H. L. Johnson and D. P. Marshall, J. Phys. Oceanogr., 34, 1702-1722.
There is a wide range of evidence from both models and palaeoclimate data indicating the possibility of abrupt changes in the oceanic meridional overturning circulation (MOC). However, much of our dynamical understanding of the MOC comes from steady state models which rely upon the assumption of thermodynamic equilibrium, and are therefore only valid on millennial timescales. Here a dynamical model for the global teleconnections of MOC anomalies on annual to multidecadal timescales is developed. It is based on a linear theory for the propagation of zonally integrated meridional transport anomalies in a reduced gravity ocean, and allows for multiple ocean basins connected by a circumpolar channel to the south. The theory demonstrates that the equator acts as a low-pass filter to MOC anomalies. As a consequence, MOC anomalies on decadal and shorter timescales are confined to the hemispheric basin in which they are generated and have little impact on the remainder of the global ocean. The linear theory is compared with the results of a global non-linear numerical integration, which it reproduces to a good approximation.
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