On the mechanism of decadal oscillations in a coarse resolution ocean model

The physical mechanism that causes an interdecadal oscillation in a coarse resolution sector ocean model forced by mixed boundary conditions is studie d. The oscillation is characterized by large fluctuations in convective act ivity and air/sea heat exchange on a decadal timescale. Changes in the subs urface temperature and surface salinity are essential for the existence of the oscillation. It is shown that a large part of these variations can be e xplained with the hypothesis of a constant ocean velocity field. This may e asily lead to the erroneous conclusion that the oscillation is mainly a "no ndynamical" phenomenon. In this paper it is demonstrated that the ocean dyn amics play an essential role in explaining decadal oscillations.