Chinese Ice Cap May Reveal Clues To Earth's Climate
Published on July 02, 1991
COLUMBUS, Ohio -- Scientists returning last week from an expedition to a Chinese ice cap called the "Roof of the World" believe they have found a record of ancient climate dating back 100,000 years.
If that is so, it will be the best climate record found in non-polar ice cores to date and might provide a key piece to the puzzle of just how the earth's weather varies over time.
The team failed to find obvious evidence of oil soot particles produced by burning Kuwaiti oil fields. The 22,000-foot thick Guliya ice cap is some 4,000 miles east and downwind of Kuwait and some experts had speculated that high concentrations of smoke and soot in the air could cause regional cooling on the high Tibetan plateau.
During this, the second year of a planned four-year cooperative program between U.S. and Chinese researchers, the team found more evidence that the last few decades have been the warmest since the last ice age.
Preliminary data from the Guliya ice cap work -- and similar initial investigations on the Gregoriev ice cap in the U.S.S.R. -- seem to match results from earlier records recovered from the Dunde ice cap in eastern Tibet.
In 1989, expedition leader Lonnie Thompson, a research scientist at the Byrd Polar Research Center at Ohio State University, reported finding evidence of this warming trend in cores he drilled from the Dunde ice cap in the Quilan Shan Mountains that border the Gobi Desert.
In 1990, Thompson and his colleagues surveyed both the Guliya and Gregoriev ice caps, digging snow pits and gauging the ice caps' potential to provide lengthy climate records. Their return to the Guliya this year netted three short ice cores that will be analyzed in the coming months.
"Our data suggests a strong warming trend over the last 10 years based on the snow pit work and shallow ice cores," Thompson said, "and that is consistent over a wide area of Asia."
The Guliya ice cap in far western China is the largest ice body in the sub-tropic regions, an area bordered by 60 degrees north latitude and 60 degrees south latitude. It covers more than 3,000 square miles -- three times the size of the state of Rhode Island -- and is 300 feet thicker than the Dunde ice cap.
Thompson said that ice temperatures were considerably colder than those in other sub-tropical ice caps and equaled those of the Antarctic peninsula and southern Greenland.
"This means that the percentage of carbon dioxide gas trapped in the ice should be measurable," he said, adding that this could offer insight into the prevailing temperatures at the time the ice was formed from snowfall. Researchers will measure oxygen isotope ratios, microparticle concentrations, pollen content, conductivity and other indicators of past climate conditions.
The team drilled three short cores while at the ice cap. One, measuring nearly 100 feet, was kept frozen. It should represent about 40 to 50 years of accumulation. A second core, this one 53 feet long, was sliced into small sections which were then bagged and melted to produce water samples. Both are awaiting analysis at Ohio State.
The third core, a 66-foot frozen length of ice, will accompany Yao Tandong, a former post-doctoral researcher at the Byrd Center and one of Thompson's colleagues, when he returns to Ohio State later this year.
The team plans to return to the Guliya next season to drill through the ice to the bedrock on which it rests. That would produce an ice core 1,155 feet long and weighing more than five tons. With luck, Thompson said, that core should provide a solid climate record back at least 100,000 years.
The remote Tibetan plateau ice fields are believed by many researchers to be the most likely place where evidence of global warming trends would appear. Because of that, Thompson and his colleagues wanted to investigate reports that snow and ice on the outer margins of the Guliya ice cap were being darkened by smoke and soot from Kuwaiti oil field fires.
"We did see a few patches of grayer snow but's there's no reason to assume that it was caused by oil," Thompson said, adding that samples of the gray snow will be analyzed soon.
"It's more likely that the gray coloring was caused by normal rock dust and that the impact of oil soot -- if any -- on the ice would be relatively small compared to normal dust contamination.
"The volcanoes in the Philippines and Japan may actually have a greater impact on global weather patterns than the oil fires in Kuwait since the fires and their smoke are a rather low-level phenomenon," Thompson explained.
This fits nicely with findings announced last week by teams of scientists flying through smoke clouds in the Gulf region. Their tentative results suggested little or no global effect from the oil field fires.
The Gregoriev, Guliya and Dunde ice caps lie along a line stretching some 2,000 miles across the Soviet Union and China.
In addition to Thompson, Ohio State researchers Gino Cassasa, Jim Greenberg and Mary Davis were part of the expedition. They were joined by about a dozen colleagues from the Chinese Lanzhou Institute of Glaciology and Geocryology.
The program was supported jointly by the National Science Foundation, the National Geographic Society, Ohio State University and Academia Sinica (the Chinese academy of science).#
Contact: Lonnie G. Thompson, (614) 292-6531 Written by Earle Holland, (614) 292-8384