Experiment of Coupling Sea Ice Model CICE4.0 to LASG/IAP Climate System Model

The latest Los Alamos sea ice model (CICE4.0) is used to replace the sea ice model (CSIM4) in the LASG/IAP climate system model (FGOALS_g1.1), and the new coupled model has been integrated for the second half of the 20th century with observed forcings. Compared with FGOALS_g1.1, CICE4.0 improves polar climate simulations in the following aspects: 1) The area with small ice concentration near the ice edge is reduced remarkably. 2) Spatial distributions of both sea ice and sea surface temperature in the Southern Ocean resemble observations. However, there are some problems, including excessive sea ice in the North Atlantic and weakening of the North Atlantic meridional overturning relative to FGOALS_g1.1, which are largely due to large cold bias of sea surface temperature in the North Atlantic. As to atmospheric circulation, there is no significant improvements compared with FGOALS_g1.1. In addition, impacts of different shortwave radiation schemes, including CCSM3 and Delta-Eddington, on sea ice simulations in the new coupled model are discussed. The results show that the Delta-Eddington scheme results in thicker sea ice, colder sea surface temperature, and weaker North Atlantic meridional overturning as compared to the CCSM3 scheme.