Flow and hydrological variability in the Kahurangi plume off north‐west South Island, New Zealand

Abstract

Non‐tidal daily mean currents on the south‐west flank of Kahurangi Shoals are strongly correlated with the local alongshore wind. A correlation equation was established which accounted for 71% of the variance in the non‐tidal flow. This equation also provides realistic estimates of the surface and bottom drag coefficients. Upwelling is prevalent along the north‐west coast of the South Island. Under northwards directed alongshore winds in mid March 1983 a plume of cold, saline, nutrient‐rich water moved northwards and offshore from north of Kahurangi Point. Warm, less nutrient‐rich water moved south from near Cape Farewell between the coast and the plume. A prominent front was developed between these two waters. The plume water in western Cook Strait met the water from the East Cape Current in a subsurface front. The Kahurangi plume can have patches of minimum‐temperature water embedded in it. The spacing of about 20 km between patches is consistent with daily modulation of the plume.

Keywords:

• plume
• currents
• upwelling, tides