Large-Scale Ocean Heat and Freshwater Transports during the World Ocean Circulation Experiment

Abstract

Hydrographic sections obtained during the World Ocean Circulation Experiment are combined using a geostrophic inverse model to estimate the global-scale horizontal transports and transport divergences of heat and freshwater with self-consistent error bars. The overall results are compared to bulk formula–derived climatologies and estimates derived from atmospheric reanalyses. At 7.5°N in the Atlantic, a previous estimate of the heat transport is modified. A recent atmospheric residual estimate from NCEP and the Earth Radiation Budget Experiment (ERBE) products is consistent with the present results for the heat budget, except at high northern latitudes where it falls outside error estimates. The freshwater transport divergence from hydrography is statistically significant only when integrated over very large areas and difficult to test—as extant climatological estimates differ substantially from each other. Hydrographic estimates can be improved through repeated observations to reduce the temporal aliasing, and by combining more detailed regional estimates using more data types. To permit a formal comparison and assimilation in ocean general circulation models, atmospheric estimates urgently require convincing error estimates for both heat and freshwater transports.