The East Sea (Japan Sea) in Change: A Story of Dissolved Oxygen

Dissolved oxygen (DO) is one of the most important oceanographic parameters measured for understanding various physicochemical processes in the ocean. This situation has been particularly true for the East Sea study ever since the first extensive investigation in the area during the 1930s (<xref ref-type="bibr" rid="bib23">Uda, 1934</xref>). Uda found very high and uniform concentrations of DO, around 250 µM (5.6 ml/l), for waters below a few hundred meters over entire basins, and assumed that a very fast ventilation system was operating in the East Sea. The Circulation Research of the East Asian Marginal Seas (CREAMS), Japan-Korea-Russia international cooperative studies on the East Sea have provided a unique opportunity to investigate the entire East Sea for the first time since Uda’s study. A spectrophotometrically modified Winkler method (<xref ref-type="bibr" rid="bib16">Pai et al., 1993</xref>) and a DO sensor (Sea Bird Model SBE 13) were tested successfully during the CREAMS studies for improving the precision and accuracy of DO measurement. The study further confirmed an earlier observation by <xref ref-type="bibr" rid="bib7">Gamo et al. (1986)</xref> that DO structures in the East Sea have been changing drastically in such a way that the DO minimum depths have deepened by more than 1000 meters during the last 30 years. While the causes for these changes are not known at the present time, the analysis of DO profiles strongly suggests that the mode of deep water ventilation system in the East Sea has shifted from bottom water formation in the past to intermediate water formation at the present time (<xref ref-type="bibr" rid="bib8">Kim and Kim, 1996</xref>). Studies of precise and accurate DO monitoring, along with other chemical tracers, deserve the highest priority for future research in the East Sea.

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Decadal Changes in Meridional Overturning Circulation in the East Sea (Sea of Japan)

Journal of Physical Oceanography ◽

10.1175/jpo-d-19-0248.1 ◽

2020 ◽

Vol 50 (6) ◽

pp. 1773-1791 ◽

Cited By ~ 1

Author(s):

MyeongHee Han ◽

Yang-Ki Cho ◽

Hyoun-Woo Kang ◽

SungHyun Nam

Keyword(s):

Sea Of Japan ◽

Bottom Water ◽

Meridional Overturning Circulation ◽

East Sea ◽

Intermediate Water ◽

Decadal Change ◽

Marginal Seas ◽

Water Formation ◽

Meridional Overturning ◽

Bottom Water Formation

AbstractMeridional overturning circulation (MOC) is vital to distributing heat, freshwater, and dissolved matter in semienclosed deep marginal seas such as the East Sea (ES) (Sea of Japan). As our understanding of the ES MOC remains incomplete, we attempted to fill this research gap. We analyzed the ES MOC and its decadal change (1993–2012), employing Hybrid Coordinate Ocean Model (HYCOM) global reanalysis. We found that the ES MOC, consisting of two counterrotating overturning cells in the late 1990s, changed into a single full-depth cell in the 2000s and reverted to two cells in the 2010s. The decadal change relates to weakening of the southward western boundary current at the intermediate layer and northward eastern boundary currents at the deep abyssal layer. We propose that surface warming and salinification favored reduced intermediate water formation and enhanced bottom water formation in the northwestern ES in the 2000s and were, therefore, key to the decadal change. Conditions unfavorable to intermediate water formation and favorable to bottom water formation in the winters of the 2000s, compared with the late 1990s, enhanced northward (westward) Ekman transport in the southern (northeastern) ES, successive advection of surface warm, saline water into water formation areas, and air–sea heat and freshwater exchanges linked to the January Arctic Oscillation. Our results indicated that the ES MOC is sensitive to both external atmospheric forcing and internal ES processes, which have implications for significant changes in the response of other marginal seas and global oceans to future climate variability.

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Occurrence and Evolution of Mesoscale Thermodynamic Phenomena in the Northern Part of the East Sea (Japan Sea) Derived from Satellite Altimeter Data

Remote Sensing ◽

10.3390/rs13061071 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1071

Author(s):

Taekyun Kim ◽

Hyeong-Jun Jo ◽

Jae-Hong Moon

Keyword(s):

Japan Sea ◽

Reanalysis Data ◽

East Sea ◽

Spatiotemporal Variability ◽

Altimeter Data ◽

Intermediate Water ◽

Dipole Structure ◽

Northwestern Region ◽

New Perspective ◽

Monsoon Winds

Based on satellite measurements and oceanic reanalysis data, it has been possible to investigate the spatiotemporal variability of the mesoscale phenomena in the northern part of the East Sea (NES) where direct observations of currents and hydrographical conditions are scarce. For the first time, this study identifies the detailed spatiotemporal structure of the mesoscale features in the NES and the mechanism of its occurrence and evolution, which have important consequences on the distribution of the intermediate water masses in the East Sea. Here, we show that mesoscale thermodynamic phenomena in the northwestern region of the East Sea are characterized by a dipole structure associated with positive and negative sea surface height anomalies. These result in a strong thermal gradient between the seasonally non-persistent anomalies, which emerge and strengthen during late fall and early winter. In contrast to the previous finding of the relationship between winter monsoon winds and mesoscale features in the NES, we found that this relationship is crucial only to the emergence of the mesoscale phenomena. Consequently, we present a new perspective on the evolution mechanism of the mesoscale features in the NES. Of direct significance to the present study, thermohaline transport into the northwestern region of the East Sea regulates the strengthening and weakening of mesoscale features in the NES. Wind forcing may contribute to the emergence of the mesoscale features in the NES and then the intensification of the mesoscale activities is attributed to the intrusion of warm and fresh surface water advected from the southern part of the East Sea.

