Colorado’s lack of dust

For the first time in a decade, cinnamon-colored dirt missing on peaks

In this photo from May, 2009, Andrew Temple of the Center for Snow and Avalanche Studies looks out over dust-covered snow in the mountains surrounding Sen. Beck Basin near Telluride. This year’s snowpack as of last week is dust-free, the first time in a decade.



This snow roller in a gully in the San Juan Mountains offers an example of differential melt rates between clean snow and dirty snow. The white “donut” rolled into the gully from the white, north-facing side of the gully.



QUICKREAD

livestock and dust

Although livestock grazing is a factor in atmospheric-dust production, a 2010 report from the Proceedings of the National Academy of Sciences said dust production from livestock has fallen by about 25 percent since the inception of the 1934 Taylor Grazing Act, which regulated grazing on public lands.

There is no way, several dust experts said , to quantify the impact from numerous causes, including grazing, climate conditions, land management practices or simply driving along a dusty road.

“At this point there are so many factors affecting the availability of dust, so many agents of disturbance, with no clear way to attributing X-percent of dust to any one agent,” Chris Landry, director of the Silverton-based Center for Snow and Avalanche Studies, said. “It’s a complex picture that is discouraging to say the least.”

It’s thought Benjamin Franklin may have been the first scientist to report on the rate of snow melt.

On a sunny day in 1729, Franklin spread several pieces of colored cloth on snow and recorded how quickly the snow beneath them melted.

“In a few hours, the black, being warmed most by the sun, was sunk so low as to be below the stroke of the sun’s rays,” he remarked in a letter to a friend. “The other colors [melted] less as they were lighter; and the quite white remained on the surface of the snow.”



A quick look around the Elk Mountains last Friday from the top of Snowmass Ski Resort revealed something not seen in nearly a decade: Mountain peaks coated in white snow.

That might not seem worth reporting, except for its rarity. This, according to the Center for Snow and Avalanche Studies, is the first spring in the past 10 when dust, blown in from elsewhere on the Colorado Plateau, hasn’t discolored the snowfields covering Colorado’s high country.

That there simply isn’t much snow in the high country was covered in Saturday’s Daily Sentinel by staff writer Dennis Webb.

In recent years, though, spring dust-laden storms similar to the one that hit the Grand Valley on Friday have carried what the Center for Snow and Avalanche Studies is calling an “increasing amount” of cinnamon-colored dust onto Colorado’s alpine peaks, creating dark, dirty-looking snow that absorbs more sunlight and melts more quickly.

This darker snow absorbs more heat than clean snow (think about wearing a black T-shirt or a white T-shirt) and melts faster, hastening the rate of spring runoff. This potentially feeds a series of consequences, including lower summer flows in streams and less water available for fields and forests, which in turn produces more dust.

Chris Landry has been tracking the dust-on-snow phenomenon for his Center for Snow and Avalanche Studies in Silverton since 2003 and in a recent interview said the conditions have worsened lately.

He said the cause is partly because of the prolonged drought and partly to an increase in man-caused dust.

A 2013 report on the website Hydrology and Earth Sciences System said that dust-on-snow deposition can hasten runoff by three weeks compared to clean snow and “extreme” dust years (such as were seen in 2009 and 2010) can hasten runoff by up to six weeks.

This year’s lack of dust-covered snow wasn’t because of a shortage of dust, said Landry, but rather the lack of the right weather patterns.

“Earlier in March the dust wasn’t available (for transport because) the Greater Colorado Plateau received snow and rain during that time,” he said. “A couple of large storm systems cut the availability of dust” even though those storms were windy enough to bring dust to the mountains.

“And then the weather missed the plateau for the rest of March,” Landry said.

He said Friday’s storm was a non-event in regard to high-altitude dust deposition since most of the disturbance was at low elevations.

Landry’s studies, in conjunction with those from the U.S. Geological Survey, say the vast majority of the dust covering the mountains comes from the Greater Colorado Plateau.

“We don’t even talk about other sources,” said Landry, discounting theories blaming deserts in China as a major source of Colorado’s wind-blown dust.

“Such a strong relationship has been established” through analysis of the dust chemistry with parts of the Greater Colorado Plateau, Landry said.

“There are any number of locales within the plateau that can be contributing a lot of (dust) depending on the particulate size, wind, soil conditions and things like that.”

He also said local sources of dust can be major factors.

“The parking lot at A-Basin (ski resort) is pretty intense,” he said with a laugh.

The drought is one reason there is more dust being carried by the wind, but what produces the dust in the first place?

Landry said “anthropogenic causes” such as motor vehicles, livestock grazing, fires and private and commercial development are “clearly recognized to make dust available.”

“But then the drought can also be a factor in that disturbed soils have more difficult time recovering and vegetation may not recover at all,” he said.

And simply receiving more rain might not be the answer.

“In a real ironic twist, in the fall of 2013, there were major rains in the mountains and on the plateau and then there was the corresponding flash flooding,” Landry recalled. “All that streamflow mobilized a whole bunch of new silt, which subsequently dried up and became a new crop of dust available for the next spring.”

“So massively wetting the Colorado Plateau actually made it worse, we speculate,” he said.

April can be one of western Colorado’s windiest and snowiest months and Landry expects to see more dust-on-snow events.

“The only way we’ll get more snow pack is to get some very large spring weather systems, which are increasingly likely to mobilize dust,” he said laughing. “So, it’s a Catch-22.

“But I think everyone would prefer having the water.”

More information about dust-on-snow and the Center for Snow and Avalanche Studies is available at http://www.snowstudies.org.


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