

  19. Radionuclides in Arctic sea ice: Tracers of sources, fates and ice transit time scales

    NASA Astrophysics Data System (ADS)

    Masqué, P.; Cochran, J. K.; Hirschberg, D. J.; Dethleff, D.; Hebbeln, D.; Winkler, A.; Pfirman, S.

    2007-08-01

    Arctic sea ice can incorporate sediment and associated chemical species during its formation in shallow shelf environments and can also intercept atmospherically transported material during transit. Release of this material in ice ablation areas (e.g. the Fram Strait) enhances fluxes of both sediments and associated species in such areas. We have used a suite of natural ( 7Be, 210Pb) and anthropogenic ( 137Cs, 239Pu, 240Pu) radionuclides in sea ice, sea-ice sediments (SIS), sediment trap material and bottom sediments from the Fram Strait to estimate transit times of sea ice from source to ablation areas, calculate radionuclide fluxes to the Fram Strait and investigate the role of sea-ice entrained sediments in sedimentation processes. Sea ice intercepts and transports the atmospherically supplied radionuclides 7Be and 210Pb, which are carried in the ice and are scavenged by any entrained SIS. All of the 7Be and most of the excess 210Pb measured in SIS collected in the Fram Strait are added to the ice during transit through the Arctic Ocean, and we use these radionuclides as chronometers to calculate ice transit times for individual ice floes. Transit times estimated from the 210Pb inventories in two ice cores are 1-3 years. Values estimated from the 7Be/ 210Pb excess activity ratio of SIS are about 3-5 years. Finally, equilibrium values of the activity ratio of 210Pb to its granddaughter 210Po in the ice cores indicate transit times of at least 2 years. These transit times are consistent with back-trajectory analyses of the ice floes. The latter, as well as the clay-mineral assemblage of the SIS (low smectite and high illite content), suggest that the sampled sea-ice floes originated from the eastern Siberian Arctic shelf seas such as the eastern Laptev Sea and the East Siberian Sea. This result is in agreement with the relatively low activities of 239,240Pu and 137Cs and the 240Pu/ 239Pu atom ratios (˜0.18, equivalent to that in global fallout) in SIS, indicating

  20. Sea-Ice Feature Mapping using JERS-1 Imagery

    NASA Technical Reports Server (NTRS)

    Maslanik, James; Heinrichs, John

    1994-01-01

    JERS-1 SAR and OPS imagery are examined in combination with other data sets to investigate the utility of the JERS-1 sensors for mapping fine-scale sea ice conditions. Combining ERS-1 C band and JERS-1 L band SAR aids in discriminating multiyear and first-year ice. Analysis of OPS imagery for a field site in the Canadian Archipelago highlights the advantages of OPS's high spatial and spectral resolution for mapping ice structure, melt pond distribution, and surface albedo.

  1. Full-depth desalination of warm sea ice

    NASA Astrophysics Data System (ADS)

    Jardon, F. P.; Vivier, F.; Vancoppenolle, M.; LourençO, A.; Bouruet-Aubertot, P.; Cuypers, Y.

