黑潮於呂宋海峽的入侵

Three Acoustic Doppler Current Profilers (ADCP) were deployed in the central
Luzon Strait to monitor current velocity. The duration of deployment varied with
location and spanned from 1997 to 1999. The observed current velocity indicated
that the Kuroshio consistently intruded into the South China Sea. The current
velocity demonstrated small annual variation, but large intraseasonal variation. The
change of monsoons, from northeast to southwest, did not cause noticeable variation
in current velocity.
The Miami Isopycnic Coordinate Ocean Model (MICOM) forced by the wind
data provided by the European Centre for Medium-Range Weather Forecasts
(ECMWF) was used to interpret the observed current velocity. Comparison between
the model output and observation validates the use of the model result in interpreting
annual and interannual current velocity variation in the Luzon Strait. The numerical
model result also shows that the Kuroshio consistently intruded into the South China
Sea, displaying a noticeable annual variation in the central Luzon Strait. The large
interannual variation masked the annual variation so that the annual variation was
difficult to observe. The interaction between the Kuroshio and the South China Sea
cyclonic flow caused the current velocity variation in the both the Luzon Strait and
the northern sector of the South China Sea. In summer, the Kuroshio intrudes as a
loop current intrusion and confines to the northern South China Sea. In winter, the
Kuroshio can intrude deeply into the South China Sea, besides intruding as loop
current intrusion in the northern South China Sea.
The annual transport variation across the Luzon Strait is primarily westward.
The eastward transport was found in summer during certain years when the Kuroshio
intrusion was weak. In spite of the fact that the Kuroshio intruded consistently into
the South China Sea, transport out of the South China Sea was observed. In summer,
the current on the northern South China Sea shelf break contributed to the transport
out. The variation in zonal transport was caused by the Sea Surface Height (SSH)
variation occurring west of northern Luzon. Wind stress curl is responsible for this
SSH variation. The variation of Kuroshio strength had little impact on the intrusion.