Low frequency variability of the Zapiola Anticyclone as observed from satellite altimetry: indication of possible collapses

SARACENO, M., AND C. PROVOST

Puerto Madryn, Argentina

Jornada; VI Jornadas Nacionales de Ciencias del Mar; 2006

The Zapiola Rise (ZR) is a unique sedimentary deposit of about 1200 m in elevation and 1500 km in horizontal scale located in the Argentinean basin.  In situ and satellite observations have revealed the presence of an intense counterclockwise circulation around the feature with a volume transport comparable to those of the largest ocean currents. Here we examine low frequency variations of that anticyclonic circulation. A 13- year (1993-2005) time series of transport is produced using geostrophic velocities estimated from the combination of satellite Sea Level Anomalies (SLA) and a Mean Dynamic Topography.  Prior to estimating the transport, the accuracy of the altimeter-derived geostrophic velocities is tested by comparison with velocities estimated from (i) two profilers that drifted at 1500m depth trapped in the region during 15 months and (ii) in-situ measurements from the WOCE A-11 section. The transport presents high frequency variability associated to mesoscale activity superposed to a low frequency signal. The low frequency signal is so strong that at times the Zapiola anticyclone may have disappeared.