EARS Student in New York Times

On March 18, 2014 by Grad Forum

Justin Stroup in Peru.

Fifth-year earth sciences graduate student, Justin Stroup, loves the outdoors. This passion propelled him from studying Alaskan glaciers during his undergraduate years at Lehigh University, to researching lake core sediments in northern Canada while completing his master’s at the University of Cincinnati. At Dartmouth, Stroup conducts research on the glaciated terrain of the Peruvian Andes. As part of a greater effort to understand how the modern climate system works, he studies how climate has changed over the last 11,700 years (the Holocene), a time in Earth’s climate history that is very similar to today.

In their recent publication in Geology, Stroup and his advisor, Meredith Kelly, (along with collaborators Thomas Lowell of the University of Cincinnati, Patrick Applegate of Pennsylvania State University, and Jennifer Howley also of Dartmouth College) provide a detailed record of Qori Kalis, the largest glacier flowing out from Quelccaya Ice Cap. They used mapping and a dating method that assesses age by measuring Beryllium-10 (10Be) in boulder surface samples to determine how Qori Kalis’ length has changed over the last half millennium. Their study is the first tropical comparison between a record of glacier length and an annually dated ice core; both are part of the same glacial system. The ice core record collected by Lonnie Thompson of the Ohio State University records net accumulation over the past approximately 1,800 years.

Interestingly, Stroup and his colleagues found that Qori Kalis glacier was advancing during times of average or below average accumulation (before ~500 years ago), and conversely, it was retreating during the period of highest accumulation. These findings suggest temperature is a primary factor controlling the growth and retreat of this tropical glacier. This is an important step toward understanding climate conditions in the recent past. This study was featured in The New York Times from February 25, 2014.

The primary physical drivers of glacier growth and retreat in the tropics are being actively debated, and the work of Stroup and his colleagues linking temperature to glacier extent creates very obvious directions forward. Stroup explains their hypothesis that temperature drives glacier length can be further tested by combining his record of past glacial extents with Thompson’s Quelccaya ice core record. “It should be possible to develop glaciological models of the Quelccaya Ice Cap to further test if temperature, precipitation, or other factors significantly influence glacier length.” Stroup adds this examination is currently underway as part of an ongoing collaborative study with Raymond Pierrehumbert of the University of Chicago.

Stroup anticipates graduating this year, and plans to pursue an academic postdoctoral fellowship. “I am always looking to expand my ‘tool box’ so that I may continue to address pressing questions in my field.”

by Gifford Wong

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