In May of 2013, a collaborative team led by Erich Osterberg (Dartmouth College), Cameron Wake (University of New Hampshire), and Karl Kreutz (University of Maine) returned to Denali National Park to collect two ice cores to bedrock from the Central Alaska Range, completing a campaign 6 years in the making. We expect these cores to provide a wealth of information about Alaskan temperature, precipitation, wind patterns, volcanic activity and pollution over at least the past 1000 years.
In recent years, Alaska has experienced some of the most dramatic warming and loss of mountain glaciers in the world. However, there are few climate proxy records from Central Alaska to put these modern changes into the context of geologically recent cold and warm periods such as the Little Ice Age and Medieval Climate Anomaly. The aim of our project is to fill this knowledge gap on the dynamics between climate change and mountain glacier response in this globally significant environment.
Over five previous field seasons, we collected meteorological data, ice thickness and flow measurements, and shallow ice cores and snow pit samples from several regions within the Park to find the best location for extracting an ice core (see Uncovering Denali, In-Depth, Fall 2008). After investigating several options within the Alaska Range, we concluded that the Mt. Hunter summit plateau is an ideal ice-drilling site. This location is high enough in elevation so as to experience little summer melting, and is also flat lying with simple stratigraphy and few crevasses. These characteristics should provide a continuous and well-preserved ice core climate record.
Though we also selected the site based on relative ease of access, the Mt. Hunter Plateau remains one of the most inaccessible regions in North America. In May, we flew onto the Kahiltna glacier via ski plane from Talkeetna, AK. Because Mt. Hunter Plateau is at 13,000 feet elevation, it was necessary to spend the first two weeks of our field season acclimatizing on the West Buttress of Denali before making the helicopter flight up to the drill site. When we arrived at Mt. Hunter, we quickly got to work setting up the solar- and wind-powered Eclipse Ice Drill under the direction of IDDO driller Mike Waszkiewicz. The Mt. Hunter plateau glacier is just over 700 feet thick, and we were able to drill two ice cores all the way to the bottom in the span of 3 weeks.
While on Mt. Hunter we took the opportunity to conduct as much research as we could in addition to collecting the ice cores. Seth Campbell (UMaine and CRREL) gathered radar profiles and GPS points to measure the depth of the ice and the velocity of the surface ice flow. We also dug many snow pits, four of which were sampled for a variety of chemical properties, which will tell us about recent climate changes. These data will help us to interpret our long-term ice core record. Finally, we set up two weather stations which are continuously collecting temperature, snow depth, wind speed, radiation, photographs and more, and sending the data back to us by satellite modem.
Remarkably good weather allowed us and the ice cores to make a safe trip off the mountain two weeks ahead of schedule. The ice was immediately transported to the National Ice Core Lab (NICL) in Colorado via freezer trucks where it will be thoroughly measured and processed for chemical sampling. Some of the ice will remain in archives at NICL so that future scientists will have access to the Mt. Hunter core as new analyses are developed. The rest of the ice will be transported to Dartmouth College where we will melt and analyze the cores in the coming year or so.
Many thanks to all of our supporters including the National Science Foundation, the National Park Service, IDDO, CH2MHill Polar Services, Talkeetna Air Taxi, PolarTREC, and our many invaluable volunteers.
For more information about the project, visit:
http://now.dartmouth.edu/2013/07/dartmouth-drills-at-denali-to-document-climate-change/