[A-CG31] Nutrient footprint of primary production in the coastal and marginal seas of East and Southeast Asia

[ACG31-P04] Analysis of oxygen-depleted water in the mid-outer shelf of the East China Sea based on the World Ocean Database

*ZILIN LI¹, Xinyu Guo¹ (1.Center for Marine Environmental Studies, Ehime University)

Keywords:oxygen-depleted, East China Sea, mid-outer shelf

Based on the World Ocean Database, we analyzed the spatiotemporal patterns of different oxygen-depleted conditions in the East China Sea shelf and compared the minimum value of dissolved oxygen and its change rate. In terms of seasons, oxygen-depleted water occurs in summer and autumn, with great differences in location and severity. In summer, hypoxia mainly occurs in the inner shelf. In autumn, oxygen deficiency mainly occurs in the middle shelf, and the oxygen-depleted water volume is much larger over the middle shelf than over the inner shelf. In addition, oxygen deficiency and low oxygen conditions are also found on the outer shelf in summer and autumn. From the average oxygen consumption point of view, in the four seasons, the outer shelf is greater than the middle shelf and the inner shelf. Interannually, the minimum values of dissolved oxygen in the inner, middle, and outer shelves show a decreasing trend. The low oxygen phenomenon has appeared on the outer shelf since the autumn of the 1950s. From the 1950s to the 1990s, the range and degree of oxygen consumption on the shelf increased. As we report in this study, the large oxygen-depleted water also occurs in the mid-outer shelf in autumn, which appears to have a different character and driving mechanism as compared to the summer inner shelf hypoxia observed by previous studies.