Satellite Measures Provide Missing Data on
Transports through Ocean Straits
T. Qu (IPRC) and Y. T. Song (JPL), GRL 2009, Vol. 36.
Density
profiles on
the SCS side
and Sulu Sea
side of the
Mindoro
Strait
Mindoro interannual transport variation:
total (black), upper (red) and deeper
layer (blue)
The South China Sea Throughflow (SCSTF) impacts Southeast Asia’s climate. Direct measurement of water transports
through the various straits, though, is complicated by the region’s variable ocean bottom topography and circulation.
Our understanding of the transports through the main strait, the Mindoro Strait, has thus come mostly from numerical
models. Qu and Song have now developed a method that allows the transports to be estimated from GRACE remotelysensed sea surface height and ocean-bottom-pressure. Using this method, they provide the first “observational”
estimate of the interannual transport variation through Mindoro Strait. At the thermocline and subthermocline depths,
the Mindoro Strait is the only pathway through the South China Sea (SCS), the density difference between the SCS and
the Sulu Sea providing a persistent baroclinic pressure gradient that drives the deeper water through the Mindoro
Strait. Most of the shallower waters flow through the Karimata Strait. Application of the hydraulic theory combined with
the “geostrophic control” formula to the data yields an mean transport of 2.4 Sv, consistent with earlier studies.
This new method that uses continuous satellite measurements is ideal for setting up a reliable monitoring
system of the transports through the SCS and may also be applicable to monitoring flow through straits
throughout the global ocean.