Cosmogenic-nuclide data from Antarctic nunataks can constrain past ice sheet instabilities

We apply geologic evidence from ice-free areas in Antarctica to evaluate model simulations of ice sheet response to warm climates. This is important because such simulations are used to predict ice sheet behaviour in future warm climates, but geologic evidence of smaller-than-present past ice sheets...

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Bibliographic Details
Published in:The Cryosphere
Main Authors: A. R. W. Halberstadt, G. Balco, H. Buchband, P. Spector
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2023
Subjects:
Online Access:https://doi.org/10.5194/tc-17-1623-2023
https://doaj.org/article/49887b460fda4078836a353d30efc5eb
Description
Summary:We apply geologic evidence from ice-free areas in Antarctica to evaluate model simulations of ice sheet response to warm climates. This is important because such simulations are used to predict ice sheet behaviour in future warm climates, but geologic evidence of smaller-than-present past ice sheets is buried under the present ice sheet and therefore generally unavailable for model benchmarking. We leverage an alternative accessible geologic dataset for this purpose: cosmogenic-nuclide concentrations in bedrock surfaces of interior nunataks. These data produce a frequency distribution of ice thickness over multimillion-year periods, which is also simulated by ice sheet modelling. End-member transient models, parameterized with strong and weak marine ice sheet instability processes and ocean temperature forcings, simulate large and small sea-level impacts during warm periods and also predict contrasting and distinct frequency distributions of ice thickness. We identify regions of Antarctica where predicted frequency distributions reveal differences in end-member ice sheet behaviour. We then demonstrate that a single comprehensive dataset from one bedrock site in West Antarctica is sufficiently detailed to show that the data are consistent only with a weak marine ice sheet instability end-member, but other less extensive datasets are insufficient and/or ambiguous. Finally, we highlight locations where collecting additional data could constrain the amplitude of past and therefore future response to warm climates.