(truenature)

Farewell, glacier; hello, lake: Fed by meltwater from Grinnell Glacier, Upper Grinnell Lake is getting bigger every year.

Photo by Andrew Geiger

Meltdown

To see how fast the earth's glaciers are vanishing, look no farther than Glacier National Park, where ice formations thousands of years old may be gone in 30.

By Tom Yulsman

With its apron of ice sprawling across 175 acres, Grinnell Glacier in Montana's Glacier National Park should, by all rights, refrigerate its surroundings. But even though we are mere yards from the ice in a cliff-encircled basin at 6,500 feet, it is sultry here today.

"It's bizarre," says Dan Fagre, a bearish, 50-year-old ecologist who has joined me on the trek up to the glacier. "There have been more days in the 90s this July than in the 13 years I've been here. In fact, it's been the hottest July in the last century." A scientist with the U.S. Geological Survey, Fagre is the leader of a team doing pioneering work in this remote environment, which has put him, as he likes to say, on "the front lines" of global climate change research.

Above our heads, a film of smoke drifts over the Garden Wall. This stupendous blade of serrated rock forms both a part of the Continental Divide and the sides of Grinnell's basin—a cirque, in geological terms. The smoke is rising from a small, lightning-sparked fire on the western side of the divide. Fagre speculates that the high temperatures and low humidity are only adding to the park's combustibility. And, in fact, in the days following our hike, this fire and others in the park will grow to 33,000 acres, making headlines worldwide by forcing the evacuation of the park service headquarters and a nearby town (where Fagre and his family live).

For the time being, however, there's just a little smoke in the air; otherwise it is astonishingly clear. To reach this spot, Fagre and I hiked uphill for several hours, making a racket all the way so as not to surprise any jumpy grizzlies. Resting on fossil-studded rock deposited in a sea 1.4 billion years ago, I dip my trail-weary toes in the icy waters of a lake fed by melt from Grinnell Glacier, which, like almost all of the glaciers in the park, is wasting away. In fact, 70 years ago there was no lake here, just glacial ice towering more than 40 feet high.

Of course, these mountains have never been immune to environmental shifts, but today a rising global temperature seems to be hastening the pace of change here and in other mountainous regions. Since the park was established in 1910, the mean summer temperature, estimated from nearby weather stations, has increased by more than 1.66 degrees Celsius—about 3 degrees Fahrenheit. And since 1885, when George Bird Grinnell, founder of the first Audubon Society, became the first white person to stand in this cirque, most of Glacier's glaciers have vanished. Today just 26 remain out of the estimated 150 that existed in 1850. And if computer modeling by Fagre and his colleagues turns out to be on target (so far it has been), the rest could be gone by 2030. "Losing the glaciers in Glacier National Park is a supreme irony," he says. "One that should tell us that global warming is real."

Glaciers are exquisitely sensitive to climate changes because of the way they are born and evolve. For a glacier to form, the accumulation of snow in the winter must exceed melting in the summer. The pressure from the ever-thickening burden of snow on top squashes snowflakes together, creating bigger and bigger crystals that eventually form ice. When the ice reaches a critical thickness—at least 60 feet—it becomes plastic and begins to move downhill, propelled by its own weight and the forces of gravity. This is when it can officially be called a glacier.

Today 10 percent of the earth's land surface is covered with glaciers. But during the peak of the most recent Ice Age, about 18,000 years ago, glaciers buried nearly a third of the world's land area. In Glacier National Park, just the tops of the mountains poked out above the rivers of ice. The unrelenting grinding from these glaciers carved the cirque basins, the bladelike walls of rock called arêtes, and the U-shaped valleys that now help draw close to 2 million visitors to the park every year. In fact, it is this spectacular topography, not the actual glaciers themselves, that gave the park its name.

According to Fagre, the area's glaciers may have completely disappeared when the climate warmed after the Ice Age. But about 7,000 years ago, small glaciers seem to have formed again. Then, between 1500 and 1850, temperatures dropped globally in a phenomenon known as the Little Ice Age. Small glaciers expanded, and new ones probably formed. During this period the Grinnell Glacier filled the cirque basin carved by an earlier ice age.

Glacial expansion in the park peaked around 1850, about the same time that the Little Ice Age was ending. By studying tree rings, moraines, naturalists' notes, photographs, and park records, researchers have charted the rate of glacial retreat in the decades since. Between 1993 and 2001, for example, Grinnell lost 42 acres of ice, or approximately 20 percent of its size. And as Grinnell melts, the lake at its foot enlarges. At its deepest point, the lake is now an abyss 220 feet deep.

The wasting of glaciers in the park is part of a worldwide trend that began with the warming at the end of the Little Ice Age. Globally, the retreat is gaining speed. Since 1988 the rate of ice loss has more than doubled, according to research by Mark Meier and Mark Dyurgerov, glaciologists at the University of Colorado's Institute of Arctic and Alpine Research.

"Losing the glaciers in Glacier National Park is a supreme irony," says a prominent ecologist. "One that should tell us that global warming is real."

The shrinking is particularly acute in tropical regions. Ohio State University climatologist Lonnie Thompson has documented the alarming retreat of ice in Asia, in the Andes Mountains of South America, and atop Africa's highest mountain, Kilimanjaro. In 2001 he reported that at least one-third of the Kilimanjaro icefield had disappeared in the preceding 12 years. Overall, four-fifths of the ice atop the Tanzanian peak has vanished in the past 80 years. At this rate, all of Kilimanjaro's ice will be gone between the years 2010 and 2020, Thompson says.

