The Global Climatic Response to Projected Transient Sea Ice Loss

In an attempt to isolate the global effects of projected Arctic sea ice decline, five RCP8.5 runs with and without sea ice change have been conducted extending from 1990 to 2100 using GFDL’s Coupled Model Version 3 (CM3). The difference between the sets of runs indicates that the reduction in sea ice drives most of the Arctic changes in the RCP simulations. The ice change also accounts for a significant fraction of the weakening of the Atlantic Meridional Overturning Circulation (AMOC) that occurred in the RCP8.5 ensemble. In both the RCP and fixed ice simulations the northern Inter-Tropical Convergence Zone (ITCZ) shifts equatorward, where the ice induced a statistically significant but relatively small fraction of the RCP8.5 warming in the tropical upper troposphere. Other atmospheric circulation changes and the surface climate response will be discussed as well.