The Spreading of Lower Circumpolar Deep Water in the Atlantic Ocean

Abstract

A Stommel-Arons model of the circulation of Lower Circumpolar Deep Water (LCDW) in the Atlantic Ocean is presented and compared with observations. The LCDW is defined as a layer of uniform thickness over a flat bottom; the lateral boundaries are given by the 4000-m isobath. The Drake Passage and the throughflow between Africa and Antarctica are closed. The model is forced by a concentrated source in the Weddell Sea representing the net Atlantic gain of LCDW due to production in the Weddell Sea and inflow through Drake Passage. This net gain is termed the LCDW formation rate. It is compensated by upwelling over the rest of the Atlantic. Best agreement with observed net transport rates in the western Atlantic was found using a LCDW formation rate of about 8 Sv (Sv ≡ 106 m3 s?1). In reality, however, a higher rate is required in order to establish the outflow to the Indian Ocean. The interior transport, the transport through topographic gaps, and the transport rates of western boundary currants on the eastern flanks of topographic barriers are calculated and compared with observations where available. In additional runs it was found that raising the production rate to a value of 13 Sv and enabling simultaneously an LCDW outflow of 5 Sv into the Indian Ocean can explain observed very high transport rates in the South Sandwich Trench. Consequences of different patterns of nonuniform upwelling are discussed.