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Home U Rising This researcher is on a quest to understand how dust impacts Utah’s precious snowpack


Utah’s mountains received a short-lived sprinkling of snow earlier this month and McKenzie Skiles is among those hoping for more snow soon. Skiles is an associate professor of geography and directs the Snow Hydro Lab at the U, where she researches how dust from urban and natural sources, such as the Great Salt Lake, impacts snowpack. In this episode of U Rising, host Julie Kiefer talks with Skiles about the surprising—and perhaps alarming—relationship between dust and snowmelt and the implications of a drier climate on snowpack and water resources.

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Julie Kiefer: Welcome to U Rising, where we share stories about interesting and often groundbreaking research and innovations taking place at the University of Utah.

I'm Julie Kiefer, the associate director of science communications at University of Utah Health and host of this episode.

My guest today is McKenzie Skiles, an associate professor of geography and director of the Snow Hydro Lab at the U, and we're going to talk about her research on how dust impacts our precious snowpack in Utah.

Welcome to U Rising, McKenzie.

McKenzie Skiles: Thank you for having me.

Julie Kiefer: McKenzie, what first drew you to snow hydrology and snowpack and by the way, what is snow hydrology?

McKenzie Skiles: Yeah, so I'll answer that one first. Snow hydrology is the study of how much water is held as snow. I focus on water held as snow in mountain environments, which is really critical here in the Western U.S. It provides the majority of our water resources, acts as a natural reservoir storing water through the winter and then melting off in the spring and summer.

And I started studying snow hydrology because I was really interested in the impacts of climate on snow cover and I got interested in that growing up in Alaska and basically skiing a lot and seeing changes in the snow that normally you wouldn't notice over a lifetime. And when I came to the University of Utah to do my undergraduate, I was fortunate enough to meet my graduate advisor who was studying snow hydrology and I learned that you could combine my interest in climate and my love of skiing, and I turned that into a career.

Julie Kiefer: I love it! I think your work is so interesting. What made you decide to focus on the effects of dust in particular?

McKenzie Skiles: Yeah, so like I mentioned, I was really interested in impacts of climate warming and climate change and actually my first field season as a graduate student in Colorado ended up being a very dusty season. The snow was really dark and so I focused on comparing the impacts of this snow darkening from dust deposition to the impacts of a warming climate. And we actually found that dust deposition has immediate and really dramatic effects on accelerating snow melt, more so than warming air temperatures. And so after that sort of first season of study, I just got hooked and wanted to understand the process of dust and dust deposition on snow more.

Julie Kiefer: You direct the Snow Hydro lab at the U, which carries out a lot of this research. What are some of the lab’s projects right now?

McKenzie Skiles: Yeah, we have a wide range of projects. So, we do study the impacts of dust on snow. That's one aspect of the research. Another aspect is taking basically measurements both from satellites and on the ground of snow processes and building those into models that can forecast snow melt because it's such a critical water resource in the West, we want to be able to represent the processes that control snow accumulation and snow melt. And currently snow melt models are primarily statistics based upon this long record of measurement and not based upon the processes that control snow melt and we're trying to change that. We're trying to build these models that can more accurately forecast snow melt in the face of processes like dust on snow and a warming climate.

                McKenzie Skiles

Julie Kiefer: And so drought in Utah over recent years has caused the Great Salt Lake as well as other Utah lakes to shrink, exposing more lakebed, which has created more dust storms. And this is a relatively new phenomenon in the context of the Great Salt Lake. Is that right?

McKenzie Skiles: That's true. There's a couple things that have led to declining lake levels in the Great Salt Lake and one of the primary ones is people. We use the water that is running out of the mountains before it actually reaches the Great Salt Lake. And that has lowered lake levels gradually over time, ever since the Salt Lake Valley was settled. And then on top of that, now it's compounded by drought and climate warming and other processes. And we've gotten sort of into this cycle of multiple years of water use and drought that has led to minimum lake levels in 2021 and then 2022 for the Great Salt Lake and we do see more dust coming off of the dry lakebed due to that.

Julie Kiefer: And for those of us who live around here, not far from the Great Salt Lake, I mean that's been so obvious. You just look out on the horizon and see this—like, where did the water go? It's pretty scary. And so you shifted gears to study this phenomenon. How did you go about doing that?

