The oceanographical conditions of the Japan-Sea. III. On the relation between the oceanographical condition and the sea level. (In Japanese; Eng. abstr.)

1965 ◽  
Vol 12 (4) ◽  
pp. 638
Keyword(s):  
Author(s):  
Norihisa Usui ◽  
Koji Ogawa ◽  
Kei Sakamoto ◽  
Hiroyuki Tsujino ◽  
Goro Yamanaka ◽  
...  

Abstract Using a coastal assimilation model, generation mechanism of unusually high sea level (UHSL) at the south coast of Japan in September 2011 is investigated. Both model results and tide gauge observations indicate that sea level rise associated with the UHSL event occurred twice in the middle and end of September. The first one, which is localized around the eastern part of the Seto Inland Sea, is caused by a cyclonic circulation in the Kii Channel formed as a result of northward migration of the Kuroshio axis toward Cape Shionomisaki. The second sea level rise, which is the main contributor to this UHSL event, is observed in wide areas not only at the south coast of Japan, but also at the coast of the Japan Sea. It is brought about by a coastal trapped wave (CTW) induced as a result of a fluctuation of the Kuroshio path to the south of the Boso Peninsula. The CTW with positive SSH anomalies propagates westward along the south coast of Japan, and then goes into the coast of the Japan Sea. Sensitivity experiments and a modal characteristic analysis indicate that the CTW is mainly characterized by the first mode baroclinic Kelvin wave. The phase speed for the first mode is calculated at 2.96 m s$$^{-1}$$ - 1 , which compares well with that estimated by tide gauge observations.


2020 ◽  
Author(s):  
Xuefa Shi ◽  
Jianjun Zou ◽  
Sergey Gorbarenko

<p>The Japan Sea, one of the marginal seas of the North Pacific, communicates with adjacent seas through four shallow straits (<130 m) and the present environment in the Japan Sea is mainly forced by the Tsushima Warm Current (TWC), East Asia Monsoon (EAM) and seasonal sea ice. During the Quaternary, the pronounced effects of glacial eustatic sea level on the hydrography, ocean biogeochemistry and sediment depositions in the Japan Sea over glacial-interglacial cycles. However, the spatial heterogeneity of these forcings exerting on environment of the Japan Sea may results in contrasting response. On the basis of a suite of sediment cores collected during the China-Russia joint expedition in 2010, we investigate the sedimentary processes and paleoenvironment changes in the Japan Sea. We found enhanced extent of seasonal sea-ice coverage in the western Japan Sea, which is synchronous with the intensification of East Asian Winter Monsoon (EAWM) from 15ka to 8ka. During the early last deglaciation (17ka-15ka), perennial sea ice cover at investigated site occurs and thus inhibits the deepwater formation in the Japan Sea. Since 8 ka, increased deep ventilation and dampened sea ice coverage are closely related to enhanced EAWM and invasion of high-salinity TWC into the Japan Sea. In the southern Japan Sea, the sediment provenance is mainly derived from the Yangtze and old yellow rivers, while the terrigenous matter was mainly sourced from the Yangtze River after 7 ka, on the basis of elemental and radiogenic isotopic data (Sr and Nd) of fine-sized (<63 μm) sediments. Abrupt shifts in sediment provenance occurred at ~18 ka and ~7 ka and these time periods are synchronous with changes in surface hydrography and deep ventilation in the Ulleung Basin. In the central Japan Sea, eolian dust sourced from central Asia and Chinese Loess Plateau by westerly was delivered to the central Japan Sea. In addition, deep ventilation in the southern and central Japan Sea evidenced by redox-sensitive elements and ventilation-like radiolarian species suggest intensified ventilation since 8ka and during cold spells of the last deglaciation, which is closely related to the invasion of the Tsushima Warm Current into the Japan Sea. Our data suggest that sea level is a first-order factor in controlling the environment and sediment deposition in the Japan Sea at orbital timescales, while the East Asian Monsoon and Kuroshio Current play a secondary role. Note: This study was supported by the National Natural Science Foundation of China (Grants No. 41420104005, U1606401) and National Program on Global Change and Air-Sea Interaction (GASI-GEOGE-03 &-04).<span> </span></p>


1992 ◽  
Vol 37 (3) ◽  
pp. 346-360 ◽  
Author(s):  
L.D. Keigwin ◽  
S.A. Gorbarenko

AbstractThe Japan Sea was profoundly different during glacial times than today. Available δ18O evidence indicates that sea surface salinity was lower by several per mil. This probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea, as shown by the absence of benthic microfossils and the presence of laminated sediment. These changes are likely related to the effects of late Quaternary sea-level change on the shallow sills (ca. 130 m) across which the Japan Sea exchanges with the open ocean. The Hwang He (Yellow River) has previously been implicated as the source of fresh water to the Japan Sea during glaciation, but the possible roles of the Amur River and excess precipitation over evaporation must also be considered. Ambiguous radiocarbon chronologies for the latest Quaternary of Japan Sea cores do not adequately constrain the timing of salinity lowering. Previous studies have suggested that lowest sea surface salinity was achieved 27,000 to 20,000 14C yr B.P. However, if global sea-level fall restricted exchange with the open ocean circulation, then lowest salinity in the Japan Sea may have occurred as recently as 15,000 to 20,000 yr ago when sea level was lowest. If this alternative is correct, then as sea level abruptly rose about 12,000 yr ago, relatively fresh water must have been discharged to the open Pacific. This might have affected the dynamics of outflow, local faunal and floral expression of the polar front, and stable isotope ratios in foraminifera. These environmental changes could be misinterpreted as evidence for the cooling of Younger Dryas age, which has not been identified in nearby terrestrial records.


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