Sea level anomaly on the Patagonian continental shelf: Trends, annual patterns and geostrophic flows

MARTIN SARACENO; LAURA AGUSTINA, RUIZ ETCHEVERRY; P.T. STRUB; PIOLA, A. R.

JOURNAL OF GEOPHYSICAL RESEARCH

AMER GEOPHYSICAL UNION

Año: 2016 vol. 121 p. 2733 - 2754

0148-0227

We study the annual patterns and linear trend of satellite sea level anomaly (SLA) over thesouthwest South Atlantic continental shelf (SWACS) between 54S and 36S. Results show that south of428S the thermal steric effect explains nearly 100% of the annual amplitude of the SLA, while north of 428Sit explains less than 60%. This difference is due to the halosteric contribution. The annual wind variabilityplays a minor role over the whole continental shelf. The temporal linear trend in SLA ranges between 1 and5 mm/yr (95% confidence level). The largest linear trends are found north of 398S, at 428S and at 508S. Wepropose that in the northern region the large positive linear trends are associated with local changes in thedensity field caused by advective effects in response to a southward displacement of the South AtlanticHigh. The causes of the relative large SLA trends in two southern coastal regions are discussed as a functionmeridional wind stress and river discharge. Finally, we combined the annual cycle of SLA with the meandynamic topography to estimate the absolute geostrophic velocities. This approach provides the first comprehensivedescription of the seasonal component of SWACS circulation based on satellite observations.The general circulation of the SWACS is northeastward with stronger/weaker geostrophic currents in australsummer/winter. At all latitudes, geostrophic velocities are larger (up to 20 cm/s) close to the shelf-break anddecrease toward the coast. This spatio-temporal pattern is more intense north of 458S.