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CONSTRAINING INTERGLACIAL ICE SHEET ELEVATIONS IN INTERIOR WEST ANTARCTICA – Dr. Robert Ackert
November 9, 2020 @ 12:00 pm
CONSTRAINING INTERGLACIAL ICE SHEET
ELEVATIONS IN INTERIOR WEST ANTARCTICA
Dr. Robert Ackert
Dept. of Earth and Planetary Sciences
Monday, November 9, 2020, 12 PM
Abstract: Determining the Antarctic ice response to global warming has been a focus of Antarctic research for decades due to its potential contribution to global sea level. Constraints on ice sheet geometry during past interglacial periods would provide empirical evidence for smaller ice volumes. However, such evidence is difficult to access because it is covered by the current ice sheet. We are using shallow (<100 m) drilling along the ice sheet margin to obtain cores of the subglacial bedrock in which to measure cosmogenic nuclides. These nuclides are only produced when the surfaces are exposed to cosmic radiation. Thus, their presence indicates the rock surface has been ice-free and the adjacent the ice surface was lower than the site. 10Be and 26Al concentrations in samples up to 28 m below the present ice surface in the Ohio Range
indicate long exposure with intermittent ice cover during the last few hundred thousand years. Drilling at Mt.Waesche, near the dome of the ice sheet in Marie Byrd Land, is scheduled for next year. There we have a unique opportunity to constrain ice elevations during the last interglacial because we have identified target lava flows that were erupted from ~79 ka to ~123 ka. Ice sheet models suggest the ice sheet surface at the Ohio Range and at Mt. Waesche is several hundred meters lower during collapse events. These depths are accessible by the IDO drill rigs and will be the target of future projects.