Date:    Wed, 24 Feb 1999 01:29:26 EST
From:    C 
Subject: GL:  Giant ocean eddies discovered

http://www.csiro.au/news/mediarel/mr1999/mr9937.htmlraindisorder.asp CSIRO
Australia
Giant ocean eddies discovered
23 February 1999

Mr Nick Goldie (02) 6276-6478
Mobile (0417) 299-586
Fax (02) 6276-6821
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GIANT OCEAN EDDIES DISCOVERED

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Dramatic ocean eddies larger than Tasmania and a kilometre deep
have been discovered in the Indian Ocean, north-west of
Australia.

Research by Australian and US oceanographers has revealed a
system of turbulent ocean eddies that peel off a major ocean
current flowing across the Indian Ocean towards Africa.

Carrying as much water as 250 Amazon Rivers, the South Equatorial
Current is fed by waters from the northern and southern Indian
Oceans, as well as water flowing from the Pacific Ocean through
the Indonesian archipelago.

"This mixing process alters the characteristics of the ocean in
a region which is a source for rainfall across southern and
western Australia" says Dr Susan Wijffels, Chief Scientist on two
CSIRO research expeditions that identified the changing ocean
conditions.

Dr Wijffels says that an understanding of how the Indonesian
throughflow and the local currents interact should contribute to
improved rainfall predictions for Australia, and a recognition
of El Nino and La Nina features extending into the Indian Ocean.

"This is another feature to take account of in the regional
climate jugsaw puzzle. Yet, it is amazing that such an enormous
natural feature of Australia's oceans has remained undiscovered
until now," she says.

Dr Wijffels says scientists confirmed the ocean features occurred
once a comparison was made using observations taken from the
French/US ocean monitoring satellite TOPEX-Poseidon, 1300
kilometres from the earth's surface.

"The observations came from a sophisticated instrument called a
satellite altimeter which is so sensitive that it can detect
elevation changes of just a few centimetres across thousands of
kilometres of ocean surface.

"Elevations indicate warm water patches that are piled up by the
wind or fed by flow from the Pacific Ocean via the Indonesian
throughflow. But the elevations also indicate the location of
these massive ocean eddies formed at certain times of the year
and which act to mix ocean waters from distinctly different
sources."

Dr Wijffels says the eddies move at two knots and form every two
months when the South Equatorial Current, on its westward journey
across the Indian Ocean, builds up immense power.

"As the flow increases in volume, the current becomes unstable,
particularly from June to December, and eddies simply peel off
and develop a life of their own," says Dr Wijffels.

She explained that eddy formations also occur in other strong
currents around Australia, such as the East Australian Current,
which flows from the Coral Sea to the Tasman Sea. Eddies from
this system are watched closely by fishermen, as well as
competitors in the Sydney to Hobart yacht race, with both groups
interested in sea surface conditions.

Scientists on the research voyages - aboard CSIRO's oceanographic
vessel Franklin and the Scripps Institute of Oceanography Vessel,
Knorr, were taking part in the World Ocean Circulation
Experiment, a project to build a decade-long snapshot of the
world's oceans.

The voyages also aimed to build a profile of the Indonesian
throughflow, an important feature of global climate.

Completing the work with Dr Wijffels have been Dr Nan Bray, Chief
Scientist on the Knorr and now the Chief of CSIRO Marine
Research, and Mr Jackson Chong, also of Scripps Institute of
Oceanography.

More information:

Dr Susan Wijffels - 03-62325450 Craig Macaulay - 03-62325219

Commonwealth Scientific and Industrial Research Organisation
(Australia's largest scientific research organisation)