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Clues to Climate Change History

Posted on March 15th, 2015

by Brittany Borghi, Iowa Now

IIHR researcher Tim Mattes is part of a team analyzing sediment samples from a lake high in the Andean mountains of Chile.

IIHR researcher Tim Mattes is part of a team analyzing sediment samples from a lake high in the Andean mountains of Chile.

IIHR Associate Research Engineer Tim Mattes is part of a research team that has found clues to Earth’s climate change history in a Chilean lake. The team is studying sediment samples from the lake in hopes of learning more about the Younger Dryas, a 1,300-year-long cold snap and drought that happened about 12,800 years ago. Mattes is able to pull DNA out of the sediment to analyze how organisms living in the lake changed throughout the Younger Dryas.

Associate Professor of Earth and Environmental Sciences Ingrid Ukstins Peate has been studying the bright red waters of Aguas Calientes in northeast Chile, one of the highest lakes in the world, for almost a decade. Ukstins Peate—along with Sam Saltzman, an MS student in geoscience, and Brennan van Alderwerelt, a doctoral student in volcanology and igneous petrology—spent two weeks at Laguna Lejía in October 2014. The trio was armed and ready to study the leftovers from one of the most significant climate change events in Earth’s recent history.

The Younger Dryas was a 1,300-year-long cold snap and drought about 12,800 years ago. The change was swift and abrupt: temperatures in the Northern Hemisphere plunged from present-day levels down to a glacial state. As the Younger Dryas ended about 11,500 years ago, temperatures rose sharply—in Greenland, about 10° C (18° F) in a decade. While there are good records of the period’s impact on the Northern Hemisphere, little is known about what happened in the Southern Hemisphere. Ukstins Peate is hopeful that Laguna Lejía holds the clues.

“There are lake records all over the planet, but it’s very hard to find that kind of consistent record in the Andes with all the active volcanism and tectonics that happen there. There aren’t a lot of sequences like this that are preserved for South America for that time frame,” Ukstins Peate says.

A close-up view of a sedimentary sample from a high-altitude lake in Chile. Image courtesy of Ingrid Ukstins Peate.

A close-up view of a sedimentary sample from a high-altitude lake in Chile. Image courtesy of Ingrid Ukstins Peate.

The sediments were deposited when the lake’s water level was at its highest and later during the Younger Dryas period. As the climate warmed and water levels receded, the sediment layers were exposed. Ukstins Peate and her research team took core samples of the layers and shipped them to the University of Iowa. Researchers are now analyzing how the composition of the rocks and the organisms living around them changed.

“If you can sample them at a high resolution, you can track what the lake was doing over time as it was drying up,” Ukstins Peate says.

IIHR Associate Research Engineer Tim Mattes (also associate professor of civil and environmental engineering), can pull DNA out of the sediment to determine how organisms in the lake changed throughout the Younger Dryas. Meanwhile, Ukstins Peate’s team determines composition, mineral content, and temperature information, showing how the structure of the land around the lake changed as temperatures dropped.

“We can actually track the changes in the ecosystem in the lake, as well, and that’s a really powerful thing to do,” Ukstins Peate says.

That research not only serves to fill in the understanding of the Younger Dryas’ impact on the Southern Hemisphere, but also how the entire planet may react to climate change in the future.

A third UI researcher, Scott Spak, will enter the chemical and ecological data into his global climate models to get a better idea of the integrated global reaction. If the researchers can understand how specific regions of the Earth are impacted when the climate changes and how the changes in those regions impact other parts of the globe, they can make better predictions of how the planet will respond to future climate change events.

“We can use the magnitude of response for this event to try to compare to what we see as the different magnitudes of response today for an event that we don’t know the end result of in the future,” Ukstins Peate says.

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