Late Quaternary glacial history, flow dynamics and sedimentation along the eastern margin of the Antarctic Peninsula Ice Sheet

AbstractSediment cores from the continental rise west of the Antarctic Peninsula and the northern Weddell and Scotia Seas were investigated for their ice-rafted debris (IRD) content by lithofacies logging and counting of particles >0.2 cm from core x-radiographs. The objective of the study was to determine if there are iceberg-rafted units similar to the Heinrich layers of the North Atlantic that might record periodic, widespread catastrophic collapse of basins within the Antarctic Ice Sheet during the Quaternary. Cores from the Antarctic Peninsula margin contain prominent IRD-rich units, with maximum IRD concentrations in oxygen isotope stages 1, 5, and 7. However, the greater concentration of IRD in interglacial stages is the result of low sedimentation rates and current winnowing, rather than regional-scale episodes of increased iceberg rafting. This is also supported by markedly lower mass accumulation rates (MAR) during interglacial periods versus glacial periods. Furthermore, thinner IRD layers within isotope stages 2–4 and 6 cannot be correlated between individual cores along the margin. This implies that the ice sheet over the Antarctic Peninsula did not undergo widespread catastrophic collapse along its western margin during the late Quaternary (isotope stages 1–7). Sediment cores from the Weddell and Scotia Seas are characterized by low IRD concentrations throughout, and the IRD signal generally appears to be of limited regional significance with few strong peaks that can be correlated between cores. Tentatively, this argues against pervasive, rapid ice-sheet collapse around the Weddell embayment over the last few glacial cycles.

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Glacial-Marine Sedimentation and Quaternary Glacial History of Marguerite Bay, Antarctic Peninsula

Quaternary Research ◽

10.1016/0033-5894(89)90008-2 ◽

1989 ◽

Vol 31 (2) ◽

pp. 255-276 ◽

Cited By ~ 54

Author(s):

Douglas S. Kennedy ◽

John B. Anderson

Keyword(s):

Antarctic Peninsula ◽

Single Channel ◽

Late Quaternary ◽

Ice Sheet ◽

Glacial History ◽

Ice Shelf ◽

Seismic Reflection Data ◽

Marguerite Bay ◽

Marine Sedimentation ◽

History Of

AbstractMarguerite Bay, situated between the subpolar glacial regime of the northern Antarctic Peninsula and the polar glacial regime of West Antarctica, is ideally located to test various models of glacial and glacial-marine sedimentation and specific scenarios of late Wisconsin ice sheet expansion. Piston cores and single-channel seismic reflection data were collected during the Deep Freeze 85 and 86 expeditions to determine the late Quaternary history of the area. Seismic data in the bay show a rugged seafloor, with numerous deep troughs and a very thin layer of sediment over crystalline basement or older sediments. Glacial erosion is important in modifying existing features, although the ultimate repository of the eroded material is not known; it is not found within the bay. The piston cores are topped by diatomaceous muds, which are underlain by terrigenous muds and muddy gravels that imply deposition beneath an ice shelf. Basal tills were penetrated at three sites, reflecting deposition by a grounded marine ice sheet. A reconstruction of the glacial history of Marguerite Bay since the last glacial maximum shows grounded ice filling the bay in late Wisconsin time. Rising sea level caused an uncoupling of the ice sheet and slow retreat of an ice shelf throughout the Holocene.

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Ice sheet retreat from the Antarctic Peninsula shelf

Continental Shelf Research ◽

10.1016/0278-4343(94)90041-8 ◽

1994 ◽

Vol 14 (15) ◽

pp. 1647-1675 ◽

Cited By ~ 123

Author(s):

C.J. Pudsey ◽

P.F. Barker ◽

R.D. Larter

Keyword(s):

Antarctic Peninsula ◽

Ice Sheet ◽

The Antarctic

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Simultaneous solution for mass trends on the West Antarctic Ice Sheet

The Cryosphere Discussions ◽

10.5194/tcd-8-2995-2014 ◽

2014 ◽

Vol 8 (3) ◽

pp. 2995-3035 ◽

Cited By ~ 1

Author(s):

N. Schön ◽

A. Zammit-Mangion ◽

J. L. Bamber ◽

J. Rougier ◽

T. Flament ◽

...

Keyword(s):

Mass Loss ◽

Antarctic Peninsula ◽

Ice Sheet ◽

The West ◽

Spatial Error ◽

Antarctic Ice Sheet ◽

Forward Models ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

The Antarctic

Abstract. The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76 ± 15 GT yr−1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for.

