The effects of including Antarctic subglacial meltwater flux to the ocean in the Energy Exascale Earth System Model

Subglacial runoff beneath ice shelves is a source of freshwater, and therefore buoyancy, at the grounding line. Being released at depth, it accelerates an ascending plume along the ice-shelf base, enhancing entrainment of ambient waters, and increasing melt rates. By now it is understood that subglacial runoff is a key control on melt rate variability at the majority of Greenland's glaciers. However, its importance in present-day and future Antarctic melt rates is less clear. To address this point, we use the Energy Exascale Earth System Model (E3SM) and investigate the effects of Antarctic freshwater volume flux addition in both idealized setups and realistic, global, sea-ice ocean coupled configurations. For realistic Antarctic configurations, we use the subglacial hydrology model from the MALI ice-sheet model with both distributed and channelized drainage run at 4-20 km resolution to calculate steady state subglacial discharge across the grounding line under historical ice-sheet conditions.  This meltwater discharge is implemented as a freshwater flux in MPAS-Ocean, the ocean component of E3SM.