Antarctic intermediate water and subantarctic mode water formation in the Southeast Pacific: The role of turbulent mixing

Bernadette M. Sloyan, Lynne D. Talley, Teresa K. Chereskin, Rana Fine, James Holte

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60 Scopus citations

Abstract

During the 2005 austral winter (lateAugust-earlyOctober) and 2006 austral summer (February-mid-March) two intensive hydrographic surveys of the southeast Pacific sector of the Southern Ocean were completed. In this study the turbulent kinetic energy dissipation rate ε, diapycnal diffusivity κ, and buoyancy flux Jb are estimated from the CTD/O2 and XCTD profiles for each survey. Enhanced κ of O(10-3 to 10-4 m2 s-1) is found near the Subantarctic Front (SAF) during both surveys. During the winter survey, enhanced κ was also observed north of the "subduction front," the northern boundary of the winter deep mixed layer north of the SAF. In contrast, the summer survey found enhanced κ across the entire region north of the SAF below the shallow seasonal mixed layer. The enhanced κ below the mixed layer decays rapidly with depth. A number of ocean processes are considered that may provide the energy flux necessary to support the observed diffusivity. The observed buoyancy flux (4.0×10-8 m2 s-3) surrounding the SAFduring the summer survey is comparable to the mean buoyancy flux (0.57 × 10-8 m2 s-3) associated with the change in the interior stratification between austral summer and autumn, determined from Argo profiles. The authors suggest that reduced ocean stratification during austral summer and autumn, by interior mixing, preconditions the water column for the rapid development of deep mixed layers and efficient Antarctic Intermediate Water and Subantarctic Mode Water formation during austral winter and early spring.

Original languageEnglish (US)
Pages (from-to)1558-1574
Number of pages17
JournalJournal of Physical Oceanography
Volume40
Issue number7
DOIs
StatePublished - Jul 2010

Keywords

  • Fronts
  • Intermediate waters
  • Mixing
  • Southern Ocean
  • Turbulence
  • Water masses

ASJC Scopus subject areas

  • Oceanography

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