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Marine heatwaves (MHWs) are among the most severe climatic events under global warming conditions; they damage marine ecosystems and result in socioeconomic losses. In East Asia, the sea surface temperature (SST) has increased significantly and is projected to increase further. Considering such increases in SST over East Asia, studies on MHWs are needed to minimize the damage caused. In this study, we classified the spatiotemporal characteristics of East Asian MHWs during boreal summer with a self-organizing map for 39 years (1982–2020) and determined their unexplored possible mechanisms. Four dominant modes of MHWs across East Asia were identified: the 1) Subtropical Gyre, 2) East China Sea, 3) East Sea/Japan Sea, and 4) Yellow Sea modes. The total annual number of MHW days has increased by about 1.23 days yr-1. The significant trend is mainly determined by the Subtropical Gyre mode, whereas other modes do not exhibit significant trends. We found that the East China Sea mode could be attributed to a strong East Asian summer monsoon via ocean stratification by the low-salinity water from the Yangtze (Changjiang) River. The East Sea/Japan Sea and Yellow Sea modes could be linked to remote forcings over the subtropics, leading to persistent anticyclonic circulation over East Asia. The anomalous anticyclone contributed to the MHW occurrences by enhancing downward shortwave radiation and reducing entrainment cooling caused by Ekman downwelling. These findings have important implications for distinguishing the characteristics of East Asian MHWs and reveal the possibility of predicting them by identifying their precursors. [ABSTRACT FROM AUTHOR]

BKV is widespread among humans, infecting children asymptomatically and then persisting in renal tissue. Based on the serological or phylogenetic method, BKV isolates worldwide are classified into four subtypes (I–IV), with subtypes I and IV further divided into several genetically-distinct subgroups. Since, similarly to JCV, a close relationship exists between BKV lineages and human populations, BKV should be useful as a marker to trace human migrations. To elucidate ancient human migrations in northeast Asia, urine samples were collected from immunocompetent elderly patients in Shanghai, China; Anyang, South Korea; and various locations in Japan. Partial and complete BKV genomes from these samples were amplified and sequenced using PCR, and the determined sequences were classified into subtypes and subgroups by phylogenetic and SNP analyses. In addition, based on an SNP analysis, the major subtype I subgroup (I/c) was classified into two subdivisions, I/c/Ch and I/c/KJ. The distribution patterns of BKV subgroups and subdivisions among the three regions were compared. Some aspects of the subgroup and subdivision distribution were more similar between Korea and Japan, but others were more similar between China and Korea or between China and Japan. Based on these findings, we inferred various northeast Asian migrations. Most of the JCV-based inferences of northeastern Asian migrations were consistent with those based on BKV, but the previously suggested migration route from the Asian continent to the Japanese archipelago seemed to need revision. [ABSTRACT FROM AUTHOR]