March
13, 2007
COLD-WATER
EDDY 'MONSTERS' MIGHTY CURRENT OFF SYDNEY
“What
we do know
is that this is a very powerful natural feature which tends to push
everything
else aside – even the mighty East Australian
Current,” says CSIRO’s Dr. David
Griffin.
Dr.
Griffin,
from the Wealth from Oceans Flagship Research program, said cold-water
eddies
regularly appear off Sydney.
“Until
20 years
ago we would not have known they even existed without accidentally
steaming
through them on a research vessel,” he said.
“However,
now
that we can routinely identify them from space via satellite, marine
scientists
can evaluate their role as a source of life in the marine
ecosystem.”
Reaching
to a
depth of more than 1000 meters, the 200 kilometers diameter ocean eddy
has a
rotational period of about seven days. Its center is about 100
kilometers
directly offshore from Sydney.
Ocean
eddies can
have a life of 2-3 weeks although similar eddies identified off South
Australia
and Western Australia are known to have survived several months.
In
a complex
cause-and-effect relationship, the East Australian Current is being
forced to
take a wide detour around the eddy off Sydney
instead of flowing along the edge of the continental shelf.
In
its center,
cold water from 400 meters is raised upwards some 200 meters. The sea
surface,
conversely, is lowered by 70 centimeters. This dip in the surface of
the ocean
is invisible to the eye, but it can be accurately measured by the
European and U.S.
satellites
Jason-1, Envisat and GFO
orbiting the Earth.
The
upward
displacement of the water was recorded by a robotic Argo float deployed
by
CSIRO as part of the international Argo program.
The
cold-water
eddy phenomena will be one of a wide range of issues to be discussed
during a
meeting which began in Hobart today of nearly 200 European, U.S. and
Australian
scientists working with satellite altimetry – instruments
that measure the
height of the ocean to detect cold and warm water.
##
Contact:
Craig
Macaulay
CSIRO Australia
036-232-5219
craig.macaulay@csiro.au
This text derived from:
http://www.csiro.au/
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