Showing papers on "Antarctic sea ice published in 2004"
Bjerknes Centre for Climate Research1, Stockholm University2, Saint Petersburg State University3, Russian Academy of Sciences4, University of Cambridge5, Geological Museum6, Gas Technology Institute7, Lund University8, University of Copenhagen9, Alfred Wegener Institute for Polar and Marine Research10, University of Iceland11, University of New Hampshire12, Geological Survey of Sweden13, University of Oulu14, Aarhus University15, Ohio State University16, Geological Survey of Finland17, University of Bristol18, Leibniz Association19
TL;DR: In this paper, the maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (>140 ka), (2) the Early Weichselian (100-80 ka),(3) the Middle Weichsellian (60-50 ka), and (4) the late Weichselsian (25-15 ka) based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic and sediment core data.
1,426 citations
TL;DR: Rignot et al. as mentioned in this paper attributed the abrupt evolution of the glaciers to the removal of the buttressing ice shelf, and demonstrated the importance of ice shelves on ice sheet mass balance and contribution to sea level change.
Abstract: acceleration exceeds 27 km 3 per year, and ice is thinning at rates of tens of meters per year. We attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf. The magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change. INDEX TERMS: 1827 Hydrology: Glaciology (1863); 1863 Hydrology: Snow and ice (1827); 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 6924 Radio Science: Interferometry; 9310 Information Related to Geographic Region: Antarctica. Citation: Rignot, E., G. Casassa, P. Gogineni, W. Krabill, A. Rivera, and R. Thomas (2004), Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf, Geophys. Res. Lett., 31, L18401, doi:10.1029/ 2004GL020697.
656 citations
TL;DR: In this paper, a simple model that keeps track of the age of ice as it moves about on the Arctic Ocean was proposed to estimate the areal coverage of thick multi-year ice.
Abstract: [1] Three of the past six summers have exhibited record low sea-ice extent on the Arctic Ocean These minima may have been dynamically induced by changes in the surface winds Based on results of a simple model that keeps track of the age of ice as it moves about on the Arctic Ocean, we show that the areal coverage of thick multi-year ice decreased precipitously during 1989–1990 when the Arctic Oscillation was in an extreme “high index” state, and has remained low since that time Under these conditions, younger, thinner ice anomalies recirculate back to the Alaskan coast more quickly, decreasing the time that new ice has to ridge and thicken before returning for another melt season During the 2002 and 2003 summers this anomalously younger, thinner ice was advected into Alaskan coastal waters where extensive melting was observed, even though temperatures were locally colder than normal The age of sea-ice explains more than half of the variance in summer sea-ice extent
448 citations
TL;DR: In this paper, the authors show that the average ice loss from Greenland between 1997 and 2003 was 80 ± 12 km3 yr-1, compared to about 60 km 3 yr -1 for 1993/4-1998/9.
Abstract: Repeated laser-altimeter surveys and modelled snowfall/summer melt show average ice loss from Greenland between 1997 and 2003 was 80 ± 12 km3 yr-1, compared to about 60 km3 yr -1 for 1993/4-1998/9. Half of the increase was from higher summer melting, with the rest caused by velocities of some glaciers exceeding those needed to balance upstream snow accumulation. Velocities of one large glacier almost doubled between 1997 and 2003, resulting in net loss from its drainage basin by about 20 km3 of ice between 2002 and 2003. Copyright 2004 by the American Geophysical Union.
421 citations
TL;DR: In this paper, satellite radar measurements show that ice shelves in Pine Island Bay have thinned by up to 5.5 m yr−1 over the past decade, and the pattern of shelf thinning mirrors that of their grounded tributaries - the Pine Island, Thwaites and Smith glaciers.
Abstract: [1] Satellite radar measurements show that ice shelves in Pine Island Bay have thinned by up to 5.5 m yr−1 over the past decade. The pattern of shelf thinning mirrors that of their grounded tributaries - the Pine Island, Thwaites and Smith glaciers - and ocean currents on average 0.5°C warmer than freezing appear to be the source. The synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini, and the drawdown of grounded ice shows that Antarctica is more sensitive to changing climates than was previously considered.
