Circulation and transports in the Newfoundland Basin, western subpolar North Atlantic

• Published in: Journal of geophysical research. Oceans 2014-11, Vol.119 (11), p.7772-7793
• Main Authors: Mertens, Christian, Rhein, Monika, Walter, Maren, Böning, Claus W., Behrens, Erik, Kieke, Dagmar, Steinfeldt, Reiner, Stöber, Uwe
• Format: Article
• Language: English
• Subjects: Boundaries; Circulation; Continental slope; Deep water; deep western boundary current; Density; Flemish Cap; Geophysics; Marine; Newfoundland Basin; North Atlantic current; Ocean circulation; Ocean currents; Ocean models; Sea currents; Slopes; Transport; Water circulation; Water flow
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2014JC010019

The southwestern part of the subpolar North Atlantic east of the Grand Banks of Newfoundland and Flemish Cap is a crucial area for the Atlantic Meridional Overturning Circulation. Here the exchange between subpolar and subtropical gyre takes place, southward flowing cold and fresh water is replaced by northward flowing warm and salty water within the North Atlantic Current (NAC). As part of a long‐term experiment, the circulation east of Flemish Cap has been studied by seven repeat hydrographic sections along 47°N (2003–2011), a 2 year time series of current velocities at the continental slope (2009–2011), 19 years of sea surface height, and 47 years of output from an eddy resolving ocean circulation model. The structure of the flow field in the measurements and the model shows a deep reaching NAC with adjacent recirculation and two distinct cores of southward flow in the Deep Western Boundary Current (DWBC): one core above the continental slope with maximum velocities at mid‐depth and the second farther east with bottom‐intensified velocities. The western core of the DWBC is rather stable, while the offshore core shows high temporal variability that in the model is correlated with the NAC strength. About 30 Sv of deep water flow southward below a density of σθ = 27.68 kg m−3 in the DWBC. The NAC transports about 110 Sv northward, approximately 15 Sv originating from the DWBC, and 75 Sv recirculating locally east of the NAC, leaving 20 Sv to be supplied by the NAC from the south. Key Points Direct current measurements in the southwestern subpolar North Atlantic North Atlantic Current (NAC) transports 110 Sv, 75 Sv recirculating locally Deep Western Boundary Current transports 30 Sv, 15 Sv recirculating into NAC