Elsevier

Quaternary Science Reviews

Volume 100, 15 September 2014, Pages 55-86
Quaternary Science Reviews

Invited review
Reconstruction of changes in the Amundsen Sea and Bellingshausen Sea sector of the West Antarctic Ice Sheet since the Last Glacial Maximum

https://doi.org/10.1016/j.quascirev.2013.10.016Get rights and content
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open access

Highlights

  • We present reconstructions of one Antarctic Ice Sheet sector spanning the past 25 ka.

  • We have collated all published radiocarbon and surface exposure ages from the sector.

  • West Antarctic Ice Sheet interior elevations have changed little during deglaciation.

  • Fastest rates of grounding line retreat occurred across deep, inner shelf basins.

  • Recent changes in this sector are unusual in the context of the past 10,000 years.

Abstract

Marine and terrestrial geological and marine geophysical data that constrain deglaciation since the Last Glacial Maximum (LGM) of the sector of the West Antarctic Ice Sheet (WAIS) draining into the Amundsen Sea and Bellingshausen Sea have been collated and used as the basis for a set of time-slice reconstructions. The drainage basins in these sectors constitute a little more than one-quarter of the area of the WAIS, but account for about one-third of its surface accumulation. Their mass balance is becoming increasingly negative, and therefore they account for an even larger fraction of current WAIS discharge. If all of the ice in these sectors of the WAIS were discharged to the ocean, global sea level would rise by ca 2 m.

There is compelling evidence that grounding lines of palaeo-ice streams were at, or close to, the continental shelf edge along the Amundsen Sea and Bellingshausen Sea margins during the last glacial period. However, the few cosmogenic surface exposure ages and ice core data available from the interior of West Antarctica indicate that ice surface elevations there have changed little since the LGM. In the few areas from which cosmogenic surface exposure ages have been determined near the margin of the ice sheet, they generally suggest that there has been a gradual decrease in ice surface elevation since pre-Holocene times. Radiocarbon dates from glacimarine and the earliest seasonally open marine sediments in continental shelf cores that have been interpreted as providing approximate ages for post-LGM grounding-line retreat indicate different trajectories of palaeo-ice stream recession in the Amundsen Sea and Bellingshausen Sea embayments. The areas were probably subject to similar oceanic, atmospheric and eustatic forcing, in which case the differences are probably largely a consequence of how topographic and geological factors have affected ice flow, and of topographic influences on snow accumulation and warm water inflow across the continental shelf.

Pauses in ice retreat are recorded where there are “bottle necks” in cross-shelf troughs in both embayments. The highest retreat rates presently constrained by radiocarbon dates from sediment cores are found where the grounding line retreated across deep basins on the inner shelf in the Amundsen Sea, which is consistent with the marine ice sheet instability hypothesis. Deglacial ages from the Amundsen Sea Embayment (ASE) and Eltanin Bay (southern Bellingshausen Sea) indicate that the ice sheet had already retreated close to its modern limits by early Holocene time, which suggests that the rapid ice thinning, flow acceleration, and grounding line retreat observed in this sector over recent decades are unusual in the context of the past 10,000 years.

Keywords

Ice sheet
Last Glacial Maximum
Holocene
Ice stream
Grounding line
Radiocarbon
Cosmogenic isotope
Surface exposure age
Multibeam swath bathymetry
Sediment
Glacimarine
Diamicton
Continental shelf
Circumpolar deep water
Subglacial meltwater
Sea level

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This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).