    2013-01-01

    Abstract The large-scale Arctic <span class="hlt">sea-ice</span> retreat induces a gradual replacement of thick, multi-year <span class="hlt">sea</span> <span class="hlt">ice</span> by thinner first-year <span class="hlt">ice</span>. The latter has distinctive physical properties and is in particular substantially saltier. It is generally thought that while salt rejection occurs primarily during <span class="hlt">ice</span> formation in winter, most of the remaining brine is flushed out of the <span class="hlt">ice</span> by the percolating surface melt water in summer. Here, it is argued that a substantial part of this residual desalination of first-year <span class="hlt">sea</span> <span class="hlt">ice</span> can occur well before summer melt, due to brine convection over the full thickness of the <span class="hlt">ice</span>, once the <span class="hlt">ice</span> temperature is higher than a threshold that depends on bulk salinity and thickness. This critical temperature is substantially higher than the permeability threshold. The argument stems from a theoretical analysis of the porous Rayleigh number depicting the propensity for convection in the mushy-layer theory. It is supported by simulations performed with a state-of-the-art 1-D <span class="hlt">sea-ice</span> model. The study was initially motivated by observations collected in March 2007 in Storfjorden, Svalbard. Those are indirect, however, and are thus presented here as a possible example. Two sporadic anomalies of seawater salinity were recorded close to the base of 40 cm thick <span class="hlt">ice</span> in temperature conditions that are incompatible with <span class="hlt">ice</span> formation. Analyses and simulations forced with observed atmospheric conditions suggest that the second peak is caused by flushing of meltwater, while the first and most intense peak is likely associated with an episode of brine convection over the full depth of the <span class="hlt">ice</span>, yielding significant desalination.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990078517&hterms=bootstrap&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbootstrap','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990078517&hterms=bootstrap&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbootstrap"><span id="translatedtitle">A Modified NASA Team <span class="hlt">Sea</span> <span class="hlt">Ice</span> Algorithm for the Antarctic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, Donald J.; Markus, Thorsten</p> <p>1998-01-01</p> <p>A recent comparative study of the NASA Team and Bootstrap passive microwave <span class="hlt">sea</span> <span class="hlt">ice</span> algorithms revealed significantly different <span class="hlt">sea</span> <span class="hlt">ice</span> concentration retrievals in some parts of the Antarctic. The study identified potential reasons for the discrepancies including the influence of <span class="hlt">sea</span> <span class="hlt">ice</span> temperature variability on the Bootstrap retrievals and the influence of <span class="hlt">ice</span> surface reflectivity on the horizontally polarized emissivity in the NASA Team retrievals. In this study, we present a modified version of the NASA Team algorithm which reduces the error associated with the use of horizontally polarized radiance data, while retaining the relative insensitivity to <span class="hlt">ice</span> temperature variations provided by radiance ratios. By retaining the 19 GHz polarization as an independent variable, we also maintain a relatively large dynamic range in <span class="hlt">sea</span> <span class="hlt">ice</span> concentration. The modified algorithm utilizes the 19 GHz polarization (PR19) and both gradient ratios, GRV and GRH defined by (37V-19V)/(37V+19V) and (37H-19H)/(37H+19H), respectively, rather than just GRV used in the current NASA Team algorithm. A plot of GRV versus GRH shows that the preponderance of points lie along a quadratic curve, whereas those points affected by surface reflectivity anomalies deviate from this curve. This serves as a method of identifying the problems points. The 19H brightness temperature of these problem points is increased so they too fall along quadratic curve. <span class="hlt">Sea</span> <span class="hlt">ice</span> concentrations derived from AVHRR imagery illustrate the extent to which this method reduces the error associated with surface layering.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.5910D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.5910D"><span id="translatedtitle">Skill metrics for evaluation and comparison of <span class="hlt">sea</span> <span class="hlt">ice</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dukhovskoy, Dmitry S.; Ubnoske, Jonathan; Blanchard-Wrigglesworth, Edward; Hiester, Hannah R.; Proshutinsky, Andrey</p> <p>2015-09-01</p> <p>Five quantitative methodologies (metrics) that may be used to assess the skill of <span class="hlt">sea</span> <span class="hlt">ice</span> models against a control field are analyzed. The methodologies are Absolute Deviation, Root-Mean-Square Deviation, Mean Displacement, Hausdorff Distance, and Modified Hausdorff Distance. The methodologies are employed to quantify similarity between spatial distribution of the simulated and control scalar fields providing measures of model performance. To analyze their response to dissimilarities in two-dimensional fields (contours), the metrics undergo sensitivity tests (scale, rotation, translation, and noise). Furthermore, in order to assess their ability to quantify resemblance of three-dimensional fields, the metrics are subjected to sensitivity tests where tested fields have continuous random spatial patterns inside the contours. The Modified Hausdorff Distance approach demonstrates the best response to tested differences, with the other methods limited by weak responses to scale and translation. Both Hausdorff Distance and Modified Hausdorff Distance metrics are robust to noise, as opposed to the other methods. The metrics are then employed in realistic cases that validate <span class="hlt">sea</span> <span class="hlt">ice</span> concentration fields from numerical models and <span class="hlt">sea</span> <span class="hlt">ice</span> mean outlook against control data and observations. The Modified Hausdorff Distance method again exhibits high skill in quantifying similarity between both two-dimensional (<span class="hlt">ice</span> contour) and three-dimensional (<span class="hlt">ice</span> concentration) <span class="hlt">sea</span> <span class="hlt">ice</span> fields. The study demonstrates that the Modified Hausdorff Distance is a mathematically tractable and efficient method for model skill assessment and comparison providing effective and objective evaluation of both two-dimensional and three-dimensional <span class="hlt">sea</span> <span class="hlt">ice</span> characteristics across data sets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811086D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811086D"><span id="translatedtitle">Atmospheric forcing of <span class="hlt">sea</span> <span class="hlt">ice</span> anomalies in the Ross <span class="hlt">Sea</span> Polynya region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dale, Ethan; McDonald, Adrian; Rack, Wolfgang</p> <p>2016-04-01</p> <p>Despite warming trends in global temperatures, <span class="hlt">sea</span> <span class="hlt">ice</span> extent in the southern hemisphere has shown an increasing trend over recent decades. Wind-driven <span class="hlt">sea</span> <span class="hlt">ice</span> export from coastal polynyas is an important source of <span class="hlt">sea</span> <span class="hlt">ice</span> production. Areas of major polynyas in the Ross <span class="hlt">Sea</span>, the region with largest increase in <span class="hlt">sea</span> <span class="hlt">ice</span> extent, have been suggested to produce the vast amount of the <span class="hlt">sea</span> <span class="hlt">ice</span> in the region. We investigate the impacts of strong wind events on polynyas and the subsequent <span class="hlt">sea</span> <span class="hlt">ice</span> production. We utilize Bootstrap <span class="hlt">sea</span> <span class="hlt">ice</span> concentration (SIC) measurements derived from satellite based, Special Sensor Microwave Imager (SSM/I) brightness temperature images. These are compared with surface wind measurements made by automatic weather stations of the University of Wisconsin-Madison Antarctic Meteorology Program. Our analysis focusses on the winter period defined as 1st April to 1st November in this study. Wind data was used to classify each day into characteristic regimes based on the change of wind speed. For each regime, a composite of SIC anomaly was formed for the Ross <span class="hlt">Sea</span> region. We found that persistent weak winds near the edge of the Ross <span class="hlt">Ice</span> Shelf are generally associated with positive SIC anomalies in the Ross <span class="hlt">Sea</span> polynya area (RSP). Conversely we found negative SIC anomalies in this area during persistent strong winds. By analyzing <span class="hlt">sea</span> <span class="hlt">ice</span> motion vectors derived from SSM/I brightness temperatures, we find significant <span class="hlt">sea</span> <span class="hlt">ice</span> motion anomalies throughout the Ross <span class="hlt">Sea</span> during strong wind events. These anomalies persist for several days after the strong wing event. Strong, negative correlations are found between SIC within the RSP and wind speed indicating that strong winds cause significant advection of <span class="hlt">sea</span> <span class="hlt">ice</span> in the RSP. This rapid decrease in SIC is followed by a more gradual recovery in SIC. This increase occurs on a time scale greater than the average persistence of strong wind events and the resulting <span class="hlt">Sea</span> <span class="hlt">ice</span> motion anomalies, highlighting the production</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PolSc...2...41H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PolSc...2...41H"><span id="translatedtitle">Vertical material flux under seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> in the Okhotsk <span class="hlt">Sea</span> north of Hokkaido, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiwatari, Takehiko; Shirasawa, Kunio; Fukamachi, Yasushi; Nagata, Ryuichi; Koizumi, Tomoyoshi; Koshikawa, Hiroshi; Kohata, Kunio</p> <p></p> <p>Downward material fluxes under seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> were measured using a time-series sediment trap installed at an offshore site in the Okhotsk <span class="hlt">Sea</span> north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m -2 day -1) and organic matter (mainly detritus; 333 mg m -2 day -1) were recorded during the period in which <span class="hlt">sea</span> <span class="hlt">ice</span> drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81-93 mg m -2 day -1) and opal as biosilica (51-67 mg m -2 day -1), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full <span class="hlt">sea</span> <span class="hlt">ice</span> coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on <span class="hlt">ice</span> algae during the period of full <span class="hlt">sea</span> <span class="hlt">ice</span> coverage. During the period of retreating <span class="hlt">sea</span> <span class="hlt">ice</span>, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10 6 cells m -2 day -1), reflecting their release into the water column as the <span class="hlt">sea</span> <span class="hlt">ice</span> melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of <span class="hlt">sea</span> <span class="hlt">ice</span> in mid-winter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950045752&hterms=Parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DParkinson','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950045752&hterms=Parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DParkinson"><span id="translatedtitle">The role of <span class="hlt">sea</span> <span class="hlt">ice</span> in 2 x CO2 climate model sensitivity. Part 1: The total influence of <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and extent</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rind, D.; Healy, R.; Parkinson, C.; Martinson, D.</p> <p>1995-01-01</p> <p>As a first step in investigating the effects of <span class="hlt">sea</span> <span class="hlt">ice</span> changes on the climate sensitivity to doubled atmospheric CO2, the authors use a standard simple <span class="hlt">sea</span> <span class="hlt">ice</span> model while varying the <span class="hlt">sea</span> <span class="hlt">ice</span> distributions and thicknesses in the control run. Thinner <span class="hlt">ice</span> amplifies the atmospheric temperature senstivity in these experiments by about 15% (to a warming of 4.8 C), because it is easier for the thinner <span class="hlt">ice</span> to be removed as the climate warms. Thus, its impact on sensitivity is similar to that of greater <span class="hlt">sea</span> <span class="hlt">ice</span> extent in the control run, which provides more opportunity for <span class="hlt">sea</span> <span class="hlt">ice</span> reduction. An experiment with <span class="hlt">sea</span> <span class="hlt">ice</span> not allowed to change between the control and doubled CO2 simulations illustrates that the total effect of <span class="hlt">sea</span> <span class="hlt">ice</span> on surface air temperature changes, including cloud cover and water vapor feedbacks that arise in response to <span class="hlt">sea</span> <span class="hlt">ice</span> variations, amounts to 37% of the temperature sensitivity to the CO2 doubling, accounting for 1.56 C of the 4.17 C global warming. This is about four times larger than the <span class="hlt">sea</span> <span class="hlt">ice</span> impact when no feedbacks are allowed. The different experiments produce a range of results for southern high latitudes with the hydrologic budget over Antarctica implying <span class="hlt">sea</span> level increases of varying magnitude or no change. These results highlight the importance of properly constraining the <span class="hlt">sea</span> <span class="hlt">ice</span> response to climate perturbations, necessitating the use of more realistic <span class="hlt">sea</span> <span class="hlt">ice</span> and ocean models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A53C0388S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A53C0388S"><span id="translatedtitle">Accuracy of short term <span class="hlt">Sea</span> <span class="hlt">Ice</span> Drift Forecasts using a coupled <span class="hlt">Ice</span>-Ocean Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schweiger, A. J. B.; Zhang, J.</p> <p>2015-12-01</p> <p><span class="hlt">Sea</span> <span class="hlt">ice</span> drift forecasts for the Arctic for the summer of 2014 are investigated. <span class="hlt">Sea</span> <span class="hlt">ice</span> forecasts are generated for 6 hours to 9 days using the Marginal <span class="hlt">Ice</span> Zone Modelling and Assimilation System (MIZMAS) and 6 hourly forecasts of atmospheric forcing variables from the NOAA Climate Forecast System (CFSv2). Forecast <span class="hlt">sea</span> <span class="hlt">ice</span> drift speed is compared to observations from drifting buoys and other observation platforms. Forecast buoy positions are compared with observed positions at 24 hours to 9 days from the initial forecast. Forecast skill is assessed relative to forecasts made using an <span class="hlt">ice</span> velocity climatology generated from multi-year integrations of the same model. RMS errors for <span class="hlt">ice</span> speed are found in the order of 5 km/day for 24 h to 48 h using the <span class="hlt">sea</span> <span class="hlt">ice</span> model vs. 12 km/day using climatology. Following adjustments in the <span class="hlt">sea</span> <span class="hlt">ice</span> model to remove systematic biases in direction and speed, predicted buoy position RMS errors are improved from 8 km 6.5 km for 24 hour forecasts and 15 km after 72 hours. Using the forecast model increases the probability of tracking a target drifting in <span class="hlt">sea</span> <span class="hlt">ice</span> with a 10x10 km sized image to 95% vs. 50% using climatology. The results are generated in the context of planning and scheduling the acquisition of high resolution images which need to follow buoys or research platforms for scientific research but additional applications such as navigation in the Arctic waters may benefit from this accuracy assessment. Ideas for future improvement of short term <span class="hlt">sea</span> <span class="hlt">ice</span> forecasts and relevance for longer term predictions are explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C43D..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C43D..01R"><span id="translatedtitle">NASA <span class="hlt">Ice</span>Bridge: Scientific Insights from Airborne Surveys of the Polar <span class="hlt">Sea</span> <span class="hlt">Ice</span> Covers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richter-Menge, J.; Farrell, S. L.</p> <p>2015-12-01</p> <p>The NASA Operation <span class="hlt">Ice</span>Bridge (OIB) airborne <span class="hlt">sea</span> <span class="hlt">ice</span> surveys are designed to continue a valuable series of <span class="hlt">sea</span> <span class="hlt">ice</span> thickness measurements by bridging the gap between NASA's <span class="hlt">Ice</span>, Cloud and Land Elevation Satellite (ICESat), which operated from 2003 to 2009, and ICESat-2, which is scheduled for launch in 2017. Initiated in 2009, OIB has conducted campaigns over the western Arctic Ocean (March/April) and Southern Oceans (October/November) on an annual basis when the thickness of <span class="hlt">sea</span> <span class="hlt">ice</span> cover is nearing its maximum. More recently, a series of Arctic surveys have also collected observations in the late summer, at the end of the melt season. The Airborne Topographic Mapper (ATM) laser altimeter is one of OIB's primary sensors, in combination with the Digital Mapping System digital camera, a Ku-band radar altimeter, a frequency-modulated continuous-wave (FMCW) snow radar, and a KT-19 infrared radiation pyrometer. Data from the campaigns are available to the research community at: http://nsidc.org/data/icebridge/. This presentation will summarize the spatial and temporal extent of the OIB campaigns and their complementary role in linking in situ and satellite measurements, advancing observations of <span class="hlt">sea</span> <span class="hlt">ice</span> processes across all length scales. Key scientific insights gained on the state of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover will be highlighted, including snow depth, <span class="hlt">ice</span> thickness, surface roughness and morphology, and melt pond evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A"><span id="translatedtitle">Interactions Between <span class="hlt">Ice</span> Thickness, Bottom <span class="hlt">Ice</span> Algae, and Transmitted Spectral Irradiance in the Chukchi <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arntsen, A. E.; Perovich, D. K.; Polashenski, C.; Stwertka, C.</p> <p>2015-12-01</p> <p>The amount of light that penetrates the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover impacts <span class="hlt">sea-ice</span> mass balance as well as ecological processes in the upper ocean. The seasonally evolving macro and micro spatial variability of transmitted spectral irradiance observed in the Chukchi <span class="hlt">Sea</span> from May 18 to June 17, 2014 can be primarily attributed to variations in snow depth, <span class="hlt">ice</span> thickness, and bottom <span class="hlt">ice</span> algae concentrations. This study characterizes the interactions among these dominant variables using observed optical properties at each sampling site. We employ a normalized difference index to compute estimates of Chlorophyll a concentrations and analyze the increased attenuation of incident irradiance due to absorption by biomass. On a kilometer spatial scale, the presence of bottom <span class="hlt">ice</span> algae reduced the maximum transmitted irradiance by about 1.5 orders of magnitude when comparing floes of similar snow and <span class="hlt">ice</span> thicknesses. On a meter spatial scale, the combined effects of disparities in the depth and distribution of the overlying snow cover along with algae concentrations caused maximum transmittances to vary between 0.0577 and 0.282 at a single site. Temporal variability was also observed as the average integrated transmitted photosynthetically active radiation increased by one order of magnitude to 3.4% for the last eight measurement days compared to the first nine. Results provide insight on how interrelated physical and ecological parameters of <span class="hlt">sea</span> <span class="hlt">ice</span> in varying time and space may impact new trends in Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> extent and the progression of melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/237970','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/237970"><span id="translatedtitle">Observations of <span class="hlt">sea</span> <span class="hlt">ice</span> and icebergs in the western Barents <span class="hlt">Sea</span> during the winter of 1987</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Loeset, S.; Carstens, T.</p> <p>1995-12-31</p> <p>A multisensor <span class="hlt">ice</span> data acquisition program for the western Barents <span class="hlt">Sea</span> 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 <span class="hlt">ice</span> in the area at that time. The reasoning was that prior to any oil/gas exploration and production in the Barents <span class="hlt">Sea</span>, 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 1987 data on <span class="hlt">sea</span> <span class="hlt">ice</span> and icebergs for engineering purposes for the western Barents <span class="hlt">Sea</span> were meager. The present paper highlights some of the findings with emphasis on <span class="hlt">ice</span> edge speeds, <span class="hlt">ice</span> edge displacement and <span class="hlt">ice</span> drift. For icebergs, the paper focuses on population, size distributions and geometric parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013EGUGA..15.5747D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013EGUGA..15.5747D&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">ICE</span> stereocamera system - photogrammetric setup for retrieval and analysis of small scale <span class="hlt">sea</span> <span class="hlt">ice</span> topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Divine, Dmitry; Pedersen, Christina; Karlsen, Tor Ivan; Aas, Harald; Granskog, Mats; Renner, Angelika; Spreen, Gunnar; Gerland, Sebastian</p> <p>2013-04-01</p> <p>A new thin-<span class="hlt">ice</span> Arctic paradigm requires reconsideration of the set of parameterizations of mass and energy exchange within the ocean-<span class="hlt">sea-ice</span>-atmosphere system used in modern CGCMs. Such a reassessment would require a comprehensive collection of measurements made specifically on first-year pack <span class="hlt">ice</span> with a focus on summer melt season when the difference from typical conditions for the earlier multi-year Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover becomes most pronounced. Previous in situ studies have demonstrated a crucial importance of smaller (i.e. less than 10 m) scale surface topography features for the seasonal evolution of pack <span class="hlt">ice</span>. During 2011-2012 NPI developed a helicopter borne <span class="hlt">ICE</span> stereocamera system intended for mapping the <span class="hlt">sea</span> <span class="hlt">ice</span> surface topography and aerial photography. The hardware component of the system comprises two Canon 5D Mark II cameras, combined GPS/INS unit by "Novatel" and a laser altimeter mounted in a single enclosure outside the helicopter. The unit is controlled by a PXI chassis mounted inside the helicopter cabin. The <span class="hlt">ICE</span> stereocamera system was deployed for the first time during the 2012 summer field season. The hardware setup has proven to be highly reliable and was used in about 30 helicopter flights over Arctic <span class="hlt">sea-ice</span> during July-September. Being highly automated it required a minimal human supervision during in-flight operation. The deployment of the camera system was mostly done in combination with the EM-bird, which measures <span class="hlt">sea-ice</span> thickness, and this combination provides an integrated view of <span class="hlt">sea</span> <span class="hlt">ice</span> cover along the flight track. During the flight the cameras shot sequentially with a time interval of 1 second each to ensure sufficient overlap between subsequent images. Some 35000 images of <span class="hlt">sea</span> <span class="hlt">ice</span>/water surface captured per camera sums into 6 Tb of data collected during its first field season. The reconstruction of the digital elevation model of <span class="hlt">sea</span> <span class="hlt">ice</span> surface will be done using SOCET SET commercial software. Refraction at water/air interface can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1815351H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1815351H&link_type=ABSTRACT"><span id="translatedtitle">Recent trends in <span class="hlt">Sea</span> <span class="hlt">ice</span> in the southern and western Baltic and the North <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holfort, Jürgen; Schmelzer, Natalija; Schwegmann, Sandra</p> <p>2016-04-01</p> <p>We analyzed <span class="hlt">sea</span> <span class="hlt">ice</span> charts and observations of a 50 year long period starting in 1961 to produce two climatological <span class="hlt">ice</span> atlases, one for the western and southern Baltic and one for the German Bight and Limfjord. As the year to year variability is large we subdivided the 50 year into three overlapping 30 year periods (1961-1990, 1971-2000 and 1981-2010) to look for trends in the <span class="hlt">sea</span> <span class="hlt">ice</span>. In the southern and western Baltic as well as in the North <span class="hlt">Sea</span> there was a clear decrease in the total frequency of <span class="hlt">ice</span> occurrence. Other parameters like begin and end of the <span class="hlt">ice</span> season, <span class="hlt">ice</span> thickness, etc. did not show such clear signal and also showed larger regional differences. The <span class="hlt">ice</span> conditions mainly changed in accordance with the changes in air temperature in the same period, although some more regional changes in some parameters were most probably also influenced by other factors like the deepening of fairways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C44A..