But where does the dust come from?
And does it really matter that it’s even there?
Yes, according to research being conducted in the high country between Telluride, Silverton and Ouray – and perhaps even more so in the future if, as many scientists believe, the American Southwest becomes hotter and drier.
In fact, dust transported from disturbed desert soils of the Colorado Plateau has hastened melting of the San Juan snowpack in the last several years by anywhere from 18 to 35 days, said scientist Tom Painter in an article published in Geophysical Research Letters in late June.
The seed for Painter’s the dust-snow relationship research was planted in 1998, when he was climbing South Maroon Peak, a 14,000-foot peak near Aspen, with his father, Richard J. Painter, then a mathematics professor at Colorado State University.
It was late June, and there was still snow along the trail as they ascended the peak, but it was dirty snow. The younger Painter idly scraped the snow to expose a white surface, leaving some of the darkened snow undisturbed.
They climbed the mountain, ate their lunches, and in late afternoon returned past the thoughtless experiment. In that brief time, the darker snow had melted several centimeters more than the clean, white snow.
While that was not particularly surprising – we all know that dark colors absorb solar radiation while white surfaces reflect it, something called albedo, and snow has the greatest albedo of any material on the planet – the question arose of where the dust came from in the first place.
Painter, who was then studying in California had been formally studying snow for four years, thought it was because melting snow exposed soil that then blew onto the snowpack, but didn’t really know the answer. Nor did he try to find out until after he got his Ph.D. in 2002 and was aligned with the National Snow and Ice Data Center at the University of Colorado-Boulder.
To conduct the experiment, he needed a relatively pristine place – one not carved up by skiers, and certainly not by snowmobiles. It had to be far away from obvious sources of air pollution, like smokestacks or roads, yet accessible enough for weekly visits.
Painter’s search led him to Silverton. “I’m looking for snow on dust, and you have it,” he said. He was steered to the new Center for Snow and Avalanche Studies, which assists scientists with fieldwork. The foundation has a permit from the U.S. Forest Service to conduct monitoring experiments in the area west of Red Mountain Pass, between Ouray and Silverton.
Called Senator Beck Basin, after a 19th century politician from Kentucky, the area ranges in elevation from a little over 11,000 feet to Trico Peak at 13,321 feet. Trico Peak, located near Black Bear Pass, is so named because it marks the corner of San Miguel, Ouray and San Juan counties.
Painter paid his first visit in February 2003. A dust storm had occurred just two days prior. As he skied to the test site above timberline in Senator Beck Basin, he noticed the color of the snow. Normally, it has a bluish hue. The snow that day, he said, was pink.
Changing the Cycle
Painter’s argument – partially relying on the work of others – is that the dust found on the snow of the San Juans is not necessarily natural. In fact, he said, disturbances in deserts of the Southwest have increased substantially in the last 140 years.
Because of global warming, the dust is likely to have large implications for the 35 million people dependent on the water of the Colorado River and its tributaries. It is a river system driven by snowmelt, with 75 percent of all water arriving in the form of snow, mostly from the high mountains.
Reservoirs do tame the snowmelt cycle; some 16 times the total annual flow of the river can be kept in storage, half in the two big buckets of Powell and Mead. But lower elevation reservoirs lose much water to evaporation. Lake Powell loses six feet each year to evaporation. The most efficient reservoirs are the alpine snowbanks, which, even into July, continue to melt in the high country.
The Colorado River Basin has no surplus water. Virtually none reaches the Sea of Cortez, and most of what does make it to Mexico is brackish and of poor quality.
Climatologists are uncertain whether global warming will produce more, or less, water for the Colorado River Basin. But computer models are nearly unanimous in predicting sharply increased temperatures. That hotter weather will, in turn, cause more evaporation and the drought-like conditions of today could quite possibly become the norm of tomorrow.
If the deserts, their soils already disturbed, become drier, they could yield even more dust on the snowpack of the San Juans and, to a lesser extent, across the Colorado Rockies. Dust storms most frequently occur from February through May. As well, the effect of dust on snow melt is more pronounced as the days get longer and the sunshine falls more directly on the snowbanks.
The Dusts of Spring
How does Painter know where the dust comes from?
First, satellite images allow Painter and other scientists to see plumes of dust rising from the desert and moving toward the Rocky Mountains. Mostly, dust comes from nearby deserts, although dust storms from as far away as Asia have been tracked.
Second, scientists can analyze the chemistry of the dust, looking for chemical isotopes that can be traced to the bedrock of certain regions.
