Modulation of cross-isothermal velocities with ENSO in the tropical Pacific cold tongue

The strength of the CT sets the zonal temperature gradient in the Pacific that couples with the atmospheric Walker circulation. This coupling is an essential component of the El Nino-Southern Oscillation (ENSO).

The CT is supplied with cold water by the Equatorial Undercurrent that follows the thermocline as it shoals toward the east, adiabatically transporting cold water toward the surface. As the thermocline shoals, its water is transformed through diabatic processes, producing water mass transformation (WMT) that allows water to cross mean isotherms. Here, we examine WMT in the cold-tongue region from a global high-resolution ocean simulation with saved budget terms that close its heat budget exactly.