Long-term trends and spatial patterns of marine heatwaves in the East Sea

Anthropogenic climate change has directly and indirectly derived extreme oceanic events. Among them, marine heatwaves (MHWs), which are defined as anomalously warm water events, persist for days to months to even years and extend over thousands of square kilometers, leading to negative impact on marine ecosystems and fisheries. East Sea, a semi-enclosed marginal sea in the northwestern Pacific Ocean, is well known as “a miniature ocean”, showing a number of physical dynamics (e.g., deep-water formation, gyre circulation, subpolar front, and eddies). The East Sea is frequently referred to as an ideal place to investigate the responses of marine environment to anthropogenic climate changes due to short residence time of seawaters, ~100 years. However, there is little information about occurrences and characteristics of MHWs and their impacts on marine ecosystem in the East Sea. Here, using available satellite-based data, we (1) investigate the long-term trends and spatial patterns of MHWs that have occurred in the East Sea during the periods of 1983‒2018, (2) characterize duration, frequency, intensity, rate of evolution, and spatial extent of the East Sea’s MHWs, and (3) investigate the impacts of MHWs on long-term chlorophyll-a variations in the East Sea.