Interannual variability of the Korea Strait Bottom Cold Water and its relationship with the upper water temperatures and atmospheric forcing in the Sea of Japan (East Sea)

Abstract

A 35 yearlong temperature data set is analyzed to investigate the long-term temperature variability in the Korea Strait and its relationship with the temperature variability in the upper layer of the Sea of Japan (East Sea). The second cyclostationary empirical orthogonal function mode of the vertical temperature section in the Korea Strait describes the interannual variability of the Korea Strait Bottom Cold Water (KSBCW). According to the corresponding principal component time series, the strength of the KSBCW fluctuates yearly with a major spectral peak around 3 years. Multiple regression analysis shows that the interannual KSBCW variability is closely linked with the temperature variability in the southwestern region of the Sea of Japan (East Sea) at about 50-100 m depth. Along 40 degrees N, the source of the KSBCW is traced at about 50 m, extending eastward from the east coast of Korea to about 135 degrees E. At 37 degrees N, the source is traced at a deeper level (about 50-100 m), confined more toward the east coast of Korea with a hint of double core characteristics. The interannual KSBCW variability is also related to the southward wind stress along the east coast of Korea. It appears that strong cooling/warming of upper water temperature induced by the basin-scale wind stress results in the interannual KSBCW variability. This connection is verified by showing a reasonable interannual covariability between the KSBCW and the basin-scale wind stress.