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C44A..06M"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> deformation and the <span class="hlt">ice</span> thickness distribution: How novel observations can help to improve models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, T.</p> <p>2012-12-01</p> <p>Several decades of Arctic-wide observational records of <span class="hlt">sea</span> <span class="hlt">ice</span> concentration and drift offer great opportunities to validate the <span class="hlt">sea</span> <span class="hlt">ice</span> component of global climate models (GCMs). Recent advancements in air- and space-borne <span class="hlt">ice</span> thickness retrieval add the long missed "3rd dimension" to these observations. However, in order to understand why a model diverges from observations, why the model physics may be inadequate and how to improve these, often observations with great detail rather than great coverage are desired. From a modeler's perspective an ideal set of observations offers the opportunity to build parameterizations directly upon prognostic model variables, such as <span class="hlt">sea</span> <span class="hlt">ice</span> concentration, thickness and drift. However, the dependency on prognostic variables is not a guaranty yet that a parameterization is flexible enough to cope with the rapid changes currently observed in the Arctic. In particular in <span class="hlt">sea</span> <span class="hlt">ice</span> modeling there is a need to revisit parameters and parameterizations dating back to the 1970s to make sure they are still valid. Examples relating to <span class="hlt">sea</span> <span class="hlt">ice</span> mechanics are drag coefficients, <span class="hlt">sea</span> <span class="hlt">ice</span> strength, and deformation. The latter importantly shapes the <span class="hlt">ice</span> thickness distribution (ITD) by ridging thin into thick <span class="hlt">ice</span> thereby compacting the <span class="hlt">ice</span> cover, which opens up leads. Leads in the pack <span class="hlt">ice</span> act like windows in a solid wall: they enable a direct, enhanced exchange between ocean and atmosphere. Most <span class="hlt">sea</span> <span class="hlt">ice</span> models used in GCMs consider an ITD for the computation of the conductive heat flux only in an idealized statistical manner. Currently, few models consider the effect of <span class="hlt">sea</span> <span class="hlt">ice</span> mechanics on the ITD, i.e. advection and deformation. The ITD has lately gained greater attention because advances in both models and observations enable higher spatial resolution furthering the perception that changes in Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> characteristics go along with changing <span class="hlt">ice</span> types. In this presentation simulations with a GCM are used to demonstrate the impact of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41.3510S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41.3510S"><span id="translatedtitle">Twentieth century <span class="hlt">sea-ice</span> trends in the Ross <span class="hlt">Sea</span> from a high-resolution, coastal <span class="hlt">ice</span>-core record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinclair, Kate E.; Bertler, Nancy A. N.; Bowen, Melissa M.; Arrigo, Kevin R.</p> <p>2014-05-01</p> <p>We present the first proxy record of <span class="hlt">sea-ice</span> area (SIA) in the Ross <span class="hlt">Sea</span>, Antarctica, from a 130 year coastal <span class="hlt">ice</span>-core record. High-resolution deuterium excess data show prevailing stable SIA from the 1880s until the 1950s, a 2-5% reduction from the mid-1950s to the early-1990s, and a 5% increase after 1993. Additional support for this reconstruction is derived from <span class="hlt">ice</span>-core methanesulphonic acid concentrations and whaling records. While SIA has continued to decline around much of the West Antarctic coastline since the 1950s, concurrent with increasing air and ocean temperatures, the underlying trend is masked in the Ross <span class="hlt">Sea</span> by a switch to positive SIA anomalies since the early-1990s. This increase is associated with a strengthening of southerly winds and the enhanced northward advection of <span class="hlt">sea</span> <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010015247&hterms=Wavelet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DWavelet','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010015247&hterms=Wavelet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DWavelet"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">Ice</span> Motion from Wavelet Analysis of Satellite Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, Antony K.; Zhou, Yun-He; Zukor, Dorothy (Technical Monitor)</p> <p>2000-01-01</p> <p>Wavelet analysis of NASA scatterometer (NSCAT) backscatter and Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) radiance data can be used to obtain daily <span class="hlt">sea</span> <span class="hlt">ice</span> drift information for the Arctic region. This technique provides improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution over techniques utilizing data from satellite synthetic aperture radars. Comparisons with <span class="hlt">ice</span> motion derived from ocean buoys give good quantitative agreement. Both comparison results from NSCAT and SSM/I are compatible, and the results from NSCAT can definitely complement that from SSM/I when there are cloud or surface effects. Then three <span class="hlt">sea-ice</span> drift daily results from NSCAT, SSM/I, and buoy data can be merged as a composite map by some data fusion techniques. The <span class="hlt">ice</span> flow streamlines are highly correlated with surface air pressure contours. Examples of derived <span class="hlt">ice</span>-drift maps in December 1996 illustrate large-scale circulation reversals over a period of four days. A method for deriving divergence and shear at the large-scale has been developed and comparison between buoys and satellite results shows a good agreement. These calibrated/validated results indicate that NSCAT, SSM/I merged daily <span class="hlt">ice</span> motion are suitably accurate to identify and closely locate <span class="hlt">sea</span> <span class="hlt">ice</span> processes, and to improve our current knowledge of <span class="hlt">sea</span> <span class="hlt">ice</span> drift and related processes through the data assimilation of ocean-<span class="hlt">ice</span> numerical model. For demonstration purpose, the <span class="hlt">ice</span> velocities derived from satellite data are compared with the <span class="hlt">ice</span> velocities derived from a coupled <span class="hlt">ice</span>-ocean interaction model. The comparison reveals that the general circulation patterns of the two are quite similar but the <span class="hlt">ice</span> velocity differences between the two are quite significant. In order to quantify the wind effects on <span class="hlt">ice</span> motion, empirical orthogonal functions (EOF) are used in the principal component analysis for both <span class="hlt">ice</span> motion and pressure field. Some</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000052707&hterms=ocean+images&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Docean%2Bimages','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000052707&hterms=ocean+images&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Docean%2Bimages"><span id="translatedtitle">Satellite-Derived Dynamics of Southern Ocean <span class="hlt">Sea</span> <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Drinkwater, Mark R.; Liu, Xiang</p> <p>2000-01-01</p> <p>Antarctic ERS-2, RADARSAT Synthetic Aperture Radar and ERS-1/2 Scatterometer images were analyzed with SMMI radiometer image time-series data to investigate seasonal variability in satellite-tracked <span class="hlt">sea-ice</span> dynamics in the Southern Ocean during 1992. Supporting field data were acquired during 'in-situ' experiments including the winter 1992 <span class="hlt">Ice</span> Station Weddell and Winter Weddell Gyre studies. A variety of surface measurements were made during these experiments including Argos-buoy deployment and GPS drift measurements. These are used in conjunction with International Program for Antarctic Buoys drift trajectories for <span class="hlt">ice</span>-motion tracking validation. Comparisons between gridded Special Sensor Microwave Imager (SSMI) <span class="hlt">ice</span>-motion vectors and European Center for Medium Range Weather Forecasts/National Centers for Environmental Prediction (ECMWF/NCEP) analyses indicate that large-scale drift is forced predominantly by the long-term mean, large-scale synoptic pressure field. Only sub-daily SAR <span class="hlt">sea-ice</span> tracking can capture high-frequency fluctuations, driven by polar lows or tidal forcing. In these cases, <span class="hlt">sea-ice</span> drift can respond rapidly to changes in forcing on semi-diurnal time scales depending on the location with respect to the coastline. Seasonality of <span class="hlt">ice</span> drift, particularly in the Weddell and Ross <span class="hlt">Seas</span>, is linked to <span class="hlt">ice</span> extent and compactness, and internal <span class="hlt">ice</span> stresses transmitted through the pack <span class="hlt">ice</span> from the coast. Three-monthly seasonal climatologies are presented of austral winter of <span class="hlt">ice</span> drift in the Southern Ocean. The large Weddell and Ross <span class="hlt">Sea</span> gyres are clearly resolved along with key seasonal and spatial attributes of their cyclonic circulation. Regional time series of <span class="hlt">ice</span> dynamics parameters are used to illustrate correlations with meteorological forcing. Persistent divergence such as that occurring in the Ronne-Filchner polynya system results in large fractions of new <span class="hlt">ice</span>. Similarly, convergence zones produce large fractions of deformed <span class="hlt">ice</span> and characterize</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PolSc...8..385Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PolSc...8..385Y&link_type=ABSTRACT"><span id="translatedtitle">Photosynthetic characteristics of sinking microalgae under the <span class="hlt">sea</span> <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, Shinya; Michel, Christine; Gosselin, Michel; Demers, Serge; Fukuchi, Mitsuo; Taguchi, Satoru</p> <p>2014-12-01</p> <p>The photosynthetic characteristics of sinking a microalgal community were studied to compare with the <span class="hlt">ice</span> algal community in the <span class="hlt">sea</span> <span class="hlt">ice</span> and the phytoplankton community in the water column under the <span class="hlt">sea</span> <span class="hlt">ice</span> at the beginning of the light season in the first-year <span class="hlt">sea</span> <span class="hlt">ice</span> ecosystem on the Mackenzie Shelf, in the western Canadian Arctic. The phytoplankton community was collected using a water bottle, whereas the sinking algal community was collected using particle collectors, and the <span class="hlt">ice</span> algal community was obtained by using an <span class="hlt">ice</span>-core sampler from the bottom portion of <span class="hlt">ice</span> core. Photosynthesis versus irradiance (P-E) incubation experiments were conducted on deck to obtain the initial slope (αB) and the maximum photosynthetic rate (PmB) of the three algal communities. The αB and the PmB of the light saturation curve, and chlorophyll a (Chl a) specific absorption coefficient (āph*) between the sinking microalgal community and the <span class="hlt">ice</span> algal community were similar and were distinctly different from the phytoplankton community. The significant linear relationship between αB and PmB, which was obtained among the three groups, may suggest that a photo-acclimation strategy is common for all algal communities under the low light regime of the early season. Although the sinking algal community could be held for the entire duration of deployment at maximum, this community remained photosynthetically active once exposed to light. This response suggests that sinking algal communities can be the seed population, which results in a subsequent phytoplankton bloom under the <span class="hlt">sea</span> <span class="hlt">ice</span> or in a surface layer, as well as representing food for the higher trophic level consumers in the Arctic Ocean even before the receding of the <span class="hlt">sea</span> <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10583953','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10583953"><span id="translatedtitle">Satellite Evidence for an Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Cover in Transformation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Johannessen; Shalina; Miles</p> <p>1999-12-01</p> <p>Recent research using microwave satellite remote sensing data has established that there has been a reduction of about 3 percent per decade in the areal extent of the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover since 1978, although it is unknown whether the nature of the perennial <span class="hlt">ice</span> pack has changed. These data were used to quantify changes in the <span class="hlt">ice</span> cover's composition, revealing a substantial reduction of about 14 percent in the area of multiyear <span class="hlt">ice</span> in winter during the period from 1978 to 1998. There also appears to be a strong correlation between the area of multiyear <span class="hlt">ice</span> and the spatially averaged thickness of the perennial <span class="hlt">ice</span> pack, which suggests that the satellite-derived areal decreases represent substantial rather than only peripheral changes. If this apparent transformation continues, it may lead to a markedly different <span class="hlt">ice</span> regime in the Arctic, altering heat and mass exchanges as well as ocean stratification. PMID:10583953</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GeoRL..29.1956C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GeoRL..29.1956C"><span id="translatedtitle">A rapidly declining perennial <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Comiso, Josefino C.</p> <p>2002-10-01</p> <p>The perennial <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the Arctic is shown to be declining at -9% per decade using satellite data from 1978 to 2000. A sustained decline at this rate would mean the disappearance of the multiyear <span class="hlt">ice</span> cover during this century and drastic changes in the Arctic climate system. An apparent increase in the fraction of second year <span class="hlt">ice</span> in the 1990s is also inferred suggesting an overall thinning of the <span class="hlt">ice</span> cover. Surface <span class="hlt">ice</span> temperatures derived from satellite data are negatively correlated with perennial <span class="hlt">ice</span> area and are shown to be increasing at the rate of 1.2 K per decade. The latter implies longer melt periods and therefore decreasing <span class="hlt">ice</span> volume in the more recent years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/107838','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/107838"><span id="translatedtitle">Eastern-western Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> analysis, 1993</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1993-12-31</p> <p>This publication is the 20th edition of the annual Arctic <span class="hlt">sea-ice</span> atlases prepared by the JIC. The atlas contains weekly charts depicting Northern Hemisphere <span class="hlt">ice</span> conditions and extent. The significant use of high resolution satellite imagery, combined with valuable <span class="hlt">ice</span> reconnaissance data from various sources, has greatly improved the accuracy of these analyses. The purpose of this atlas is to provide the user with reliable weekly hemispheric <span class="hlt">ice</span> analyses. These charts are prepared by experienced Navy and NOAA <span class="hlt">ice</span> analysts who plot and evaluate numerous data sources: (a) Conventional shore station, ship, and aerial reconnaissance observations; and (b) Satellite data from various sensors. Table I, located on the inside back cover, lists these sensors and their availability. A final product is synthesized from the inputs described above. When insufficient data is available, estimated boundaries are plotted, using meteorological data and computer generated <span class="hlt">ice</span> drift vectors to determine estimated <span class="hlt">ice</span> position.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C23B0793M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C23B0793M&link_type=ABSTRACT"><span id="translatedtitle">Multiyear <span class="hlt">ice</span> transport and small scale <span class="hlt">sea</span> <span class="hlt">ice</span> deformation near the Alaska coast measured by air-deployable <span class="hlt">Ice</span> Trackers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahoney, A. R.; Kasper, J.; Winsor, P.</p> <p>2015-12-01</p> <p>Highly complex patterns of <span class="hlt">ice</span> motion and deformation were captured by fifteen satellite-telemetered GPS buoys (known as <span class="hlt">Ice</span> Trackers) deployed near Barrow, Alaska, in spring 2015. Two pentagonal clusters of buoys were deployed on pack <span class="hlt">ice</span> by helicopter in the Beaufort <span class="hlt">Sea</span> between 20 and 80 km offshore. During deployment, <span class="hlt">ice</span> motion in the study region was effectively zero, but two days later the buoys captured a rapid transport event in which multiyear <span class="hlt">ice</span> from the Beaufort <span class="hlt">Sea</span> was flushed into the Chukchi <span class="hlt">Sea</span>. During this event, westward <span class="hlt">ice</span> motion began in the Chukchi <span class="hlt">Sea</span> and propagated eastward. This created new openings in the <span class="hlt">ice</span> and led to rapid elongation of the clusters as the westernmost buoys accelerated away from their neighbors to the east. The buoys tracked <span class="hlt">ice</span> velocities of over 1.5 ms-1, with fastest motion occurring closest to the coast indicating strong current shear. Three days later, <span class="hlt">ice</span> motion reversed and the two clusters became intermingled, rendering divergence calculations based on the area enclosed by clusters invalid. The data show no detectable difference in velocity between first year and multiyear <span class="hlt">ice</span> floes, but Lagrangian timeseries of SAR imagery centered on each buoy show that first year <span class="hlt">ice</span> underwent significant small-scale deformation during the event. The five remaining buoys were deployed by local residents on prominent ridges embedded in the landfast <span class="hlt">ice</span> within 16 km of Barrow in order to track the fate of such features after they detached from the coast. Break-up of the landfast <span class="hlt">ice</span> took place over a period of several days and, although the buoys each initially followed a similar eastward trajectory around Point Barrow into the Beaufort <span class="hlt">Sea</span>, they rapidly dispersed over an area more than 50 km across. With rapid environmental and socio-economic change in the Arctic, understanding the complexity of nearshore <span class="hlt">ice</span> motion is increasingly important for predict future changes in the <span class="hlt">ice</span> and the tracking <span class="hlt">ice</span>-related hazards</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.2659H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.2659H"><span id="translatedtitle">Recent changes in <span class="hlt">sea</span> <span class="hlt">ice</span> area flux through the Beaufort <span class="hlt">Sea</span> during the summer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Howell, Stephen E. L.; Brady, Michael; Derksen, Chris; Kelly, Richard E. J.</p> <p>2016-04-01</p> <p>Over the annual cycle, <span class="hlt">sea</span> <span class="hlt">ice</span> is sequestered from the Canadian Basin and transported through the Beaufort <span class="hlt">Sea</span> toward the Chukchi <span class="hlt">Sea</span>. In recent years, the Beaufort <span class="hlt">Sea</span> has experienced considerable <span class="hlt">ice</span> loss during the summer, which may be indicative of recent changes to this process. In order to investigate this, we quantify the <span class="hlt">sea</span> <span class="hlt">ice</span> area flux using RADARSAT from 1997 to 2014 at three gates in Beaufort <span class="hlt">Sea</span>: the Canadian Basin (entrance), mid-Beaufort (midpoint), and Chukchi (exit). There was a mean annual flux of 42 ± 56 × 103 km2 at the Canadian Basin gate, 94 ± 92 × 103 km2 at the mid-Beaufort gate and -83 ± 68 × 103 km2 at the Chukchi gate (positive and negative flux signs correspond to <span class="hlt">ice</span> inflow and outflow, respectively). The majority of <span class="hlt">ice</span> transport in Beaufort <span class="hlt">Sea</span> was found to occur from October to May providing replenishment for <span class="hlt">ice</span> lost during the summer months. The cross-strait gradient in <span class="hlt">sea</span> level pressure explains ˜40% of the variance in the <span class="hlt">ice</span> area flux at the gates. Remarkably, the mean July-October net <span class="hlt">sea</span> <span class="hlt">ice</span> area flux at the Chukchi gate decreased by ˜80% from 2008 to 2014 relative to 1997-2007 and became virtually <span class="hlt">ice</span>-free every year since 2008. This reduction was associated with younger (thinner) <span class="hlt">ice</span> that was unable to survive the summer melt season when either being sequestered from the Canadian Basin and transported through Beaufort <span class="hlt">Sea</span> during the melt season (2008-2011) or remaining immobile and present in the vicinity of the Chukchi gate during the melt season (2012-2014).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C51C..08M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C51C..08M"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> properties and processes in a warming Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maykut, G. A.</p> <p>2004-12-01</p> <p>The Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover is changing. Over the past few decades there has been a marked decrease in the areal extent and thickness of multiyear <span class="hlt">ice</span>. Open water fraction in summer has been increasing, with corresponding increases in first-year <span class="hlt">ice</span> fraction during the remainder of the year. Such changes have a profound impact on air-<span class="hlt">sea-ice</span> interactions in the Arctic. For example, there is increased input of solar heat to the ocean that is producing a positive feedback on <span class="hlt">ice</span> formation and decay, as well as affecting biological activity in the <span class="hlt">ice</span> and ocean. Recent observations in the Chukchi and Beaufort <span class="hlt">Seas</span> help to illustrate the magnitude of the environmental changes. Work during the SHEBA Program has shown substantial thinning of second-year and multiyear <span class="hlt">ice</span> in this region, with almost half of the total summer melt occurring at the base of the <span class="hlt">ice</span> due to heat transfer from the ocean. Surface hydrography and tracer studies indicate that solar heating of the mixed layer, enhanced by a more mobile <span class="hlt">ice</span> cover with larger fractions of leads and open water, plays the major role in ocean-<span class="hlt">ice</span> heat transfer. Future <span class="hlt">sea</span> <span class="hlt">ice</span> research in the Arctic needs to focus strongly on the consequences of these and other ongoing changes. To do so will require interdisciplinary studies that combine field observations and large-scale modeling efforts. Such studies and a more fundamental understanding of the underlying processes are needed to assess potential changes in western Arctic shelf ecosystems and the related impacts on coastal communities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6578049','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6578049"><span id="translatedtitle">Global <span class="hlt">ice</span>-sheet system interlocked by <span class="hlt">sea</span> level</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Denton, G.H.; Hughes, T.J.; Karlen, W.