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Landforms of Marine Plain in the Vestfold Hills contrast with those of most in the Vestfold Hills. They include consistent land surfaces at 40+ m and 25 m, characteristics controlled by orientation of rock features, and imprints of phases of glaciation, deglaciation and marine and freshwater inundation. The 40+ m surface is widespread in the Vestfold Hills and has been noted previously. The 25 m level was an earlier coastline, is more localized and marked by water rounded boulders; it serves to differentiate clearly between two terrains of different relief and erratic distribution. The Pliocene sedimentary rocks below the 25 m level have been dislocated, probably during an interval of glaciotectonism caused by northward movement of sediments under an ice load due to northern extension of the Sørsdal Glacier or expansion of the East Antarctic Ice Sheet some time after the mid-Pliocene. Soil development is active. These features are accompanied by the normal aspects of a glaciated landscape such as glacial striations, sand wedges, erratics, and patterned ground. Wind has been important in transporting sand and developing honeycomb weathering on exposed rock faces. [ABSTRACT FROM AUTHOR]

Lichen and moss colonize the surface of glacial debris left after deglaciation. Transformation of unsorted debris into a sorted circle causes early plant remains to be preserved in the fine-grained centre encircled by a coarse, clastic border. Systematic radiocarbon dating of plant remains from the sorted stone circles on King George Island, South Shetland Islands, West Antarctica, yielded ages between 290-4710 14C yrs BP. The oldest age obtained from a large stone circle approximated the regional deglaciation age recorded in marine and lacustrine sediment cores. Most of the ages, however, underestimate the time of deglaciation due to the continual addition of younger plant remains, changes in soil motion, and the diverse vegetation history. Despite its current limitations as a terrestrial proxy for regional deglaciation, further systematic dating and careful interpretation based on surface processes may improve the usefulness of sorted circles in reconstructing the glacial and periglacial history of polar terrestrial environments. [ABSTRACT FROM AUTHOR]

Allogromiid foraminifera and gromiids constitute an important but poorly known component of the meiobenthos in high-latitude marine settings. Here, we present a first report on the diversity of these protists, together with an account of co-occurring invertebrate taxa, in a sample of sea floor sediment from a water depth of 923 m under the Ross Ice Shelf. Light microscopy of sieved sediment yielded 14 allogromiid foraminifera and three Gromia spp. morphotypes. We also obtained 36 partial small subunit rDNA sequences of allogromiids, including 19 sequences of individual isolates and 17 sequences from environmental DNA samples. Phylogenetic analyses of the obtained sequences identified 18 phylotypes, of which seven were closely related to previously sequenced allogromiids, while 11 represented new lineages. Our results demonstrate that a rich meiofaunal assemblage is present under the Ross Ice Shelf, 12 km from the open ocean. Molecular phylogenetic analyses of these allogromiid foraminifera point to the endemic character of the Ross Ice Shelf assemblage; however, more extensive sampling of the molecular diversity of this group of foraminifera in the Antarctic deep sea is necessary to confirm this conclusion. [ABSTRACT FROM AUTHOR]

Initial cosmogenic 10Be results from a former ice limit in Torres del Paine indicate a shortlived stillstand or readvance of Patagonian ice culminating at 12–15 kyr BP with a mean age of 13.2 ± 0.8 kyr BP. The glacier extended some 40 km beyond the present ice margin and was within 15 km of the presumed Last Glacial Maximum limits. The timing of the glacier stage spans the cooling event recorded in Antarctic ice cores, termed the Antarctic Cold Reversal (14.5–12.9 kyr BP). This result implies that glaciers at these latitudes were out of phase with those in the northern hemisphere; instead they mirrored the climate structure of Antarctica during the last glacial to interglacial transition. [ABSTRACT FROM AUTHOR]

