PUBLIC LECTURE: Free Seminar: The seas of Papua New Guinea and the Sepik River outflow
|Free Seminar: The seas of Papua New Guinea and the Sepik River outflow : Insights from a voyage on RV Franklin
George Cresswell completed his undergraduate degree at UWA and PhD at the University of Alaska. He spent 1960 at Mawson station Antarctica. The majority of his career was with CSIRO in Sydney and Hobart. He studied the East Australian Current, the Leeuwin Current, and the currents of the seas of New Caledonia, Papua New Guinea and SE Asia. In all, he has collected data while working on ships of eight nations. Other data have come from moored instruments, satellite-tracked drifters and thermal and radar satellite imagery.
In 1997 he ran a voyage on RV Franklin into the seas of Papua New Guinea. It was part a study called TROPICS (Tropical River/Ocean Processes in Coastal Settings) that was the brainchild of, and orchestrated by, AIMS scientist Gregg Brunskill. Since that time George has carried out desktop consultancies covering PNG waters.
In this free public seminar George will discuss the voyage. The instrumentation included the suite on Franklin, two instrument moorings, simple drifters – and NOAA thermal imagery, RADARSAT synthetic aperture radar scenes, and SeaWIFS ocean colour imagery.
The dominant large scale features were: the strong New Guinea Coastal Undercurrent that flows through Vitiaz Strait and then reaches along the coast towards Irian Jaya;
a SE monsoon-driven upwelling plume from SW New Britain that joins Solomon Sea waters to flow through Vitiaz Strait to bathe the offshore islands and the northern PNG coast;
the New Guinea Coastal Current that reverses with the monsoons.
During the Franklin (SE monsoon) survey the surface plume from the Sepik River was only about 2 m thick and it moved offshore ~10 km at 1 m s–1 before being turned to the NW by the underlying currents.
The waters down to several hundred metres in the Sepik study area were comprised of stacks of many mixed layers, with enhanced loads of suspended sediment at the bases of most of them. These subsurface sediment plumes became depleted with increasing distance offshore. Although the tides in the region are small, the moored instruments showed semi-diurnal internal tidal currents to have amplitudes up to 0.15 m s–1 and to be associated with vertical oscillations of perhaps 40-50m.
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