LINEAR-SYSTEMS ANALYSIS OF MOMENTUM ON THE CONTINENTAL-SHELF AND SLOPE OF THE CENTRAL GREAT-BARRIER-REEF

Current meter records from a mooring transect deployed across the continental shelf and slope of the central Great Barrier Reef, Australia during 1985 have been analyzed in a study of the subtidal momentum balance. In the 3-20 day wave band, a single-input linear systems model of the subtidal along-shelf flow, driven by across-shelf pressure gradient (i.e., assuming semi-geostrophic balance), explained over 70% of the variance on the shelf, but only 30% at the shelf break and upper slope. A two-input model driven by along-shelf horizontal pressure gradient and wind stress, and incorporating along-shelf acceleration and bottom stress, explained approximately 60% of the variance on both the shelf and upper slope. The model responses evidently combine local wind-driven circulation and freely-propagating continental shelf waves. Linear resistance coefficients estimated from the two-input model averaged 0.07 cm s-1, but were higher (0.09) within the reef matrix and lower (0.06) near the coast.