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Sample records for adjacent sea ice

  1. Pelagic ciliate communities within the Amundsen Sea polynya and adjacent sea ice zone, Antarctica

    NASA Astrophysics Data System (ADS)

    Jiang, Yong; Liu, Qian; Yang, Eun Jin; Wang, Min; Kim, Tae Wan; Cho, Kyoung-Ho; Lee, SangHoon

    2016-01-01

    Polynyas, areas of open water surrounded by sea ice, are sites of intense primary production and ecological hotspots in the Antarctic Ocean. This study determined the spatial variation in communities of pelagic ciliates in an Amundsen Sea polynya (ASP) and adjacent sea ice zones (SIZ) during austral summer from February to March 2012, and the results were compared with biotic and abiotic environmental factors. The species number, abundance and biomass were higher in the ASP than SIZ. Canonical analysis indicated that the communities in the ASP were distinct from those under the sea ice. The pelagic ciliate community structure was closely correlated with environmental variability. Several primary environmental variables, both alone and in combination, were found to affect community spatial patterns. The ciliate biomasses in the ASP and SIZ areas were both significantly correlated with total and nano-Chl a. This analysis of the ciliated microzooplankton communities associated with high primary production provides new insights into the roles of ciliates in biogeochemical cycles in high-latitude polynyas. Additionally, our findings provide detailed data on the composition, distribution, and structure of polynya ciliate communities in the Amundsen Sea.

  2. 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.

  3. 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.

  4. Sea Ice Ecosystems

    NASA Astrophysics Data System (ADS)

    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.

  5. 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.

  6. 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...

  7. 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.

  8. 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 ...

  9. Sea Ice Minimum 2016

    NASA Video Gallery

    This animation shows the evolution of the Arctic sea ice cover from its wintertime maximum extent, which was reached on Mar. 24, 2016, and was the lowest on record for the second year in a row, to ...

  10. 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) ...

  11. 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.

  12. 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.

  13. 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.

  14. Sea Ice and Oceanographic Conditions.

    ERIC Educational Resources Information Center

    Oceanus, 1986

    1986-01-01

    The coastal waters of the Beaufort Sea are covered with ice three-fourths of the year. These waters (during winter) are discussed by considering: consolidation of coastal ice; under-ice water; brine circulation; biological energy; life under the ice (including kelp and larger animals); food chains; and ice break-up. (JN)

  15. 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 ...

  16. Arctic Sea Ice Model Sensitivities

    NASA Astrophysics Data System (ADS)

    Peterson, K. J.; Bochev, P.; Paskaleva, B.

    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. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94-AL85000.

  17. Polar Climate: Arctic sea ice

    USGS Publications Warehouse

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

    2005-01-01

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

  18. Stalactite Growth beneath Sea Ice.

    PubMed

    Paige, R A

    1970-01-01

    Fresh ice stalactites were observed beneath sea ice in Antarctica. They are hollow, tapering, inverted cones having a base diameter between 10 and 20 centimeters and a tip diameter of 4 to 10 centimeters extending downward about 100 centimeters. The stalactites form when dense, chilled brine drains downward from the ice sheet into seawater of norma1 salinity and near-freezing temperature.

  19. 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

  20. Neogene History of Antarctic Sea-ice and Development of the Sea-ice Diatom Community

    NASA Astrophysics Data System (ADS)

    Harwood, D. M.; Bohaty, S. M.; Whitehead, J. M.

    2002-12-01

    Sea-ice plays an important role in the modern Antarctic climate system and in this region's linkage to lower latitude regions. Today, the seasonal sea-ice cover decouples oceanic heat transfer to the atmosphere, which amplifies winter's low temperatures and shifts sources of moisture far to the north. The sea-ice zone is an important site for biological productivity and bottom water formation, through cooling and brine exclusion. The absence of the sea-ice during past and future periods of elevated temperatures would significantly impact the biology, oceanography, glaciology and meteorology of the Antarctic region. A unique diatom assemblage is adapted to life in and around the sea-ice, and serves as an increasingly useful proxy to mark the presence, extent and duration of sea-ice cover. This assemblage dominates Antarctic shelf sediments today and back through most of the Quaternary. The oldest fossil diatom flora with a similar composition and structure to that of the modern sea-ice community was identified in a late Miocene mudstone erratic MB-244C in coastal moraine from McMurdo Sound. This assemblage did not persist through to the present day, and it is absent, or significantly reduced, in numerous marine diatom-bearing strata of late Miocene, Pliocene and Quaternary age, including the upper Miocene McLeod Beds of the Battye Glacier Formation, Prince Charles Mountains, the lower Pliocene Sorsdal Formation in the Vestfold Hills, the Pliocene sediments from the DVDP and CIROS drillcores, and the lower Quaternary carbonate unit in the Cape Roberts Project drillcore CRP-1. The sea-ice diatom community likely persisted in low numbers in interior fjords and basins, adjacent to glacier margins during these times. The history of sea-ice development and fluctuation during the Neogene appears to be complex, with substantial variability in sea-ice cover. Core records are currently insufficient to document the details of this history, and variation in the diatom

  1. 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.

  2. 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, ...

  3. 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...

  4. 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...

  5. Jet formation at the sea ice edge

    NASA Astrophysics Data System (ADS)

    Feltham, D. L.; Heorton, H. D.

    2014-12-01

    The sea ice edge presents a region of many feedback processes between the atmosphere, ocean and sea ice, which are inadequately represented in current climate models. Here we focus on on-ice atmospheric and oceanic flows at the sea ice edge. Mesoscale jet formation due to the Coriolis effect is well understood over sharp changes in surface roughness such as coastlines. This sharp change in surface roughness is experienced by the atmosphere flowing over, and ocean flowing under, a compacted sea ice edge. We have studied a dynamic sea ice edge responding to atmospheric and oceanic jet formation. The shape and strength of atmospheric and oceanic jets during on-ice flows is calculated from existing studies of the sea ice edge and prescribed to idealised models of the sea ice edge. An idealised analytical model of sea ice drift is developed and compared to a sea ice climate model (the CICE model) run on an idealised domain. The response of the CICE model to jet formation is tested at various resolutions. We find that the formation of atmospheric jets during on-ice winds at the sea ice edge increases the wind speed parallel to the sea ice edge and results in the formation of a sea ice edge jet. The modelled sea ice edge jet is in agreement with an observed jet although more observations are needed for validation. The increase in ice drift speed is dependent upon the angle between the ice edge and wind and can result in a 40% increase in ice transport along the sea ice edge. The possibility of oceanic jet formation during on-ice currents and the resultant effect upon the sea ice edge is less conclusive. Observations and climate model data of the polar oceans has been analysed to show areas of likely atmospheric jet formation, with the Fram Strait being of particular interest.

  6. 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.

  7. 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.

  8. 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

  9. 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...

  10. Sea ice structure and biological activity in the Antarctic marginal ice zone

    NASA Astrophysics Data System (ADS)

    Clarke, D. B.; Ackley, S. F.

    1984-03-01

    Ice cores obtained during October-November 1981 from Weddell Sea pack ice were analyzed for physical, chemical, and biological parameters. Frazil ice, which is associated with dynamic, turbulent conditions in the water column, predominated (70%). Both floe thickness and salinity indicate ice which is less than 1 year old. Chemical analyses, particularly with regard to the nutrients, revealed a complex picture. Phosphate values are scattered relative to the dilution curve. Nitrate and silicate values are lower than expected from simple scaling with salinity and suggest diatom growth within the ice. Nitrite values are higher in the ice than in adjacent waters. Frazil ice formation which probably concentrates algal cells from the water column into ice floes results in higher initial chlorophyll a concentrations in the ice than in adjacent waters. This mechanical concentration is further enhanced by subsequent reproduction within the ice. Ice core chlorophyll ranged from 0.09 to 3.8 mg/m3, comparable to values previously reported for this area but significantly lower than values for Antarctic coastal fast ice. The dominance of frazil ice in the Weddell is one of the major differences between this area and others. Consequently, we believe that ice structural conditions significantly influence the biological communities in the ice.

  11. 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...

  12. 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.

  13. 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.

  14. 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…

  15. 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.

  16. 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.

  17. Dynamics of sea ice in the Baltic Sea and applications

    NASA Astrophysics Data System (ADS)

    Leppäranta, M.; Andrejev, O.; Oikkonen, A.

    2009-04-01

    Sea ice forms in the Baltic Sea annually. Coastal and archipelago areas are covered by landfast ice, while further offshore the ice drifts under the influence of winds and currents. The length scale of the Baltic Sea basins is 100 km and the scale of the ice thickness is ½ m, and the characteristics of the ice dynamics are similar to the ice dynamics in the polar seas. The drifting of the ice has major practical implications. First, the navigation conditions are determined by the ice extent, presence of leads and ice pressure, and therefore the dynamical behaviour of ice may cause rapid changes for them. Recent research has focused on ice kinematics scales, evolution of landfast ice zone, and downscaling of pressure from mesoscale models to ship scales. The length scale of dynamics depends on the ice thickness showing up in the stiffness of the ice and expansion of the landfast ice zone. Oil spills are in particular difficult in drift ice conditions, which has led to development of oil spill drift and dispersion models. This is most critical in the Gulf of Finland, a narrow and shallow basin with large oil terminals in the eastern side. The formation of sea ice ridges has important consequences in shallow basins since they ground to scour the bottom and form tie points for the expansion of the landfast ice.

  18. Monitoring Arctic Sea ice using ERTS imagery. [Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

    NASA Technical Reports Server (NTRS)

    Barnes, J. C.; Bowley, C. J.

    1974-01-01

    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 other 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 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft.

  19. 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.

  20. 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.

  1. 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...

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Sea-ice thermodynamics and brine drainage.

    PubMed

    Worster, M Grae; Rees Jones, David W

    2015-07-13

    Significant changes in the state of the Arctic ice cover are occurring. As the summertime extent of sea ice diminishes, the Arctic is increasingly characterized by first-year rather than multi-year ice. It is during the early stages of ice growth that most brine is injected into the oceans, contributing to the buoyancy flux that mediates the thermo-haline circulation. Current operational sea-ice components of climate models often treat brine rejection between sea ice and the ocean similarly to a thermodynamic segregation process, assigning a fixed salinity to the sea ice, typical of multi-year ice. However, brine rejection is a dynamical, buoyancy-driven process and the salinity of sea ice varies significantly during the first growth season. As a result, current operational models may over predict the early brine fluxes from newly formed sea ice, which may have consequences for coupled simulations of the polar oceans. Improvements both in computational power and our understanding of the processes involved have led to the emergence of a new class of sea-ice models that treat brine rejection dynamically and should enhance predictions of the buoyancy forcing of the oceans.

  9. Microbial mercury methylation in Antarctic sea ice.

    PubMed

    Gionfriddo, Caitlin M; Tate, Michael T; Wick, Ryan R; Schultz, Mark B; Zemla, Adam; Thelen, Michael P; Schofield, Robyn; Krabbenhoft, David P; Holt, Kathryn E; Moreau, John W

    2016-01-01

    Atmospheric deposition of mercury onto sea ice and circumpolar sea water provides mercury for microbial methylation, and contributes to the bioaccumulation of the potent neurotoxin methylmercury in the marine food web. Little is known about the abiotic and biotic controls on microbial mercury methylation in polar marine systems. However, mercury methylation is known to occur alongside photochemical and microbial mercury reduction and subsequent volatilization. Here, we combine mercury speciation measurements of total and methylated mercury with metagenomic analysis of whole-community microbial DNA from Antarctic snow, brine, sea ice and sea water to elucidate potential microbially mediated mercury methylation and volatilization pathways in polar marine environments. Our results identify the marine microaerophilic bacterium Nitrospina as a potential mercury methylator within sea ice. Anaerobic bacteria known to methylate mercury were notably absent from sea-ice metagenomes. We propose that Antarctic sea ice can harbour a microbial source of methylmercury in the Southern Ocean. PMID:27670112

  10. 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

  11. 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.

  12. [Reflectance of sea ice in Liaodong Bay].

    PubMed

    Xu, Zhan-tang; Yang, Yue-zhong; Wang, Gui-fen; Cao, Wen-xi; Kong, Xiang-peng

    2010-07-01

    In the present study, the relationships between sea ice albedo and the bidirectional reflectance distribution in Liaodong Bay were investigated. The results indicate that: (1) sea ice albedo alpha(lambda) is closely related to the components of sea ice, the higher the particulate concentration in sea ice surface is, the lower the sea ice albedo alpha(lambda) is. On the contrary, the higher the bubble concentration in sea ice is, the higher sea ice albedo alpha(lambda) is. (2) Sea ice albedo alpha(lambda) is similar to the bidirectional reflectance factor R(f) when the probe locates at nadir. The R(f) would increase with the increase in detector zenith theta, and the correlation between R(f) and the detector azimuth would gradually increase. When the theta is located at solar zenith 63 degrees, the R(f) would reach the maximum, and the strongest correlation is also shown between the R(f) and the detector azimuth. (3) Different types of sea ice would have the different anisotropic reflectance factors.

  13. Microwave remote sensing of sea ice

    NASA Technical Reports Server (NTRS)

    Comiso, J. C.

    1988-01-01

    The long term objectives are: (1) to understand the physics of the multispectral microwave radiative characteristics of sea ice as it goes through different phases; (2) to improve characterization of sea ice cover using satellite microwave sensors; and (3) to study ice/ocean physical and biological processes associated with polynya formations and variability of the marginal sea ice region. Two field experiments were conducted to pursue these objectives. One involved measurements of radiative and physical characteristics of sea ice from a ship during a 3-month long cruise through the Weddell Sea ice pack during the Austral winter of 1986. The other involved similar measurements from two aircrafts and a submarine over the Central Arctic and Greenland Sea region. Preliminary results have already led to an enhanced understanding of the microwave signatures of pancake ice, nilas, first year ice, multiyear ice and effects of snow cover. Coastal and deep ocean polynyas and their role in bottom water formation and ocean circulation were studied using a time series of ice images from SMMR. An unsupervised cluster analysis of Arctic sea ice using SMMR and THIR emissivity and brightness temperature data was implemented. The analysis indicates the existence of several unique and persistent clusters in the Central Arctic region during winter and that the sum of the area of these clusters excluding those of first year ice is about 20 percent less than minimum ice cover area inferred from a previous summer data. This result is consistent with saline surface for some multiyear ice floes as observed during MIZEZ and suggests that a significant fraction of multiyear ice floes in the Arctic have first year ice signatures.

  14. Fluid and electromagnetic transport in sea ice

    NASA Astrophysics Data System (ADS)

    Gully, Adam Spence

    Covering 7-10% of the Earth's ocean surface, sea ice is both an indicator and agent of climate change. The sea ice cover controls the exchange of heat, momentum, and gases between the ocean and atmosphere. As a material, sea ice is a polycrystalline composite consisting of a pure ice host containing brine, air, and solid salt inclusions. This dissertation examines sea ice processes that are important to climate studies. In particular, we investigate the fluid transport properties of sea ice, which mediate melt pond evolution and ice pack reflectance, snow-ice formation, nutrient replenishment for microbial communities, and the evolution of salinity profiles. We also examine the electromagnetic monitoring of these processes, which rely on some knowledge of the effective electrical properties of sea ice. Columnar sea ice is effectively impermeable to fluid flow below a 5% brine volume fraction, yet is permeable for brine volume fractions above this threshold value. In two different experiments conducted in the Arctic and Antarctic, we have found that this critical transition in fluid flow at the brine connectivity threshold displays a strong electrical signature. The sea ice conductivity data are accurately explained by percolation theory with a universal critical exponent of 2. The data also indicate marked changes in the conductivity profile with the onset of surface ponding. Further, resistance data from classical four-probe Wenner arrays on the surfaces of ice floes in Antarctica were used to indirectly reconstruct the conductivity profiles with depth, involving both the horizontal and vertical components. We note the close agreement with the actual data for some models and the inadequacy of others. Additionally, a network model for the electrical conductivity of sea ice is developed, which incorporates statistical measurements of the brine microstructure. The numerical simulations are in close agreement with direct measurements we made in Antarctica on the

  15. 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.

  16. 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.

  17. 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...

  18. 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

  19. Fram Strait Spring Ice Export and September Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Smedsrud, Lars H.; Halvorsen, Mari H.; Stroeve, Julienne; Zhang, Rong; Kloster, Kjell

    2016-04-01

    The Arctic Basin exports between 600 000 - 1 million km² of it's sea ice cover southwards through Fram Strait each year, comparing to about 10% of the ice covered area inside the basin. During winter ice export results in growth of new and relatively thin ice inside the basin, while during summer or spring export contributes directly to open water further north. A new updated time series from 1935 to 2014 of Fram Strait sea ice area export shows that the long-term annual mean export is about 880,000 km², with large annual and decadal variability and no long-term trend over the past 80 years. Nevertheless, the last decade has witnessed increased annual ice export, with several years having annual ice export exceed 1 million km². Evaluating the trend onwards from 1979, when satellite based sea ice coverage became more readily available, reveals an increase in annual export of about +6% per decade. This increase is caused by higher southward ice drift speeds due to stronger southward geostrophic winds, largely explained by increasing surface pressure over Greenland. Spring and summer area export increased more (+11% per decade) than in autumn and winter. Contrary to the last decade the 1950 - 1970 period had low export during spring and summer, and mid-September sea ice extent was consistently higher than both before and after these decades. We thus find that export anomalies during spring have a clear influence on the following September sea ice extent in general, and that for the recent decade the export may be partially responsible for the accelerating decline in Arctic sea ice extent.

  20. 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.

  1. 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.

  2. 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.

  3. Antarctic sea ice thickness affects algae populations

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-01-01

    In the waters off Antarctica, algae grow and live in the sea ice that surrounds the southern continent—a floating habitat sure to change as the planet warms. As with most aquatic ecosystems, microscopic algae form the base of the Southern Ocean food web. Distinct algae populations reside in the sea ice surface layers, on the ice's underside, and within the floating ice itself. The algae that reside on the floating ice's underside are particularly important for the region's krill population, while those on the interior or surface layers are less accessible. Understanding how changing sea ice properties will affect the regional biology, then, depends on understanding how algae populations interact with the ice.

  4. 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.

  5. 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

  6. On sea level - ice sheet interactions

    NASA Astrophysics Data System (ADS)

    Gomez, Natalya Alissa

    This thesis focuses on the physics of static sea-level changes following variations in the distribution of grounded ice and the influence of these changes on the stability and dynamics of marine ice sheets. Gravitational, deformational and rotational effects associated with changes in grounded ice mass lead to markedly non-uniform spatial patterns of sea-level change. I outline a revised theory for computing post-glacial sea-level predictions and discuss the dominant physical effects that contribute to the patterns of sea-level change associated with surface loading on different timescales. I show, in particular, that a large sea-level fall (rise) occurs in the vicinity of a retreating (advancing) ice sheet on both short and long timescales. I also present an application of the sea-level theory in which I predict the sea-level changes associated with a new model of North American ice sheet evolution and consider the implications of the results for efforts to establish the sources of Meltwater Pulse 1A. These results demonstrate that viscous deformational effects can influence the amplitude of sea-level changes observed at far-field sea-level sites, even when the time window being considered is relatively short (≤ 500 years). Subsequently, I investigate the feedback of sea-level changes on marine ice-sheet stability and dynamics by coupling a global sea-level model to ice-sheet models of increasing complexity. To begin, I incorporate gravitationally self-consistent sea-level changes into an equilibrium marine ice-sheet stability theory to show that the sea-level changes have a stabilizing influence on ice-sheet retreat. Next, I consider the impact of the stabilizing mechanism on the timescale of ice-sheet retreat using a 1D dynamic coupled ice sheet - sea level model. Simulations with the coupled model, which incorporate viscoelastic deformation of the solid Earth, show that local sea-level changes at the grounding line act to slow, and in some cases, halt

  7. 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

  8. Sea ice biogeochemistry: a guide for modellers.

    PubMed

    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.

  9. Contrasting Arctic and Antarctic sea ice temperatures

    NASA Astrophysics Data System (ADS)

    Vancoppenolle, Martin; Raphael, Marilyn; Rousset, Clément; Vivier, Frédéric; Moreau, Sébastien; Delille, Bruno; Tison, Jean-Louis

    2016-04-01

    Sea ice temperature affects the sea ice growth rate, heat content, permeability and habitability for ice algae. Large-scale simulations with NEMO-LIM suggest large ice temperature contrasts between the Arctic and the Antarctic sea ice. First, Antarctic sea ice proves generally warmer than in the Arctic, in particular during winter, where differences reach up to ~10°C. Second, the seasonality of temperature is different among the two hemispheres: Antarctic ice temperatures are 2-3°C higher in spring than they are in fall, whereas the opposite is true in the Arctic. These two key differences are supported by the available ice core and mass balance buoys temperature observations, and can be attributed to differences in air temperature and snow depth. As a result, the ice is found to be habitable and permeable over much larger areas and much earlier in late spring in the Antarctic as compared with the Arctic, which consequences on biogeochemical exchanges in the sea ice zone remain to be evaluated.

  10. Sea ice in the paleoclimate system: the challenge of reconstructing sea ice from proxies - an introduction

    NASA Astrophysics Data System (ADS)

    de Vernal, Anne; Gersonde, Rainer; Goosse, Hugues; Seidenkrantz, Marit-Solveig; Wolff, Eric W.