419 citations
TL;DR: In this paper, the influence of realistic Arctic sea ice anomalies on the atmosphere during winter is investigated with version 3.6 of the Community Climate Model (CCM3.6) for the winters with the most (1982/83) and least (1995/96) Arctic ice coverage during 1979-99, when ice concentration estimates were available from satellites.
Abstract: The influence of realistic Arctic sea ice anomalies on the atmosphere during winter is investigated with version 3.6 of the Community Climate Model (CCM3.6). Model experiments are performed for the winters with the most (1982/83) and least (1995/96) Arctic ice coverage during 1979–99, when ice concentration estimates were available from satellites. The experiments consist of 50-member ensembles: using large ensembles proved critical to distinguish the signal from noise. The local response to ice anomalies over the subpolar seas of both the Atlantic and Pacific is robust and generally shallow with large upward surface heat fluxes (>100 W m−2), near-surface warming, enhanced precipitation, and below-normal sea level pressure where sea ice receded, and the reverse where the ice expanded. The large-scale response to reduced (enhanced) ice extent to the east (west) of Greenland during 1982/83 resembles the negative phase of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) with a ridge over t...
372 citations
TL;DR: In this article, the authors reconstructed large ice-dammed lakes with reversed outlets, e.g. toward the Caspian Sea, based on numerous optically stimulated luminescence (OSL) dates for the periods 90-80 and 60-50 ka.
367 citations
TL;DR: Glacier thinning rates near the coast during 2002–2003 are much larger than those observed during the 1990s, providing exit routes for ice from further inland if ice-sheet collapse is under way.
Abstract: Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 1990s. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.
361 citations
TL;DR: In this article, a robust sea ice-air temperature relationship was demonstrated by a set of four simulations with the atmospheric ECHAM model forced with observed SST and sea ice concentrations.
Abstract: The huge warming of the Arctic that started in the early 1920s and lasted for almost two decades is one of the most spectacular climate events of the twentieth century. During the peak period 1930–40, the annually averaged temperature anomaly for the area 60°–90°N amounted to some 1.7°C. Whether this event is an example of an internal climate mode or is externally forced, such as by enhanced solar effects, is presently under debate. This study suggests that natural variability is a likely cause, with reduced sea ice cover being crucial for the warming. A robust sea ice–air temperature relationship was demonstrated by a set of four simulations with the atmospheric ECHAM model forced with observed SST and sea ice concentrations. An analysis of the spatial characteristics of the observed early twentieth-century surface air temperature anomaly revealed that it was associated with similar sea ice variations. Further investigation of the variability of Arctic surface temperature and sea ice cover was performed by analyzing data from a coupled ocean–atmosphere model. By analyzing climate anomalies in the model that are similar to those that occurred in the early twentieth century, it was found that the simulated temperature increase in the Arctic was related to enhanced wind-driven oceanic inflow into the Barents Sea with an associated sea ice retreat. The magnitude of the inflow is linked to the strength of westerlies into the Barents Sea. This study proposes a mechanism sustaining the enhanced westerly winds by a cyclonic atmospheric circulation in the Barents Sea region created by a strong surface heat flux over the ice-free areas. Observational data suggest a similar series of events during the early twentieth-century Arctic warming, including increasing westerly winds between Spitsbergen and Norway, reduced sea ice, and enhanced cyclonic circulation over the Barents Sea. At the same time, the North Atlantic Oscillation was weakening.
361 citations
TL;DR: The strongest sea ice teleconnection at the interannual time scale was found between El Nino-Southern Oscillation (ENSO) events and a high latitude climate mode named the Antarctic Dipole as mentioned in this paper.
