Unglaciated areas in East Antarctica during the Last Glacial (Marine Isotope Stage 3) – New evidence from Rauer Group. (1st December 2016)

• Record Type: Journal Article
• Authors: Berg, Sonja; White, Duanne A.; Bennike, Ole; Fülöp, Réka-H.; Fink, David; Wagner, Bernd; Melles, Martin
• Is Part Of: Quaternary science reviews. Volume 153(2016)
• Page Start: 1
• Page End: 10
• Publication Date: 2016-12-01
• Subjects: Lake sediments -- Exposure dating -- Ice sheet reconstructions -- Antarctica; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2016.08.021
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Limited information on the East Antarctic Ice Sheet (EAIS) geometry during Marine Isotope Stage 3 (MIS 3; 60-25 ka) restricts our understanding of its behaviour during periods of climate and sea level change. Ice sheet models forced by global parameters suggest an expanded EAIS compared to the Holocene during MIS 3, but field evidence from East Antarctic coastal areas contradicts such modelling, and suggests that the ice sheet margins were no more advanced than at present. Here we present a new lake sediment record, and cosmogenic exposure results from bedrock, which confirm that Rauer Group (eastern Prydz Bay) was ice-free for much of MIS 3. We also refine the likely duration of the Last Glacial Maximum (LGM) glaciation in the region. Lacustrine and marine sediments from Rauer Group indicate the penultimate period of ice retreat predates 50 ka. The lacustrine record indicates a change from warmer/wetter conditions to cooler/drier conditions after ca. 35 ka. Substantive ice sheet re-advance, however, may not have occurred until much closer to 20 ka. Contemporary coastal areas were still connected to the sea during MIS 3, restricting the possible extent of grounded ice in Prydz Bay on the continental shelf. In contrast, relative sea levels (RSL) deduced from field evidence indicate an extra ice load averaging several hundred metres thicker ice across the Bay between 45 and 32 ka. Thus, ice must either have been thicker immediately inland (with a steeper ice profile), or there were additional ice domes on the shallow banks of the outer continental shelf. Further work is required to reconcile the differences between empirical evidence of past ice sheet histories, and the history predicted by ice sheet models from far-field temperature and sea level records. Highlights: East Antarctic Ice Sheet margin during MIS 3 was similar to that observed today. New relative sea level constraint provides indication on ice sheet profile during MIS 3. Onset of the penultimate period of ice sheet and glacier retreat predates 50 ka. Short (<10 ka) duration of LGM ice sheet advance in coastal areas.