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Air-sea interaction processes over the east-asian marginal seas surrounding the Korean peninsula

Annales Geophysicae ◽

10.5194/angeo-25-1477-2007 ◽

2007 ◽

Vol 25 (7) ◽

pp. 1477-1486 ◽

Cited By ~ 5

Author(s):

D. Bala Subrahamanyam ◽

Radhika Ramachandran ◽

S. Indira Rani ◽

B. Prasad Kumar

Keyword(s):

Heat Flux ◽

Korean Peninsula ◽

East Asian ◽

Sensible Heat Flux ◽

Japan Sea ◽

The Yellow Sea ◽

Climatological Data ◽

Marginal Seas ◽

East Asian Marginal Seas ◽

Meteorological Observations

Abstract. In this article, we describe the seasonal variation of air-sea interface fluxes of heat, momentum and moisture over the East Asian Marginal Seas (EAMS) surrounding the Korean Peninsula. Surface layer meteorological observations for a period of about six years obtained from five oceanic buoys deployed in the Yellow Sea, Korean Strait and East (Japan) Sea form the database for this study. With the available database, monthly mean of sensible heat flux, latent heat flux and momentum flux obtained from the present analysis is compared with the existing climatological data over the EAMS.

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Re-initiation of bottom water formation in the East Sea (Japan Sea) in a warming world

Scientific Reports ◽

10.1038/s41598-018-19952-4 ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 7

Author(s):

Seung-Tae Yoon ◽

Kyung-Il Chang ◽

SungHyun Nam ◽

TaeKeun Rho ◽

Dong-Jin Kang ◽

...

Keyword(s):

Bottom Water ◽

Japan Sea ◽

East Sea ◽

Water Formation ◽

Warming World ◽

Bottom Water Formation

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Intermediate Water Formation at the Japan/East Sea Subpolar Front

Oceanography ◽

10.5670/oceanog.2006.48 ◽

2006 ◽

Vol 19 (3) ◽

pp. 110-121 ◽

Cited By ~ 22

Author(s):

Craig Lee ◽

Leif Thomas ◽

Yutaka Yoshikawa

Keyword(s):

East Sea ◽

Intermediate Water ◽

Water Formation

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Continent-Ocean Interactions Within East Asian Marginal Seas

10.1029/gm149 ◽

2004 ◽

Cited By ~ 8

Keyword(s):

East Asian ◽

Marginal Seas ◽

East Asian Marginal Seas

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Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current

The Holocene ◽

10.1177/09596836211003238 ◽

2021 ◽

pp. 095968362110032

Author(s):

Boo-Keun Khim ◽

Sunghan Kim ◽

Yu-Hyeon Park ◽

Jongmin Lee ◽

Sangbeom Ha ◽

...

Keyword(s):

Grain Size ◽

Japan Sea ◽

East Sea ◽

Eastern Coast ◽

Size Change ◽

Sediment Properties ◽

Warm Current ◽

The Holocene ◽

Mean Grain Size ◽

East Korea Warm Current

Various sediment properties, such as mean grain size, total organic carbon, total nitrogen, C/N ratio, CaCO3, and biogenic opal content, were analyzed for a box core (BC02; 45 cm long) and a gravity core (GC02; 628 cm long), which were collected from the western margin of the Hupo Trough located off the eastern coast of Korea. The study area has been affected by the East Korea Warm Current (EKWC), a branch of the Tsushima Warm Current (TWC). The analytical results obtained for BC02 and the upper part of GC02 were in agreement, affirming the core-top preservation of GC02. Based on the corrected calibrated AMS 14C dates, the sedimentation rate of GC02 changed abruptly at ~8.2 ka from ~4.0–10.2 cm/kyr in the lower part to ~56.6–91.0 cm/kyr in the middle to upper part. This corresponds to the lithologic change from sandy mud to mud sediments showing the mean grain size change from 6.9 to 46.0 μm. Diverse paleoceanographic proxies representing the surface water condition exhibited varying degree of change at ~8.2 ka, after which all the properties remain almost unchanged, implying stable and continuous depositional conditions following the complete development of the EKWC. Furthermore, it indicated that the sediment depositional conditions in the Hupo Trough in response to the EKWC might have stabilized at ~8.2 ka since the opening of the Korea Strait during the Holocene sea level rise. Moreover, microfossil data from previous studies on the establishment of the TWC in the East Sea (Japan Sea) support our interpretation that the sediment properties revealed the Holocene development of the EKWC in the Hupo Trough.

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