New insights into the ocean heat budget closure problem from analysis of the SOC air-sea flux climatology

Results from an analysis of the Southampton Oceanography Centre (SOC) globa l air-sea heat flux climatology, which has been calculated using in situ we ather reports from voluntary observing ships covering the period 1980-93, a re presented. Systematic errors in the fluxes arising from differences in o bserving procedure have been quantified and corrected; the magnitude of the se errors is up to 15 W m(-2) with strong seasonal and regional variations. Despite these corrections, closure of the ocean heat budget is not obtaine d as the global mean net heat flux is an oceanic gain of 30 W m(-3). The va lidity of closing the heat budget by global scaling of the flux components is assessed by comparison of the SOC Aux fields with Woods Hole Oceanograph ic Institute research buoy measurements. The level of agreement between the two is found to vary from one site to another. Thus, closure of the ocean heat budget requires regional adjustments to the flux components in order t o avoid significant biases in the adjusted fields. Close agreement is found for several buoys deployed in the Subduction Array off the coast of northw est Africa. However, at other buoy deployment sites in the western equatori al Pacific warm pool and south of Bermuda in the North Atlantic, the flux a djustment improves the estimate of the net heat exchange. Further evidence for regional biases is obtained from a comparison of box mean surface heat fluxes derived from hydrographic section data with the corresponding SOC va lues in the Atlantic and North Pacific. The climatological heat loss is fou nd to be an underestimate in those boxes containing the strongest surface f lux expression of the major western boundary currents.