</p> <p>1986-01-01</p> <p>Denton and Hughes postulated that <span class="hlt">sea</span> level linked a global <span class="hlt">ice</span>-sheet system with both terrestrial and grounded marine components during later Quaternary <span class="hlt">ice</span> ages. Summer temperature changes near Northern Hemisphere melting margins initiated <span class="hlt">sea</span>-level fluctuations that controlled marine components in both polar hemispheres. It was further proposed that variations of this <span class="hlt">ice</span>-sheet system amplified and transmitted Milankovitch summer half-year insolation changes between 45 and 75/sup 0/N into global climatic changes. New tests of this hypothesis implicate <span class="hlt">sea</span> level as a major control of the areal extent of grounded portions of the Antarctic <span class="hlt">Ice</span> Sheet. But factors other than areal changes of the grounded Antarctic <span class="hlt">Ice</span> Sheet may have strongly influenced Southern Hemisphere climate and terminated the last <span class="hlt">ice</span> age simultaneously in both polar hemispheres. Atmospheric carbon dioxide linked to high-latitude oceans is the most likely candidate, but another potential influence was high-frequency climatic oscillations. It is postulated that variations in atmospheric carbon dioxide acted through an Antarctic <span class="hlt">ice</span> shelf linked to the grounded <span class="hlt">ice</span> sheet to produce and terminate Southern Hemisphere <span class="hlt">ice</span>-age climate. It is further postulated that Milankovitch summer insolation combined with a warm-high frequency oscillation caused marked recession of Northern Hemisphere <span class="hlt">ice</span>-sheet melting margins and the North Atlantic polar front about 14,000 /sup 14/C yr B.P. This permitted renewed formation of North Atlantic Deep Water, which could well have controlled atmospheric carbon dioxide. Combined melting and consequent <span class="hlt">sea</span>-level rise from the three warming factors initiated irreversible collapse of the interlocked global <span class="hlt">ice</span>-sheet system, which was at its largest but most vulnerable configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51A0675B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51A0675B"><span id="translatedtitle">Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Reemergence Mechanisms in a Model Hierarchy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bushuk, M.; Giannakis, D.</p> <p>2015-12-01</p> <p>Lagged correlation analysis of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> area anomalies reveals that melt season <span class="hlt">sea</span> <span class="hlt">ice</span> anomalies tend to recur the following growth season, and growth season anomalies tend to recur the following melt season. In this work, the regional and temporal characteristics of this phenomenon, termed <span class="hlt">sea-ice</span> reemergence, are investigated in a hierarchy of climate models. Coupled nonlinear Laplacian spectral analysis (NLSA), a multivariate data analysis technique, is used to study the covariability of Arctic <span class="hlt">sea-ice</span> concentration (SIC), <span class="hlt">sea</span>-surface temperature (SST), <span class="hlt">sea</span>-level pressure (SLP), and <span class="hlt">sea-ice</span> thickness (SIT). Two mechanisms related to melt season to growth season reemergence are identified: (1) An SST-SIC mechanism, related to local imprinting and persistence of SST anomalies in the seasonal <span class="hlt">ice</span> zones, and (2) an SLP-SIC mechanism, related to winter-to-winter regime persistence of large-scale SLP teleconnection patterns. An SIT-SIC growth season to melt season reemergence mechanism is also identified, related to winter persistence of SIT anomalies in the central Arctic. The representation of these mechanisms is investigated using the model hierarchy to determine the relative roles of the ocean, atmosphere, and <span class="hlt">sea</span> <span class="hlt">ice</span> itself in producing reemergence. It is found that the SST-based and SIT-based mechanisms can exist as stand-alone processes, whereas the SLP mechanism cannot. Dynamical feedback from the ocean to the atmosphere is found to be essential in creating large-scale organized patterns of SIC-SLP covariability. A set of reemergence metrics is introduced, by which one can judge the amplitude and phase of reemergence events and associated mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000101018&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Continental%2BDrift%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000101018&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Continental%2BDrift%2529"><span id="translatedtitle">Active Microwave Remote Sensing Observations of Weddell <span class="hlt">Sea</span> <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Drinkwater, Mark R.</p> <p>1997-01-01</p> <p>Since July 1991, the European Space Agency's ERS-1 and ERS-2 satellites have acquired radar data of the Weddell <span class="hlt">Sea</span>, Antarctica. The Active Microwave Instrument on board ERS has two modes; SAR and Scatterometer. Two receiving stations enable direct downlink and recording of high bit-rate, high resolution SAR image data of this region. When not in an imaging mode, when direct SAR downlink is not possible, or when a receiving station is inoperable, the latter mode allows normalized radar cross-section data to be acquired. These low bit-rate ERS scatterometer data are tape recorded, downlinked and processed off-line. Recent advances in image generation from Scatterometer backscatter measurements enable complementary medium-scale resolution images to be made during periods when SAR images cannot be acquired. Together, these combined C-band microwave image data have for the first time enabled uninterrupted night and day coverage of the Weddell <span class="hlt">Sea</span> region at both high (25 m) and medium-scale (-20 km) resolutions. C-band ERS-1 radar data are analyzed in conjunction with field data from two simultaneous field experiments in 1992. Satellite radar signature data are compared with shipborne radar data to extract a regional and seasonal signature database for recognition of <span class="hlt">ice</span> types in the images. Performance of automated <span class="hlt">sea-ice</span> tracking algorithms is tested on Antarctic data to evaluate their success. Examples demonstrate that both winter and summer <span class="hlt">ice</span> can be effectively tracked. The kinematics of the main <span class="hlt">ice</span> zones within the Weddell <span class="hlt">Sea</span> are illustrated, together with the complementary time-dependencies in their radar signatures. Time-series of satellite images are used to illustrate the development of the Weddell <span class="hlt">Sea</span> <span class="hlt">ice</span> cover from its austral summer minimum (February) to its winter maximum (September). The combination of time-dependent microwave signatures and <span class="hlt">ice</span> dynamics tracking enable various drift regimes to be defined which relate closely to the circulation of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7955K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7955K"><span id="translatedtitle">Springtime atmospheric transport controls Arctic summer <span class="hlt">sea-ice</span> extent</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kapsch, Marie; Graversen, Rune; Tjernström, Michael</p> <p>2013-04-01</p> <p>The <span class="hlt">sea-ice</span> 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 <span class="hlt">ice</span> retreat are among others: changes in surface air temperature (SAT; Lindsay and Zhang, 2005), <span class="hlt">ice</span> 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 <span class="hlt">ice</span> 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 <span class="hlt">ice</span> variability? A comparison of years with an anomalously large September <span class="hlt">sea-ice</span> extent (HIYs - high <span class="hlt">ice</span> years) with years showing an anomalously small <span class="hlt">ice</span> extent (LIYs - low <span class="hlt">ice</span> years) reveals that the <span class="hlt">ice</span> variability is most pronounced in the Arctic Ocean north of Siberia (which became almost entirely <span class="hlt">ice</span> free in September of 2007 and 2012). Significant <span class="hlt">ice</span>-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 <span class="hlt">sea</span> <span class="hlt">ice</span> during the subsequent months. In years where the end-of-summer <span class="hlt">sea-ice</span> extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the <span class="hlt">ice</span> 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 <span class="hlt">ice</span> anomaly begins to appear and the surface albedo therefore becomes anomalously low, the net shortwave radiation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940030006&hterms=FRAM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFRAM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940030006&hterms=FRAM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFRAM"><span id="translatedtitle">Monitoring <span class="hlt">sea</span> <span class="hlt">ice</span> flux through Fram Strait</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schweiger, Axel J.; Rothrock, D. Andrew</p> <p>1994-01-01</p> <p>A methodology for estimating daily <span class="hlt">ice</span> velocity through Fram Strait is presented. <span class="hlt">Ice</span> velocity fields are estimated from a combination of motions observed by SAR (Synthetic Aperture Radar) or buoys and drift estimated by a simple wind drift model. The analysis includes <span class="hlt">ice</span> motion vectors from approximately 300 pairs of ERS-1 images, Feb. - Jun. 1993. ESA UILR8 low resolution images derived from the Fast Delivery (FD) products are analyzed to produce <span class="hlt">ice</span> velocity vectors using a semi-automated interactive approach. This method reveals substantial variability in the <span class="hlt">ice</span> motion field that would not be apparent from a single data source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...629465G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...629465G&link_type=ABSTRACT"><span id="translatedtitle">Biopolymers form a gelatinous microlayer at the air-<span class="hlt">sea</span> interface when Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> melts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galgani, Luisa; Piontek, Judith; Engel, Anja</p> <p>2016-07-01</p> <p>The interface layer between ocean and atmosphere is only a couple of micrometers thick but plays a critical role in climate relevant processes, including the air-<span class="hlt">sea</span> exchange of gas and heat and the emission of primary organic aerosols (POA). Recent findings suggest that low-level cloud formation above the Arctic Ocean may be linked to organic polymers produced by marine microorganisms. <span class="hlt">Sea</span> <span class="hlt">ice</span> harbors high amounts of polymeric substances that are produced by cells growing within the <span class="hlt">sea-ice</span> brine. Here, we report from a research cruise to the central Arctic Ocean in 2012. Our study shows that microbial polymers accumulate at the air-<span class="hlt">sea</span> interface when the <span class="hlt">sea</span> <span class="hlt">ice</span> melts. Proteinaceous compounds represented the major fraction of polymers supporting the formation of a gelatinous interface microlayer and providing a hitherto unrecognized potential source of marine POA. Our study indicates a novel link between <span class="hlt">sea</span> <span class="hlt">ice</span>-ocean and atmosphere that may be sensitive to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20080036090&hterms=concentration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dconcentration','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20080036090&hterms=concentration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dconcentration"><span id="translatedtitle">Ross <span class="hlt">Sea</span> Polynyas: Response of <span class="hlt">Ice</span> Concentration Retrievals to Large Areas of Thin <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kwok, R.; Comiso, J. C.; Martin, S.; Drucker, R.</p> <p>2007-01-01</p> <p>For a 3-month period between May and July of 2005, we examine the response of the Advanced Microwave Scanning Radiometer (AMSR-E) Enhanced NASA Team 2 (NT2) and AMSR-E Bootstrap (ABA) <span class="hlt">ice</span> concentration algorithms to large areas of thin <span class="hlt">ice</span> of the Ross <span class="hlt">Sea</span> polynyas. Coincident Envisat Synthetic Aperture Radar (SAR) coverage of the region during this period offers a detailed look at the development of the polynyas within several hundred kilometers of the <span class="hlt">ice</span> front. The high-resolution imagery and derived <span class="hlt">ice</span> motion fields show bands of polynya <span class="hlt">ice</span>, covering up to approximately 105 km(sup 2) of the Ross <span class="hlt">Sea</span>, that are associated with wind-forced advection. In this study, <span class="hlt">ice</span> thickness from AMSR-E 36 GHz polarization information serves as the basis for examination of the response. The quality of the thickness of newly formed <span class="hlt">sea</span> <span class="hlt">ice</span> (<10 cm) from AMSR-E is first assessed with thickness estimates derived from <span class="hlt">ice</span> surface temperatures from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The effect of large areas of thin <span class="hlt">ice</span> in lowering the <span class="hlt">ice</span> concentration estimates from both NT2/ABA approaches is clearly demonstrated. Results show relatively robust relationships between retrieved <span class="hlt">ice</span> concentrations and thin <span class="hlt">ice</span> thickness estimates that differ between the two algorithms. These relationships define the approximate spatial coincidence of <span class="hlt">ice</span> concentration and thickness isopleths. Using the 83% (ABA) and 91% (NT2) isopleths as polynya boundaries, we show that the computed coverage compares well with that using the estimated 10-cm thickness contour. The thin <span class="hlt">ice</span> response characterized here suggests that in regions with polynyas, the retrieval results could be used to provide useful geophysical information, namely thickness and coverage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016TCry...10..245S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016TCry...10..245S&link_type=ABSTRACT"><span id="translatedtitle">Halogen-based reconstruction of Russian Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> area from the Akademii Nauk <span class="hlt">ice</span> core (Severnaya Zemlya)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spolaor, A.; Opel, T.; McConnell, J. R.; Maselli, O. J.; Spreen, G.; Varin, C.; Kirchgeorg, T.; Fritzsche, D.; Saiz-Lopez, A.; Vallelonga, P.</p> <p>2016-01-01</p> <p>The role of <span class="hlt">sea</span> <span class="hlt">ice</span> in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere-ocean heat and gas exchange. Here we present a reconstruction of 1950 to 1998 AD <span class="hlt">sea</span> <span class="hlt">ice</span> in the Laptev <span class="hlt">Sea</span> based on the Akademii Nauk <span class="hlt">ice</span> core (Severnaya Zemlya, Russian Arctic). The chemistry of halogens bromine (Br) and iodine (I) is strongly active and influenced by <span class="hlt">sea</span> <span class="hlt">ice</span> dynamics, in terms of physical, chemical and biological process. Bromine reacts on the <span class="hlt">sea</span> <span class="hlt">ice</span> surface in autocatalyzing "bromine explosion" events, causing an enrichment of the Br / Na ratio and hence a bromine excess (Brexc) in snow compared to that in seawater. Iodine is suggested to be emitted from algal communities growing under <span class="hlt">sea</span> <span class="hlt">ice</span>. The results suggest a connection between Brexc and spring <span class="hlt">sea</span> <span class="hlt">ice</span> area, as well as a connection between iodine concentration and summer <span class="hlt">sea</span> <span class="hlt">ice</span> area. The correlation coefficients obtained between Brexc and spring <span class="hlt">sea</span> <span class="hlt">ice</span> (r = 0.44) as well as between iodine and summer <span class="hlt">sea</span> <span class="hlt">ice</span> (r = 0.50) for the Laptev <span class="hlt">Sea</span> suggest that these two halogens could become good candidates for extended reconstructions of past <span class="hlt">sea</span> <span class="hlt">ice</span> changes in the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/400792','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/400792"><span id="translatedtitle">Self-excited oscillations in <span class="hlt">sea</span> <span class="hlt">ice</span> and evaluation of the <span class="hlt">ice</span> forces</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Smirnov, V.N.</p> <p>1996-12-01</p> <p>The processes of the dynamical interactions of the <span class="hlt">ice</span> are described. Special attention is given to the self-excited oscillating processes when the <span class="hlt">ice</span> goes through periodical deformations similar to these which appear in the structures in the <span class="hlt">sea</span> <span class="hlt">ice</span>. The range of the self-excited oscillations periods is from 0.1 s to 20 s. The jump-like processes transform themselves into the quasi-harmonical ones up to sound frequency range. For comparison purposes the spectra of the frictional self-excited oscillations in the glaciers are presented. An iceberg interacting with the drifting <span class="hlt">ice</span> also forms self-excited oscillating system with period of up to 10 s. An example of numerical evaluation of the forces of interaction between a drifting <span class="hlt">ice</span> island and the <span class="hlt">sea</span> <span class="hlt">ice</span> is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C51A0490P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C51A0490P"><span id="translatedtitle">New <span class="hlt">Ice</span>Tracker Tool Depicts Forward and Backward Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Trajectories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pfirman, S. L.; Campbell, G.; Tremblay, B.; Newton, R.; Meier, W.</p> <p>2013-12-01</p> <p>The <span class="hlt">Ice</span>Tracker allows researchers, educators and the public to depict the forward drift trajectories of <span class="hlt">sea</span> <span class="hlt">ice</span>, as well as back trajectories showing the path the <span class="hlt">ice</span> took to the specified location. Users enter in the location and date of an <span class="hlt">ice</span> parcel - or parcels -- of interest, then select a later or earlier date, depending on whether they want to see the forward or the backward trajectory. The database for the <span class="hlt">Ice</span>Tracker contains <span class="hlt">ice</span> motion vectors based upon a pattern recognition algorithm applied to images of <span class="hlt">sea</span> <span class="hlt">ice</span> derived from microwave satellite data. <span class="hlt">Ice</span> motion vector plots are single day motion estimates. The available database starts November 1978 and runs to the present with ca. 1 month delay. <span class="hlt">Ice</span>Tracker output includes both an image of the <span class="hlt">ice</span> motion path as well as a data file that has quasi-daily date, latitude, longitude, estimated <span class="hlt">sea</span> <span class="hlt">ice</span> age, <span class="hlt">ice</span> drift speed, mean air temperature, and water depth. One can overlay different days on the same plot in different colors for comparing different seasons. This presentation highlights research, education, and outreach applications of the tool. Research applications include estimating the origin and melt location of sediment and contaminants sampled on or in <span class="hlt">sea</span> <span class="hlt">ice</span>, assessing potential trajectories oil spilled in <span class="hlt">ice</span>-infested waters, documenting seasonal and interannual variability in <span class="hlt">ice</span> drift trajectories from specific locations, defining the typical origins of <span class="hlt">ice</span> that tend to melt in an area of interest, such as a polynya, and assessing the deviation from drift of polar bear foraging. The <span class="hlt">Ice</span>Tracker can also be used in the social sciences, for example recreating Nansen's historic 1893-1896 trans-Arctic drift with the Fram under modern conditions and considering the implications of alternative fates. Educational purposes include teaching students about <span class="hlt">ice</span> dynamics and interannual variability by setting up team competitions to be the first to reach the North Pole or some other location. Applications</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C13C..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C13C..05M"><span id="translatedtitle">Surface and basal <span class="hlt">sea</span> <span class="hlt">ice</span> melt from autonomous buoy arrays during the 2014 <span class="hlt">sea</span> <span class="hlt">ice</span> retreat in the Beaufort/Chukchi <span class="hlt">Seas</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maksym, T. L.; Wilkinson, J.; Hwang, P. B.</p> <p>2014-12-01</p> <p>As the Arctic continues its transition to a seasonal <span class="hlt">ice</span> cover, the nature and role of the processes driving <span class="hlt">sea</span> <span class="hlt">ice</span> retreat are expected to change. Key questions revolve around how the coupling between dynamics and thermodynamic processes and potential changes in the role of melt ponds contribute to an accelerated seasonal <span class="hlt">ice</span> retreat. To address these issues, 44 autonomous platforms were deployed in four arrays in the Beaufort <span class="hlt">Sea</span> in March, 2014, with an additional array deployed in August in the Chukchi <span class="hlt">Sea</span> to monitor the evolution of <span class="hlt">ice</span> conditions during the seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> retreat. Each "5-dice" array included four or five co-sited <span class="hlt">ice</span> mass balance buoys (IMB) and wave buoys with digital cameras, and one automatic weather station (AWS) at the array center. The sensors on these buoys, combined with satellite imagery monitoring the large-scale evolution of the <span class="hlt">ice</span> cover, provide a near-complete history of the processes involved in the seasonal melt of <span class="hlt">sea</span> <span class="hlt">ice</span>. We present a preliminary analysis of the contributions of several key processes to the seasonal <span class="hlt">ice</span> decay. The evolution of surface ponding was observed at several sites with differing <span class="hlt">ice</span> types and surface morphologies. The records of surface melt and <span class="hlt">ice</span> thickness demonstrate a key role of <span class="hlt">ice</span> type in driving the evolution of the <span class="hlt">ice</span> cover. Analysis of the surface forcing and estimates of solar energy partitioning between the surface and upper ocean is compared to the surface and basal mass balance from the IMBs. The role of <span class="hlt">ice</span> divergence and deformation in driving <span class="hlt">sea</span> <span class="hlt">ice</span> decay - in particular its role in accelerating thermodynamic melt processes - is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C23B0403B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C23B0403B"><span id="translatedtitle"><span class="hlt">Ice</span> loss from West Antarctica to the Bellingshausen <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bingham, R. G.; Smith, A.; King, E. C.; Gudmundsson, G. H.; Thomas, E. R.</p> <p>2014-12-01</p> <p>Determination of Antarctica's <span class="hlt">ice</span>-sheet mass balance (more correctly, mass imbalance) is of paramount concern due to its impact on global <span class="hlt">sea</span> levels. Monitoring with satellite remote sensing since the early 1990s has demonstrated that the imbalance has become progressively more negative, with losses dominated by the ocean-forced drawdown of <span class="hlt">ice</span> from West Antarctica into the Amundsen and Bellingshausen <span class="hlt">Seas</span>. Recent years have hosted unprecedented study and increased understanding of the <span class="hlt">ice</span>-ocean processes contributing to Amundsen-<span class="hlt">Sea</span> losses, leaving ocean-forced <span class="hlt">ice</span>-dynamical losses to the Bellingshausen <span class="hlt">Sea</span> relatively neglected. We therefore present here, with the aid of dedicated field data in austral season 2009/2010, a detailed assessment of the mass imbalance of Ferrigno <span class="hlt">Ice</span> Stream (FIS), the dominant contributor of mass directly to the Bellingshausen <span class="hlt">Sea</span>. We assess mass imbalance using the input-output method for (i) 1992, and (ii) 2010; the temporal markers being defined by the acquisition of the first comprehensive satellite-velocity coverage and the acquisition of the field measurements respectively. Input by snowfall is estimated using existing maps of Antarctic snow accumulation calibrated with 2010-acquired field data in the form of a 20-m <span class="hlt">ice</span> core recovered at the upper FIS <span class="hlt">ice</span> divide and englacial layering across the catchment imaged with 500 MHz over-snow radar. Output by discharge across the grounding line requires measurements of <span class="hlt">ice</span> velocity and depth across a "flux gate." In 2010, we obtained flux gate measurements directly from the field using DGPS and 2 MHz over-snow radar, and we also refer to satellite-acquired <span class="hlt">ice</span>-velocity data (MeASUREs) and airborne-acquired <span class="hlt">ice</span> depths (Operation <span class="hlt">Ice</span>Bridge) acquired at a similar time. Output from 1992 is calculated using 1992-acquired satellite <span class="hlt">ice</span>-velocities (Rignot, 2006) and <span class="hlt">ice</span> depth retroactively inferred from the 2010-acquired <span class="hlt">ice</span> depth corrected for 1992-2010 surface elevation loss. We calculate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C31A0610H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C31A0610H"><span id="translatedtitle">Comparison of the MASIE with Other <span class="hlt">Sea</span> <span class="hlt">Ice</span> Extent Products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Helfrich, S.; Jackson, B. M.; Clemente-Colon, P.; Fetterer, F. M.; Savoie, M.