Abstract: Many remote and local climate variabilities influence Antarctic sea ice at different time scales. The strongest sea ice teleconnection at the interannual time scale was found between El Nino-Southern Oscillation (ENSO) events and a high latitude climate mode named the Antarctic Dipole. The Antarctic Dipole is characterized by an out-of-phase relationship between sea ice and surface temperature anomalies in the South Pacific and South Atlantic, manifesting itself and persisting 3-4 seasons after being triggered by the ENSO forcing. This study examines the life cycles of ENSO warm and cold events in the tropics and associated evolution of the ADP in high latitudes of the Southern Hemisphere. In evaluating the mechanisms that form the ADP, the study suggests a synthesized scheme that links these high latitude processes with ENSO teleconnection in both the Pacific and Atlantic basins. The synthesized scheme suggests that the two main mechanisms responsible for the formation/maintenance of the Antarctic Dipole are the heat flux due to the mean meridional circulation of the regional Ferrel Cell and regional anomalous circulation generated by stationary eddies. The changes in the Hadley Cell, the jet stream in the subtropics, and the Rossby Wave train associated with ENSO link the tropical forcing to these high latitude processes. Moreover, these two mechanisms operate in phase and are comparable in magnitude. The positive feedback between the jet stream and stationary eddies in the atmosphere, the positive feedback within the air-sea-ice system, and the seasonality all reinforce the anomalies, resulting in persistent Antarctic Dipole anomalies.
356 citations
TL;DR: In this paper, the authors employ an advanced numerical ice-flow model to simulate the effects of perturbations at the grounding line on PIG's dynamics, and test the hypothesis that these changes are triggered by the adjoining ocean.
Abstract: A growing body of observational data suggests that Pine Island Glacier (PIG) is changing on decadal or shorter timescales. These changes may have far-reaching consequences for the future of the West Antarctic ice sheet (WAIS) and global sea levels because of PIG's role as the ice sheet's primary drainage portal. We test the hypothesis that these changes are triggered by the adjoining ocean. Specifically, we employ an advanced numerical ice-flow model to simulate the effects of perturbations at the grounding line on PIG's dynamics. The speed at which these changes are propagated upstream implies a tight coupling between ice-sheet interior and surrounding ocean.
TL;DR: Marine sediments from the Chilean continental margin are used to infer millennial-scale changes in southeast Pacific surface ocean water properties and Patagonian ice sheet extent since the last glacial period, showing a clear “Antarctic” timing of sea surface temperature changes.
Abstract: Marine sediments from the Chilean continental margin are used to infer millennial-scale changes in southeast Pacific surface ocean water properties and Patagonian ice sheet extent since the last glacial period. Our data show a clear “Antarctic” timing of sea surface temperature changes, which appear systematically linked to meridional displacements in sea ice, westerly winds, and the circumpolar current system. Proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore, but reveal a variable glacier-response time of up to ∼1000 years, which may explain some of the current discrepancies among terrestrial records in southern South America.
TL;DR: In this paper, the authors investigated the mechanisms responsible for the covariability between the ice and the (a) AAO and (b) ENSO and demonstrated that over the last 24 years, a positive AAO trend and a slightly negative e nino-nino-southern Oscillation trend produce a spatial pattern of ice changes similar to the regional ice trends.
Abstract: [1] Trends in the satellite-derived Antarctic sea ice concentrations (1979–2002) show pronounced increase (decrease) in the central Pacific sector (Bellingshausen/western Weddell sector) by ∼4–10% per decade. Confidence levels for these regional trends exceed 95%. Positive polarities of the Antarctic Oscillation (AAO) lead to more (less) ice in the eastern Ross/Amundsen sector (Bellingshausen/northern Weddell sector), which are qualitatively opposite to the impacts of positive polarities of the El Nino-Southern Oscillation (ENSO). The mechanisms responsible for the covariability between the ice and the (a) AAO and (b) ENSO are demonstrated. Over the last 24 years, a positive AAO trend and a slightly negative ENSO trend produce a spatial pattern of ice changes similar to the regional ice trends. However, the magnitude of the ice changes associated with the AAO and ENSO is much smaller than the regional ice trends. More local (or less understood large) scale processes should be investigated for the explanations.
TL;DR: In this article, the authors investigated the impact of the Southern Annular Mode (SAM) on the Antarctic sea ice-ocean system and found that the response of the circumpolar Southern Ocean consists of an annular and a non-annular component.
