Intellectual Merit: The generation, propagation and upper-ocean mixing associated with near inertial internal waves will be conducted using data collected during the Eastern Pacific Investigation of Climate(EPIC2001) intensive field survey. This work will advance our understanding of near-inertial wave generation, propagation and decay at low-latitudes-processes that are poorly understood though likely important in light of recent estimates of the contribution of near-inertial wave mixing to the global mixing budget. Maps of wind-flux into mixed-layer inertial motions also indicate that the Eastern pacific Warm Pool (EPWP) may be a hotspot for low-latitude inertial wave generation. Preliminary findings suggest that near-inertial wave-produced mixing may influence entrainment at the base of the mixed-layer and the structure and evolution of the region's shallow thermocline. Both time series and spatial data from the EPIC2001 survey show that shear and turbulence within the thermocline were dominated by a single, energetic, downward-propagating near-inertial internal wave. The richness of the EPIC2001 data set, with temporal and spatial sampling of the upper ocean and lower atmosphere from a number of platforms, presents the unique opportunity to conduct such an investigation. Previous studies of low-latitude near-inertial waves lacked spatial data to extend the propagation and generation details beyond rough estimation.
The main scientific objectives of the project are to: 1. Quantify and describe in time and space the near-inertial wave and mixing it produced at 10?N, 95?W. 2. Determine the influence of the wave on mixed-layer properties. 3. Estimate the wave's properties using linear wave theory. 4. Quantify the wave's energy flux and estimate losses to spreading and turbulent dissipation. 5. Use a simple mixed-layer slab model to investigate the temporal and spatial variability of wind forcing. 6. Use a wind-forced primitive equation numerical model to investigate the wave's generation and propagation. 7. Compare our results with those of past near-inertial wave research and linear near-inertial wave theory.
Broader Impacts: This research will be done in close interaction with other EPIC2001 investigators and contribute to the EPIC goal of better understanding atmosphere-ocean coupling in the EPWP and Intertropical Convergence Zone (ITCZ). The results will also provide a physical basis for improving parameterizations of mixed-layer turbulent fluxes in ocean models utilized for making predictions of mixed-layer depth and heat-content in a key climatic region. As part of the project, a graduate student will complete his Ph.D. training in interpreting oceanic turbulence data as part of the upper ocean response to atmospheric forcing using modern analysis and modeling tools.