    2013-11-01

    Sea ice is an important component of the Earth system with complex dynamics imperfectly documented from direct observations, which are primarily limited to the last 40 years. Whereas large amplitude variations of sea ice have been recorded, especially in the Arctic, with a strikingly fast decrease in recent years partly attributed to the impact of anthropogenic climate changes, little is known about the natural variability of the sea ice cover at multi-decadal to multi-millennial time scales. Hence, there is a need to establish longer sea ice time series to document the full range of sea ice variations under natural forcings. To do this, several approaches based on biogenic or geochemical proxies have been developed from marine, ice core and coastal records. The status of the sea ice proxies has been discussed by the Sea Ice Proxy (SIP) working group endorsed by PAGES during a first workshop held at GEOTOP in Montréal. The present volume contains a set of papers addressing various sea ice proxies and their application to large scale sea ice reconstruction. Here we summarize the contents of the volume, including a table of various proxies available in marine sediments and ice cores, with their possibilities and limitations.

  11. Critical behavior of transport in sea ice

    NASA Astrophysics Data System (ADS)

    Golden, K. M.

    2003-10-01

    Geophysical materials such as sea ice, rocks, soils, snow, and glacial ice are composite media with complex, random microstructures. The effective fluid, gas, thermal, and electromagnetic transport properties of these materials play an important role in the large-scale dynamics and behavior of many geophysical systems. A striking feature of such media is that subtle changes in microstructural characteristics can induce changes over many orders of magnitude in the transport properties of the materials, which in turn can have significant large-scale geophysical effects. For example, sea ice, which mediates energy transfer between the ocean and atmosphere, plays a key role in global climate, and serves as an indicator of climatic change, is a porous composite of ice, brine and gases. Relevant length scales range from microns and millimeters for individual brine structures, to centimeters and meters for connected brine channels across floes, to hundreds of kilometers across an ice pack. Sea ice is distinguished from many other porous composites, such as sandstones or bone, in that its microstructure and bulk material properties can vary dramatically over a relatively small temperature range. The fluid permeability of sea ice ranges over six orders of magnitude for temperatures between 0°C and -25°C. Moreover, small changes in brine volume fraction around a threshold value of about 5%, corresponding to variations in temperature around a critical point of about -5°C, control an important transition between low and high fluid permeability regimes. Below this critical temperature, the sea ice is effectively impermeable, while for higher temperatures the brine phase becomes connected over macroscopic scales, allowing fluid transport through the ice. This transition has been observed to impact a wide range of phenomena such as surface flooding and snow-ice formation, enhancement of heat transfer due to fluid motion, mixing in the upper ocean, melt pool persistence

  12. 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.

  13. 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

  14. Evidence for radionuclide transport by sea ice

    USGS Publications Warehouse

    Meese, D.A.; Reimnitz, E.; Tucker, W. B.; Gow, A.J.; Bischof, J.; Darby, D.

    1997-01-01

    Ice and ice-borne sediments were collected across the Arctic Basin during the Arctic Ocean Section, 1994 (AOS-94), a recent US/Canada trans- Arctic expedition. Sediments were analysed for 137Cs, clay mineralogy and carbon. Concentrations of 137Cs ranged from 5 to 73 Bq kg-1 in the ice- borne sediments. Concentrations of ice samples without sediment were all less than 1 Bq m-3. The sediment sample with the highest 137Cs concentration (73 Bq kg-1)was collected in the Beaufort Sea. This concentration was significantly higher than in bottom sediments collected in the same area, indicating an ice transport mechanism from an area with correspondingly higher concentrations. Recent results from the application of ice transport models and sediment analyses indicate that it is very likely that sediments are transported by ice, from the Siberian shelf areas to the Beaufort Sea.

  15. 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.

  16. Ice Types in the Beaufort Sea, Alaska

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Determining the amount and type of sea ice in the polar oceans is crucial to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite remote sensing instruments; the synthetic aperture radar (SAR) on board the RADARSAT satellite and the Multi-angle Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea off the north coast of Alaska was classified and mapped in these concurrent images acquired March 19, 2001 and mapped to the same geographic area.

    To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center constructs ice charts using several data sources including RADARSAT SAR images such as the one shown at left. SAR classifies sea ice types primarily by how the surface and subsurface roughness influence radar backscatter. In the SAR image, white lines delineate different sea ice zones as identified by the National Ice Center. Regions of mostly multi-year ice (A) are separated from regions with large amounts of first year and younger ice (B-D), and the dashed white line at bottom marks the coastline. In general, sea ice types that exhibit increased radar backscatter appear bright in SAR and are identified as rougher, older ice types. Younger, smoother ice types appear dark to SAR. Near the top of the SAR image, however, red arrows point to bright areas in which large, crystalline 'frost flowers' have formed on young, thin ice, causing this young ice type to exhibit an increased radar backscatter. Frost flowers are strongly backscattering at radar wavelengths (cm) due to both surface roughness and the high salinity of frost flowers, which causes them to be highly reflective to radar energy.

    Surface roughness is also registered by MISR, although the roughness observed is at a different spatial scale. Older, rougher ice areas are predominantly backward scattering to

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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…

  2. 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

  3. Microwave properties of sea ice in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Onstott, R. G.; Larson, R. W.

    1986-01-01

    Active microwave properties of summer sea ice were measured. Backscatter data were acquired at frequencies from 1 to 17 GHz, at angles from 0 to 70 deg from vertical, and with like and cross antenna polarizations. Results show that melt-water, snow thickness, snowpack morphology, snow surface roughness, ice surface roughness, and deformation characteristics are the fundamental scene parameters which govern the summer sea ice backscatter response. A thick, wet snow cover dominates the backscatter response and masks any ice sheet features below. However, snow and melt-water are not distributed uniformly and the stage of melt may also be quite variable. These nonuniformities related to ice type are not necessarily well understood and produce unique microwave signature characteristics.

  4. 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.

  5. 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

  6. Effects of recent decreases in arctic sea ice on an ice-associated marine bird

    NASA Astrophysics Data System (ADS)

    Divoky, George J.; Lukacs, Paul M.; Druckenmiller, Matthew L.

    2015-08-01

    Recent major reductions in summer arctic sea ice extent could be expected to be affecting the distributions and life histories of arctic marine biota adapted to living adjacent to sea ice. Of major concern are the effects of ice reductions, and associated increasing SST, on the most abundant forage fish in the Arctic, Arctic cod (Boreogadus saida), the primary prey for the region's upper trophic level marine predators. The black guillemot (Cepphus grylle mandtii) is an ice-obligate diving seabird specializing in feeding on Arctic cod and has been studied annually since 1975 at a breeding colony in the western Beaufort Sea. The data set is one of the few allowing assessment of the response of an upper trophic marine predator to recent decadal changes in the region's cryosphere. Analysis of oceanographic conditions north of the colony from 1975 to 2012 for the annual period when parents provision young (mid-July to early September), found no major regime shifts in ice extent or SST until the late 1990s with major decreases in ice and increases in SST in the first decade of the 21st Century. We examined decadal variation in late summer oceanographic conditions, nestling diet and success, and overwinter adult survival, comparing a historical period (1975-1984) with a recent (2003-2012) one. In the historical period sea ice retreated an average of 1.8 km per day from 15 July to 1 September to an average distance of 95.8 km from the colony, while in the recent period ice retreat averaged 9.8 km per day to an average distance of 506.9 km for the same time period. SST adjacent to the island increased an average of 2.9 °C between the two periods. While Arctic cod comprised over 95% of the prey provided to nestlings in the historical period, in the recent period 80% of the years had seasonal decreases, with Arctic cod decreasing to <5% of the nestling diet, and nearshore demersals, primarily sculpin (Cottidae), comprising the majority of the diet. A five-fold increase in

  7. 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

  8. 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.

  9. 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...

  10. 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 ...

  11. 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...

  12. 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.

  13. Inference of optical properties from radiation profiles within melting landfast sea ice

    NASA Astrophysics Data System (ADS)

    Ehn, J. K.; Papakyriakou, T. N.; Barber, D. G.

    2008-09-01

    Vertical in-ice spectral radiation profiles were measured within melting 1.5- to 1.7-m-thick landfast sea ice in western Hudson Bay on 25 April 2005. Because the surface ice was subject to extensive melting and refreezing, the sea ice had fractioned into two main types, i.e., areas of more reflective white ice and less reflective blue ice. The shortwave albedo was about 0.69 for white ice and 0.47 for bare blue ice. The corresponding shortwave transmittance through the ice cover was about 0.02 and 0.09, respectively. The inherent optical properties of the sea ice were inferred by tying the input and output of radiative transfer simulations to the radiation profiles and the ice physical properties, as well as to the irradiance measurements above and below the ice cover. To explain observed spectral albedo and transmittance simultaneously, the ice/snow above the interior ice was divided into three layers on the basis of the following observations: snow (white ice) or a thin soot containing layer (blue ice), drained ice above and saturated ice below the waterline. Similarly, the bottom portion was divided on the basis of the presence of a living ice algae layer adjacent to the seawater interface and a layer extending 30 cm above the bottom containing mostly detrital matter. The interior of the ice, i.e., roughly 20-40 cm from boundaries, was well-represented by a single layer of pure sea ice as the radiation field was nearly asymptotic and the absorption spectra showed little evidence of impurities. Representative values for the scattering coefficient ranged 600-800 m-1, with a Henyey-Greenstein asymmetry parameter of 0.995. Observations within white ice suggest that about 40% of the energy responsible of the internal melting was provided directly by shortwave radiation, while the rest is due to heat conduction.

  14. Using Sea Ice Age as a Proxy for Sea Ice Thickness

    NASA Astrophysics Data System (ADS)

    Stroeve, J. C.; Tschudi, M. A.; Maslanik, J. A.

    2014-12-01

    Since the beginning of the modern satellite record starting in October 1978, the Arctic sea ice cover has been shrinking, with the largest changes observed at the end of the melt season in September. Through 2013, the September ice extent has declined at a rate of -14.0% dec-1, or -895,300 km2 dec-1. The seven lowest September extents in the satellite record have all occurred in the past seven years. This reduction in ice extent is accompanied by large reductions in winter ice thicknesses that are primarily explained by changes in the ocean's coverage of multiyear ice (MYI). Using the University of Colorado ice age product developed by J. Maslanik and C. Fowler, and currently produced by M. Tschudi we present recent changes in the distribution of ice age from the mid 1980s to present. The CU ice age product is based on (1) the use of ice motion to track areas of sea ice and thus estimate how long the ice survives within the Arctic, and (2) satellite imagery of sea ice concentration to determine when the ice disappears. Age is assigned on a yearly basis, with the age incremented by one year if the ice survives summer melt and stays within the Arctic domain. Age is counted from 1 to 10 years, with all ice older than 10 years assigned to the "10+" age category. The position of the ice is calculated on weekly time steps on NSIDC's 12.5-km EASE-grid. In the mid-1980s, MYI accounted for 70% of total winter ice extent, whereas by the end of 2012 it had dropped to less than 20%. This reflects not only a change in ice type, but also a general thinning of the ice pack, as older ice tends to be thicker ice. Thus, with older ice being replaced by thinner first-year ice, the ice pack is more susceptible to melting out than it was in 1980's. It has been suggested that ice age may be a useful proxy for long-term changes in ice thickness. To assess the relationship between ice age and thickness, and how this may be changing over time, we compare the ice age fields to several

  15. Bacterial community structure in the Sulu Sea and adjacent areas

    NASA Astrophysics Data System (ADS)

    Yoshida, Akihiro; Nishimura, Masahiko; Kogure, Kazuhiro

    2007-01-01

    The deep waters of the Sulu Sea are characterized by relatively high and constant water temperatures and low oxygen concentrations. To examine the effect of these characteristics on the bacterial community structure, the culture-independent molecular method was applied to samples from the Sulu Sea and the adjacent areas. DNA was extracted from environmental samples, and the analysis was carried out on PCR-amplified 16S rDNA; fragments were analyzed by denaturing gradient gel electrophoresis (DGGE) and nonmetric multidimensional scaling analysis. Stations in the Sulu Sea and the adjacent areas showed much more prominent vertical stratification of bacterial community structures than horizontal variation. As predominant sequences, cyanobacteria and α-proteobacteria at 10 m depth, δ-proteobacteria at 100 m depth, and green nonsulfur bacteria below 1000 m depth were detected in all sampling areas. High temperatures and low oxygen concentrations are thought to be minor factors in controlling community structure; the quantity and quality of organic materials supplied by the sinking particles, and hydrostatic pressure are believed to be important.

  16. 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.

  17. 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.

  18. Ice sheet systems and sea level change.

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.

    2015-12-01

    Modern views of ice sheets provided by satellites, airborne surveys, in situ data and paleoclimate records while transformative of glaciology have not fundamentally changed concerns about ice sheet stability and collapse that emerged in the 1970's. Motivated by the desire to learn more about ice sheets using new technologies, we stumbled on an unexplored field of science and witnessed surprising changes before realizing that most were coming too fast, soon and large. Ice sheets are integrant part of the Earth system; they interact vigorously with the atmosphere and the oceans, yet most of this interaction is not part of current global climate models. Since we have never witnessed the collapse of a marine ice sheet, observations and exploration remain critical sentinels. At present, these observations suggest that Antarctica and Greenland have been launched into a path of multi-meter sea level rise caused by rapid climate warming. While the current loss of ice sheet mass to the ocean remains a trickle, every mm of sea level change will take centuries of climate reversal to get back, several major marine-terminating sectors have been pushed out of equilibrium, and ice shelves are irremediably being lost. As glaciers retreat from their salty, warm, oceanic margins, they will melt away and retreat slower, but concerns remain about sea level change from vastly marine-based sectors: 2-m sea level equivalent in Greenland and 23-m in Antarctica. Significant changes affect 2/4 marine-based sectors in Greenland - Jakobshavn Isb. and the northeast stream - with Petermann Gl. not far behind. Major changes have affected the Amundsen Sea sector of West Antarctica since the 1980s. Smaller yet significant changes affect the marine-based Wilkes Land sector of East Antarctica, a reminder that not all marine-based ice is in West Antarctica. Major advances in reducing uncertainties in sea level projections will require massive, interdisciplinary efforts that are not currently in place

  19. 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.

  20. 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

  1. The NRL 2011 Airborne Sea-Ice Thickness Campaign

    NASA Astrophysics Data System (ADS)

    Brozena, J. M.; Gardner, J. M.; Liang, R.; Ball, D.; Richter-Menge, J.

    2011-12-01

    In March of 2011, the US Naval Research Laboratory (NRL) performed a study focused on the estimation of sea-ice thickness from airborne radar, laser and photogrammetric sensors. The study was funded by ONR to take advantage of the Navy's ICEX2011 ice-camp /submarine exercise, and to serve as a lead-in year for NRL's five year basic research program on the measurement and modeling of sea-ice scheduled to take place from 2012-2017. Researchers from the Army Cold Regions Research and Engineering Laboratory (CRREL) and NRL worked with the Navy Arctic Submarine Lab (ASL) to emplace a 9 km-long ground-truth line near the ice-camp (see Richter-Menge et al., this session) along which ice and snow thickness were directly measured. Additionally, US Navy submarines collected ice draft measurements under the groundtruth line. Repeat passes directly over the ground-truth line were flown and a grid surrounding the line was also flown to collect altimeter, LiDAR and Photogrammetry data. Five CRYOSAT-2 satellite tracks were underflown, as well, coincident with satellite passage. Estimates of sea ice thickness are calculated assuming local hydrostatic balance, and require the densities of water, ice and snow, snow depth, and freeboard (defined as the elevation of sea ice, plus accumulated snow, above local sea level). Snow thickness is estimated from the difference between LiDAR and radar altimeter profiles, the latter of which is assumed to penetrate any snow cover. The concepts we used to estimate ice thickness are similar to those employed in NASA ICEBRIDGE sea-ice thickness estimation. Airborne sensors used for our experiment were a Reigl Q-560 scanning topographic LiDAR, a pulse-limited (2 nS), 10 GHz radar altimeter and an Applanix DSS-439 digital photogrammetric camera (for lead identification). Flights were conducted on a Twin Otter aircraft from Pt. Barrow, AK, and averaged ~ 5 hours in duration. It is challenging to directly compare results from the swath LiDAR with the

  2. Lidar detection of leads in Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Schnell, R. C.; Barry, R. G.; Miles, M. W.; Andreas, E. L.; Radke, L. F.; Brock, C. A.; Mccormick, M. P.

    1989-01-01

    REMOTE sensing using an airborne infrared lidar has shown an unexpected capability to detect open leads in Arctic sea ice and their associated meteorology in winter. It is shown here that vertical profiles of backscattered radiation demonstrate strong returns from hydrometeor plumes originating from leads having a surface water temperature near -1.8 C. Recently refrozen leads are also distinguishable by the lidar backscatter from adjacent thicker, older sea ice. Wide leads release enough energy to create buoyant plumes which penetrate the Arctic boundary layer inversion, transporting heat and moisture into the troposphere. These results show that the role of the Arctic as a global heat sink may need to be reevaluated, and that lead plumes have a significant effect on the radiation budget.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. [Spectral features analysis of sea ice in the Arctic Ocean].

    PubMed

    Ke, Chang-qing; Xie, Hong-jie; Lei, Rui-bo; Li, Qun; Sun, Bo

    2012-04-01

    Sea ice in the Arctic Ocean plays an important role in the global climate change, and its quick change and impact are the scientists' focus all over the world. The spectra of different kinds of sea ice were measured with portable ASD FieldSpec 3 spectrometer during the long-term ice station of the 4th Chinese national Arctic Expedition in 2010, and the spectral features were analyzed systematically. The results indicated that the reflectance of sea ice covered by snow is the highest one, naked sea ice the second, and melted sea ice the lowest. Peak and valley characteristics of spectrum curves of sea ice covered by thick snow, thin snow, wet snow and snow crystal are very significant, and the reflectance basically decreases with the wavelength increasing. The rules of reflectance change with wavelength of natural sea ice, white ice and blue ice are basically same, the reflectance of them is medium, and that of grey ice is far lower than natural sea ice, white ice and blue ice. It is very significant for scientific research to analyze the spectral features of sea ice in the Arctic Ocean and to implement the quantitative remote sensing of sea ice, and to further analyze its response to the global warming.

  10. Formation of an aggregate scale in Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Hopkins, Mark A.; Frankenstein, Susan; Thorndike, Alan S.

    2004-01-01

    The ice pack covering northern seas is a mixture of thick ridged and rafted ice, undeformed ice, and open water. Conventional Eulerian Arctic sea ice models use a plastic yield surface to characterize the constitutive behavior of the pack. An alternative is to adopt a discontinuous Lagrangian approach and explicitly model the formation of leads and pressure ridges. We use a Lagrangian ice model that consists of thousands of discrete polygonal floes 1-4 km in width. At the beginning of a simulation the ice floes are frozen together in a square domain. We apply a linearly varying wind stress that deforms the pack by stretching the viscous-elastic joints between adjacent floes. Fractures propagate along joints forming a crack pattern in the model ice pack. The crack pattern defines a system of large plates 10-100 km in width that are aggregates of many individual floes. The average size of the plates is determined by a competition between the rate of crack creation and the speed of the relaxation wave that travels outward from a newly broken joint and reduces stresses in the surrounding pack. Simulation results are used to characterize the formation of the aggregate structure and to determine how the rate of crack creation and the average area of the aggregate plates depends on tensile strength, the wind stress gradient, and the size of the individual floes. After the formation of the aggregate-scale plate structure, subsequent deformation occurs at the plate boundaries. Since the usual state of the ice pack is a state of failure, an interesting situation is created in which the initial wind-driven deformation creates the material conditions or aggregate structure under which subsequent deformation occurs.

  11. Sea Ice, Bristol Bay, Alaska, USA

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This north looking view shows the coast of Alaska, north of the Aleutians, and the eastern margin of the Bering Sea (58.0N, 159.5W). Bristol Bay is apparent in the foreground and Nunivak Island can be seen just below the Earth's horizon, at a distance of about 300 nautical miles. Similar views, photographed during previous missions, when analyzed with these recent views may yield information about regional ice drift and breakup of ice packs.

  12. 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

  13. 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.

  14. Dynamics of landfast sea ice near Jangbogo Antarctic Research Station observed by SAR interferometry

    NASA Astrophysics Data System (ADS)

    Lee, H.; Han, H.

    2015-12-01

    Landfast sea ice is a type of sea ice adjacent to the coast and immobile for a certain period of time. It is important to analyze the temporal and spatial variation of landfast ice because it has significant influences on marine ecosystem and the safe operation of icebreaker vessels. However, it has been a difficult task for both remote sensing and in situ observation to discriminate landfast ice from other types of sea ice, such as pack ice, and also to understand the dynamics and internal strss-strain of fast ice. In this study, we identify landfast ice and its annual variation in Terra Nova Bay (74° 37' 4"S, 164° 13' 7"E), East Antarctica, where Jangbogo Antarctic Research Station has recently been constructed in 2014, by using Interferometric Synthetic Aperture Radar (InSAR) technology. We generated 38 interferograms having temporal baselines of 1-9 days out of 62 COSMO-SkyMed SAR images over Terra Nova Bay obtained from December 2010 to January 2012. Landfast ice began to melt in November 2011 when air temperature raised above freezing point but lasted more than two month to the end of the study period in January 2012. No meaningful relationship was found between sea ice extent and wind and current. Glacial strain (~67cm/day) is similar to tidal strain (~40 cm) so that they appear similar in one-day InSAR. As glacial stress is cumulative while tidal stress is oscillatory, InSAR images with weekly temporal baseline (7~9 days) revealed that a consistent motion of Campbell Glacier Tongue (CGT) is pushing the sea ice continuously to make interferometric fringes parallel to the glacier-sea ice contacts. Glacial interferometric fringe is parallel to the glacier-sea ice contact lines while tidal strain should be parallel to the coastlines defined by sea shore and glacier tongue. DDInSAR operation removed the consistent glacial strain leaving tidal strain alone so that the response of fast ice to tide can be used to deduce physical properties of sea ice in various

  15. 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

  16. 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

  17. 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...

