Wind-forced inertial oscillations of the surface mixed layer generate propagating near-inertial waves, which eventually break and drive small-scale mixing in the ocean interior. The importance of such small-scale mixing for the large-scale circulation is becoming increasingly apparent. However, based on the current range of estimates, the flux of energy from the mixed layer to propagating near-inertial waves may either play a major role in the ocean's power budget, comparable to the tidal input, or may be entirely negligible - a fundamental uncertainty.
This study uses data analyses, supplemented by numerical modeling, to assess the role of eddies in shaping the global character of mixed layer oscillations. The primary goal is a more accurate estimate of the global contribution of wind forcing to the near-inertial wave field. The strategy is built around accessing and interpreting the dynamical information contained in a recently enhanced dataset - the Global Drifter Program network of surface buoys, now available with approximately hourly resolution since 2005. The use of a new set of mathematical tools will capture the time-varying properties of inertial oscillations in the mixed layer, and simultaneously, those of the mesoscale eddies expected to modulate the inertial environment.
Intellectual Merit: This process-oriented study will be an important step in the larger goal of understanding and quantifying the mechanical energy budget of the ocean. It will have a direct benefit to the representation of the ocean's response to wind forcing in general circulation models, and consequently, to our ability to accurately predict climate-scale variability. Furthermore, the approach which brings together advances and expertise in data collection, analysis, and numerical process modeling will make optimal use of newly available resources and will identify outstanding areas for future research.
Broader Impacts: A primary societal benefit of this work is its potential impact on our ability to predict long-term climate variability. Funds are included to support a postdoctoral researcher, who will gain exposure to novel datasets, data analysis techniques, and numerical studies. The project will benefit other investigators by supporting and promoting the use of the high-resolution drifter dataset as a new window on ocean dynamics. Analysis algorithms developed in this work will be freely distributed to the greater scientific community, by inclusion in JLAB, J. M. Lilly's open-source software package for Matlab. The project will also fund two early career scientists.