</p> <p>2011-12-01</p> <p>The Multisensor Analyzed <span class="hlt">Sea</span> <span class="hlt">Ice</span> Extent (MASIE) has been made available to the public via the National Snow and <span class="hlt">Ice</span> Data Center (NSIDC) since 2010, with daily data covering from January 2006 on. The MASIE is based on NOAA <span class="hlt">ice</span> and snow cover analysis utilizing nearly 30 data sources to generate an integrated daily <span class="hlt">ice</span> cover. While the resolution of the imagery sources ranges from 100m resolution synthetic aperture radar (SAR) to coarse 48km passive microwave (PM) data, the MASIE analysis attempts to synthesize the data sources into a 4km identification of <span class="hlt">sea-ice</span> covered areas over the Northern Hemisphere. The MASIE differs from other <span class="hlt">ice</span> extent data sources in three key ways. First, MASIE applies multiple data sources ranging from point sources and models to imagery acquired through a wide range in the electromagnetic spectrum. Second, MASIE has a moderate resolution so it is able to account relatively well for the <span class="hlt">ice</span> extent in smaller bays, straits, coastlines, and along the marginal <span class="hlt">ice</span> zone, particularly when compared to passive microwave sources. And third, MASIE relies on expert identification of the <span class="hlt">ice</span> and manual assimilation of the multiple data sources rather than on a given automated algorithm. This study compares the MASIE with other <span class="hlt">sea</span> extent products to understand their similarities and try to explain their differences. We analyze temporal and spatial behavior between <span class="hlt">ice</span> extents from different products over the Northern Hemisphere, as well as within selected regions of interest. This comparison will help users in the interpretation of popular <span class="hlt">ice</span> cover products and their applications in weather forecasting, ocean and <span class="hlt">ice</span> modeling, safe navigation, and climate monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830043095&hterms=cinematography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcinematography','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830043095&hterms=cinematography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcinematography"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> motion measurements from Seasat SAR images</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leberl, F.; Raggam, J.; Elachi, C.; Campbell, W. J.</p> <p>1983-01-01</p> <p>Data from the Seasat synthetic aperture radar (SAR) experiment are analyzed in order to determine the accuracy of this information for mapping the distribution of <span class="hlt">sea</span> <span class="hlt">ice</span> and its motion. Data from observations of <span class="hlt">sea</span> <span class="hlt">ice</span> in the Beaufort <span class="hlt">Sea</span> from seven sequential orbits of the satellite were selected to study the capabilities and limitations of spaceborne radar application to <span class="hlt">sea-ice</span> mapping. Results show that there is no difficulty in identifying homologue <span class="hlt">ice</span> features on sequential radar images and the accuracy is entirely controlled by the accuracy of the orbit data and the geometric calibration of the sensor. Conventional radargrammetric methods are found to serve well for satellite radar <span class="hlt">ice</span> mapping, while ground control points can be used to calibrate the <span class="hlt">ice</span> location and motion measurements in the cases where orbit data and sensor calibration are lacking. The <span class="hlt">ice</span> motion was determined to be approximately 6.4 + or - 0.5 km/day. In addition, the accuracy of pixel location was found over land areas. The use of one control point in 10,000 sq km produced an accuracy of about + or 150 m, while with a higher density of control points (7 in 1000 sq km) the location accuracy improves to the image resolution of + or - 25 m. This is found to be applicable for both optical and digital data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.C22A..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.C22A..05D"><span id="translatedtitle">Co-incident 3D mapping of <span class="hlt">sea</span> <span class="hlt">ice</span> surface elevation and <span class="hlt">ice</span> draft in the Beaufort <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doble, M. J.; Forsberg, R.; Haas, C.; Hanson, S.; Hendriks, S.; Martin, T.; Skourup, H.; Wadhams, P.</p> <p>2007-12-01</p> <p>Co-incident measurements of <span class="hlt">sea</span> <span class="hlt">ice</span> freeboard, thickness and draft were made during the Applied Physics Laboratory <span class="hlt">Ice</span> Station (APLIS), in April 2007. The campaign was the first time that full three-dimensional mapping of <span class="hlt">sea</span> <span class="hlt">ice</span> freeboard and <span class="hlt">sea</span> <span class="hlt">ice</span> draft have been achieved simultaneously. Freeboard was measured across a swath width of 300 m at 1 m spatial resolution, using a laser profilometer flown aboard a Twin Otter aircraft. <span class="hlt">Ice</span> draft was measured across a swath width of approximately 80 m at 0.5 m spatial resolution, using a Gavia AUV fitted with a GeoAcoustics phase-measuring swath sonar. <span class="hlt">Ice</span> thickness was also measured along co-incident tracks using a helicopter-borne electromagnetic sounding instrument (HEM bird). The laser profilometer and AUV-mounted sonar rely on the assumption of isostatic balance when deriving <span class="hlt">ice</span> thickness estimates from the <span class="hlt">ice</span> surface and underside profiles, while the HEM bird records both surfaces simultaneously and independently, though averaging over a significant footprint (30 m) for the underside of the <span class="hlt">ice</span>. Though the extent of the APLIS dataset was limited by the radius of AUV operations, the dataset will significantly improve our understanding of <span class="hlt">ice</span> volume in deformed <span class="hlt">ice</span> areas, particularly our understanding of the contribution of ridges and rubble fields to total Arctic <span class="hlt">ice</span> volume, their isostatic balance and questions of block-scale porosity. The data will serve to better constrain the effects of porosity and footprint on the operational HEM measurements and, conversely, the HEM measurements will allow conclusions about the impact of the isostatic balance assumption on <span class="hlt">ice</span> thickness estimates derived from mapping of one surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CliPa..12..749H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CliPa..12..749H"><span id="translatedtitle">Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> simulation in the PlioMIP ensemble</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Howell, Fergus W.; Haywood, Alan M.; Otto-Bliesner, Bette L.; Bragg, Fran; Chan, Wing-Le; Chandler, Mark A.; Contoux, Camille; Kamae, Youichi; Abe-Ouchi, Ayako; Rosenbloom, Nan A.; Stepanek, Christian; Zhang, Zhongshi</p> <p>2016-03-01</p> <p>Eight general circulation models have simulated the mid-Pliocene warm period (mid-Pliocene, 3.264 to 3.025 Ma) as part of the Pliocene Modelling Intercomparison Project (PlioMIP). Here, we analyse and compare their simulation of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> for both the pre-industrial period and the mid-Pliocene. Mid-Pliocene <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and extent is reduced, and the model spread of extent is more than twice the pre-industrial spread in some summer months. Half of the PlioMIP models simulate <span class="hlt">ice</span>-free conditions in the mid-Pliocene. This spread amongst the ensemble is in line with the uncertainties amongst proxy reconstructions for mid-Pliocene <span class="hlt">sea</span> <span class="hlt">ice</span> extent. Correlations between mid-Pliocene Arctic temperatures and <span class="hlt">sea</span> <span class="hlt">ice</span> extents are almost twice as strong as the equivalent correlations for the pre-industrial simulations. The need for more comprehensive <span class="hlt">sea</span> <span class="hlt">ice</span> proxy data is highlighted, in order to better compare model performances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41A0691C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41A0691C"><span id="translatedtitle">Decadal variability of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> in the Canada Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Connor, L. N.</p> <p>2015-12-01</p> <p>A series of spring Arctic flight campaigns surveying a region over the Canada Basin, from 2006 to 2015, has resulted in unique observations that reveal new details of <span class="hlt">sea</span> <span class="hlt">ice</span> leads and freeboard evolution, during a decade of significant interannual variability in the Arctic <span class="hlt">ice</span> cover. The series began in 2006 with a joint NASA/NOAA airborne altimetry campaign over a 1300 km survey line northwest of the Canadian Archipelago extending into the northern Beaufort <span class="hlt">Sea</span>. Operation <span class="hlt">Ice</span>Bridge (OIB) took up this flight line again in 2009 and repeated it annually through 2012. Additional observations have been collected along a 1000+ km flight line, in the southern Canada Basin and eastern Beaufort <span class="hlt">Sea</span>, between 2009 and 2015. Here we examine laser altimetry, snow radar data, and high-resolution visible imagery to better understand the frequency and distribution of leads and <span class="hlt">ice</span> floes, the characteristics of first- and multi-year <span class="hlt">ice</span> types in the survey region, and their impact on the derivation and accuracy of <span class="hlt">sea</span> <span class="hlt">ice</span> freeboard. We demonstrate a novel lead detection methodology that depends only upon laser altimeter measurements, and we quantify the impact of low lead frequencies on estimates of instantaneous <span class="hlt">sea</span> surface height. The analysis reveals a variable springtime freeboard north of 78° N, significantly reduced after 2006, and a notable lead outbreak over the Canada Basin during 2010.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010403','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010403"><span id="translatedtitle">Satellite Observations of Antarctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Thickness and Volume</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurtz, Nathan; Markus, Thorsten</p> <p>2012-01-01</p> <p>We utilize satellite laser altimetry data from ICESat combined with passive microwave measurements to analyze basin-wide changes in Antarctic <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and volume over a 5 year period from 2003-2008. <span class="hlt">Sea</span> <span class="hlt">ice</span> thickness exhibits a small negative trend while area increases in the summer and fall balanced losses in thickness leading to small overall volume changes. Using a five year time-series, we show that only small <span class="hlt">ice</span> thickness changes of less than -0.03 m/yr and volume changes of -266 cu km/yr and 160 cu km/yr occurred for the spring and summer periods, respectively. The calculated thickness and volume trends are small compared to the observational time period and interannual variability which masks the determination of long-term trend or cyclical variability in the <span class="hlt">sea</span> <span class="hlt">ice</span> cover. These results are in stark contrast to the much greater observed losses in Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> volume and illustrate the different hemispheric changes of the polar <span class="hlt">sea</span> <span class="hlt">ice</span> covers in recent years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26032323','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26032323"><span id="translatedtitle">Regional variability in <span class="hlt">sea</span> <span class="hlt">ice</span> melt in a changing Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perovich, Donald K; Richter-Menge, Jacqueline A</p> <p>2015-07-13</p> <p>In recent years, the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover has undergone a precipitous decline in summer extent. The <span class="hlt">sea</span> <span class="hlt">ice</span> mass balance integrates heat and provides insight on atmospheric and oceanic forcing. The amount of surface melt and bottom melt that occurs during the summer melt season was measured at 41 sites over the time period 1957 to 2014. There are large regional and temporal variations in both surface and bottom melting. Combined surface and bottom melt ranged from 16 to 294 cm, with a mean of 101 cm. The mean <span class="hlt">ice</span> equivalent surface melt was 48 cm and the mean bottom melt was 53 cm. On average, surface melting decreases moving northward from the Beaufort <span class="hlt">Sea</span> towards the North Pole; however interannual differences in atmospheric forcing can overwhelm the influence of latitude. Substantial increases in bottom melting are a major contributor to <span class="hlt">ice</span> losses in the Beaufort <span class="hlt">Sea</span>, due to decreases in <span class="hlt">ice</span> concentration. In the central Arctic, surface and bottom melting demonstrate interannual variability, but show no strong temporal trends from 2000 to 2014. This suggests that under current conditions, summer melting in the central Arctic is not large enough to completely remove the <span class="hlt">sea</span> <span class="hlt">ice</span> cover. PMID:26032323</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160004954&hterms=zhang&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dzhang','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160004954&hterms=zhang&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dzhang"><span id="translatedtitle">Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Simulation in the PlioMIP Ensemble</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Howell, Fergus W.; Haywood, Alan M.; Otto-Bliesner, Bette L.; Bragg, Fran; Chan, Wing-Le; Chandler, Mark A.; Contoux, Camille; Kamae, Youichi; Abe-Ouchi, Ayako; Rosenbloom, Nan A.; Stepanek, Christian; Zhang, Zhongshi</p> <p>2016-01-01</p> <p>Eight general circulation models have simulated the mid-Pliocene warm period (mid-Pliocene, 3.264 to 3.025 Ma) as part of the Pliocene Modelling Intercomparison Project (PlioMIP). Here, we analyse and compare their simulation of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> for both the pre-industrial period and the mid-Pliocene. Mid-Pliocene <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and extent is reduced, and the model spread of extent is more than twice the pre-industrial spread in some summer months. Half of the PlioMIP models simulate <span class="hlt">ice</span>-free conditions in the mid-Pliocene. This spread amongst the ensemble is in line with the uncertainties amongst proxy reconstructions for mid-Pliocene <span class="hlt">sea</span> <span class="hlt">ice</span> extent. Correlations between mid-Pliocene Arctic temperatures and <span class="hlt">sea</span> <span class="hlt">ice</span> extents are almost twice as strong as the equivalent correlations for the pre-industrial simulations. The need for more comprehensive <span class="hlt">sea</span> <span class="hlt">ice</span> proxy data is highlighted, in order to better compare model performances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4455714','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4455714"><span id="translatedtitle">Regional variability in <span class="hlt">sea</span> <span class="hlt">ice</span> melt in a changing Arctic</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Perovich, Donald K.; Richter-Menge, Jacqueline A.</p> <p>2015-01-01</p> <p>In recent years, the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover has undergone a precipitous decline in summer extent. The <span class="hlt">sea</span> <span class="hlt">ice</span> mass balance integrates heat and provides insight on atmospheric and oceanic forcing. The amount of surface melt and bottom melt that occurs during the summer melt season was measured at 41 sites over the time period 1957 to 2014. There are large regional and temporal variations in both surface and bottom melting. Combined surface and bottom melt ranged from 16 to 294 cm, with a mean of 101 cm. The mean <span class="hlt">ice</span> equivalent surface melt was 48 cm and the mean bottom melt was 53 cm. On average, surface melting decreases moving northward from the Beaufort <span class="hlt">Sea</span> towards the North Pole; however interannual differences in atmospheric forcing can overwhelm the influence of latitude. Substantial increases in bottom melting are a major contributor to <span class="hlt">ice</span> losses in the Beaufort <span class="hlt">Sea</span>, due to decreases in <span class="hlt">ice</span> concentration. In the central Arctic, surface and bottom melting demonstrate interannual variability, but show no strong temporal trends from 2000 to 2014. This suggests that under current conditions, summer melting in the central Arctic is not large enough to completely remove the <span class="hlt">sea</span> <span class="hlt">ice</span> cover. PMID:26032323</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850013448','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850013448"><span id="translatedtitle">Passive microwave remote sensing for <span class="hlt">sea</span> <span class="hlt">ice</span> research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1984-01-01</p> <p>Techniques for gathering data by remote sensors on satellites utilized for <span class="hlt">sea</span> <span class="hlt">ice</span> research are summarized. Measurement of brightness temperatures by a passive microwave imager converted to maps of total <span class="hlt">sea</span> <span class="hlt">ice</span> concentration and to the areal fractions covered by first year and multiyear <span class="hlt">ice</span> are described. Several ancillary observations, especially by means of automatic data buoys and submarines equipped with upward looking sonars, are needed to improve the validation and interpretation of satellite data. The design and performance characteristics of the Navy's Special Sensor Microwave Imager, expected to be in orbit in late 1985, are described. It is recommended that data from that instrument be processed to a form suitable for research applications and archived in a readily accessible form. The <span class="hlt">sea</span> <span class="hlt">ice</span> data products required for research purposes are described and recommendations for their archival and distribution to the scientific community are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1011619','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1011619"><span id="translatedtitle">Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> modeling with the material-point method.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Peterson, Kara J.; Bochev, Pavel Blagoveston</p> <p>2010-04-01</p> <p>Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> plays an important role in global climate by reflecting solar radiation and insulating the ocean from the atmosphere. Due to feedback effects, the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover is changing rapidly. To accurately model this change, high-resolution calculations must incorporate: (1) annual cycle of growth and melt due to radiative forcing; (2) mechanical deformation due to surface winds, ocean currents and Coriolis forces; and (3) localized effects of leads and ridges. We have demonstrated a new mathematical algorithm for solving the <span class="hlt">sea</span> <span class="hlt">ice</span> governing equations using the material-point method with an elastic-decohesive constitutive model. An initial comparison with the LANL CICE code indicates that the <span class="hlt">ice</span> edge is sharper using Materials-Point Method (MPM), but that many of the overall features are similar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27130467','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27130467"><span id="translatedtitle">Modeling oil weathering and transport in <span class="hlt">sea</span> <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Afenyo, Mawuli; Khan, Faisal; Veitch, Brian; Yang, Ming</p> <p>2016-06-15</p> <p>This paper presents a model of oil weathering and transport in <span class="hlt">sea</span> <span class="hlt">ice</span>. It contains a model formulation and scenario simulation to test the proposed model. The model formulation is based on state-of-the-art models for individual weathering and transport processes. The approach incorporates the dependency of weathering and transport processes on each other, as well as their simultaneous occurrence after an oil spill in <span class="hlt">sea</span> <span class="hlt">ice</span>. The model is calibrated with available experimental data. The experimental data and model prediction show close agreement. A sensitivity analysis is conducted to determine the most sensitive parameters in the model. The model is useful for contingency planning of a potential oil spill in <span class="hlt">sea</span> <span class="hlt">ice</span>. It is suitable for coupling with a level IV fugacity model, to estimate the concentration and persistence of hydrocarbons in air, <span class="hlt">ice</span>, water and sediments for risk assessment purposes. PMID:27130467</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70040743','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70040743"><span id="translatedtitle">Walrus areas of use in the Chukchi <span class="hlt">Sea</span> during sparse <span class="hlt">sea</span> <span class="hlt">ice</span> cover</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jay, Chadwick V.; Fischbach, Anthony S.; Kochnev, Anatoly A.