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Deep and extensive meltwater system beneath the former Eurasian Ice Sheet in the Kara Sea

Geology ◽

10.1130/g46968.1 ◽

2019 ◽

Vol 48 (2) ◽

pp. 179-183 ◽

Cited By ~ 1

Author(s):

Aleksandr Montelli ◽

Julian A. Dowdeswell ◽

Anastasiya Pirogova ◽

Yana Terekhina ◽

Mikhail Tokarev ◽

...

Keyword(s):

Ocean Circulation ◽

Late Quaternary ◽

Thermal Structure ◽

Three Dimensional ◽

Ice Sheet ◽

Kara Sea ◽

Yamal Peninsula ◽

Arctic Seas ◽

Ice Dynamics ◽

Eastern Margin

Abstract The Eurasian ice sheet extended across the Barents and Kara Seas during the late Quaternary, yet evidence on past ice dynamics and thermal structure across its huge eastern periphery remains largely unknown. Here we use three-dimensional seismic data sets covering ∼4500 km2 of the Kara Sea west of Yamal Peninsula, Siberia (71°–73°N), to identify, for the first time in the Russian Arctic seas, several buried generations of vast subglacial tunnel valley networks. Individual valleys are up to 50 km long and are incised as much as 400 m deep; among the largest tunnel valleys ever reported. This discovery represents the first documentation of an extensively warm-based eastern margin of the Eurasian ice sheet during the Quaternary glaciations. The presence of major subglacial channel networks on the shallow shelf, with no evidence of ice streaming, suggests that significant meltwater discharge and subsequent freshwater forcing of ocean circulation may be long-lived rather than catastrophic, occurring during the latest stages of deglaciation in areas where the ice sheet flows slowly and is grounded largely above sea level. Furthermore, the first account of an extensive hydrological network across large areas of the Kara Sea provides important empirical evidence for active subglacial hydrological processes that should be considered in future numerical modeling of the eastern margin of the Quaternary Eurasian ice sheet.

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Nonlinear response of the Antarctic Ice Sheet to late Quaternary sea level and climate forcing

The Cryosphere ◽

10.5194/tc-13-2615-2019 ◽

2019 ◽

Vol 13 (10) ◽

pp. 2615-2631 ◽

Cited By ~ 3

Author(s):

Michelle Tigchelaar ◽

Axel Timmermann ◽

Tobias Friedrich ◽

Malte Heinemann ◽

David Pollard

Keyword(s):

Sea Level ◽

Late Quaternary ◽

Ice Sheet ◽

Volume Changes ◽

Antarctic Ice Sheet ◽

Glacial Ice ◽

Ice Volume ◽

Global Sea Level ◽

The Individual ◽

The Antarctic

Abstract. Antarctic ice volume has varied substantially during the late Quaternary, with reconstructions suggesting a glacial ice sheet extending to the continental shelf break and interglacial sea level highstands of several meters. Throughout this period, changes in the Antarctic Ice Sheet were driven by changes in atmospheric and oceanic conditions and global sea level; yet, so far modeling studies have not addressed which of these environmental forcings dominate and how they interact in the dynamical ice sheet response. Here, we force an Antarctic Ice Sheet model with global sea level reconstructions and transient, spatially explicit boundary conditions from a 408 ka climate model simulation, not only in concert with each other but, for the first time, also separately. We find that together these forcings drive glacial–interglacial ice volume changes of 12–14 ms.l.e., in line with reconstructions and previous modeling studies. None of the individual drivers – atmospheric temperature and precipitation, ocean temperatures, or sea level – single-handedly explains the full ice sheet response. In fact, the sum of the individual ice volume changes amounts to less than half of the full ice volume response, indicating the existence of strong nonlinearities and forcing synergy. Both sea level and atmospheric forcing are necessary to create full glacial ice sheet growth, whereas the contribution of ocean melt changes is found to be more a function of ice sheet geometry than climatic change. Our results highlight the importance of accurately representing the relative timing of forcings of past ice sheet simulations and underscore the need for developing coupled climate–ice sheet modeling frameworks that properly capture key feedbacks.

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Reconstruction of ice-sheet changes in the Antarctic Peninsula since the Last Glacial Maximum

Quaternary Science Reviews ◽

10.1016/j.quascirev.2014.06.023 ◽

2014 ◽

Vol 100 ◽

pp. 87-110 ◽

Cited By ~ 78

Author(s):

Colm Ó Cofaigh ◽

Bethan J. Davies ◽

Stephen J. Livingstone ◽

James A. Smith ◽

Joanne S. Johnson ◽

...

