MESOSCALE CIRCULATION FEATURES OF THE GREAT-BARRIER-REEF REGION INFERRED FROM NOAA SATELLITE IMAGERY

The commissioning of a NOAA satellite receiving station at Townsville in North Queensland in 1988 greatly expanded the AVHRR coverage of the northeast Australian region to include the entire Great Barrier Reef system and marginal seas. Selected imagery from this and a southern st ation installed previously at Aspendale, Victoria provide a valuable n ew perspective on oceanographic phenomena occurring in this ecological ly significant region. This perspective could not be attained using co nventional ship-board and in situ oceanographic sampling techniques. A rich spectrum of mesoscale oceanographic features is revealed in the analyzed imagery, and various features such as western boundary curren t meanders, frontal shear waves, eddies, and jets are described. The t emporal and spatial variability of these features appears strongly lin ked to that of the larger-scale Coral Sea current circulation. Several of the features identified are unique to the region, others resemble features observed in other western boundary current systems, but are s ignificantly modified by the complex regional topography, and by the p resence of the Great Barrier Reef (GBR). Evidence has been found for a number of processes which have significant implications for the origi n and maintenance of CBR ecosystems, including shelf edge exchange pro cesses, stratified slope water intrusions onto the shelf, and boundary layer mixing around reefs. Such processes provide a mechanism for inj ection of cool nutrient-rich waters into the reef matrix. The imagery provides a clear picture of a well-organized, but spatially complex, f rontal system existing in the southern Coral Sea, which is associated with enhanced commercial and recreational fishing activity in the regi on. The AVHRR imagery has thus proven to be a valuable tool for spatia l mapping of oceanographic features throughout the CBR region, for hyp othesis formation in dynamical and modeling studies, and for ship-boar d reconnaissance operations.