Eddy Kinematics During the Agulhas-South Atlantic Thermohaline Transport Experiment (ASTTEX): Sea Level Variability Along the ASTTEX Mooring Line and Beyond

To better quantify exchanges of heat, salt and mass entering the South Atlantic Ocean via the Agulhas Retroflection, an array of moored pressure sensor-equipped inverted echo sounders (PIES) and near-bottom current meters (CM) was deployed off the coast of southern Africa as part of the Agulhas-South Atlantic Thermohaline Transport Experiment (ASTTEX). Satellite altimetry is analyzed as part of ASTTEX to provide the regional view that is not accessible from the mooring observations alone. By observing sea level anomalies before they reached the moored array, and by allowing the tracking of features after they passed beyond the array, satellite altimetry provides a broad-scale context for interpreting the in situ observations, as well as a better foundation for understanding variability of mass, heat and salt fluxes in the area. This broad-scale view is particularly important as the ASTTEX array was deployed in the "Cape Cauldron" area of the Cape Basin, a region known for highly dynamic eddy-eddy interactions. Along-track sea level data from the tandem phase of the TOPEX/POSEIDON (T/P) and Jason-1 satellite altimeter missions are used to analyze eddy kinematics along the ASTTEX mooring line (which coincided with a Jason-1 groundtrack), and in the broader region surrounding the moored array. The ASTTEX deployment interval represented an excellent opportunity for observing ocean variability as the deployment commenced five months after the beginning of the tandem mission and moorings were recovered five months before the end of the tandem mission. During the 28-month deployment (January 2003 to April 2005), 11 large anticyclonic eddies were observed crossing the ASTTEX mooring line. Of these, 9 experienced significant eddy-eddy interaction, including merging and splitting events, on or after crossing the line. Kinematic properties of these eddies, including position, velocity, amplitude and spatial length scales, are presented for the ASTTEX deployment interval.