Abstract: Temperature, salinity and chlorofluorocarbons (CFCs) 11, 12 and 113 were measured on a line of stations along the front of the Ross Ice Shelf in the austral summers of 1984, 1994 and 2000. Water mass distributions were similar each year but with high variability in the cross-sectional areas. CFC concentrations increased and salinity decreased with time throughout the water column. CFC saturation levels in the shelf and surface waters also increased with time and ranged from 43% to 90%. The undersaturation was due to inflow of low-CFC modified Circumpolar Deep Water, gas exchange limited by sea ice cover and isolation of water from the atmosphere beneath the ice shelf. The residence time of dense shelf waters resulting from sea ice formation is less well constrained by the chemical data than is the strong flow into the Ross Ice Shelf cavity. Shelf waters are transformed over about 3.5 years, by net basal melting of the ice shelf, into fresher Ice Shelf Water (ISW), which emerges as a large plume near the central ice front at temperatures below the sea surface freezing point. We estimate an average ISW production rate of 0.86Sv and an average net basal melt rate of 60km3/year for the Ross Ice Shelf exceeding a 300m draft (75% of the ice cavity) during recent decades from box and stream tube models fit to all of the CFC and salinity data. Model fits to the individual data sets suggest ISW production and net basal melt rate variability due to interannual changes on a shorter time scale than our observations. ISW production based on the CFC budget is better constrained than net basal melting based on thermohaline data, with a heat budget yielding a rate of only 20km3/yr. Reconciling differences between apparent freshwater and temperature changes under the ice shelf involves considerations of mixing, freezing and the flow of meltwater across the ice shelf grounding line. [Copyright &y& Elsevier]

The continued retreat of ice shelves on the Antarctic Peninsulahas been widely attributed to recent atmospheric warming, but there islittle published work describing changes in glacier margin positions. Wepresent trends in 244 marine glacier fronts on the peninsula andassociated islands over the past 61 years. Of these glaciers, 87% haveretreated and a clear boundary between mean advance and retreat hasmigrated progressively southward. The pattern is broadly compatible withretreat driven by atmospheric warming, but the rapidity of the migrationsuggests that this may not be the sole driver of glacier retreat in thisregion. [ABSTRACT FROM AUTHOR]

Alpine glacier deposits in the McMurdo Dry Valleys of Antarctica have been interpreted to indicate that early Pliocene climate in that region was not warmer than it is today. Correlation of these alpine-glacier till sheets to marine deposits that contain evidence consistent with warmer-than-present climate has been used to constrain the age of both deposits, preclude the warm interpretation of the marine evidence, and constrain mountain uplift as determined from the marine deposit. We tested the interpretation that, in the early Pliocene, the alpine glaciers in Wright Valley terminated in a fjord and, thereby, constrain the age, temperature, and depth of the fjord. We did this by mapping the surficial geology in this region using the newly available microtopography based on the light detection and ranging (LIDAR) technique. Stratigraphic issues like these need to be resolved in order to quantify early Pliocene climate in Antarctica and contribute to understanding warm global-climate dynamics. We found that the Pliocene Alpine-IIIA (A-IIIA), A-IIIB and A-IV drift sheets were more likely deposited from terrestrial alpine-glacier lobes than glaciers terminating either at tidewater or with a floating appendage. The principal evidence is the occurrence of moraine fragments weir below the minimum elevation of the early Pliocene fjord surface, and moraine arrangement in arcs indicative of arcuate glacier fronts without flairing near the proposed shoreline. Our A-IIIA till is more widespread in the proglacial areas of the five alpine glaciers examined than previously proposed. We propose that the existing distribution of A-IIIB till reflects glaciers even less extensive than today rather than truncation at a hypothetical fjord surface. Additionally, the A-IV moraine remnants outline glaciers that were significantly larger than those associated with A-III moraines. If we are correct, the age of the A-III till, 3.4 ± 0.1 Ma at maximum, does not constrain the age of the Prospect fjord episode which can be closer to 5.5 ± 0.4 Ma as previously inferred. Moreover, if the alpine tills are not as old as the Prospect fjord episode, the polar paleoclimatic interpretation from those tills does not preclude the high temperature (0–3°C) and reduced salinity previously inferred for the Prospect fjord. However, if alpine glacier extent was not limited by Prospect fjord surface elevation, then paleoclimate during the A-IIIA, A-IIIB, and A-IV glacial episodes can be quantitatively reconstructed. The Prospect fjord might have been deep, not shallow, and, hence, mountain uplift might be greater than currently thought which would explain minimal alpine-glacier erosion into the valley sides. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an integrated multiproxy approach study (sedimentological, geochemical, preliminary smear-slides diatom assemblages, and 14C ages analyses) performed on a sediment core collected in Cape Hallett Bay (Ross Sea, Antarctica). Sediments record the early Holocene rapid climate changes: buried varved diatomaceous ooze on the base of core (>9.5–9.4 ka BP) are linked to the early Holocene warming and open marine conditions. From 9.4 ka BP, the climate starts to cool (massive mud). From 8.0 to 7.8 ka BP, sandy mud sediment suggests a rapid landward recession of the local/regional glaciers, with relevant underflow inputs, together with the onset of seasonal sea-ice formation. The ages and the characteristics of the youngest sediments are related to the changed oceanographic conditions linked to the retreat of the calving front of the Ross Ice Shelf. [Copyright &y& Elsevier]

