The zonal dimension of the Indian Ocean Meridional Overturning Circulation

Drijfhout, S. S. and Naveira Garabato, A. C.

abstract: The three-dimensional structure of the meridional overturning circulation (MOC) in the deep Indian Ocean is investigated with an eddy-permitting ocean model. The amplitude of the modeled deep Indian Ocean MOC is 5.6 Sv (1 Sv = 10^6 m^3 s^-1), a broadly realistic but somewhat weak overturning. Although the model parameterization of diapycnal mixing is inaccurate, the model?s short spin-up allows the effective diapycnal velocity (the sum of model drift and the explicitly modeled diapycnal velocity) to resemble the true, real-ocean diapycnal velocity. For this reason, the model is able to recover the broad zonal asymmetry in the turbulent buoyancy flux that is suggested by observations. The model features a substantial deep, depth-reversing zonal circulation of nearly 50% of the MOC. The existence of this circulation, brought about by the zonally asymmetric distribution of diapycnal mixing, implies a much slower ventilation of the deep Indian Ocean (by a factor of 5-6) than would be in place without zonal interbasin exchanges. It is concluded that the zonal asymmetry in the distribution of diapycnal mixing must have a major impact on the deep Indian Ocean?s capacity to store and transform climatically significant physical and biogeochemical tracers.

  author = {Drijfhout, S. S. and Naveira~Garabato, A. C.},
  title = {The zonal dimension of the Indian Ocean Meridional Overturning Circulation},
  journal = {J. Phys. Ocean.},
  year = {2008},
  pages = {359--379},
  volume = {38},
  issue = {2},
  doi = {10.1175/2007JPO3640.1},
  url = {}