An expert in identifying the fingerprints of dust is Jason Neff, a biogeochemist with the Geological Science Department at the University of Colorado-Boulder. The isotopes clearly tell the story of the dust.
“With that information, we can say very definitely it’s not local,” said Neff. “It’s not from wood-burning, it’s not road dust and it’s not stuff flying off ridges from near the sample sites. It’s traveling into the state and being deposited on the snowpack.”
Scientists can not currently pinpoint the precise source of the dust – say, for example, a location 20 miles from Flagstaff, Ariz. – but Neff said relatively little of the dust is natural to the area. Some places, such as the playas or dry riverbeds and lakes, are natural sources of dust. Most of the dust from deserts is the result of soil disturbances.
Neff participated in a study in Canyonlands National Park that found a progressive loss of surface soil in areas that have been grazed, as compared to areas not used by domestic livestock.
“One-hundred years of grazing in the American Southwest, at least in that particular place in Utah, has led to a pretty large loss of soils,” he said.
Neff is conducting a study in the San Juans on core sediments taken from above-timberline lakes – including atmospheric dust that has been deposited. One goal of the study is to determine whether there have been major changes during the time of Euroamerican settlement.
“We actually had a lot more grazing 100 years ago than we do now, although we now have more cars, home construction and recreational use” in the desert Southwest, he said.
Neff plans to publish his study results later this year.
Desert Dust Isn’t Natural
Jayne Belnap, from Moab, has also studied changes in the deserts of the Southwest. A soil scientist with the U.S. Geological Survey, she used advanced equipment to simulate the effect of wind in the desert.
The goal was to see what sticks and what flies.
Belnap said few deserts are naturally dusty. In the American Southwest, the story is largely one of disturbances – from livestock grazing, recreational vehicles and home construction.
“Anything that has a compressional force,” said Belnap. “It doesn’t matter whether it’s a hoof, a bike, or an ATV, or a tank – anything will disturb that surface.”
This is, she repeated, not normal. Desert soils will mostly stay put if they aren’t disturbed.
But the vagrant dust in the Southwest has altered the hydrology of the region. Even if the reservoirs could hold the floodwaters of a rapid spring runoff, the rhythm is changed, she said. Among water quality problems will be increased sediment loading.
Brad Udall, director of the Boulder-based Western Watershed Assessment, said Painter’s study has not yet raised eyebrows among climate scientists, but water managers are paying attention.
Flying from Denver to a water conference in Las Vegas in May, Udall remembered looking down on the mountains around Crested Butte and noticing how dirty the snow appeared.
“It’s certainly a wild card,” he said. “It’s something about which we need to know a lot more.”
Studying Snow in Silverton
A key factor in Painter’s work is the assistance of Silverton-based Chris Landry, who does much of the fieldwork.
Landry has a long history with snow, beginning at Whitefish, Mont., where he learned to ski and his parents (his father was a 10th Mountain Division veteran) managed the Big Mountain ski area. Living in Aspen in the 1970s and early 1980s, Landry was one of the pioneers of extreme skiing, notching first line descent on the east face of Pyramid Peak as well as on Mt. Rainier.
In 1999, while living in Carbondale and plotting avalanche safety for marble-mining operations at the Marble quarry, Landry witnessed a major dust storm on March 1.
“It was bright red and out of the southwest,” he recalled. “Visibility in Carbondale was only two miles. You could hardly see the edge of the valley. That one caught my attention.”
Landry later got a master’s degree in snow studies at Montana State University, and moved to Silverton in 2002 to establish the Center for Snow and Avalanche Studies. Silverton has a history in recent decades of being a base for scientific experiments as well as avalanche studies, and has lower costs than many old mining towns with more robust tourism and real estate based economies.
Aided by one or two assistants, Landry conducts fieldwork for several university-based scientists.
Jeff Dozier, a professor of snow hydrology at the University of Santa Barbara, said the importance of Painter’s work stretches far beyond Colorado. Conditions similar to those of the San Juans exist in many other areas, and the water supply for about a billion people in the world is dependent on melt from snow or glaciers.
“In considering future climate changes, we often focus on warmer temperatures,” said Dozier. “In the high alpine zone, however, snow is more sensitive to the amount of solar radiation absorbed than it is to the air temperature.
“For this reason, a change in the amount of dust from the desert (perhaps caused by drier conditions) is probably more important to the San Juan snow than a change in temperature.”
This summer, Painter, 41, became an assistant professor at the University of Utah. He had previously lived in Utah as a young man, when he was uncertain of what his future held, but with the goal to compete as a freestyle skier. Now, Painter said he figures snow has enough mysteries to keep him occupied for a lifetime, and then some.