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

2020 ◽  
Vol 50 (6) ◽  
pp. 1773-1791 ◽  
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.

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

1999 ◽  
Vol 33 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Kyung-Ryul Kim ◽  
Kuh Kim ◽  
Dong-Jin Kang ◽  
Sun Young Park ◽  
Mi-Kyung Park ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Ventilation System ◽  
Japan Sea ◽  
East Sea ◽  
Future Research ◽  
Intermediate Water ◽  
Chemical Tracers ◽  
Marginal Seas ◽  
East Asian Marginal Seas ◽  
Water Formation

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.

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

2018 ◽  
Vol 8 (1) ◽  
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

Turnover Time of the East Sea (Sea of Japan) Meridional Overturning Circulation

2021 ◽  
Vol 8 ◽  
Author(s):  
MyeongHee Han ◽  
Yeon S. Chang ◽  
Hyoun-Woo Kang ◽  
Dong-Jin Kang ◽  
Yong Sun Kim
Keyword(s):  
Flow Pattern ◽  
Sea Of Japan ◽  
Turnover Time ◽  
Meridional Overturning Circulation ◽  
East Sea ◽  
Shallow Convection ◽  
Overturning Circulation ◽  
Water Particle ◽  
Chemical Tracers ◽  
Meridional Overturning

The East Sea (ES; Sea of Japan) meridional overturning circulation (MOC) serves as a crucial mechanism for the transportation of dissolved, colloidal, and suspended particulate matters, including pollutants, on the surface to deep waters via thermohaline circulation. Therefore, understanding the structure of the ES MOC is critical for characterizing its temporal and spatial distribution. Numerous studies have estimated these parameters indirectly using chemical tracers, severely limiting the accuracy of the results. In this study, we provide a method for directly estimating the turnover times of the ES MOC using the stream functions calculated from HYbrid Coordinate Ocean Model (HYCOM) reanalysis data by averaging the flow pattern in the meridional 2-D plane. Because the flow pattern is not consistent but various over time, three cases of stream function fields were computed over a 20-year period. The turnover time was estimated by calculating the time required for water particles to circulate along the streamlines. In the cases of multiple (two or three) convection cells, we considered all possible scenarios of the exchange of water particles between adjacent cells, so that they circulated over those cells until finally returning to the original position and completing the journey on the ES MOC. Three different cell cases were tested, and each case had different water particle exchange scenarios. The resulting turnover times were 17.91–58.59 years, 26.41–37.28 years, and 8.68–45.44 years for the mean, deep, and shallow convection cases, respectively. The maximum turnover time, namely 58.59 years, was obtained when circulating the water particle over all three cells, and it was approximately half of that estimated by the chemical tracers in previous studies (∼100 years). This underestimation arose because the streamlines and water particle movement were not calculated in the shallow (&lt;300 m) and deep areas (&gt;3,000 m) in this study. Regardless, the results of this study provide insight into the ES MOC dynamics and indicate that the traditional chemical turnover time represents only one of the various turnover scenarios that could exist in the ES.

Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies

2020 ◽  
Vol 13 (12) ◽  
pp. 780-786 ◽  
Author(s):  
Alessandro Silvano ◽  
Annie Foppert ◽  
Stephen R. Rintoul ◽  
Paul R. Holland ◽  
Takeshi Tamura ◽  
...  
Keyword(s):  
Bottom Water ◽  
Ross Sea ◽  
Antarctic Bottom Water ◽  
Climate Anomalies ◽  
Water Formation ◽  
Bottom Water Formation

scholarly journals Arctic–North Atlantic Interactions and Multidecadal Variability of the Meridional Overturning Circulation

2005 ◽  
Vol 18 (19) ◽  
pp. 4013-4031 ◽  
Author(s):  
Johann H. Jungclaus ◽  
Helmuth Haak ◽  
Mojib Latif ◽  
Uwe Mikolajewicz
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Deep Water Formation ◽  
Overturning Circulation ◽  
Multidecadal Variability ◽  
Water Formation ◽  
Meridional Overturning

Abstract Analyses of a 500-yr control integration with the non-flux-adjusted coupled atmosphere–sea ice–ocean model ECHAM5/Max-Planck-Institute Ocean Model (MPI-OM) show pronounced multidecadal fluctuations of the Atlantic overturning circulation and the associated meridional heat transport. The period of the oscillations is about 70–80 yr. The low-frequency variability of the meridional overturning circulation (MOC) contributes substantially to sea surface temperature and sea ice fluctuations in the North Atlantic. The strength of the overturning circulation is related to the convective activity in the deep-water formation regions, most notably the Labrador Sea, and the time-varying control on the freshwater export from the Arctic to the convection sites modulates the overturning circulation. The variability is sustained by an interplay between the storage and release of freshwater from the central Arctic and circulation changes in the Nordic Seas that are caused by variations in the Atlantic heat and salt transport. The relatively high resolution in the deep-water formation region and the Arctic Ocean suggests that a better representation of convective and frontal processes not only leads to an improvement in the mean state but also introduces new mechanisms determining multidecadal variability in large-scale ocean circulation.

scholarly journals Impact of Weddell Sea shelf progradation on Antarctic bottom water formation during the Miocene

2017 ◽  
Vol 32 (3) ◽  
pp. 304-317 ◽  
Author(s):  
Xiaoxia Huang ◽  
Michael Stärz ◽  
Karsten Gohl ◽  
Gregor Knorr ◽  
Gerrit Lohmann
Keyword(s):  
Bottom Water ◽  
Weddell Sea ◽  
Antarctic Bottom Water ◽  
Water Formation ◽  
Bottom Water Formation
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