Understanding an Intermodal Diversity of the Northwestern Pacific SST in CMIP5 RCP Scenarios

The sea surface temperature (SST) in the North Western Pacific (NWP), where the air-sea interactions are quite strong, is significantly changing in the recent past. In addition, there are still large uncertainties in future SST change in a warming climate. In this study, we investigate why the SST trends in the NWP region differ in Coupled Model Intercomparison Project phase 5 (CMIP5) four Representative Concentration Pathways (RCP) scenarios (i.e., RCP2.6, RCP4.5, RCP6.0, and RCP8.5). Fifth CMIP5 simulations are taken with four RCP scenarios as well as their historical run in the present climate. It is found that each CMIP5 model simulates various ranges of SST trends in spite of a same RCP scenario, indicating that there is an intermodal diversity of SST trends under four RCP scenarios. Further analysis indicates that the spread of SST trends appears significantly in the Kuroshio-Oyashio Extension (KOE) region. This suggests that the SST in the KOE region can be an important source to drive the intermodal diversity of SST trends in the NWP region in a changing climate. The details of physical analyses are also examined.