Stratified Abyssal Flow in the Presence of Fractured Ridges

Abstract

A linear, two-layer model for abyssal flow driven by a specified upwelling into the thermocline is studied when the ocean basin is partially blocked by a meridional barrier in the lower layer. The barrier is meant to represent a midoceanic ridge, and the space between the termination points of the ridge and the northern and southern basin boundaries represents the gaps that pierce most ridge systems. It is found that the deep flow is only partially blocked by the barrier. A substantial flow threads through the gaps in the form of zonal jets. The portion of the flow that is blocked by the ridge produces a recirculating, cyclonic gyre east of the ridge, and its latitudinal extent is typically smaller than the unbroken interval of the ridge. The overall structure of the recirculation and the degree of blocking are related to robust integral conditions constraining the circulation around the ridge. Although weaker, a similar recirculation is often found in the unblocked layer above the ridge as an upward extension of the deep circulation.