Non-stationary Relationship between Cloud Radiative Forcing and Sea Ice Concentration in the Arctic Ocean during Summer

Abstract

In this study, we have examined changes in the relationship between surface cloud radiative forcing (CRF) and sea ice concentration (SIC) / surface temperature (TS) in the Arctic Ocean during summer (June-July-August-September). The monthly observation data of shortwave (SW) and longwave (LW) CRFs, SIC and TS were obtained over the Arctic Ocean (North of 70°N) from the Extended AVHRR Polar Pathfinder (APP-x) product for the period of 1982？2012. We found that the relationship between CRF and SIC/TS changed over time. The negative (positive) correlation between SW CRF (LW CRF) and SIC has become stronger over the Pacific sector of the central Arctic since the late 20th century. This indicates that the cloud radiative effect by LW radiation has been reduced, whereas that by SW radiation has increased over the Pacific sector of the Arctic Ocean. In addition, the impact of LW CRF to SIC has increased over the marginal sea areas. Similar relationship is also found in the TS data. This recent change in the relationship based on the satellite observation is not reproduced in current climate models. Rather, most models tend to overemphasize the cloud radiative effect by LW radiation on SIC/TS during summer.