Transient wind-driven coastal upwelling on a shelf with varying width and orientation

Abstract

Cross-correlations between along-shelf wind stress and both along- and cross-shelf currents within the central Bay of Plenty, New Zealand show the circulation during spring–summer to be highly responsive to wind events. Current meter records indicate that upwelling-favourable wind stresses generate upwelling dynamics in both mean and fluctuating senses. Both thermistor moorings and satellite inferred temperature data record the outcropping of this cool water following upwelling-favourable wind stresses. The upwelling circulation provides an efficient mechanism for the periodic delivery of cool (c. <15°C), nutrient rich (NOx- N >80 µg litre–1 ) water to the coastal zone during spring. Historical wind forcing data suggest that the wind-forced dynamics described were responsible for a major toxic algal bloom within the Bay of Plenty during 1992–93.