USAP-DC

The Antarctic Ice Sheet (AIS) is sensitive to and an indicator of climate change. While dynamic ice loss is largely driven by ocean forcing, this ice loss might be mitigated by enhanced snowfall on the ice sheet. By developing and understanding of the processes governing snowfall variability and change on the AIS, this project will contribute to the objective of understanding the long-term role of the AIS as a contributor to sea level rise. This project is strongly embedded in the collaborative, open-source framework of the Community Earth System Model version 2 (CESM2) and will deliver new datasets of Antarctic precipitation for the community to use. The project will help to build a diverse geoscience workforce by recruiting and training a SOARs student to be directly involved in the research. A graduate student will also be recruited, and they will play a pivotal role in the proposed work. In this project, we propose to leverage the Climate Model Intercomparison Project 6 (CMIP6) climate model ensemble as a whole, and CESM2 in particular, to disentangle the major sources of uncertainty and to elucidate the underlying mechanisms of Antarctic precipitation change, with a particular focus on the role of atmospheric circulation changes relative to that of atmospheric warming. Using the variable resolution capabilities of CESM2, we will provide the community with precipitation estimates at a very high horizontal resolution. The proposed analyses will also use a forthcoming 100-member large ensemble. The project seeks to answer the following questions: 1) How well does the CESM2 represent the present-day Antarctic surface climate, precipitation, and surface mass balance (SMB), including the mean and its variability? 2) What is the sensitivity of simulated Antarctic precipitation to model resolution in present-day and future climates? 3) What are the roles of thermodynamics (warming atmosphere and ocean) and dynamics (changes in atmospheric circulation) in observed and projected snowfall changes? How do these break down into forced and internal variability? In particular, is there a significant forced precipitation trend due to circulation changes driven by stratospheric ozone depletion and recovery and increases in greenhouse gas concentration? 4) What processes and boundary conditions drive the ensemble spread of AIS precipitation in single-model and multi-model ensembles? How does the spread driven by initial surface conditions (including sea ice cover, surface fluxes, inversion strength) compare with the irreducible uncertainty due to internal climate system variability?

Person	Role
Lenaerts, Jan	Investigator and contact
Schneider, David
Datta, Rajashree Tri	Investigator and contact

Antarctic Glaciology	Award # 1952199
Antarctic Integrated System Science	Award # 1952199
Antarctic Ocean and Atmospheric Sciences	Award # 1952199

USAP-1952199_1

None in the Database

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2. Dunmire, D., Lenaerts, J. T. M., Datta, R. T., & Gorte, T. (2022). Antarctic surface climate and surface mass balance in the Community Earth System Model version 2 (1850–2100). (doi:10.5194/tc-2022-52)
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8. Wille, J. D., Alexander, S. P., Amory, C., Baiman, R., Barthélemy, L., Bergstrom, D. M., Berne, A., Binder, H., Blanchet, J., Bozkurt, D., Bracegirdle, T. J., Casado, M., Choi, T., Clem, K. R., Codron, F., Datta, R., Battista, S. D., Favier, V., Francis, D., … Zou, X. (2024). The Extraordinary March 2022 East Antarctica “Heat” Wave. Part II: Impacts on the Antarctic Ice Sheet. Journal of Climate, 37(3), 779–799. (doi:10.1175/jcli-d-23-0176.1)
9. Holland, P., O’Connor, G., Bracegirdle, T., Dutrieux, P., Naughten, K., Steig, E., Schneider, D., Jenkins, A., & Smith, J. (2022). Anthropogenic and internal drivers of wind changes over the Amundsen Sea, West Antarctica, during the 20th and 21st centuries. (doi:10.5194/tc-2022-121)