Miocene to recent ice elevation variations from the interior of the West Antarctic ice sheet: Constraints from geologic observations, cosmogenic nuclides and ice sheet modeling

S. Mukhopadhyay, R. P. Ackert, A. E. Pope, D. Pollard, and R. M. DeConto

Earth and Planetary Science Letters (1 July 2012)

DOI: 10.1016/j.epsl.2012.05.015

Observations of long-term West Antarctic Ice Sheet (WAIS) behavior can be used to test and constrain dynamic ice sheet models. Long-term observational constraints are however, rare. Here we present the first constraints on long-term (Miocene–Holocene) WAIS elevation from the interior of the ice sheet near the WAIS divide. We use geologic observations and measurements of cosmogenic 21Ne and 10Be in bedrock surfaces to constrain WAIS elevation variations to 65 m above present-day ice levels at the Ohio Range occur only rarely during brief ice sheet highstands, consistent with the observed cosmogenic nuclide data. Furthermore, the model's prediction that highstand elevations have increased on average since the Pliocene is in good agreement with the cosmogenic nuclide data that indicate the highest ice elevation over the past 5 Ma was reached during the highstand at 11 ka. Since the simulated cosmogenic nuclide concentrations derived from the model's ice elevation history are in good agreement with our measurements, we suggest that the model's prediction of more frequent collapsed-WAIS states and smaller WAIS volumes during the Pliocene are also correct.

keywords: WAIS; Pliocene; 21Ne; 10Be; exposure dating; ice sheet model

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