Classification of Boreal Summer East Asian Marine Heatwaves and Their Possible Mechanisms

Marine heatwave (MHW) is one of the severe extreme events under global warming, which affects the marine ecosystem and its relevant socio-economic losses. In particular, East Asian sea surface temperature is projected to increase more under the future climate change scenarios than any other ocean worldwide. According to concern for the increasing SST over East Asia, studies on the MHW are needed to minimize the damage. Thus, this study will classify the different spatiotemporal characteristics of East Asian MHWs and find their possible mechanisms using a self-organizing map. There are four dominant modes of MHWs over East Asia: (1) Global warming-like mode, (2) East China Sea mode, (3) East Sea/Japan Sea mode, and (4) Yellow Sea mode. We found the enhanced net downward shortwave radiation plays a crucial role in modulating the onset of the MHW everywhere over East Asia. When looking at the process of MHW occurrence, the spatial patterns related to the Yellow Sea mode and the East Sea/Japan Sea mode appear very similar, but the significant difference between the two modes is the presence or absence of preceding Indian monsoon heating. This means the Indian monsoon heating can precursor the MHWs over the East Sea/Japan Sea. As a result, this study has a significant implication for the predictability of the MHW over East Asia by finding precursors of the MHWs.