Keyword(s):

Last Glacial Maximum ◽

Antarctic Peninsula ◽

Ice Sheet ◽

Glacial Maximum ◽

Last Glacial ◽

The Antarctic ◽

The Last Glacial Maximum ◽

The Last Glacial

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Late-Pleistocene geomorphological and geochronological history of the former Patagonian Ice Sheet in north-eastern Patagonia (43°S)

10.5194/egusphere-egu2020-2384 ◽

2020 ◽

Author(s):

Tancrede P.M Leger ◽

Andrew S. Hein ◽

Angel Rodes ◽

Robert G. Bingham ◽

Derek Fabel

Keyword(s):

Late Pleistocene ◽

Late Quaternary ◽

Ice Sheet ◽

Glacial History ◽

Climatic Fluctuations ◽

Eastern Sector ◽

North Eastern ◽

Westerly Winds ◽

Proglacial Lake ◽

Exposure Ages

The former Patagonian Ice Sheet was the most extensive Quaternary ice sheet of the southern hemisphere outside of Antarctica. Against a background of Northern Hemisphere-dominated ice volumes, it is essential to document how the Patagonian Ice Sheet and its outlet glaciers &#64258;uctuated throughout the Quaternary. This information can help us investigate the climate forcing mechanisms responsible for ice sheet &#64258;uctuations and provide insight on the causes of Quaternary glacial cycles at the southern mid-latitudes. Moreover, Patagonia is part of the only continental landmass that fully intersects the precipitation-bearing southern westerly winds and is thus uniquely positioned to study past climatic fluctuations in the southern mid-latitudes. While Patagonian palaeoglaciological investigations have increased, there remains few published studies investigating glacial deposits from the north-eastern sector of the former ice sheet, between latitudes 41&#176;S and 46&#176;S. Palaeoglaciological reconstructions from this region are required to understand the timing of late-Pleistocene glacial expansion and retreat, and to understand the causes behind potential latitudinal asynchronies in the glacial records throughout Patagonia. Here, we reconstruct the glacial history and chronology of a previously unstudied region of north-eastern Patagonia that formerly hosted the Rio Huemul and Rio Corcovado (43&#176;S, 71&#176;W) palaeo ice-lobes. We present the first detailed glacial geomorphological map of the valley enabling interpretations of the region&#8217;s late Quaternary glacial history. Moreover, we present new cosmogenic 10Be exposure ages from moraine boulders, palaeolake shoreline surface cobbles and ice-moulded bedrock. This new dataset establishes a high-resolution reconstruction of the local LGM through robust dating of five distinct moraines limits of the Rio Corcovado palaeo-glacier. Our results demonstrate that, in its north-eastern sector, the Patagonian Ice Sheet reached its last maximum extent during MIS 2, thus contrasting with the MIS 3 maxima found for the southern parts of the ice sheet. We also present geomorphological evidence along with chronological data for the formation of two ice-dammed proglacial lake phases in the valley caused by LGM ice-extent fluctuations and final glacial recession. Furthermore, this dataset allows us to determine the timing and onset of glacial termination 1 in the region. Finally, our findings include the reconstruction of a proglacial lake drainage and Atlantic/Pacific drainage reversal event caused by ice sheet break-up in western Patagonia. Such findings have significant implications for climate fluctuations at the southern mid-latitudes, former Southern Westerly Winds behaviour and interhemispheric climate linkages during and following the local LGM. They provide further evidence supporting the proposed latitudinal asynchrony in the timing of expansion of the Patagonian Ice Sheet during the last glacial cycle and enable glacio-geomorphological interpretations for the studied region.

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Automated mapping of Antarctic supraglacial lakes and streams using machine learning

10.5194/egusphere-egu2020-3280 ◽

2020 ◽

Author(s):

Mariel Dirscherl ◽

Andreas Dietz ◽

Celia Baumhoer ◽

Christof Kneisel ◽

Claudia Kuenzer

Keyword(s):

Machine Learning ◽

Mass Balance ◽

Antarctic Peninsula ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Dynamics ◽