Abstract: [1] The global sea ice - ocean model ORCA2-LIM, driven by the NCEP/NCAR ( National Centers for Environmental Prediction-National Center for Atmospheric Research) reanalysis daily 2-m air temperatures and 10-m winds and by monthly climatologies for precipitation, cloud cover, and relative humidity, is used to investigate the impact of the Southern Annular Mode (SAM) on the Antarctic sea ice-ocean system. Our results suggest that the response of the circumpolar Southern Ocean consists of an annular and a nonannular component. For the sea ice cover, the non-annular component seems to be the most important. The annular component strongly affects the overall patterns of the upper ocean circulation. When the SAM is in its positive phase, a northward surface Ekman drift, a downwelling at about 45 degreesS, and an upwelling in the vicinity of the Antarctic continent are simulated. The non-annular component has a significant impact at the regional scale, especially in the Weddell, Ross, Amundsen, and Bellingshausen Seas. In those regions, the pressure pattern associated with the SAM induces meridional winds which advect warmer air in the Weddell Sea and around the Antarctic Peninsula and colder air in the Amundsen and Ross Seas. This implies a dipole response of sea ice to the SAM, with on average a decrease in ice area in the Weddell Sea and around the Antarctic Peninsula and an increase in the Ross and Amundsen Seas during years with a high SAM index. The long-term trend in the observed sea ice area does not appear to be related to the trend in the SAM index.
TL;DR: In this paper, the authors present a synthesis of two previously disjoint methodologies based on a large ensemble of glacial cycle simulations using a three-dimensional thermo-mechanically coupled ice-sheet model.
University of Canterbury1, University of Newcastle2, National Institute of Water and Atmospheric Research3, Australian Nuclear Science and Technology Organisation4, Cooperative Research Centre5, Landcare Research6, Lamont–Doherty Earth Observatory7, University of Western Australia8, Macquarie University9, University of Maine10, Australian Antarctic Division11
TL;DR: The Southern Hemisphere westerlies in the southwest Pacific are known to have waxed and waned numerous times during the last two glacial cycles, though even semi-continuous histories of the Westerlies extend back no more than about 20,000 years.
TL;DR: In this article, the authors reconstructed the thickness of the sedimentary bed under a large Antarctic paleo-ice stream for the first time, showing that fast flow is indicated by streamlined seafloor lineations that form the surface of a layer of low shear strength, unsorted sediment, averaging 4.6 m thick.
Abstract: Fast-flowing ice streams and outlet glaciers currently account for as much as 90% of the discharge from the Antarctic and Greenland Ice Sheets. Although the deformation of subglacial material has been proposed as the mechanism for this rapid motion, such sediment is usually hidden under several kilometers of ice. Marine-geophysical records have allowed reconstruction of the three-dimensional thickness of the sedimentary bed beneath a large Antarctic paleo-ice stream for the first time. Fast flow is indicated by streamlined seafloor lineations that form the surface of a layer of low shear strength, unsorted sediment, averaging 4.6 m thick. Rapid motion of the paleo-ice stream was a result of subglacial deformation within this layer.
Alfred Wegener Institute for Polar and Marine Research1, Saint Petersburg State University2, Russian Academy of Sciences3, University of Cambridge4, University of Bergen5, Lund University6, University of Copenhagen7, University of New Hampshire8, University of Oulu9, Geological Survey of Finland10, University of Bristol11
TL;DR: In this paper, the results of studies of the Late Weichselian periglacial environments carried out in key areas of northern Eurasia by several QUEEN teams (European Science Foundation (ESF) programme: “Quaternary Environment of the Eurasian North”).
TL;DR: In this article, the authors show that the depth of the snow cover, by controlling the amount of superimposed ice formation in early summer, critically affects the retention of meltwater at the ice surface and hence affects pond coverage.
