Variations of the Sea Surface Temperature in the Offshore Area of China and Their Relationship with the East Asian Monsoon under the Global Warming

Based on the long time series of mean Sea Surface Temperature (SST) and high-resolution wind field reanalysis data such as HadISST and ERA-40 reanalysis data, the variations of the SST in the offshore area of China and their relationship with the East Asian Monsoon (EAM) in winter (December to the next February) and summer (June to August) are analyzed using the Empirical Orthogonal Function (EOF) and linear regression analysis methods. The results show that: 1) The SST in the offshore area of China in winter or summer exhibited significant interannual and interdecadal variations, and experienced a climate shift in the mid-1980s. The areas with the strongest increase in SST are located in the East China Sea (ECS) in winter and in the Yellow Sea in summer. The SST increased by 1.96°C in winter for the period of 1955-2005 and 1.10 °C in summer for the period of 1971-2006. 2）The EAM has displayed distinct interannual and interdecadal variations with a weakening trend since the end of the 1980s in winter, and since the end of the 1970s in summer. In addition, the linear regression analysis indicates the relationship of the SST to EAM in winter on interdecadal timescale is closer than that on interannual timescale. The interdecadal weakening trend of EAM in winter contributes to the rise in SST in the offshore areas of China, particularly significant in the ECS. Moreover, the related areas of winter or summer mean SST on the interannual timescale in the offshore area of China to the EAM are located in the South China Sea (SCS), and the relationship in winter is much more obvious than that in summer. It is found that the interannual variation of SST in the SCS has obvious relation to the anomalies of the meridional southward and northward winds over the SCS and zonal migration of the subtropical anticyclone over the western Pacific.