Linear systems analysis of momentum on the continental shelf and slope of the central Great Barrier Reef

Abstract

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.