Longest Ice Cores Retrieved From Canadian Yukon

The core was the deepest ever retrieved from the St. Elias range that straddles the border of the Yukon and southeast Alaska and includes 19,850-foot high Mt. Logan, Canada's highest peak. "Mt. Logan is well positioned to reflect what's going on in the North Pacific," says Kreutz. He and his colleagues hope to shed light on an El Nino-like weather cycle known as the Pacific Ocean Decadal Oscillation, or PDO.

Based on data collected over the last century, scientists know that the PDO changes every 20 to 30 years and affects weather across North America. The name of the cycle was coined in 1996 by a fisheries scientist studying the relationship between Alaska salmon and Pacific Ocean climate.

The PDO is centered in the North Pacific and has cool and warm phases. Ocean surface temperatures and dominant wind directions are different for each phase. Weather data have been collected since about 1900, according to Kreutz, although scientists have used tree ring analysis to extend that record back to about 1650.

Better knowledge of the PDO may help answer questions about an apparent climate change in northwest North America. The region is home to the largest icefield and number of tidewater glaciers on the continent. Many glaciers have retreated dramatically over the last two decades. "There is no question that a large change is happening in this region," Kreutz adds.

Kreutz has climbed in some of the world's highest mountain ranges to collect ice cores. He has worked in the Andes of Eduador, the Himalayas in Tibet and the Tien Shan Mountains of Kyrgyzstan in central Asia. In his UMaine laboratory, he subjects the cores to detailed chemical analysis. His goal is to understand where the moisture came from, how far it traveled to reach the glacier or icefield and how the atmosphere was circulating at the time.

The St. Elias project involves researchers from UMaine, the University of New Hampshire (UNH), the National Institute of Polar Research (NIPR) in Japan and the Geological Survey of Canada (GSC). Collaborators include Cameron Wake of UNH, David Fisher of the GSC and Kumiko Goto-Azuma of the NIPR.

Kreutz helped to lead a UMaine and UNH team that concentrated its ice coring efforts in an area known as the Eclipse Icefield east of Mt. Logan at an elevation of about 10,000 feet. Analysis of the ice cores, including one recovered from near the summit of Mt. Logan by a GSC team, will be done at UMaine in collaboration with Paul Mayewski, director of the UMaine Institute for Quaternary and Climate Studies.

Research in the St. Elias range has already provided important clues to how the Earth's climate system operates. In the early 1970s, UMaine geologist George Denton and colleagues studied fluctuations in alpine glaciers and the elevation of tree lines. They were the first to demonstrate that such fluctuations reflect changes in climate.