Guarini Alumni Research Award Recipient 2019: Gabe Lewis, Earth Sciences

Understanding natural climate oscillations is imperative to determining the amount of anthropogenic impact on climate change. The arctic is currently warming two-to-three times as fast as the global average, a phenomenon known as artic amplification, causing glaciers at high latitudes to melt at unprecedented rates. Very few high-elevation temperature records exist in the arctic, making the existing ice core and weather station records imperative to maintain.

In 2013, a group from Dartmouth College drilled two parallel 208 m long surface-to-bedrock ice cores from the summit plateau (3900 m elevation) of Mt. Hunter, Denali National

Park, Alaska. These cores contain temperature and precipitation proxy records over the past 1200 years and show a doubling of precipitation since ~1840 CE. Previous studies by researchers at Dartmouth College attribute this precipitation increase to a strengthening of the Aleutian Low pressure center caused, in part, by warming of the western tropical Pacific and Indian Ocean sea surface temperatures from anthropogenic climate change. Similarly, they find a sixtyfold increase in total annual melt between 1850 and present, representing a summer warming of at least 1.92 ± 0.31 °C over the past 100 years. These results show rapid high elevation warming in the Alaska Range for at least the past century, and that the glaciers' health is at risk if similar magnitude warming continues.

Dartmouth Earth Science professor Erich Osterberg installed a weather station on Mt. Hunter to analyze warming in the Arctic, but ice core records provide vital information for snow accumulation and melt to interpret the longer cores in context. With financial support from the Dartmouth College Alumni Research Award, David Polashenski '17 and I traveled to Alaska this past summer to collect an ice core in the same location as the two deep cores from 2013. This location accumulates 8-12 m of snow each winter, so it was important to update the record before the 2013 layer became buried too deeply to easily reach. We tested a new drill from the National Science Foundation's Ice Drilling Program Office to collect an ice core totaling just over 50 m, which should update the accumulation and melt record from 2013 to 2019. This data will expand the 1200-year record into the modern and could expand insight into high alpine climate change, weather patterns in the Alaska Range, and will help model how these glaciers will fare throughout the 21^stcentury.

With assistance from the National Park Service and Talkeetna Air Taxi, we successfully transported our ice core from the summit plateau of Mt. Hunter to the nearby town of Talkeetna without damaging or melting the ice. We shipped the samples to Hanover and they are safely sitting in the Dartmouth College ice core freezer, awaiting analysis this coming summer. 

For more information, please listen to an interview with KTNA radio about this work.