The effect of increased resolution in the Energy, Exascale, Earth System Model (E3SM)

This study provides an overview of the coupled high-resolution version 1 of the Energy Exascale Earth System Model (E3SMv1) and documents the characteristics of a 50 year long high-resolution control simulation with time-invariant 1950 forcings following the HighResMIP protocol. Ocean and sea ice simulation is particularly improved at high resolution, due to better resolution of bathymetry, the ability to capture more variability and extremes in winds and currents, and the ability to resolve mesoscale ocean eddies. The most notable change is an ice-free Labrador Sea, which is a persistent problem at low resolution. Interestingly, certain aspects of the climate that were found to improve with resolution in other studies are unchanged with resolution or slightly degraded in E3SMv1. Most notable in this regard are a relative insensitivity in the size and strength of coastal upwelling and degraded El Nino. Finally we discuss the use of simulations that utilize the variable resolution capability of E3SM to diagnose the insensitivity of coastal upwelling seen across resolution.