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The East China Sea (ECS) and Yellow Sea (YS) are East Asian marginal seas and mainly cover shallow continental shelves with depths of

International audience; An up-to-date map of the Antarctic Circumpolar Current (ACC) fronts is constructed from the latest version of mean dynamic topography (MDT) from satellite altimetry and reveals the narrowest ACC width in the Udintsev Fracture Zone (UFZ), with the strongest concentration of the three major ACC fronts within a limited distance as short as 170 km, about 40% narrower than that at Drake Passage. At 144°W, at the entrance of the UFZ, which lies between the Pacific-Antarctic Ridge (PAR) and its eastwardly offset segment (offset PAR segment), there is a triple confluence of the Subantarctic Front, Polar Front, and Southern ACC Front. Downstream of this longitude, the Subantarctic Front progressively meanders northward over the relatively shallow offset PAR segment before channeling through the Eltanin Fracture Zone, thus diverging from the Polar Front which proceeds through the UFZ. In situ observations from two recent cruises at 144°W confirm the satellite altimetry-derived frontal circulation in the UFZ region and yield a baroclinic transport relative to the bottom of 113 × 10 6 m 3 /s, comparable to that through Drake Passage. The hydrographic sections show no Antarctic bottom water colder than 0.2°C. Characteristics of major water masses are described, and the implications for their potential downstream modifications at Drake Passage are discussed in terms of the meridional overturning circulation across the ACC. Mesoscale eddy activity with periods shorter than 90 days is predominantly concentrated in the immediate downstream area of the offset PAR segment, suggesting a substantial poleward eddy heat flux there.

One year long time-series current data were obtained at two stations (K1 and K2) located in the Usan Trough in the area north of Ulleungdo in the East Sea from September 2006. The observed data reveal enhanced seafloor flows in both stations with variabilities of about 20 days which is possibly governed by the topographic Rossby wave. After February 2007, strong flow in the upper layer in St. K1 appears throughout the mooring period and this is due to the passage of the warm eddy comparing with satellite sea surface temperature data. During this period, no significant correlation between the current in the upper layer and those in two deep layers is shown indicating the eddy does not affect flows in the deep ocean. It is also observed that the flow direction rotates clockwise with depth in both stations except for the upper of the K1. This implies that the deep flow does not parallel to the isobaths exactly and it has a downwelling velocity component. The possibility of the flow from the Japan Basin to the Ulleung Basin across the Usan Trough is not evidenced from the data.

Seawater samples were collected at discrete depths from five stations across the polar front in the Drake Passage (Antarctic Ocean) by the 20 th Korea Antarctic Research Program in December, 2006. Nitrate concentrations of seawater increase with depth within the photic zone above the depth of Upper Circumpolar Deep Water (UCDW). In contrast, δ¹?N values of seawater nitrate decrease with depth, showing a mirror image to the nitrate variation. Such a distinct vertical variation is mainly attributed to the degree of nitrate assimilation by phytoplankton as well as organic matter degradation of sinking particles within the surface layer. The preferential ¹⁴NO₃? assimilation by the phytoplankton causes ¹?NO₃? concentration to become high in a closedsystem surface-water environment during the primary production, whereas more ¹⁴NO₃? is added to the seawater during the degradation of sinking organic particles. The water-mass mixing seems to play an important role in the alteration of δ¹?N values in the deep layer below the UCDW. Across the polar front, nitrate concentrations of surface seawater decrease and corresponding δ¹?N values increase northward, which is likely due to the degree of nitrate utilization during the primary production. Based on the Rayleigh model, the calculated e (isotope effect of nitrate uptake) values between 4.0‰ and 5.8‰ were validated by the previously reported data, although the preformed δ¹?NO₃? initial value of UCDW is important in the calculation of e values.

Conductivity-temperature-depth (CTD) data obtained along a meridional section in the eastern tropical Pacific in July 2003 have been analyzed to identify various water masses, and to examine the hydrographic structure and zonal geostrophic currents in the upper 1000 m. Water mass analysis shows the existence of subtropical and intermediate waters, characterized by layers of subsurface salinity maximum and minimum, originating from both hemispheres of the Pacific. Vertical section of temperature in the upper 200 m shows the typical trough-ridge structure associated with the zonal current system for most of the tropical Pacific. Water with the lowest salinity of less than 33.6 was found in the upper 30 m between and in a boundary zone between the North Equatorial Current and North Equatorial Countercurrent. Temporal changes in water properties observed at over a period of 9 days suggest both the local rainfall and horizontal advection is responsible for the presence of the low-salinity water. Development of a barrier layer was also observed at . In the North Equatorial Current region a local upwelling was observed at , which brings high salinity and cooler subtropical water to the sea surface. A band of countercurrent occurs in the upwelling region between and

[1] Episodes of high-frequency internal waves, which lasted approximately 3 hours, were detected in the northern East China Sea during a specific phase of the barotropic tide (i.e., low tide at 32°N, 125°E). The observed internal waves influenced the whole water column. The wave packets were presumably generated near the ocean shelf break, approximately 200 km to the southeast of the test site. During several internal wave episodes, which coincided with the neap tide, large-amplitude solitary wave-like features emerged preceding higher frequency internal waves. Shear instability of tidal currents is explored as a possible mechanism for sustaining or regenerating internal waves in the packets during the course of their propagation. It is suggested that rotating velocity field of tidal current supports sufficient vertical shear within wave packets to cause outbreaks of K-H instability. These instabilities may gradually transition to more symmetric Holmboe waves, following the increase of the bulk Richardson number.