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Circulation, biogeochemistry and carbon cycling in ocean margins
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Variability of the Cyclonic-Anticyclonic-Cyclonic circulation in the South China Sea
P-M1-17-S
Yao Tang* , Division of Environment and Sustainability and Department of Mathematics, The Hong Kong University of Science and Technology
Jianping Gan, Department of Mathematics & Department of Ocean Science
The Hong Hong University of Science and Technology
Presenter Email: ytangba@connect.ust.hk |
| Recent studies have revealed that the three dimensional circulation in the South China Sea (SCS) exhibits a Cyclonic-Anticyclonic-Cyclonic (CAC) circulation pattern in the upper (<750 m), middle (750-1500 m) and deep (>1500 m) layer, which is driven mainly by the planetary vorticity influx from surrounding seas. This study investigates the spatiotemporal variability of the CAC intrinsic circulation in response to the influx in the SCS, which remains largely unknown. Based on the daily relative vorticity over 1992-2011 from the CMOMS (China Sea Multi-Scale Ocean Modeling System) model, we found that: (1) the intensity of the circulation and its variability in the upper and deep layer are much stronger than those of the middle layer; (2) positive relative vorticity at the northeast (hotspot1), western boundary (hotspot2) and SCS central basin (hotspot3) contribute to almost 90% of the upper cyclonic circulation. The hotspots 1 and 2 extend downward and account for over 70% of the whole anti-cyclonic circulation in the middle layer, while hotspot 1 continues to appear at the southwestern part of the deep basin; (3) the signal of seasonality dominates variability in upper layer, whereas the variability of middle and deep layers show not only seasonality (much weaker than that in upper layer), but also energetic intra-seasonal signal. All the three layers manifest inter-annual variability. Reasoning of these spatiotemporal variability will be presented. |
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