by Dan McGrath, Associate Professor of Cryospheric Sciences, Colorado State University; Ashlesha Khatiwada, Ph.D. Candidate in Geoscience, Colorado State University; and Scott Hotaling, Assistant Professor of Watershed Sciences, Utah State University
If you have ever hiked in the high peaks of Colorado, the Wasatch Range in Utah or the Tetons in Wyoming, you’ve almost certainly seen a rock glacier, perhaps without even knowing it.
Rock glaciers are slow-moving masses of rock debris and ice that flow downhill the same way that glaciers do, but they are covered by a thick layer of rock and boulders that can easily be mistaken for stable ground.
There are at least 1,500 active rock glaciers across the western U.S., and they’re important. That’s because while the icy white glaciers people typically picture have been shrinking and even disappearing, a new study shows that rock glaciers and their frozen water are remaining mostly stable despite rising temperatures.
The thick debris mantle shades the ice, keeping it colder, similar to how ski areas have started covering their slopes with reflective blankets in summer to stave off melting. The result is that rock glaciers continue to provide meltwater for streams in summer, and the study showed that having a major ice source feeding a stream has limited the warming of that stream over the past decade.
Researchers found that streams fed by rock glaciers warmed slowly, by about 1.1 degrees Fahrenheit (0.6 degrees Celsius) over the decade, while streams fed by icy glaciers warmed by about 1.6 F (0.9 C). Streams that were fed by seasonal snowpack, small patches of ice and groundwater warmed much more rapidly, by 6.1 F (3.4 C) over the same period. In one instance, the small snowfields feeding one long-term study site largely disappeared, causing the stream below it to stop flowing by late summer.
Rock glaciers will not replace the glaciers and snowfields that are disappearing. A recent study estimates that rock glaciers in the region hold the equivalent of 0.6 cubic miles (2.5 cubic kilometers) of water, about one-fifth the amount held in mountain glaciers. And climate projections show that even rock glaciers are not immune to a warming climate — many could become ice-free by the end of the century.
This article is republished from The Conversation under a Creative Commons license.
