The ACT mooring array will be positioned offshore and to the southwest of East London, South Africa, in up to 4700 m of water. The array will consist of seven full-depth current meter moorings, spanning the mean width of the Agulhas Current, one tide gauge, plus four pressure gauge-equipped inverted echo-sounders (C-PIES) to cover the Current's offshore meandering events cost-effectively.
On each full-depth mooring upward-looking profiling current meters will measure the top 350 m of the water column, where velocities are strongest. Below these, up to six single-point current meters will measure the rest of the water column. All current meters are acoustic, with no moving parts, measuring velocity using the principle of Doppler shift, whereby the frequency of a sound wave changes as it reflects off a moving particle in the ocean.
Offshore recirculations and meandering events will be captured using the C-PIES, which can give information about the transport over the upper 2000 m, when combined with local hydrographic data collected during each mooring cruise. The shallow-water tide gauge will be placed on the continental shelf, allowing for an hourly record of sea surface height shoreward of the Agulhas Current.
The initial deployment cruise is scheduled to leave Cape Town, South Africa, in March 2010, aboard a U.S. University-National Oceanographic Laboratory System (UNOLS) research vessel. The ACT array will be in the water until approximately March 2013.
"Ultimately, a twenty year proxy of Agulhas Current transport will provide an important climate index for the Indian Ocean, which can be linked to other climate indices, such as the Atlantic Meridional Overturning, and hopefully improve our predictive capabilities for the future," Beal added.
|Contact: Barbra Gonzalez|
University of Miami Rosenstiel School of Marine & Atmospheric Science