Physical and chemical oceanographic observations off westland, new zealand, june 1979

Abstract

In June 1979, temperature, salinity, dissolved oxygen, reactive phosphorus, reactive silicate, and nitrate nitrogen data were collected along 3 transects off Cape Foulwind, Greymouth, and Wanganui Bluff west of the South Island. Water entered the study area from the vicinity of the Challenger Plateau. It apparently arrived from the north and northwest, guided by the morphology of the plateau, and turned to flow southwestwards along the continental slope. There is some evidence of recirculation to the north close inshore. These flows appear to contribute to a surface and subsurface temperature maximum parallel to the coast, to a subsurface salinity maximum at least off Wanganui Bluff, to a maximum in the depth of the mixed layer parallel to the coast, and to warm, more saline water with minimum surface reactive phosphorus and silicate concentrations approaching the coast more closely off Greymouth. Freshwater runoff diluted coastal water to the greatest extent off Cape Foulwind and Greymouth. This river water contributed to the levels of reactive silicate since there was a significant negative correlation between salinity and reactive silicate. Upwelling, possibly wind‐induced, brought subsurface water from about 75 m to the surface off Wanganui Bluff, thus raising the inshore temperature, salinity, and dissolved nutrients, and slightly lowering dissolved oxygen concentrations. © 1983 Taylor & Francis Group, LLC.