  18. Use of ERTS data for mapping Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Barnes, J. C.; Bowley, C. J.

    1973-01-01

    This investigation is to evaluate the application of ERTS data for detecting and mapping Arctic sea ice. The specific objectives are to determine the spectral bands most suitable for detecting ice, to measure the scale and types of ice features that can be detected, and to develop interpretive techniques for differentiating ice from clouds and for mapping ice concentrations. The ERTS data are being analyzed primarily for three Arctic areas, the eastern Beaufort Sea, Baffin Bay, and the Greenland Sea.

  19. Ice core reconstruction of sea ice change in the Amundsen-Ross Seas since 1702 A.D.

    NASA Astrophysics Data System (ADS)

    Thomas, Elizabeth R.; Abram, Nerilie J.

    2016-05-01

    Antarctic sea ice has been increasing in recent decades, but with strong regional differences in the expression of sea ice change. Declining sea ice in the Bellingshausen Sea since 1979 (the satellite era) has been linked to the observed warming on the Antarctic Peninsula, while the Ross Sea sector has seen a marked increase in sea ice during this period. Here we present a 308 year record of methansulphonic acid from coastal West Antarctica, representing sea ice conditions in the Amundsen-Ross Sea. We demonstrate that the recent increase in sea ice in this region is part of a longer trend, with an estimated ~1° northward expansion in winter sea ice extent (SIE) during the twentieth century and a total expansion of ~1.3° since 1702. The greatest reconstructed SIE occurred during the mid-1990s, with five of the past 30 years considered exceptional in the context of the past three centuries.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. SIPEX—exploring the Antarctic sea ice zone

    NASA Astrophysics Data System (ADS)

    Zicus, Sandra; Dobson, Jane; Worby, Anthony

    2008-11-01

    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 Southern Ocean ecosystems. One of the main goals of SIPEX was to conduct large-scale sea ice and snow thickness surveys for the validation of satellite-based measurements. SIPEX scientists used a variety of techniques including helicopter-based radar and laser altimetry, as well as a remotely operated underwater vehicle, to gather baseline data on Antarctic sea ice thickness and the under-ice environment. These data will be invaluable for monitoring possible future changes in the sea ice around Antarctica.

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

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1994-01-01

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

  6. Macrobenthos of Yenisei Bay and the adjacent Kara Sea shelf

    NASA Astrophysics Data System (ADS)

    Galkin, S. V.; Vedenin, A. A.

    2015-07-01

    Trawl samples were collected in the northern region of Yenisei Bay and adjacent parts of the Kara Sea shelf. A total of eight stations were taken. We found more than 200 species of benthic organisms. A consecutive replacement of benthic communities is observed when going to the north from the Ob and Yenisei estuaries to the open parts of the sea. We could distinguish four different species complexes in the investigated area: a brackish-water complex where Saduria entomon is dominant; an intermediate complex where S. sibirica, S. sabini and Portlandia aestuariorum are dominant; a transitional complex with P. arctica as a dominant species and with a small amount of Ophiocten sericeum; a marine complex where O. sericeum is dominant. When salinity increased, some brackish-water species were replaced by related euryhaline species. One such example was the replacement of brackish-water Saduria entomon isopods by two euryhaline species: S. sibirica and S. sabini. The consecutive replacement of benthic communities showed a break near Sverdrup Island. In this area the marine complex was replaced by a transitional complex with P. arctica.

  7. Recent wind driven high sea ice area export in the Fram Strait contributes to Arctic sea ice decline

    NASA Astrophysics Data System (ADS)

    Smedsrud, L. H.; Sirevaag, A.; Kloster, K.; Sorteberg, A.; Sandven, S.

    2011-10-01

    Arctic sea ice area has been decreasing for the past two decades. Apart from melting, the southward drift through Fram Strait is the main ice loss mechanism. We present high resolution sea ice drift data across 79° N from 2004 to 2010. Ice drift has been derived from radar satellite data and corresponds well with variability in local geostrophic wind. The underlying East Greenland current contributes with a constant southward speed close to 5 cm s-1, and drives around a third of the ice export. We use geostrophic winds derived from reanalysis data to calculate the Fram Strait ice area export back to 1957, finding that the sea ice area export recently is about 25% larger than during the 1960's. The increase in ice export occurred mostly during winter and is directly connected to higher southward ice drift velocities, due to stronger geostrophic winds. The increase in ice drift is large enough to counteract a decrease in ice concentration of the exported sea ice. Using storm tracking we link changes in geostrophic winds to more intense Nordic Sea low pressure systems. Annual sea ice area export likely has a significant influence on the summer sea ice variability and we find low values in the 1960's, the late 1980's and 1990's, and particularly high values during 2005-2008. The study highlights the possible role of variability in ice export as an explanatory factor for understanding the dramatic loss of Arctic sea ice during the last decades.

  8. 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.

  9. 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.

  10. Holocene cooling culminates in sea ice oscillations in Fram Strait

    NASA Astrophysics Data System (ADS)

    Müller, Juliane; Werner, Kirstin; Stein, Ruediger; Fahl, Kirsten; Moros, Matthias; Jansen, Eystein

    2012-07-01

    A reconstruction of Holocene sea ice conditions in the Fram Strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years BP. Organic geochemical analyses of sediment cores from eastern and western Fram Strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic (and atmospheric) circulation system. By means of the sea ice proxy IP25, phytoplankton-derived biomarkers and ice rafted detritus (IRD) increasing sea ice occurrences are traced along the western continental margin of Spitsbergen throughout the Holocene, which supports previous palaeoenvironmental reconstructions that document a general cooling. A further significant ice advance during the Neoglacial is accompanied by distinct sea ice fluctuations, which point to short-term perturbations in either the Atlantic Water advection or Arctic Water outflow at this site. At the continental shelf of East Greenland, the general Holocene cooling, however, seems to be less pronounced and sea ice conditions remained rather stable. Here, a major Neoglacial increase in sea ice coverage did not occur before 1000 years BP. Phytoplankton-IP25 indices ("PIP25-Index") are used for more explicit sea ice estimates and display a Mid Holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern Fram Strait, while the inner East Greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire Holocene.

  11. 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.

  12. 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.

  13. 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

  14. Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris.

    PubMed

    Stickley, Catherine E; St John, Kristen; Koç, Nalân; Jordan, Richard W; Passchier, Sandra; Pearce, Richard B; Kearns, Lance E

    2009-07-16

    Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.

  15. 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.

  16. 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

  17. 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.

  18. Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

    NASA Astrophysics Data System (ADS)

    Patton, H.; Hubbard, A.; Bradwell, T.; Glasser, N. F.; Hambrey, M. J.; Clark, C. D.

    2013-08-01

    Understanding the retreat behaviour of past marine-ice sheets provides vital context to accurate assessment of the present stability and long-term response of contemporary polar-ice sheets to climate and oceanic warming. Here new multibeam swath-bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process-dynamics associated with deglaciation of the British-Celtic Ice Sheet (BCIS) within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream, the largest draining the BCIS, and the retreat of outlet glaciers draining the adjacent, terrestrially based ice sheet centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet re-advances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice-divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the re-advancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short-time scales across marine-sectors of the Greenland and Antarctic ice sheets.

  19. Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

    NASA Astrophysics Data System (ADS)

    Patton, H.; Hubbard, A.; Bradwell, T.; Glasser, N. F.; Hambrey, M. J.; Clark, C. D.

    2013-12-01

    Understanding the retreat behaviour of past marine-based ice sheets provides vital context for accurate assessments of the present stability and long-term response of contemporary polar ice sheets to climate and oceanic warming. Here new multibeam swath bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process dynamics associated with deglaciation of the Celtic ice sheet within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream and the retreat of outlet glaciers draining the adjacent, terrestrially based ice cap centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet readvances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and which dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the readvancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short timescales across marine sectors of the Greenland and Antarctic ice sheets.

  20. 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.

  1. 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.

  2. Factors affecting dynamical seasonal prediction of the Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Wang, W.; Chen, M.; Kumar, A.; Hung, M.

    2013-12-01

    Arctic sea ice variability has received increasing attention during the last decade. Seasonal prediction of the Arctic sea ice has been primarily produced with statistical methods during the past years. A few operational centers have recently implemented dynamical sea ice component in the coupled atmosphere-ocean forecast systems for seasonal climate prediction. Yet various issues remain to be resolved for an improved prediction of seasonal sea ice variations. In this study, we analyze the forecast of sea ice extent in the NCEP Climate Forecast System version 2 (CFSv2) and address factors that affect the representation of the observed sea ice variability in the forecast model. The analysis will be based on retrospective and real-time 9-month forecasts from the CFSv2 for 1982-2012. We will first assess the overall performance of the CFSv2 in capturing the observed sea ice extent climatology, long-term trend, and interannual anomalies. We will then discuss factors that affect the sea ice prediction, including: (1) consistency of the initialization of the observed sea ice concentration, (2) impacts of surface heat fluxes related to atmospheric model physics, (3) bias in sea surface temperatures, and (4) impacts of initial sea ice thickness.

  3. 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.

  4. 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.

  5. Ice formation and growth shape bacterial community structure in Baltic Sea drift ice.

    PubMed

    Eronen-Rasimus, Eeva; Lyra, Christina; Rintala, Janne-Markus; Jürgens, Klaus; Ikonen, Vilma; Kaartokallio, Hermanni

    2015-02-01

    Drift ice, open water and under-ice water bacterial communities covering several developmental stages from open water to thick ice were studied in the northern Baltic Sea. The bacterial communities were assessed with 16S rRNA gene terminal-restriction fragment length polymorphism and cloning, together with bacterial abundance and production measurements. In the early stages, open water and pancake ice were dominated by Alphaproteobacteria and Actinobacteria, which are common bacterial groups in Baltic Sea wintertime surface waters. The pancake ice bacterial communities were similar to the open-water communities, suggesting that the parent water determines the sea-ice bacterial community in the early stages of sea-ice formation. In consolidated young and thick ice, the bacterial communities were significantly different from water bacterial communities as well as from each other, indicating community development in Baltic Sea drift ice along with ice-type changes. The thick ice was dominated by typical sea-ice genera from classes Flavobacteria and Gammaproteobacteria, similar to those in polar sea-ice bacterial communities. Since the thick ice bacterial community was remarkably different from that of the parent seawater, results indicate that thick ice bacterial communities were recruited from the rarer members of the seawater bacterial community.

  6. Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core.

    PubMed

    Spolaor, Andrea; Vallelonga, Paul; Turetta, Clara; Maffezzoli, Niccolò; Cozzi, Giulio; Gabrieli, Jacopo; Barbante, Carlo; Goto-Azuma, Kumiko; Saiz-Lopez, Alfonso; Cuevas, Carlos A; Dahl-Jensen, Dorthe

    2016-09-21

    Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called "bromine explosions" and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement.

  7. Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core

    PubMed Central

    Spolaor, Andrea; Vallelonga, Paul; Turetta, Clara; Maffezzoli, Niccolò; Cozzi, Giulio; Gabrieli, Jacopo; Barbante, Carlo; Goto-Azuma, Kumiko; Saiz-Lopez, Alfonso; Cuevas, Carlos A.; Dahl-Jensen, Dorthe

    2016-01-01

    Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called “bromine explosions” and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement. PMID:27650478

  8. Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core

    NASA Astrophysics Data System (ADS)

    Spolaor, Andrea; Vallelonga, Paul; Turetta, Clara; Maffezzoli, Niccolò; Cozzi, Giulio; Gabrieli, Jacopo; Barbante, Carlo; Goto-Azuma, Kumiko; Saiz-Lopez, Alfonso; Cuevas, Carlos A.; Dahl-Jensen, Dorthe

    2016-09-01

    Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called “bromine explosions” and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement.

  9. Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core.

    PubMed

    Spolaor, Andrea; Vallelonga, Paul; Turetta, Clara; Maffezzoli, Niccolò; Cozzi, Giulio; Gabrieli, Jacopo; Barbante, Carlo; Goto-Azuma, Kumiko; Saiz-Lopez, Alfonso; Cuevas, Carlos A; Dahl-Jensen, Dorthe

    2016-01-01

    Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called "bromine explosions" and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement. PMID:27650478

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Remote Sensing of Sea Ice from Earth Satellites

    NASA Technical Reports Server (NTRS)

    Mcclain, E. P.

    1971-01-01

    The application of meteorological satellite data for mapping ice fields is discussed. The characteristics of the photographic records of sea ice formations are described. The derivation of the composite minimum brightness chart by computer processing of the mapped satellite vidicon data for several successive days is explained. The factors which create a quantitative delimiting of the sea ice conditions are explained.

  16. 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.

  17. 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.

  18. 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.

  19. Improving Arctic sea ice edge forecasts by assimilating high horizontal resolution sea ice concentration data into the US Navy's ice forecast systems

    NASA Astrophysics Data System (ADS)

    Posey, P. G.; Metzger, E. J.; Wallcraft, A. J.; Hebert, D. A.; Allard, R. A.; Smedstad, O. M.; Phelps, M. W.; Fetterer, F.; Stewart, J. S.; Meier, W. N.; Helfrich, S. R.

    2015-08-01

    This study presents the improvement in ice edge error within the US Navy's operational sea ice forecast systems gained by assimilating high horizontal resolution satellite-derived ice concentration products. Since the late 1980's, the ice forecast systems have assimilated near real-time sea ice concentration derived from the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSMI and then SSMIS). The resolution of the satellite-derived product was approximately the same as the previous operational ice forecast system (25 km). As the sea ice forecast model resolution increased over time, the need for higher horizontal resolution observational data grew. In 2013, a new Navy sea ice forecast system (Arctic Cap Nowcast/Forecast System - ACNFS) went into operations with a horizontal resolution of ~ 3.5 km at the North Pole. A method of blending ice concentration observations from the Advanced Microwave Scanning Radiometer (AMSR2) along with a sea ice mask produced by the National Ice Center (NIC) has been developed, resulting in an ice concentration product with very high spatial resolution. In this study, ACNFS was initialized with this newly developed high resolution blended ice concentration product. The daily ice edge locations from model hindcast simulations were compared against independent observed ice edge locations. ACNFS initialized using the high resolution blended ice concentration data product decreased predicted ice edge location error compared to the operational system that only assimilated SSMIS data. A second evaluation assimilating the new blended sea ice concentration product into the pre-operational Navy Global Ocean Forecast System 3.1 also showed a substantial improvement in ice edge location over a system using the SSMIS sea ice concentration product alone. This paper describes the technique used to create the blended sea ice concentration product and the significant improvements in ice edge forecasting in both of the

  20. 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.

  1. 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.

  2. Mechanism of seasonal Arctic sea ice evolution and Arctic amplification

    NASA Astrophysics Data System (ADS)

    Kim, Kwang-Yul; Hamlington, Benjamin D.; Na, Hanna; Kim, Jinju

    2016-09-01

    Sea ice loss is proposed as a primary reason for the Arctic amplification, although the physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-Interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice loss in the Arctic Ocean and the Arctic amplification. While sea ice loss is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains thin in winter only in the Barents-Kara seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice reduction warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be free of ice. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara seas and Laptev, East Siberian, Chukchi, and Beaufort seas.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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).

  11. Estimates of ikaite export from sea ice to the underlying seawater in a sea ice-seawater mesocosm

    NASA Astrophysics Data System (ADS)

    Geilfus, Nicolas-Xavier; Galley, Ryan J.; Else, Brent G. T.; Campbell, Karley; Papakyriakou, Tim; Crabeck, Odile; Lemes, Marcos; Delille, Bruno; Rysgaard, Søren

    2016-09-01

    The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice-seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmol kg-1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64-66 µmol kg-1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmol kg-1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper

  12. 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

  13. The EUMETSAT sea ice concentration climate data record

    NASA Astrophysics Data System (ADS)

    Tonboe, Rasmus T.; Eastwood, Steinar; Lavergne, Thomas; Sørensen, Atle M.; Rathmann, Nicholas; Dybkjær, Gorm; Toudal Pedersen, Leif; Høyer, Jacob L.; Kern, Stefan

    2016-09-01

    An Arctic and Antarctic sea ice area and extent dataset has been generated by EUMETSAT's Ocean and Sea Ice Satellite Application Facility (OSISAF) using the record of microwave radiometer data from NASA's Nimbus 7 Scanning Multichannel Microwave radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager and Sounder (SSMIS) satellite sensors. The dataset covers the period from October 1978 to April 2015 and updates and further developments are planned for the next phase of the project. The methodology for computing the sea ice concentration uses (1) numerical weather prediction (NWP) data input to a radiative transfer model for reduction of the impact of weather conditions on the measured brightness temperatures; (2) dynamical algorithm tie points to mitigate trends in residual atmospheric, sea ice, and water emission characteristics and inter-sensor differences/biases; and (3) a hybrid sea ice concentration algorithm using the Bristol algorithm over ice and the Bootstrap algorithm in frequency mode over open water. A new sea ice concentration uncertainty algorithm has been developed to estimate the spatial and temporal variability in sea ice concentration retrieval accuracy. A comparison to US National Ice Center sea ice charts from the Arctic and the Antarctic shows that ice concentrations are higher in the ice charts than estimated from the radiometer data at intermediate sea ice concentrations between open water and 100 % ice. The sea ice concentration climate data record is available for download at www.osi-saf.org, including documentation.

  14. 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.

  15. 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.

  16. Effects of Arctic Sea Ice Decline on Weather and Climate: A Review

    NASA Astrophysics Data System (ADS)

    Vihma, Timo

    2014-09-01

    The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.

  17. 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.

  18. Microwave remote sensing of snow-covered sea ice

    NASA Technical Reports Server (NTRS)

    Borgeaud, M.; Kong, J. A.; Lin, F. C.

    1986-01-01

    Snow and ice are modeled as random media characterized by different dielectric constants and correlation functions. In order to model the brine inclusions of sea ice, the random medium is assumed to be anisotropic. A three-layer model is used to simulate a snow-covered ice field with the top layer being snow, the middle layer being ice, and the bottom layer being sea water. The theoretical results are illustrated for thick first-year sea ice covered by dry snow, and for artificial, thin first-year sea ice covered by wet snow as measured in controlled model tank experiments. The radar backscattering cross sections are seen to increase with snow cover for snow-covered sea ice owing to large volume scattering effects of snow.

  19. 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...

  20. 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

  1. 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.

  2. 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.

  3. Modeling ocean wave propagation under sea ice covers

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  4. Barrow Ak: A Focal Point for Ice-Albedo-Transmission Feedback Processes in Arctic Sea Ice.

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    The Arctic sea ice cover has measurably decreased in thickness, extent, and seasonal duration over the last two decades culminating in record or near-record fluctuations in 1998 and again in 2002 followed by a further strong melt season in 2003. Seasonal changes and short-term variability in the state of the ice cover and their effect on the interaction of solar radiation with the ice cover and underlying ocean are of particular importance in this context. Positive feedback processes associated with decreases in albedo and increasing transmissivity act to accelerate these changes. The rates of spring warming and summer melt as well as the length of the melt season are strongly influenced by the albedo, which in turn decreases as the melt season progresses. At the same time, increased transmission provides more energy to the upper oceanic mixed layer further increasing the potential for melting at the bottom of the ice. This ice-albedo-transmission (IAT) feedback plays a central role in modulating the heat and mass balance of the Arctic sea ice cover. Along the coastal contact zone, the feedback processes are even more complex due to interactions with the adjacent land surfaces. Indeed, this zone appears to be a focal point where the feedbacks are amplified. To understand and model the processes involved, it is necessary to determine how shortwave radiation is distributed within the ice-ocean system and how this distribution affects heat and mass balance. Analysis of this system is complicated by spatial and temporal inhomogeneity of the spring/summer ice cover, with surface conditions varying from deep snow to bare ice to melt ponds to open leads, and with ice thickness ranging from zero (open water) to ridges tens of meters thick, all within an area that is often less than one square km. Each of these categories has a different set of physical and optical properties. Treatment of the surface as a locally homogeneous medium with effective bulk optical properties

  5. Sea ice effects on salinity in northern oceans

    NASA Astrophysics Data System (ADS)

    Gerdes, Rüdiger; Koeberle, Cornelia

    2016-04-01

    Arctic sea ice volume decreases despite decreasing ice export through Fram Strait. This implies considerable chages in the thermodynamic growth of Arctic sea ice. We use a hindcast simulation with AWI's NAOSIM to estimate the spatial and temporal distribution of freezing and melting. An additional tracer allows us to follow the melt water through the Arctic and into the Nordic seas. We compare the effect of thermodynamic sea ice processes on ocean salinity between the decade of the 1990s and the first decade of the 21st century.

  6. Sea-ice indicators of polar bear habitat

    NASA Astrophysics Data System (ADS)

    Stern, Harry L.; Laidre, Kristin L.

    2016-09-01

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

  7. 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.

  8. Nonlinear threshold behavior during the loss of Arctic sea ice.

    PubMed

    Eisenman, I; Wettlaufer, J S

    2009-01-01

    In light of the rapid recent retreat of Arctic sea ice, a number of studies have discussed the possibility of a critical threshold (or "tipping point") beyond which the ice-albedo feedback causes the ice cover to melt away in an irreversible process. The focus has typically been centered on the annual minimum (September) ice cover, which is often seen as particularly susceptible to destabilization by the ice-albedo feedback. Here, we examine the central physical processes associated with the transition from ice-covered to ice-free Arctic Ocean conditions. We show that although the ice-albedo feedback promotes the existence of multiple ice-cover states, the stabilizing thermodynamic effects of sea ice mitigate this when the Arctic Ocean is ice covered during a sufficiently large fraction of the year. These results suggest that critical threshold behavior is unlikely during the approach from current perennial sea-ice conditions to seasonally ice-free conditions. In a further warmed climate, however, we find that a critical threshold associated with the sudden loss of the remaining wintertime-only sea ice cover may be likely.

