Modeling Ice-shelf Basal Melt Rates in the Energy Exascale Earth System Model (E3SM) v2, a Variable Resolution, Global, Coupled Climate Model
The processes responsible for freshwater flux from the Antarctic Ice Sheet (AIS) -- ice-shelf basal melting and iceberg calving -- are generally poorly represented in current Earth System Models (ESMs). As a step towards full ice-sheet coupling, we implemented static Antarctic ice-shelf cavities and the ability to calculate ice-shelf basal melt rates from the heat and freshwater fluxes computed by the ocean model in a coupled ESM, the Department of Energy's Energy Exascale Earth System Model (E3SM). In addition, we added the capability to prescribe forcing from iceberg melt, allowing us to realistically represent the other dominant mass loss process from the AIS. We make use of E3SM’s regional-refinement capability with an ocean/sea-ice grid that has high resolution (down to 12km) in the Southern Ocean around Antarctica, bypassing the need for parameterization of eddy-induced transport in this region. With these new capabilities, E3SM version 2 produces realistic and stable ice-shelf basal melt rates across the continent. We show preliminary results of modeled ice-shelf basal melt rates across a range of Antarctic ice-shelves under pre-industrial and historical climate forcing, as well as the impacts of these added capabilities on the region’s climate. The accurate representation of these processes within a coupled ESM is an important step towards reducing uncertainties in projections of the Antarctic response to climate change and Antarctica's contribution to global sea-level rise.