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Study of stalagmites gives insights into past and future climate

Researchers have uncovered clues in stalagmites in a cave just south of the Himalayas that could help better predict Central Pacific El Niño events and monsoons as the planet’s climate changes.

Jessica Oster, assistant professor of Earth and Environmental Sciences at Vanderbilt University, and her research group stumbled upon the findings back in February 2013. They were in Mawmluh Cave in Meghalaya, India, studying seismic activity in the region. While exploring there, they found young stalagmites which had formed in rich, “beautiful” layers over the past 50 to 100 years, Oster said.  They had high concentrations of uranium, an essential element for dating the layers.

The team made a record of the Mawmluh stalagmites to help them decipher average rainfall records from Central Pacific El Niño events, which occur when there is abnormally strong warming in the Central Pacific and cooling in the Eastern and Western Pacific. By looking at the composition of the layers that make up the stalagmites, the team could determine that when El Niño events occurred, the monsoon rainfall was restricted to directly above the cave, leading to a different chemical makeup in the layer. If it was a non-El Niño rainfall, the water would find it’s way in through other avenues, which they could also determine from the layers.

According to Oster and her team, data was consistent with historical information for the area. But one question still remains for the team and for the locals who depend on accurate rainfall predictions.

(Top) The stalagmite in Mawmluh Cave before it was collected. (Bottom) A cross section of the stalagmite showing its layers. (Credit: Jessica Oster)

“What will El Niño do with global warming and the impacts on the monsoon?” Oster said. “Looking at warmer periods in the past, with this information that we have from recent past, could inform our understanding of what might happen in the future.”

Monsoon prediction is critical to agriculture in India, so Oster and her team are hopeful that their research will be helpful for those who are trying to predict changes. They plan to expand on the research in many ways. Oster is currently in Berkeley, California, studying the uranium and thorium samples and has plans to look at different chemicals as well. She wants to look farther back into the past using the samples collected at Mawmluh. They also have to complete their research on earthquakes in the region.

“Having these samples in the first place was surprising and it’s interesting to see where it will take us.”

The research has been funded by the National Science Foundation, the Vanderbilt International Office, the Cave Research Foundation, the Geological Society of America and the Swiss National Science Foundation.



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