The role of Luzon Strait transport in shallow meridional overturning circulation of South China Sea
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Abstract: The impacts of the Luzon Strait transport on shallow meridional overturning circulation (SMOC) in the South China Sea (SCS) have been pointed out by previous studies, but the issue whether the Luzon Strait transport dominates the SMOC formation still remains open. The Helmholtz decomposition is applied based on OFES products to address this issue. Results show that the motion caused by the Luzon Strait transport is characterized as an obvious southward flow between 13°N and 20°N. After this motion being removed, the clockwise winter SMOC and the anticlockwise summer SMOC can still exist significantly. The SMOC existence and its seasonal variation are also reproduced in the numerical simulation with the Luzon Strait closed. Both results of the Helmholtz decomposition and numerical experiment suggest that the SMOC formation and its seasonal variation are not dominated by the Luzon Strait transport. The SCS monsoon is the primary driving factor for the SMOC, which is related to the physical processes within the SCS.
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Figure 1. Zonal velocities (m/s, eastward positive) at the eastern boundary of the SCS in winter (a) and summer (b).
Figure 2. Stream functions (106 m3/s) obtained by vertically integrating the total zonally integrated meridional velocity
$ V $ (a) and the rotational component$ {V}_{\Psi } $ (b) in winter. (c) and (d) are same as (a) and (b), but in summer.
Figure 3. The divergent component
$ {V}_{\Phi } $ (104 m2/s, northward positive) of total zonally integrated meridional velocity in winter (a) and summer (b).
Figure 4. Surface circulation (in m/s) in winter (a) and summer (b) from the control run. (c) and (d) are same as (a) and (b), but from OSCARv2.0 products.
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