A canary in an ice-rich rock glacier in Alaska

Emily Schwing: It is American scientist‘s 60-Second Science. I am Emily Schwing.

How do you fight an uphill battle when the problem moves down? This is exactly what Denali National Park resident geologist Denny Capps is trying to figure out.

Caps: Over the past few years, the Pretty Rocks landslide has grown from a minor maintenance issue to our biggest challenge.

Schwing: On a cool autumn day in September, just outside the park entrance, not much was happening inside the offices. Staff are one week away from the park’s winter closure. But over 40 miles down the park’s only road, at a place known as Pretty Rocks, things really go downhill, down to half an inch an hour.

Paul Ollig: The Pretty Rocks landslide acts much more like a glacier than what most people think of as a landslide.

Time-lapse image of the Pretty Rocks collapse from July 21 to August 25, 2021. During this time, the road was moved 21 feet. Credit: National Park Service Geology Team

Schwing: Paul Ollig is the director of interpretation and education in Denali.

Ollig: In that it is this very rich ice material that reacts to temperature fluctuations and will speed up and slow down depending on many different factors, regarding the level of the ice, the temperature of the ice. And so we tend to think of the Pretty Rocks landslide as a rock glacier rather than what we would generally think of as a landslide.

Schwing: Ollig says the landslide is a harbinger of what could happen to the entire United States national park system.

Ollig: It is, in my opinion, a sort of ‘canary in the coal mine’ type situation, where we are on the front lines of these impacts of climate change. But as we see more and more of them, more and more parks are going to face other challenges that can be just as, if not more, difficult to understand.

Schwing: Here in the heart of Alaska, much of the ground is believed to be semi-permanently frozen for most of the year. But Denny Capps says signs of climate change here have been evident for years.

Caps: Denali is a great place to understand what that future looks like. And also, with the temperatures that we have had over the last few years, we are already reaching the 2040 forecast for here and places in the park. So we’re well ahead of the current predictions of climate change here in the park. So that really caught our attention.

Schwing: At Pretty Rocks, road conditions changed so much at the end of this summer season that park officials eventually had to shut it down, cutting off access to a visitor center with direct views of America’s tallest mountain. North and a wild lodge. And Pretty Rocks isn’t the only place that occupies Denny Capps.

Caps: Yeah, definitely not. It’s all along the park road that gives us problems with permafrost. We have a system we call the Unstable Slope Management Program, where we track over 140 unstable slopes along the park road. Now, not all of them are necessarily conditioned by permafrost, but many are.

Schwing: When you say 140, that seems like a pretty high number of places to watch for the park.

Caps: That’s a relatively high number, but we want to make sure and not always be in a reactive position. And some of those sites are very minor maintenance issues – you know, things that we might have had to do a bit of background work on in the past. And we’re just looking up to Pretty Rocks. We have like a major mass bearing causing road closures, so a whole range of severity and type of magnitude and frequency of impacts at all levels.

Schwing: So what’s causing all this movement? Warmer temperatures all year round combined with increased summer precipitation – all of this is helping to melt what was once frozen ground.

Caps: I know I have seen more intense rains and floods. We have had a number of precipitation records that have been set in the 10 years that I am here, including very intense precipitation. We had what long-range Alaskan meteorologists described as the highest amount of daily precipitation for a non-coastal site and in history recorded here last year. Here on the north side of the mountains, where it’s relatively dry and where we have a lot of topographic relief, we have permafrost melting. Having rain at this level could be catastrophic for us.

Schwing: It’s like pouring hot water on an ice cube.

Caps: It really is. And that’s one of the things we’ve come to recognize, it’s – it’s really important – it’s that rain and, more specifically, the temperature of that rain, because I think we all know. that, you know, if you have hot air it can definitely heat things up. But if you have hot water, it actually carries more heat with it, and it brings that heat back to the ground. So we really come to recognize the importance of the amount and temperature of precipitation falling on these sensitive areas.

Schwing: Because much of Denali National Park is classified as a wilderness area, long-term solutions are limited.

Caps: Unfortunately, we don’t want to experiment too much here. You know, it’s a sensitive place. So, for example, in other places, instead of filling it with gravel to build the road, you can put styrofoam underneath as it insulates the ground and it is much lighter. However, we don’t want the styrofoam to spill over into our environment here and rain plastic down our rivers forever.

So, you know, we’re figuring out exactly what we’re going to do at these locations. But in general at Pretty Rocks we’re probably going to end up bridging the landslide there. This is one of the classic ways of dealing with any kind of geological risk like this. If you have a bull charging at you, you step aside and let it go. You don’t straighten your shoulders or try to stop it. And so that’s basically what we’re going to do — try to do — at Pretty Rocks.

Schwing: Denali is the third largest national park in the United States. The two that exceed it in size are also located in Alaska: Gates of the Arctic and Wrangell – St. Elias. And here too, large strips of permafrost are at risk of melting. From Paul Ollig’s perspective, with a focus on educating and informing the public, he says there might be a silver lining.

Ollig: Having specific infrastructure, like a potential bridge over a landslide like Pretty Rocks, is a great tool to use. As difficult as it may be, it gives us a very tangible element to frame the conversation about the impacts of climate change and to talk about solutions, to talk about what is going to be required of parks in order to adapt to changing conditions.

Schwing: Park officials are working on plans for a $ 55 million bridge over the declining section of road at Pretty Rocks. Construction could start as early as next summer. Now that fall has set in and the park has received its first snowfall, there isn’t much left to do but watch and wait.

Caps: We are really curious to see how he will react during the winter. So last spring when we got out of the spring road opening at the end of March, we had an escarpment of about 18 feet vertical that collapsed. So we already have an 18 foot vertical escarpment there. So we certainly expect major challenges next spring.

Schwing: As is normally the case in Alaska, you never quite know what the snowmelt might reveal when the warmer weather returns the following year.

For 60-Second Science, I’m Emily Schwing.

[The above text is a transcript of this podcast.]

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