ABSTRACT
In the marine dynamics of continental shelf waters the phenomenon of upwelling is of considerable significance. On the one hand, it represents the product of a complex interaction between the atmosphere and ocean on a rotating earth, and, on the other, it has great practical implications in both climate modification and in its ability to inject nutrients into the surface layers. The latter feature is particularly true of limited sections of the southern coastal zone of Australia. For the greater part of each year this vast zone experiences a persistent west to east current, trapped on the shelf in the characteristic southern hemisphere downwelling condition. 1 It is not surprising then, that the coastal waters of much of this region have often been termed a biological desert. This unfavorable condition seems to be relieved intermittently during the summer period, when the latitudinal shift of zonal barometric pressures allows the eastward-tracking high pressure systems to linger occasionally in the Great Australian Bight (Figure 1 inset). Given stability over a number of days, the associated southeasterly wind field in the eastern Bight region (detail shown in Figure 1) may halt the southeast-going current and reverse its flow to create conditions suitable for upwelling. That such upwelling features do occur has been established beyond doubt by observation of water properties and by satellite remote sensing of sea-surface temperatures. 2 It is also clear that a rock lobster fishery is supported by the system. 3 However, the evidence suggests that prolonged favorable conditions occur infrequently and that there are preferred localities for upwelling cells to develop. It is therefore important to understand the physics of the upwelling mechanism in greater detail.