</p> <p>2012-01-01</p> <p>The Pacific walrus Odobenus rosmarus divergens feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering <span class="hlt">Seas</span> and rests on <span class="hlt">sea</span> <span class="hlt">ice</span> between foraging trips. With climate warming, <span class="hlt">ice</span>-free periods in the Chukchi <span class="hlt">Sea</span> have increased and are projected to increase further in frequency and duration. We radio-tracked walruses to estimate areas of walrus foraging and occupancy in the Chukchi <span class="hlt">Sea</span> from June to November of 2008 to 2011, years when <span class="hlt">sea</span> <span class="hlt">ice</span> was sparse over the continental shelf in comparison to historical records. The earlier and more extensive <span class="hlt">sea</span> <span class="hlt">ice</span> retreat in June to September, and delayed freeze-up of <span class="hlt">sea</span> <span class="hlt">ice</span> in October to November, created conditions for walruses to arrive earlier and stay later in the Chukchi <span class="hlt">Sea</span> than in the past. The lack of <span class="hlt">sea</span> <span class="hlt">ice</span> over the continental shelf from September to October caused walruses to forage in nearshore areas instead of offshore areas as in the past. Walruses did not frequent the deep waters of the Arctic Basin when <span class="hlt">sea</span> <span class="hlt">ice</span> retreated off the shelf. Walruses foraged in most areas they occupied, and areas of concentrated foraging generally corresponded to regions of high benthic biomass, such as in the northeastern (Hanna Shoal) and southwestern Chukchi <span class="hlt">Sea</span>. A notable exception was the occurrence of concentrated foraging in a nearshore area of northwestern Alaska that is apparently depauperate in walrus prey. With increasing <span class="hlt">sea</span> <span class="hlt">ice</span> loss, it is likely that walruses will increase their use of coastal haul-outs and nearshore foraging areas, with consequences to the population that are yet to be understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70159860','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70159860"><span id="translatedtitle">Increased land use by Chukchi <span class="hlt">Sea</span> polar bears in relation to changing <span class="hlt">sea</span> <span class="hlt">ice</span> conditions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Rode, Karyn D.; Wilson, Ryan R.; Regehr, Eric V.; St. Martin, Michelle; Douglas, David; Olson, Jay</p> <p>2015-01-01</p> <p>Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their <span class="hlt">sea</span> <span class="hlt">ice</span> habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi <span class="hlt">Sea</span> between two periods (1986–1995 and 2008–2013) when substantial summer <span class="hlt">sea-ice</span> loss occurred. In both time periods, polar bears predominantly occupied <span class="hlt">sea-ice</span>, although land was used during the summer <span class="hlt">sea-ice</span> retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi <span class="hlt">Sea</span> polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of <span class="hlt">sea</span> <span class="hlt">ice</span> retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to <span class="hlt">sea-ice</span> loss. Implications of increased land use for Chukchi <span class="hlt">Sea</span> polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to <span class="hlt">sea</span> <span class="hlt">ice</span> loss. However, projections of continued <span class="hlt">sea</span> <span class="hlt">ice</span> loss suggest that polar bears in the Chukchi <span class="hlt">Sea</span> and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26580809','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26580809"><span id="translatedtitle">Increased Land Use by Chukchi <span class="hlt">Sea</span> Polar Bears in Relation to Changing <span class="hlt">Sea</span> <span class="hlt">Ice</span> Conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rode, Karyn D; Wilson, Ryan R; Regehr, Eric V; St Martin, Michelle; Douglas, David C; Olson, Jay</p> <p>2015-01-01</p> <p>Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their <span class="hlt">sea</span> <span class="hlt">ice</span> habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi <span class="hlt">Sea</span> between two periods (1986-1995 and 2008-2013) when substantial summer <span class="hlt">sea-ice</span> loss occurred. In both time periods, polar bears predominantly occupied <span class="hlt">sea-ice</span>, although land was used during the summer <span class="hlt">sea-ice</span> retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi <span class="hlt">Sea</span> polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of <span class="hlt">sea</span> <span class="hlt">ice</span> retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to <span class="hlt">sea-ice</span> loss. Implications of increased land use for Chukchi <span class="hlt">Sea</span> polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to <span class="hlt">sea</span> <span class="hlt">ice</span> loss. However, projections of continued <span class="hlt">sea</span> <span class="hlt">ice</span> loss suggest that polar bears in the Chukchi <span class="hlt">Sea</span> and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions. PMID:26580809</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4651550','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4651550"><span id="translatedtitle">Increased Land Use by Chukchi <span class="hlt">Sea</span> Polar Bears in Relation to Changing <span class="hlt">Sea</span> <span class="hlt">Ice</span> Conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rode, Karyn D.; Wilson, Ryan R.; Regehr, Eric V.; St. Martin, Michelle; Douglas, David C.; Olson, Jay</p> <p>2015-01-01</p> <p>Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their <span class="hlt">sea</span> <span class="hlt">ice</span> habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi <span class="hlt">Sea</span> between two periods (1986–1995 and 2008–2013) when substantial summer <span class="hlt">sea-ice</span> loss occurred. In both time periods, polar bears predominantly occupied <span class="hlt">sea-ice</span>, although land was used during the summer <span class="hlt">sea-ice</span> retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi <span class="hlt">Sea</span> polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of <span class="hlt">sea</span> <span class="hlt">ice</span> retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to <span class="hlt">sea-ice</span> loss. Implications of increased land use for Chukchi <span class="hlt">Sea</span> polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to <span class="hlt">sea</span> <span class="hlt">ice</span> loss. However, projections of continued <span class="hlt">sea</span> <span class="hlt">ice</span> loss suggest that polar bears in the Chukchi <span class="hlt">Sea</span> and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions. PMID:26580809</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811757R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811757R&link_type=ABSTRACT"><span id="translatedtitle">Melt ponds and marginal <span class="hlt">ice</span> zone from new algorithm of <span class="hlt">sea</span> <span class="hlt">ice</span> concentration retrieval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Repina, Irina; Tikhonov, Vasiliy; Komarova, Nataliia; Raev, Mikhail; Sharkov, Evgeniy</p> <p>2016-04-01</p> <p>Studies of spatial and temporal properties of <span class="hlt">sea</span> <span class="hlt">ice</span> distribution in polar regions help to monitor global environmental changes and reveal their natural and anthropogenic factors, as well as make forecasts of weather, marine transportation and fishing conditions, assess perspectives of mineral mining on the continental shelf, etc. Contact methods of observation are often insufficient to meet the goals, very complicated technically and organizationally and not always safe for people involved. Remote sensing techniques are believed to be the best alternative. Its include monitoring of polar regions by means of passive microwave sensing with the aim to determine spatial distribution, types, thickness and snow cover of <span class="hlt">ice</span>. However, the algorithms employed today to retrieve <span class="hlt">sea</span> <span class="hlt">ice</span> characteristics from passive microwave sensing data for different reasons give significant errors, especially in summer period and also near <span class="hlt">ice</span> edges and in cases of open <span class="hlt">ice</span>. A new algorithm of <span class="hlt">sea</span> <span class="hlt">ice</span> concentration retrieval in polar regions from satellite microwave radiometry data is discussed. Beside estimating <span class="hlt">sea</span> <span class="hlt">ice</span> concentration, the algorithm makes it possible to indicate <span class="hlt">ice</span> areas with melting snow and melt ponds. Melt ponds are an important element of the Arctic climate system. Covering up to 50% of the surface of drifting <span class="hlt">ice</span> in summer, they are characterized by low albedo values and absorb several times more incident shortwave radiation than the rest of the snow and <span class="hlt">ice</span> cover. The change of melt ponds area in summer period 1987-2015 is investigated. The marginal <span class="hlt">ice</span> zone (MIZ) is defined as the area where open ocean processes, including specifically ocean waves, alter significantly the dynamical properties of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover. Ocean wave fields comprise short waves generated locally and swell propagating from the large ocean basins. Depending on factors like wind direction and ocean currents, it may consist of anything from isolated, small and large <span class="hlt">ice</span> floes drifting over a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C41D0429L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C41D0429L"><span id="translatedtitle">Multiscale Observation System for <span class="hlt">Sea</span> <span class="hlt">Ice</span> Drift and Deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lensu, M.; Haapala, J. J.; Heiler, I.; Karvonen, J.; Suominen, M.</p> <p>2011-12-01</p> <p>The drift and deformation of <span class="hlt">sea</span> <span class="hlt">ice</span> cover is most commonly followed from successive SAR images. The time interval between the images is seldom less than one day which provides rather crude approximation of the motion fields as <span class="hlt">ice</span> can move tens of kilometers per day. This is particulary so from the viewpoint of operative services, seeking to provide real time information for <span class="hlt">ice</span> navigating ships and other end users, as leads are closed and opened or ridge fields created in time scales of one hour or less. The <span class="hlt">ice</span> forecast models are in a need of better temporal resolution for <span class="hlt">ice</span> motion data as well. We present experiences from a multiscale monitoring system set up to the Bay of Bothnia, the northernmost basin of the Baltic <span class="hlt">Sea</span>. The basin generates difficult <span class="hlt">ice</span> conditions every winter while the ports are kept open with the help of an icebreaker fleet. The key addition to SAR imagery is the use of coastal radars for the monitoring of coastal <span class="hlt">ice</span> fields. An independent server is used to tap the radar signal and process it to suit <span class="hlt">ice</span> monitoring purposes. This is done without interfering the basic use of the radars, the ship traffic monitoring. About 20 images per minute are captured and sent to the headquarters for motion field extraction, website animation and distribution. This provides very detailed real time picture of the <span class="hlt">ice</span> movement and deformation within 20 km range. The real time movements are followed in addition with <span class="hlt">ice</span> drifter arrays, and using AIS ship identification data, from which the translation of ship cannels due to <span class="hlt">ice</span> drift can be found out. To the operative setup is associated an extensive research effort that uses the data for <span class="hlt">ice</span> drift model enhancement. The Baltic <span class="hlt">ice</span> models seek to forecast conditions relevant to ship traffic, especilly hazardous ones like severe <span class="hlt">ice</span> compression. The main missing link here is downscaling, or the relation of local scale <span class="hlt">ice</span> dynamics and kinematics to the <span class="hlt">ice</span> model scale behaviour. The data flow when</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060039120&hterms=Climate+change+arctic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DClimate%2Bchange%2Barctic','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060039120&hterms=Climate+change+arctic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DClimate%2Bchange%2Barctic"><span id="translatedtitle">(abstract) Examining <span class="hlt">Sea</span> <span class="hlt">Ice</span> SAR Signatures in the Arctic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Holt, Benjamin</p> <p>1993-01-01</p> <p>This research examines the seasonal changes of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the Arctic Basin as it responds to atmospheric and oceanic conditions. Monitoring this process provides a means of determining the onset and extent of the annual seasonal stages, which is thought to be an indicator for detecting climate change in the polar regions. Much of the response of <span class="hlt">sea</span> <span class="hlt">ice</span> to seasonal conditions results in changes in the phase of water (both in the <span class="hlt">ice</span> and snow cover), surface roughness, and internal properties such as air bubbles. Imagery from SAR has proven to be an important tool for revealing these changes since radar backscatter is affected by both surface roughness and dielectric properties of water and salt. The major <span class="hlt">ice</span> types and <span class="hlt">ice</span> features may have unique SAR backscatter signatures because of the inherent variations in surface roughness, salinity, and internal properties in each category.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8769F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8769F"><span id="translatedtitle">Peopling of the high Arctic - induced by <span class="hlt">sea</span> <span class="hlt">ice</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Funder, Svend</p> <p>2010-05-01</p> <p>'We travelled in the winter after the return of daylight and did not go into fixed camp until spring, when the <span class="hlt">ice</span> broke up. There was good hunting on the way, seals, beluga, walrus, bear.' (From Old Merkrusârk's account of his childhood's trek from Baffin Island to Northwest Greenland, told to Knud Rasmussen on Saunders Island in 1904) Five thousand years ago people moving eastwards from Beringia spread over the barrens of the Canadian high Arctic. This was the first of three waves of prehistoric Arctic 'cultures', which eventually reached Greenland. The passage into Greenland has to go through the northernmost and most hostile part of the country with a 5 month Polar night, and to understand this extraordinary example of human behaviour and endurance, it has been customary to invoke a more favourable (warmer) climate. This presentation suggests that land-fast <span class="hlt">sea</span> <span class="hlt">ice</span>, i.e. stationary <span class="hlt">sea</span> <span class="hlt">ice</span> anchored to the coast, is among the most important environmental factors behind the spread of prehistoric polar cultures. The <span class="hlt">ice</span> provides the road for travelling and social communion - and access to the most important source of food, the ocean. In the LongTerm Project (2006 and 2007) we attempted to establish a Holocene record for <span class="hlt">sea</span> <span class="hlt">ice</span> variations along oceanic coasts in northernmost Greenland. Presently the coasts north of 80° N are beleaguered by year-round <span class="hlt">sea</span> <span class="hlt">ice</span> - for ten months this is land-fast <span class="hlt">ice</span>, and only for a period in the stormy autumn months are the coasts exposed to pack-<span class="hlt">ice</span>. This presentation Land-fast <span class="hlt">ice</span> - as opposed to pack-<span class="hlt">ice</span> - is a product of local temperatures, but its duration over the year, and especially into the daylight season, is also conditioned by other factors, notably wind strength. In the geological record we recognize long lasting land-fast <span class="hlt">ice</span> by two absences: absence of traces of wave action (no beach formation), which, however, can also be a result of pack-<span class="hlt">ice</span> along the coast; - and absence of driftwood on the shore (land-fast <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23413190','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23413190"><span id="translatedtitle">Export of algal biomass from the melting Arctic <span class="hlt">sea</span> <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boetius, Antje; Albrecht, Sebastian; Bakker, Karel; Bienhold, Christina; Felden, Janine; Fernández-Méndez, Mar; Hendricks, Stefan; Katlein, Christian; Lalande, Catherine; Krumpen, Thomas; Nicolaus, Marcel; Peeken, Ilka; Rabe, Benjamin; Rogacheva, Antonina; Rybakova, Elena; Somavilla, Raquel; Wenzhöfer, Frank</p> <p>2013-03-22</p> <p>In the Arctic, under-<span class="hlt">ice</span> primary production is limited to summer months and is restricted not only by <span class="hlt">ice</span> thickness and snow cover but also by the stratification of the water column, which constrains nutrient supply for algal growth. Research Vessel Polarstern visited the <span class="hlt">ice</span>-covered eastern-central basins between 82° to 89°N and 30° to 130°E in summer 2012, when Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> declined to a record minimum. During this cruise, we observed a widespread deposition of <span class="hlt">ice</span> algal biomass of on average 9 grams of carbon per square meter to the deep-<span class="hlt">sea</span> floor of the central Arctic basins. Data from this cruise will contribute to assessing the effect of current climate change on Arctic productivity, biodiversity, and ecological function. PMID:23413190</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DSRI..106...97H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DSRI..106...97H"><span id="translatedtitle">Two wind-driven modes of winter <span class="hlt">sea</span> <span class="hlt">ice</span> variability in the Barents <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herbaut, Christophe; Houssais, Marie-Noëlle; Close, Sally; Blaizot, Anne-Cécile</p> <p>2015-12-01</p> <p>The interannual variability of the winter <span class="hlt">sea</span> <span class="hlt">ice</span> area in the Barents <span class="hlt">Sea</span> is investigated using SMMR-SSM/I data and a coupled ocean-<span class="hlt">sea</span> <span class="hlt">ice</span> model over the period 1979-2012. Our analysis reveals that the <span class="hlt">sea</span> <span class="hlt">ice</span> area in the northern and eastern parts of the Barents <span class="hlt">Sea</span> do not covary. This contrast in behavior allows us to associate two distinct modes of variability with these two regions, with the variability of the overall Barents <span class="hlt">Sea</span> <span class="hlt">ice</span> cover being predominantly captured by the northern mode. Both modes show a dominant, near in-phase response to the surface wind, both being associated with different spatial patterns. The northern mode emerges in response to northwesterly wind anomalies which favor the export of <span class="hlt">ice</span> and surface polar water from the Arctic between Svalbard and Franz Josef Land. Atlantic Water temperature anomalies, formed concomitantly with northerly wind anomalies in the vicinity of the Barents <span class="hlt">Sea</span> Opening, also influence the northern mode in the following winter. These temperature anomalies are linked to local convergence of the oceanic heat transport. The delayed influence of the ocean on the <span class="hlt">sea</span> <span class="hlt">ice</span> is found primarily in the northeastern Barents <span class="hlt">Sea</span> and occurs through the re-emergence of the Atlantic water temperature anomalies at the surface in the following fall and winter. An ocean-to-atmosphere feedback initiated by October SST anomalies in the central Barents <span class="hlt">Sea</span> is further identified. This feedback is hypothesized to enhance the <span class="hlt">sea</span> <span class="hlt">ice</span> response in the northern Barents <span class="hlt">Sea</span> by promoting the formation of meridional wind anomalies. In contrast, the eastern mode of variability of the Barents <span class="hlt">Sea</span> <span class="hlt">ice</span> mainly responds to wind anomalies with a strong zonal component, and is less influenced by the Atlantic Water temperature variability than the northern mode. While our results clearly highlight a role of the ocean in the Barents <span class="hlt">Sea</span> <span class="hlt">ice</span> variability, this role appears to be more spatially restricted following the sudden northward retreat of the <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C41A0683N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C41A0683N&link_type=ABSTRACT"><span id="translatedtitle">The Impact of Snow and <span class="hlt">Ice</span> Morphology on Radar Altimetric Determination of <span class="hlt">Sea</span> <span class="hlt">Ice</span> Thickness</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newman, T.; Brozena, J. M.; Ball, D.; Liang, R.; Abelev, A.; Gardner, J. M.</p> <p>2015-12-01</p> <p>Observations of the current state of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> indicate a trend towards a younger, thinner and more mobile pack that exhibits significant inter-annual variability. Radar returns from altimeters are impacted by the morphology of snow and <span class="hlt">ice</span> features on the surface as well as the characteristics of radar pulse penetration through the snow pack. Together these contribute to uncertainty in the procedures for deriving <span class="hlt">sea</span> <span class="hlt">ice</span> freeboard from radar altimeter data. We make use of dense lidar grids and airborne snow radar measurements, collected on the <span class="hlt">sea</span> <span class="hlt">ice</span> pack north of Barrow, Alaska by the Naval Research Laboratory in 2014 and 2015, to investigate the effect of <span class="hlt">ice</span> surface morphology on radar altimeter measurements. We quantify the effect of surface morphology using a nested approach that includes forward modeling, snow radar data and a comprehensive set of in situ measurements. Our results allow us to better constrain the altimetric uncertainty resulting from <span class="hlt">ice</span> surface morphology, with respect to <span class="hlt">ice</span> type. This will lead to an enhanced understanding of sources of uncertainty in altimeter-derived <span class="hlt">sea</span> <span class="hlt">ice</span> thickness products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040040106','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040040106"><span id="translatedtitle">The Effects of Snow Depth Forcing on Southern Ocean <span class="hlt">Sea</span> <span class="hlt">Ice</span> Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Powel, Dylan C.; Markus, Thorsten; Stoessel, Achim</p> <p>2003-01-01</p> <p>The spatial and temporal distribution of snow on <span class="hlt">sea</span> <span class="hlt">ice</span> is an important factor for <span class="hlt">sea</span> <span class="hlt">ice</span> and climate models. First, it acts as an efficient insulator between the ocean and the atmosphere, and second, snow is a source of fresh water for altering the already weak Southern Ocean stratification. For the Antarctic, where the <span class="hlt">ice</span> thickness is relatively thin, snow can impact the <span class="hlt">ice</span> thickness in two ways: a) As mentioned above snow on <span class="hlt">sea</span> <span class="hlt">ice</span> reduces the ocean-atmosphere heat flux and thus reduces freezing at the base of the <span class="hlt">ice</span> flows; b) a heavy snow load can suppress the <span class="hlt">ice</span> below <span class="hlt">sea</span> level which causes flooding and, with subsequent freezing, a thickening of the <span class="hlt">sea</span> <span class="hlt">ice</span> (snow-to-<span class="hlt">ice</span> conversion). In this paper, we compare different snow fall paramterizations (incl. the incorporation of satellite-derived snow depth) and study the effect on the <span class="hlt">sea</span> <span class="hlt">ice</span> using a <span class="hlt">sea</span> <span class="hlt">ice</span> model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.9702P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.9702P&link_type=ABSTRACT"><span id="translatedtitle">High resolution Holocene <span class="hlt">sea</span> <span class="hlt">ice</span> records from Herald Canyon, Chukchi <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pearce, Christof; Jakobsson, Martin; O'Regan, Matt; Rattray, Jayne; Barrientos, Natalia; Muchitiello, Francesco; Smittenburg, Rienk; Cronin, Tom; Coxall, Helen; Semiletov, Igor</p> <p>2016-04-01</p> <p>Arctic Ocean <span class="hlt">sea</span> <span class="hlt">ice</span> plays a critical role in the Earth's climate system because of the positive <span class="hlt">ice</span>-albedo feedback mechanisms as well as its control on ocean-atmospheric heat exchange and potential influence on the thermohaline circulation. Key to improving our understanding of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover and its reaction to external forcing is the reconstruction of past variability through paleo-records such as marine sediment cores. Although the observed recent <span class="hlt">sea</span> <span class="hlt">ice</span> loss seems to be the strongest of the last millennia, it is still uncertain whether the shift from perennial to seasonal <span class="hlt">ice</span> cover expected for the near future was unprecedented during the current interglacial. High resolution <span class="hlt">sea</span> <span class="hlt">ice</span> reconstructions from the Arctic Ocean are rare, and specifically records from the Russian Arctic are underrepresented. In this study, we present results from marine sediment cores from the Herald Canyon in the East Siberian <span class="hlt">Sea</span>. The area is one of the major conduits of Pacific water entering the Arctic Ocean basin from the Bering Strait and is thus an ideal place to study past variability of the inflow of these nutrient rich waters. Radiocarbon dating of mollusks indicates very high sedimentation rates at the coring sites which allowed for analyses at centennial resolution up to decadal resolution in the late Holocene. Core samples were analyzed for the biomarker IP25, which is produced by diatoms living in <span class="hlt">sea</span> <span class="hlt">ice</span> and is used as a proxy of past seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> concentrations. Preliminary results indicate the presence of seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> during the entire Late Holocene and show a significant increase of <span class="hlt">sea</span> <span class="hlt">ice</span> concentrations during the last millennia.