동해 북서부 중규모 순환 분석

Abstract

The spatiotemporal variability in the northern part of the East Sea(ES) and its mechanism are investigated using empirical orthogonal function (EOF) analysis of sea surface height (SSH) measured by satellite altimetry during the 1993-2017, meteorological and oceanic reanalysis data. The results show that there is a noticeble mesoscale variability in the northwestern region of the ES during wintertime as well as the prevailing semiannual variation in the cyclonic gyre in the northern ES. The variability of the mesoscale aspects which appears form of a dipole structure shows a maximum from October to December and small values in warm period with a minimum in August. The timing of the development and spatial structure of the EOF mode correspond well to the mesoscale structures observed by Argos drift buoys which appear in the northwestern region of the ES, such as anticyclonic eddies accompanied by the northward coastal current reversal and the northwestern thermal front(NWTF). Some of these mesoscale aspects are closely related to atmospheric submesoscale disturbance south of Vladivostok. The wind forcing is dominant on the shelf areas of the northwestern region of the ES where the dipole of wind stress curl exists during wintertime. The NWTF is accompanied by a cold anomaly in the eastern side and a weak warm anomaly in the western side. NWTF is consistent with the NWSPF mentioned in Park et al. (2004). The cold and warm anomalies are generated by the dipole wind stress curl structure; the cold anomaly may be generated by the Ekman divergence due to the positive wind-stress curl, while a warm anomaly appears below the negative wind stress curl in the process of the downwelling imposed by the anticyclonic vortex off Vladivostok. And anticyclonic eddies accompanied by northward coastal current reversal are generated by negative wind stress curl. Also, strong wind-driven Ekman convergence plays an important role in thickening the East Sea intermediate water(ESIW).