December 2, 2009
Professor Studies Changes in Glacier Size
VALDOSTA -- As a teenager in the 1970s, Dr. Edward Chatelain
remembers backpacking with his family amid the Beartooth Mountains
of Montana, and standing in awe at the impressive magnitude of the
many glaciers scattered beneath the crests of the highest peaks in
this remote area.
The young outdoorsman appreciated their importance as an eternal water source for ranchers and farmers in the area, but it wasn't until decades later when he flew over the largest -- Castle Rock Glacier, which rests below the 12,604-foot peak of Castle Rock -- that he chose to make these dwindling sheets of ice the focus of his research.
In 1996, Chatelain and his father chartered a Cessna 170 airplane from West Yellowstone, Mont. and flew over the area he remembered from his youth, but was alarmed to find the glaciers substantially smaller than he recalled. The VSU geology professor wondered what spurred the change. Was this a continuous effect caused by ongoing global warming, or could the decline be the result of more cyclical variations in temperature and precipitation?
After researching regional photographic records from 1951-2004, Chatelain partnered with forest service scientists for a yearlong study that sought to quantify the timing of glacier loss as seen through photographic images. Their findings showed that while continuous reduction in the ice mass of these glaciers seems to be the cumulative result, a closer look incorporating climate records suggests a cyclic history of melting events closely related to climate phenomena such as El Niño.
Chatelain said his first challenge was gathering baseline data due to the remote nature of the region. The earliest photos, captured in the 1898 Wilse Expedition, show the famous Grasshopper Glacier near Cooke City, Mont. to be five miles long, but photos from 1951 show the ice sheet had diminished to only one mile. No photographic record of the Castle Rock Glacier could be located prior to 1932, but comparisons with later 1951 photos also suggest a 50 percent reduction in the same time interval, which ran concurrent with the Dust Bowl period of extreme drought and excessive high temperatures. More extensive photos from 1971 and 1976 suggested an apparent stabilization of the larger glaciers in the region, which lasted through about 1983.
"I wanted desperately to locate photos of the Beartooth glaciers in the period of time before 1950, but the records are sparse," said Chatelain, who instead focused on the more recent images. "We wanted to look at the overall picture to create a more complete analysis and determine if loss was a continuous linear trend or part of a larger cycle."
During the one-year pilot study titled "Monitoring Climate Changes in the Beartooth Mountains of the Custer National Forest," the research team worked with GPS systems to make three-dimensional images out of flat aerial photos taken in approximate 5-year intervals from 1950-2003. After analysis of the images, they were able to determine the rate of loss of ice and estimate surface elevation reductions in terms of meters over the intervals between successive photos.
They also noticed correlations between glacier loss and climate phenomena, such as El Niño, as well as anomalies such as the Yellowstone forest fire of 1988, which aggravated melting by covering the glaciers with soot.
"Most people don't realize that the small cirque glaciers we have now in the Rocky Mountains are not remnants of the Pleistocene Ice Age; they are remnants of the 'Little Ice Age,'" said Chatelain. "Technically we are still in that ice age. It is cold enough, but it is too dry today to build glaciers."
Chatelain maintains that the short length of available climate records in the area makes it difficult to identify long-term trends. Global warming was far more severe in the Dust Bowl days of 1930s, but has received little attention since many US climate station records began in 1949. The longest climate record in the region is that of the Yellowstone National Park Headquarters located at Mammoth, Wyoming, which only extends back to 1890. In contrast, the Little Ice Age existed from 1300-1800 AD.
Overall, the VSU researcher proposed that continuous global warming is not the main cause for the size reduction of the Beartooth glaciers. After an initially warm period from 1949-1967, the cool, wet period from 1968-1983 allowed many glaciers to actually stabilize their boundaries. Droughts then affected this region in the 1980’s and 1990’s. El Nino years in 1976, 1981, 1987, 1988, 1994, and 2001 robbed the region of vital winter snowfalls by shifting storm tracts farther south. Summer Heat waves in 1988, 2002, 2006, and 2007 were also significant. He believes we can expect the cycles to continue.
Chatelain pointed out that most climate records from before the 1950s were taken in cities -- far from the chilly Montana mountain glaciers. He plans to continue charting climate changes back into the beginning of the 20th century to search for more ups and downs in temperatures in hopes of finding more support for his cyclical theory.
Improved technology will help his research into more recent years. "Sno-Tel" climatic stations, operated by the National Water and Climate Center, are positioned in mountain areas too extreme for humans to monitor in order to provide readings on temperature extremes, snow depth and precipitation much closer to the glaciers.
The issue of glacier loss is an important one for those who depend on them for the constant water supply they provide. Although Chatelain doesn't believe we have the ability to do much about loss, he hopes his research can provide more insight into the hows and whys of glacial cycles.
View a PowerPoint presentation about glacier loss by choosing the link at the bottom of Chatelain's Web page: http://www.valdosta.edu/~echatela/ .
Dr. Chatelain's research was recently featured in the Billings Gazette, published in Billings Montana. Read the full story at http://www.billingsgazette.com/email/top-headlines/article_bffb030c-888b-11de-976b-001cc4c03286.html .