Abstract: Ross Island volcanic complex began forming with the emplacement of the basaltic shield volcanoes of Mt. Bird and Mt. Terror between ca. 4.6 and 1.3 Ma, though it has developed most significantly over the last 1 Ma during an eruptive phase resulting in the 3794-m-high composite vent of Mt. Erebus. Throughout this time, loading of the lithosphere at the southern end of the Terror Rift by the Ross Island volcanic pile has progressively depressed the crust, resulting in a subcircular flexural moat around the periphery of the island. Multichannel seismic reflection data collected from the McMurdo-Ross Ice Shelf (MRIS) reveal the stratigraphic architecture of the moat-fill on the southeastern side of Ross Island. The moat region has accommodated a well-stratified, regionally extensive sedimentary succession of at least 1.2 km below the seafloor in the deepest part of the depression. Three seismic stratigraphic units are identified that generally thicken and dip towards Ross Island and are bounded by angular (onlap) unconformities. We infer that the three units were deposited in accommodation space created during discrete phases of volcanic load-induced subsidence: [1.] Unit III. Moderate to low-amplitude discontinuous reflectors are dislocated and tilted by normal faulting and interpreted to represent coarse-grained glacigenic and fine-grained marine sediments with likely intercalated volcanic ash. These strata may have started to accumulate during loading of the crust by Mt. Bird between ca. 4.6 and 3.8 Ma. [2.] Unit II. Moderate to high-amplitude continuous reflectors that onlap Unit III and are interpreted to represent coarse-grained glacigenic and fine-grained marine sediments with likely intercalated volcanic ash. These strata are inferred to have accumulated in the crustal depression resulting from loading by Mt. Terror between ca. 1.8 and 1.3 Ma. [3.] Unit I. Relatively continuous low-amplitude to seismically-opaque reflectors (Unit IB), onlap Unit II and grade upwards into moderate to high amplitude reflectors below the seafloor (Unit IA). Unit IB is interpreted to represent fine-grained pelagic marine sediments and volcanic ashes which may have accumulated during a phase of rapid subsidence at the initiation of Mt. Erebus loading between ca. 1.0 and 0.8 Ma. Unit IA is interpreted to represent progressive infilling of the flexural moat with more coarse-grained, probably glacigenic sediments during continuation of Mt. Erebus loading between ca. 0.8 and 0.2 Ma. These phases of load-induced subsidence may have periodically overdeepened the moat, making it likely that the sedimentary fill is relatively continuous and has largely escaped erosion by ice grounding during past glacial expansions of the West Antarctic Ice Sheet (WAIS) and the MRIS. The age relationships provided by radiometric dating of the various volcanic loads imply that the sediments here have the potential to provide a relatively continuous and high-resolution glacimarine record of the past behavior of the WAIS–MRIS and the climate history of the western Ross Sea region back to ∼5 Ma. This stratigraphic record is scheduled to be drilled by the ANDRILL Program in the austral summer of 2006. From the interpretation of seismic facies, we present a stratigraphic prognosis for the proposed drill site. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

A mass balance calculation was made for the floating part of Byrd Glacier, using 1978-79 ice elevation and velocity data, over the 45 km of Byrd Glacier from its grounding line to where it leaves its fjord and merges with the Ross Ice Shelf. Smoothed basal melting rates were relatively uniform over this distance and averaged 12 ± 2 m yr-1. [ABSTRACT FROM AUTHOR]

East Antarctic ice discharged by Byrd Glacier continues as a flowband to the calving front of the Ross Ice Shelf. Flow across the grounding line changes from compressive to extensive as it leaves the fjord through the Transantarctic Mountains occupied by Byrd Glacier. Magnitudes of the longitudinal compressive stress that suppress opening of transverse tensile cracks are calculated for the flowband. As compressive back stresses diminish, initial depths and subsequent growth of these cracks, and their spacing, are calculated using theories of elastic and ductile fracture mechanics. Cracks are initially about one millimeter wide, with approximately 30 m depths and 20 m spacings for a back stress of 83 kPa at a distance of 50 km beyond the fjord, where floating ice is 600 m thick. When these crevasses penetrate the whole ice thickness, they release tabular icebergs 20 km to 100 km wide, spaced parallel to the calving front of the Ross Ice Shelf. [ABSTRACT FROM AUTHOR]

