Collaborative Research: Moored Observations of Turbulent Kinetic Energy Dissipation In and Below the Mixed Layer During VOCALS

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Intellectual merit: One goal of the VOCALS (VAMOS Ocean Cloud Atmosphere Land Study; VAMOS is Variability of the American Monsoon System) Regional Experiment (REx) is to improve understanding of the processes controlling sea surface temperature (SST) in the Southeastern Pacific off the west coast of South America. A connected set of upper-ocean processes --- near-inertial internal waves, mesoscale eddies, and vertical mixing --- are hypothesized to be important influences on the regional SST field. The relationship of eddies and near-inertial waves to SST, surface forcing and upper-ocean dissipation are of broader interest, but coincident observations of these processes are rare and exist only over periods of a few weeks.This collaborative project will study the relationship of upper-ocean dissipation, near-inertial internal waves, and mesoscale eddies to SST in the VOCALS-REx study region over a period of one year. The project involves the enhancement of an existing, heavily instrumented air-sea interaction mooring with instruments to measure turbulent kinetic energy dissipation at six depths in the upper ocean and analysis of these observations in the context provided by the mooring record. The primary focus of the proposed research is on understanding how physical processes in the upper ocean impact SST in the VOCALS study region, but the results will be of broader scientific interest, as the observations will be unique and will allow insight into some outstanding scientific questions. Specifically, the following will be examined: (i) the relationship of velocity, hydrography, and turbulent dissipation within eddies in the VOCALS region; (ii) the temperature balance of the mixed layer; (iii) near-inertial kinetic energy balance in the mixed layer; and (iv) the influence of near-inertial oscillations on SST. Broader Impact: There are no time series of turbulent kinetic energy dissipation and its vertical profile in the surface mixed layer of the deep ocean spanning an annual cycle. Recent advances in instrumentation, battery longevity, and data storage capacity make such measurements possible now. The dissipation measurements, combined with the existing moored measurements of surface forcing and detailed profiles of stratification and velocity, will allow unprecedented study of the energy balance of mixed-layer near-inertial oscillations and the temperature balance of the mixed layer over a period of one year. A subject of great interest to those interested in the global ocean energy balance is the relative amount of wind-forced mixed-layer near-inertial kinetic energy that is dissipated locally compared to the amount of near-inertial energy that propagates to the deep-ocean. The episodic nature of wind-forced inertial oscillations makes a long-term study of their energetics desirable and necessary, and this will be the first such study that can directly address the relative contributions of wave radiation and mixed-layer dissipation to the loss of mixed-layer near-inertial kinetic energy from the mixed layer.This project also has a significant educational and outreach component. Presently at Columbia University and Barnard College, a number of course offerings expose students to principles of oceanography and applications of advanced environmental field methods. Focused teaching modules on global ocean-atmosphere interaction science problems will be developed to be incorporated into curricula. During the planned work, our experiments will offer unique opportunities for the Lamont-Doherty Earth Observatory?s Summer Intern Program in which talented undergraduates from around the world work on problems related to all aspects of environmental sciences. Results will be presented to the public through Lamont-Doherty Earth Observatory's annual open house.