http://www.news.com.au/story/0,23599,21379283-2,00.html A MASSIVE, mysterious whirlpool of cold water has developed off the coast of Sydney, forcing the sea surface to fall almost 1m and ocean currents to change course.
Dubbed a sea "monster" by CSIRO oceanographers, the huge body of water stretches almost 200km across and plunges 1000m towards the ocean floor. Its centre sits just 100km off the coast of Sydney and could stay there for months.
Scientists are baffled by the powerful cold-water eddy, which is invisible to the human eye but can be tracked through satellite images.
At its centre the sea level has dropped by 70cm, while the water 400m below the surface is 6C colder than normal at that depth.
The East Australian Current has been forced to divert around the eddy, which takes one week to do a full rotation in a clockwise direction. A second eddy of similar proportions is sitting further out from the coast.
CSIRO satellite oceanographer Dr David Griffin said fishers passing through the eddies in their boats would not feel the slow whirlpools.
However, they would notice a line of debris forming at the edges.
Beachgoers can feel the effects of the whirlpool closer to shore as it forces water from the ocean depths up over the continental shelf.
The cooler water can bring down the temperature at Sydney's beaches by several degrees.
Oceanographers noticed the eddy forming in January.
Dr Griffin said it contributed to the surprisingly cool sea temperatures – down to a numbing 14C – swimmers felt at their favourite spots this summer.
"To break a (temperature) record like that you need a bunch of things to happen," Dr Griffin said.
But fish and other marine life felt the changes most, he said. Some would be attracted to the cooler water and others would shy away.
Experts are unsure how long the two whirlpools will sit off Australia's east coast, or how they will affect marine ecosystems.
"The eddies in this part of the world are very hard to predict," Dr Griffin said.
They naturally drift westwards but keep bumping up against the shore and may be re-energised by other tidal and weather patterns, he said.
The whirlpool will today be discussed in Hobart at a meeting of 200 Australian, European and US scientists working with satellite images to map water temperatures.