Measurements of meridional heat transport by ocean currents

The meridional transport of heat by ocean currents in the northern hemisphere, as calculated from heat-balance maps of the oceans compiled by Budyko and Albrecht, is compared with a similar calculation by Sverdrup. The transports are in best agreement in the northern part of the North Atlantic. Discrepancies occur in the Pacific and in the equatorial Atlantic. To calculate meridional heat transport directly, a method is formulated for combining hydrographic station data and climatological estimates of surface wind stress. The method is applied to hydrographic sections made by individual expeditions during the IGY and NORPAC programs. Transient changes in the density field introduce a large sampling error, but these measurements have the advantage of providing some physical insight into the mechanism of heat transport. The principal conclusions of the study are: (a) Circulations in the vertical plane account for at least half as much meridional heat transport as the large-scale horizontal circulation of ocean basins; (b) the NORPAC Pacific section made in August 1955 at 35°N indicates a transport of heat southward, toward the equator, comparable in magnitude to northward heat transport measured in the North Atlantic.