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Australian Academy of Science, Becker House, Canberra. Friday 16 December 1994
To a large extent, I am going to leave you to imagine how these currents will impact on fluxes in the coastal zone; but I will just show you one classic example of the impact of the East Australian Current. The example is the coccolithophorid bloom that occurred in Jervis Bay two years ago. This (Overhead 5, from Blackburn and Cresswell, Australian Journal of Marine and Freshwater Research, vol. 44, pp 253-260) is an aerial photograph of the algal bloom. The hypothesis for this bloom is that both the algae and the nutrients to sustain them were brought into the bay by an eddy that encroached on the coastline, an eddy from the East Australian Current.
I have already shown you some of the data that we use to interpret the current systems along the Australian coastline: that is, satellite data. We have a wealth of other information and I will go very quickly through some of this. This part of the talk is a very unashamed advertisement for the Division of Oceanography which has been working all round Australia's coasts for a number of decades now.Overhead 6
This spaghetti diagram (Overhead 6) shows drifter tracks. You will not be able to distinguish any particular track, but you do get an indication of just how many satellite-tracked drifters have been deployed over the years, in particular focusing on the western and eastern coastal current systems. These tracks are very graphic but, of course, only provide currents at a particular time and at the particular depth of the drifter drogue.
We have our research vessel, the RV "Franklin", which is on the move around Australian coastal waters. These (Overhead 7) are the cruise tracks from 1985 when the vessel was launched through until early 1995. You can see we have achieved quite extensive coverage of Australia's coastal waters and beyond. As the ship is steaming about doing its tasks -- like putting in moorings, taking bottle samples and so on -- it is also continuously recording currents down to 400 metres and surface temperatures and salinity. So there is an large data source associated just with the operation of the vessel.
We have a rather daunting set of hydrology stations (Overhead 8) - locations at which profiles of temperature and salinity have been measured down through the water column either by chemical or electronic means. The oldest hydrology station here actually dates back to 1906. This is a very valuable data set but, again, it suffers because most of these points are only collected once. As you saw from the satellite images, we are working with a coastal current system that is highly variable in time. A single measurement at a single time may not always be very informative.
Another source of sub-surface information that we have is our volunteer observer network set up as part of TOGA, the Tropical Ocean and Global Atmosphere program. These (Overhead 9) are the lines that the Division of Oceanography runs, along which expendable temperature profilers are released from merchant ships. These are repeating ship routes, so that we receive temporal information as well as spatial information. You can see we have now built up, since 1983, an extensive data base of upper ocean temperatures.