Seasonal Sea Level Anomaly patterns over Argentine Continental Shelf

LAURA RUIZ ETCHEVERRY AND MARTÍN SARACENO

Riva del Garda

Workshop; 6th Coastal altimetry workshop; 2012

Argentine Continental shelf circulation has been studied principally with numerical models. Results of these models have shown a marked seasonal behavior of the currents. The seasonal pattern has been described also with in-situ data but only for a limited number of dates corresponding to oceanographic campaigns. Satellite data provide an opportunity to solve the spatial and temporal issue. In particular, the 20-year database of sea surface height collected by radar altimeters is a unique dataset to study the circulation in regions with low density of in-situ data. Altimetry over continental shelf and coastal regions has improved considerably in the last few years, allowing researchers to study these complex areas. The aim of this work is to study the shelf circulation with gridded altimetry data produced by AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data) over the Argentine Continental Shelf (36ºS-55ºS). Our first objective was to estimate the accuracy of the data sets with in-situ data. Results show that the error is minor than 5.6 cm for periods larger than 20 days. We then analyse the seasonal component of 18 years of SLA (sea level anomaly). The seasonal signal of the SLA could be explained by the cooling and heating of the column water due to the solar radiation. This steric-effect depends on the Net Heat Flux and the thermal expansion coefficient. The results show that this effect explains almost the 100% of the seasonal SLA, south of 44ºS. However, in the northern part of the shelf, the seasonal SLA is not well represented by the steric-effect. Our hypothesis is that the climatology of Word Ocean Atlas 98 is not representing properly the thermocline in the north part of the shelf. Therefore, thermal expansion coefficient is subestimated.