  9. 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.

  10. 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.

  11. 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.

  12. Thermodynamics of slush and snow-ice formation in the Antarctic sea-ice zone

    NASA Astrophysics Data System (ADS)

    Jutras, Mathilde; Vancoppenolle, Martin; Lourenço, Antonio; Vivier, Frédéric; Carnat, Gauthier; Madec, Gurvan; Rousset, Clément; Tison, Jean-Louis

    2016-09-01

    Snow over Antarctic sea ice is often flooded by brine or seawater, particularly in spring, forming slush and snow ice. Here, we evaluate the representation of the thermodynamics of slush and snow-ice formation in large-scale sea-ice models, using laboratory experiments (NaCl solutions poured into grated ice in an isolated container). Scaling analysis highlights latent heat as the main term of the energy budget. The temperature of the new sea ice immediately after flooding is found very close to the saltwater freezing point, whereas its bulk salinity is typically > 20 g / kg. Large-scale sea-ice models faithfully represent such physics, yet the uncertainty on the origin of flooding saltwater impacts the calculated new ice temperature, because of the different salinities of seawater and brine. The laboratory experiments also suggest a potential limitation to the existing physical representations of flooding: for brine fractions > 60 %, ice crystals start floating upon saltwater. Natural sea-ice observations suggest that the isolated system assumption holds for a few hours at most, after which rapid heat and salt exchanges mostly destroy the initial flooding signature on temperature and salinity. A small footprint on ice salinity remains however, natural snow ice is found 3-5 g/kg more saline than other forms of sea ice.

  13. 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

  14. Comparison of modelled and observed Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Bobylev, Leonid; Kuzmina, Svetlana; Johannessen, Ola M.

    2010-05-01

    When considering the climate projections one of the most important issues is how well models reproduce variability and change of the main climate parameters, e.g. sea ice. To address this issue the comparative analysis of observed and modelled sea ice coverage and thickness was performed. Modelled sea ice extent and thickness data for the comparison are represented by results of simulation runs of IPCC AR4 models. Observed data for sea ice coverage - area and extent, are Chapman and Walsh data and data from satellite passive microwave measurements available continuously since November 1978. Observed sea ice thickness data are Kwok and Rothrock data from submarines for 1975-2000 and from ICESat satellite for 2003-2008. Annual cycle of observed and modelled monthly mean sea ice extent (SIE) showed that, generally, models overestimate SIE. Disagreement between simulated and observed results is larger during late winter, spring and earlier summer. Annual cycle of observed and modelled linear trends of SIE showed that negative trend rates reach their maxima in July-August, revealing significant decreases in summer SIE. Simulated trend rates are two times smaller then observed. Thus, the observed sea ice extent decreases faster than modelled. Comparison of observed and modelled annual cycle of SIE for the different Arctic seas showed that for the Barents sea models overestimate sea ice during the whole year. For other seas models overestimate SIE only for summer and early fall. For all other seasons they underestimate Arctic sea ice. The mean differences between observed and modelled sea ice concentration in the Arctic is the largest in Barents, Kara, Laptev and East-Siberian seas and exceeds 80%. The comparison of observed and modelled sea ice thickness showed that, generally, observed values lie within the area of the model spread. But the negative trend of observed thicknesses significantly higher than that of models. So, the Arctic sea ice thickness, like its area

  15. Texture analysis of radiometric signatures of new sea ice forming in Arctic leads

    NASA Technical Reports Server (NTRS)

    Eppler, Duane T.; Farmer, L. Dennis

    1991-01-01

    Analysis of 33.6-GHz, high-resolution, passive microwave images suggests that new sea ice accumulating in open leads is characterized by a unique textural signature which can be used to discriminate new ice forming in this environment from adjacent surfaces of similar radiometric temperature. Ten training areas were selected from the data set, three of which consisted entirely of first-year ice, four entirely of multilayer ice, and three of new ice in open leads in the process of freezing. A simple gradient operator was used to characterize the radiometric texture in each training region in terms of the degree to which radiometric gradients are oriented. New ice in leads has a sufficiently high proportion of well-oriented features to distinguish it uniquely from first-year ice and multiyear ice. The predominance of well-oriented features probably reflects physical processes by which new ice accumulates in open leads. Banded structures, which are evident in aerial photographs of new ice, apparently give rise to the radiometric signature observed, in which the trend of brightness temperature gradients is aligned parallel to lead trends. First-year ice and multiyear ice, which have been subjected to a more random growth and process history, lack this banded structure and therefore are characterized by signatures in which well-aligned elements are less dominant.

  16. 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.

  17. Bayesian classification of the ice cover of the Arctic seas

    NASA Astrophysics Data System (ADS)

    Zakhvatkina, N. Yu.; Bychkova, I. A.

    2015-12-01

    A classification of sea ice in the Arctic by age (multiyear; first-year; and first-year deformed ice, nilas, etc.) is developed based on the Bayesian approach using satellite radar data and taking into account regional peculiarities of these types of ice for different sectors of the Arctic. Estimations of a priori probabilities for each ice type, which are required for the use of the Bayesian classification, are obtained by the analysis of ice charts in the Arctic seas developed at the AARI in 2008-2013 using satellite data. A posterior probabilities are estimated visually by an expert. Types of sea ice distinguished by the expert on satellite images make it possible to create sample values of the radar-scattering cross section (RSCS). Examples of the proposed Bayesian classification of ice in the Laptev Sea according to Envisat satellite data are given.

  18. 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.

  19. The CMIP6 Sea-Ice Model Intercomparison Project (SIMIP): understanding sea ice through climate-model simulations

    NASA Astrophysics Data System (ADS)

    Notz, Dirk; Jahn, Alexandra; Holland, Marika; Hunke, Elizabeth; Massonnet, François; Stroeve, Julienne; Tremblay, Bruno; Vancoppenolle, Martin

    2016-09-01

    A better understanding of the role of sea ice for the changing climate of our planet is the central aim of the diagnostic Coupled Model Intercomparison Project 6 (CMIP6)-endorsed Sea-Ice Model Intercomparison Project (SIMIP). To reach this aim, SIMIP requests sea-ice-related variables from climate-model simulations that allow for a better understanding and, ultimately, improvement of biases and errors in sea-ice simulations with large-scale climate models. This then allows us to better understand to what degree CMIP6 model simulations relate to reality, thus improving our confidence in answering sea-ice-related questions based on these simulations. Furthermore, the SIMIP protocol provides a standard for sea-ice model output that will streamline and hence simplify the analysis of the simulated sea-ice evolution in research projects independent of CMIP. To reach its aims, SIMIP provides a structured list of model output that allows for an examination of the three main budgets that govern the evolution of sea ice, namely the heat budget, the momentum budget, and the mass budget. In this contribution, we explain the aims of SIMIP in more detail and outline how its design allows us to answer some of the most pressing questions that sea ice still poses to the international climate-research community.

  20. 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

  1. 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.

  2. 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.

  3. Beaufort-Chukchi Seas summer and fall ice margin data from Seasat - Conditions with similarities to the Labrador Sea

    NASA Technical Reports Server (NTRS)

    Carsey, Frank D.; Pihos, Greg

    1989-01-01

    The margin of the sea-ice pack of the Beaufort and Chukchi Seas is examined using the microwave data from Seasat taken during the summer to early fall, July 4 through October 8, 1978, and the observations are compared to the analogous observations taken in LIMEX'87. The sensors used are synthetic-aperture radar (SAR), the Seasat-A scatterometer system, and the Scanning Multichannel Microwave Radiometer. The examination indicates that the ice edge in summer and early fall is compact; that is, in most cases the pack undergoes an abrupt change in ice concentration from zero over open water to a substantial value (over 70 percent) in the marginal ice zone. This change takes place over the space of a few kilometers. Adjacent to the edge there is a zone of intermediate ice concentration 50-100-km wide. In late summer there is a band of ice at the edge which is largely featureless in the 25-m resolution of the Seasat SAR and is taken to be ice cakes with diameters less than 100 m. Eddylike structures seem to be present in the margin on scales from 5-200 km; bands and tadpole streamers are also observable. All three instruments locate the ice edge with varying degrees of precision.

  4. Sea ice variability during the Holocene: evidence from marine and ice cores in the Ross Sea area, East Antarctica

    NASA Astrophysics Data System (ADS)

    Mezgec, Karin; Melis, Romana; Crosta, Xavier; Traversi, Rita; Severi, Mirko; Colizza, Ester; Braida, Martina; Stenni, Barbara

    2013-04-01

    High latitudes are particularly interesting places to document natural climate variability. Sea ice is an important element in the climate system because it influences bottom water formation and ocean circulation and regulates the ocean-atmosphere heat exchange. Understanding climate and environmental changes through the reconstruction of past sea ice variability, atmospheric circulation and oceanographic conditions in the Southern Ocean could represent one of the most important keys to predict with confidence future climate changes on global scale. In fact, the oceanic area surrounding Antarctica represents the main source of bottom water formation affecting the global climate through the oceanic circulation. In this study, we present an interdisciplinary proxies analysis considering marine and ice core records, as part of the ESF PolarCLIMATE HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) project, to document sea ice variability in the Ross Sea continental shelf area. Diatom assemblages from three sediment cores located in the north-western Ross Sea (Joides Basin, Cape Hallett and Wood Bay) have been studied and the sea salt Na+ (a potential proxy of sea ice) records from two ice core sites (Taylor Dome and Talos Dome) facing the Ross Sea area have been considered. The significant positive correlations among the sea ice diatom Fragilariopsis curta relative abundance and sea salt Na+ records from Talos Dome and Taylor Dome ice cores, suggest that sea salt Na+ could be used as a proxy for sea ice extent and/or duration in the Ross Sea area. These preliminary results look as a positive premise in view of integrating proxies from different realms (marine and glacial) in order to achieve a more complete view of the climate and environmental changes occurring during the Holocene. The combination of geological and glacial records will greatly improve our knowledge on paleo sea ice dynamics.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. Protists in Arctic drift and land-fast sea ice.

    PubMed

    Comeau, André M; Philippe, Benoît; Thaler, Mary; Gosselin, Michel; Poulin, Michel; Lovejoy, Connie

    2013-04-01

    Global climate change is having profound impacts on polar ice with changes in the duration and extent of both land-fast ice and drift ice, which is part of the polar ice pack. Sea ice is a distinct habitat and the morphologically identifiable sympagic community living within sea ice can be readily distinguished from pelagic species. Sympagic metazoa and diatoms have been studied extensively since they can be identified using microscopy techniques. However, non-diatom eukaryotic cells living in ice have received much less attention despite taxa such as the dinoflagellate Polarella and the cercozoan Cryothecomonas being isolated from sea ice. Other small flagellates have also been reported, suggesting complex microbial food webs. Since smaller flagellates are fragile, often poorly preserved, and are difficult for non-experts to identify, we applied high throughput tag sequencing of the V4 region of the 18S rRNA gene to investigate the eukaryotic microbiome within the ice. The sea ice communities were diverse (190 taxa) and included many heterotrophic and mixotrophic species. Dinoflagellates (43 taxa), diatoms (29 taxa) and cercozoans (12 taxa) accounted for ~80% of the sequences. The sympagic communities living within drift ice and land-fast ice harbored taxonomically distinct communities and we highlight specific taxa of dinoflagellates and diatoms that may be indicators of land-fast and drift ice.

  12. Amplification of European Little Ice Age by sea ice-ocean-atmosphere feedbacks

    NASA Astrophysics Data System (ADS)

    Lehner, Flavio; Born, Andreas; Raible, Christoph C.; Stocker, Thomas F.

    2013-04-01

    The transition from the Medieval Climate Anomaly (~950-1250 AD) to the Little Ice Age (~1400-1700 AD) is believed to have been driven by an interplay of external forcing and climate system-internal variability. While the hemispheric signal seems to have been dominated by solar irradiance and volcanic eruptions, the understanding of mechanisms shaping the climate on continental scale is less robust. Examining an ensemble of transient model simulations as well as a new type of sensitivity experiments with artificial sea ice growth, we identify a sea ice-ocean-atmosphere feedback mechanism that amplifies the Little Ice Age cooling in the North Atlantic-European region and produces the temperature pattern expected from reconstructions. Initiated by increasing negative forcing, the Arctic sea ice substantially expands at the beginning of the Little Ice Age. The excess of sea ice is exported to the subpolar North Atlantic, where it melts, thereby weakening convection of the ocean. As a consequence, northward ocean heat transport is reduced, reinforcing the expansion of the sea ice and the cooling of the Northern Hemisphere. In the Nordic Seas, sea surface height anomalies cause the oceanic recirculation to strengthen at the expense of the warm Barents Sea inflow, thereby further reinforcing sea ice growth in the Barents Sea. The absent ocean-atmosphere heat flux in the Barents Sea results in an amplified cooling over Northern Europe. The positive nature of this feedback mechanism enables sea ice to remain in an expanded state for decades to centuries and explain sustained cold periods over Europe such as the Little Ice Age. Support for the feedback mechanism comes from recent proxy reconstructions around the Nordic Seas.

  13. 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.

  14. The Effect of Excess Snow on Sea Ice in a Global Ice-Ocean Prediction System

    NASA Astrophysics Data System (ADS)

    Winter, B.; Bélair, S.; Lemieux, J. F.

    2014-12-01

    Snow cover on sea ice acts as a thermal insulator, greatly reducing the upward heat flux from the ocean through the ice, specifically through thin ice. The treatment of snow in the CICE sea ice model does not include the effects of blowing snow, thereby leading to an unrealistically thick snow layer on the ice. We investigate the consequences of this excess snow for the upward heat fluxes throughout the year, and how this impacts forecast accuracy in a global ice-ocean prediction model (GIOPS). First results will be presented, and computationally efficient solutions will be discussed.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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).

  20. Climate science: Southern Ocean freshened by sea ice

    NASA Astrophysics Data System (ADS)

    Maksym, Ted

    2016-09-01

    The Southern Ocean has become less salty during the past few decades. An analysis of sea-ice transport in the ocean suggests that this phenomenon can be explained by coupled changes in sea-ice drift and thickness. See Letter p.89

  1. Proteorhodopsin-bearing bacteria in Antarctic sea ice.

    PubMed

    Koh, Eileen Y; Atamna-Ismaeel, Nof; Martin, Andrew; Cowie, Rebecca O M; Beja, Oded; Davy, Simon K; Maas, Elizabeth W; Ryan, Ken G

    2010-09-01

    Proteorhodopsins (PRs) are widespread bacterial integral membrane proteins that function as light-driven proton pumps. Antarctic sea ice supports a complex community of autotrophic algae, heterotrophic bacteria, viruses, and protists that are an important food source for higher trophic levels in ice-covered regions of the Southern Ocean. Here, we present the first report of PR-bearing bacteria, both dormant and active, in Antarctic sea ice from a series of sites in the Ross Sea using gene-specific primers. Positive PR sequences were generated from genomic DNA at all depths in sea ice, and these sequences aligned with the classes Alphaproteobacteria, Gammaproteobacteria, and Flavobacteria. The sequences showed some similarity to previously reported PR sequences, although most of the sequences were generally distinct. Positive PR sequences were also observed from cDNA reverse transcribed from RNA isolated from sea ice samples. This finding indicates that these sequences were generated from metabolically active cells and suggests that the PR gene is functional within sea ice. Both blue-absorbing and green-absorbing forms of PRs were detected, and only a limited number of blue-absorbing forms were found and were in the midsection of the sea ice profile in this study. Questions still remain regarding the protein's ecological functions, and ultimately, field experiments will be needed to establish the ecological and functional role of PRs in the sea ice ecosystem.

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

    NASA Astrophysics Data System (ADS)

    Tucker, W. B.; 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.

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

    USGS Publications Warehouse

    Tucker, W. B.; 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.

  4. Climate and sea ice variability in the SW Labrador Sea during the late Holocene

    NASA Astrophysics Data System (ADS)

    Weckström, Kaarina; Massé, Guillaume; Collins, Lewis; Sicre, Marie-Alexandrine; Bouloubassi, Ioanna; Seidenkrantz, Marit-Solveig; Olsen, Jesper; Kuijpers, Antoon

    2014-05-01

    The recent rapid decline in Arctic sea ice cover has increased the need to improve the accuracy of the sea ice components in climate models and to provide detailed long-term sea ice records based on proxy data. Recently, the highly branched isoprenoid IP25 has emerged as a potential sea ice specific proxy for past sea ice cover, found in marine sediments underlying seasonal sea ice. We tested the reliability of this biomarker against observational sea ice data off Newfoundland (SW Labrador Sea), where box cores covering the last ca. 100-150 years were collected. Based on the results, IP25 proved to be a robust and reliable proxy for reconstructing variability in past sea ice concentrations in the area. After having successfully validated the proxy in the SW Labrador Sea, we further analysed IP25 from a sediment core NE of Newfoundland covering the last ca. 5000 years, providing the southernmost multi-millennial record of this proxy to date. Based on this record and on diatom and dinoflagellate cyst data and alkenone-based sea surface temperatures (SSTs) from the same core, we reconstructed climatic conditions in and Arctic sea ice export to the SW Labrador Sea area: Alkenone-based SSTs show a clear albeit variable decline after the Holocene Climate Optimum, while at the same time diatom and dinoflagellate cyst data suggest decreased melt water export from the Arctic. The IP25 record reveals increased sea ice export from the Baffin and Hudson Bays starting ca 1500 yr cal. BP, accelerating ca. 800 yr cal. BP and culminating at the height of the Little Ice Age. Sea ice export during the last century is comparable to the export during the Medieval Climate Anomaly.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    USGS Publications Warehouse

    Tsai, V.C.; McNamara, D.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. Copyright 2011 by the American Geophysical Union.

  13. 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.

  14. Physical Characteristics and Geobiology of 'Rotten' Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Frantz, C. M.; Light, B.; Orellana, M. V.; Carpenter, S.; Junge, K.

    2015-12-01

    Arctic sea ice in its final stage of demise, "rotten ice", is characterized by seriously compromised structural integrity, making it difficult to collect and study. Consequently, little is known about the physical, chemical and biological properties of this ice type. Yet, as the Arctic melt season lengthens, this ice type will likely appear sooner and become more prevalent in the Arctic Ocean and its occurrence may be more common than satellite mapping and ice charts suggest (e.g., Barber et al., 2009). Here we present physical, chemical, biological, and optical measurements of first-year ice near Barrow, Alaska during the spring and summer of 2015. Samples represent a progression from solid, "springtime" shorefast ice (May); through melting, heavily melt-ponded, "summertime" shorefast ice (June); to the final stage of barely-intact, "rotten" ice collected from small floes Beaufort Sea (July). Results indicate that rotten ice exhibits low salinity, is well drained and has a lower density than its springtime counterpart. X-ray tomography of dimethyl phthalate-casted sea ice samples indicates differences in porosity and relative permeability in rotten ice vs. spring- and summertime ice. We also present a preliminary characterization of rotten sea ice as a microbial habitat using preliminary results of chemical measurements (nutrients, dissolved organic and inorganic carbon), and microbiological characterizations (concentrations and16S/18S rDNA-based identifications) from seawater vs. sea ice vs. sea ice brines. Optical measurements show that while decreased ice thickness and increased melt pond coverage cause an overall increase in solar radiation to the ocean as sea ice warms, rotten ice is actually less transparent to solar radiation than its spring- and summertime counterparts. These factors determine solar heating in the ocean and, ultimately, the potential for accelerated ice melting (e.g., Light et al., 2008). This work provides a foundation for understanding

  15. 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.

  16. 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

  17. In situ observations of wave-induced sea ice breakup

    NASA Astrophysics Data System (ADS)

    Kohout, A. L.; Williams, M. J. M.; Toyota, T.; Lieser, J.; Hutchings, J.

    2016-09-01

    Ocean waves can propagate hundreds of kilometers into sea ice, leaving behind a wake of broken ice floes. Three floe breakup events were observed during the second Sea Ice Physics and Ecosystem Experiment (SIPEX-2). We show that the three breakup events were likely influenced by ocean waves. We compare the observations to a wave induced floe breakup model which includes an empirical wave attenuation model, and show that the model underestimates the extent of floe breaking for long period waves.

  18. 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.

  19. Does ice float in Titan’s lakes and seas?

    NASA Astrophysics Data System (ADS)

    Hofgartner, Jason D.; Lunine, Jonathan I.

    2013-03-01

    We model Titan’s lakes and seas as methane-ethane-nitrogen systems and model the buoyancy of solids in these systems assuming thermodynamic equilibrium. We find that ice will float in methane-rich lakes for all temperatures below the freezing point of pure methane and that ice will also float in ethane-rich seas provided the ice has an air porosity of greater than 5% by volume.

  20. 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.

  1. The influence of sea ice extent variability on the Greenland surface mass and energy balance

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Quillet, A.; Alexander, P. M.; Rennermalm, A. K.; Stroeve, J. C.; Fettweis, X.; Orantes, E. J.; Tuia, D.; Parkan, M.

