Abstract:
The South China Sea throughflow (SCSTF) connects the South China Sea (SCS) with neighboring seas and
oceans, transferring surface water of the global thermohaline
circulation between the Pacific and Indian oceans. A configuration of the SYMPHONIE ocean model at high resolution (4 km) and including an explicit representation of tides
is implemented over this region, and a simulation is analyzed
over 2010–2018. Comparisons with in situ and satellite data
and other available simulations at coarser resolution show
the good performance of the model and the relevance of the
high resolution for reproducing the spatial and temporal variability of the characteristics of surface dynamics and water
masses over the SCS. The added value of an online computation of each term of the water, heat, and salt SCS budgets
(surface, lateral oceanic and river fluxes, and internal variations) is also quantitatively demonstrated: important discards
are obtained with offline computation, with relative biases of
∼ 40% for lateral oceanic inflows and outflows.
The SCS water volume budget, including the SCSTF, is
analyzed at climatological and seasonal scales. The SCS receives on average a 4.5 Sv yearly water volume input, mainly
from the Luzon Strait. It laterally releases this water to neighboring seas, mainly to the Sulu Sea through Mindoro Strait
(49 %), to the East China Sea via Taiwan Strait (28 %), and
to the Java Sea through Karimata Strait (22 %). The seasonal
variability of this water volume budget is driven by lateral interocean exchanges. Surface interocean exchanges, especially at Luzon Strait, are all driven by monsoon winds that
favor winter southwestward flows and summer northeastward surface flows. Exchanges through Luzon Strait deep
layers show a stable sandwiched structure with vertically alternating inflows and outflows. Last, differences in flux estimates induced by the use of a high-resolution model vs. a low-resolution model are quantified.