CoAuthors

Martin Saraceno (UBA-CIMA-CONICET, Argentina); Alberto Piola (SHN, Argentina)

The Patagonia continental shelf is a vast region within the Southwestern Atlantic Ocean that is known for its high primary production rates and, consequently, for the wide biological diversity present there. To better understand the biological patterns observed, it is necessary to deepen the knowledge of the physical processes that they are exposed to. In this study, we analyze two direct velocity observations of up to 18 months, measured over the South-Patagonia continental shelf, located along 44.7S at the 90 and 110 m isobaths, respectively, in addition to altimetry satellite data. Results show that the barotropic circulation dominates the dynamics at both sites, with a mean flow towards the west-northwestin the inner shelf and to the north in the outer shelf. The variability of the meridional barotropic velocity in the inner shelf is dominated by the local meridional wind stress. The in-situ barotropic velocity in the outer shelf presented a mean value of 7 cm s-1 and a range between -10 and 30 cm s-1 and is partially influenced by the meridional wind stress. We hypothesize this mooring is embedded in a transition area, partially affected by the shelf dynamics and partially affected by the slope regime. The SLA from the L4 gridded product developed by AVISO allowed the analysis of the forcing of the circulation variability of the outer shelf measurements. In particular, we found a seasonal signal in the meridional barotropic velocity that is in agreement with a SLA zonal gradient between the middle shelf and the slope region. Through the thermosteric effect, this SLA zonal gradient is generated by the differential heating in austral summer of the shelf waters, with depths lower than 200 m, and the slope waters, with depths higher than 1000 m and subject to the relatively cold Malvinas current. We also detected an intra-seasonal signal in the outer shelf meridional velocity that is also present in the SLA of the region.