A coupled energy balance climate‐sea ice model: Impact of sea ice and leads on climate

Abstract

A coupled climate‐sea ice model that includes land‐sea resolution in the atmosphere, a mixed layer ocean, and a ground layer is used to investigate the impact of sea ice and leads within the ice pack on climate. Results show that a feedback process between the ocean and atmosphere exists, called the lead‐temperature feedback, such that changes in the winter minimum lead fraction can cause large changes in the simulated annual zonally averaged surface air temperature in the north polar regions. Compared to a control case where the minimum lead fraction is 1.1%, these changes in temperature range from a decrease of about 1.0°K, when leads are eliminated, to an increase of 1.0°K, when the winter minimum lead fraction is increased to 4.3%. Seasonally, this temperature change ranges up to 2.0°K. An examination of the surface energy fluxes shows that the changes in the sensible heat flux, in response to changes in the lead fraction, contribute the most to these temperature changes. The absorbed solar radiation is also affected by the changes in the winter minimum lead fraction; however, the small changes in lead area during the winter and the period of open ocean during the summer reduce its impact. The increase in the sensible heat flux to the atmosphere, along with the changes in the other fluxes, in response to increases in winter minimum lead fraction, forms the positive lead‐temperature feedback between larger lead area and warming. This feedback process has major implications for both polar and global climate.