An investigation of natural climate variability, sensitivity, and poleward flux using the COADS data set

Upwelling-diffusion climate models have shown that radiative forcing changes in the ocean surface temperature penetrate only very slowly into the intermediate ocean whereas changes in deep water formation and basin scale upwelling can affect the water temperatures at intermediate depths sizably and quickly. Hence, both mechanisms could be involved in the warming of oceans at intermediate depths that has been observed. Seeing how the heat flux at the ocean-air interface has varied through time would give us an idea of the degree to which it accounts for the rise in intermediate water temperatures and hence the lack of a marked greenhouse warming signal in the temperature record.;To achieve these goals, the heat flux at the ocean-air interface was calculated for the 1946-1991 period using the Comprehensive Ocean Atmosphere Data Set (COADS). The heat flux was broken down into the four components of shortwave flux, longwave flux, latent, and sensible heat and individual components were calculated by the bulk parameterization method.;The magnitudes of the individual heat flux calculations were found to depend critically on the parameterization scheme adopted. There was however no difference in the temporal variation or spatial pattern of the individual flux components due to the parameterization scheme adopted. The net heat flux values, in turn, depended on the choice of parameterization schemes and therefore have a high uncertainty in comparison to the greenhouse radiative forcing signal that is expected to be hiding in the ocean.;There seems to have been a period of high heat flux into the ocean that was tapering off at the beginning of the record being analyzed. From the early 1960s the net heat flux seems to have increased till about 1980 and resumed its decreasing trend since then. One of the three net flux calculations carried out seems to be close to a zero global average for much of the period being analyzed, and therefore, likely to be the real scenario.;This study also looks at the overall poleward heat transport in the oceans as well as in individual ocean basins and their variation over the years.;The poleward heat flux calculations show that the Pacific Ocean shows higher magnitudes in the mid latitudes compared to the Atlantic and Indian Oceans. There seems to be a signficant variation in the poleward heat transport in the individual ocean basins over the years with an apparent shift occurring around 1980. (Abstract shortened by UMI.).