HIDDEN OCEAN CURRENT A CLIMATE CLUE?
08.23.07 - Leído 67 veces. Enviar esta notaLarry O’Hanlon
Australian climate scientists have located a deep-ocean current in the Tasman Sea that may play a big role in connecting the world’s oceans, and therefore regulating Earth’s climate
COLUMBIA, US; August 21, 2007.- The newfound Tasman Outflow is part of the “super-gyre” ocean current pathway which helps connect the Indian, South Atlantic and South Pacific oceans and is part of the global heat conveyor belt known as the thermohaline circulation. It’s not certain, however, just how big a player the Tasman Outflow is.
“It’s another link between the Pacific and Indian Ocean,” said Ken Ridgway of the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO). “The other is through Indonesia.” Ridgway and his colleagues report on the Tasman Outflow in the August issue of Geophysical Journal Letters.
“What we’ve been really able to show is the pathway and define the very narrow boundary current,” said Ridgway. “It’s these boundary flows that connect everything up.”
Ridgway describes the Tasman Outflow as a current that runs west from Tasmania at a depth of 2,600 to 3,300 feet (800 to 1,000 meters). He also describes the waters south of Tasmania as a “choke-point” in the connections between southern oceans.
In the broader picture in which each ocean contains giant “gyres” of currents, the Tasman Outflow is a small eddy, or spin off, that carries Pacific water from the Coral Sea down the east coast of Australia and then away to the Indian Ocean. It was identified by crunching a large amount of temperature and salinity data collected by ships, buoys and satellites from 1950 to 2002.
Other experts agree that the Tasman Outflow exists, but are not convinced it plays a very significant role globally, primarily because it doesn’t appear to carry that much water or much heat or salinity variation — essential for driving the thermohaline circulation — into the Indian Ocean.
“I think it’s there, but it cannot be very large,” said Arnold Gordon, associate director of Ocean and Climate Physics division at Lamont-Doherty Earth Observatory at Columbia University.
In terms of flow, the current is weak in comparison to others, Gordon added.
He said the Tasman Outflow could not flow at more than three sverdrups — one sverdrup being a million cubic meters of water per second, or about 264 million gallons per second. The Gulf Stream, by comparison, varies from 30 to 15 sverdrups. All the freshwater streams and rivers on Earth come to about one sverdrup, collectively.
“I do not think that’s an important part of the thermohaline circulation,” Gordon told Discovery News.
The bigger, far more important connection between the Pacific and Indian oceans is the three to seven sverdrups which navigate through Indonesia, he said. And since the resources for studying these currents are very limited, he suggested that research would be better focused around Indonesia.
“Inter-ocean exchanges are really important to the climate system,” said Gordon. “We really do need to quantify them. I don’t think the climate modelers are getting it right.”
(Discovery News)
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