The exchange of Intermediate Water in the southeast Atlantic: Water mass transformations diagnosed from the Lagrangian analysis of a regional ocean model

Type Article
Date 2012-08
Language English
Author(s) Rimaud Julie2, Speich Sabrina2, Blanke Bruno1, 2, Grima Nicolas1, 2
Affiliation(s) 1 : CNRS Ifremer IRD UBO, UMR 6523, Lab Phys Oceans, FR-29238 Brest 3, France.
Source Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2012-08 , Vol. 117 , N. C08034 , P. 21p.
DOI 10.1029/2012JC008059
WOS© Times Cited 15
Abstract Results from a regional ocean model and numerical Lagrangian analyses are compared with in situ measurements to describe the properties and dynamics of Antarctic Intermediate Water (AAIW) in the region of the Cape Basin. The AAIW that originates in the South Atlantic (A-AAIW) at 8 degrees W follows two branches. A southern branch, flowing mostly south of 40 degrees S, is blocked by topography and is deflected westward without significant changes in its physical properties. A northern branch crosses the Cape Basin with strong modification of its physical properties. The AAIW that originates in the Indian Ocean (I-AAIW) flows into the Atlantic Ocean via the Agulhas Current and undergoes small physical changes in the Cape Basin. In the model, the salinity ranges of A-AAIW and I-AAIW cores that reach the southeast Atlantic are 34.2-34.5 and 34.5-34.6, respectively. The modeled AAIW distribution and behavior compare well with observations, despite a bias of +0.2 in salinity. To investigate the dynamical processes involved in the interocean exchanges of these AAIW varieties, we use diagnoses based on the Okubo-Weiss parameter and the directional variations of trajectories of particles transported by the model velocity field. Our results suggest that I-AAIW flows into the Cape Basin more within eddies, and particularly within cyclones, than A-AAIW. Once the mixing of both varieties operates, physical and behavioral differences fade and the resulting AAIW flows over the Walvis Ridge in a less turbulent way as part of the Benguela Current, with salinity between 34.55 and 34.6.
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Rimaud Julie, Speich Sabrina, Blanke Bruno, Grima Nicolas (2012). The exchange of Intermediate Water in the southeast Atlantic: Water mass transformations diagnosed from the Lagrangian analysis of a regional ocean model. Journal Of Geophysical Research-oceans, 117(C08034), 21p. Publisher's official version : https://doi.org/10.1029/2012JC008059 , Open Access version : https://archimer.ifremer.fr/doc/00098/20921/