The Annual Cycle of Meridional Heat Flux in the Atlantic Ocean at 26.5°N

Total meridional heat flux through a zonal oceanic section at 26.5°N in the Atlantic Ocean is computed from hydrographic, direct current and surface wind observations. The oceanic current and temperature fields are decomposed into depth-averaged and depth-dependent (including Ekman and geostrophic) components to perform the calculation. The mean annual boat flux is estimated to be 1.21 ± 0.34 PW. Mean monthly values of net heat flux are also computed from the data. The annual cycle of net heat flux determined from these values ranges from a minimum of 0.69 PW in February to a maximum of 1.86 PW in July. Thus, in contrast to an earlier estimate of the annual cycle of oceanic heat flux derived indirectly from surface energy fluxes and upper-layer heat content changes, there is no net southward heat flux during the Call. Results from a simulation of the circulation of the North Atlantic give an annual cycle of heat flux similar to our calculations with a summer maximum and winter minimum. However, the simulated mean value and range of the annual cycle are less than observed.