Penetration of surface-forced diurnal cycles observed by enhanced TAO moorings across the tropical Pacific
We find a surprising diversity of diurnal cycles in upper ocean heat and velocity across the enhanced sites, ranging from cycles that penetrate as deep as 65 meters to those that are confined to the upper 10-15 meters. We explore possible controls on these penetration depths, including wind forcing, insolation, and background ocean dynamics like Kelvin and tropical instability waves. In general, we find that deeper penetration of surface-forced heat and velocity occurs in locations where there is strong insolation and strong subsurface background shear. This background shear creates a marginally unstable flow, so that additional shear associated with the near-surface afternoon warm layer can trigger deeply-penetrating diurnal mixing.