Impact of Model Resolution on Antarctic Bottom Water Representation in Coupled Climate Models

Abstract

Antarctic Bottom Water (AABW) formation plays a crucial role in the climate system by driving the lower branch of the global overturning circulation, redistributing heat and salt, storing anthropogenic carbon dioxide, and delivering oxygen to the deep ocean. However, the representation of AABW formation in most climate models remains inadequate, since coarse spatial resolution fails to capture the intense ocean‐ice‐atmospheric interactions in a few small areas around the Antarctic continental shelf. This study evaluates the impact of model resolution on AABW simulations, using three climate models from the High Resolution Model Intercomparison Project (HighResMIP). By comparing the climatological mean state and projected changes of AABW in both low‐ and high‐resolution simulations, we find that climate models with approximately 4 km resolution better capture AABW formation and export processes along the Antarctic continental shelf than their lower‐resolution counterparts. High‐resolution climate models also project more pronounced future AABW changes than low‐resolution models. However, spurious AABW formation through open‐ocean deep convection becomes more prevalent in two of the three high‐resolution models, and thus the overall property biases in these models remain comparable to those in the low‐resolution models. Our results advance the understanding of how climate model resolution affects climate simulations and offer insights into the progress and challenges in representing AABW in climate models.