Td. Qu et al., UPPER OCEAN DYNAMICS AND ITS ROLE IN MAINTAINING THE ANNUAL MEAN WESTERN PACIFIC WARM POOL IN A GLOBAL GCM, International journal of climatology, 17(7), 1997, pp. 711-724
This study provides a description of the large-scale aspects of upper
ocean dynamics and its role in balancing the annual mean surface heat
budget in the tropical western Pacific Ocean, using the results from a
n ocean general circulation model (GCM) combined with existing observa
tions. A comparison with observations shows that the model simulates m
ajor aspects of the observed upper-layer thermal structure and circula
tion, and it has a reasonable representation of net surface heat flux.
The heat flux in the model is of the order of 10 W m(-2) into the oce
an near the Equator and less at high latitudes, which supports the pre
vious inference that fluxes in the region are overestimated in most cl
imatologies. The annual mean surface heat budget of the model averaged
over a large region (20 degrees S-20 degrees N and 110 degrees E-160
degrees E) indicates that heat is generally transported downward to th
e deeper levels by vertical motion and mixing, which agrees with earli
er studies. However, close inspection of six subregions within the lar
ge region indicates that different mechanisms are balancing the surfac
e heat budget in different subregions. Horizontal advection is importa
nt in some subregions. Upper-layer convergence induced by the equatorw
ard western boundary currents in the region of the North Equatorial Co
untercurrent (NECC) is equivalent to a surface heat flux of 17 W m(-2)
into the ocean, about 5 W m(-2) larger than the net exchange of heat
between ocean and atmosphere in the model. This provides a reasonable
explanation for why the warmest (> 28 degrees C) water of the global o
ceans exists in the tropical western Pacific and an independent eviden
ce for Wyrtki's hypothesis of accumulation of heat in the region. The
residence time of the warm pool water is about 8 months in the model s
horter by a factor of about two than Wyrtki's estimate of 1.3 years. (
C) 1997 by the Royal Meteorological Society.