Intellectual Merit: This project will analyze observations collected during the field phase of the Vema Fracture Zone Exploratory (VEX) Measurement program carried out in 2001-2003. The Vema Fracture Zone (VFZ) is an abyssal passage through the Mid-Atlantic Ridge near 11 degrees N, connecting the Guiana and Gambia Basins and permitting eastward flow of Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW). The VEX measurements were directed towards determination of the intensity and structure of the flow in the VFZ, the source pathways delivering waters to the VFZ, and the strength of the vertical mixing within the fracture zone. In the field phase of the project, 95 hydrographic stations were sampled and six moorings with a total of 18 current meters and three moored profilers were deployed.
The completed analysis and synthesis of the VEX data will provide a greatly improved picture of the abyssal flow through a low-latitude fracture zone linking two of the North Atlantic abyssal basins. This will advance our understanding of the deep component of the meridional overturning circulation, particularly through the recognition that much of the total diapycnal flow occurs in the restricted areas of fracture zones and steep topography. The description of the VFZ flow will also aid in validating the representation of flow through narrow passages in large-scale numerical simulations.
Broader Impacts: The moored profilers deployed during VEX for the first time outside their test and developmental phase, are novel instruments profiling current velocities, temperature, salinity, and pressure. Demonstrating the utility of simultaneous time series of velocity and CTD profiles for improved estimation of transports and mixing will benefit future moored profiler deployments. The analysis of the VEX data forms one component of the joint GAGE/VEX program. The funds requested will provide the opportunity for a young scientist to advance her skills in analyzing oceanographic processes using data from a variety of instrument sources.
