National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2005

Shallow overturning circulations of the tropical-subtropical oceans

Schott, F.A., J.P. McCreary, and G.C. Johnson

In Earth Climate: The Ocean-Atmosphere Interaction, C. Wang, S.-P. Xie, and J.A. Carton (eds.), Geophysical Monograph 147, American Geophysical Union, Washington D.C., 261–304, doi: 10.1029/147GM15 (2004)

The Subtropical Cells (STCs) of the Pacific and Atlantic Oceans connect the subtropical subduction regions of both hemispheres to the eastern, equatorial upwelling regimes by equatorward thermocline and poleward surface flows. In the Indian Ocean, where equatorial upwelling is absent, a cross-equatorial cell (CEC) connects the southern-hemisphere subduction regime with upwelling regions north of the equator, and it is closed by southward, cross-equatorial Ekman/Sverdrup transport at the ocean surface. We review here the theory explaining the mean features of the STCs and CEC, the observational evidence for their various branches, and results of realistic model simulations. A topic of particular interest is the partition of the equatorward STC branch between interior and western-boundary pathways. Observational results are only now beginning to reveal the structure of the interior pathways, and model results of these flows vary with model type and the wind forcing applied. We also review studies of STC variability, which has been hypothesized to play a role in climate variability. Existing work indicates that wind-driven STC transport variations ( processes) are more important than advection of subducted temperature anomalies by the mean STC currents (the processes) in generating equatorial sea-surface temperature anomalies and, hence, climate variability.

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