Northwestern University graduate students dive into the past to understand current climate change

Aidan Burdick, third-year Ph.D. candidate in the Department of Earth and Planetary Sciences, examines the sediment core sample he acquired from Crystal Lake, Illinois.
Aidan Burdick, third-year Ph.D. candidate in the Department of Earth and Planetary Sciences, examines the sediment core sample he acquired from Crystal Lake, Illinois.

Photo Courtesy of Ava Hoelscher

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By Ava Hoelscher

Thick winter socks: check. Thermal underwear: check. Non-perishable food: check. Bear spray: check. Industrial-sized pipe: check. Bailey Nash’s packing list for her upcoming trip looks a little different as she pursues her travels as a climate science detective. 

Nash, a third-year Ph.D. candidate in Northwestern University’s Department of Earth and Planetary Sciences, will travel to southern Greenland this summer with a team of other researchers to collect sediment cores from lake beds that offer a window into the past of climate cues.

“Basically what we do is show up to the lake, fill this big raft, float into the middle of the lake, shove what’s essentially a plumbing pipe down into the bottom of the lake, and then we pull it up,” Nash said.

The research team returns to Professor Yarrow Axford’s Quaternary Sediment Laboratory on campus where Nash works with Axford, her Ph.D. adviser, to understand climate change by analyzing components in the mud samples accrued over thousands of years.

Bailey Nash, third-year Ph.D. candidate in the Department of Earth and Planetary Sciences, gestures energetically as she breaks down the sediment core gathering process. (Photo Courtesy of Ava Hoelscher)

Students in Axford’s lab operate under a paleolimnology focus, according to Nash, which is the study of lakes throughout the past. Nash said the goal is to use the story of lakes changing over time to paint a bigger picture of how the earth’s climate has changed.

Other student researchers in Axford’s lab seek a similar goal from sediment cores extracted much closer to home. Aidan Burdick, also a third-year Ph.D. student in the Department of Earth and Planetary Sciences, gathers sediment cores from lakes in the Midwest. Burdick gestured to a long half-tube of sediment from Crystal Lake, Illinois, on the table in front of him as he described its revelations about the past climate record.

“This core represents about 1,200 years of time,” Burdick said. “We use a technique called radiocarbon dating” to follow the trail of time.

Burdick said radiocarbon dating helps them determine the age of the layers in their sediment cores because it is based on a type of carbon isotope that decays over a set period of time once organic matter such as moss has died. He pointed to the layers on the core that marked when the Europeans settlers pioneered in Illinois.

A bulk of the lab’s work — both in the Arctic and in the Midwest — centers around how knowledge of the past can help scientists understand current and future changes associated with climate change, said Nash. The sediment core displayed in the lab reveals evidence of settlement, according to Burdick, which points toward human effects on climate change.

The team analyzes the organic matter and other components in the sediment cores by using a long, flat piece of technology called the GeoTek Multi-Sensor Core Logger, according to Burdick. The equipment uses a flat bed to move the core through the logger while a camera takes high-resolution images of the sediment core and logs what is found at the various layers. Burdick said it also measures the amount of magnetic material in the sediment, gives numerical values for the varying mud coloration and detects different types of ions and atoms found in the core such as calcium and aluminum.

“We can just put the core on, program it, leave it overnight, and then come in and have a ton of data we can use to help characterize our cores,” Burdick said. “It’s pretty cool.”

Nash acknowledged that climate research is an ongoing process undertaken by scientists worldwide, and her work in Axford’s lab is merely one aspect of the collaborative effort toward understanding the changing environment. She said she entered graduate school starry-eyed and ready to change the world, and she is now recognizing their records are a nuanced drop in the bucket of broader research seeking to answer her biggest questions.

“Those individual drops aren’t going to be reflective of the whole truth,” she said. “We’re really pulling together different elements of what already exists, what’s currently being done, and incorporating it into our story and trying the best we can to build that story.”

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