Water masses and their long-term variability

We here review previous studies of spatiotemporal variability of surface and subsurface water properties in the East Sea (Japan Sea), including (1) sea surface temperature (SST) and mixed layer depth (MLD), (2) water masses, and (3) their long-term variability. Intra-annual, annual, and interannual variability of SSTs and SST-front structures are introduced together with a description of regionally adapted SST calibration methods. The MLD has distinct spatial patterns in its seasonal variability, which is determined by atmospheric forcing as well as advection effects. Water masses in the East Sea are listed in a comprehensive manner, covering not only subsurface water masses (e.g. Intermediate Waters) formed in the northern part of the sea but also near-surface water masses (e.g. Tsushima Warm Water) mostly originating from outside the sea. Where previous studies are available, we attempt to describe the definition, formation, and fate of the various water masses. Also, in terms of climate change in the East Sea, long-term variability found in the water masses or water properties is presented and its possible relationship with interannual to decadal variability of atmospheric forcing and heat content in the North Pacific is also considered.