Journal of Geophysical Research: Oceans

Interocean exchanges and the spreading of Antarctic Intermediate Water south of Africa

Authors

  • Emanuela Rusciano,

    Corresponding author
    1. Laboratoire de Physique des Océans, CNRS/IFREMER/IRD/UBO, IFREMER/Centre de Brest, Plouzané, France
      Corresponding author: E. Rusciano, Laboratoire de Physique des Océans, CNRS/IFREMER/IRD/UBO, IFREMER/Centre de Brest, BP70, FR-29280 Plouzané, France. (emanuela.rusciano@univ-brest.fr)
    Search for more papers by this author
  • Sabrina Speich,

    1. Laboratoire de Physique des Océans, CNRS/IFREMER/IRD/UBO, UBO-UFR Sciences et Techniques, Brest, France
    Search for more papers by this author
  • Michel Ollitrault

    1. Laboratoire de Physique des Océans, CNRS/IFREMER/IRD/UBO, IFREMER/Centre de Brest, Plouzané, France
    Search for more papers by this author

Corresponding author: E. Rusciano, Laboratoire de Physique des Océans, CNRS/IFREMER/IRD/UBO, IFREMER/Centre de Brest, BP70, FR-29280 Plouzané, France. (emanuela.rusciano@univ-brest.fr)

Abstract

[1] Argo hydrographic profiles collected from 2004 to 2011 in the southeast Atlantic sector of the Southern Ocean are used in combination with hydrographic transects to describe the characteristics of Antarctic Intermediate Water (AAIW) in the region. Making use of the recently developed ANDRO velocity data set, we estimate the evolution of the dynamical properties of different AAIW varieties along their pathways within the isoneutral layer (27.1 < γn < 27.6). Three different regional varieties of intermediate water converge in the southeast Atlantic: Atlantic AAIW (A-AAIW, characterized by S ≤ 34.2), Indian AAIW (I-AAIW, S ≥ 34.3), and a previously unknown variety that we named Indo-Atlantic intermediate water (IA-AAIW, 34.2 < S < 34.3). South of Africa, the I-AAIW flowing within the Agulhas Current separates into two branches. One branch retroflects following the Agulhas Return Current (13.4 Sv) and proceeds back to the Indian Ocean. The other one separates from the Agulhas Current, and flows into the southeast Atlantic via the Cape Basin within mesoscale eddies (13.5 Sv). A-AAIW enters the domain between the Subtropical Front and the Subantarctic Front (36 Sv). Part of this water (28 Sv) flows eastward into the Indian Ocean, while 10 Sv are injected into the Cape Basin and mix with I-AAIW giving rise to the new IA-AAIW variety. The latter separates into two branches, both transporting 7.4 Sv. One flows northwestward and subducts along the Northern Subtropical Front, while the other moves eastward to contribute a sizable volume of fresh and oxygenated water to the Indian Ocean.

Ancillary