Where do we measure?
Numerical and analytical model studies indicate that higher latitudes (32-35S) are the best location for a trans-basin MOC array for several reasons. First and foremost, higher latitudes provide larger dynamic range in the zonal density gradients, leading to improved signal-to-noise characteristics for geostrophic velocity calculations. Second, ocean model studies indicate that at higher latitudes it is possible to utilize less expensive mooring technologies, such as pressure equipped inverted echo-sounders (PIES), reducing the cost of the overall measurements. Third, measurement of the stability of the MOC, a function of the baroclinic salt flux, can best be measured at the southern boundary of the Atlantic, nominally along 34.5S. The community recommendation is that a SAMOC monitoring array be located at 32-35S, and that it involves about 20 deep ocean moorings, a combination of tall moorings and pressure-equipped inverted echo sounders, coupled with several shorter direct velocity moorings on the shelf on either side of the basin. Moorings have been funded and in some cases already deployed at 34.5S on the continental shelf and slope region of the eastern and western boundaries by SAMOC partners to assess South Atlantic boundary current transports and the role of Agulhas rings. Funds are being sought to augment the trans-basin array to better sample transports by the different deep water masses on the western boundary continental slope and rise and in the interior.