USAP-DC

Geologic data provide crucial insights into Antarctic Ice Sheet dynamics; for example, progressive exposure of mountain peaks emerging from the ice sheet reveal ice elevation changes, and the past ‘footprint’ of marine-based ice sheets is imprinted on the seafloor. Numerical ice sheet simulations can link these geologic records in space and time to make larger-scale inferences about continent-wide ice sheet evolution. This work integrates both marine and terrestrial geologic datasets with numerical simulations to investigate Antarctic Ice Sheet behavior (and contribution to global sea level) throughout the last deglaciation, ~20,000 years ago until present. Specifically, this research addresses two issues regarding the relationship between simulations and data and their use in reconstructing past ice-sheet behavior: (1) Geologic records from the modern seafloor suggest significantly earlier retreat of marine-based ice compared to terrestrial records of mountain peak exposure (ice thinning). Computer experiments investigate several hypotheses for this mismatch in timing. (2) Exposure age data (terrestrial measurements recording ice elevation changes) are often interpreted to reflect ice dynamics hundreds of kilometers away from the study site. This work uses simulations to explore the linkage between ice elevation changes ‘upstream’ as glaciers flow through mountainous regions and ice dynamics further ‘downstream’ where ice contacts the ocean. This work will produce a publicly available, customizable, and easily accessible toolkit for comparing simulations and data, including a database of geologic records to use as constraints. The project is interdisciplinary, bridging a communication gap between the ice-sheet simulations and geologic data-collecting communities. This project combines numerical simulations and geologic data to explore fundamental knowledge gaps regarding the interpretation and use of marine and terrestrial datasets. This work will produce an ensemble of continent-wide coupled ice sheet and glacial isostatic adjustment simulations, constrained with comprehensive existing geologic data, to reproduce a history of deglacial Antarctic Ice Sheet evolution that is compatible with the geologic record as well as glaciologically and gravitationally self-consistent. Comparison between simulations and data is improved through high-resolution nested ice sheet modeling techniques, which provide unprecedented context for exposure age data generally located in regions of complex topography. Numerical simulations will be performed with systematically varied parameters and boundary conditions, and can thus support an investigation of (1) chronological mismatches between terrestrial thinning and marine ice sheet retreat during the mid-Holocene, and (2) how marine grounding-line dynamics are propagated upstream to coastal outlet glaciers and further interior under a variety of different scenarios. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Person	Role
Halberstadt, Anna Ruth	Investigator and contact

Post Doc/Travel

Award # 2138556

USAP-2138556_1

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	5 million year transient Antarctic ice sheet model run with "desensitized" marine ice margin instabilities	NetCDF	exists
USAP-DC	5 million year transient Antarctic ice sheet model run with "sensitized" marine ice margin instabilities	NetCDF	exists

1. Halberstadt, A. R. W., Balco, G., Buchband, H., & Spector, P. (2022). Cosmogenic-nuclide data from Antarctic nunataks can constrain past ice sheet sensitivity to marine ice margin instabilities. (doi:10.5194/tc-2022-213)
2. Halberstadt, A. R. W., Balco, G., Buchband, H., & Spector, P. (2023). Cosmogenic-nuclide data from Antarctic nunataks can constrain past ice sheet instabilities. The Cryosphere, 17(4), 1623–1643. (doi:10.5194/tc-17-1623-2023)