The Agulhas Undercurrent Experiment

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0118318BealRecent observations of a strong, apparently persistent, Agulhas Undercurrent (AUC) raise a multitude of provocative questions. The big questions addressed by this study are What are the latitudinal extent of the AUC and its role in the thermohaline circulation?What are the evolution and forcing of the velocity, potential vorticity, and water mass structure along the AUC path?How does one quantify the mixing/entrainment with western boundary current waters and determine the absolute fluxes of heat and mass within the AUC?What are the mean and temporal variability of the transport of the AUC?A hydrographic cruise is proposed during which 4 conductivity-temperature-depth and lowered acoustic Doppler current profiler sections of the AUC will be measured. A short mooring array along 32S will be deployed, as well. Three moorings will each contain 3 meters spaced to capture the AUC transport. They will be confined to the lower 1000 m of the water column and be designed to monitor for up to 2 years, but may be retrieved earlier. The dominant fluctuations are expected to have periods of 30 - 40 days. The moorings, meters, and associated technicians will be provided at no cost to NSF by Southampton Oceanography Centre. A line of stations at 50 km spacing will connect the offshore ends of the sections closing boxes to allow property balance estimation to be done. A line of stations at 100 km spacing will be made along 1800 m from 26S to 37S to estimate the latitudinal extent of the undercurrent. Each station will include conductivity-temperature-depth, dissolved oxygen, and lowered acoustic Doppler current profiler data with 24 bottles for calibration to WOCE standards by ODF personnel. The cruise should require about 28 days.