The role of the Magellan Strait on the southwest South Atlantic shelf

Abstract

We analyze historical hydrographic data together with recent high-resolution hydrographic and underwater glider observations collected in the Magellan Strait to determine the water mass characteristics and exchanges between the continental shelves of the southeast South Pacific and southwest South Atlantic around southern South America. The near-surface salinity distribution and water mass analyses indicate a strong interoceanic connectivity associated with diluted subantarctic waters of the Pacific Ocean through the Magellan Strait which in turn are further diluted largely by inflows from the Almirantazgo Fjord via the Whiteside Channel. The lowest salinity waters reach the Atlantic shelf via the Magellan Strait. This core of low salinity waters (S < 31.5) are observed on the northern portion of the strait's Atlantic mouth and creates a strong baroclinic signal that leads to intense eastward geostrophic velocities suggesting a net Pacific to Atlantic transport (0.038–0.074 Sv, 1 Sv = 106 m3 s−1). This flow plays a significant role on the thermohaline characteristics and extent of the subantarctic shelf waters that occupy the Atlantic shelf. The low salinity inflow from the Magellan Strait combines with saltier inflows through the Le Maire Strait and farther east that feed the Atlantic shelf.