On the Mechanisms of Decadal Variability of the Wind-Driven Ocean Circulation

Andrew McC. Hogg, Peter D. Killworth, William K. Dewar, and Jeffrey R. Blundell

Eddy resolving quasigeostrophic simulations of wind-driven circulation in a large ocean basin are presented. The results show that strong modes of low-frequency variability arise in many parameter regimes, and that the strength of these modes depends upon the presence of inertial recirculations in the flow field. The inertial recirculations arise through advection of anomalous potential vorticity by the western boundary current, and are barotropised by the effect of baroclinic eddies in the flow. We explore the mechanism of low-frequency oscillations with reference to previous studies, and find that the observed mode can be linked to the gyre mode, but is strongly modified by the effect of eddies.