Mesoscale circulation features of the great barrier reef region inferred from NOAA satellite imagery

Abstract

The commissioning of a NOAA satellite receiving station at Townsville in North Queensland in 1988 greatly expanded the A VHRR coverage of the northeast Australian region to include the entire Great Barrier Reef system and marginal seas. Selected imagery from this and a southern station installed previously at Aspendale, Victoria provide a valuable new perspective on oceanographic phenomena occurring in this ecologically significant region. This perspective could not be attained using conventional 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 current meanders, frontal shear waves, eddies, and jets are described. The temporal and spatial variability of these features appears strongly linked 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 significantly modified by the complex regional topography, and by the presence of the Great Barrier Reef (GBR). Evidence has been found for a number of processes which have significant implications for the origin and maintenance of GBR ecosystems, including shelf edge exchange processes, stratified slope water intrusions onto the shelf, and boundary layer mixing around reefs. Such processes provide a mechanism for injection of cool nutrient-rich waters into the reef matrix. The imagery provides a clear picture of a well-organized, but spatially complex, frontal system existing in the southern Coral Sea, which is associated with enhanced commercial and recreational fishing activity in the region. The AVHRR imagery has thus proven to be a valuable tool for spatial mapping of oceanographic features throughout the GBR region, for hypothesis formation in dynamical and modeling studies, and for ship-board reconnaissance operations.