Heat transport into a northern North Pacific (NNP) box, enclosed by thehigh resolution XBT (HRX) lines PX-37 (San Francisco-Honolulu), PX-40(Honolulu-Japan), and the Tsushima and Bering Straits, and heat transportinto a western North Pacific (WNP) box enclosed by the HRX lines PX-40,PX-10 (Honolulu-Guam) and PX-44 (Guam-Hong Kong or Taiwan), and theTsushima Strait, are estimated to be 0.31 ± 0.10 and 0.20 ± 0.21 PW,respectively.
The area integrals of climatological air-sea flux (average flux during1950-2001) from the NCEP/NCAR reanalysis are in agreement with ocean heattransports in both boxes. For the period of the XBT observations,1998-2001, the average flux from NCEP/NCAR falls within the error range ofheat transport in the NNP box, but is greater than the heat transport inthe WNP box (more heat loss from the ocean to the atmosphere).
Observational air-sea flux processed from COADS by the SouthamptonOceanographic Centre is underestimated compared to ocean heat transport.Adjusted flux by da Silva et al. (1994), which avoids the excessive heatingof the ocean, shows agreement with heat transport in the WNP box, but isoverestimated in the NNP box. Adjustments to air-sea flux products areneeded, but should be made locally rather than globally. It is expectedthat heat transport estimated from HRX sampling, which includes interannualvariations, can provide valuable constraints for the flux adjustment.
Seasonal heat budgets in both boxes are examined using the NCEP/NCAR fluxand heat storage data processed by White (1995). In the NNP box, thebalance between temporal change of heat storage and surface flux isdominant, and heat transport (advection) has little effect. On the otherhand, heat transport has a significant contribution to heat budget in theWNP box, acting to cancel part of the seasonal change of surface flux.Using only heat storage and flux data would mislead us into concluding thatheat transport has a smaller contribution. However, the time-series on line PX-40 is still short and an extended period of observations is needed for accurate estimates of seasonal and interannual variability.Continuation of the HRX sampling is required to clarify the mechanismsof ocean heat transport, its role in the ocean heat budget, and its long-term variability, which is believed to play a key role in decadal tointerdecadal climate variability in the North Pacific. |
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