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AGU: Journal of Geophysical Research, Oceans

 

Keywords

  • Arctic
  • double diffusive mixing
  • mixing process
  • vertical heat transfer

Index Terms

  • 4568 - Turbulence, diffusion, and mixing processes

Paper in Press

JOURNAL OF GEOPHYSICAL RESEARCH, doi:10.1029/2012JC007910

Vertical heat transfer in the Arctic Ocean: The role of double-diffusive mixing

Key Points
  • Detection of thermohaline staircase structure in Amundsen Basin
  • Quantification of vertical heat transfer by diffusive convection
  • Evaluation of diffusive convection parameterization

Authors:

Anders Sirevaag

Ilker Fer

Microstructure profiles collected in the central Amundsen Basin are analyzed in order to quantify the role of double-diffusive mixing for vertical heat transfer from the Atlantic layer. In the profiles, a persistent, but laterally incoherent thermohaline staircase structure is identified in the 200 - 260 m depth range. The staircase contains homogeneous layers with average height of 1.3 m and thin, high-gradient interfaces with average temperature and salinity jumps of about 0.065 {degree sign}C and 0.015, respectively. When inferred from a commonly used diffusive convection parameterization, the average vertical heat flux within the staircase is 0.6 W m-2. This is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the Atlantic layer in the deep basins of the Arctic Ocean. The parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude, especially for weak thermal forcing (small temperature jumps in staircase). Staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles. Lomonosov Ridge is identified as a potential region for formation of intrusions. It is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins.

Received 23 January 2012; accepted 25 May 2012.

Citation: Sirevaag, A. and I. Fer (2012), Vertical heat transfer in the Arctic Ocean: The role of double-diffusive mixing, J. Geophys. Res., doi:10.1029/2012JC007910, in press.