Preprints
https://doi.org/10.5194/tc-2022-213
https://doi.org/10.5194/tc-2022-213
 
09 Nov 2022
09 Nov 2022
Status: this preprint is currently under review for the journal TC.

Cosmogenic-nuclide data from Antarctic nunataks can constrain past ice sheet sensitivity to marine ice margin instabilities

Anna Ruth Weston Halberstadt, Greg Balco, Hannah Buchband, and Perry Spector Anna Ruth Weston Halberstadt et al.
  • Berkeley Geochronology Center, Berkeley CA USA

Abstract. 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 modeling. End-member transient models parameterized with strong and weak marine ice sheet instability processes, which predict large and small sea-level impacts during warm periods, also predict contrasting and distinct frequency distributions of ice thickness. We identify regions of Antarctica where predicted frequency distributions are diagnostic of marine ice sheet instability parameterizations. We then show that a single comprehensive data set 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 data sets 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.

Anna Ruth Weston Halberstadt et al.

Status: open (until 04 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Anna Ruth Weston Halberstadt et al.

Data sets

5 million year transient Antarctic ice sheet model run with "sensitized" marine ice margin instabilities Balco, G., Buchband, H., & Halberstadt, A. R. https://doi.org/10.15784/601602

5 million year transient Antarctic ice sheet model run with "desensitized" marine ice margin instabilities Balco, G., Buchband, H., & Halberstadt, A. R. https://doi.org/10.15784/601601

Anna Ruth Weston Halberstadt et al.

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Short summary
This paper explores the use of multi-million-year exposure ages from Antarctic bedrock outcrops to benchmark ice sheet model predictions and thereby infer ice sheet sensitivity to warm climates. We describe a new approach for model/data comparison, highlight an example where observational data are used to distinguish end member models, and provide guidance for targeted sampling around Antarctica that can improve understanding of ice sheet response to climate warming in the past and future.