Major Driver Leading to Winter SST Variability in the Kuroshio Recirculation Gyre Region and Its Decadal Changes: Refreshening Versus Spring-Initiated Reemergence Processes

Abstract

The analyses using reanalysis data and one-dimensional ocean model during the past decades (1963–2012) revealed that the epoch-dependent refreshening and reemergence mechanisms alternatively influenced the winter sea surface temperature (SST) in the Kuroshio recirculation gyre region. During 1971–1985, the refreshening mechanism due to the strong East Asian winter monsoon significantly contributed to the interannual winter SST variability, consistent with previous works. In contrast, the spring-initiated reemergence process better explains the winter SST variability for 1991–2005, a period corresponding to a declined winter monsoon. The classical winter-to-winter reemergence did not occur during either studied period; thus, the observed spring-to-winter reemergence is an original feature in the Kuroshio recirculation gyre region. The winter monsoon-related strong atmospheric forcing and prominent year-to-year variability of spring SST are important prerequisites for the regional refreshening and reemergence of the winter SST anomaly, respectively.