Spatial and temporal caracterization of the subtropic-tropic shallow cells in the Pacific and Atlantic oceans

Abstract

Tropic-subtropic cells (TSC) refer to meridional overturning shallow cells contained in the upper 500 m layer in the ocean as a result from the Ekman dynamics near the equatorial regions of the Atlantic and Pacific oceans. Waters from the upper layers in the tropical regions outcrop in response to the equatorial divergence and are carried toward the poles. When they arrive at the subtropics during the winter months, they loose heat and sink to the thermocline depths because of convective processes associated with interaction between ocean and atmosphere. Then, they are carried out by the subsurface layers up to the tropics where again arise, thus closing the cell. The sinking and upwelling time scale in these cells are relatively slow, ranging from interannual to decadal. Therefore, the TSC mechanism has a potential effect over the sea surface temperature (SST) fluctuations. Therefore, they can be considered as an important oceanic component in the variability of processes that occur at the interface between the ocean and the atmosphere. In the Pacific Ocean, the TSC pathways and its related transport variability have been extensively investigated by observational and theoretical studies. Unlike the Pacific, few observational studies of the TSC were conducted in the Atlantic, although various modeling studies have been published more recently. Therefore, this project aims to contribute to a better understanding of the similarities and differences in the structure of the cells in the Pacific and Atlantic oceans. We will also focus on determining the magnitude of the fluctuations on the time scales from interannual to decadal of the ocean variables related to TSCs. One of the objectives of this study is to analyze the changes in volume transport of the upper layers above the thermocline (or pycnocline) in the equatorial and tropical Atlantic and Pacific in interannual to intradecadal scale. We intend to verify the hypothesis that low frequency variations in the sea surface temperature (SST) observed in the subtropics are correlated with variations observed in tropical regions due to the dynamics associated with subtropical-tropical cells. (AU)