NADW and AABW: Their Interaction and Influence on the Variability of the Global Ocean Circulation

Holger Brix¹, and Rüdiger Gerdes, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
¹Now at Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California, USA

  Interhemispheric signal transmission in the Atlantic Ocean connects
  the deep water production regions of both hemispheres. The nature of
  these interactions and large scale responses to perturbations on
  time scales of years to millennia have been investigated using a
  global three-dimensional ocean general circulation model coupled to
  a dynamic-thermodynamic sea ice model. The coupled model reproduces
  many aspects of today's oceanic circulation. A set of experiments
  shows the sensitivity to changes in different surface boundary
  conditions. Buoyancy changes in the Weddell and Labrador Seas exert
  a direct effect on the overturning cells of the respective
  hemisphere. They influence the density structure of the deep ocean
  and thereby lead to alterations in the strength of the ACC.
  Changing the wind stress south of 30oS influences the
  magnitude of the deep water production of both hemispheres. The
  interhemispheric effect in these experiments cannot be explained
  solely by advective mechanisms. Switching off the wind stress over
  the latitude band of the Drake Passage leads to a slow gradual
  decrease of the water mass transport in the ACC resulting in an
  almost complete cessation. The model results prove the necessity to
  continue integrations over thousands of years until new equilibria
  are established.

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