Abstract: [1] Linkages between albedo, surface morphology, melt pond distribution, and properties of first-year and multiyear sea ice have been studied at two field sites in the North American Arctic between 1998 and 2001. It is shown that summer sea-ice albedo depends critically on surface melt-pond hydrology, controlled by melt rate, ice permeability, and topography. Remarkable short-term and interannual variability in pond fraction varying by more than a factor of 2 and hence area-averaged albedo (varying between 0.28 and 0.49 over the period of a few days) were observed to be forced by millimeter to centimeter changes in pond water level. Tracer studies show that the depth of the snow cover, by controlling the amount of superimposed ice formation in early summer, critically affects the retention of meltwater at the ice surface and hence affects pond coverage. Ice roughness as determined by deformation and aging processes explains a significant portion of the contrasts in pond coverage and albedo between ice of different ages, suggesting that a reduction in multiyear ice area and sea-ice residence time in the Arctic Ocean is accompanied by large-scale ice albedo decreases. Our work indicates that ice-albedo prediction in large-scale models with conventional methods is inherently difficult, if not impossible. However, a hydrological model, incorporating measured statistics of ice topography, reproduces observed pond features and variability, pointing toward an alternative approach in predicting ice albedo in numerical simulations.
TL;DR: Using the ice accumulation rates estimated from global climate model simulations, it is shown that, over the past ten million years, large variations of Mars' obliquity have allowed the formation of such metres-thick, sedimentary layered deposits in high latitude and polar regions.
Abstract: Observations from the gamma-ray spectrometer instrument suite on the Mars Odyssey spacecraft have been interpreted as indicating the presence of vast reservoirs of near-surface ice in high latitudes of both martian hemispheres1,2,3,4,5. Ice concentrations are estimated to range from 70 per cent at 60° latitude to 100 per cent near the poles, possibly overlain by a few centimetres of ice-free material in most places4. This result is supported by morphological evidence of metres-thick layered deposits that are rich in water-ice6,7,8,9 and periglacial-like features10,11 found only at high latitudes. Diffusive exchange of water between the pore space of the regolith and the atmosphere has been proposed to explain this distribution12, but such a degree of concentration is difficult to accommodate with such processes9,13,14. Alternatively, there are suggestions that ice-rich deposits form by transport of ice from polar reservoirs and direct redeposition in high latitudes during periods of higher obliquity9,13, but these results have been difficult to reproduce with other models. Here we propose instead that, during periods of low obliquity (less than 25°), high-latitude ice deposits form in both hemispheres by direct deposition of ice, as a result of sublimation from an equatorial ice reservoir that formed earlier, during a prolonged high-obliquity excursion. Using the ice accumulation rates estimated from global climate model simulations we show that, over the past ten million years, large variations of Mars' obliquity have allowed the formation of such metres-thick, sedimentary layered deposits in high latitude and polar regions.
TL;DR: In this paper, the results of a numerical model for the Southern Ocean using two contrasting configurations with and without caverns beneath major Antarctic ice shelves are compared, and they show that the freshwater flux due to deep basal melting significantly stabilizes the shelf water column in front of an ice shelf as well as downstream due to advection by the coastal current.
Abstract: [1] An approximation of Antarctica's rocky and icy coastline normally forms the southern boundary in global climate models. Such a configuration neglects extensive ice shelf areas where ocean-ice interaction initiates a net freshwater flux to the circumpolar continental shelf equal to ∼75% of the annual mean net precipitation in coastal seas. The results of a numerical model for the Southern Ocean using two contrasting configurations with and without caverns beneath major Antarctic ice shelves are compared. They show that the freshwater flux due to deep basal melting significantly stabilizes the shelf water column in front of an ice shelf as well as downstream due to advection by the coastal current. If the freshwater from the caverns is absent, sea ice is thinner, shelf waters are warmer and saltier, and the Southern Ocean deep basins are flushed by denser waters.
TL;DR: A Modern Analog Technique (MAT5201/31) has been applied to fossil diatom assemblages to provide down-core estimates of February sea-surface temperatures (SSTs) and of sea ice duration over the past 220,000 years at 56°40′S, 160°14′E as mentioned in this paper.
