Abyssal Upwelling and Downwelling and the role of boundary layers

The bottom-intensified mixing activity arising from the interaction of internal tides with bottom topography implies that the dianeutral advection in the ocean interior is downwards, rather than upwards as is required by continuity. The upwelling of Bottom Water through density surfaces in the deep ocean is however possible because of the sloping nature of the sea floor. A budget study of the abyss (deeper than 2000m) will be described that shows that while the upwelling of Bottom Water might be ~25 Sv, this is achieved by very strong upwelling in the bottom turbulent boundary layer (of thickness ~50m) of ~100 Sv and strong downwelling in the ocean interior of ~75 Sv. This downwelling occurs within 10 degrees of longitude of the continental boundaries. This near-boundary confined strong upwelling and downwelling clearly has implications for the Stommel-Arons circulation.