Where waves of an ancient sea once lapped at a lifeless shore, today an ever-shifting mosaic of life thrives in Glacier National Park. Near timberline, just downhill from where Fagre and I sit, islands of stunted subalpine trees are surrounded by a sea of flower-filled meadows—prime summer habitat for bighorn sheep. Lower still, armies of spruce and fir stand on steep slopes. And carved into the mountain forest are grassy boulevards, open areas bulldozed through the trees by snow avalanches. Fagre says the biological mosaic created by avalanches encourages a rich diversity of plant and animal species.

To show me what he means, he points to the openings in the forest, extending in stripes from valley bottoms to ridge tops; he calls the openings "bear elevators." Grizzlies start at the bottom and browse their way to the top, feasting on berries and other treats that thrive in the sunny openings. And while trees may invade old openings, fresh avalanches create new ones.

But warming temperatures, the accelerated melting of the snowpack, and the quickening deglaciation of the park now threaten to upset Glacier's rich mountain ecosystem. For example, cold meltwater from glaciers helps maintain stream flows in late summer, when rains are scarce and winter snows have melted. "Meltwater from glaciers is critical for aquatic organisms," Fagre notes. As glaciers disappear from the headwaters of valleys, and the snowpack melts earlier, the temperature of water in streams will rise, and some streams will dry up.

The changing climate also could bring more precipitation to parts of Glacier each year. Warmer temperatures would mean more rain and less snow. This, in turn, would result in fewer avalanches and, therefore, fewer bear elevators carved into the forests, Fagre says.

A decrease in avalanches could have other impacts as well. "There is an increase in biodiversity in the snow avalanche paths," which cover up to 20 percent of the park, Fagre says. So the diversity of plant species would decline with fewer avalanches.

The paths also serve as natural firebreaks. So in the future, fires like the ones that made news last summer could travel farther. And finally, if the snowpack were to melt just two weeks earlier, more seedlings of subalpine fir could get a foothold in alpine meadows. (Today snow lingering into summer inhibits this growth.) As the firs invade, flowering meadow plants would lose out. The matrix of different environments—islands of trees separated by meadows—would thus become more homogeneous as the trees filled in, "and the habitat diversity for wildlife would go down," Fagre predicts.

It is certainly true that Glacier National Park—and the entire earth, for that matter—has weathered changes much greater than the ones occurring now. (Just ask the dinosaurs.) Global warming has happened before, glaciers have disappeared, and species have been forced to move. But Fagre believes that the changes today may be happening faster than they have in the past—perhaps too fast for some species to be able to adapt.

"And whether that's true or not, the changes are happening in the context of a fragmented landscape," he says. "In the past, species had a place to take refuge when the climate changed. Now maybe they don't. The Great Plains can't be a refuge for plants when it is wall-to-wall corn."

The rapidly disappearing glaciers worldwide have consequences for humans, too. Meier and Dyurgerov, the University of Colorado glaciologists, recently estimated that glacial melt and the expansion of ocean water as it warms will cause sea level to rise by more than two feet by the end of this century. This may seem small to some. "But a one-foot rise in sea level typically will cause a retreat of shoreline of 100 feet or more," Meier says. He notes that a sea-level rise of just three feet will affect 100 million people worldwide in coastal cities such as Houston, which is not much above sea level now, and New Orleans, which is already well below.

Another detrimental impact, one that has received little notice, concerns the world's water supply. Climatologist Lonnie Thompson of Ohio State describes glaciers as a kind of hydrological bank, into which deposits of water are made each winter. Globally, the glacial account contains about 75 percent of earth's fresh water. Withdrawals from the bank each summer sustain hydroelectric power, irrigation, and drinking-water supplies. (In Washington State, for example, glaciers provide roughly 470 billion gallons of water each summer.) But Thompson warns that as mountain glaciers melt, water is being withdrawn from the bank account more rapidly than it is being replaced.

The trail down from Grinnell Glacier hugs the side of a steep slope, providing panoramic views of the forested valley a thousand feet below us. As Fagre and I head back, we pass from stands of subalpine fir into sunny meadows—Fagre's bear elevators—filled with flowers, including reddish Indian paintbrush and waist-high stalks of bear grass capped with showy white flowers. We continue our conversation about the changing character of the park, and even though the topic is sobering, at least the grizzlies will hear us coming. Fagre tells me that if the earth keeps warming, we should expect to see further ecological alteration of Glacier National Park—more frequent and bigger wildfires, for example, and a major redistribution of grasses, trees, insects, and animals.

Several days later Fagre's predictions hit home. By late afternoon, temperatures have crept up into the high 90s, and the fire that had ignited on the day of our hike has expanded dramatically. As I drive down from the high country through a pall of smoke on Going-to-the-Sun Road, a bright glint of light catches my eye through the yellowish haze. It is sunlight reflecting off a patch of ice on Heaven's Peak, about four miles in the distance. Although summer's end is many weeks away, much of the nourishing snow atop the remains of a glacier has evidently melted away.

I wonder how long it can hang on.

Tom Yulsman, author of the recent book Origins: The Quest for Our Cosmic Roots, is the co-director of the Center for Environmental Journalism at the University of Colorado, Boulder.