Characteristics and mechanisms of marine heatwaves in the East Asian Marginal Seas: regional and seasonal differences

Abstract

Marine heatwaves (MHWs) are spatially extended and temporally prolonged warm water temperature that pose a severe threat to marine ecosystems. Previous studies on MHWs in the East Asian Marginal Seas (EAMS) (East, Yellow, and East China Seas) have hardly considered seasonal variation. In this study, we examined the characteristics and mechanisms of MHWs in the EAMS, with a focus on seasonal changes and regional differences, based on 37 years (1982–2018) of optimum interpolation Sea Surface Temperature data. MHWs during the summer tended to be more intense and more frequent than in other seasons. For regional differences, long-term mean MHWs tended to be longer (27.5 days/year) and stronger (2.1 °C) in the East Sea than in the Yellow and East China Seas. MHWs over the EAMS during the summer are typically induced by increased surface shortwave radiation, which are caused by the reduction of the total cloud cover and latent cooling resulting from the weakened wind speed over the western flank of developing subtropical highs. In the East Sea, the MHWs in winter can be explained mainly by ocean dynamics related to the northward shift of the subpolar front, providing conditions for intensified warm water in the region. Our findings suggest that the MHW characteristics and mechanisms vary across seasons and regions.