Understanding Intermodel Diversity of CMIP5 Climate Models in Simulating East Asian Marginal Sea Surface Temperature in the Near Future (2020-2049)

Abstract

Using 14 Coupled Model Intercomparison Projections Phase 5 (CMIP5) climate models, we examined the intermodel diversity when simulating East Asian Marginal Seas (EAMSs) sea surface temperature (SST) in the near future period (2020-2049) under four different Representative Concentration Pathway runs. We classified two groups for the CMIP5 climate models: for models that simulate SSTs in the EAMS that are higher (H_EAMS) and lower (L_EAMS) than the ensemble mean, respectively. Results show that compared to L_EAMS, H_EAMS tends to simulate weaker westerlies in the western-to-central North Pacific, together with a weaker Aleutian Low intensity, which causes higher EAMS SSTs through a reduction in latent heat flux. Furthermore, H_EAMS is characterized by cooler SST, less precipitation, and stronger trade winds in the central-to-eastern tropical Pacific than in L_EAMS. We argued that the intermodel diversity of simulated tropical Pacific SST is associated with the diversity of EAMS SST, which is related to atmospheric teleconnections from the tropics to the western-to-central North Pacific. It is also found that the bifurcation latitude of the North Equatorial Current is lower in H_EAMS than in L_EAMS, which is associated with the difference of tropical Pacific mean state between H_EAMS and L_EAMS. A lower bifurcation latitude transports more warm water into the EAMS, resulting in warmer SSTs in the H_EAMS than in the L_EAMS. These results show the importance of correctly simulating the tropical Pacific mean state to reduce the uncertainty in EAMS SST during the near-future period.