    2012-12-01

    Sea ice variations are known to affect local surface air temperature regimes, but other influences, in particular atmospheric circulation, are important. Several recent studies have found that, via atmospheric transport, atmospheric warming driven by sea ice loss affects surrounding areas. Indeed, while observed amplified autumn warming is focused over the areas where the sea ice has disappeared in summers (e.g. Beaufort, Chukchi and E. Siberian seas), wind patterns spread the anomalous warmth over open water areas to adjacent land areas and may extend up to 1500 km inland during periods of rapid ice loss through the 21st century. It is plausible that changes in the sea-ice/open- water regime surrounding the ice sheet are capable of modulating Greenland surface melt and precipitation. Diminished sea ice around Greenland may lead to large fluxes of heat into the atmosphere that could lead to enhanced ice-sheet surface-melt, increased coastal water temperatures, alter the vertical stability of the atmosphere, moisture availability and regional baroclinicity. Here we report results concerning the combined analysis of sea ice extent estimated from spaceborne microwave observations, the outputs of a regional climate model (Modèle Atmosphérique Régional, MAR) and in-situ measured quantities. In particular, we study the impact of the open water along the coasts of Greenland (divided into 16 longitudinal zones and two latitudinal ones) on surface mass balance (e.g., meltwater production, runoff, precipitation) and surface energy quantities (e.g., albedo, sensible heat flux, etc.) simulated over the Greenland ice sheet for the period 1979 - 2011. Among other things, our results indicate a statistically significant correlation between open water spatio-temporal variability and integrated liquid water content, with correlation values being highest for the month of August along the Southwest region of Greenland (e.g., Kangerlussuaq). Such dependency persists even after the

  2. 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

  3. 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.

  4. Ice-gouged microrelief on the floor of the eastern Chukchi Sea, Alaska: a reconnaissance survey

    USGS Publications Warehouse

    Toimil, Lawrence J.

    1978-01-01

    Side-scan sonar and bathymetric records obtained from 1,800 km of trackline from the eastern Chukchi Sea continental shelf, between water depths of 20 and 70 m show the ubiquitous presence of furrow-like linear depressions produced by gouging of the sea bed by ice keels. These sea bed micro-features are regionally widespread but are not uniformly distributed. Furthermore, the microrelief, texture, and lithologic structure of sea bed sediments have been significantly modified by the disruptive processes associated with ice gouge formation. An analysis of some 10,.200 individual gouges shows that the density of ice gouges increases with increasing latitude, increasing slope gradients, and decreasing water depth. Across the northern half of the shelf few trackline segments are free of ice gouges; in the southern portion numerous segments contain no ice gouges. However, ice gouges extend at least as far south as Cape Prince of Wales Shoal. Densities of over 200 gouges per km of trackline are not uncommon in water depths less than 30 m ,but no values higher than 50 km are encountered in water deeper than 50 m. No ice gouges have been observed in water depths exceeding 58 m. Saturation ice gouge densities (greater than 300/Pan) occur along the eastern side 6f Barrow Sea Valley and the northeast flank of Hanna Shoal. Maximum gouge incision depths per km of trackline are greatest in water 36 to 50 m deep . A maximum incision depth of 4.5 m occurs in the 35-40 m water depth interval. Individual ice gouge events wider than 100 m, most produced by multi-keeled ice fragments, are found between 31 and 45 m depths. The dominant azimuth of gouge furrows shows no preferred orientation on the Chukchi Sea shelf; only locally does bathmetric control of the trend of gouges appear. The occurrence of current-produced bedforms within individual ice gouges suggests an interaction between slow-moving grounded or gouging ice keels and swift currents. In other cases, current

  5. 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.

  6. Spatial Variability of Barrow-Area Shore-Fast Sea Ice and Its Relationships to Passive Microwave Emissivity

    NASA Technical Reports Server (NTRS)

    Maslanik, J. A.; Rivas, M. Belmonte; Holmgren, J.; Gasiewski, A. J.; Heinrichs, J. F.; Stroeve, J. C.; Klein, M.; Markus, T.; Perovich, D. K.; Sonntag, J. G.; Tape, K.

    2006-01-01

    Aircraft-acquired passive microwave data, laser radar height observations, RADARSAT synthetic aperture radar imagery, and in situ measurements obtained during the AMSR-Ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales. The data fusion allows delineation of the shore-fast ice and pack ice in the Barrow area, AK, into several ice classes. Results show good agreement between observed and Polarimetric Scanning Radiometer (PSR)-derived snow depths over relatively smooth ice, with larger differences over ridged and rubbled ice. The PSR results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness, ridging, and other factors such as ice age. Apparent relationships exist between ice roughness and the degree of depolarization of emission at 10,19, and 37 GHz. This depolarization .would yield overestimates of total ice concentration using polarization-based algorithms, with indications of this seen when the NT-2 algorithm is applied to the PSR data. Other characteristics of the microwave data, such as effects of grounding of sea ice and large contrast between sea ice and adjacent land, are also apparent in the PSR data. Overall, the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity.

  7. 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.

  8. 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.

  9. 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.

  10. Correlation of sea level falls interpreted from atoll stratigraphy with turbidites in adjacent basins

    SciTech Connect

    Lincoln, J.M. )

    1990-05-01

    Past sea levels can be derived from any atoll subsurface sediments deposited at or near sea level by determining the ages of deposition and correcting the present depths to the sediments for subsidence of the underlying edifice since the times of deposition. A sea level curve constructed by this method consists of discontinuous segments, each corresponding to a period of rising relative sea level and deposition of a discrete sedimentary package. Discontinuities in the sea level curve derived by this method correspond to relative sea level falls and stratigraphic hiatuses in the atoll subsurface. During intervals of relative sea level fall an atoll emerges to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence without depositing sediments on top of the atoll. Furthermore, subaerial erosion may remove a substantial part of the depositional record of previous sea level fluctuations. For these reasons the authors must look to the adjacent basins to complement the incomplete record of sea level change recorded beneath atolls. During lowstands of sea level, faunas originally deposited near sea level on an atoll may be eroded and redeposited as turbidites in deep adjacent basins. Three such turbidites penetrated during deep-sea drilling at Sites 462 and 315 in the central Pacific correlate well with a late Tertiary sea level curve based on biostratigraphic ages and {sup 87}Sr/{sup 86}Sr chronostratigraphy for core from Enewetak Atoll in the northern Marshall Islands. Further drilling of the archipelagic aprons adjacent to atolls will improve the sea level history that may be inferred from atoll stratigraphy.

  11. Sea-bird affinities for ocean and ice boundaries in the Antarctic

    NASA Astrophysics Data System (ADS)

    Ainley, David G.; Jacobs, Stanley S.

    1981-10-01

    We have observed more sea birds near the Ross Sea continental slope and near ice than over the adjacent continental shelf, deep ocean, and ice-free regions. Bird concentrations near the continental margin occurred above th subsurface Antarctic Slope Front, defined by increased horizontal gradients in water temperature, salinity, density, chemistry, color, and transparency. A convergence between easterly and westerly currents near the continental shelf break may accumulate plankton and other positively bouyant material from oceanic gyres to the north and south. In addition, some sea-bird prey are believed to have life cycles adapted to the continental margin regime of upwelling deep water and sinking shelf water. Order-of-magnitude changes in bird abundance over relatively small distances indicate the importance of hydrographic and cryographic features to sea-bird distributions in the Southern Ocean.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. NASA IceBridge: Airborne surveys of the polar sea ice covers

    NASA Astrophysics Data System (ADS)

    Richter-Menge, J.; Farrell, S. L.

    2014-12-01

    The NASA Operation IceBridge (OIB) airborne sea ice surveys are designed to continue a valuable series of sea ice thickness measurements by bridging the gap between NASA's Ice, 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. Primary OIB sensors being used for sea ice observations include the Airborne Topographic Mapper laser altimeter, 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 campaigns and highlight key scientific accomplishments, which include: • Documented changes in the Arctic marine cryosphere since the dramatic sea ice loss of 2007 • Novel snow depth measurements over sea ice in the Arctic • Improved skill of April-to-September sea ice predictions via numerical ice/ocean models • Validation of satellite altimetry measurements (ICESat, CryoSat-2, and IceSat-2/MABEL)

  17. 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.

  18. 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

  19. High resolution modelling of the decreasing Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Madsen, K. S.; Rasmussen, T. A. S.; Blüthgen, J.; Ribergaard, M. H.

    2012-04-01

    The Arctic sea ice cover has been rapidly decreasing and thinning over the last decade, with minimum ice extent in 2007 and almost as low extent in 2011. This study investigates two aspects of the decreasing ice cover; first the large scale thinning and changing dynamics of the polar sea ice, and secondly oceanic oil drift in ice affected conditions. Both investigations are made with the coupled ocean - sea ice model HYCOM-CICE at 10 km resolution, which is also used operationally at DMI and allows detailed studies of sea ice build-up, drift and melt. To investigate the sea ice decrease of the last decade, we have performed a reanalysis simulation of the years 1990-2011, forced with ERA Interim atmospheric data. Thus, the simulation includes both the period before the recent sea ice decrease and the full period of decrease up till today. We will present our model results of the thinning and changing dynamics and discuss how they relate to satellite observations. The relation to the upper ocean heat content is also investigated. The decreasing sea ice has opened up for increased ship traffic and oil exploration in the polar oceans. To avoid damage on the pristine Arctic ecosystem, this requires careful environmental assessments. Here, one important tool is to investigate how a possible oil spill will drift and disperse. Through an ensemble of simulations, we will demonstrate the drift of imaginary spills off the Greenlandic coast for both a release at the surface and the in the deep ocean, and it will be discussed how sea ice affects the drift.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. Sea ice properties in the Bohai Sea measured by MODIS-Aqua: 2. Study of sea ice seasonal and interannual variability

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Wang, Menghua

    2012-07-01

    During the 2009-2010 winter, the Bohai Sea experienced its most severe sea ice event in four decades, which caused significant economic losses, affected marine transportation and fishery, and impacted the entire marine ecosystem in the region. Measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite from 2002 to 2010 and surface atmosphere temperature (SAT) data from the National Centers for Environmental Prediction (NCEP) are used to study and quantify the extreme sea ice event in the 2009-2010 winter and the interannual variability of the regional sea ice properties, as well as the relationship between sea ice and the climate variability in the Bohai Sea. The mean sea ice reflectance from MODIS-Aqua visible and near-infrared wavelengths are 9.33%, 13.26%, and 12.60% in the months of December 2009, January 2010, and February 2010, respectively, compared with the monthly average sea ice reflectance values (from 2002 to 2010) of 9.35%, 11.21%, and 11.41% in the same three winter months. The sea ice monthly average coverages are ~ 5427, ~ 27,414, and ~ 21,156 km2 in these three winter months. These values are significantly higher than the averages of monthly sea ice coverage of ~ 2735, ~ 11,119, and ~ 10,287 km2 in the Bohai Sea in December, January, and February between 2002 and 2010. Most of the sea ice coverage was located in the northern Bohai Sea. Both the intra-seasonal and interannual sea ice variability in the Bohai Sea is found to be related closely to SAT. The mechanism of anomalous SAT and intense sea ice severity are also discussed and attributed to large-scale climate changes due to the variability of the Arctic Oscillation (AO) and Siberian High (SH).

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

    USGS Publications Warehouse

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

    2002-01-01

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

  6. 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.

  7. Coincident vortices in Antarctic wind fields and sea ice motion

    NASA Astrophysics Data System (ADS)

    Wassermann, S.; Schmitt, C.; Kottmeier, C.; Simmonds, I.

    2006-08-01

    This study introduces a method to examine the coincidence of rotational ice drift and winds caused by the forcing of ice motion by Antarctic cyclones. Vortices are automatically detected using the algorithm of Murray and Simmonds (1991) from both ECMWF surface pressures and SSM/I sea ice motions. For compatibility with this algorithm sea ice motion vectors are transformed to a scalar stream function. During a seven-day test period positions of pressure minima and stream function maxima (SFM) of ice drift are within 300 km in 96% of the cases. Lowest pressure minima are related to highest stream function maxima. The results promise the method to provide a complementary tool of detecting and localizing low-pressure systems over sea ice, adding to numerical pressure analyses.

  8. 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.

  9. A Lagrangian analysis of sea ice dynamics in the Arctic

    NASA Astrophysics Data System (ADS)

    Szanyi, S.; Lukovich, J. V.; Haller, G.; Barber, D. G.

    2014-12-01

    Recent studies have highlighted acceleration in sea ice drift and deformation in the Arctic over the last several decades, underlining the need for improved understanding of sea ice dynamics and dispersion. In this study we present Lagrangian diagnostics to quantify changes in the dynamical characteristics of the Arctic sea ice cover from 1979 to 2012 during the transition from a predominantly multi-year to a first-year ice regime. Examined in particular is the evolution in finite-time Lyapunov exponents (FTLEs), which monitor the rate at which neighboring particle trajectories diverge, and stretching rates throughout the Arctic. In this analysis we compute FTLEs for the Arctic ice drift field using National Snow and Ice Data Centre (NSIDC) Polar Pathfinder Daily 25 km EASE-Grid weekly sea ice motion vectors for the annual cycle beginning both from the sea ice minimum in September, and maximum in March. Sensitivity analyses show that maximal FTLEs, or ridges, are robust even with the introduction of significant noise. Probability density functions and mean values of FTLEs show a trend towards higher FTLE values characteristic of increased mixing in the Arctic in the last decade, in keeping with a transition to a weaker, thinner ice cover.

  10. 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.

  11. 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.

  12. Sea ice climatology, variations and teleconnections: Observational and modeling studies

    NASA Astrophysics Data System (ADS)

    Liu, Jiping

    Hypotheses, models and observations suggest that sea ice plays an important role in the local, regional and global climate through a variety of processes across a full range of scales. However, our documentation and understanding of the nature of the polar-extrapolar climate teleconnections and their underlying causal and mechanistic links are still rudimentary, and the largest disagreements among model simulations of present and future climate are in the polar regions. In an effort to address these issues, we evaluated the simulated Antarctic sea ice variability and its climate teleconnections in three coupled global climate models (GISS, NCAR and GFDL) as compared to the observations. All the models capture the El Nino-Southern Oscillation (ENSO)-like phenomenon to some degree, although almost all the models miss some observed linkages. The GISS and NCAR models also capture the observed Antarctic Dipole and meridional banding structure through the Pacific. The Antarctic sea ice regions showing the strongest sensitivity to global teleconnections differ among the models and between the models and observations. We then proposed that the changes of the regional mean meridional atmospheric circulation (the regional Ferrel Cell) are one such mechanism leading to the covariability of the ENSO and Antarctic Dipole by modulating the mean meridional heat flux using the observational data. To more accurately represent sea ice simulations and associated feedbacks with the atmosphere and the ocean, the GISS coupled model was used to investigate the sensitivity of sea ice to the following physical parameterizations: (a) two sea ice dynamics (cavitating fluid and viscous-plastic), (b) the specification of oceanic isopyncal mixing coefficients in the Gent and McWillams isopyncal mixing, (c) the Wajsowicz viscosity diffusion, (d) surface albedo, (e) the penetration of solar radiation in sea ice, (f) effects of including a sea ice salinity budget, and (g) the ice-ocean boundary

  13. 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

  14. 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.

  15. A dynamical model of Kara Sea land-fast ice

    NASA Astrophysics Data System (ADS)

    Olason, Einar

    2016-05-01

    This paper introduces modifications to the traditional viscous-plastic sea-ice dynamical model, which are necessary to model land-fast ice in the Kara Sea in a realistic manner. The most important modifications are an increase in the maximum viscosity from the standard value of ζmax=>(2.5×108s>)P to ζmax=>(1013s>)P, and to use a solver for the momentum equation capable of correctly solving for small ice velocities (the limit here is set to 10-4 m/s). Given these modifications, a necessary condition for a realistic fast-ice simulation is that the yield curve give sufficient uniaxial compressive strength. This is consistent with the idea that land-fast ice in the Kara Sea forms primarily via static arching. The modified model is tested and tuned using forcing data and observations from 1997 and 1998. The results show that it is possible to model land-fast ice using this model with the modifications mentioned above. The model performs well in terms of modeled fast-ice extent, but suffers from unrealistic break-ups during the start and end of the fast-ice season. The main results are that fast ice in the Kara Sea is supported by arching of the ice, the arches footers resting on a chain of islands off shore.

  16. SEA-ICE INFLUENCE ON ARCTIC COASTAL RETREAT.

    USGS Publications Warehouse

    Reimnitz, Erk; Barnes, P.W.

    1987-01-01

    Recent studies document the effectiveness of sea ice in reshaping the seafloor of the inner shelf into sharp-relief features, including ice gouges with jagged flanking ridges, ice-wallow relief, and 2- to 6-m-deep strudel-scour craters. These ice-related relief forms are in disequilibrium with classic open-water hydraulic processes and thus are smoothed over by waves and currents in one to two years. Such alternate reworking of the shelf by ice and currents - two diverse types of processes, which in the case of ice wallow act in unison-contributes to sediment mobility and, thus, to sediment loss from the coast and inner shelf. The bulldozing action by ice results in coast-parallel sediment displacement. Additionally, suspension of sediment by frazil and anchor ice, followed by ice rafting, can move large amounts of bottom-derived materials. Our understanding of all these processes is insufficient to model Arctic coastal processes.

  17. Atmospheric mercury over sea ice during the OASIS-2009 campaign

    NASA Astrophysics Data System (ADS)

    Steffen, A.; Bottenheim, J.; Cole, A.; Douglas, T. A.; Ebinghaus, R.; Friess, U.; Netcheva, S.; Nghiem, S.; Sihler, H.; Staebler, R.

    2013-03-01

    Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected on sea ice near open leads in the Beaufort Sea near Barrow, Alaska in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) International Polar Year Program. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg over the sea ice averaged 393.5 pg m-3 (range 47.1-900.1 pg m-3) during the two week long study. RGM concentrations averaged 30.1 pg m-3 (range 3.5-105.4 pg m-3). The mean GEM concentration of 0.59 ng m-3 during the entire study (range 0.01-1.51 ng m-3) was depleted compared to annual Arctic ambient boundary layer concentrations. It was shown that when ozone (O3) and bromine oxide (BrO) chemistry are active there is a~linear relationship between GEM, PHg and O3 but there was no correlation between RGM and O3. There was a linear relationship between RGM and BrO and our results suggest that the origin and age of air masses play a role in determining this relationship. These results were the first direct measurements of these atmospheric components over the sea ice. For the first time, GEM was measured simultaneously over the tundra and the sea ice. The results show a significant difference in the magnitude of the emission of GEM from the two locations where significantly higher emission occurs over the tundra. Elevated chloride levels in snow over sea ice are believed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of Hg(II) to Hg(0) (GEM) in snow. These results are important because while GEM is emitted after depletion events on snow inland, less GEM is emitted over sea ice. Since the snow pack on sea ice retains more mercury than inland snow current models of the Arctic mercury cycle, which are based predominantly on land based measurements, may greatly underestimate

  18. 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.

  19. 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.

  20. 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.

  1. Influence of diet and sea ice drift on organochlorine bioaccumulation in Arctic ice-associated amphipods.

    PubMed

    Borgå, K; Poltermann, M; Polder, A; Pavlova, O; Gulliksen, B; Gabrielsen, G W; Skaare, J U

    2002-01-01

    The drifting sea ice has been suggested as important in the transport and concentration of organic matter and pollutants in the Arctic. We collected sea ice-associated amphipods in the marginal ice zone north of Svalbard and in the Fram Strait in September 1998 and 1999 to assess contaminant accumulation in ice-associated organisms. Organochlorine concentrations increased from the more herbivorous Apherusa glacialis to the more carnivorous Gammarus wilkitzkii and the more necrophagous Onisimus spp. The relative contribution of compound classes to the sum of organochlorines differed between the amphipod families, with a higher relative contribution of hexachlorocyclohexanes (HCHs) in A. glacialis. The composition of the compound classes HCHs. chlordanes and dichlorodiphenyltrichloroethanes (DDTs) was similar between the amphipod families, whereas the profiles of polychlorinated biphenyls (PCBs) differed. The occurrence of organochlorines differed spatially, with higher alpha-HCH concentrations in amphipods from the Fram Strait in comparison with amphipods collected north of Svalbard. This could be related to the sea ice drift route, since sea ice in the Fram Strait had a drift route across the central Arctic Ocean, while the sea ice north of Svalbard had a western drift route to the sampling stations. Even though marine invertebrates have direct uptake by passive diffusion of contaminants across their gills. our results imply that the species' ecology such as diet is important in the bioaccumulation process of organic pollutants. In addition, the results show that sea ice drift route influences the concentrations of organochlorine pollutants in ice-associated organisms.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Mercury Export from Mainland China to Adjacent Seas and Its Influence on the Marine Mercury Balance.

    PubMed

    Liu, Maodian; Chen, Long; Wang, Xuejun; Zhang, Wei; Tong, Yindong; Ou, Langbo; Xie, Han; Shen, Huizhong; Ye, Xuejie; Deng, Chunyan; Wang, Huanhuan

    2016-06-21

    Exports from mainland China are a significant source of mercury (Hg) in the adjacent seas (Bohai Sea, Yellow Sea, East China Sea, and South China Sea) near China. A total of 240 ± 23 Mg was contributed in 2012 (30% from natural sources and 70% from anthropogenic sources), including Hg from rivers, industrial wastewater, domestic sewage, groundwater, nonpoint sources, and coastal erosion. Among the various sources, the Hg from rivers amounts to 160 ± 21 Mg and plays a dominant role. The Hg that is exported from mainland China increased from 1984 to 2013; the contributions from rivers, industrial wastewater, domestic sewage and groundwater increased, and the contributions from nonpoint sources and coastal erosion remained stable. A box model is constructed to simulate the mass balance of Hg in these seas and quantify the sources, sinks and Hg biogeochemical cycle in the seas. In total, 160 Mg of Hg was transported to the Pacific Ocean and other oceans from these seas through oceanic currents in 2012, which could have negative impacts on the marine ecosystem. A prediction of the changes in Hg exportation through 2030 shows that the impacts of terrestrial export might worsen without effective pollution reduction measures and that the Hg load in these seas will increase, especially in the seawater of the Bohai Sea, Yellow Sea, and East China Sea and in the sea margin sediments of the Bohai Sea and East China Sea. PMID:27243109

  12. Mercury Export from Mainland China to Adjacent Seas and Its Influence on the Marine Mercury Balance.

    PubMed

    Liu, Maodian; Chen, Long; Wang, Xuejun; Zhang, Wei; Tong, Yindong; Ou, Langbo; Xie, Han; Shen, Huizhong; Ye, Xuejie; Deng, Chunyan; Wang, Huanhuan

    2016-06-21

    Exports from mainland China are a significant source of mercury (Hg) in the adjacent seas (Bohai Sea, Yellow Sea, East China Sea, and South China Sea) near China. A total of 240 ± 23 Mg was contributed in 2012 (30% from natural sources and 70% from anthropogenic sources), including Hg from rivers, industrial wastewater, domestic sewage, groundwater, nonpoint sources, and coastal erosion. Among the various sources, the Hg from rivers amounts to 160 ± 21 Mg and plays a dominant role. The Hg that is exported from mainland China increased from 1984 to 2013; the contributions from rivers, industrial wastewater, domestic sewage and groundwater increased, and the contributions from nonpoint sources and coastal erosion remained stable. A box model is constructed to simulate the mass balance of Hg in these seas and quantify the sources, sinks and Hg biogeochemical cycle in the seas. In total, 160 Mg of Hg was transported to the Pacific Ocean and other oceans from these seas through oceanic currents in 2012, which could have negative impacts on the marine ecosystem. A prediction of the changes in Hg exportation through 2030 shows that the impacts of terrestrial export might worsen without effective pollution reduction measures and that the Hg load in these seas will increase, especially in the seawater of the Bohai Sea, Yellow Sea, and East China Sea and in the sea margin sediments of the Bohai Sea and East China Sea.

