An Antarctic oceanographic section along 170°E

Abstract

The circulation pattern of Antarctic and sub-Antarctic waters is strongly influenced by the complex marine topography south of New Zealand. The distribution of water characteristics indicates that the Antarctic Circumpolar Current undergoes intense wave-like migrations, which may be transient in nature, apparently associated with the Macquarie Ridge and Campbell Plateau. The bulk of the circumpolar current transport flows eastward over the northern flank of the mid-ocean ridge, but a strong, apparently jet-like, current exists around the periphery of the Campbell Plateau. The water column of the upper 1000 m possesses much thermohaline complex structure on vertical scales of 20–200 m in the Polar Front zone along 170°E from 56 to 62°S. South of 62°S the water column is well stratified with a strong temperature minimum at 100 m, while north of 56°S is the well-mixed, thick, Sub-Antarctic Surface Water. The geostrophic volume transport relative to the deepest common depth of station pairs, is 135 × 10 6 m 3 s −1. The bottom velocities are not zero and the actual transport is quite different from the baroclinic transport. Bottom current (100 m above the sea floor) at 56°S average, for a three-day period, is 29 cm s −1 towards 065° T. Using this for geostrophic reference suggests that the current around the Campbell Plateau periphery has a surface zonal velocity of 1·5 knots.