COLUMBUS , Ohio -- For the third time in as many years, glaciologistLonnie Thompson has returned from an Andean ice field in Peru withsamples from beds of ancient plants exposed for the first time inperhaps as much as 6,500 years.
In 2002, he first stumbled across some non-fossilized plants exposed bythe steadily retreating Quelccaya ice cap. Carbon dating showed thatplant material was at least 5,000 years old.
Then in 2004, Thompson found additional plant beds revealed by thecontinued retreat of the melting ice and when tested, these proved tobe carbon-free, suggesting that they might date back more than 50,000years. If true, that would suggest that the climate in that region maynot have been as warm as it is today in more than 500 centuries.
In June, he went back to the ice field and found at least 20 new plantcollection sites that had been newly exposed. An analysis of the plantmaterial from these sites suggested that it ranged from 4,500 to 6,500years old.
Some of these sites contained thick, multiple layers of plant materialand soil which might provide a chronology of when in the past this nowhigh, cold, ice-covered locale harbored flourishing wetland bogs, anecosystem requiring much warmer temperatures.
Thompson, a professor of geological sciences and researcher with theByrd Polar Research Center at Ohio State , calls that ice cap the"Rosetta Stone" for climate change.
"Quelccaya is the biggest tropical ice cap on earth and is probably thebest-documented as far as its response to recent climate change," hesaid. "And the retreat of the Qori Kalis glacier that spills offQuelccaya is perhaps the best-studied retreat of any tropical glacier."
He should know. He's led 22 expeditions to this forbidding region since1974, drilling cores through the ice cap that have yielded a detailedclimate history of the region. Frozen areas once surrounding Quelccayanow harbor massive meltwater lakes hundreds of feet deep.
This time, Thompson brought with him two botanists to help identify newdeposits. Blanca Leon, a research fellow from the Herbarium, PlantResources Center , and her colleague Kenneth Young, an associateprofessor of geography, both at the University of Texas at Austin , hadidentified the plant species in samples from Thompson's earlierexpedition.
The plants proved to be alpaca moss, Distichia muscoides, a hardyspecies that still inhabits the region. The researchers also identifiedat least two additional species of moss and grasses that were recentlyuncovered by the ice. The 20 plant samples were sent to both LawrenceLivermore National Laboratories and Woods Hole Oceanographic Institutefor carbon dating.
Having the botanists along allowed the researchers to confirm that theplants had not been moved by the ice, that they actually once grewwhere they were found. "It was important that we confirmed that thesewere original plants on those sites."
Thompson said that the retreating ice was exposing sizeable areascovered by these old plants. "They are perfectly preserved," he said."We could have collected a boxcar full of them."
The plant discoveries are very significant, Thompson says, not so muchbecause of what the plants are but the fact that so many are beingexposed.
Early next year, he plans to return to Tanzania 's Mount Kilimanjaro .In 2001, he predicted that the massive ice field atop that extinctvolcano might disappear within 15 years because of rising temperatures.This time, he intends to look for similar plant deposits that might beexposed as the ice retreats. And when he returns to Peru 's Quelccayaice field next year, he wants to sample more of the exposed beds whosecarbon dates suggest are far older than 5,000 years.
"This story could only have been told by having spent 28 yearscollecting ice cores from around the world, extracting the climaterecords from them, seeing the global trends emerge and having theopportunity to be there now as the ice released its treasures,"Thompson said.
His research is supported by the National Science Foundation, theNational Aeronautics and Space Administration and the National Oceanicand Atmospheric Administration.
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