  13. 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.

  14. 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.

  15. 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.

  16. Antarctic snow and sea ice processes: Effects on passive microwave emissions and AMSR-E sea ice products

    NASA Astrophysics Data System (ADS)

    Lewis, Michael John, Jr.

    In this research, passive microwave remote sensing products generated for the Antarctic sea ice zone from the Advance Microwave Scanning Radiometer-Earth Observing System (AMSR-E) sensor were compared with various in situ field measurements, both from previous Antarctic campaigns in the published literature and as obtained during the Sea Ice Mass Balance in the Antarctic (SIMBA) project during the International Polar Year (IPY) 2007--2008. Data gathered during the SIMBA project was used to understand the geophysical processes occurring in the sea ice and snow cover of the Bellingshausen Sea and to provide a physical basis for modeling of microwave emissions. In Chapter 2, the AMSR-E sea ice temperature product was compared with AMSR-E snow depth product and previous in situ field measurements. The comparisons were not intended to provide a strict validation of remote sensing products, but to evaluate the physical context of the remotely sensed data and examine potential trends. From examination of the data, it was found that the AMSR-E sea ice temperature product conflicted with several generally observed sea ice properties. The apparent contradictory behavior of the satellite data product is indicative of radiative temperature behavior related to changes in emissivity within the ice pack. Further comparisons of the AMSR-E sea ice temperature product with in situ temperature data from Ice Mass-balance Buoys (IMB) from two Antarctic field programs showed no correlation. However, apparent response of sea ice temperature product to snow/ice interface flooding events was noted. In Chapter 3, an important sea ice process related to the formation of "gap layers" within Antarctic sea ice was examined and modeled. Gap layers are horizontal voids that develop internally within the sea ice structure, often filled with decaying sea ice, saline slush, and a microbial biological community that thrives on the available nutrients. Gap layers are commonly observed in summer melt

  17. 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.

  18. Modelling land-fast sea ice using a linear elastic model

    NASA Astrophysics Data System (ADS)

    Plante, Mathieu; Tremblay, Bruno

    2016-04-01

    Land-fast ice is an important component of the Arctic system, capping the coastal Arctic waters for most of the year and exerting a large influence on ocean-atmosphere heat exchanges. Yet, the accurate representation of land-fast ice in most large-scale sea ice models remains a challenge, part due to the difficult (and sometimes non-physical) parametrisation of ice fracture. In this study, a linear elastic model is developed to investigate the internal stresses induced by the wind forcing on the land-fast ice, modelled as a 2D elastic plate. The model simulates ice fracture by the implementation of a damage coefficient which causes a local reduction in internal stress. This results in a cascade propagation of damage, simulating the ice fracture that determines the position of the land-fast ice edge. The modelled land-fast ice cover is sensitive to the choice of failure criterion. The parametrised cohesion, tensile and compressive strength and the relationship with the land-fast ice stability is discussed. To estimate the large scale mechanical properties of land-fast ice, these results are compared to a set of land-fast ice break up events and ice bridge formations observed in the Siberian Arctic. These events are identified using brightness temperature imagery from the MODIS (Moderate Resolution Imaging Spectroradiometer) Terra and Aqua satellites, from which the position of the flaw lead is identifiable by the opening of polynyi adjacent to the land-fast ice edge. The shape of the land-fast ice before, during and after these events, along with the characteristic scale of the resulting ice floes, are compared to the model results to extrapolate the stress state that corresponds to these observations. The model setting that best reproduce the scale of the observed break up events is used to provide an estimation of the strength of the ice relative to the wind forcing. These results will then be used to investigate the relationship between the ice thickness and the

  19. Sensitivity of Antarctic sea ice to form drag parameterization

    NASA Astrophysics Data System (ADS)

    Barbic, Gaia; Tsamados, Michel; Petty, Alek; Schroeder, David; Holland, Paul; Feltham, Daniel

    2014-05-01

    A new drag parametrization accounting explicitly for form drag has been recently formulated and applied to the Arctic sea ice (Lupkes et al, 2012 and Tsamados et al, 2014). We summarize here the fundamental elements of this formulation and we then adapt it to the Antarctic sea ice. Considering the general expression of the momentum balance of sea ice, we analyze the total (neutral) drag coefficients by studying separately air-ice and ocean-ice momentum fluxes, and by introducing the parameterization for both the atmospheric neutral drag coeffcient (ANDC) and the oceanic neutral drag coeffcient (ONDC). The two coefficients are calculated as a sum of their skin frictional contribution and form drag contribution, which comes from ridges and floe edges for the ANDC and keels and floe edges for the ONDC. Due to the contrasting geography of the two polar regions, there are important differences, both dynamic and thermodynamic, between Arctic and Antarctic sea ice. In the Antarctic, sea ice is younger, less ridged (hence thinner and smoother). Due to the intense snowfalls, the snow cover is generally thicker than in the Arctic, with values that vary significantly both seasonally and regionally and can affect the roughness of the surface and can lead to flooding of the ice. At the outer boundary of the Southern Ocean, the ice is unconstrained by land, divergent and subject to meridional advection, which leads to a much faster ice drift than in the Arctic. We show here how the new parameterization accounting for form drag influences the Antarctic sea ice characteristics.

  20. 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.

  1. 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.

  2. 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.

  3. Holocene Sea Surface and Subsurface Water Mass Variability Reconstructed from Temperature and Sea-ice Proxies in Fram Strait

    NASA Astrophysics Data System (ADS)

    Werner, Kirstin; Spielhagen, Robert F.; Müller, Juliane; Husum, Katrine; Kandiano, Evgenia S.; Polyak, Leonid

    2016-04-01

    In two high-resolution sediment cores from the West Spitsbergen continental margin we investigated planktic foraminiferal, biomarker and dinocyst proxy data in order to reconstruct surface and subsurface water mass variability during the Holocene. The two study sites are today influenced by northward flowing warm and saline Atlantic Water. Both foraminiferal and dinocyst (de Vernal et al., 2013) temperature reconstructions indicate a less-stratified, ice-free, nutrient-rich summer surface ocean with strong Atlantic Water advection between 10.6 and 8.5 cal ka BP, likely related to maximum July insolation during the early Holocene. Sea surface to subsurface water temperatures of up to 6°C prevailed until ca 5 cal ka BP. A weakened contribution of Atlantic Water is found when subsurface temperatures strongly decreased with minimum values between ca 4 and 3 cal ka BP. High planktic foraminifer shell fragmentation and increased oxygen isotope values of the subpolar planktic foraminifer species Turborotalita quinqueloba as well as increasing concentrations of the sea ice biomarker IP25 further indicate cool conditions. Indices associated with IP25 as well as dinocyst data suggest a sustained cooling and consequently sea-ice increase during the late Holocene. However, planktic foraminiferal data indicate a slight return of stronger subsurface influx of Atlantic Water since ca 3 cal ka BP. The observed decoupling of cooling surface and warming subsurface waters during the later Holocene might be attributed to a strong pycnocline layer separating cold sea-ice fed surface waters from enhanced subsurface Atlantic Water advection. Reference: de Vernal, A., Hillaire-Marcel, C., Rochon, A., Fréchette, B., Henry, M., Solignac, S., Bonnet, S., 2013. Dinocyst-based reconstructions of sea ice cover concentration during the Holocene in the Arctic Ocean, the northern North Atlantic Ocean and its adjacent seas. Quaternary Science Reviews 79, 111-121.

  4. Ice volume and sea level during the last interglacial.

    PubMed

    Dutton, A; Lambeck, K

    2012-07-13

    During the last interglacial period, ~125,000 years ago, sea level was at least several meters higher than at present, with substantial variability observed for peak sea level at geographically diverse sites. Speculation that the West Antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice-sheet dynamics during this time interval. We provide an internally consistent database of coral U-Th ages to assess last interglacial sea-level observations in the context of isostatic modeling and stratigraphic evidence. These data indicate that global (eustatic) sea level peaked 5.5 to 9 meters above present sea level, requiring smaller ice sheets in both Greenland and Antarctica relative to today and indicating strong sea-level sensitivity to small changes in radiative forcing.

  5. Arctic Sea ice studies with passive microwave satellite observations

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.

    1988-01-01

    The objectives of this research are: (1) to improve sea ice concentration determinations from passive microwave space observations; (2) to study the role of Arctic polynyas in the production of sea ice and the associated salinization of Arctic shelf water; and (3) to study large scale sea ice variability in the polar oceans. The strategy is to analyze existing data sets and data acquired from both the DMSP SSM/I and recently completed aircraft underflights. Special attention will be given the high resolution 85.5 GHz SSM/I channels for application to thin ice algorithms and processes studies. Analysis of aircraft and satellite data sets is expected to provide a basis for determining the potential of the SSM/I high frequency channels for improving sea ice algorithms and for investigating oceanic processes. Improved sea ice algorithms will aid the study of Arctic coastal polynyas which in turn will provide a better understanding of the role of these polynyas in maintaining the Arctic watermass structure. Analysis of satellite and archived meteorological data sets will provide improved estimates of annual, seasonal and shorter-term sea ice variability.

  6. Solidification and convective instability during early sea ice growth

    NASA Astrophysics Data System (ADS)

    Hitchen, Joseph; Wells, Andrew

    2016-04-01

    Growing sea ice rejects large amounts of cold, salty water into the underlying ocean which contributes to the formation of Antarctic Bottom Water, North Atlantic Deep Water, and maintaining the cold halocline in the Arctic ocean. This cold, salty water is formed by the partial solidification of sea water to form porous sea ice, which is an example of a mushy layer. Convection within the porous ice interior drives the drainage of dense brine into the underlying ocean. We consider how realistic surface cooling and variations in physical properties affect the time-dependent development of early sea ice growth, and the impact on solidification and convective instability within the ice. Whilst many previous studies of mushy layers have focussed on growth at a steady rate, we here model geophysically-motivated settings where the growth rate evolves with time. We quantify how the onset of convection in sea ice depends on the initial salinity of the sea water and the rate of heat loss to the overlying atmosphere, and show that slower cooling rates can promote the formation of larger convection cells within the ice.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Arctic sea ice surface ponds due to saltwater impurities

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-03-01

    During the summer melt season the white surface of Arctic sea ice turns to a mixture of grays and blues as meltwater ponds come to dot the landscape. Rising temperatures in late spring melt ice and snow, and the meltwater pools in depressions left by drifting snow. In just a week, these meltwater ponds can come to dominate the ice surface, increasing their areal extent by up to 35% per day. But just as quickly as they appear, the pools can recede, the water flowing into the ocean. Surface ponds drastically reduce the ice's albedo, increasing the amount of light available for Arctic ecosystems and accelerating ice melt.

  14. Dependence of NAO variability on coupling with sea ice

    NASA Astrophysics Data System (ADS)

    Strong, Courtenay; Magnusdottir, Gudrun

    2011-05-01

    The variance of the North Atlantic Oscillation index (denoted N) is shown to depend on its coupling with area-averaged sea ice concentration anomalies in and around the Barents Sea (index denoted B). The observed form of this coupling is a negative feedback whereby positive N tends to produce negative B, which in turn forces negative N. The effects of this feedback in the system are examined by modifying the feedback in two modeling frameworks: a statistical vector autoregressive model ( F VAR) and an atmospheric global climate model ( F CAM) customized so that sea ice anomalies on the lower boundary are stochastic with adjustable sensitivity to the model's evolving N. Experiments show that the variance of N decreases nearly linearly with the sensitivity of B to N, where the sensitivity is a measure of the negative feedback strength. Given that the sea ice concentration field has anomalies, the variance of N goes down as these anomalies become more sensitive to N. If the sea ice concentration anomalies are entirely absent, the variance of N is even smaller than the experiment with the most sensitive anomalies. Quantifying how the variance of N depends on the presence and sensitivity of sea ice anomalies to N has implications for the simulation of N in global climate models. In the physical system, projected changes in sea ice thickness or extent could alter the sensitivity of B to N, impacting the within-season variability and hence predictability of N.

  15. Applicability of highly branched isoprenoids as a sea ice proxy in the Ross Sea

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hyun; Lee, Jae Il; Belt, Simon T.; Gal, Jong-Ku; Smik, Lukas; Shin, Kyung-Hoon

    2016-04-01

    Sea ice is an integral component of the polar climate system, constraining the effect of changing surface albedo, ocean-atmosphere heat exchanges, the formation of deep and intermediate waters that participate in driving the meridional overturning circulation and thus global climate. In recent years, a mono-unsaturated highly branched isoprenoid (HBI) alkene which is biosynthesised by certain sea ice diatoms during the spring bloom and, upon ice melt, deposited into underlying sediments, has been uniquely observed in Arctic sea ice and in Arctic sediments. Hence, the term IP25 (ice proxy with 25 carbon atoms) was proposed to distinguish this compound from other HBI isomers and has become an established proxy for the reconstruction of Arctic sea ice. In contrast, a monounsaturated HBI alkene, i.e. IP25, has not been observed in sea ice or sediments from the Antarctic. Hence, the application of diene and triene HBI concentrations and the resulting diene/triene (D/T) ratio was alternatively introduced as sea ice/open water indicators in the Southern Ocean. However, there is still lack of data covering the wide areas around the Antarctic, especially from the Ross Sea. Hence, we investigated surface sediment samples from the Ross Sea (n=14) collected during the R/V ARAON cruise in 2015 as well as from the Antarctic Peninsula (n=17) collected during several R/V ARAON cruises between 2001 and 2013. We will present our preliminary results and will discuss the applicability of the HBI in the Ross Sea.

  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. Ice Thickness Distribution and Bottom Topography in Beaufort Sea in Winter Preceding 2007 Ice Minimum

    NASA Astrophysics Data System (ADS)

    Wadhams, P.; Rodrigues, J.; Toberg, N.

    2008-12-01

    The unprecedented sea ice retreat in the Arctic Ocean (especially Beaufort Sea) during the summer of 2007 was characterised by exceptional bottom melting. We were able to characterise the thickness distribution of the sea ice during the preceding winter in parts of the Beaufort Sea which subsequently became completely ice-free, as well as in regions of heavier multi-year ice, by means of a transect in March 2007 using a submarine equipped with upward-looking and multi-beam sonar. The transect involved extensive survey work under the APLIS 2007 ice camp from which the SEDNA project (led by University of Alaska) subsequently took place. The upward sonar generated statistical properties of the ice thickness distribution which showed that the ice cover was sensitised for subsequent break-up under enhanced bottom melt because of (a) the prevalence of first-year ice which was unusually thin, (b) the relative absence of deep ridges, (c) the relative prevalence of first-year ridges which melt quickly through water percolation around ice blocks. This is in contrast to the structure of the ice thickness distribution in earlier years. The multi-beam sonar (with additional information from high-resolution studies of individual ridges by small AUVs in 2007 and 2008) yields special insight into the role played by ridge melt in the overall break-up process.

  18. Snow distribution on Antarctic sea ice: precipitation, accumulation, and connections to sea ice thickness from in situ and NASA IceBridge observations.

    NASA Astrophysics Data System (ADS)

    Maksym, T. L.; Kunz, C.; Kwok, R.; Leonard, K. C.; Singh, H.; Trujillo, E.; Williams, G. D.; White, S.; Wever, N.

    2014-12-01

    Snow plays a dominant role in Antarctic sea ice mass balance and its seasonal evolution. It is a primary control on sea ice thickness and the structure of sea ice ecosystems, it dominates the uncertainty in satellite estimates of ice thickness, and it may significantly modulate the response of sea ice to climate change and variability. Here, we provide an overview of recent surveys of snow distribution (both small and large scale), its temporal evolution, and its connection with the processes that drive it - precipitation, accumulation, blowing snow events, flooding, and the role of ice deformation. We present recent 3-D in situ floe-scale measurements of snow surface topography, snow depth, and ice thickness distribution that allow relationships between surface roughness features, snow accumulation, and ice thickness to be examined in unprecedented detail. These data are compared with estimates of snow depth from the NASA IceBridge radar from spring surveys in the Weddell and Amundsen/Bellingshausen Seas. Both airborne and in situ measurements suggest a significant extent of thick ice with a deep snow cover that is underrepresented in prior surveys. Finally, the seasonal evolution of precipitation, snow depth, and accumulation is examined with data from drifting buoy platforms deployed in several regions of the Antarctic. These observations show that precipitation is not necessarily a good estimator for snow accumulation and that treatment of blowing snow must be included for sea ice models to accurately simulate Antarctic snow and sea ice mass balance. The implications of these results for modeling and satellite measurement of the sea ice thickness distribution are discussed.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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).

  5. Source identification of the Arctic sea ice proxy IP25.

    PubMed

    Brown, T A; Belt, S T; Tatarek, A; Mundy, C J

    2014-06-18

    Analysis of the organic geochemical biomarker IP25 in marine sediments is an established method for carrying out palaeo sea ice reconstructions for the Arctic. Such reconstructions cover timescales from decades back to the early Pleistocene, and are critical for understanding past climate conditions on Earth and for informing climate prediction models. Key attributes of IP25 include its strict association with Arctic sea ice together with its ubiquity and stability in underlying marine sediments; however, the sources of IP25 have remained undetermined. Here we report the identification of IP25 in three (or four) relatively minor (<5%) sea ice diatoms isolated from mixed assemblages collected from the Canadian Arctic. In contrast, IP25 was absent in the dominant taxa. Chemical and taxonomical investigations suggest that the IP25-containing taxa represent the majority of producers and are distributed pan-Arctic, thus establishing the widespread applicability of the IP25 proxy for palaeo Arctic sea ice reconstruction.

  6. 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. ...

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Landfast sea ice breakouts: Stabilizing ice features, oceanic and atmospheric forcing at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Jones, Joshua; Eicken, Hajo; Mahoney, Andrew; MV, Rohith; Kambhamettu, Chandra; Fukamachi, Yasushi; Ohshima, Kay I.; George, J. Craig

    2016-09-01

    Landfast sea ice is an important seasonal feature along most Arctic coastlines, such as that of the Chukchi Sea near Barrow, Alaska. Its stability throughout the ice season is determined by many factors but grounded pressure ridges are the primary stabilizing component. Landfast ice breakouts occur when these grounded ridges fail or unground, and previously stationary ice detaches from the coast and drifts away. Using ground-based radar imagery from a coastal ice and ocean observatory at Barrow, we have developed a method to estimate the extent of grounded ridges by tracking ice motion and deformation over the course of winter and have derived ice keel depth and potential for grounding from cumulative convergent ice motion. Estimates of landfast ice grounding strength have been compared to the atmospheric and oceanic stresses acting on the landfast ice before and during breakout events to determine prevailing causes for the failure of stabilizing features. Applying this approach to two case studies in 2008 and 2010, we conclude that a combination of atmospheric and oceanic stresses may have caused the breakouts analyzed in this study, with the latter as the dominant force. Preconditioning (as weakening) of grounded ridges by sea level variations may facilitate failure of the ice sheet leading to breakout events.

  12. 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.

  13. Arctic sea ice albedo from AVHRR

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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. The poor calibration of AVHRR channels 1 and 2 is another large impediment to making accurate albedo estimates.

  14. 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

  15. 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.

  16. 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.

  17. Fluid transport processes within sea ice: towards physically derived models

    NASA Astrophysics Data System (ADS)

    Wells, A. J.; Wettlaufer, J. S.; Orszag, S.

    2012-12-01

    Rather than being an impermeable solid barrier, young sea ice forms a porous matrix of ice crystals through which the interstitial brine can flow. Gravity drainage of dense brine is of particular importance in young sea ice, with the resulting fluid flow redistributing heat, salt, and passive tracers through the ice and controlling exchanges with the ocean. Hence, an understanding of this buoyancy-driven flow is critical for quantifying ice-ocean tracer fluxes, biogeochemical cycles, and evolution of the salinity-dependent material properties of ice that influence growth and decay. We use mushy layer theory, which describes the thermodynamics of the relevant multiphase flow, simulations and analogue experiments to provide insight into these processes. The approach provides a structure to evaluate ad-hoc parameterizations of brine drainage for consistency with the underlying physics. The resulting theoretical framework points towards a bottom-up approach to deriving models via a homogenization of the underlying physical processes.

  18. 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.

  19. 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.

  20. Bacterial communities from Arctic seasonal sea ice are more compositionally variable than those from multi-year sea ice.

