Thermocline variability in the tropical Pacific

In the Pacific the thermocline exhibits three centers of variability, as indicated by temperature variance at 200m depth, one in the Kuroshio extension around 40^oN, the second between 10^oN and 15^oN, and the third around 10^oS. What is special about the tropical regions? These regions are located at the equatorward egdes of the subtropical gyres in both hemispheres, and are associated with large meridional gradients of mean thermocline depth. Thus, meridional displacements of the thermocline can give rise to large depth and temperature anomalies. These regions are also associated with enhanced Ekman pumping variability west of the dateline, which can produce large oceanic signals.

What is the nature of the thermocline variability in the tropics? Is the enhanced variance associated with a stronger surface forcing, or is the ocean responding more vigorously in these areas? Are there ocean-atmosphere feedbacks responsible for the enhanced variance around 13^oN and 10^oS in both oceanic and atmospheric fields? What are the dominant timescales of the ocean variability and what are the processes determining them?

We investigate these issues using a number of observational datasets, a global ocean general circulation model forced with observed atmospheric fields over the period 1958-1997, and an idealized Rossby wave model forced with different observed wind products as well as idealized wind forcing.