The exchange of Intermediate Water in the southeast Atlantic: Water mass transformations diagnosed from the Lagrangian analysis of a regional ocean model
Article first published online: 25 AUG 2012
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 117, Issue C8, August 2012
How to Cite
2012), The exchange of Intermediate Water in the southeast Atlantic: Water mass transformations diagnosed from the Lagrangian analysis of a regional ocean model, J. Geophys. Res., 117, C08034, doi:10.1029/2012JC008059., , , and (
- Issue published online: 25 AUG 2012
- Article first published online: 25 AUG 2012
- Manuscript Accepted: 11 JUN 2012
- Manuscript Revised: 7 JUN 2012
- Manuscript Received: 18 MAR 2012
- Agulhas system;
- interbasin exchanges;
 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°W follows two branches. A southern branch, flowing mostly south of 40°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.