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C43A0776P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.C43A0776P&link_type=ABSTRACT"><span id="translatedtitle">High resolution Holocene <span class="hlt">sea</span> <span class="hlt">ice</span> records from Herald Canyon, East Siberian <span class="hlt">Sea</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pearce, C.; Rattray, J.; Jakobsson, M.; Barrientos, N.; Muschitiello, F.; Smittenberg, R.; O'Regan, M.; Coxall, H.</p> <p>2015-12-01</p> <p>Arctic Ocean <span class="hlt">sea</span> <span class="hlt">ice</span> plays a critical role in the Earth's climate system because of the positive <span class="hlt">ice</span>-albedo feedback mechanisms as well as its control on ocean-atmospheric heat exchange and potential influence on the thermohaline circulation. Key to improving our understanding of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover and its reaction to external forcing is the reconstruction of past variability through paleo-records such as marine sediment cores. Although the observed recent <span class="hlt">sea</span> <span class="hlt">ice</span> loss seems to be the strongest of the last millennia, it is still uncertain whether the shift from perennial to seasonal <span class="hlt">ice</span> cover expected for the near future was unprecedented during the current interglacial. High resolution <span class="hlt">sea</span> <span class="hlt">ice</span> reconstructions from the Arctic Ocean are rare, and specifically records from the Russian Arctic are underrepresented. In this study, we present results from marine sediment cores from the Herald Canyon in the East Siberian <span class="hlt">Sea</span>. The area is one of the major conduits of Pacific water entering the Arctic Ocean basin from the Bering Strait and is thus an ideal place to study past variability of the inflow of these nutrient rich waters. Radiocarbon dating of mollusks indicates very high sedimentation rates at the coring sites which allowed for analyses at centennial resolution up to decadal resolution in the late Holocene. Core samples were analyzed for the biomarker IP25, which is produced by diatoms living in <span class="hlt">sea</span> <span class="hlt">ice</span> and is used as a proxy of past seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> concentrations. Preliminary results indicate the presence of seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> during the entire Late Holocene and show a significant increase of <span class="hlt">sea</span> <span class="hlt">ice</span> concentrations during the last millennia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730020518','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730020518"><span id="translatedtitle"><span class="hlt">Sea-ice</span> and surface water circulation, Alaskan continental shelf</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wright, F. F.; Sharma, G. D.; Burns, J. J. (Principal Investigator)</p> <p>1973-01-01</p> <p>The author has identified the following significant results. Over 1500 water samples from surface and from standard hydrographic depths were collected during June and July 1973 from Bering <span class="hlt">Sea</span> and Gulf of Alaska. The measurement of temperature, salinity, and productivity indicated that various distinct water masses cover the Bering <span class="hlt">Sea</span> Shelf. The suspended load in surface waters will be correlated with the ERTS-1 imagery as it becomes available to delineate the surface water circulation. The movement of <span class="hlt">ice</span> floes in the Bering Strait and Bering <span class="hlt">Sea</span> indicated that movement of <span class="hlt">ice</span> varies considerably and may depend on wind stress as well as ocean currents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.431..127B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.431..127B"><span id="translatedtitle">Identification of paleo Arctic winter <span class="hlt">sea</span> <span class="hlt">ice</span> limits and the marginal <span class="hlt">ice</span> zone: Optimised biomarker-based reconstructions of late Quaternary Arctic <span class="hlt">sea</span> <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belt, Simon T.; Cabedo-Sanz, Patricia; Smik, Lukas; Navarro-Rodriguez, Alba; Berben, Sarah M. P.; Knies, Jochen; Husum, Katrine</p> <p>2015-12-01</p> <p>Analysis of >100 surface sediments from across the Barents <span class="hlt">Sea</span> has shown that the relative abundances of the mono-unsaturated <span class="hlt">sea</span> <span class="hlt">ice</span> diatom-derived biomarker IP25 and a tri-unsaturated highly branched isoprenoid (HBI) lipid (HBI III) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> edge. Thus, while IP25 is generally limited to locations experiencing seasonal <span class="hlt">sea</span> <span class="hlt">ice</span>, with higher abundances found for locations with longer periods of <span class="hlt">ice</span> cover, HBI III is found in sediments from all sampling locations, but is significantly enhanced in sediments within the vicinity of the retreating <span class="hlt">sea</span> <span class="hlt">ice</span> edge or marginal <span class="hlt">ice</span> zone (MIZ). The response of HBI III to this well-defined <span class="hlt">sea</span> <span class="hlt">ice</span> scenario also appears to be more selective than that of the more generic phytoplankton biomarker, brassicasterol. The potential for the combined analysis of IP25 and HBI III to provide more detailed assessments of past <span class="hlt">sea</span> <span class="hlt">ice</span> conditions than IP25 alone has been investigated by quantifying both biomarkers in three marine downcore records from locations with contrasting modern <span class="hlt">sea</span> <span class="hlt">ice</span> settings. For sediment cores from the western Barents <span class="hlt">Sea</span> (intermittent seasonal <span class="hlt">sea</span> <span class="hlt">ice</span>) and the northern Norwegian <span class="hlt">Sea</span> (<span class="hlt">ice</span>-free), high IP25 and low HBI III during the Younger Dryas (ca. 12.9-11.9 cal. kyr BP) is consistent with extensive <span class="hlt">sea</span> cover, with relatively short periods of <span class="hlt">ice</span>-free conditions resulting from late summer retreat. Towards the end of the YD (ca. 11.9-11.5 cal. kyr BP), a general amelioration of conditions resulted in a near winter maximum <span class="hlt">ice</span> edge scenario for both locations, although this was somewhat variable, and the eventual transition to predominantly <span class="hlt">ice</span>-free conditions was later for the western Barents <span class="hlt">Sea</span> site (ca. 9.9 cal. kyr BP) compared to NW Norway (ca. 11.5 cal. kyr BP). For both locations, coeval elevated HBI III (but absent IP25) potentially provides further evidence for increased Atlantic Water inflow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011892','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011892"><span id="translatedtitle">Observations of Recent Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and <span class="hlt">Ice</span> Production</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.</p> <p>2011-01-01</p> <p>Using recently developed techniques we estimate snow and <span class="hlt">sea</span> <span class="hlt">ice</span> thickness distributions for the Arctic basin through the combination of freeboard data from the <span class="hlt">Ice</span>, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic <span class="hlt">sea</span> <span class="hlt">ice</span> model to calculate ocean-atmosphere heat exchange and <span class="hlt">ice</span> volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and <span class="hlt">ice</span> growth rates are in agreement with previous observations over multiyear <span class="hlt">ice</span>. In this study, we calculate heat fluxes and <span class="hlt">ice</span> growth rates for the full distribution of <span class="hlt">ice</span> thicknesses covering the Arctic basin and determine the impact of <span class="hlt">ice</span> thickness change on the calculated values. Thinning of the <span class="hlt">sea</span> <span class="hlt">ice</span> is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in <span class="hlt">sea</span> <span class="hlt">ice</span> thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in <span class="hlt">ice</span> thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of <span class="hlt">sea</span> <span class="hlt">ice</span>. The anomalously low <span class="hlt">sea</span> <span class="hlt">ice</span> coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that <span class="hlt">sea</span> <span class="hlt">ice</span> losses are now playing a role in increasing surface air temperatures in the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070016598&hterms=ice+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dice%2Bmelt','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070016598&hterms=ice+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dice%2Bmelt"><span id="translatedtitle">Observational Evidence of a Hemispheric-wide <span class="hlt">Ice</span>-ocean Albedo Feedback Effect on Antarctic <span class="hlt">Sea-ice</span> Decay</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nihashi, Sohey; Cavalieri, Donald J.</p> <p>2007-01-01</p> <p>The effect of <span class="hlt">ice</span>-ocean albedo feedback (a kind of <span class="hlt">ice</span>-albedo feedback) on <span class="hlt">sea-ice</span> decay is demonstrated over the Antarctic <span class="hlt">sea-ice</span> zone from an analysis of satellite-derived hemispheric <span class="hlt">sea</span> <span class="hlt">ice</span> concentration and European Centre for Medium-Range Weather Forecasts (ERA-40) atmospheric data for the period 1979-2001. <span class="hlt">Sea</span> <span class="hlt">ice</span> concentration in December (time of most active melt) correlates better with the meridional component of the wind-forced <span class="hlt">ice</span> drift (MID) in November (beginning of the melt season) than the MID in December. This 1 month lagged correlation is observed in most of the Antarctic <span class="hlt">sea-ice</span> covered ocean. Daily time series of <span class="hlt">ice</span> , concentration show that the <span class="hlt">ice</span> concentration anomaly increases toward the time of maximum <span class="hlt">sea-ice</span> melt. These findings can be explained by the following positive feedback effect: once <span class="hlt">ice</span> concentration decreases (increases) at the beginning of the melt season, solar heating of the upper ocean through the increased (decreased) open water fraction is enhanced (reduced), leading to (suppressing) a further decrease in <span class="hlt">ice</span> concentration by the oceanic heat. Results obtained fi-om a simple <span class="hlt">ice</span>-ocean coupled model also support our interpretation of the observational results. This positive feedback mechanism explains in part the large interannual variability of the <span class="hlt">sea-ice</span> cover in summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11697256','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11697256"><span id="translatedtitle">Numerical investigations of future <span class="hlt">ice</span> conditions in the Baltic <span class="hlt">Sea</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Haapala, J; Meier, H E; Rinne, J</p> <p>2001-08-01</p> <p>Global climate changes is expected to have an effect on the physical and ecological characteristics of the Baltic <span class="hlt">Sea</span>. Estimates of future climate on the regional scale can be obtained by using either statistical or dynamical downscaling methods of global AOGCM scenario results. In this paper, we use 2 different coupled <span class="hlt">ice</span>-ocean models of the Baltic <span class="hlt">Sea</span> to simulate present and future <span class="hlt">ice</span> conditions around 100 years from present. Two 10-year time slice experiments have been performed using the results of atmospheric climate model simulations as forcing, one representing pre-industrial climate conditions (control simulation), and the other global warming with a 150% increase in CO2 greenhouse gas concentration (scenario simulation). Present-day climatological <span class="hlt">ice</span> conditions and interannual variability are realistically reproduced by the models. The simulated range of the maximum annual <span class="hlt">ice</span> extent in the Baltic in both models together is 180 to 420 x 10(3) km2 in the control simulation and 45 to 270 x 10(3) km2 in the scenario simulation. The range of the maximum annual <span class="hlt">ice</span> thickness is from 32 to 96 cm and from 11 to 60 cm in the control and scenario simulations, respectively. In contrast to earlier estimates, <span class="hlt">sea</span> <span class="hlt">ice</span> is still formed every winter in the Northern Bothnian Bay and in the most Eastern parts of the Gulf of Finland. Overall, the simulated changes of quantities such as <span class="hlt">ice</span> extent and <span class="hlt">ice</span> thickness, as well as their interannual variations are relatively similar in both models, which is remarkable, because the 2 coupled <span class="hlt">ice</span>-ocean model systems have been developed independently. This increases the reliability of future projections of <span class="hlt">ice</span> conditions in the Baltic <span class="hlt">Sea</span>. PMID:11697256</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070034034&hterms=Arctic+Ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Arctic%2BOcean%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070034034&hterms=Arctic+Ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Arctic%2BOcean%2529"><span id="translatedtitle">Contrasts in <span class="hlt">Sea</span> <span class="hlt">Ice</span> Deformation and Production in the Arctic Seasonal and Perennial <span class="hlt">Ice</span> Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kwok, K.</p> <p>2006-01-01</p> <p>Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the <span class="hlt">sea</span> <span class="hlt">ice</span> deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) <span class="hlt">ice</span> zones. <span class="hlt">Ice</span> production is of seasonal <span class="hlt">ice</span> in openings during the winter. Three-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the midwinter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is seen in the SIZ north of coastal Alaska. Both <span class="hlt">ice</span> deformation and production are higher in the SIZ: deformation-related <span class="hlt">ice</span> production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m): this is connected to <span class="hlt">ice</span> strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal <span class="hlt">ice</span> growth in <span class="hlt">ice</span> fractures accounts for approx.25-40% of the total <span class="hlt">ice</span> production of the Arctic Ocean. Uncertainties in these estimates are discussed. By itself, this deformation-<span class="hlt">ice</span> production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on <span class="hlt">ice</span> production in the face of increasing seasonal and thinner/weaker <span class="hlt">ice</span> coverage could be modified by local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and the upwelling of the pynocline associated with increased occurrence of large shear motion in <span class="hlt">sea</span> <span class="hlt">ice</span>. Divergence is shown to be negligibly correlated to cyclonic motion in summer and winter in both <span class="hlt">ice</span> zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ClDy...41.2511T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ClDy...41.2511T"><span id="translatedtitle">Predictability of large interannual Arctic <span class="hlt">sea-ice</span> anomalies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tietsche, Steffen; Notz, Dirk; Jungclaus, Johann H.; Marotzke, Jochem</p> <p>2013-11-01</p> <p>In projections of twenty-first century climate, Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> declines and at the same time exhibits strong interannual anomalies. Here, we investigate the potential to predict these strong <span class="hlt">sea-ice</span> anomalies under a perfect-model assumption, using the Max-Planck-Institute Earth System Model in the same setup as in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We study two cases of strong negative <span class="hlt">sea-ice</span> anomalies: a 5-year-long anomaly for present-day conditions, and a 10-year-long anomaly for conditions projected for the middle of the twenty-first century. We treat these anomalies in the CMIP5 projections as the truth, and use exactly the same model configuration for predictions of this synthetic truth. We start ensemble predictions at different times during the anomalies, considering lagged-perfect and <span class="hlt">sea-ice</span>-assimilated initial conditions. We find that the onset and amplitude of the interannual anomalies are not predictable. However, the further deepening of the anomaly can be predicted for typically 1 year lead time if predictions start after the onset but before the maximal amplitude of the anomaly. The magnitude of an extremely low summer <span class="hlt">sea-ice</span> minimum is hard to predict: the skill of the prediction ensemble is not better than a damped-persistence forecast for lead times of more than a few months, and is not better than a climatology forecast for lead times of two or more years. Predictions of the present-day anomaly are more skillful than predictions of the mid-century anomaly. Predictions using <span class="hlt">sea-ice</span>-assimilated initial conditions are competitive with those using lagged-perfect initial conditions for lead times of a year or less, but yield degraded skill for longer lead times. The results presented here suggest that there is limited prospect of predicting the large interannual <span class="hlt">sea-ice</span> anomalies expected to occur throughout the twenty-first century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70012473','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70012473"><span id="translatedtitle">Arctic continental shelf morphology related to <span class="hlt">sea-ice</span> zonation, Beaufort <span class="hlt">Sea</span>, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Reimnitz, E.; Toimil, L.; Barnes, P.</p> <p>1978-01-01</p> <p>Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of <span class="hlt">ice</span> and <span class="hlt">sea</span>-floor data were used to study <span class="hlt">sea-ice</span> zonation and dynamics and their relation to bottom morphology and geology on the Beaufort <span class="hlt">Sea</span> continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast <span class="hlt">ice</span> and westward-drifting pack <span class="hlt">ice</span> 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-<span class="hlt">ice</span> 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 <span class="hlt">ice</span> seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major <span class="hlt">ice</span>-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of <span class="hlt">ice</span> up to 400 m in the last 25 years. The <span class="hlt">sea</span> floor seaward of these shoals within the stamukhi zone shows high <span class="hlt">ice</span>-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large <span class="hlt">ice</span> ridges and our <span class="hlt">sea</span> 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 <span class="hlt">ice</span> grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to <span class="hlt">sea-ice</span> zonation, <span class="hlt">ice</span> dynamics, and bottom</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JGR...101.8853L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JGR...101.8853L"><span id="translatedtitle">Heat flux through <span class="hlt">sea</span> <span class="hlt">ice</span> in the western Weddell <span class="hlt">Sea</span>: Convective and conductive transfer processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lytle, V. I.; Ackley, S. F.</p> <p>1996-04-01</p> <p>The heat flux through the snow and <span class="hlt">sea</span> <span class="hlt">ice</span> cover and at the <span class="hlt">ice</span>/ocean interface were calculated at five sites in the western Weddell <span class="hlt">Sea</span> during autumn and early winter 1992. The ocean heat flux averaged 7 ± 2 W/m2 from late February to early June, and average <span class="hlt">ice</span>/air heat flux in the second-year floes depended on the depth of the snow cover and ranged from 9 to 17 (±0.8) W/m2. In late February, three of the five sites had an <span class="hlt">ice</span> surface which was depressed below <span class="hlt">sea</span> level, resulting, at two of the sites, in a partially flooded snow cover and a slush layer at the snow/<span class="hlt">ice</span> interface. As this slush layer froze to form snow <span class="hlt">ice</span>, the dense brine which was rejected flowed out through brine drainage channels and was replaced by lower-salinity, nutrient-rich seawater from the ocean upper layer. We estimate that about half of the second-year <span class="hlt">ice</span> in the region was covered with this slush layer early in the winter. As the slush layer froze, over a 2- to 3-week period, the convection within the <span class="hlt">ice</span> transported salt from the <span class="hlt">ice</span> to the upper ocean and increased total heat flux through the overlying <span class="hlt">ice</span> and snow cover. On an area-wide basis, approximately 10 cm of snow <span class="hlt">ice</span> growth occurred within second-year pack <span class="hlt">ice</span>, primarily during a 2- to 3-week period in February and March. This <span class="hlt">ice</span> growth, near the surface of the <span class="hlt">ice</span>, provides a salt flux to the upper ocean equivalent to 5 cm of <span class="hlt">ice</span> growth, despite the thick (about 1 m) <span class="hlt">ice</span> cover, in addition to the <span class="hlt">ice</span> growth in the small (area less than 5%), open water regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015GeoRL..4210704Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015GeoRL..4210704Y&link_type=ABSTRACT"><span id="translatedtitle">Predicted slowdown in the rate of Atlantic <span class="hlt">sea</span> <span class="hlt">ice</span> loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yeager, Stephen G.; Karspeck, Alicia R.; Danabasoglu, Gokhan</p> <p>2015-12-01</p> <p>Coupled climate models initialized from historical climate states and subject to anthropogenic forcings can produce skillful decadal predictions of <span class="hlt">sea</span> surface temperature change in the subpolar North Atlantic. The skill derives largely from initialization, which improves the representation of slow changes in ocean circulation and associated poleward heat transport. We show that skillful predictions of decadal trends in Arctic winter <span class="hlt">sea</span> <span class="hlt">ice</span> extent are also possible, particularly in the Atlantic sector. External radiative forcing contributes to the skill of retrospective decadal <span class="hlt">sea</span> <span class="hlt">ice</span> predictions, but the spatial and temporal accuracy is greatly enhanced by the more realistic representation of ocean heat transport anomalies afforded by initialization. Recent forecasts indicate that a spin-down of the thermohaline circulation that began near the turn of the century will continue, and this will result in near-neutral decadal trends in Atlantic winter <span class="hlt">sea</span> <span class="hlt">ice</span> extent in the coming years, with decadal growth in select regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060036455&hterms=ice+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dice%2Bmelt','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060036455&hterms=ice+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dice%2Bmelt"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">Ice</span> Floe Size Distribution in the Beaufort <span class="hlt">Sea</span> Measured by ERS-1 SAR (abstract)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Holt, B.; Martin, S.