The Southern Ocean and its interactions with the atmosphere play an important role in the ocean and climate dynamics. The processes that govern the communication between the surface and the interior of the Southern Ocean ("ventilation") remain, however, poorly understood. A major challenge comes from the essential and complex role of mesoscale eddies. The spatial distribution of the eddy transports is complicated, and the effects of eddies are incredibly rich. The importance of this complexity has not been systematically evaluated.
The main goal of this project is to analyze the role of mesoscale eddies in ventilation of the upper waters (top 2000 meters) of the Southern Ocean. The importance of such properties of the eddy transports as large-scale spatial variations, anisotropy, transport barriers, advection by coherent vortices and non-diffusive effects will be investigated. The main hypothesis is that eddies and their properties listed above play an important role in ventilation of the Southern Ocean. To that effect, an analysis of how ventilation is directly affected by eddies, by studying the importance of eddies in the distribution of passive tracers (idealized and Chlorofluorocarbons) will be undertaken.
Specific objectives are to: (i) analyze distributions of the eddy flux divergences and eddy diffusivities, and study their relationship to other physical processes; (ii) examine the importance of eddies for ventilation of the major water masses of the upper Southern Ocean; (iii) identify specific properties of eddy transports, such as their anisotropic structure, that are the most important for the ventilation of the Southern Ocean. These objectives will be achieved using a suite of numerical experiments that are carefully designed to isolate the direct effects of eddies. In particular, the method of analyzing offline simulations with prescribed advective velocities with and without eddies will enable the investigators to isolate and analyze the effects of eddies on ventilation of the Southern Ocean.
Intellectual Merit: This project is addressing the fundamentally important problem of the role of eddies in ventilation the Southern Ocean. The proposed research is based on a technique that allows the investigators to most accurately isolate the direct effects of eddies on tracer distributions and ventilation. For the first time, the significance of these effects can be examined quantitatively. Main effects of eddies on distribution of idealized passive tracers and CFCs can be expected to be applicable to dynamically active tracers, such as density and potential vorticity. The progress in understanding the latter effects is notoriously challenging and will greatly benefit from the proposed analysis.
Broader Impacts: Understanding and quantifying the role of eddies in developing the mixing history of Southern Ocean waters has important implications for exchange and export of gases (Chlorofluorocarbons, Carbon Dioxide, Oxygen) and nutrients between the Southern Ocean and the rest of the global oceans. The identification of the most important eddy effects that require accurate representation in models will benefit the modeling community. Finally, this project will aid in the interpretation of observational data sets and in the planning of future observational strategies In terms of education and training, a post-doctoral fellow will advance his understanding of processes that govern ventilation of the oceans and redistribute transient oceanic tracers, and will learn various techniques of quantitative analysis of numerical simulations and their comparisons with data. One of the investigators is involved in several outreach activities for an under-represented group in science: women. She has served on the Mentoring Physical Oceanography Women to Increase Retention (MPOWIR) steering committee, participated in two Pattullo Conferences, and leads an MPOWIR mentoring group. She is also on the Steering Committee for the University of Miami's NSF-Advance program.
