This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Intellectual Merit: The momentum and energy fluxes from the atmosphere to the ocean pass through the surface wave field before giving rise to surface currents and mixing locally, while some of the fluxes extend across the ocean basins through propagation by swell. However, the detailed balances of energy and momentum in the upper ocean are poorly understood and are still the subject of speculative estimates. Recent Large Eddy Simulations (LES) of the upper ocean mixed layer, or Oceanic Boundary Layer (OBL), which include wave effects through Langmuir circulations and wave breaking, have shown that wave effects may be felt throughout the developing boundary layer through aspects of vortex dynamics common to both breaking and Langmuir circulations, and synergies between the two phenomena. For example, the numerical model shows that the same Craik-Leibovich vortex force and feedback that gives rise to Langmuir circulations may be seeded by breaking. Furthermore, turbulence generated at the surface by breaking may be transported into the entraining boundary layer by Langmuir circulations.
The project will carry out a series of field experiments to test the assumptions and predictions of the LES models. The field measurements will be conducted from R/P FLIP in collaboration with planned ONR FLIP experiments on surface wave phenomena and air-sea interaction. These wave measurements are necessary to constrain the LES models and boundary conditions. The project will concentrate on the OBL measurements including currents and turbulence, temperature, salinity and entrained air (bubbles), from profiled instruments and a tethered surface float. The predictions of the models may be tested by measurements of the statistical moments of the velocity and temperature fields as a function of depth, including fluxes of momentum, heat and Turbulent Kinetic Energy (TKE) through the OBL. One of the important assumptions of the models is that the dynamical effects of the entrained air due to breaking can be neglected; a good approximation under certain environmental conditions. However, there is evidence that this approximation will break down near the surface at higher wind speeds. If air entrainment is dynamically significant it will act to suppress vertical mixing and may have a qualitative impact on the structure of the OBL. Direct measurements of the air entrained by breaking and its dynamical consequences will be made.
Broader Impacts: This research will include an improved understanding of the coupling of the oceans and the atmosphere, leading to better coupled models of weather and climate. Our ability to predict seasonal fluctuations and secular climate change has an important impact on fisheries, agriculture, the energy industry, the commodity markets, the construction and insurance industries, and disaster/threat preparedness. Ultimately, good national and international environmental policy relies on a solid scientific basis for decision making, and the project will contribute to those policies. The project will support the integration of research and education at every academic level. This includes training and support of post-doctoral scholars and graduate students, as well as contributions to K-12 and public education. Results from this research will be disseminated in professional journal publications and more popular avenues of publication. Knowledge gained through this research will be incorporated into the education and training of students at Scripps Institution of Oceanography, UCSD. The resources from the project will support a doctoral student and provide material and facilities for undergraduate projects and minority undergraduate summer fellows. The results of this project will be used to promote science and research to a broader audience by working with the Center for Ocean Science Excellence/California (COSEE CA) to develop a website and present earth science workshops for science teachers from the San Diego Unified School District.