During a cruise to the Ross Ice Shelf we counted all penguins and marine mammals seen whilst underway. Our objective was to determine the abundance and distribution of these animals along our cruise line. From 14 May until 11 June the sun was below the horizon. Our observations were from the 18 m high bridge. Most watches were in the dark, aided by the bridge spotlights. A total of 79 emperor penguins, 920 Adélie penguins, and 27 marine mammals were counted. We conclude that the Ross Sea, in which wildlife flourishes during the summer, is depauperate in winter. The low numbers of marine mammals may be due partially to their tendency to remain below the surface most of the time. However, Adélie penguins, a visual hunter which rests on sea ice at night, appear to prefer pack ice edges where there is a few hours of daylight and civil twilight for pursuit of prey. Non-breeding emperor penguins also rest on sea ice at night. All but four were observed north of the Ross Sea. Unlike more northerly colonies where females lay their egg and disperse in May female departure in the Ross Sea appears to be later and, we were unable to determine their winter foraging area. [ABSTRACT FROM AUTHOR]

GPS measurements collected between 1999 and 2002 in Marie Byrd Land, West Antarctica indicate no significant present motion between East and West Antarctica greater than 1–2 mm/year. Low strain rates imply that the Ross Sea rift is either inactive or active at a very low rate. This result indicates that the two subcontinents are likely joined as a single coherent lithospheric plate. They could have been joined since the end of Adare Trough spreading in Oligocene time. The volcanic activity in the Ross Sea sector at present such as at Mount Erebus is most likely related to mantle upwelling and not associated with continental rifting. GPS measurements of vertical rates indicate postglacial rebound of up to 12±4 mm/year in western Marie Byrd Land (wMBL). Errors are scaled 1σ. The rock uplift rates are consistent with postglacial rebound models of significant ice thinning in the eastern Ross Ice Shelf in the late Holocene. [Copyright &y& Elsevier]

Despite Antarctica being considered the driest continent on Earth, precipitation plays an important role in modulating activities, where reduced visibility in snow not only adversely affects flying operations but can also hinder ground transportation. Precipitation is also a fundamental component in the calculation of the Antarctic mass budget where the balance between precipitation, evaporation, and the outflow of ice through glacial calving and surface and basal melting defines whether the continental ice sheet is in equilibrium or not. In this paper precipitation data from a high-resolution, limited-area gridpoint model are presented, along with verification results and a discussion of how the model data may be used to assist in weather forecasting and climate analyses. [ABSTRACT FROM AUTHOR]

Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. The landscape of the MCMurdo Dry Valleys (MCM) of Antarctica is dominated by glaciers, and glacier melt is the primary water source for life in soils, streams, and lakes. The glaciers, despite their cold and lifeless appearance, offer functioning habitats for life. The major objective of this study was to examine biogeochemical characteristics of miniecosystems present in cryoconite holes and to determine links to other components (soils, streams, and lakes) of the dry valley landscape. We examined cryoconite holes from 5 glaciers spanning the length of Taylor Valley, one of many valleys in the MCM. Cryoconite biotic communities were composed of the same species observed in streams and lakes, namely, cyanobacteria (Chlorococcus, Chroococcus, Crinalium, Oscillatoria, Nostoc, and Sprirulina), rotifers (Philodina gregaria and Cephalodella catellina), tardigrades (Acutuncus antarcticus and Hypsibius spp.), and ciliates. Biotic communities did not reflect the composition of the immediately surrounding environments, suggesting the effects of eolian mixing and transport of sediments and biota across the valley. Gradients of chemistry and biotic abundance in cryoconite holes reflected the position of each glacier in the valley. Nitrogen and organic carbon concentration patterns across glaciers potentially resulted from biological activities in cryoconite holes. Properties of holes were stable from one to the next sampling season, suggesting that changes of cryoconite hole properties develop on longer than yearly time scales. [ABSTRACT FROM AUTHOR]

