Predicting Long-term Currents in the Great Barrier Reef

Long-term records of continental shelf currents are needed in the Great Barrier Reef region for addressing major ecological problems and for assessing offshore engineering projects. Since current meter observations longer than one year are virtually non existent, a capability to simulate currents over multi-year time scales is desirable. A suite of linear systems models has therefore been developed and used to predict low-frequency along-shelf current in the central Great Barrier Reef region over 25 years. The models, which combine optimally-lagged regression analysis with knowledge of regional hydrodynamics are driven by readily available wind, atmospheric pressure and sea level records. A model based on across-shelf geostrophic balance, which accounts for sea level variations at the coast and in the adjoining Coral Sea, predicts low frequency along-shelf currents with a maximum bias of 3.5 cm {-1} and standard error of 10 cm {-1}. Predicted currents for the period 1966-1990 have been used in simulating Crown of Thorns Starfish outbreaks, to set boundary conditions for numerical hydro-dynamic models, and for analysing long-term current statistics. Predicted tidal currents can be linearly superimposed on the low-frequency flows to produce estimates of total current. Possible extensions include provision of a real-time 'now casting' mode, and modelling of surface and bottom boundary layer flows.