NORTHWARD ABYSSAL TRANSPORT THROUGH THE SAMOAN PASSAGE AND ADJACENT REGIONS

A conductivity-temperature-depth/hydrographic survey in January-Februa ry 1994 and a 17-month deployment of current meter moorings from Septe mber 1992 to March 1994 were carried out to determine the volume trans port, water mass characteristics, and diathermal fluxes of northward f lowing abyssal waters in the Samoan Passage and adjacent regions of th e South Pacific Ocean. Geostrophic calculations relative to 1.2 degree s C potential temperature indicated northward transport of 7.8 Sv in t he Samoan Passage, 1.1 Sv through a gap in Robbie Ridge, and 2.8 Sv al ong 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 tempera ture, with a cold mode of 3.6 Sv in the range 0.65 degrees-0.70 degree s 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 confi rmed 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 fl ow within the Samoan Passage together with the hydrographic snapshot a cross the region, an estimate of the total mean northward transport of 10.6 Sv +/- 1.7 was obtained. Estimates of the flow across near-botto m potential temperature surfaces indicate extraordinarily high rates o f mixing, with heating of the abyssal layer up to 20 W m(-2), correspo nding to diffusivities up to 10(-1) m(2) s(-1).