Assessing future climate changes in the northwestern North Pacific around Japan using a high-resolution regional ocean model

We assessed future climate changes in the northwestern North Pacific around Japan using a high-resolution regional ocean model. We used the SI-CAT10 version 2 data, which are the output of a 10-km resolution North Pacific OGCM driven by four CMIP5 atmospheric forcing datasets (MIROC5, MRI-CGCM3, GFDL-ESM2M, IPSL-CM5A-MR) under two RCP scenarios (RCP8.5 and RCP2.6). We estimated climate changes from the end of the 20th century (1986-2005) to the end of the 21st century (2081-2100) and obtained the following results. It is very likely that the sea surface temperature (SST) around Japan will increase in the 21st century. The rate of the mean SST rise is likely to be 3.6 ° C for RCP8.5, and 1.1 ° C for RCP2.6. The sea surface height (SSH) around Japan is likely to increase in the 21st century. The rate of the mean SSH rise is estimated to be 0.72 m for RCP8.5, and 0.38 m for RCP2.6. Most of this change is due to the globally averaged sea level rise, which is based on the estimates from IPCC-SROCC. The remain is due to the regional sea level rise associated with the northward shift of the subtropical gyre in the North Pacific. It is also likely that the sea ice area in the Sea of Okhotsk will decrease in the 21st century. The rate of the sea ice area in March is likely to decrease by 70 % for RCP8.5, and 28 % for RCP2.6, though the reliability of the projection is relatively low. The latitude of the Kuroshio Extension is likely to shift northward for RCP8.5, but the rate is almost within the range of the standard deviation. The Kuroshio Extension is likely to show no clear trend for RCP2.6.