Reuters News Service, Aug. 15, 2007
SYDNEY (Reuters) - Australian scientists have discovered a giant underwater current that is one of the last missing links of a system that connects the world's oceans and helps govern global climate.
New research shows that a current sweeping past
The Southern Ocean, which swirls around
"We knew that they (deep ocean pathway currents) could move from the Pacific to the Indian Ocean through
In each ocean, water flows around anticlockwise pathways, or gyres, the size of ocean basins.
The newly discovered Tasman Outflow, which sweeps past Tasmania at an average depth of 800-1,000 meters (2,600 to 3,300 feet), is classed as a "supergyre" that links the Indian, Pacific and Atlantic southern hemisphere ocean basins, the government-backed CSIRO said in a statement on Wednesday.
The CSIRO team analyzed thousands of temperature and salinity data samples collected between 1950 and 2002 by research ships, robotic ocean monitors and satellites between 60 degrees south, just north of the
"They identified linkages between these gyres to form a global-scale 'supergyre' that transfers water to all three ocean basins," the CSIRO said.
Ridgway and co-author Jeff Dunn said identification of the supergyre improves the ability of researchers to more accurately explain how the ocean governs global climate.
"Recognizing the scales and patterns of these subsurface water masses means they can be incorporated into the powerful models used by scientists to project how climate may change," Ridgway said in a statement.
The best known of the global ocean currents is the North Atlantic loop of the Great Ocean Conveyer, which brings warm water from the Equator to waters off northern
Earlier this year, another CSIRO scientist said global warming was already having an impact on the vast Southern Ocean, posing a threat to myriad ocean currents that distribute heat around the world.
Melting ice-sheets and glaciers in Antarctica are releasing fresh water, interfering with the formation of dense "bottom water", which sinks 4-5 kilometers to the ocean floor and helps drive the world's ocean circulation system.
A slowdown in the system known as "overturning circulation" would affect the way the ocean, which absorbs 85 percent of atmospheric heat, carries heat around the globe, Steve Rintoul, a senior scientist at the CSIRO Division of Marine and Atmospheric Research, said in March.
© Reuters 2006. All rights reserved.
Hidden Ocean Current a Climate Clue?
Discovery.com, Aug. 21, 2007
Australian climate scientists have located a deep-ocean current in the
The newfound Tasman Outflow is part of the "super-gyre" ocean current pathway which helps connect the Indian,
"It's another link between the Pacific and
"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
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
"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
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
"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
"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."