Antarctic Ice Sheet ◽

Supraglacial Lakes ◽

The Antarctic ◽

Sentinel 2

Antarctica stores ~91 % of the global ice mass making it the biggest potential contributor to global sea-level-rise. With increased surface air temperatures during austral summer as well as in consequence of global climate change, the ice sheet is subject to surface melting resulting in the formation of supraglacial lakes in local surface depressions. Supraglacial meltwater features may impact Antarctic ice dynamics and mass balance through three main processes. First of all, it may cause enhanced ice thinning thus a potentially negative Antarctic Surface Mass Balance (SMB). Second, the temporary injection of meltwater to the glacier bed may cause transient ice speed accelerations and increased ice discharge. The last mechanism involves a process called hydrofracturing i.e. meltwater-induced ice shelf collapse caused by the downward propagation of surface meltwater into crevasses or fractures, as observed along large coastal sections of the northern Antarctic Peninsula. Despite the known impact of supraglacial meltwater features on ice dynamics and mass balance, the Antarctic surface hydrological network remains largely understudied with an automated method for supraglacial lake and stream detection still missing. Spaceborne remote sensing and data of the Sentinel missions in particular provide an excellent basis for the monitoring of the Antarctic surface hydrological network at unprecedented spatial and temporal coverage.In this study, we employ state-of-the-art machine learning for automated supraglacial lake and stream mapping on basis of optical Sentinel-2 satellite data. With more detail, we use a total of 72 Sentinel-2 acquisitions distributed across the Antarctic Ice Sheet together with topographic information to train and test the selected machine learning algorithm. In general, our machine learning workflow is designed to discriminate between surface water, ice/snow, rock and shadow being further supported by several automated post-processing steps. In order to ensure the algorithm&#8217;s transferability in space and time, the acquisitions used for training the machine learning model are chosen to cover the full circle of the 2019 melt season and the data selected for testing the algorithm span the 2017 and 2018 melt seasons. Supraglacial lake predictions are presented for several regions of interest on the East and West Antarctic Ice Sheet as well as along the Antarctic Peninsula and are validated against randomly sampled points in the underlying Sentinel-2 RGB images. To highlight the performance of our model, we specifically focus on the example of the Amery Ice Shelf in East Antarctica, where we applied our algorithm on Sentinel-2 data in order to present the temporal evolution of maximum lake extent during three consecutive melt seasons (2017, 2018 and 2019).

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Recent glacial advance in the western Weddell Sea Sector driven by anomalous sea ice circulation

10.5194/egusphere-egu2020-7801 ◽

2020 ◽

Author(s):

Frazer Christie ◽

Toby Benham ◽

Julian Dowdeswell

Keyword(s):

Sea Ice ◽

Antarctic Peninsula ◽

Ice Sheet ◽

Weddell Sea ◽

Landsat 8 ◽

Ice Shelf ◽

Total Contribution ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

The Antarctic

The Antarctic Peninsula is one of the most rapidly warming regions on Earth. There, the recent destabilization of the Larsen A and B ice shelves has been directly attributed to this warming, in concert with anomalous changes in ocean circulation. Having rapidly accelerated and retreated following the demise of Larsen A and B, the inland glaciers once feeding these ice shelves now form a significant proportion of Antarctica&#8217;s total contribution to global sea-level rise, and have become an exemplar for the fate of the wider Antarctic Ice Sheet under a changing climate. Together with other indicators of glaciological instability observable from satellites, abrupt pre-collapse changes in ice shelf terminus position are believed to have presaged the imminent disintegration of Larsen A and B, which necessitates the need for routine, close observation of this sector in order to accurately forecast the future stability of the Antarctic Peninsula Ice Sheet. To date, however, detailed records of ice terminus position along this region of Antarctica only span the observational period c.1950 to 2008, despite several significant changes to the coastline over the last decade, including the calving of giant iceberg A-68a from Larsen C Ice Shelf in 2017.Here, we present high-resolution, annual records of ice terminus change along the entire western Weddell Sea Sector, extending southwards from the former Larsen A Ice Shelf on the eastern Antarctic Peninsula to the periphery of Filchner Ice Shelf. Terminus positions were recovered primarily from Sentinel-1a/b, TerraSAR-X and ALOS-PALSAR SAR imagery acquired over the period 2009-2019, and were supplemented with Sentinel-2a/b, Landsat 7 ETM+ and Landsat 8 OLI optical imagery across regions of complex terrain.Confounding Antarctic Ice Sheet-wide trends of increased glacial recession and mass loss over the long-term satellite era, we detect glaciological advance along 83% of the ice shelves fringing the eastern Antarctic Peninsula between 2009 and 2019. With the exception of SCAR Inlet, where the advance of its terminus position is attributable to long-lasting ice dynamical processes following the disintegration of Larsen B, this phenomenon lies in close agreement with recent observations of unchanged or arrested rates of ice flow and thinning along the coastline. Global climate reanalysis and satellite passive-microwave records reveal that this spatially homogenous advance can be attributed to an enhanced buttressing effect imparted on the eastern Antarctic Peninsula&#8217;s ice shelves, governed primarily by regional-scale increases in the delivery and concentration of sea ice proximal to the coastline.

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