Marked coastal warming off Tokai attributable to Kuroshio large meander

Abstract

The Kuroshio takes a large meander (LM) path since summer of 2017 for the first time since the 2004–2005 event and is the sixth LM event since 1965. It has been commonly recognized that a cool water pool is distributed broadly in the inshore region between the Kuroshio and southern coast of the Tokai district, Japan, during the LM periods. By using the recently-developed 1-km high-resolution sea surface temperature data, here we show marked coastal warming off the Tokai district during the LM periods, despite the Kuroshio not passing through the coastal area. The archived temperature-salinity profiles reveal that large positive anomalies off the Tokai district exist not only at the sea surface but also below 300 m and the water properties of which are those of the offshore Kuroshio water. The warm, salty waters are transported inshore by the westward Kuroshio which bifurcates at around 138° E, 34° N, during the LM path periods. We detect an increased upward heat release via turbulent heat fluxes along the coastal warming region from the new-generation atmosphere reanalysis data on a 25 km grid. These are common features to the past LMs and, furthermore, the region around the Kanto-Tokai districts becomes warmer than usual in warm seasons during the LM events. Our result reveals that the LM event can exert an influence upon the Japanese climate via the coastal air-sea interaction.