Hurricane History Found in Trees

[Madame Butterfly 0]

Hurricane History Found in Trees

Larry O'Hanlon, Discovery News

 

 

Aug. 12, 2005— Pine trees in the southeastern U.S. may have the answer to a question millions are now asking: Are hurricanes becoming more frequent?

 

The isotopic signatures from centuries of hurricanes have been found in the rings of old pine trees near Valdosta, Ga., say researchers at the University of Tennessee in Knoxville.

 

By looking throughout the southeastern U.S. for more trees with similar records, the scientists hope to provide some hard evidence to compare with models that predict more hurricanes due to global warming.

 

 

New Method Predicts Hurricane Season

"What we're trying to do is understand the frequency of hurricanes and how variable they are," said tree ring researcher Claudia Mora of the University of Tennessee. "We're trying to come up with a reliable way to say this."

 

To prove the new approach is reliable, Mora and her team studied the oxygen isotopes locked in the tissues of late-season growth inside of annual growth rings from pine trees near Valdosta, Ga.

 

What they found was a signal from every known hurricane from more than 50 years that dropped rain in the area. Then she pushed the record further.

 

"We've taken it back 100 years and didn't miss a storm," said Mora. She presented her latest findings Thursday at a joint meeting of the Geological Society of America and the Geological Association of Canada in Calgary, Alberta, Canada.

 

Mora's method involved sampling specific seasons from past years within tree rings to extract the isotopic signals of hurricanes. They can do this, said Mora, because hurricanes are already known to be naturally low in oxygen-18.

 

So the rain from hurricanes — which is quickly sucked up by longleaf and slash pine trees after the storm — is distinctly depleted of oxygen-18.

 

That isotopic signature remains locked inside the cellulose of plant cells that grow immediately after a hurricane, she said.

 

But even 100 years is not enough data when you're talking about climate change, said Mora. So she and her team have broadened the area and the ages from which they are gathering hurricane data in the southeastern U.S.

 

Already they have found a record of tropical cyclones spanning 227 years and other clues to climate in that region reaching back to 1450 A.D.

 

"I think they've made a convincing case," said stable isotope biochemist William Anderson of Florida International University.

 

It's research that's extremely timely as well, he said, since there is increasing concern about what global warming is actually doing to hurricanes and other meteorological systems worldwide.

[Yillara Skye 1]

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