Feb. 1, 2007 • Volume 15 Number 10

"The evidence is overwhelming. There's no question that the Earth is warming and we're having a role in it." - Asst. Prof. Amy Frappier (Geology and Geophysics)

Warming to the Task

BC geologist Amy Frappier looks to the past to find answers about climate's future

By Stephen Gawlik
Staff Writer

When it comes to the weather, Asst. Prof. Amy Frappier (Geology and Geophysics) tends to have a different perspective.

While most people concern themselves with what the weather is going to do on a daily basis, Frappier, a paleoclimatologist, is far more interested in what the weather did - thousands of years ago.

"We have only a relatively short recorded history, but we can take a look back at old clues and try to use them to see what's coming," said Frappier, who joined the Boston College faculty last semester after completing her doctorate at the University of New Hampshire.

As a public debate about global warming continues and the chorus demanding legislative, political and industrial changes reaches a crescendo, it is researchers like Frappier who are working to provide empirical guidance about the planet's always-shifting climate.

"The evidence is overwhelming," she said. "The globe is warming and we want to know what to expect so we can be prepared."

For her part, the Rhode Island native is one of a small but growing contingent of scientists in her field - paleotempestology, the study of ancient storms - who are seeking clues about the history of Earth's changing climate as found in certain natural "archives" such as tree rings, sea shells, polar ice cores and other places.

Frappier is credited with developing a method for decoding the record of hurricane rainfall preserved in tropical cave formations such as stalagmites. The details of Frappier's methodology and its results will appear in a paper published in this month's issue of Geology.

Frappier, who spent an undergraduate semester while at the University of Maine living in Antarctica, sees undeniable evidence of climate change both in her many research trips to the Caribbean - and also right here at home in New England.

"There's no question that the Earth is warming and we're having a role in it," says Frappier.

An avid cross-country skier - "I think this has been a tough year for all of us who enjoy winter sports," she says - Frappier says there is ample firsthand evidence that things aren't what they used to be as far as the New England weather patterns are concerned.

"Look at how many small ski slopes have closed and look at how much artificial snow the big ones have to produce," she said. "That was unheard of 50 years ago.

"There are more heat waves in summertime and we're seeing a change in the growing season, the last frost comes earlier in spring, and the first frost is later in the fall."

Frappier's research, however, is focused on the tropics because those regions are home to most of the world's population, and are most likely to be sharply affected by whatever climate changes are happening.

"I am exploring new Caribbean cave records of pre-historic hurricane activity to illuminate how global climate change is likely to affect hurricanes and vulnerable coastal populations in the future," said Frappier. The more traditional method of this research, she explains, involved digging sediment cores from coastal lagoons and marshes. Stalagmites, she said, offer a different and more detailed "story set in stone."

Stalagmites are mineral formations that grow up from the floor of caves as mineral-rich water drips from the cave ceiling. All cave formations are created slowly over time, at rates that vary from an inch in 1,000 years to as fast as an inch in 20 years. A change in the isotopic character of oxygen in rainfall from hurricanes alters the chemical composition of the water descending through the rock into the cave, says Frappier. These changes are recorded as variations in the oxygen isotope values in the stalagmite's calcium carbonate composition. Stalagmites contain visible growth bands that can be counted like tree rings and, using a computer-controlled dental drill to collect samples, researchers can tell when in the past the region experienced hurricane rains. .

The number and intensity of hurricanes in the region will tell researchers something about the links between climate and storms, she says.

"Changes in the water that came through the cave result in really brief variations which we can mathematically distinguish from the rest of the record," Frappier says. "We have cross-checked this with historical storms and the correspondence is remarkable."

Frappier began following this line of inquiry while in graduate school as she came upon a research article that discussed the isotopic differences in rains caused by hurricanes. At the same time, she met another graduate student who was studying caves in Belize to ascertain what sort of climate the Mayan people experienced at the height and decline of their civilization. Frappier put the two pieces together and developed the methodology for indicating exactly when and with what intensity hurricanes appeared since the last Ice Age.

"I figured either this was impossible, or someone was doing it already," she said, noting that others had attempted this research many years ago, but didn't have the technology required to detect individual storms. That all has now changed, she said.

For Frappier, the interplay between humans and nature has been a life-long interest. As an elementary school student in northwestern Rhode Island, she witnessed a dispute between people who wanted to preserve local wetlands and a city that wanted to build a sewer in an area behind her home.

"The whole idea of how people live in the environment while protecting it became an interesting dynamic to me for a very long time," she said.

As the conservation-versus-development debate continues to take center stage internationally, Frappier says it is more vital than ever before to make sound environmental decisions.

"The choices we all make in the next decade are going to be very important in determining the climate our children inherit," she said.

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