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The sinking of an Australian coastal trader, the Blyth Star, off Southern Tasmania in early October 22 years ago sparked what then became Australia's most expensive maritime air and sea search.
For eight days the crew of the 320 tonne vessel drifted in an inflatable life raft for 800 kilometres around the Tasmanian coastline - unsighted from the air yet always within sight of land, at times so close they could even hold on to kelp.
Poorly clad for the conditions, their situation was exacerbated by the fact maritime safety authorities had been given no indication which route - via the east or west coasts - the vessel was taking from Hobart to Melbourne.
The tragedy occurred when, according to the ensuing marine inquiry, a probable operational error in the engine room led to ballast water being pumped out, with the result that the vessel heeled to starboard and the poop, engine room and possibly the hold, flooded.
It cost the lives of three men during the next 12 days, including the death of two of the crew after they had succeeded in reaching shore at Deep Glen Bay on the Forestier Peninsula, only to be confronted by cliffs and thick bush delaying their quest for safety.
However, had the sinking occurred even just a few weeks later all aboard that inflatable life raft would have been swept down into the Southern Ocean, by the converging tail of Australia's two most influential ocean currents.
Since the sinking, by using satellite-recordings from ocean drift buoys, CSIRO Oceanography scientists studying Australia's ocean currents have identified winter and summer current patterns around the Tasmanian coastline.
Oceanographers, led by Dr Peter Craig and working in consultation with the Bureau of Meteorology and the Australian Maritime Safety Authority, believe such map information could be available to shipping companies and mariners within two years.
When the Blyth Star sank on the morning of October 13, the current was in a winter pattern - the final influences of the Leeuwin Current off the West Australian coast continuing across the Australian Bight and running down the Tasmanian West Coast, where it is known as the Zeehan Current.
Under the winter pattern the Zeehan Current then rounds southern Tasmania, moving up the east coast towards the Freycinet Peninsula, before joining the remaining influence of the East Australian Current and diverting into the Tasman Sea.
Under a summer pattern, both currents converge off southern Tasmania before moving into the Southern Ocean. This piece of the ocean's currents and eddies jigsaw has emerged from a study by CSIRO Oceanography scientists, of an ocean area in Australia's recently declared Exclusive Economic Zone (EEZ). Declaration of the EEZ has given the Federal Government authority over more than 14 million square kilometres of marine territory.
Within the last year new satellite technology has provided oceanographers with real-time pictures. In effect, these are weather charts of the ocean currents and eddies off Australia's coast and are more reliable than previous satellite based maps. Previous maps were produced by measuring sea surface temperatures from which scientists calculated the patterns and directions of currents and eddies.
The latest satellite, the TOPEX/POSEIDON, measures the height of the sea surface, using on-board radar altimeters. Adding this to information from tracking drift buoys and satellite read sea surface temperatures, scientists believe they are now able to predict current and ocean movement in greater detail. This detail shows up unpredictable eddies, which can carry buoys (and boats) hundreds of kilometres at considerable speeds of up to three knots.
The satellite, 1,340 kilometres about the earth's surface, can record sea surface height to within 5 cm accuracy.
The development of real-time maps is the work of Drs Stuart Godfrey, Ken Ridgway and Chris Aiken, all of CSIRO Oceanography, Hobart.
Another member of the Oceanography team, Dr George Cresswell, has provided pre-race briefings for the Sydney-Hobart yacht race. His briefs on the East Australia Current, based on information from previous oceanographic technology, served the competitors well. The latest computer models, developed on satellite sea surface temperature and wave height information, now confirm the current and eddy activity that George Cresswell forecast, but to greater detail.
A decade after the sinking - and addressing a seminar on Survival At Sea at the Australian Maritime College, Launceston in 1983, - Blyth Star crew member, Michael Doleman provided a valuable insight when he reflected -
"During our eight days adrift, we travelled an enormous distance at the mercy of the tides and currents."
"From the scene of the sinking at South West Cape, we drifted south down past Maatsuyker Island to what we thought would be a cold death in the Antarctic only to drift back again towards the coast, drifting north east all the way up to Schouten Island (off Freycinet Peninsula)...
(They were then) ... "drifting back down past Maria Island to Tasman Island then drifting back up past Fortescue Bay, Eaglehawk Neck and eventually coming ashore at Deep Glen Bay," he said.
By Doleman's calculation, the distance of drift was around 800 kilometres, including three days in the vicinity of Tasman Island before the Forestier Peninsula landing.
Dr Cresswell says that patterns of behaviour of satellite tracking drift buoys around Tasmania highlights how lucky the survivors were to not end up in the Southern Ocean.
"Within just a few weeks, current patterns would have changed and had them shooting off to Antarctica, instead of following the Tasmanian coast."
"Because of the studies of drifting buoys since the Blyth Star sinking we are much better off in terms of the information. We need, however, to do considerably more to be able to present a relatively detailed picture of current patterns for fishermen and sailors working in Tasmanian waters," he said.
The new mapping techniques promise to be powerful tools in future search and rescue operations, as well as in other marine applications in the EEZ.
For further information please contact:
Craig Macaulay
Drs Peter Craig and Stuart Godfrey will be available for interview.
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