The movements of nine breeding adult emperor penguins Aptenodytes forsteri from two colonies, Auster (67° 23′S 64° 04′E) and Taylor Glacier (67° 28′S 60° 54′E), were determined by satellite telemetry on their pre-moult foraging trips. While preparing for their annual moult the penguins travelled for 22–38 days and reached distances of up to 618 km from the colony. Six of the nine tracked penguins were followed to three different moult locations all to the west of their breeding colonies and near other known emperor penguins colonies, such as Kloa Point (66°38′S, 59°23′E) and Fold Island (67°17′S, 59°23′E). Sea-ice conditions changed throughout the tracking period; as the birds travelled north the sea-ice contracted south. [ABSTRACT FROM AUTHOR]

Byrd Glacier has one of the largest ice catchment areas in Antarctica, delivers more ice to the Ross Ice Shelf than any other ice stream, and is the fastest of these ice streams. A force balance, combined with a mass balance, demonstrates that stream flow in Byrd Glacier is transitional from sheet flow in East Antarctica to shelf flow in the Ross Ice Shelf. The longitudinal pulling stress, calculated along an ice flowband from the force balance, is linked to variations of ice thickness, to the ratio of the basal water pressure to the ice overburden pressure where Byrd Glacier is grounded, and is reduced by an ice-shelf buttressing stress where Byrd Glacier is floating. Longitudinal tension peaks at pressure-ratio maxima in grounded ice and close to minima in the ratio of the pulling stress to the buttressing stress in floating ice. The longitudinal spacing of these tension peaks is rather uniform and, for grounded ice, the peaks occur at maxima in surface slope that have no clear relation to the bed slope. This implies that the maxima in surface slope constitute a "wave train" that is related to regular variations in ice-bed coupling, not primarily to bed topography. It is unclear whether these surface "waves" are "standing waves" or are migrating either upslope or downslope, possibly causing the grounding line to either retreat or advance. Deciding which is the case will require obtaining bed topography in the map plane, a new map of surface topography, and more sophisticated modeling that includes ice flow linked to subglacial hydrology in the map plane. [ABSTRACT FROM AUTHOR]

In the McMurdo Dry Valleys of Antarctica, glaciers are the source of meltwater during the austral summer, and the streams and adjacent hyporheic zones constitute the entire physical watershed; there are no hillslope processes in these systems. Hyporheic zones can extend several metres from each side of the stream, and are up to 70 cm deep, corresponding to a lateral cross-section as large as 12 m2, and water resides in the subsurface year around. In this study, we differentiate between the near-stream hyporheic zone, which can be characterized with stream tracer experiments, and the extended hyporheic zone, which has a longer time-scale of exchange. We sampled stream water from Green Creek and from the adjacent saturated alluvium for stable isotopes of D and 18O to assess the significance and extent of stream-water exchange between the streams and extended hyporheic zones over long time-scales (days to weeks). Our results show that water residing in the extended hyporheic zone is much more isotopically enriched (up to 11‰ D and 2·2‰ 18O) than stream water. This result suggests a long residence time within the extended hyporheic zone, during which fractionation has occurred owing to summer evaporation and winter sublimation of hyporheic water. We found less enriched water in the extended hyporheic zone later in the flow season, suggesting that stream water may be exchanged into and out of this zone, on the time-scale of weeks to months. The transient storage model OTIS was used to characterize the exchange of stream water with the extended hyporheic zone. Model results yield exchange rates (α) generally an order magnitude lower (10−5 s−1) than those determined using stream-tracer techniques on the same stream. In light of previous studies in these streams, these results suggest that the hyporheic zones in Antarctic streams have near-stream zones of rapid stream-water exchange, where ‘fast’ biogeochemical reactions may influence water chemistry, and extended hyporheic zones, in which slower biogeochemical reaction rates may affect stream-water chemistry at longer time-scales. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We have analysed a series of surface samples from the alpine glaciers of Taylor Valley, Southern Victoria Land, Antarctica for their geochemical composition. This was done to better establish the role of glaciochemical variation on the chemical composition of meltwater streams emanating from the glaciers. The chemistry of the snow and ice changes with proximity to the ocean and with elevation of the glacier surface. The aeolian transport of dry valley dust, as indicated by both chemical and particulate matter variations, is a major process affecting the overall glacier chemistry and the chemistry of the meltwaters. Streams originating on the western edges of the glaciers are more impacted by the aeolian input as they are in the direct path of the major regional wind direction. Our data strongly suggest that the variation in stream geochemistry in Taylor Valley is a result in part of the differences in chemical composition of glacier melt.

