The Luzon Strait transport (LST) from the Pacific into the South China Sea (SCS) is examined using results from a high-resolution ocean general circulation model. The LST from the model has a mean value of 2.4 Sv (Sv ϵ 10 6 m 3 s Ϫ1) and reaches its seasonal maximum (6.1 Sv westward) in winter and seasonal minimum (0.9 Sv eastward) in summer. Both the annual mean and seasonal variation of LST compare favorably with earlier observations. On an interannual time scale, LST tends to be higher during El Niño years and lower during La Niña years, with its maximum (minimum) leading the mature phase of El Niño (La Niña) by 1 month. The interannual variation of LST appears to be oppositely phased with the Kuroshio transport east of Luzon, indicating a possible nonlinear hysteresis of the Kuroshio as a driving mechanism of LST. For the annual average, water leaving the SCS in the south is of higher temperature than that with LST, thus producing a cooling advection in the upper 405 m equivalent to a surface heat flux of Ϫ19 W m Ϫ2. Most of this cooling advection is balanced by the atmospheric heating (17 W m Ϫ2). From late spring to early fall, surface heat flux is the primary heating process; only a small part of the heat content change can be explained by heat advection. But, in winter, heat advection seems to be the only important process responsible for the cooling in the upper layer of the SCS. The interannual variation of the upper-layer heat content has a strong signature of ENSO, cooling in the development of El Niño and warming in the development of La Niña. An oceanic connection is revealed, in which LST seems to be a key process conveying the impact of the Pacific ENSO into the SCS.

No abstract

The South China Sea throughflow begins at the Luzon Strait, as an intrusion of the Kuroshio. At the present time, there are insufficient in situ measurements either to estimate accurately the transport loss or to provide a clear picture of the Kuroshio pathway at the Luzon Strait. In this study, we use newly available, multi‐year, high‐resolution satellite images and a numerical model to track the warm, relatively low‐biomass, Pacific water carried by the Kuroshio. A suite of numerical experiments are carried out to identify key factors that influence Kuroshio paths at the Luzon Strait. The model can reproduce the satellite‐inferred Kuroshio paths across the Luzon Strait only when a significant amount of the Kuroshio water is allowed to enter the Luzon Strait during December–February, therefore providing strong evidence for the existence of the South China Sea throughflow.

The salinity distribution in the South China Sea (SCS) has a pronounced subsurface maximum from 150–220 m throughout the year. This feature can only be maintained by the existence of a mean flow through the SCS, consisting of a net inflow of salty North Pacific tropical water through the Luzon Strait and outflow through the Mindoro, Karimata, and Taiwan Straits. Using an inverse modeling approach, the authors show that the magnitude and space–time variations of the SCS thermohaline structure, particularly for the salinity maximum, allow a quantitative estimate of the SCS throughflow and its distribution among the three outflow straits. Results from the inversion are compared with available observations and output from a 50-yr simulation of a highly resolved ocean general circulation model. The annual-mean Luzon Strait transport is found to be 2.4 ± 0.6 Sv (Sv ≡ 106 m3 s−1). This inflow is balanced by the outflows from the Karimata (0.3 ± 0.5 Sv), Mindoro (1.5 ± 0.4), and Taiwan (0.6 ± 0.5 Sv) Straits. Results of the inversion suggest that the Karimata transport tends to be overestimated in numerical models. The Mindoro Strait provides the only passage from the SCS deeper than 100 m, and half of the SCS throughflow (1.2 ± 0.3 Sv) exits the basin below 100 m in the Mindoro Strait, a result that is consistent with a climatological run of a 0.1° global ocean general circulation model.

Abstract. The objective of this study is to derive estimates of the mean seasonal variations in the Pacific to Indian Ocean throughflow transport using climatological data of the temperature/salinity fields and surface wind stress. A variable grid global general circulation model (GCM) with 1/6 ø resolution in Indonesian seas configured with ETOP05 bottom topography is utilized to diagnose the three-dimensional velocity field. An extensive set of sensitivity experiments is conducted to obtain estimates of the error bars. The computations show that Indonesian Throughflow (ITF) is maximum in boreal summer (13.9-+-1.3 Sv) and minimum in boreal winter