</p> <p>1996-01-01</p> <p>Model results indicate that understanding summer heat balance and freshwater balance in the polar oceans requires knowledge of how much goes into vertical and lateral <span class="hlt">sea</span> <span class="hlt">ice</span> melt. In addition to thickness, two of the key <span class="hlt">ice</span> parameters that affect melt rate are <span class="hlt">ice</span> concentration and floe size. Smaller <span class="hlt">ice</span> floes and more open water enables more heat to go into lateral melt preferentially to vertical melt, thereby enhancing warming up the upper ocean and increasing stratification. Using ERS-1 SAR imagery along two areas, one in the Beaufort <span class="hlt">Sea</span> and another in the Chukchi <span class="hlt">Sea</span>, floe size distributions were obtained during the summer period in 1992. Comparisons will be made of floe distributions, together with meteorological and buoy measurements, to examine the differences between an <span class="hlt">ice</span> sink region (Chukchi) and a multiyear <span class="hlt">ice</span> region (Beaufort) in the summer melt process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/981847','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/981847"><span id="translatedtitle">Controls on Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> from first-year and multi-year survival rates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hunke, Jes</p> <p>2009-01-01</p> <p>The recent decrease in Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover has transpired with a significant loss of multi year <span class="hlt">ice</span>. The transition to an Arctic that is populated by thinner first year <span class="hlt">sea</span> <span class="hlt">ice</span> has important implications for future trends in area and volume. Here we develop a reduced model for Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> with which we investigate how the survivability of first year and multi year <span class="hlt">ice</span> control the mean state, variability, and trends in <span class="hlt">ice</span> area and volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1005B"><span id="translatedtitle">Coupled model of INM-IO global ocean model, CICE <span class="hlt">sea</span> <span class="hlt">ice</span> model and SCM OIAS framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayburin, Ruslan; Rashit, Ibrayev; Konstantin, Ushakov; Vladimir, Kalmykov; Gleb, Dyakonov</p> <p>2015-04-01</p> <p>Status of coupled Arctic model of ocean and <span class="hlt">sea</span> <span class="hlt">ice</span> is presented. Model consists of INM IO global ocean component of high resolution, Los <span class="hlt">Alamos</span> National Laboratory CICE <span class="hlt">sea</span> <span class="hlt">ice</span> model and a framework SCM OIAS for the ocean-<span class="hlt">ice</span>-atmosphere-land coupled modeling on massively-parallel architectures. Model is currently under development at the Institute of Numerical Mathematics (INM), Hydrometeorological Center (HMC) and P.P. Shirshov Institute of Oceanology (IO). Model is aimed at modeling of intra-annual variability of hydrodynamics in Arctic and. The computational characteristics of the world ocean-<span class="hlt">sea</span> <span class="hlt">ice</span> coupled model governed by SCM OIAS are presented. The model is parallelized using MPI technologies and currently can use efficiently up to 5000 cores. Details of programming implementation, computational configuration and physical phenomena parametrization are analyzed in terms of intercoupling complex. Results of five year computational experiment of <span class="hlt">sea</span> <span class="hlt">ice</span>, snow and ocean state evolution in Arctic region on tripole grid with horizontal resolution of 3-5 kilometers, closed by atmospheric forcing field from repeating "normal" annual course taken from CORE1 experiment data base are presented and analyzed in terms of the state of vorticity and warm Atlantic water expansion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811112T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811112T"><span id="translatedtitle">Greenland <span class="hlt">ice</span> sheet initiation and Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> coincide with Eocene and Oligocene CO2 changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tripati, Aradhna; Darby, Dennis</p> <p>2016-04-01</p> <p>Earth's modern ocean-climate system is largely defined by the presence of glacial <span class="hlt">ice</span> on landmasses in both hemispheres. Northern Hemisphere <span class="hlt">ice</span> was previously thought to have formed no earlier than the Miocene or Oligocene, about 20-30 million years after the widespread onset of Antarctic glaciation at the Eocene-Oligocene boundary. Controversially, the episodic presence of seasonal Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> and glacial <span class="hlt">ice</span> in the Northern Hemisphere beginning in the early Oligocene to Middle Eocene has been inferred from multiple observations. Here we use precise source determinations based on geochemical measurements of <span class="hlt">ice</span>-rafted debris (IRD) from an ODP core in the Greenland <span class="hlt">Sea</span> (75° N) to constrain glacial <span class="hlt">ice</span> and <span class="hlt">sea</span> <span class="hlt">ice</span>-rafting in the Northern Hemisphere during the middle Eocene through early Oligocene. The chemical fingerprint of 2,334 detrital Fe oxide grains indicates most of these grains are from Greenland with >98% certainty. Thus the coarse IRD in the Greenland <span class="hlt">Sea</span> originates from widespread areas of east Greenland as far south as the Denmark Strait area (~68° N), with additional IRD sources from the circum-Arctic Ocean. This is the first definitive evidence that mid-Eocene IRD in the Greenland <span class="hlt">Sea</span> is from Greenland. Episodic glaciation of different source regions on Greenland is synchronous with times of <span class="hlt">ice</span>-rafting in the western Arctic and ephemeral perennial Arctic <span class="hlt">ice</span> cover. Intervals of bipolar glacial <span class="hlt">ice</span> storage in the middle Eocene through early Oligocene coincide with evidence for periods of reduced CO2, associated with carbon cycle perturbations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4653624','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4653624"><span id="translatedtitle">Additional Arctic observations improve weather and <span class="hlt">sea-ice</span> forecasts for the Northern <span class="hlt">Sea</span> Route</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime</p> <p>2015-01-01</p> <p>During <span class="hlt">ice</span>-free periods, the Northern <span class="hlt">Sea</span> Route (NSR) could be an attractive shipping route. The decline in Arctic <span class="hlt">sea-ice</span> extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of <span class="hlt">sea</span> <span class="hlt">ice</span> could make ship navigation along the NSR difficult. Accurate forecasts of weather and <span class="hlt">sea</span> <span class="hlt">ice</span> are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and <span class="hlt">sea-ice</span> forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The <span class="hlt">sea-ice</span> forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven <span class="hlt">sea-ice</span> advection along the NSR. PMID:26585690</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...516868I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...516868I"><span id="translatedtitle">Additional Arctic observations improve weather and <span class="hlt">sea-ice</span> forecasts for the Northern <span class="hlt">Sea</span> Route</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime</p> <p>2015-11-01</p> <p>During <span class="hlt">ice</span>-free periods, the Northern <span class="hlt">Sea</span> Route (NSR) could be an attractive shipping route. The decline in Arctic <span class="hlt">sea-ice</span> extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of <span class="hlt">sea</span> <span class="hlt">ice</span> could make ship navigation along the NSR difficult. Accurate forecasts of weather and <span class="hlt">sea</span> <span class="hlt">ice</span> are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and <span class="hlt">sea-ice</span> forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The <span class="hlt">sea-ice</span> forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven <span class="hlt">sea-ice</span> advection along the NSR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26585690','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26585690"><span id="translatedtitle">Additional Arctic observations improve weather and <span class="hlt">sea-ice</span> forecasts for the Northern <span class="hlt">Sea</span> Route.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime</p> <p>2015-01-01</p> <p>During <span class="hlt">ice</span>-free periods, the Northern <span class="hlt">Sea</span> Route (NSR) could be an attractive shipping route. The decline in Arctic <span class="hlt">sea-ice</span> extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of <span class="hlt">sea</span> <span class="hlt">ice</span> could make ship navigation along the NSR difficult. Accurate forecasts of weather and <span class="hlt">sea</span> <span class="hlt">ice</span> are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and <span class="hlt">sea-ice</span> forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The <span class="hlt">sea-ice</span> forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven <span class="hlt">sea-ice</span> advection along the NSR. PMID:26585690</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......110D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......110D"><span id="translatedtitle">Alaska shorefast <span class="hlt">ice</span>: Interfacing geophysics with local <span class="hlt">sea</span> <span class="hlt">ice</span> knowledge and use</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Druckenmiller, Matthew L.</p> <p></p> <p>This thesis interfaces geophysical techniques with local and traditional knowledge (LTK) of indigenous <span class="hlt">ice</span> experts to track and evaluate coastal <span class="hlt">sea</span> <span class="hlt">ice</span> conditions over annual and inter-annual timescales. A novel approach is presented for consulting LTK alongside a systematic study of where, when, and how the community of Barrow, Alaska uses the <span class="hlt">ice</span> cover. The goal of this research is to improve our understanding of and abilities to monitor the processes that govern the state and dynamics of shorefast <span class="hlt">sea</span> <span class="hlt">ice</span> in the Chukchi <span class="hlt">Sea</span> and use of <span class="hlt">ice</span> by the community. Shorefast <span class="hlt">ice</span> stability and community strategies for safe hunting provide a framework for data collection and knowledge sharing that reveals how nuanced observations by Inupiat <span class="hlt">ice</span> experts relate to identifying hazards. In particular, shorefast <span class="hlt">ice</span> break-out events represent a significant threat to the lives of hunters. Fault tree analysis (FTA) is used to combine local and time-specific observations of <span class="hlt">ice</span> conditions by both geophysical instruments and local experts, and to evaluate how <span class="hlt">ice</span> features, atmospheric and oceanic forces, and local to regional processes interact to cause break-out events. Each year, the Barrow community builds trails across shorefast <span class="hlt">ice</span> for use during the spring whaling season. In collaboration with hunters, a systematic multi-year survey (2007--2011) was performed to map these trails and measure <span class="hlt">ice</span> thickness along them. Relationships between <span class="hlt">ice</span> conditions and hunter strategies that guide trail placement and risk assessment are explored. In addition, trail surveys provide a meaningful and consistent approach to monitoring the thickness distribution of shorefast <span class="hlt">ice</span>, while establishing a baseline for assessing future environmental change and potential impacts to the community. Coastal communities in the region have proven highly adaptive in their ability to safely and successfully hunt from <span class="hlt">sea</span> <span class="hlt">ice</span> over the last 30 years as significant changes have been observed in the <span class="hlt">ice</span> zone</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020060091','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020060091"><span id="translatedtitle">A Rapidly Declining Arctic Perennial <span class="hlt">Sea</span> <span class="hlt">Ice</span> Cover</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Koblinsky, Chester J. (Technical Monitor)</p> <p>2002-01-01</p> <p>The perennial <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the Arctic is shown to be declining at -8.9 plus or minus 2.0% per decade, using 22 years of satellite data. A sustained decline at this rate would mean the disappearance of the multiyear <span class="hlt">ice</span> cover during this century and drastic changes in the seasonal characteristics of the Arctic <span class="hlt">ice</span> cover. An apparent increase in the fraction of second year <span class="hlt">ice</span> in the 1990s is also inferred suggesting an overall thinning of the <span class="hlt">ice</span> cover while co-registered satellite surface temperatures show a warming trend of 0.8 plus or minus 0.6 K per decade in summer and a good correlation with the perennial <span class="hlt">ice</span> data.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17363664','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17363664"><span id="translatedtitle">Perspectives on the Arctic's shrinking <span class="hlt">sea-ice</span> cover.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Serreze, Mark C; Holland, Marika M; Stroeve, Julienne</p> <p>2007-03-16</p> <p>Linear trends in arctic <span class="hlt">sea-ice</span> extent over the period 1979 to 2006 are negative in every month. This <span class="hlt">ice</span> loss is best viewed as a combination of strong natural variability in the coupled <span class="hlt">ice</span>-ocean-atmosphere system and a growing radiative forcing associated with rising concentrations of atmospheric greenhouse gases, the latter supported by evidence of qualitative consistency between observed trends and those simulated by climate models over the same period. Although the large scatter between individual model simulations leads to much uncertainty as to when a seasonally <span class="hlt">ice</span>-free Arctic Ocean might be realized, this transition to a new arctic state may be rapid once the <span class="hlt">ice</span> thins to a more vulnerable state. Loss of the <span class="hlt">ice</span> cover is expected to affect the Arctic's freshwater system and surface energy budget and could be manifested in middle latitudes as altered patterns of atmospheric circulation and precipitation. PMID:17363664</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..33.4501W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..33.4501W"><span id="translatedtitle">A new view of the underside of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wadhams, P.; Wilkinson, J. P.; McPhail, S. D.</p> <p>2006-02-01</p> <p>The Autosub-II autonomous underwater vehicle (AUV), operating off NE Greenland in August 2004, obtained the first successful swath sonar measurements under <span class="hlt">sea</span> <span class="hlt">ice</span>, showing in unprecedented detail the three-dimensional nature of the under-<span class="hlt">ice</span> surface. The vehicle, operated from RRS James Clark Ross, obtained more than 450 track-km of under-<span class="hlt">ice</span> multibeam data. We show imagery from first- and multiyear <span class="hlt">ice</span>, including young ridges, old hummocks and undeformed melting <span class="hlt">ice</span>. In addition, we show how the combination of other on-board sensors enabled the vehicle to obtain detailed information about seabed topography, water structure and current fields in an exploratory mode within a region which is seldom visited because of difficult year-round <span class="hlt">ice</span> conditions. This included identification of a new current regime in the Norske Trough.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.C43A0579L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.C43A0579L&link_type=ABSTRACT"><span id="translatedtitle">Microstructural Considerations of Transporting <span class="hlt">Sea</span> <span class="hlt">Ice</span> Samples from Polar Regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lieb-Lappen, R.; Obbard, R. W.</p> <p>2012-12-01</p> <p>High latitude regions are at the forefront of climate change research as these regions have and will experience the greatest impact due to changing environmental conditions (e.g. Antarctic and recent Arctic stratospheric ozone holes, large temperature increases on the Antarctic Peninsula, changes in the extent and age of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span>). One of the major challenges of polar scientific research is the preservation of frozen <span class="hlt">sea</span> <span class="hlt">ice</span> samples during their transport back to the laboratory and subsequent storage. Small fluctuations in temperature have been shown to have a significant effect on the microstructure of snow and <span class="hlt">ice</span> samples. This is especially true for <span class="hlt">sea</span> <span class="hlt">ice</span> specimens where transport and storage temperatures are often only slightly below the eutectic point for its different constituents (i.e. salts). Furthermore, <span class="hlt">sea</span> <span class="hlt">ice</span> can have a 30 deg C in situ vertical temperature gradient that is lost during transport and storage. <span class="hlt">Sea</span> <span class="hlt">ice</span> plays a critical role in mediating the exchange of heat, gases, and chemical species across the ocean-atmosphere interface. The kinetics of these exchanges is highly dependent upon the brine channel microstructure, which is strongly coupled to temperature. To determine the degree of microstructural variation between samples shipped at different temperatures, ten samples of a single <span class="hlt">sea</span> <span class="hlt">ice</span> core collected in March 2012 were transported from Barrow, Alaska to Hanover, NH using two common techniques: with blue <span class="hlt">ice</span> packs enclosed in a Styrofoam box (~ -25 deg C) and in a dry liquid nitrogen cryoshipper (~ -182 deg C). In addition, snow lying on the <span class="hlt">sea</span> <span class="hlt">ice</span> and blowing snow samples were collected and shipped via both techniques. All samples were then stored for analysis in a cold room maintained at ~ -33 deg C. The microstructure of both sets of samples was analyzed using x-ray micro-computed tomography (μ-CT), with samples on a Peltier cold stage to maintain a scanning temperature of -20 deg C. We compare <span class="hlt">sea</span> <span class="hlt">ice</span> porosity and brine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070010003&hterms=Arctic+Ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Arctic%2BOcean%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070010003&hterms=Arctic+Ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Arctic%2BOcean%2529"><span id="translatedtitle">Contrasts in <span class="hlt">Sea</span> <span class="hlt">Ice</span> Formation and Production in the Arctic Seasonal and Perennial <span class="hlt">Ice</span> Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kwok, R.</p> <p>2006-01-01</p> <p>Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the <span class="hlt">sea</span> <span class="hlt">ice</span> deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) <span class="hlt">ice</span> zones. <span class="hlt">Ice</span> production is of seasonal <span class="hlt">ice</span> in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both <span class="hlt">ice</span> deformation and production are higher in the SIZ: deformation-related <span class="hlt">ice</span> production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to <span class="hlt">ice</span> strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal <span class="hlt">ice</span> growth in <span class="hlt">ice</span> fractures accounts for approx.25-40% of the total <span class="hlt">ice</span> production of the Arctic Ocean. By itself, this deformation-<span class="hlt">ice</span> production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on <span class="hlt">ice</span> production in the face of increasing seasonal and thinner/weaker <span class="hlt">ice</span> coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in <span class="hlt">sea</span> <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013478','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013478"><span id="translatedtitle">Variability and Anomalous Trends in the Global <span class="hlt">Sea</span> <span class="hlt">Ice</span> Cover</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.</p> <p>2012-01-01</p> <p>The advent of satellite data came fortuitously at a time when the global <span class="hlt">sea</span> <span class="hlt">ice</span> cover has been changing rapidly and new techniques are needed to accurately assess the true state and characteristics of the global <span class="hlt">sea</span> <span class="hlt">ice</span> cover. The extent of the <span class="hlt">sea</span> <span class="hlt">ice</span> in the Northern Hemisphere has been declining by about -4% per decade for the period 1979 to 2011 but for the period from 1996 to 2010, the rate of decline became even more negative at -8% per decade, indicating an acceleration in the decline. More intriguing is the drastically declining perennial <span class="hlt">sea</span> <span class="hlt">ice</span> area, which is the <span class="hlt">ice</span> that survives the summer melt and observed to be retreating at the rate of -14% per decade during the 1979 to 2012 period. Although a slight recovery occurred in the last three years from an abrupt decline in 2007, the perennial <span class="hlt">ice</span> extent was almost as low as in 2007 in 2011. The multiyear <span class="hlt">ice</span>, which is the thick component of the perennial <span class="hlt">ice</span> and regarded as the mainstay of the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover is declining at an even higher rate of -19% per decade. The more rapid decline of the extent of this thicker <span class="hlt">ice</span> type means that the volume of the <span class="hlt">ice</span> is also declining making the survival of the Arctic <span class="hlt">ice</span> in summer highly questionable. The slight recovery in 2008, 2009 and 2010 for the perennial <span class="hlt">ice</span> in summer was likely associated with an apparent cycle in the time series with a period of about 8 years. Results of analysis of concurrent MODIS and AMSR-E data in summer also provide some evidence of more extensive summer melt and meltponding in 2007 and 2011 than in other years. Meanwhile, the Antarctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover, as observed by the same set of satellite data, is showing an unexpected and counter intuitive increase of about 1 % per decade over the same period. Although a strong decline in <span class="hlt">ice</span> extent is apparent in the Bellingshausen/ Amundsen <span class="hlt">Seas</span> region, such decline is more than compensated by increases in the extent of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the Ross <span class="hlt">Sea</span> region. The results of analysis of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24766483','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24766483"><span id="translatedtitle">Total and methylated mercury in Arctic multiyear <span class="hlt">sea</span> <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beattie, Sarah A; Armstrong, Debbie; Chaulk, Amanda; Comte, Jérôme; Gosselin, Michel; Wang, Feiyue</p> <p>2014-05-20</p> <p>Mercury is one of the primary contaminants of concern in the Arctic marine ecosystem. While considerable efforts have been directed toward understanding mercury cycling in the Arctic, little is known about mercury dynamics within Arctic multiyear <span class="hlt">sea</span> <span class="hlt">ice</span>, which is being rapidly replaced with first-year <span class="hlt">ice</span>. Here we report the first study on the distribution and potential methylation of mercury in Arctic multiyear <span class="hlt">sea</span> <span class="hlt">ice</span>. Based on three multiyear <span class="hlt">ice</span> cores taken from the eastern Beaufort <span class="hlt">Sea</span> and McClure Strait, total mercury concentrations ranged from 0.65 to 60.8 pM in bulk <span class="hlt">ice</span>, with the highest values occurring in the topmost layer (∼40 cm) which is attributed to the dynamics of particulate matter. Methylated mercury concentrations ranged from below the method detection limit (<0.1 pM) to as high as 2.64 pM. The ratio of methylated to total mercury peaked, up to ∼40%, in the mid to bottom sections of the <span class="hlt">ice</span>, suggesting the potential occurrence of in situ mercury methylation. The annual fluxes of total and methylated mercury into the Arctic Ocean via melt of multiyear <span class="hlt">ice</span> are estimated to be 420 and 42 kg yr(-1), respectively, representing an important and changing source of mercury and methylmercury into the Arctic Ocean marine ecosystem. PMID:24766483</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010037608','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010037608"><span id="translatedtitle">Trends in the Length of the Southern Ocean <span class="hlt">Sea</span> <span class="hlt">Ice</span> Season: 1979-1999</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)</p> <p>2001-01-01</p> <p>Satellite data can be used to observe the <span class="hlt">sea</span> <span class="hlt">ice</span> distribution around the continent of Antarctica on a daily basis and hence to determine how many days a year have <span class="hlt">sea</span> <span class="hlt">ice</span> at each location. This has been done for each of the 21 years 1979-1999. Mapping the trends in these data over the 21-year period reveals a detailed pattern of changes in the length of the <span class="hlt">sea</span> <span class="hlt">ice</span> season around Antarctica. Most of the Ross <span class="hlt">Sea</span> <span class="hlt">ice</span> cover has undergone a lengthening of the <span class="hlt">sea</span> <span class="hlt">ice</span> season, whereas most of the Amundsen <span class="hlt">Sea</span> <span class="hlt">ice</span> cover and almost the entire Bellingshausen <span class="hlt">Sea</span> <span class="hlt">ice</span> cover have unde