Volume Transport Variability on the Northern Argentine Continental Shelf from In Situ and Satellite Altimetry Data

Abstract

Direct current observations and satellite altimetry data over the northern portion of the Argentine continental shelf are used to produce an 11-month long hourly time series and a 25-year long daily time series of along-shore volume transport, respectively. At time scales longer than 20 days, the temporal variability of the in situ transport is significantly correlated with the transport inferred from satellite altimetry (r = 0.74). The mean in situ along-shore transport is 2.65 ± 0.07 Sv (1 Sv = 106 m3 s−1) to the northeast and presents large variability, with a peak-to-peak range of 16 Sv. The extended satellite transport presents variability at multiple time scales. The annual cycle is the dominant signal, with a maximum during the austral autumn and a minimum during the austral spring. The interannual component of the transport is significantly correlated (r = −0.5) with the Southern Annular Mode (SAM). SAM-induced along-shore wind stress anomalies over the region modulate the cross-shore pressure gradient that, in turn, modulates the along-shore transport variability. This mechanism holds also at synoptic scales, highlighting the dominant role of the wind on the along-shore transport. Satellite altimetry measurements also indicate that the cross-shore pressure gradient generated by the variability of the Malvinas Current affects the along-shore transport only in the outer 30 km of the continental shelf.