Mechanisms of Interannual Variations of the Meridional Overturning Circulation of the North Atlantic Ocean. - Archive ouverte HAL
Article Dans Une Revue Journal of Physical Oceanography Année : 2008

Mechanisms of Interannual Variations of the Meridional Overturning Circulation of the North Atlantic Ocean.

Résumé

The authors investigate the nature of the interannual variability of the meridional overturning circulation (MOC) of the North Atlantic Ocean using an Estimating the Circulation and Climate of the Ocean (ECCO) assimilation product for the period of 1993–2003. The time series of the first empirical orthogonal function of the MOC is found to be correlated with the North Atlantic Oscillation (NAO) index, while the associated circulation anomalies correspond to cells extending over the full ocean depth. Model sensitivity experiments suggest that the wind is responsible for most of this interannual variability, at least south of 40°N. A dynamical decomposition of the meridional streamfunction allows a further look into the mechanisms. In particular, the contributions associated with 1) the Ekman flow and its depth-independent compensation, 2) the vertical shear flow, and 3) the barotropic gyre flowing over zonally varying topography are examined. Ekman processes are found to dominate the shorter time scales (1.5–3 yr), while for longer time scales (3–10 yr) the MOC variations associated with vertical shear flow are of greater importance. The latter is primarily caused by heaving of the pycnocline in the western subtropics associated with the stronger wind forcing. Finally, how these changes in the MOC affect the meridional heat transport (MHT) is examined. It is found that overall, Ekman processes explain a larger part of interannual variability (3–10 yr) for MHT (57%) than for the MOC (33%).

Domaines

Océanographie

Dates et versions

hal-00400047 , version 1 (29-06-2009)

Identifiants

Citer

Cécile Cabanes, Tong Lee, Lee-Lueng Fu. Mechanisms of Interannual Variations of the Meridional Overturning Circulation of the North Atlantic Ocean.. Journal of Physical Oceanography, 2008, 38 (2), pp.467-480. ⟨10.1175/2007JPO3726.1⟩. ⟨hal-00400047⟩
76 Consultations
0 Téléchargements

Altmetric

Partager

More