Abstract
Abstract. The Patagonia continental shelf located off southeastern South America is bounded offshore by the Malvinas Current, which extends northward from northern Drake Passage (~55° S) to nearly 38° S. The transition between relatively warm-fresh shelf waters and Subantarctic Waters from the western boundary current is characterized by a thermohaline front extending nearly 2500 km. We use satellite derived sea surface temperature, and chlorophyll-a data combined with hydrographic and surface drifter data to document the intrusions of slope waters onto the continental shelf near 41° S. These intrusions create vertically coherent localized negative temperature and positive salinity anomalies extending onshore about 150 km from the shelf break. The region is associated with a center of action of the first mode of non-seasonal sea surface temperature variability and also relatively high chlorophyll-a variability, suggesting that the intrusions are important in promoting the local development of phytoplankton. The generation of slope water penetrations at this location may be triggered by the inshore excursion of the 100 m isobath, which appears to steer the Malvinas Current waters over the outer shelf.
Highlights
Continental shelf-open ocean interactions lead to the exchange of mass, water properties and momentum (Loder et al, 1998), and may be important in the maintenance of the shelf ecosystems and carbon fluxes to the deep ocean
The Csata distribution clearly indicates that, whatever mechanism lead to the anomalous phytoplankton development over the northern Patagonia continental shelf, its effects were substantially enhanced near 40–41◦ S, the region where the slope water intrusions are documented in this paper
We have presented evidence of intense slope water intrusions onto the northern Patagonia continental shelf near 41◦ S
Summary
Continental shelf-open ocean interactions lead to the exchange of mass, water properties and momentum (Loder et al, 1998), and may be important in the maintenance of the shelf ecosystems and carbon fluxes to the deep ocean. Shelf open-ocean interactions between the MC and the outer shelf off northern Patagonia do not appear to be dominated by mesoscale eddies, as further north This portion of the slope region presents intense chlorophyll blooms (Podesta, 1997; Longhurst, 1998; Saraceno et al, 2005; Romero et al, 2006; Signorini et al, 2006) and is important for the life cycle of a variety of species throughout the water column and in the benthic domains (Podesta, 1989; Bertolotti et al, 1996; Sanchez and Ciechomski, 1995; Rodhouse et al, 2001; Acha et al, 2004; Bogazzi et al, 2005).
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