Sea Ice Climate of the Energy Exascale Earth System Model, Version 2
The Energy Exascale Earth System Model (E3SM) has undergone significant development during the past year, including improvements to the atmosphere, land, ocean, and sea-ice components to create Version 2 of the fully coupled model. We present a detailed analysis of the marine surface polar climate of E3SM V2 at the standard model resolution of 30km in polar regions and 60km in the mid-latitudes for the ice and ocean components, 100km for the atmosphere component. We compare this configuration with coupled simulations using a new North American regionally-enhanced mesh, featuring 14km ice-ocean resolution over the Gulf of Mexico, the Gulf Stream, the Arctic Ocean, and the U.S. and Canadian Pacific Coasts, and resolved Trans-Arctic shipping channels, and improved land-hydrology resolution. With these two mesh configurations, key features of the E3SM V2 Arctic and Southern Ocean sea ice zones are compared with E3SM Version 1 CMIP6 submissions at standard resolution, and the high-resolution version of E3SM Version 1 at 6km/25km ocean/atmosphere resolution in high latitudes. Our results demonstrate that a significant bias in the northern hemisphere ice edge is greatly improved with a more accurate eddy parameterization at 30km resolution, or simply by not parametrizing eddies within the high resolution (14km) region of our enhanced northwestern quadrant. As part of our analysis, we include a systematic breakdown of the impact of consistent radiative transfer models between snow on land and sea ice, of improved snow treatment in the presence of ridge sea ice, of a higher resolution land-hydrology model feeding the Arctic Ocean, and analysis of the radiative balance within the sea ice zone. Our analysis spans four different model configurations, indicating the impact of regional mesh enhancement on internal variability and model accuracy, making use of a suite of observations of the atmosphere-sea ice-oceanic boundary layer system.