Four newly--developed profiling floats (EM-APEX) measuring finescale temperature, salinity and velocity will be deployed in conjunction with a tracer release experiment in the Sargasso Sea in Summer 2005. The floats will alternate between profiling and isopycnal-following modes in order to characterize the internal wave environment in the vicinity of the tracer while minimizing their drift away from the center of the patch. Statistics of shear, strain and Richardson number over the duration of the tracer release will be directly compared to diapycnal diffusivities inferred from the dye, allowing testing and improvement of internal wave mixing parameterizations in the upper ocean. The floats will be deployed in a radial array across the chosen eddy so as to characterize the eddy structure and its evolution in time.
Intellectual Merit: While parameterizations for the diagnosis of diapycnal mixing using finescale shear and strain data have proven useful in the main thermocline, a number of failures have been documented in the upper ocean, in submarine canyons, and on continental shelves. To test the utility of such parameterizations in unraveling the question of nutrient supply to the euphotic zone, simultaneous diffusivity and finescale data will be required. The EM-APEX float is well suited for comparison with tracer-based diffusivity estimates because of its ability to drift with the flow at a chosen depth and measure temperature, salinity and velocity at scales down to a few meters.
Broader Impacts: These measurements will make a significant addition to the NSF-sponsored "EDdy Dynamics, mIxing, Export, and Species composition" (EDDIES) experiment by allowing a more complete in-situ description of the density and velocity fields in which the multi-disciplinary experiment is taking place. In addition, the EM-APEX float has the potential to be an immensely useful tool in future oceanographic studies. Demonstration of its capabilities in process studies such as EDDIES will help promote this new technology to the oceanographic community.
