Intrusions of Kuroshio and Shelf Waters on Northern Slope of South China Sea in Summer 2015
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The northern slope region of the South China Sea (SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of commercially and ecologically important fish species. To understand the physical and biogeochemical processes that promote the high primary production of this region, we conducted a cruise from June 10 and July 2, 2015. In this study, we used fuzzy cluster analysis and optimum multiparameter analysis methods to analyze the hydrographic data collected during the cruise to determine the compositions of the upper 55-m water masses on the SCS northern slope and thereby elucidate the cross-slope transport of shelf water (SHW) and the intrusions of Kuroshio water (KW). We also analyzed the geostrophic currents derived from acoustic Doppler current profiler measurements and satellite data. The results reveal the surface waters on the northern slope of the SCS to be primarily composed of waters originating from South China Sea water (SCSW), KW, and SHW. The SCSW dominated a majority of the study region at percentages ranging between 60% and 100%. We found a strong cross-slope current with speeds greater than 50 cm s−1 to have carried SHW into and through the surveyed slope area, and KW to have intruded onto the slope via mesoscale eddies, thereby dominating the southwestern section of the study area.
Key wordsSouth China Sea shelf water Kuroshio water geostrophic currents cross-slope current
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This study is supported by the National Basic Research Program of China (No. 2014CB441500) and the National Natural Science Foundation of China (No. 41406021). The Argo data are provided by the China Argo Real-time Data Center (http://www.argo.org.cn/). The data of surface geostrophic currents and SSH are downloaded from AVISO, and the SST from the OSSIT. Meng Zhou would like to acknowledge the Captain of the RV Nanfeng for his knowledge and confidencem which kept us safe and effective during the cruise, and the ship crews for their tireless efforts to help us execute research tasks on the rough sea.
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