Transport of Bottom Water in the Romanche Fracture Zone and the Chain Fracture Zone

Abstract

Two moored arrays deployed in the Romanche Fracture Zone and Chain Fracture Zone in the equatorial Atlantic Ocean provide two-year-long time series of current and temperature in the Lower North Atlantic Deep Water and the Antarctic Bottom Water. Total time-averaged transport of Antarctic Bottom Water (potential temperature ? < 1.9°C) across the Mid-Atlantic Ridge amounts to 1.22 ? 106 m3 s?1 eastward with a standard deviation of ±0.25 ? 106 m3 s?1. A time-averaged transport of 0.36(± 0.23) ? 106 m3 s?1 eastward is found for the Lower North Atlantic Deep Water in the 1.9° < ? < 2.1°C temperature range, but this may represent only a fraction of the total flow of this water mass across the ridge. Contributions of the Romanche Fracture Zone and Chain Fracture Zone to the Antarctic Bottom Water transport are similar, while the Chain Fracture Zone has the greater share of Lower North Atlantic Deep Water transport. Semiannual and annual periods are detected in the transport time series and together explain 24% of the Antarctic Bottom Water transport variance in the Romanche Fracture Zone. In the Chain Fracture Zone, Antarctic Bottom Water transport variance is dominated by fluctuations in the period band 10?20 days.