Geometric and cross-cutting relationships between the Wilson Piedmont Glacier and raised beach ridges indicate that the glacier margin has undergone Holocene fluctuations. During mid-Holocene time, the Wilson Piedmont Glacier retreated to a position less extensive than at present. A subsequent readvance culminated less than 250 years ago. Since AD 1956, the glacier and adjacent large snow ramps have retreated up to 600 m in some locations. Large snowbanks have also disappeared. Although the cross-cutting relationships and chronology indicate a late-Holocene advance at approximately the same time as the 'Little Ice Age' event, the magnitude and style of that advance differ from those of the classic 'Little Ice Age' glacier fluctuations in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Investigates the features of cold glaciers erosion and deposition in Allan Hills, Antarctica. Formation of rock debris by sandstone blocks; Destruction of bedrock platforms by wind erosion; Derivation of sandstone and siltstone breccia following brecciation of bedrock escarpments.

Examines the subglacial sedimentary system of Central Bransfield Basin in Antarctica. Drainage patterns of ice streams; Occurrence of erosion at the ice base-bedrock contact; Location of the tidewater glaciers flowing to the coastline.

The Antarctic Ice Sheet comprises the West Antarctic Ice Sheet and the much larger East Antarctic Ice Sheet. Fast flowing ice streams and outlet glaciers are important dynamic components of the ice sheet system, and a grid resolution of at least 20 km is required to identify many of these areas. Previous fine resolution numerical models have focussed on ice flow in West Antarctica or on fine resolution modelling of subsections of the ice sheet, since the size of East Antarctica has generally precluded studies of the whole ice sheet at a resolution adequate to identify complex flow features.The equations describing ice flow are highly non-linear, making this a computationally intensive problem. We use a staggered grid for calculation of ice diffusivity to overcome numerical instability, and a sparse packing scheme to take account of the irregular boundary of Antarctica. We have developed an efficient parallel temperature-dependent ice flow model of the entire grounded portion of the Antarctic Ice Sheet at a resolution of 20 km. The model was primarily written to run on a commodity cluster of workstations, and performance results for this and other systems are presented. Ice flow patterns at steady state compare well with recently published balance velocity calculations. [Copyright &y& Elsevier]

Preconsolidation stress recorded in subglacial sediments provides important information about subglacial effective stresses. It is commonly used to reconstruct past effective stresses from sediments left after ice retreat. In this article, we use properties of sub-ice-stream till samples to estimate effective stresses beneath a modern West Antarctic ice stream. Two previous estimates of sub-ice-stream effective stress were derived for the Upstream B (UpB) area of Ice Stream B from shear wave velocities (50 ± 40 kPa, Blankenship et al. 1987) and borehole water level measurements (63 ± 24 kPa, Engelhardt & Kamb 1997). However, geotechnical tests performed on samples of the UpB till have shown that if subjected to effective stress of 50-63 kPa this till would have significantly lower porosity (~0.32-0.35) and higher strength (~22-28 kPa) than it apparently has in situ (~0.4 and ~2 kPa). We derive new estimates of sub-ice-stream effective stress using: (1) Casagrande's construction applied to the results of six confined uniaxial tests, and (2) a combination of void-ratio data for 51 till samples and 3 experimentally constrained equations describing compressibility of the UpB till under normal consolidation, overconsolidation and in the critical state. Casagrande's method yields an upper bound on effective stress of 25 kPa for four till samples and values of 13, and 4.4 kPa for two other samples. The voidratio approach gives 11.7 ± 2.6 (normal consolidation), 18.3 ± 4.4 (overconsolidation) and 2.0 ± 0.8 kPa (critical state). These new, lower estimates of effective stress are consistent with the low till strength that has been independently measured and inferred from recent theoretical ice-stream models. Our interpretation of data on till void ratio in terms of sub-ice-stream effective stress means that we can qualitatively evaluate the nature of the vertical distribution of this stress in the UpB till layer. We infer that in the sampled top 3 m of till the effective-stress distribution is non-hydrostatic, probably close to lithostatic. The results may be useful in future modeling of ice-stream behavior and may aid efforts to delineate paleo-ice streams based on their geologic record. [ABSTRACT FROM AUTHOR]

Presents a study on subpolar, tidewater glacier at Anvers Island in the Antarctic Peninsula. Improvement of understanding on the sedimentary processes and associated deposits in glacial marine settings; List of data collected from the ice-proximal environment; Occurrence of halocline through the stratification of the water column.

