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 (NO_x‐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.

Keywords:

• upwelling
• downwelling
• wind
• shelf currents
• Bay of Plenty