Helen Shea: High and low Antarctic sea ice states in CMIP6 models
Total Antarctic sea ice extent increased over several decades, peaking in 2014, before declining sharply in 2016 and remaining persistently low thereafter, marking distinct high (2008–2016) and low (2017–2025) sea ice states. Previous work has highlighted contrasting ocean-sea ice behaviour in the Ross Sea, emphasising the importance of region-specific processes in interpreting recent sea ice trends and projecting future change. To assess whether climate models reproduce these regional processes, we analyse output from 19 CMIP6 models selected based on data availability. High and low sea ice states are identified in each model’s pre-industrial control simulations. Preliminary results indicate that deep ocean drift is present in some models, highlighting the need for selection criteria to exclude models in which sea ice variability is overly influenced by deep ocean processes. In addition, the relative influence of different regions on total sea ice extent varies across models, suggesting that total sea ice extent alone may not provide a directly comparable benchmark for defining high and low sea ice states relative to observations. Further work will look at regional ocean conditions for each model’s high and low sea ice states. These considerations will support more targeted model evaluation within the ACCESS community, strengthening the use of CMIP6 models for Antarctic sea ice research and future projections.