Presents measurements of the gas content and isotopic composition of debris-rich basal layers of a polar glacier, Meserve Glacier, Antarctica. Indication of debris entrainment occurrence without alteration of the glacial ice; Direct evidence that active entrainment occurs at the beds of cold glaciers, without bulk freezing of water.

The rapid warming of the West Antarctic Peninsula (WAP) is causing an important expansion of marine coastal areas due to glacier retreat. These new ice-free areas offer additional habitats for the colonization of benthic species in areas formerly occupied by ice. The establishment of benthic species can represent important negative feedback to the warming process due to the new carbon fixed and stored. Opportunistic, fast-growing, and high turnover species are expected to colonize these new emerging areas. At Potter Cove, the glacier retreat has opened wide areas of soft bottoms, which provides an excellent study area to assess the colonization process and the success of opportunistic species. Here, we examined the population response of the opportunistic soft coral Malacobelemnon daytoni species in the soft bottom area of Potter Cove with different exposure times due to glacier retreat. Our results show a significant variation of M. daytoni population among the sampled areas in terms of presence, abundances, and distribution. In the long-term ice-free areas, opened for more than 60 years, we observed a ~20-fold increase of M. daytoni densities within just 15 years. However, this extraordinary population outburst was not observed in the newer ice-free areas (≤15 years). We registered very low densities in areas of 15 years and no colonies in areas with 10 years of open sea conditions. These were unexpected results based on colonization capabilities showed by the species and habitat suitability of the new areas. Indeed, using Species Distribution Models (SDMs) we also obtained contrasting outputs. SDMs based on long-term areas presence data predicted high habitat suitability and the potential presence of the species in the newer areas. However, when based on newer and older areas data, SDMs showed low habitat suitability and potential absence of the species in the newer areas. This work suggests that species that can be considered as fast and efficient colonizers, could not perform in that way under certain conditions. This deepens the current knowledge on species natural history and environmental relationships, especially to improve our prediction capabilities under changing environmental conditions. • Climate-driven expansion of ice-free areas is a new challenge for polar researchers. • Species consider efficient pioneers might not colonize these newly available habitats. • Up-to-date field observations are essential to complement the SDMs. • Predicting benthic colonization processes in Antarctica is still a tricky task. [ABSTRACT FROM AUTHOR]

Although the glaciers in the Antarctic periphery currently modestly contribute to sea level rise, their contribution is projected to increase substantially until the end of the 21st century. The South Shetland Islands (SSI), located to the north of the Antarctic Peninsula, are lacking a geodetic mass balance calculation for the entire archipelago. We estimated its geodetic mass balance over a 3–4-year period within 2013–2017. Our estimation is based on remotely sensed multispectral and interferometric SAR data covering 96% of the glacierized areas of the islands considered in our study and 73% of the total glacierized area of the SSI archipelago (Elephant, Clarence, and Smith Islands were excluded due to data limitations). Our results show a close to balance, slightly negative average specific mass balance for the whole area of −0.106 ± 0.007 m w.e. a−1, representing a mass change of −238 ± 12 Mt a−1. These results are consistent with a wider scale geodetic mass balance estimation and with glaciological mass balance measurements at SSI locations for the same study period. They are also consistent with the cooling trend observed in the region between 1998 and the mid-2010s. [ABSTRACT FROM AUTHOR]

The article focuses on research published in "The Cryosphere" which modeled the response and stability of the West Antarctic Ice Sheet to global warming in the next 300 years which identified the Thwaites Glacier as the largest probable source of sea level rise during that time.

