The volume transport of the cold deep water in the South China Sea
Date Issued
2009
Date
2009
Author(s)
Hsu, Wei-Lun
Abstract
Geographically, two deep channels which are both located around 121.5°E could lead deep water exchange (>2000 m) between Pacific Ocean and South China Sea (SCS). The north one, named as D1, is located east of southern Taiwan, while the south one, named as D2, is located east of Luzon Strait. The presented current observations indicate the deep water continuously flow into the SCS through D2. The volume transport through D2 was 1.08±0.32 Sv (1 Sv = 106 m3s-1), while the transport through D1 was negligible. By assuming volume conservation, the inflow transport was used to estimate the residence time and vertical velocity on the 2000m isobaths. The estimated residence time in the deep SCS (>2000m) is from 31 to 58 years. The estimated vertical velocity at 2000m is (1.10±0.32)×10-6 ms-1. It is close to the sum of the mean Ekman pumping (1.30×10-6 ms-1) and the mean geostrophic vertical velocities (0.30×10-6 ms-1) which were calculated by using Quick Scatterometer (QSCAT) wind and Generalized Digital Environmental Model (GDEM), respectively. The result indicates the deep current at D2 could be a primary channel providing the cold water into SCS. Examined the historical hydrography around SCS, the origination of SCS deep water could be mainly mixed by the water mass of Circumpolar Deep Water (CDW) and the water mass of Pacific Subarctic Intermediate Water (PSIW). Heat flux through D2 channel was also calculated. It could be balanced for 40% of net heat flux on sea surface. The result was implied that the upwelling at deep SCS as well as intermediated depths could be important for maintaining strong stratification and energetic internal motion in the SCS.
Subjects
South China Sea
deep water
volume transport
residence time
water mass
heat flux
upwelling
Type
thesis
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