    PubMed

    Hatam, Ido; Lange, Benjamin; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2016-10-01

    Arctic sea ice can be classified into two types: seasonal ice (first-year ice, FYI) and multi-year ice (MYI). Despite striking differences in the physical and chemical characteristics of FYI and MYI, and the key role sea ice bacteria play in biogeochemical cycles of the Arctic Ocean, there are a limited number of studies comparing the bacterial communities from these two ice types. Here, we compare the membership and composition of bacterial communities from FYI and MYI sampled north of Ellesmere Island, Canada. Our results show that communities from both ice types were dominated by similar class-level phylogenetic groups. However, at the operational taxonomic unit (OTU) level, communities from MYI and FYI differed in both membership and composition. Communities from MYI sites had consistent structure, with similar membership (presence/absence) and composition (OTU abundance) independent of location and year of sample. By contrast, communities from FYI were more variable. Although FYI bacterial communities from different locations and different years shared similar membership, they varied significantly in composition. Should these findings apply to sea ice across the Arctic, we predict increased compositional variability in sea ice bacterial communities resulting from the ongoing transition from predominantly MYI to FYI, which may impact nutrient dynamics in the Arctic Ocean. PMID:26882269

  1. Bacterial communities from Arctic seasonal sea ice are more compositionally variable than those from multi-year sea ice.

    PubMed

    Hatam, Ido; Lange, Benjamin; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2016-10-01

