T. Kagimoto et T. Yamagata, SEASONAL TRANSPORT VARIATIONS OF THE KUROSHIO - AN OGCM SIMULATION, Journal of physical oceanography, 27(3), 1997, pp. 403-418
Numerical simulation is performed using a high-resolution ocean genera
l circulation model to investigate seasonal variations of the Kuroshio
transport. The simulated velocity profiles of the Kuroshio agree surp
risingly well with ADCP observations and dynamic calculations. The ann
ual mean of the model Kuroshio transport relative to 700 m across the
PN line near the Nansei (Ryukyu) Islands is about 25 Sv (Sv = 10(6) m(
3) s(-1)), which is almost the same with the estimate based on the lon
g-term hydrographic observations. The model transport variations acros
s the PN line are also almost the same as the observation; the transpo
rt shows a weak maximum in summer and a weak minimum in winter. Althou
gh the Sverdrup balance is valid in the broad interior of the basin, i
t fails to predict the variations as well as the transport of the Kuro
shio south of Japan due to existence of the Kuroshio recirculation. Th
e above discrepancy between the Sverdrup theory and the model (observa
tions, as well) is studied in detail by analyzing the torque balance.
In winter the Kuroshio transport across the PN line is much smaller th
an expected from the Sverdrup theory because the topographic control p
revents the western boundary current from intruding west of the contin
ental slope near the Nansei Islands. The current over the slope legion
changes its direction from winter to summer due to anticyclonic eddy
activity related to the joint effect of baroclinicity and bottom topog
raphy. The deep northeastward current over the slope in winter is canc
eled in summer by the eddy activity so that the interaction between th
e continental slope and the current is much reduced. Since the same ed
dy activity intensifies the Kuroshio recirculation, the Kuroshio trans
port across the PN line in the East China Sea is increased in summer.
The present study demonstrates that comparing model results with obser
vations requires a model resolution suitable enough to resolve locatio
ns of observations as well as essential dynamics related to the intera
ction between baroclinic ocean currents and bottom topography.