I remember camping near the terminus of the Dinwoody Glacier in late July one summer. Dinwoody Creek braided its way across the meadows below camp after slipping out from under the rocky moraine that marked the dirty end of the glacier. The site could have been taken from a magazine advertisement. Our tents were pitched in an alpine meadow painted with the bright pinks, blues and yellows of moss campions, forget-me-nots and drabas. Twisted, battered Engelmann spruce and subalpine fir created knee-high islands of deep green that protected our site from the relentless wind. And all around us towered the snowy peaks of the northern Wind River Mountains.
Rising Temperatures, Melting Glaciers
Fifty years from now this site may be totally transformed. Temperatures in the Wind Rivers have gone up as much as six degrees in the last 40 years, according to research done by a team led by Utah-based U.S. Geological Survey scientist David Naftz. And with that temperature rise, the glaciers are melting.
"High elevations seem to be experiencing higher rates of temperature change than low elevations," Naftz says. He bases his conclusion on ice-core samples taken from the Upper Fremont Glacier in the northern Winds. If the current warming trend continues, the Wind Rivers' glaciers Ñ which represent the largest concentration of alpine glaciers left in the American Rockies Ñ may be gone in as few as 30 years.
The Wind Rivers' glaciers aren't the only ones disappearing. Evidence taken from satellite photographs show that most of the world's 160,000 glaciers are retreating at unprecedented rates. Scientists predict that the ice will be gone from the Rockies, Cascades and Glacier National Park by the middle of this century. The Alps, Himalayas and Andes are expected to be devoid of ice by 2100. Even Alaska's glaciers will be considerably smaller in 100 years.
George Kerr, a professor of civil and architectural engineering at the University of Wyoming, studied Dinwoody and Gannett Glaciers in the early 1990s. Kerr's studies, coupled with work conducted in the late 90s by other scientists, show that between 1950 and 1999, Dinwoody and Gannett Glaciers shrank 37 percent, with 67 percent of that loss occurring in the last decade of the study. While dramatic, Kerr says the accelerating melting during the 90s does not necessarily reflect a rise in temperatures.
"It's like an ice cube," he says. "At first, the rate of melt is quite slow, but as the cube gets smaller and the ratio of surface area to volume increases, the rate of melt also increases. It's the same with a glacier. As it gets smaller, more surface area is exposed and it melts faster."
Gannett Glacier
Photo by Marco Johnson
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Glacial Melt Vital in Water-Scarce Wyoming
Glaciers act as natural reservoirs, storing water in the winter and releasing it throughout the summer. For a few years, the increased melt rate of the glaciers as they shrink could actually benefit ranchers in the Wind Rivers' watershed by adding to stream flows. But in the long run, the loss of the glaciers will reduce the amount of water available for agricultural and domestic use, especially in late summer and fall.
Glacial melt is particularly important in years with low precipitation when other water sources, such as winter snow pack, may be in short supply. How much less water will be available without glaciers is unknown, but in a land of water scarcity, any loss is significant.
"When and if the glaciers disappear, there will probably be some pretty dramatic effects on late-season irrigation, stream flows and interstate water compacts," Kerr says.
Temperature changes have also been documented by tree-core samples taken in the Winds by a team led by Lisa Graumlich, executive director of the Big Sky Institute for Science and Natural History and a professor at Montana State University in the Land Resources and Environmental Sciences Department.
"Our data, which goes back to about 1500, shows that cycles of 20- to 30-year drought are normal for the Northern Rockies. But what's remarkable about what we are currently experiencing is the combination of warmer temperatures and extended drought," Graumlich says. "The last time we saw anything like this was 1,000 years ago. It's a bad time to be a glacier."
Glacial size is a function of two things: the amount of snowfall feeding the glacier in the winter and the amount of melt depleting it in the summer.
Graumlich and her team wanted to understand what combination of melt and freeze was causing the Winds' massive glacial retreat. They looked at tree-ring data taken both from alpine tree line and from the lower forest boundary to get a sense of the changing climate.
"Data taken from tree line tells us about variations in the growing season," Graumlich says. "Those trees are most limited by temperature. The lower forest boundary is more moisture-limited, so data taken from there acts like a rain gauge over time. What we've found is that the Wind River glaciers are experiencing a double whammy. They are receiving less precipitation and they are also being exposed to warmer temperatures than we've seen in the recent past."
Threats to World-Class Trout Fisheries
The disappearance of glaciers and warming air temperatures will not only reduce the amount of water flowing out of the mountains, it is also likely to cause a corresponding rise in water temperatures. Changes in water temperature mean changes in habitat for both plants and animals.
A recent U.S. Environmental Protection Agency study found that a moderate warming of 4.5 degrees could cut the habitat of brook, rainbow and cutthroat trout by a quarter to a third nationwide. In the Winds, where Naftz documented a temperature increase of six degrees, the blue-ribbon trout fishing that draws anglers from around the world is sure to be adversely affected by temperature change.
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