One to four weekly currents on the west coast South island New Zealand continental slope

Abstract

Current meter measurements from the west coast South Island New Zealand continental slope exhibit flows with dominant time scales of between 1 and 4 weeks as well as the expected diurnal and semidiurnal tides. The alongshore Doodson filtered daily mean flow components are marginally correlated with the alongshore wind. The onshore flow components are marginally correlated with the envelope of the square of the semidiurnal and diurnal tidal flow, which is taken as a measure of energy loss from the tide. Observations from the southern flank of the Challenger Plateau, 200 km north of the continental slope observations and further offshore, also exhibit similar long-period variations. However, here the alongshore flow is more strongly correlated with alongshore wind than at the southern site.