TL;DR: In this paper, a review unites records of Holocene relative sea level from Svalbard, Franz Josef Land, and Novaya Zemlya to better understand the geometries of past ice sheet loads.
TL;DR: In this paper, the authors combined geomorphological descriptions of changes in the extent of the Greenland Ice Sheet (GIS) with glacial-isostatic-adjustment models to reproduce the sea-level history of Greenland since the Last Glacial Maximum (LGM).
TL;DR: The occurrence and behavior of sympagic amphipods and Arctic cod were studied in the High Arctic Canada Basin by diving under the ice at seven stations in summer 2002 to obtain animal abundances and information on the structure of the ice environment.
Abstract: The occurrence and behavior of sympagic amphipods and Arctic cod (Boreogadus saida) were studied in the High Arctic Canada Basin by diving under the ice at seven stations in summer 2002. Still images of video-transects were used to obtain animal abundances and information on the structure of the ice environment. Mean amphipod abundances for the stations varied between 1 and 23 individuals m−2, with an increase towards the western part of the basin. The standard deviation within the 31–51 images analyzed per station was small (<1 individual m−2). Gammarus wilkitzkii was found in low abundances, often hiding in small ice gaps. Small amphipods (Onisimus spp., Apherusa glacialis, and juveniles of all species) tended to move freely along the bottom of the floes. B. saida occurred in narrow wedges of seawater along the edges of melting ice floes at three stations in water depths of 10–50 cm and was never found under the ice. The fish occurred in schools of 1–28 per wedge. Fish were inactive and did not escape the approaching diver. Resting in the wedges may be a strategy to reduce energetic requirements and avoid predators.
TL;DR: The relationship between the dynamics of sea ice and phytoplankton abundance was investigated for the Cape Bathurst polynya region of the Canadian Arctic using five years (1998-2002) of satellite data from SSM/I and SeaWiFS as mentioned in this paper.
Abstract: [1] The relationship between the dynamics of sea ice and phytoplankton abundance were investigated for the Cape Bathurst polynya region of the Canadian Arctic using five years (1998–2002) of satellite data from SSM/I and SeaWiFS The Cape Bathurst polynya exhibited marked interannual variability in sea ice dynamics, both in the timing of initial polynya formation and in the extent and persistence of open water Related to this, although all years exhibited two distinct phytoplankton blooms, these also varied in their intensity and timing Generally, the late bloom of each year was the most intense, after surface waters had stratified in summer Blooms were most intense in spring 1998, following anomalous warming and early stratification, and late summer 2002, following a summer ice melt event Changes in the timing of phytoplankton bloom development in polar waters can impact food web structure and the relative importance of top-down versus bottom-up control of marine ecosystems
TL;DR: In this article, an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the Antarctic Peninsula: rapid disintegrations of fringing ice shelves induced by climate-controlled meltwater infilling of surface crevasses.
Abstract: [1] Heinrich layers of the glacial North Atlantic record abrupt widespread iceberg rafting of detrital carbonate and other lithic material at the extreme-cold culminations of Bond climate cycles. Both internal (glaciologic) and external (climate) forcings have been proposed. Here we suggest an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the Antarctic Peninsula: rapid disintegrations of fringing ice shelves induced by climate-controlled meltwater infilling of surface crevasses. We postulate that peripheral ice shelves, formed along the eastern Canadian seaboard during extreme cold conditions, would be vulnerable to sudden climate-driven disintegration during any climate amelioration. Ice shelf disintegration then would be the source of Heinrich event icebergs.
TL;DR: In this article, the authors analyzed the Larsen B ice shelf and the collapse of its northern section using satellite images acquired between January 1995 and May 2003, showing significant loss of grounded ice upstream of those ice-shelf sections which disintegrated in 1995 and 2002.
