An Assessment of Antarctic Sea-ice Thickness in CMIP6 Simulations with Comparison to the Observations

This study assesses less-explored Southern Ocean sea-ice parameters, namely sea-ice thickness and volume, through a comprehensive comparison of 39 CMIP6 models with observation-based sea-ice products. Findings indicate that models replicate the mean seasonal cycle and spatial patterns of sea-ice thickness, particularly during its maxima in February. However, some models simulate implausible historical mean states compared to satellite observations, leading to large inter-model spread. September sea-ice thickness is consistently biased low across the models. Our results show a positive relationship between modeled mean sea-ice area and thickness in September (i.e., models with more area tend to have thicker ice); in February this relationship becomes negative. While CMIP6 models demonstrate proficiency in simulating Area, thickness accuracy remains a challenge. This study, therefore, highlights the need for improved representation of Antarctic sea-ice processes in models for accurate projections of thickness and volume changes.