ABSTRACT
This is the largest and deepest of the oceans. All the deep water originates off Antarctica and flows northwards at depths >2500 m. In the South Pacific the bottom-water temperatures are 0.5-2.5 °C and salinity 34.70-34.74‰. It takes roughly 1000 years for the water to reach the North Pacific and during this time oxygen is reduced and phosphate levels increased. The AABW flows as a contour current and passes from one basin to the next through fracture zones in the ocean ridges. The CCD lies at 4200-4500 m over much of the ocean but it is depressed to 5000 m beneath the equatorial zone of high productivity and becomes shallower (<3000 m) close to the continental margins. Consequently carbonate sediments are restricted to the East Pacific Rise and Lord Howe Rise-New Zealand Platform. Elsewhere the sediments are carbonate-poor or non-carbonate abyssal clays (Kennett 1982).
