Southern Ocean High-Resolution (SOhi) Modeling Along the Antarctic Ice Sheet Periphery

The Southern Ocean plays a major role in controlling the evolution of Antarctic glaciers and in turn their impact on sea level rise. We present the Southern Ocean high-resolution (SOhi) simulation of the MITgcm ocean model to reproduce ice-ocean interaction at 1/24 degrees around Antarctica, including all ice shelf cavities and oceanic tides. We evaluate the model accuracy on the continental shelf using Marine Mammals Exploring the Oceans Pole to Pole data and compare the results with three other MITgcm ocean models (ECCO4, SOSE, and LLC4320) and the ISMIP6 temperature reconstruction. Below 400 m, all the models exhibit a warm bias on the continental shelf, but the bias is reduced in the high-resolution simulations. We hypothesize some of the bias is due to an overestimation of sea ice cover, which reduces heat loss to the atmosphere. Both high-resolution and accurate bathymetry are required to improve model accuracy around Antarctica. Warm water from the Southern Ocean melts the glaciers and ice shelves around the Antarctic margin, leading to glacier de-stabilization, and sea level rise. We present the Southern Ocean high-resolution (SOhi) model to better represent ocean circulation and ice-ocean interaction around Antarctica. We assess the accuracy of SOhi with in situ data from marine mammals and compare the results with three other ocean model simulations and to a baseline reference. All model results are slightly too warm on the continental shelf, but the higher-resolution models yield colder waters in better agreement with observations. We attribute the warm bias to an overestimation of the sea ice cover in the ocean models. An improved bathymetry also significantly improves model accuracy in Antarctica. High-resolution ocean models with more complete physics are in better agreement with in situ ocean data than coarser resolution models Accurate bathymetry is essential to capture circulation pathways and warm water intrusions on the Antarctic continental shelf High-resolution ocean models may remain too warm on the continental shelf because they over-predict the sea ice cover