Collaborative Research: Climatic Controls of West Antarctic Ice Sheet Surface Mass Balance

University Of Utah, Salt Lake City UT

Investigators

Abstract

Sea level rise remains one of the most pressing and widespread risks of climate change. The West Antarctic Ice Sheet (WAIS), with an ice volume equivalent to 4.3 meters of sea-level rise, provides substantial uncertainty and may dominate sea-level changes in the near future. As climate changes, WAIS surface mass (the balance of snow added and snow lost) changes, which then drives a change in the flow of ice into the ocean. Both the surface mass balance and the shifts in ice flow into the ocean, alter sea level. To determine how climate change will impact WAIS contributions to sea-level changes, it is therefore critical to understand the atmospheric processes driving WAIS surface mass balance and ice flow. In particular, the ice sheet's response to surface mass balance is nonlinear, meaning small changes in weather patterns triggered by variations over the tropics may produce large changes in ice flow. It is therefore critical to assess how changes in climate at both low (e.g., tropics) and high (e.g., polar regions) latitudes combine to impact WAIS surface mass balance and ice flow, and the potential to cross tipping points that would result in rapid changes in sea level. This project will also leverage the existing University of Utah Masters of Science in Secondary School Teaching (MSSST) program, which supports motivated middle and high school teachers to earn an M.S. while still actively engaging in classroom teaching. This project addresses two primary research questions motivated by the need to improve our understanding of atmospheric forcing of WAIS surface mass balance and dynamic response: (1) What climate mechanisms generate interannual-to-multidecadal surface mass balance variability and trends in different sectors of WAIS? (2) How do climate-driven variations at multiple frequencies and spatially divergent trends in surface mass balance project onto ice sheet dynamics? We use a combination of multi-platform, spatially dense surface mass balance records, two century-length climate reanalyses, and climate and glacier numerical modeling to address these two questions. The observational work will use multivariate statistical methods to identify internal versus tropically-forced modes of climate variability relevant to spatiotemporal variations in SMB across WAIS, leveraging spatially dense surface mass balance records from cores and radar in conjunction with multiple century-length climate and sea surface temperature data sets. The resulting hypotheses of climate driver causality will then be tested by conducting boundary-forcing experiments with a global atmospheric model. Finally, the response of ice sheet dynamics to the spectrum of climate forcing from the observational and atmospheric model results will be investigated using a hierarchy of numerical ice sheet models. Ultimately, this work will deconvolve the role of tropical and intrinsic climate variability and trends on the dynamic response of WAIS to SMB variance and trends and how that varies across different regions of WAIS. The results will point directly to the climate mechanisms most likely to significantly influence ice sheet SMB and dynamics in the coming decades to centuries. 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.