This project is a contribution the the AIMS (Analysis, Interpretation, Modeling, and Synthesis) phase of the World Ocean Circulation Experiment (WOCE). In the early part of WOCE, the Deep Basin Experiment (DBE) was begun in the tropical South Atlantic. A variety of observations were initiated by both US and French scientists, which included hydrographic surveys, mooring arrays, subsurface floats, and others. As part of the effort to synthesize DBE data, the PI proposes to continue analysis of velocity and temperature measurements from moored arrays at the equator along 36 degrees West and in the Romanche and Chain Fracture Zones (RFZ and CFZ). These arrays monitored the two exit passages for AntArctic Bottom Water (AABW) from the Brazil Basin. Estimates of mean AABW transport and its variability have already been published. This proposal addresses the transport in potential temperature classes at 36 degrees W, which will estimate the temperature / heat flux through the array. Advective-diffusive heat budgets over volumes bounded by isotherms will be used to obtain estimates of average vertical diffusivity in the AABW in the basins north and south of the equator, and the implications of slow changes observed in the bottom water will be studied, including the possibility of calculating time-dependent diffusive coefficients.
