Northward abyssal transport through the Samoan passage and adjacent regions

A conductivity-temperature-depth/hydrographic survey in January-February 1994 and a 17-month deployment of current meter moorings from September 1992 to March 1994 were carried out to determine the volume transport, water mass characteristics, and diathermal fluxes of northward flowing abyssal waters in the Samoan Passage and adjacent regions of the South Pacific Ocean. Geostrophic calculations relative to 1.2 degrees C potential temperature indicated northward transport of 7.8 Sv in the Samoan Passage, 1.1 Sv through a gap in Robbie Ridge, and 2.8 Sv along the eastern flank of the Manihiki Plateau. All of the total of 11.7 Sv of northward geostrophic transport was in waters colder than 1.1 degrees C. The northward transport distribution was bimodal in temperature, with a cold mode of 3.6 Sv in the range 0.65 degrees-0.70 degrees C occurring entirely in the Samoan Passage and a warm mode of 3.0 Sv in the range of 0.8 degrees-0.85 degrees C occurring mainly along the Manihiki Plateau. Within the Samoan Passage, 7.1 Sv of the northward transport was below 4000 m where the geostrophic calculation was confirmed by an equal estimate of transport from current meters during the simultaneous 3-day period. The 17-month mean transport from the moored array was 6.0 Sv +/- 0.5. By using the observed temporally varying flow within the Samoan Passage together with the hydrographic snapshot across the region, an estimate of the total mean northward transport of 10.6 Sv +/- 1.7 was obtained. Estimates of the flow across near-bottom potential temperature surfaces indicate extraordinarily high rates of mixing, with heating of the abyssal layer up to 20 W m(-2), corresponding to diffusivities up to 10(-1) m(2) s(-1).