Abstract: The retreat of the Larsen B ice shelf, Antarctic Peninsula, and the collapse of its northern section are analyzed using satellite images acquired between January 1995 and May 2003 Over 1 week during March 2002, after a period of steady retreat since 1995, 2300 km2 of the ice shelf broke up into many small icebergs This rapid collapse occurred at the end of an exceptionally warm summer, and after a multi-year period of decreasing surface net mass balance, ice thinning, flow acceleration and widening of rifts The ice-shelf area decreased from 11 512 km2 in January 1995 to 3463 km2 in March 2002, and 2667 km2 in April 2003 ERS synthetic aperture radar (SAR) images were used to identify ice-shelf zones with different surface morphology, which generated icebergs of different sizes and shapes The pattern of retreat and break-up, similar to that of Larsen A in 1995, suggests that fracturing enhanced by abundant surface melt played a key role In addition, the recent changes of grounded and residual floating ice north of Larsen B are analyzed by means of Envisat advanced synthetic aperture radar (ASAR) images up to summer 2003, showing significant loss of grounded ice upstream of those ice-shelf sections which disintegrated in 1995 and 2002
TL;DR: In this article, the authors review the nature of electromagnetic wave propagation in ice and snow, including the permittivity of ice, signal attenuation and volume scattering, along with reflection from rough and specular surfaces.
Abstract: Radio-echo sounding (RES), utilizing a variety of radio frequencies, was developed to allow glaciologists to measure the thickness of ice sheets and glaciers. We review the nature of electromagnetic wave propagation in ice and snow, including the permittivity of ice, signal attenuation and volume scattering, along with reflection from rough and specular surfaces. The variety of instruments used in RES of polar ice sheets and temperate glaciers is discussed. The applications and insights that a knowledge of ice thickness, and the wider nature of the form and flow of ice sheets, provides are also considered. The thickest ice measured is 4.7 km in East Antarctica. The morphology of the Antarctic and Greenland ice sheets, and many of the smaller ice caps and glaciers of the polar regions, has been investigated using RES. These findings are being used in three-dimensional numerical models of the response of the cryosphere to environmental change. In addition, the distribution and character of internal and basal reflectors within ice sheets contains information on, for example, ice-sheet layering and its chrono-stratigraphic significance, and has enabled the discovery and investigation of large lakes beneath the Antarctic Ice Sheet. Today, RES from ground-based and airborne platforms remains the most effective tool for measuring ice thickness and internal character.
TL;DR: In this paper, an analysis of atmosphere, sea ice, and ocean coupling over the period 1979 to 2000 as a means of setting a physical science context for the Canadian Arctic Shelf Exchange study area (CASES) is presented.
Abstract: [1] Northern Hemisphere sea ice areal extent, and perhaps thickness, have shown a detectable reduction over the past several decades. This situation is particularly apparent in the southern Beaufort Sea. The region encompassing the Mackenzie Shelf, the Cape Bathurst Polynya, and the Canada Basin mobile pack ice all occur in a region referred to here as the Canadian Arctic Shelf Exchange study area (CASES). In this paper we present results from an analysis of atmosphere, sea ice, and ocean coupling over the period 1979 to 2000 as a means of setting a physical science context for the CASES research network (operating over the period 2001-2005). Results show that the Cape Bathurst Polynya complex can be considered as a recurrent polynya; particularly the flaw leads associated with the early opening of the polynya. The Polynya appears to be a consequence of the Beaufort Sea Gyre acting like an ice bridge and a series of flaw leads creating conditions conducive to oceanic upwelling. The sea ice average areal extent has been decreasing in this region over the period 1979 to 2000. Large regional reductions are found (I) north of the Yukon and Alaska Coasts in the region between the Canada Basin pack ice and the landfast sea ice and (2) at the eastern limit of the Cape Bathurst Polynya in Amundsen Gulf. The meteorological forcing of sea ice anomalies occurs through a full range of timescales and space scales. At hemispheric scales a statistical cross-correlation analysis between weekly sea ice concentration anomalies and the Arctic Oscillation accounts for a maximum of about 25 percent of the explained variance and show a surprising spatial coherence in correlation magnitudes both within the study area and northward along the Canadian Archipelago coast. At local scales, positive and negative concentration anomaly periods can be explained through local-scale advective processes associated with regional-scale sea level pressure, 500 hPa geopotential heights, and surface temperature anomalies.