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Although tides are believed to be the most important source for diapycnal mixing in the ocean, few studies have directly simulated open-ocean circulation including tides. Because the East/Japan Sea (EJS) has been considered to be a ''miniature ocean,'' tidal effects on the intermediate water of the EJS are investigated by using an eddy-resolving ocean general circulation model that can take account of M2 and K1 tides as well as oceanic flows. The simulated temperature and salinity in the intermediate layer are significantly improved by including tides. The improvement results from the combined effect of two internal tides. The M2 internal tide, propagating into the interior of the EJS, enhances vertical mixing and brings watermass characteristics closer to those observed. The K1 internal tide, trapped along the coast, induces southwestward flow along the Russian coast in the upper layer and thereby enhances the so-called Liman Current, which transports fresh waters with density conducive to the ventilation of intermediate waters in the EJS. [ABSTRACT FROM AUTHOR]

Abstract: In order to reconstruct spatial and temporal changes in sea surface temperature (SST) of the East Sea (Japan Sea) on glacial–interglacial time scale, alkenone temperature records from the both Korean and Japan margins have been investigated for the period over the last 130kyr. Results show that the temperature gradient between the Korean and Japan margins was relatively small (~2°C) during the warm interval of the interglacial period (MIS 5e). But it was large (~10°C) during the transitional period from the interglacial to the glacial (MIS 5a and b). The temperature of the Korean margin was colder than that of the Japan margin during the transitional period. Based on the reconstructed alkenone temperature, temporal changes in surface circulation and subpolar front (SPF) have been investigated. During the interglacial period when sea level was higher than today (MIS 5e), the influx of the Tsushima Warm Current (TWC) was enhanced and the both Korean and Japan margins were influenced by the warm water. At that time, the SPF appears to be located in the northern part compared to today. During the transitional period when the sea level was lower than today (MIS 5a and b), the TWC volume transport was reduced contributing to the lower SST. Its effect on the surface temperature appears to be larger along the Korean margin than the Japan margin, indicating that the strength of the East Korea Warm Current appears to be strongly correlated with the TWC volume transport. The SPF would displace southward orienting from southwest to northeast at that time. During the glacial period when the sea level was very lower (~100m deep), the influx of warm water was almost completely restricted and the cold water expanded into the southern area. The SPF would disappear at that time. Model simulation results also support the relationship between the TWC volume transport and surface circulation and the SST. [Copyright &y& Elsevier]

Abstract: To test the applicability of alkenones as a proxy for past sea surface temperature (SST) in the East Sea (Japan Sea), this study investigated the season and depth of alkenone production in the area. Surface and subsurface seawater samples were collected from the East Sea during cruises carried out by the National Fisheries Research and Development Institute of Korea in 2008–2010. Surface samples were filtered for suspended material at two-month intervals. Subsurface samples were collected at water depths of 20, 50, 70 and 100m by CTD bottle casts at two stations, one a coastal station and the other an offshore station. The results of alkenone analysis show that the concentration of total C37 alkenones was generally high in the surface mixed layer and decreased with depth, indicating that alkenones were most likely produced in or close to the surface mixed layer. Alkenone concentration varied seasonally: high in spring to fall and significantly reduced in winter. Comparisons of alkenone-based temperatures with in situ seawater temperatures show that alkenone temperatures measured from suspended particles in the surface waters were close to in situ SST in summer but were lower in winter. During winter, when alkenone production is significantly reduced, alkenones may be suspended for relatively long times and are likely to be advected from the north by eddies from Subpolar Front meanders. In summer when new production of alkenones increases, the settling velocity of alkenones appears to increase and residence time becomes shorter than in winter, suggesting that particles are less likely to be significantly advected at that time. Importantly, at the offshore station, coretop alkenone temperature corresponds to annual-averaged SST, while at the coastal station it corresponds to summer-to-fall averaged SST. [Copyright &y& Elsevier]