    Arctic sea ice can be classified into two types: seasonal ice (first-year ice, FYI) and multi-year ice (MYI). Despite striking differences in the physical and chemical characteristics of FYI and MYI, and the key role sea ice bacteria play in biogeochemical cycles of the Arctic Ocean, there are a limited number of studies comparing the bacterial communities from these two ice types. Here, we compare the membership and composition of bacterial communities from FYI and MYI sampled north of Ellesmere Island, Canada. Our results show that communities from both ice types were dominated by similar class-level phylogenetic groups. However, at the operational taxonomic unit (OTU) level, communities from MYI and FYI differed in both membership and composition. Communities from MYI sites had consistent structure, with similar membership (presence/absence) and composition (OTU abundance) independent of location and year of sample. By contrast, communities from FYI were more variable. Although FYI bacterial communities from different locations and different years shared similar membership, they varied significantly in composition. Should these findings apply to sea ice across the Arctic, we predict increased compositional variability in sea ice bacterial communities resulting from the ongoing transition from predominantly MYI to FYI, which may impact nutrient dynamics in the Arctic Ocean.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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://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://ntrs.nasa.gov/search.jsp?R=20010023033&hterms=Okhotsk+Sea+of&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528%2528Okhotsk%252C%2BSea%2529%2Bof%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010023033&hterms=Okhotsk+Sea+of&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528%2528Okhotsk%252C%2BSea%2529%2Bof%2529"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">Ice</span> Variability in the <span class="hlt">Sea</span> of Okhotsk from Passive Microwave Satellite Observations</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.; Zukor, Dorothy (Technical Monitor)</p> <p>2000-01-01</p> <p>The <span class="hlt">Sea</span> of Okhotsk, located between 50 and 60 N, is bounded by the Kamchatka Peninsula, Siberia, Sakhalin Island, and the Kuril Island chain and is the largest midlatitude seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> zone in the Northern Hemisphere. The winter <span class="hlt">sea</span> <span class="hlt">ice</span> cover begins to form in November and expands to cover most of the <span class="hlt">sea</span> by March. Over the following three months, the <span class="hlt">ice</span> retreats with only small <span class="hlt">ice</span>-covered areas remaining by the beginning of June. The <span class="hlt">sea</span> is <span class="hlt">ice</span> free or nearly <span class="hlt">ice</span> free on average for six months of the year, from June through November. The recent compilation of a consistent, long-term record of Northern Hemisphere <span class="hlt">sea</span> <span class="hlt">ice</span> extents based on passive microwave satellite observations from the Nimbus 7 Scanning Multichannel Microwave Radiometer and from four Defense Meteorological Satellite Program Special Sensor Microwave Imagers provides the basis for assessing long-term <span class="hlt">sea</span> <span class="hlt">ice</span> extent variability in the <span class="hlt">Sea</span> of Okhotsk. Analysis of this 20-year data record (1979-1998) shows that based on yearly averages the overall extent of the <span class="hlt">Sea</span> of Okhotsk <span class="hlt">ice</span> cover is decreasing at the rate of -8.1+/-2.1x10(exp 3) sq km/yr (-17.2%/decade), in contrast to the rate of decrease of -33.3+/-0.7x10(exp 3) sq km/yr (-2.7%/decade) for the Northern Hemisphere as a whole. There is large regional <span class="hlt">sea</span> <span class="hlt">ice</span> extent variability of the Arctic <span class="hlt">ice</span> cover. Two of the nine Arctic regions analyzed, the Bering <span class="hlt">Sea</span> and the Gulf of St. Lawrence, show increases of 0.8+/-1.4xl0(exp 3) sq km/yr (2.7%/decade) and 1.2+/-0.5xl0(exp 3) sq km/yr (17.1%/decade), respectively. Interestingly, the <span class="hlt">Sea</span> of Okhotsk and the Gulf of St. Lawrence show about equal percentage changes, but of opposite sign. The <span class="hlt">Sea</span> of Okhotsk exhibits its greatest percent decrease (-24.3%/decade) during spring (April-June). The year of maximum winter <span class="hlt">sea</span> <span class="hlt">ice</span> extent for the <span class="hlt">Sea</span> of Okhotsk was 1979, whereas the minimum winter <span class="hlt">sea</span> <span class="hlt">ice</span> extent occurred in 1984.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhyA..375..288C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhyA..375..288C"><span id="translatedtitle">The Artic-<span class="hlt">sea-ice</span> cover: Problem of forecasting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chmel, A.; Smirnov, V.</p> <p>2007-02-01</p> <p>The <span class="hlt">ice</span>-research station “North Pole 32” (NP 32) was established on the <span class="hlt">ice</span> pack in the Arctic Ocean in 2003 and drifted up to February 2004, when a “global” perturbation in the <span class="hlt">sea-ice</span>-cover caused the intensive <span class="hlt">ice</span> fragmentation around the actual position of the NP 32. As a result, the station ceased its activity and was abandoned in March 2004. The statistical characterization of the <span class="hlt">sea-ice</span> cover fragmentation and the drift dynamics during the final weeks of the work of the NP 32 are under consideration in this communication. The work is an attempt to reveal some features in the prehistory of this large-scale event which could serve for forecasting the substantial perturbations in the <span class="hlt">sea-ice</span> cover. The most prominent feature that indicated the approach of the <span class="hlt">sea-ice</span> fragmentation over the area of ∼10 5 km 2 was the break of the correlated motion of <span class="hlt">ice</span>-fields observed 2 days before the “catastrophic” event.</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=Impact+CO2&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DImpact%2BCO2','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950045752&hterms=Impact+CO2&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DImpact%2BCO2"><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('https://www.ncbi.nlm.nih.gov/pubmed/20434194','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20434194"><span id="translatedtitle">Arctic Ocean <span class="hlt">sea</span> <span class="hlt">ice</span> drift origin derived from artificial radionuclides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cámara-Mor, P; Masqué, P; Garcia-Orellana, J; Cochran, J K; Mas, J L; Chamizo, E; Hanfland, C</p> <p>2010-07-15</p> <p>Since the 1950s, nuclear weapon testing and releases from the nuclear industry have introduced anthropogenic radionuclides into the <span class="hlt">sea</span>, and in many instances their ultimate fate are the bottom sediments. The Arctic Ocean is one of the most polluted in this respect, because, in addition to global fallout, it is impacted by regional fallout from nuclear weapon testing, and indirectly by releases from nuclear reprocessing facilities and nuclear accidents. <span class="hlt">Sea-ice</span> formed in the shallow continental shelves incorporate sediments with variable concentrations of anthropogenic radionuclides that are transported through the Arctic Ocean and are finally released in the melting areas. In this work, we present the results of anthropogenic radionuclide analyses of <span class="hlt">sea-ice</span> sediments (SIS) collected on five cruises from different Arctic regions and combine them with a database including prior measurements of these radionuclides in SIS. The distribution of (137)Cs and (239,240)Pu activities and the (240)Pu/(239)Pu atom ratio in SIS showed geographical differences, in agreement with the two main <span class="hlt">sea</span> <span class="hlt">ice</span> drift patterns derived from the mean field of <span class="hlt">sea-ice</span> motion, the Transpolar Drift and Beaufort Gyre, with the Fram Strait as the main ablation area. A direct comparison of data measured in SIS samples against those reported for the potential source regions permits identification of the regions from which <span class="hlt">sea</span> <span class="hlt">ice</span> incorporates sediments. The (240)Pu/(239)Pu atom ratio in SIS may be used to discern the origin of <span class="hlt">sea</span> <span class="hlt">ice</span> from the Kara-Laptev <span class="hlt">Sea</span> and the Alaskan shelf. However, if the (240)Pu/(239)Pu atom ratio is similar to global fallout, it does not provide a unique diagnostic indicator of the source area, and in such cases, the source of SIS can be constrained with a combination of the (137)Cs and (239,240)Pu activities. Therefore, these anthropogenic radionuclides can be used in many instances to determine the geographical source area of <span class="hlt">sea-ice</span>.</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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5016760','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5016760"><span id="translatedtitle">Influence of <span class="hlt">ice</span> thickness and surface properties on light transmission through Arctic <span class="hlt">sea</span> <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>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.</p> <p>2015-01-01</p> <p>Abstract The observed changes in physical properties of <span class="hlt">sea</span> <span class="hlt">ice</span> such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span>. 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‐<span class="hlt">ice</span> primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of <span class="hlt">sea</span> <span class="hlt">ice</span>. We measured spectral under‐<span class="hlt">ice</span> radiance and irradiance using the new Nereid Under‐<span class="hlt">Ice</span> (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 <span class="hlt">sea</span> <span class="hlt">ice</span>. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under‐<span class="hlt">ice</span> optical measurements with three dimensional under‐<span class="hlt">ice</span> 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‐<span class="hlt">ice</span> light field on small scales (<1000 m2), while <span class="hlt">sea</span> 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 <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and surface albedo. PMID:27660738</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5016760','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5016760"><span id="translatedtitle">Influence of <span class="hlt">ice</span> thickness and surface properties on light transmission through Arctic <span class="hlt">sea</span> <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>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.</p> <p>2015-01-01</p> <p>Abstract The observed changes in physical properties of <span class="hlt">sea</span> <span class="hlt">ice</span> such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span>. 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‐<span class="hlt">ice</span> primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of <span class="hlt">sea</span> <span class="hlt">ice</span>. We measured spectral under‐<span class="hlt">ice</span> radiance and irradiance using the new Nereid Under‐<span class="hlt">Ice</span> (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 <span class="hlt">sea</span> <span class="hlt">ice</span>. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under‐<span class="hlt">ice</span> optical measurements with three dimensional under‐<span class="hlt">ice</span> 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‐<span class="hlt">ice</span> light field on small scales (<1000 m2), while <span class="hlt">sea</span> 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 <span class="hlt">sea</span> <span class="hlt">ice</span> thickness and surface albedo.</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://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('https://www.ncbi.nlm.nih.gov/pubmed/17868292','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17868292"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> occurrence predicts genetic isolation in the Arctic fox.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geffen, Eli; Waidyaratne, Sitara; Dalén, Love; Angerbjörn, Anders; Vila, Carles; Hersteinsson, Pall; Fuglei, Eva; White, Paula A; Goltsman, Michael; Kapel, Christian M O; Wayne, Robert K</p> <p>2007-10-01</p> <p>Unlike Oceanic islands, the islands of the Arctic <span class="hlt">Sea</span> are not completely isolated from migration by terrestrial vertebrates. The pack <span class="hlt">ice</span> connects many Arctic <span class="hlt">Sea</span> islands to the mainland during winter months. The Arctic fox (Alopex lagopus), which has a circumpolar distribution, populates numerous islands in the Arctic <span class="hlt">Sea</span>. In this study, we used genetic data from 20 different populations, spanning the entire distribution of the Arctic fox, to identify barriers to dispersal. Specifically, we considered geographical distance, occurrence of <span class="hlt">sea</span> <span class="hlt">ice</span>, winter temperature, ecotype, and the presence of red fox and polar bear as nonexclusive factors that influence the dispersal behaviour of individuals. Using distance-based redundancy analysis and the BIOENV procedure, we showed that occurrence of <span class="hlt">sea</span> <span class="hlt">ice</span> is the key predictor and explained 40-60% of the genetic distance among populations. In addition, our analysis identified the Commander and Pribilof Islands Arctic populations as genetically unique suggesting they deserve special attention from a conservation perspective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17868292','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17868292"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> occurrence predicts genetic isolation in the Arctic fox.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geffen, Eli; Waidyaratne, Sitara; Dalén, Love; Angerbjörn, Anders; Vila, Carles; Hersteinsson, Pall; Fuglei, Eva; White, Paula A; Goltsman, Michael; Kapel, Christian M O; Wayne, Robert K</p> <p>2007-10-01</p> <p>Unlike Oceanic islands, the islands of the Arctic <span class="hlt">Sea</span> are not completely isolated from migration by terrestrial vertebrates. The pack <span class="hlt">ice</span> connects many Arctic <span class="hlt">Sea</span> islands to the mainland during winter months. The Arctic fox (Alopex lagopus), which has a circumpolar distribution, populates numerous islands in the Arctic <span class="hlt">Sea</span>. In this study, we used genetic data from 20 different populations, spanning the entire distribution of the Arctic fox, to identify barriers to dispersal. Specifically, we considered geographical distance, occurrence of <span class="hlt">sea</span> <span class="hlt">ice</span>, winter temperature, ecotype, and the presence of red fox and polar bear as nonexclusive factors that influence the dispersal behaviour of individuals. Using distance-based redundancy analysis and the BIOENV procedure, we showed that occurrence of <span class="hlt">sea</span> <span class="hlt">ice</span> is the key predictor and explained 40-60% of the genetic distance among populations. In addition, our analysis identified the Commander and Pribilof Islands Arctic populations as genetically unique suggesting they deserve special attention from a conservation perspective. PMID:17868292</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.5747D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.5747D"><span 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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815351H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815351H"><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/2014SPIE.9240E..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9240E..03B"><span id="translatedtitle"><span class="hlt">Sea-ice</span> distribution and variability in the East Greenland <span class="hlt">Sea</span>, 2003-13</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boccolari, Mauro; Guerrieri, Lorenzo; Parmiggiani, Fiorigi</p> <p>2014-10-01</p> <p>This study presents an analysis of the <span class="hlt">sea-ice</span> area time series for the East Greenland <span class="hlt">Sea</span> for the period January 2003 - December 2013. The data used are a subset of the Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Concentration data set derived from the observations of the passive microwave sensors AMSR-E and AMSR-2 and produced, on a daily basis, by the Inst. of Environ. Physics of the University of Bremen. The area of interest goes, approximately, from 57°N to 84°N and from 53°W to 15°E. On the basis of previous studies, the parameter <span class="hlt">Sea</span> <span class="hlt">Ice</span> Area as the sum of all pixels whose <span class="hlt">sea</span> <span class="hlt">ice</span> concentration is above 70%, was introduced for measuring <span class="hlt">sea-ice</span> extent. A first survey of the Greenland <span class="hlt">Sea</span> data set showed a large anomaly in year 2012; this anomaly, clearly linked with the transition period from AMSR-E to AMSR-2 when re-sampled SSM/I data were used, was partially corrected with a linear regression procedure. The correlation between monthly mean <span class="hlt">Sea</span> <span class="hlt">Ice</span> Area and other geophysical parameters, like air temperature, surface wind and cloud cover, was further investigated. High anti-correlation coefficients between air temperature, at <span class="hlt">sea</span> level and in five different tropospheric layers, and observed <span class="hlt">ice</span> cover is confirmed. Our analysis shows that the strong decline of Arctic <span class="hlt">sea-ice</span> area in the last 10 years is not observed in the East Greenland <span class="hlt">Sea</span>; this implies that large reductions have occurred in the Canadian and Russian Arctic. This result confirms a hypothesis recently postulated to explain the different <span class="hlt">sea-ice</span> decline in the Arctic and Antarctic regions.</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=zones+ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dzones%2Bocean','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000052707&hterms=zones+ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dzones%2Bocean"><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/abs/2014PolSc...8..385Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PolSc...8..385Y"><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://ntrs.nasa.gov/search.jsp?R=20060044030&hterms=motion+estimation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmotion%2Bestimation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060044030&hterms=motion+estimation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmotion%2Bestimation"><span id="translatedtitle">Ross <span class="hlt">sea</span> <span class="hlt">ice</span> motion, area flux, and deformation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>kwok, Ron</p> <p>2005-01-01</p> <p>The <span class="hlt">sea</span> <span class="hlt">ice</span> motion, area export, and deformation of the Ross <span class="hlt">Sea</span> <span class="hlt">ice</span> cover are examined with satellite passive microwave and RADARSAT observations. The record of high-resolution synthetic aperture radar (SAR) data, from 1998 and 2000, allows the estimation of the variability of <span class="hlt">ice</span> deformation at the small scale (10 km) and to assess the quality of the longer record of passive microwave <span class="hlt">ice</span> motion. Daily and subdaily deformation fields and RADARSAT imagery highlight the variability of motion and deformation in the Ross <span class="hlt">Sea</span>. With the passive microwave <span class="hlt">ice</span> motion, the area export at a flux gate positioned between Cape Adare and Land Bay is estimated. Between 1992 and 2003, a positive trend can be seen in the winter (March-November) <span class="hlt">ice</span> area flux that has a mean of 990 x 103 km2 and ranges from a low of 600 x 103 km2 in 1992 to a peak of 1600 x 103 km2 in 2001. In the mean, the southern Ross <span class="hlt">Sea</span> produces almost twice its own area of <span class="hlt">sea</span> <span class="hlt">ice</span> during the winter. Cross-gate <span class="hlt">sea</span> level pressure (SLP) gradients explain 60% of the variance in the <span class="hlt">ice</span> area flux. A positive trend in this gradient, from reanalysis products, suggests a 'spinup' of the Ross <span class="hlt">Sea</span> Gyre over the past 12 yr. In both the NCEP-NCAR and ERA-40 surface pressure fields, longer-term trends in this gradient and mean SLP between 1979 and 2002 are explored along with positive anomalies in the monthly cross-gate SLP gradient associated with the positive phase of the Southern Hemisphere annular mode and the extrapolar Southern Oscillation.</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> <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/2011AGUFM.C41E0459N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C41E0459N"><span id="translatedtitle">Microwave signature of <span class="hlt">sea-ice</span> for GCOM-W1/AMSR2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naoki, K.; Nishio, F.; Yoshikawa, M.</p> <p>2011-12-01</p> <p>The lowest Arctic <span class="hlt">sea-ice</span> cover has been recorded in September 2007. After that, though it has increased in 2008 and 2009, it has decreased again in 2010. The factor of the <span class="hlt">sea-ice</span> change is researched in various fields. Monitoring of a thin <span class="hlt">sea-ice</span> thickness is important as these researches because the <span class="hlt">sea-ice</span> thickness has influences for the heat budget. However the retrieval of thin <span class="hlt">sea-ice</span> thickness is difficult because thin <span class="hlt">sea-ice</span> brightness temperature (TB) depends on the salinity and temperature, and there exist the snow over the thin <span class="hlt">sea-ice</span>. In order to know the relationship between <span class="hlt">sea-ice</span> TB and <span class="hlt">sea-ice</span> parameters, we observed thin <span class="hlt">sea-ice</span> TB using Polarimetric Scanning Radiometer (PSR) and measured <span class="hlt">ice</span> thickness by ship. The effect of <span class="hlt">sea-ice</span> parameters on the TB was examined by model. The brightness temperature of the thin <span class="hlt">sea-ice</span> was observed using PSR on board an aircraft in the Okhotsk on February 7, 2003. The <span class="hlt">sea-ice</span> thickness was measured from the icebreaker synchronizing with the aircraft. The TB calculated the variation at the <span class="hlt">sea-ice</span> with/without of the snow, thickness, and the density of the snow. The calculated result was consistent with the observed one in the 18GHz-Hpol. We show the snow density influenced the increased brightness temperature.</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/abs/2016TCry...10..245S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10..245S"><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('https://www.ncbi.nlm.nih.gov/pubmed/27435531','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27435531"><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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Galgani, Luisa; Piontek, Judith; Engel, Anja</p> <p>2016-07-20</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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...629465G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...629465G"><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://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/2015EGUGA..17.6162C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6162C"><span id="translatedtitle">Uncertainties in the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> cover in ocean reanalyses: are current <span class="hlt">ice</span>-ocean reanalyses suitable for initializing <span class="hlt">sea</span> <span class="hlt">ice</span> forecasts?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chevallier, Matthieu; Smith, Greg; Lemieux, Jean-François; Dupont, Frédéric; Forget, Gael; Fujii, Yosuke; Garric, Gilles; Hernandez, Fabrice; Msadek, Rym; Peterson, Drew; Storto, Andrea; Toyoda, Takahiro; Valdivieso, Maria; Vernieres, Guillaume; Zuo, Hao; Balmaseda, Magdalena</p> <p>2015-04-01</p> <p>The dramatically declining Arctic <span class="hlt">ice</span> cover observed in recent years has prompted a growing interest in resource exploration and marine traffic. This has in turn led to an increasing demand for reliable <span class="hlt">ice</span> prediction capabilities on timescales from hourly to seasonal. The predictability of <span class="hlt">sea</span> <span class="hlt">ice</span> cover on seasonal timescales has been a topic of much interest in recent years with skill being demonstrated by various systems. Of particular note, several studies have found that the predictability of seasonal <span class="hlt">ice</span> extent anomalies is strongly dependent on the initial <span class="hlt">ice</span> thickness distribution. This highlights a weakness in almost all <span class="hlt">ice</span> forecasting systems in that they do not include the explicit assimilation of <span class="hlt">ice</span> thickness observations. Moreover, it remains to be seen how the predictability of the seasonal <span class="hlt">ice</span> cover depends on the representation of various physical processes and model details, such as spatial resolution and the inclusion of an <span class="hlt">ice</span> thickness distribution. Here we present a few results from the Ocean ReAnalyses Intercomparison Project (ORA-IP), with a focus on the Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> fields reconstructed by state-of-the-art global ocean reanalyses. Differences between the various reanalyses are explored in terms of the effects of data assimilation, model physics and atmospheric forcing on properties of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover, including concentration, thickness and velocity. In spite of an expected agreement in the reconstructed concentration fields due to the assimilation of surface data, a large spread in <span class="hlt">sea</span> <span class="hlt">ice</span> thickness is found within the ensemble of reanalyses. Through this intercomparison, we aim to highlight deficiencies and discuss best practises in state-of-the-art systems toward answering the question: Are current <span class="hlt">ice</span>-ocean reanalyses suitable for initializing seasonal forecasts of the <span class="hlt">sea</span> <span class="hlt">ice</span> cover?</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://ntrs.nasa.gov/search.jsp?R=20160004954&hterms=Arctic+Sea&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DArctic%2BSea','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160004954&hterms=Arctic+Sea&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DArctic%2BSea"><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('https://www.ncbi.nlm.nih.gov/pubmed/26032323','PUBMED'); return false;" href="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010403','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010403"><span 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.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('https://www.ncbi.nlm.nih.gov/pubmed/27130467','PUBMED'); return false;" href="https://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.</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://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('https://www.ncbi.nlm.nih.gov/pubmed/26580809','PUBMED'); return false;" href="https://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.</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://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://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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4651550','PMC'); return false;" href="https://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/abs/2016EGUGA..1811757R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811757R"><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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS51C0988P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS51C0988P"><span id="translatedtitle"><span class="hlt">Sea</span> <span class="hlt">ice</span> dynamics and the role of wind forcing over 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>Petty, A.; Hutchings, J. K.; Farrell, S. L.; Richter-Menge, J.; Tschudi, M. A.</p> <p>2014-12-01</p> <p>Both the ocean circulation and overlying <span class="hlt">sea</span> <span class="hlt">ice</span> cover of the Beaufort and Chukchi <span class="hlt">seas</span> have experienced significant change in recent decades. We use <span class="hlt">sea</span> <span class="hlt">ice</span> drift estimates from satellite feature tracking (NSIDC/CERSAT), wind forcing from atmospheric reanalysis products (NCEP-R2/ERA-I/JRA-55), and <span class="hlt">ice</span> type information from satellite and direct ship-based observations (obtained during the Beaufort Gyre Exploration Project), to investigate the role of wind forcing and <span class="hlt">ice</span> mechanics in driving these changes. An assessment of <span class="hlt">ice</span> drift shows reasonable agreement across the different products, revealing interannual variability in the <span class="hlt">ice</span> flux around the Beaufort <span class="hlt">Sea</span>. However, clear uncertainties remain in determining the magnitude of these fluxes, especially in regions of low <span class="hlt">ice</span> concentration. We find an increase in <span class="hlt">ice</span> export out of the southern Beaufort <span class="hlt">Sea</span> (into the Chukchi <span class="hlt">Sea</span>) across all seasons. We find slight differences in the strength of the decadal (1980-2013) trends in the mean seasonal wind curl over the Beaufort <span class="hlt">Sea</span>, although all reanalysis products indicate a strong and significant increase in anti-cyclonic winds in summer. Analysis of <span class="hlt">ice</span> drift curl suggests increasing anti-cyclonic drift across all seasons, despite the wind curl showing a similar trend in summer only. The strongest trend in <span class="hlt">ice</span> drift curl appears to be in autumn, however recent years have seen a strong reduction in this anti-cyclonic drift, likely due to a combination of changes in the wind forcing and <span class="hlt">sea</span> <span class="hlt">ice</span> state. The implication of this finding is an enhanced response of the ocean circulation to shifts in atmospheric circulation compared to that experienced prior to 2000.</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('https://www.ncbi.nlm.nih.gov/pubmed/23413190','PUBMED'); return false;" href="https://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.</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://ntrs.nasa.gov/search.jsp?R=19940007282&hterms=Arctic+Sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DArctic%2BSea','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940007282&hterms=Arctic+Sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DArctic%2BSea"><span id="translatedtitle">Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> microwave signature and geophysical processes study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Onstott, Robert G.; Shuchman, Robert A.</p> <p>1993-01-01</p> <p>Studies on the validation and utilization of ERS-1 SAR (Synthetic Aperture Radar) derived liquid and solid ocean information and the study of the interregional, regional, and temporal variation of the microwave signatures of <span class="hlt">sea</span> <span class="hlt">ice</span> and snow, are reported. Initial interests are focused on the accuracy of the estimates of <span class="hlt">ice</span> type, <span class="hlt">ice</span> form, deformation state, or thickness, and the ability to retrieve <span class="hlt">ice</span> physical property information. Two in situ campaigns were conducted for the purpose of 'truth' ERS-1 SAR products and to gather data in support of the above science studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9702P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9702P"><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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C43A0776P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C43A0776P"><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://adsabs.harvard.edu/abs/2006AGUFM.C41D0352M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.C41D0352M"><span id="translatedtitle">Operational <span class="hlt">sea</span> <span class="hlt">ice</span> charts: An integrated data product suitable for observing long-term changes in 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>Meier, W. N.; Fetterer, F.; Fowler, C.; Clemente-Colon, P.; Street, T.</p> <p>2006-12-01</p> <p>Passive microwave data has been the primary source for observing large-scale trends and variability in Arctic <span class="hlt">sea</span> <span class="hlt">ice</span>. This provides a consistent record of <span class="hlt">ice</span> conditions since 1978. However, there are known deficiencies in the passive microwave data, including low spatial resolution that limits the precision of the <span class="hlt">ice</span> edge location and an underestimation of summer <span class="hlt">ice</span> area due to surface melt water. Operational <span class="hlt">ice</span> analyses aim to provide the most accurate estimate of <span class="hlt">ice</span> conditions using the best available information, including high spatial resolution satellite data. The manual analyses used to produce the charts provide consistent integration of the various sources as well as quality control of the final products. The National Snow and <span class="hlt">Ice</span> Data Center, in collaboration with the U.S. National <span class="hlt">Ice</span> Center (NIC), has updated the NIC <span class="hlt">ice</span> chart climatology through 2004 and released hemispheric field in a format that is easy to access and analyze. This climatology provides a 30-year record of <span class="hlt">ice</span> conditions and also yields information on different <span class="hlt">ice</span> types (e.g., fast <span class="hlt">ice</span>) that cannot be easily obtained from passive microwave data. However, the quality and quantity of data that is used to produce the <span class="hlt">ice</span> charts has varied over time, leading to inconsistencies in the timeseries. For example, since 1995 the NIC charts have relied significantly on high resolution synthetic aperture radar imagery from Radarsat-1. This has resulted in higher area and extent estimates in the <span class="hlt">ice</span> charts compared to earlier years that need to be accounted for if long-term trends are to be estimated from the <span class="hlt">ice</span> chart climatology. On the other hand, <span class="hlt">ice</span> charts from the Radarsat-1 era can provide a useful comparison for possible changes in the passive microwave data due to more extreme melt over the past ten years. Here we examine the new NIC <span class="hlt">ice</span> chart climatology to investigate the consistency of the timeseries through statistical analysis and comparison with the passive microwave record.</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/2005AGUFM.C51B0302B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.C51B0302B"><span id="translatedtitle">Climate Records of Snow, Glaciers and <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>Ballagh, L.; Dye, D.; Howard, A.; Fetterer, F.</p> <p>2005-12-01</p> <p>Cryospheric data can be used to study global climate change. For example, various environmental factors contribute to changes in annual and interannual snow cover, glacier terminus movement and anomalies of <span class="hlt">sea</span> <span class="hlt">ice</span> extent. Archiving and making the data easily accessible is important. At the National Snow and <span class="hlt">Ice</span> Data Center (NSIDC), three data sets in particular exhibit characteristics that allow for understanding global climate change. Users can analyze glacier retreat from historical glacier photographs, study changes in <span class="hlt">sea</span> <span class="hlt">ice</span> by reviewing historical <span class="hlt">ice</span> charts, and review changes in the annual autumn snow cover onset and last day of snow cover in the Northern Hemisphere. By including a temporal component, the Timing and Statistics of Autumn and Spring Annual Snow Cover for the Northern Hemisphere data set is useful for analyzing statistics of snow cover timing and their relation to other environmental phenomena, for example, vegetation growth dynamics. The Online Glacier Photograph Database, which contains approximately 3,000 images, provides online search and order options for photographs that were previously in risk of deterioration. The Arctic <span class="hlt">Sea</span> <span class="hlt">Ice</span> Charts, 1953-1986: W. Dehn Collection data set includes <span class="hlt">ice</span> charts of the Canadian and Alaskan Arctic Ocean that can be browsed by region and date range. Previously, these <span class="hlt">ice</span> charts were archived in analog format and in need of long-term preservation. The NOAA Climate Database Modernization Program (CDMP) supported the digitization of both the historical photographs and the <span class="hlt">sea</span> <span class="hlt">ice</span> charts. By evaluating these data sets, users will have the opportunity to better interpret climatic change related to snow cover, <span class="hlt">sea</span> <span class="hlt">ice</span> and glacier retreat.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A42C..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A42C..05D"><span id="translatedtitle">Arctic spring ozone reduction associated with projected <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>Deser, C.; Sun, L.; Tomas, R. A.; Polvani, L. M.</p> <p>2013-12-01</p> <p>The impact of Arctic <span class="hlt">sea</span> <span class="hlt">ice</span> loss on the stratosphere is investigated using the Whole-Atmosphere Community Climate Model (WACCM), by prescribing the <span class="hlt">sea</span> <span class="hlt">ice</span> in the late 20th century and late 21st century, respectively. The localized <span class="hlt">Sea</span> Surface Temperature (SST) change associated with <span class="hlt">sea</span> <span class="hlt">ice</span> melt is also included in the future run. Overall, the model simulates a negative annular-mode response in the winter and spring. In the stratosphere, polar vortex strengthens from February to April, peaking in March. Consistent with it, there is an anomalous cooling in the high-latitude stratosphere, and polar cap ozone reduction is up to 20 DU. Since the difference between these two runs lies only in the <span class="hlt">sea</span> <span class="hlt">ice</span> and localized SST in the Arctic, the stratospheric circulation and ozone changes can be attributed to the surface forcing. Eliassen-Palm analysis reveals that the upward propagation of planetary waves is suppressed in the spring as a consequence of <span class="hlt">sea</span> <span class="hlt">ice</span> loss. The reduction in propagation causes less wave dissipation and thus less zonal wind deceleration in the extratropical stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015E%26PSL.431..127B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015E%26PSL.431..127B&link_type=ABSTRACT"><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=feedback&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dfeedback','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070016598&hterms=feedback&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dfeedback"><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://ntrs.nasa.gov/search.jsp?R=20070034034&hterms=zones+ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dzones%2Bocean','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070034034&hterms=zones+ocean&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dzones%2Bocean"><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://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://adsabs.harvard.edu/abs/2015AGUFM.C53B0782B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53B0782B"><span id="translatedtitle">Airborne Grid <span class="hlt">Sea-Ice</span> Surveys for Comparison with Cryosat-2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brozena, J. M.; Gardner, J. M.; Liang, R.; Hagen, R. A.; Ball, D.; Newman, T.</p> <p>2015-12-01</p> <p>The Naval Research Laboratory is studying of the changing Arctic with a focus on <span class="hlt">ice</span> thickness and distribution variability. The goal is optimization of computer models used to predict <span class="hlt">sea</span> <span class="hlt">ice</span> changes. An important part of our study is to calibrate/validate Cryosat-2 <span class="hlt">ice</span> thickness data prior to its incorporation into new <span class="hlt">ice</span> forecast models. The footprint of the altimeter over <span class="hlt">sea-ice</span> is a significant issue in any attempt to ground-truth the data. Along-track footprints are reduced to ~ 300 m by SAR processing of the returns. However, the cross-track footprint is determined by the topography of the surface. Further, the actual return is the sum of the returns from individual reflectors within the footprint making it difficult to interpret the return, and optimize the waveform tracker. We therefore collected a series of grids of scanning LiDAR and radar on sub-satellite tracks over <span class="hlt">sea-ice</span> that would extend far enough cross-track to capture the illuminated area. The difficulty in the collection of such grids, which are comprised of <span class="hlt">adjacent</span> overlapping tracks is <span class="hlt">ice</span> motion of as much as 300 m over the duration of a single flight track (~ 20 km) of data collection. With a typical LiDAR swath width of < 500m adjustment of the survey tracks in near real-time for the <span class="hlt">ice</span> motion is necessary for a coherent data set. This was accomplished by a an NRL devised photogrammetric method of <span class="hlt">ice</span> velocity determination. Post-processing refinements resulted in typical track-to-track miss-ties of ~ 1-2 m, much of which could be attributed to <span class="hlt">ice</span> deformation over the period of the survey. This allows us to reconstruct the <span class="hlt">ice</span> configuration to the time of the satellite overflight, resulting in a good picture of the surface actually illuminated by the radar. The detailed 2-d LiDAR image is the snow surface, not the underlying <span class="hlt">ice</span> presumably illuminated by the radar. Our hope is that the 1-D radar profiles collected along the LiDAR swath centerlines will be sufficient to correct the</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://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> </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://adsabs.harvard.edu/abs/2015GeoRL..4210704Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..4210704Y"><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://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://hdl.handle.net/2060/19810011207','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810011207"><span id="translatedtitle">Oceanographic influences on the <span class="hlt">sea</span> <span class="hlt">ice</span> cover in the <span class="hlt">Sea</span> of Okhotsk</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gratz, A. J.; Parkinson, C. L.</p> <p>1981-01-01</p> <p><span class="hlt">Sea</span> <span class="hlt">ice</span> conditions in the <span class="hlt">Sea</span> of Okhotsk, as determined by satellite images from the electrically scanning microwave radiometer on board Nimbus 5, were analyzed in conjunction with the known oceanography. In particular, the <span class="hlt">sea</span> <span class="hlt">ice</span> coverage was compared with the bottom bathymetry and the surface currents, water temperatures, and salinity. It is found that <span class="hlt">ice</span> forms first in cold, shallow, low salinity waters. Once formed, the <span class="hlt">ice</span> seems to drift in a direction approximating the Okhotsk-Kuril current system. Two basic patterns of <span class="hlt">ice</span> edge positioning which persist for significant periods were identified as a rectangular structure and a wedge structure. Each of these is strongly correlated with the bathymetry of the region and with the known current system, suggesting that convective depth and ocean currents play an important role in determining <span class="hlt">ice</span> patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/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://adsabs.harvard.edu/abs/1992JMS.....3..225C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992JMS.....3..225C"><span id="translatedtitle">The <span class="hlt">ice</span> fauna in the shallow southwestern Beaufort <span class="hlt">Sea</span>, Arctic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carey, Andrew G.</p> <p>1992-06-01</p> <p>Sympagic fauna were studied in seasonal fast <span class="hlt">ice</span> <span class="hlt">adjacent</span> to Narwhal Island during the spring of 1979 and 1980, with emphasis on the origin of the fauna and its relationship to contiguous pelagic and benthic communities. The results of five subprojects are reviewed and compared with recent literature. Within Stefansson Sound, inshore of Narwhal Island, total sympagic meiofaunal densities and species diversity were low. In March 1979, the dominant taxa were polychaete larvae and crustacean nauplii, while in May the dominant group was Nematoda. Total numerical densities were low, ranging from 4500 to 8000 per m 2. During the spring of 1980 large numbers of invertebrate fauna concentrated at the undersurface of seasonal <span class="hlt">sea</span> <span class="hlt">ice</span> on the inner western Beaufort <span class="hlt">Sea</span> continental shelf, seaward of Narwhal Island. The sympagic meiofauna were comprised primarily of benthic harpacticoid and cyclopoid copepods, turbellarians, nematode worms, and polychaete worm larvae. Total meiofaunal densities increased from about 6000 per m 2 in April to about 482,000 per m 2 in June. All life stages of Cyclopina gracilis (Copepoda: Cyclopoida) were present in the <span class="hlt">ice</span>. This species appeared to reproduce continuously from early April to early June during the study period. The Harpacticus sp. (Copepoda: Harpaticoida) population consisted of one cohort whose individuals grew in size from April to early June. The sympagic macrofauna consisted entirely of amphipod crustaceans, primarily comprised of benthic species. Population size structure of the amphipod Pseudalibrotus (= Onisimus) litoralis was bimodal and there was a lack of intermediate growth stages. These characteristics indicate that this species has a two-year life cycle in the Beaufort <span class="hlt">Sea</span>. The highest growth rate for P. litoralis coincided with maximal <span class="hlt">ice</span> algal production. P. litoralis fed largely on meiofaunal Crustacea and amphipod fragments in April, but its diet switched to <span class="hlt">ice</span> algae during the height of the bloom in late May</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53D..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53D..08B"><span id="translatedtitle">Simulating Arctic clouds during Arctic Radiation- <span class="hlt">Ice</span>Bridge <span class="hlt">Sea</span> and <span class="hlt">Ice</span> Experiment (ARISE)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bromwich, D. H.; Hines, K. M.; Wang, S. H.</p> <p>2015-12-01</p> <p>The representation within global and regional models of the extensive low-level cloud cover over polar oceans remains a critical challenge for quantitative studies and forecasts of polar climate. In response, the polar-optimized version of the Weather Research and Forecasting model (Polar WRF) is used to simulate the meteorology, boundary layer, and Arctic clouds during the September-October 2014 Arctic Radiation- <span class="hlt">Ice</span>Bridge <span class="hlt">Sea</span> and <span class="hlt">Ice</span> Experiment (ARISE) project. Polar WRF was developed with several adjustments to the <span class="hlt">sea</span> <span class="hlt">ice</span> thermodynamics in WRF. ARISE was based out of Eielson Air Force Base near Fairbanks, Alaska and included multiple instrumented C-130 aircraft flights over open water and <span class="hlt">sea</span> <span class="hlt">ice</span> of the Beaufort <span class="hlt">Sea</span>. Arctic boundary layer clouds were frequently observed within cold northeasterly flow over the open ocean and <span class="hlt">ice</span>. Preliminary results indicate these clouds were primarily liquid water, with characteristics differing between open water and <span class="hlt">sea</span> <span class="hlt">ice</span> surfaces. Simulated clouds are compared to ARISE observations. Furthermore, Polar WRF simulations are run for the August-September 2008 Arctic Summer Cloud Ocean Study (ASCOS) for comparison to the ARISE. Preliminary analysis shows that simulated low-level water clouds over the <span class="hlt">sea</span> <span class="hlt">ice</span> are too extensive during the the second half of the ASCOS field program. Alternatives and improvements to the Polar WRF cloud schemes are considered. The goal is to use the ARISE and ASCOS observations to achieve an improved polar supplement to the WRF code for open water and <span class="hlt">sea</span> <span class="hlt">ice</span> that can be provided to the Polar WRF community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1113752H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1113752H"><span id="translatedtitle">L-band radiometry for <span class="hlt">sea</span> <span class="hlt">ice</span> applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heygster, G.; Hedricks, S.; Mills, P.; Kaleschke, L.; Stammer, D.; Tonboe, R.</p> <p>2009-04-01</p> <p>Although <span class="hlt">sea</span> <span class="hlt">ice</span> remote sensing has reached the level of operational exploitation with well established retrieval methods, several important tasks are still unsolved. In particular during freezing and melting periods with mixed <span class="hlt">ice</span> and water surfaces, estimates of <span class="hlt">ice</span> concentration with passive and active microwave sensors remain challenging. Newly formed thin <span class="hlt">ice</span> is also hard to distinguish from open water with radiometers for frequencies above 8 GHz. The SMOS configuration (planned launch 2009) with a radiometer at 1.4 GHz is a promising technique to complement observations at higher microwave frequencies. ESA has initiated a project to investigate the possibilities for an additional Level-2 <span class="hlt">sea</span> <span class="hlt">ice</span> data product based on SMOS. In detail, the project objectives are (1) to model the L band emission of <span class="hlt">sea</span> <span class="hlt">ice</span>, and to assess the potential (2) to retrieve <span class="hlt">sea</span> <span class="hlt">ice</span> parameters, especially concentration and thickness, and (3) to use cold water regions for an external calibration of SMOS. Modelling of L band emission: Several models have are investigated. All of them work on the same basic principles and have a vertically-layered, plane-parallel geometry. They are comprised of three basic components: (1) effective permittivities are calculated for each layer based on <span class="hlt">ice</span> bulk and micro-structural properties; (2) these are integrated across the total depth to derive emitted brightness temperature; (3) scattering terms can also be added because of the granular structure of <span class="hlt">ice</span> and snow. MEMLS (Microwave Emission Model of Layered Snowpacks (Wiesmann and Matzler 1999)) is one such model that contains all three elements in a single Matlab program. In the absence of knowledge about the internal structure of the <span class="hlt">sea</span> <span class="hlt">ice</span>, three-layer (air, <span class="hlt">ice</span> and water) dielectric slab models which take as input a single effective permittivity for the <span class="hlt">ice</span> layer are appropriate. By ignoring scattering effects one can derive a simple analytic expression for a dielectric slab as shown by Apinis and</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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4653624','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4653624"><span id="translatedtitle">Additional Arctic observations improve weather and <span class="hlt">sea-