Collaborative Research: Cold Tongue Mixing

Oregon State University, Corvallis OR

Investigators

Abstract

This project will examine temporal and spatial variability of diapycnal mixing of heat within the oceanic cold tongues of the Atlantic and Pacific oceans through multi-year time series measurements of dissipation of temperature variance, and through post-analysis of high temporal and spatial resolution ocean models. Temperature variance dissipation is measured using ChiPods, instruments developed by PI's lab at OSU that make high-frequency turbulence measurements to derive key parameters of ocean mixing. The Chipods will be deployed on moorings in the equatorial Pacific and Atlantic oceans where they will make continuous measurements of turbulence over four years. The project includes two early career scientists and educational components at the undergraduate student level. The cold tongues of the equatorial Atlantic and Pacific Oceans stand out as regions of cool tropical sea surface temperatures that take up anomalously large amounts of heat. Shear-driven turbulence moves heat well below the mixed layer and away from the surface. The rate of diathermal heat transport is determined by mixing, which can be measured directly using ChiPods deployed on moorings. The proposed work focuses on resolving long-term mixing signals in the equatorial cold tongues. This will allow evaluation of the role of mixing in interannual to decadal-scale processes, help determine the extent to which mixing influenced the Pacific cold tongue’s heat uptake during the warming hiatus, quantify how much heat is fluxed down to the deeper ocean, and quantify related model biases. ChiPods will be deployed at three equatorial mooring sites, two in the Atlantic and one in the Pacific. Analyses will be aimed at better understand intermittency of turbulence and its effect on seasonal, interannual and longer-term variations in vertical turbulent heat flux, particularly associated with tropical instability waves. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.