Investigating the importance of cloud-aerosol effects on the Arctic and Antarctic sea ice state in the Community Earth System Model version 2

Historical sea ice extents for the Arctic and Antarctic
Figure: Historical sea ice extents for the Arctic and Antarctic

In recent decades, sea ice in the Arctic Ocean has undergone rapid change. Sea ice extent has decreased in all months, and the thirteen lowest sea ice extents were recorded in the past thirteen years. Additionally, the sea ice has become thinner with the extensive loss of multiyear ice. These changes in sea ice will have local effects on the atmosphere and ocean as well as impacts on the large-scale atmospheric circulation. A model’s ability to recreate observed sea ice means state, temporal trends, and variability is essential for a credible simulation of future sea ice changes.

We are investigating two configurations of the newly released CESM2 to understand the Arctic and Antarctic sea ice. We find that in the Arctic there is a significant difference in the mean sea ice state between configurations that is related to the representation of springtime clouds. This is due to the inclusion of prognostic chemistry, which leads to more aerosols and cloud condensation nuclei. In the Antarctic, the two CESM2 configurations have similar mean state and trends in both sea ice extent and volume. However, neither is able to reproduce observed trends in the recent past. Understanding the reasons for the difference in Antarctic sea ice extent trends is an area we plan to explore further.