Overflows and Upper Ocean Interaction: A Mechanism for the Azores Current

摘要

The oceanic response to overflows is explored using a two-layer isopycnal model. Overflows are a major source of the dense water of the global deep ocean, originating from only a few marginal seas. They enter the open ocean as dense gravity currents down a continental slope and play a crucial role in the deep ocean circulation. To understand the dynarnics of these overflows, previous studies simplified their dynam- ics by treating the overlying ocean as inactive. This simplification may be a first approximation for the overflow but not for the overlying ocean. The Mediterranean overflow, for example, entralns about 2 Sv of overlying Atlaritic water when it enters the Atlantic through Gibraltar Strait. The upper ocean must balance the mass loss and vortex stretching associated with entrainment. Thus for the upper ocean, overflows represent a localized region of intense mass and PV forcing.