DURHAM, N.H. -- It was just another normal day in the lab for Amy Frappier, a
graduate student in Earth science at the University of New Hampshire, who was
investigating the composition of a cave stalagmite from the Cave of the Stone Tomb
in Belize. Little did she know that she was about to come across evidence about a
surprising new effect of El Ni?o on the carbon cycle.
This unexpected discovery, documented in the Oct. 18 issue of the journal Science, contributes to scientific knowledge of how carbon dioxide moves in and out of the atmosphere, a key to understanding global warming.
The discovery was made when Frappier noticed a jump in carbon isotopes during an El Ni?o year. Upon later inspection, the entire graph for carbon matched up with historic records of El Ni?o events.
"The data from the stalagmite shows a significant effect of El Ni?o on the carbon cycle. The effect is so large that it is almost as if a forest had turned into a grassland and then back again into a forest in just one year," says Dork Sahagian, Frappier's advisor and professor at UNH's Institute for the Study of Earth, Oceans, and Space. "This was a very curious discovery."
Explains Frappier, who was initially looking for signals of only hurricanes captured in the stalagmite, "Belize is about the last place you would look for El Ni?o data because during recent El Ni?o events, central Belize experienced no major changes in temperature or rainfall. Despite the lack of typical weather changes, the stalagmite data shows that the ecosystem responded in a big way. Our findings indicate that El Ni?os may actually be affecting a larger area than we had recognized before, and that ecosystems may be more sensitive to El Ni?o events than previously thought."
Aided by new microsampling techniques developed by collaborators at the University of Iowa, Frappier and Sahagian, principal investigator of this study, were among the first to study stalagmites for historic records of extreme weather events. The investigators suspect that the response to El Ni?o probably came from the amount of carbon dioxide being released into the atmosphere or soil, by plant roots, soil microbes, or tree leaves.
This research was partially funded by the National Science Foundation.
"Scientists are still looking at how changes in ecosystems are related to changes in the climate system," says Frappier, explaining that most detailed prehistoric records of atmospheric carbon come from air bubbles trapped in glacier ice taken from the polar regions."
"Before now, there wasn't a good way to see how ecosystem carbon-cycling had changed over time in the Tropics," she says. "Our work shows that stalagmites can capture very detailed records of such changes in tropical forests. Stalagmites could be the 'ice core' of the Tropics."
By Amy Seif
Communication and Information Coordinator
Institute for the Study of Earth, Oceans, and Space