Japan Geoscience Union Meeting 2022

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS22] Ocean circulation and material cycle in coastal seas

Wed. May 25, 2022 3:30 PM - 5:00 PM Exhibition Hall Special Setting (2) (Exhibition Hall 8, Makuhari Messe)

convener:Daisuke Takahashi(Tokai University), convener:Naoki Furuichi(Fisheries Technology Institute, Japan Fisheries Research and Education Agency ), Hitomi Yamaguchi(Kagawa University), convener:Akihiko Morimoto(Ehime University), Chairperson:Daisuke Takahashi(Tokai University), Naoki Furuichi(Fisheries Technology Institute, Japan Fisheries Research and Education Agency), Hitomi Yamaguchi(Kagawa University), Akihiko Morimoto(Ehime University)

3:30 PM - 3:45 PM

[AOS22-07] Horizontally localized existence of multi-decadal deoxygenation trend in East China Sea

*Tsuneo Ono1 (1.Fisheries Research and Education Agency)

Keywords:East China Sea, oxygen, temporal trends

In the last JpGU meeting I presented a significant trend of oxygen decrease in shallow subsurface waters (30m to 100m depth range) in summer Tsushima-strait area. Detailed analyses suggested that this deoxygenation trend originated not from the westward propagation of deep-water deoxygenation in Japan Sea, but from the eastward propagation of oxygen decrease in the East China Sea (Ono et al., 2021). To specify more localized origin of this phenomenon, I separated East China Sea into 29 sub-areas. Historical oxygen data observed from 1950s to 2000s in each sub-area were then extracted from WOD 2018, and interannual variation in each isodepths (0m, 10m, 30m, 50m, 75m and 100m) were examined in each sub-area. As this result, it was found that summer oxygen data (June to August) showed multi-decadal decreasing trend only in the sub-areas where their surface area are covered by Changjiang diluted water in summer season. Vertical gradient of both water temperature and salinity between 10m and 50m showed no significant temporal trends in these sub-areas, suggesting that the observed temporal decrease of sub-surface oxygen in these areas were caused not by temporal variation of vertical oxygen transport from surface waters but by enhanced oxygen consumption by biological processes.