Japan/East Sea Water Masses and Their Relation to the Sea's Circulation

Abstract

The Japan/East Sea is a major anomaly in the ventilation and overturn picture of the Pacifi c Ocean. The North Pacifi c is well known to be nearly unventilated at intermediate and abyssal depths, refl ected in low oxygen concentration at 1000 m (Figure 1). (High oxygen indicates newer water in more recent contact with the atmosphere. Oxygen declines as water "ages" after it leaves the sea surface mainly because of bacterial respiration.) Even the small production of North Pacifi c Intermediate Water in the Okhotsk Sea (Talley, 1991; Shcherbina et al., 2003) and the tiny amount of new bottom water encountered in the deep Bering Sea (Warner and Roden, 1995) have no obvious impact on the overall oxygen distribution at 1000 m and below, down to 3500 m, which is the approximate maximum depth of the Bering, Okhotsk, and Japan/East Seas. In contrast, the nearly isolated Japan/East Sea is very well ventilated at all depths from the surface to the bottom. Oxygen is higher than anywhere else in the Pacifi c, even in the South Pacifi c, where intermediate-layer ventilation yields relatively high oxygen content at 1000 dbar (roughly 1000-m depth). It is necessary to look much farther away, to the North Atlantic and best-ventilated sectors of the Antarctic, to fi nd deep ventilation comparable to the Japan/East Sea's. Because it is ventilated from top to bottom and located at mid-latitude, the Japan/East Sea has many similarities to the North Atlantic Ocean (e.g., Riser and Jacobs, 2005; Min and Warner, 2005). Both have (1) infl ow of warm, saline surface waters from the south; (2) subduction that ventilates the upper ocean in the subtropics; (3) subtropical mode waters; (4) a subpolar front south of which a low-salinity water mass is formed; (5) cooling and precipitation that cause a colder, fresher subpolar north; (6) subpolar mode waters with comparable winter mixed-layer thicknesses; and (7) deep convection and ice formation that ventilate the entire water column. The Japan/East Sea differs from the North Atlantic in two major respects: (1) the powerful northward eastern boundary current in the Japan/East Sea, the Tsushima Warm Current, distorts the subtropical gyre, and (2) the Japan/East Sea is isolated from all subsurface waters in the North Pacifi c. Therefore, the Japan/East Sea's salinity is nearly uniform below the shallow sill depth (140 m) of Tsushima Strait. The Japan/East Sea has a full temperature range, however, because surface waters cool to freezing and some of this very cold water becomes bottom water. In its isolation, the Japan/East Sea most closely resembles the Mediterranean Sea-both seas form dense water as a result of convection during winter cold-air outbreaks (Talley et al., 2003; Marshall and Schott, 1999).

Summer primary productivity and phytoplankton community composition driven by different hydrographic structures in the East/Japan Sea and the Western Subarctic Pacific

“…It contains three deep (>2000 m) basins (Figure 1): the Ulleung Basin (UB), the Yamato Basin (YB), and the Japan Basin (JB). Hydrographic features of the EJS (e.g., deep water formation, independent thermohaline circulation, a subpolar front, and mesoscale eddies) are similar to those of the North Atlantic Ocean [Min and Warner, 2005;Riser and Jacobs, 2005;Talley et al, 2006]. Because of these ocean-like features, the EJS is considered to be an ideal place for studying oceanic processes as a ''Miniature Ocean'' [Kim and Kim, 1996;Lee et al, 2009].…”

A newly observed physical cause of the onset of the subsurface spring phytoplankton bloom in the southwestern East Sea/Sea of Japan

“…The intermediate and deep layers are all below the main pycnocline, or partly include the lower pycnocline. Water masses occupying the intermediate and deep layers south of the subpolar front are all formed in the Japan Basin Talley et al, 2006). The East Sea Intermediate Water (ESIW) characterized by a layer of shallow salinity minimum with a potential temperature range of 1-5 • C is widespread south of the subpolar front in a depth range of 100-500 m (Kim and Chung, 1984;.…”

Deep Nitrate Deficit Observed in the Highly Oxygenated East/Japan Sea and Its Possible Cause

“…The East/Japan Sea (EJS) is a marginal sea, with a maximum depth close to 4000 m, adjacent to the western North Pacific Ocean (Chang et al 2004). The EJS exhibits many open ocean-like features including deep-water formation processes (Talley et al 2006). Denitrification has not been considered to be a significant process sufficient to affect the nitrogen cycle in the EJS because the sea is well oxygenated throughout the water column (> 190 μmol kg -1 at minimum).…”