Changes and Extreme Events in Temperature of an Ocean Reanalysis Product around Japan

Because recent changes in ocean temperature around Japan are affecting fisheries and precipitation over the land, grasp of the changes is needed. A new ocean reanalysis product JCOPE2M (*1) with a 1/12-degree horizontal resolution was analyzed to investigate changes and extreme events around Japan. The reanalysis data are available from 1993 to present. The positive temperature trends (secure trend and/or decadal variation) from 1993 to 2018 more than a few degree/100-year were found along the Kuroshio, the Kuroshio Extension, the subarctic front, and in the Japan Sea. While these features are similar to NOAA ERSST V5 (2-degree resolution) and NOAA OISST V2 (1/2-degree resolution), JCOPE2M reanalysis with the higher resolution can capture sharper structures. Another benefit of the ocean reanalysis is that analyses of subsurface depths are possible. Higher trends more than several degrees/100-year were found at 100 m depth. The significant increases in the number of events of marine heatwaves were found in the northern Japan Sea and around the subartic front.
*1 http://www.jamstec.go.jp/jcope/htdocs/e/distribution/index.html