Data acquired during a winter (May) cruise of the RV Franklin to the southern Great Barrier Reef
indicate that the dynamics of the shelf/slope region are governed by the tides, the poleward-flowing
East Australian Current (EAC), and the complex topography. Over the Marion Plateau in water deeper
than - 100 m, the EAC appears to drive a slow clockwise circulation. Tides appear to be primarily
responsible for shelf/slope currents in the upper layers, with evidence of nutrient uplift from the upper
slope to the outer shelf proper in the Capricorn Channel. Elsewhere, the bottom Ekrnan flux of the
strongly poleward-flowing EAC enhances the sloping isotherms associated with the longshore geostrophic
balance, pumping nutrient-rich waters from depth to the upper continental slope. Generally, shelf
waters are cooler than oceanic waters as a consequence of surface heat loss by radiation. A combination
of heat loss and evaporation from waters flowing in the shallows of the Great Sandy Strait appears to
result in denser 'winter mangrove waters' exporting low-oxygen, high-nutrient waters onto the shelf both
north and south of Fraser Island; these subsequently mix with shelf waters and finally flow offshore
at - 100 m depth, just above the salinity-maximum layer, causing anomalous nutrient values in the
region of Fraser Island.
The Stable Oxygen Isotope Signal in Shallow-Water, Upper-Slope Sediments off the Great Barrier Reef (Hole 820A)