Quasi-synoptic transport, budgets and water mass transformation in the Azores–Gibraltar Strait region during summer 2009

• Published in: Progress in Oceanography
• Main Authors: Carracedo, Lidia, Gilcoto, Miguel, Mercier, Herle, Fernandez Perez, Fiz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon-elsevier Science Ltd 2015
• Subjects: North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00213/32383/30847.pdf; https://doi.org/10.1016/j.pocean.2014.09.006; https://archimer.ifremer.fr/doc/00213/32383/

We describe the circulation patterns in the Azores–Gibraltar Strait region (North-Eastern Atlantic) during the 2009 CAIBOX cruise on the basis of hydrographic and direct current velocity measurements. This study offers new data for a region where importation of central waters (subpolar and subtropical modes of Eastern North Atlantic central waters) and exports of Mediterranean Water are strongly related to large-scale dynamics in the North Atlantic Ocean (Azores Current-Mediterranean Water system). The description is backed up quantitatively by the results of a box inverse model, which was used to obtain absolute water mass transport values consistent with thermal wind equations and with conservation of volume, salt and heat. The contributions of water masses were determined in an extended Optimum Multiparameter Analysis from a quasi-synoptic point of view, providing detail in addition to volume, salt and heat transport. The surface–subsurface large-scale current system in the region consists of the Azores Current (13.1 ± 2.5 Sverdrup [Sv], 1 Sv = 106 m3s-1), the Azores Counter-Current (5.2 ± 2.1 Sv), the Portugal Current (4.5 ± 1.4 Sv) and the Canary Current (7.1 ± 1.1 Sv). Broadly speaking, central waters are imported into the CAIBOX region at a rate of 1.6 ± 0.9 Sv, and Mediterranean Water is exported at a rate of 1.5 ± 0.4 Sv. The entrainment of central waters during Mediterranean Water formation was quantified at 0.8 Sv, of which 0.5 Sv are from central waters of subpolar origin and 0.3 Sv from subtropical central waters. Of the 4.9 Sv of subtropical central waters advected by the Azores Current, about 0.7 Sv would reach the Gulf of Cadiz region flow across the Gibraltar Strait as part of the Atlantic inflow to the Mediterranean Sea and to take part in central water entrainment.