The antarctic ICE sheet is a significant contributor to sea level rise at present and has the largest potential for future sea level rise in the coming centuries. Most of the mass loss is governed…

The University of California, Irvine (UCI) was awarded a $1.02M research grant by a civilian federal agency with an ultimate completion date of March 31, 2026. This grant, which was not set aside for any specific designation, supports a critical climate science initiative focused on mapping the bathymetry and sub-ice-shelf cavities of the Antarctic ice sheet. The research addresses a significant gap in understanding sea level rise mechanisms by utilizing multiple data sources, including airborne gravity data from Operation IceBridge (2009-2019), magnetic anomalies, the BedMachine Antarctica bed topography dataset, multi-beam echo-sounding data from the International Bathymetry Chart of the Southern Ocean, seismic data, and novel marine mammal diving depth observations. The resulting bathymetry product will be delivered as a Level 4 dataset to the National Snow and Ice Data Center (NSIDC) for use by ice sheet and ocean modelers.

This research directly addresses critical limitations in current ice sheet and Earth system models, which fail to adequately represent sub-ice-shelf cavity geometry and the pathways by which warm Circumpolar Deep Water reaches glacier grounding lines, driving glacier acceleration and retreat. By comprehensively mapping these subsurface features and continental shelf topography, UCI's work will provide essential data infrastructure for improving predictive models of Antarctic ice mass loss and associated sea level rise—a key research priority for federal climate science agencies. The grant represents UCI's demonstrated expertise in advanced geophysical research and its role as a strategic partner for federal climate and oceanographic research initiatives.

The antarctic ICE sheet is a significant contributor to sea level rise at present and has the largest potential for future sea level rise in the coming centuries. Most of the mass loss is governed by the acceleration of its glaciers, not by changes in surface mass balance, and the glacier acceleration is caused by the enhanced advection of subsurface, warm, salty water of antarctic circumpolar current origin, or CDW, onto the continental shelf, beneath the ICE shelf cavities, and reaching the glacier grounding lines. As more warm CDW reaches the grounding lines, the glaciers retreat and speed up, which is conducive to more retreat, especially if the glaciers are resting on retrograde bed slopes, i.e. bed elevation drops in the inland direction. Ippc-class models and earth system models fail to reproduce this evolution of antarctic ICE for two major reasons: 1) the shapes of the sub-ICE-shelf cavities that potentially host CDW and the presence of troughs on the continental shelf that control the advection of CDW are not well known and ICE shelves are not well represented in earth system models 2) ocean models need to be run at a high spatial resolution on the continental shelf to model offthe- shelf to on-the-shelf ocean heat transport, but this is not the focus of ocean models in esms. Here, we will map the shape of nearly all sub-ICE-shelf cavities using a new compilation of airborne gravity data, including operation icebridge (OIB) data from 2009-2019, combined with a new compilation of magnetic anomalies, a new bed topography on land named bedmachine antarctica, multi-beam echo-sounding data at sea from the international bathymetry chart of the southern ocean, existing pan-antarctica seismic data on the continental shelf and on ICE shelves, and novel seal mammal diving depth data from marine mammals exploring the oceans pole to pole near ICE shelf fronts. The bathymetry will be delivered as a level 4 product to nsidc for ICE sheet/ocean modelers to use in antarctica. Secondly, we will run a 1 KM resolution eddy-resolving, cavity-inclusive model of the southern ocean forced by RE-analysis using the mitgcm ocean model. At the northern boundary, the model will be constrained by an extension of the southern ocean state estimate to 2003-2021 via massive data assimilation. To evaluate the 1-KM model results, we will compare the modeled ICE shelf melt rates with pan-antarctic ICE shelf melt rates calculated from remote sensing data: time series of ICE velocity from measures-3, ICE elevation from icesat-1, OIB, icesat-2, worldview/geoeye and tandem-x, and ICE thickness from bedmachine. The results will provide bathymetry, ICE shelf melt rates, and guidelines to improve the representation of ICE shelves in ESM, e.g. geos-5 which uses mitgcm. As part of the ocean analysis, we will investigate the relationship between climate variables and ICE shelf melt rates using the adjoint method to reduce uncertainties in projections. We will combine the derived ICE shelf melt rate sensitivities with climate projections from CMIP6 and CMPI6/scenariomip ensemble members to project ICE shelf melt under different emission scenarios. Overall, the results of this project will be a major step forward in the modeling of antarctic ICE/ocean evolution in a warming climate, with ocean state around antarctica, ICE-shelf melt rates, reliable bathymetry with ICE shelf cavities, and constraints to better project the coming decades of antarctic evolution with lower uncertainties. This work will enhance our current modeling capabilities in antarctica, capitalize on NASA and non-NASA space and airborne observations, data assimilation techniques, and ESM development to pave the way for more realistic projections of antarctic ICE sheet evolution and its impact on sea level rise. This work will contribute to NASA overall research objective to better understand the role of oceans, atmosphere and ICE in the climate system and its impact on global sea level rise.