AP-Dow Jones News Service April 10, 1997
SYDNEY (AP)--Rising temperatures in the ocean depths off Antarctica provide new evidence that pollution and gas emissions from the Industrial Age are causing global warming, researchers said Thursday.
Carbon dioxide from burning fossil fuels and other gas emissions from industry have built up for more than a century and trap heat in the atmosphere, said Professor Bill Budd of the Antarctic Cooperative Research Center.
Most measurements of global warming have been made at or near the Earth's surface, and though they show a general trend toward warming, there is also wide local inconsistency in measurements, he said.
But new data from deep ocean probes in the Southern Ocean, Indian Ocean, and South Pacific show the same warming trend.
'The deep changes have occurred in waters which originate from surface waters in the Southern Ocean,' said Dr. Nathan Bindoff, also from the Antarctic Research Center, based in Hobart, Tasmania.
'These surface waters sink and are carried northward by the ocean currents into the Indian and Southern Pacific Oceans where the observations were taken. The Southern Ocean is an important source of deep water and is one of the keys to understanding global climate change,' he said.
Indian Ocean waters they tested down to 900 meters have warmed up to 0.5 degrees Celsius between 1962 and 1987, based on comparison of measurements, Bindoff said.
The Indian Ocean has risen by 3.5 centimeters in those 25 years just from thermal expansion.
If this warming were being driven by the 'greenhouse gas effect' of heat trapped in the Earth's atmosphere, Budd said, you would also expect a dilution of the salty oceans in southern latitudes approaching Antarctica. That is because a warmer atmosphere holds more moisture, and drops more rain and snow to mix with the oceans.
Bindoff's research found exactly that - waters of the Indian Ocean between 500 and 1,500 meters deep 'contain more fresh water than in the past.
'By comparing the salinity pattern of the surface waters with the pattern of deep water salinity, this extra fresh water has been found to come from surface waters in the Southern Ocean,' Bindoff said.
This discovery validated computer models that predicted increased precipitation near Antarctica from manmade global warming.
It also added more weight to Antarctic studies which found in 1995 that about 40% more snow is falling on the Lambert Glacier than is being drained away, amounting to about 1.2 centimeters in extra depth.
That effect was ascribed to global warming, but researchers were unsure whether it was manmade or part of a longer-term climatic trend toward warming after the last Ice Age.
More deepsea temperature measurements will be taken from instruments brought into Hobart this week by the Melville, a research ship from the Scripps Institute of Oceanography in San Diego, California.
The ship recovered 50 deepsea probes from the Southern Ocean as part of a US$1 billion multi-year study.
They measured temperature, current flow and movement for two years at depths of up to four kilometers. It is all part of the World Ocean Circulation Experiment, a study sponsored by the U.S. National Science Foundation, Australia's federal science agency, and science agencies from 23 other nations.
The data from the probes will be compared with satellite measurements and other information collected over the last six years of studying the Antarctic circumpolar current, which has a volume of water equal to 150 times that of all the world's rivers.
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