Climatological descriptions on regional circulation around the Korean Peninsula

Abstract

The coastal ocean climatology of the temperature and salinity around the Korean Peninsula [Yellow Sea (YS), South Sea of Korea (SS), and East/Japan Sea (EJS)] is derived from conductivity-temperature-depth (CTD) profiles, which are collected from historical hydrographic surveys conducted over the last 20 years (1995 to 2014), using a multivariate regression analysis having basis functions of the temporal mean, annual and semiannual cycles, and linear trend. Based on the temporal means of the temperature and salinity profiles, the regional mesoscale circulation is reviewed with regard to the boundary currents, geostrophic currents, and density compensation and layered density structures associated with distinct water properties. The temperature in the YS exhibits a two-layer system, with decreasing annual amplitudes onshore above 25m and offshore below 25m because of annually modulated tidal mixing. The annual and semiannual variability in the temperature in the EJS primarily appears in the surface (upper 50m) and intermediate (between 50m and 200m) layers, respectively, because of annual surface heat fluxes and southward subsurface regional currents (e.g. the North Korea Cold Current). For the linear trend in the temperature, the onshore decreasing and offshore increasing tendencies in the EJS are described by the transport of long-term heat contents associated with the regional boundary currents. The multivariate regression analysis presented here explains approximately 90% of the variance in the temperature and salinity in the upper 100m (corresponding to most of the depths in the YS and SS).