Contributions of Ice Thickness to the Atmospheric Response From Projected Arctic Sea Ice Loss

A large ensemble of simulations from a high-top atmospheric general circulation model are conducted to compare the atmospheric responses from loss of Arctic sea ice thickness and sea ice concentration. The response to projected sea ice thickness loss indicates substantial surface warming over the Arctic Ocean and up to 1 degrees C of cooling in Eurasia. While the dynamic circulation response from sea ice thickness loss is smaller in magnitude, it has a similar spatial anomaly pattern as that due to sea ice concentration loss. This pattern resembles the negative phase of the Northern Annular Mode. The simulations reveal that sea ice thickness loss enhances the thermodynamic and large-scale circulation response from sea ice anomalies. These results stress the importance of considering a realistic sea ice thickness distribution in future atmospheric general circulation model sea ice perturbation experiments. Plain Language Summary The atmospheric response to the loss of Arctic sea ice remains uncertain in current climate change assessments. Prior studies addressing the response have mostly focused on changes in sea ice concentration or the fraction of sea ice cover in a defined area. However, this neglects the role of sea ice thickness, which is projected to substantially thin during the 21st century. Using a series of climate model simulations, this study provides a comprehensive comparison of the atmospheric response to the loss of Arctic sea ice thickness and sea ice concentration. The experiments show a nonnegligible influence of sea ice thickness on near-surface warming of the Arctic and the large-scale atmospheric circulation. This study demonstrates the importance of accurately representing changes in Arctic sea ice thickness in future climate model studies.