Increased Model Resolution Amplifies Boreal Winter Arctic Precipitation and Atmospheric Circulation Response to Sea Ice Loss

The impact of future Arctic sea ice loss on local climate and large-scale atmospheric circulation has been extensively studied, including through the Polar Amplification Model Intercomparison Project (PAMIP). However, the influence of horizontal resolution on these responses remains largely unexplored. This study addresses this gap by conducting a set of PAMIP-type experiments in parallel using the Community Earth System Model, version 2.2 (CESM2.2), at global 110-km and Arctic-refined 14-km resolutions, with outputs regridded to a common grid to enable direct comparison. Sea ice loss is identified as the dominant driver of future Arctic precipitation increases in boreal winter. The Arctic-refined model exhibits a larger increase in precipitation over the sea ice loss region compared to the global 110-km model. This amplified response is linked to stronger updrafts and corresponding intensification of upward moisture transport. Additionally, daily precipitation variability increases in response to sea ice loss, with the change in the Arctic-refined model more than twice that in the global 110-km model, primarily connected to enhanced variability in vertical motion. Furthermore, both model resolutions capture Arctic amplification and associated dynamical responses, but the Arctic-refined model shows stronger warming and greater zonal wind deceleration over the polar cap. The thermodynamic budget analysis indicates that transient eddies associated with vertical motion are a major factor in the enhanced warming in the higher-resolution configuration. Collectively, these findings highlight the role of horizontal resolution in shaping Arctic precipitation and atmospheric circulation responses and underscore vertical motion as a key driver of this sensitivity. SIGNIFICANCE STATEMENT: This modeling study examines how increasing model horizontal resolution influences the atmospheric response to future Arctic sea ice loss. Using the Community Earth System Model, version 2.2 (CESM2.2), we conducted two sea ice loss experiments, one with a typical climate model resolution and one with very high resolution over the Arctic, following an experiment protocol similar to the Polar Amplification Model Intercomparison Project (PAMIP). The results show that higher resolution leads to greater increases in Arctic precipitation and its variability in response to sea ice loss. Additionally, the simulations with high resolution over the Arctic exhibit stronger lower-tropospheric temperature and circulation responses over the polar cap compared to the coarser-resolution simulations. These enhanced responses are likely linked to resolution-dependent differences in vertical motion. Our findings advance the understanding of high-resolution modeling and highlight the critical role of horizontal resolution in accurately simulating climate and climate change in the Arctic.