Regional changes in the flow velocity of Antarctic glaciers can affect the ice sheet mass balance and formation of surface crevasses. The velocity anomaly of a glacier can be detected using the Double-Differential Interferometric Synthetic Aperture Radar (DDInSAR) technique that removes the constant displacement in two Differential Interferometric SAR (DInSAR) images at different times and shows only the temporally variable displacement. In this study, two circular-shaped ice-velocity anomalies in Campbell Glacier, East Antarctica, were analyzed by using 13 DDInSAR images generated from COSMO-SkyMED one-day tandem DInSAR images in 2010–2011. The topography of the ice surface and ice bed were obtained from the helicopter-borne Ice Penetrating Radar (IPR) surveys in 2016–2017. Denoted as A and B, the velocity anomalies were in circular shapes with radii of ~800 m, located 14.7 km (A) and 11.3 km (B) upstream from the grounding line of the Campbell Glacier. Velocity anomalies were up to ~1 cm/day for A and ~5 cm/day for B. To investigate the cause of the two velocity anomalies, the ice surface and bed profiles derived from the IPR survey crossing the anomalies were analyzed. The two anomalies lay over a bed hill along the glacial valley where stick-slip and pressure melting can occur, resulting in temporal variation of ice velocity. The bright radar reflection and flat hydraulic head at the ice bed of A observed in the IPR-derived radargram strongly suggested the existence of basal water in a form of reservoir or film, which caused smaller friction and the reduced variation of stick-slip motion compared to B. Crevasses began to appear at B due to tensile stress at the top of the hill and the fast flow downstream. The sporadic shift of the location of anomalies suggests complex pressure melting and transportation of the basal water over the bed hill. [ABSTRACT FROM AUTHOR]

The aim of the present project was to find simple satellite-based methods to be used in glaciological-climatological research in Antarctica. A Landsat-TM image from 16 February 1991 was used together with field data to study the spectral charcateristics of different types of snow and ice in the Vestfold Hills, East Antarctica (68degrees35'S, 78degrees10'E). Radiometer measurements were made simultaneously with the satellite passage and at several other occasions using a handheld Photodyne 44XLA. 72 test sites selected in the Landsat-TM image formed the basis for the analysis of the spectral characteristics. Principal component analysis, ratioing, and maximum-likelihood classification were also performed. The analysis revealed a large and interesting information content in the TM image. Blue-ice of different character as well as snow of various degree of metamorphosis were discernible and could also be mapped using maximumlikelihood classification. The TM-3/TM-4-ratio was found to be a simple tool for distinguishing between blue-ice and snow of various character. It also showed to be insensitive to influence from thin clouds and cloud shadows. The TM-3/TM-5-ratio was found to enhance snow grain-size variations. [ABSTRACT FROM AUTHOR]

Analyzes the lithology, stratigraphy and tephra from marine sediment glaciers from the western Ross Sea area in Antarctica. Indications that subglacial till does not extend to the continental shelf edge; Occurrence of the subglacial till as the lowest unit in most cores landward; Distinctions between glacial marine diamictons and subglacial tills.

The most recent volume (27) of Annals of Glaciology, ‘International Symposium on Antarctica and Global Change: Interactions and Impacts’, is a bumper issue comprising 115 articles, providing an immediate impression of the importance now attached to the health of the Antarctic Ice Sheet by the international glacial community. It may be outside the logistical and financial reach of most glacial researchers but the results obtained by those who do have access to this remote and fascinating part of the cryosphere are of importance to much of what we do in the realms of glaciology, glacial geology and geomorphology and glacier?climate relationships. Volume 27 deals with a wide range of topics relating to Holocene and recent changes in all elements of the Antarctic glacial system including the fringing sea ice. Space restricts even a partial review of the contents of this tome here, but if up-to-date information on Antarctic glaciology is required, volume 27 is the place to find it. [ABSTRACT FROM AUTHOR]

This article focuses on a virtual field trip to Antarctica that was designed as a project to help fifth-grade students learn how to use the Internet for educational research. The students visited an interactive web site created by TBT International Inc. They were particularly attracted by the penguins and icebergs. They supplemented their research with inquiry-based experiments. The study consisted of several themes that directly related to Antarctica: weather and climate, glaciers and icebergs, water currents and air currents, and global warming. The students learned that 70 percent of the world's fresh water is found on Antarctica. They were able to explain what they learned using their imagination and creativity. The study was supplemented by various inquiry-based explorations. One activity involved the mimicking of visual deprivation, a temporary blindness that may occur in Antarctica.

Documents submarine giant slide deposits from a well-exposed Mesozoic fore-arc basin in Alexander Island, Antarctica. Geologic setting; Terminology and general characteristics of slide units; Ablation point formation; Himalia Ridge Formation; Spartan Glacier Formation; Pluto Glacier Formation; Fossil bluff group slide deposits; Slide sheet size.

Investigates Neogene glacial history of Antarctica from evidences suggested by the Mount Fleming Upper Valley Drift. Climatic implication of the inference that local alpine glaciation is responsible for the Fleming Upper Valley Drift.