One year ago, a massive avalanche broke from Highland Ridge and slid all the way into the Conundrum Creek valley near Aspen. It was one of about one-thousand avalanches statewide that were reported during the first two weeks of March, 2019. Recent reporting from Aspen Journalism digs into how that historic avalanche cycle might connect to climate change.
Host Molly Dove discussed the story with Aspen Journalism environment editor Elizabeth Stewart-Severy.
MD: What was unique about the avalanche cycle last March?
ES: Well, first, the sheer number of avalanches. As you mentioned, there were about 1000 slides reported to the Colorado Avalanche Information Center (CAIC) in just two weeks, and the scale was also unique.
Avalanches are measured on a five-level scale for how destructive they are – the D scale. Aspen Journalism’s Catherine Lutz reported that last March was the first time in Colorado history that avalanches were classified as D-5, the most destructive.
Three avalanches statewide were categorized as D5, including two in Aspen. The Conundrum slide was one of those; it had a crown that was estimated to be two miles wide, and it ran 3,000 feet down hill, crossed Conundrum Creek and continued 300 feet up the other side of the stream. Just massive.
The other local avalanche that was classified as the most destructive on that scale was on Garrett Peak, which is up East Snowmass Creek, easily visible from Snowmass Ski Area.
MD: Why were those avalanches so destructive?
ES: Catherine talked with several snow scientists about this, including Ethan Greene, who is director of the CAIC. He breaks down this cycle into three phases.
First, there was a lot of early-season snow that formed a weak base layer. That was followed by pretty consistent snow throughout the winter that meant those weak layers didn’t slough off as they might have if there were dry spells or major storms.
Finally, in March there was this series of really wet storms that were borne on atmospheric rivers — narrow streams of concentrated water vapor in the sky. The strong snowpack — on top of the unstable base — couldn’t withstand the weight of the new, wet snow, and really large avalanches broke across the state.
Now, scientists are identifying some elements — warmer temperatures, wetter air and snow, and more-intense storms — that are consistent with a warming climate.
MD: So, does this mean that with a warmer climate, we’ll see more avalanche cycles like last year’s?
ES: That’s not clear. In her reporting, Catherine found that, in the US, there hasn’t been much scientific study of the link between climate change and avalanche activity. But there are some pieces to the puzzle that have been studied.
Chris Wilbur, who is an engineer and alpine natural hazards expert, has documented that winter storms are getting warmer, and the 2019 cycle may be consistent with what he described as “climatic trends of warmer and wetter air masses colliding with our mountains.”
Wilbur also surveyed more than 200 experienced avalanche practitioners across North America, and respondents across all regions predicted more wet avalanches and more avalanches at higher elevations.
But those experts also predict that the stability of the snowpack will increase with wetter, denser snow.That’s typically good news for backcountry skiers, but Wilbur says climate change just adds another wild card into an area that’s already full of variability.
MD: What are we seeing this winter?
ES: We haven’t seen the same scale of avalanche activity as last year, but Ethan Greene with the CAIC told Catherine that there are similarities: A weak base layer from early-season storms, a pretty strong snowpack from smaller storms through the winter and there was an atmospheric-river event in February that lead to what Greene said were 50-year avalanches.