McKenzie Skiles: Yeah, so I actually started collecting snow samples here in the Wasatch in 2009 when I started graduate school. And that was more of a side project, sort of fun for me to compare it to the snow that we were collecting in Colorado.

And in Colorado, the dust deposition there comes from the Colorado Plateau, which is one of the main dust producers in North America. So, dust deposition on snow in Colorado is very consistent and when I started looking at it here in the Wasatch, the dust levels were much lower. And so, it was sort of a side project for me to compare the two sites.

But then in 2022, it was the first year that I really looked at the snow in the Wasatch and thought it looks like Colorado, it looks dirty, there's a lot of dust on the snow. And that just motivated us to spend a little more time studying it and to see if it was linked back to the dry lakebed or if there was some other process that was contributing more dust than we had seen previously.

Julie Kiefer: And so what'd you find?

McKenzie Skiles: We found that the, well one, in comparison to the previous record that it was a record-breaking year. We saw more dust deposition events and more dust was deposited in the snowpack than we had ever recorded before. And we studied each one of those dust events individually and traced it back to where the source regions were. And we found that the Great Salt Lake dry lakebed was contributing about 25% of the dust that's landing on the snowpack. And that might seem like a low number, but what was important about that is it's a relatively small area, so per sort of footprint, it was contributing the most dust.

The other sources of dust that we see were the Great Salt Lake Desert or the West Desert, and also the Sevier dry lakebed to the south of us. And those have been consistent dust producers over time. We know that those are dust producers and they're just big, vast areas. But the dry lakebed of the Great Salt Lake is relatively small and producing a lot of dust very efficiently. And that's a new source that's really close to the Wasatch Mountains. So, it's having a big impact.

Julie Kiefer: And what is that impact? The snow is melting sooner, right?

McKenzie Skiles: Exactly. So, when it lands on the snow, it makes the snow darker. And a lot of people assume that it's air temperature that melts snow, but it's actually sunlight that melts snow. As days get longer in the spring, there's more sunlight and air temperatures warm up, but we typically get dust deposition in the spring. That's when source regions dry out, that's when wind speeds pick up. And so we're depositing dust on the snow pack when the days are getting longer and making it darker. It's absorbing more sunlight and it's just a very effective way to accelerate snow melt. In 2022, the record-breaking dust year, we found that dust accelerated snow melt by 17 days, so over two weeks of faster snow melt just due to that snow darkening process.

Julie Kiefer: In fact, Snowbird was supposed to stay open until July 4, but they closed two weeks early. And so, is this part of the reason you think?

McKenzie Skiles: I do think it's part of the reason. So, 2023, this past winter, also very dark, probably maybe even more dust than we saw in 2022 and relative to previous really large snow years, because this past winter was record-breaking in terms of snowfall. But in terms of snow melt rates, it actually melted much quicker relative to previous big snow years. And we think dust played a role in speeding up that melt.

Julie Kiefer: It kind of doesn't look very good for the future, right? I mean, we are predicting that the climate will keep continuing to get warmer. What do you think that means for the snowpack? I mean, in terms of this dust phenomenon that you see?

McKenzie Skiles: Yeah, I think we're looking at a future that's only going to be dustier. A lot of times people assume dust is a natural aerosol and there are natural dust aerosols, but the amount of dust that's getting emitted and transported is increasing due to human activity. And that could be direct due to land surface disturbance or indirect due to drought related to climate warming. And when we get less vegetation, more disturbed surfaces and then increasing dry lakebed areas, all of those add up to more dust. And increasingly we're seeing that dust corresponding with the snow season. And that leads to a feedback where we get dust on snow, snow melt accelerates, melts out sooner, and then the whole landscape dries up earlier because the snow melt has melted out earlier than it had in the past.

Julie Kiefer: So, your research is helping to bring some of this to light. I mean, what are you hoping to accomplish with this knowledge?

McKenzie Skiles: One of the things we're hoping to accomplish is just awareness of this increasing dust and dust deposition and the impacts that it has. A lot of the work on the Great Salt Lake dust has focused on health impacts, which is, of course, really important and also air visibility impacts.

But this is another impact that people might not directly think about when they think about the dry lakebed of the Great Salt Lake. And one of the easiest solutions to reduce dust from the dry lakebed is to keep water in the lake because if there's water there, it won't be dust producing.

That dry lakebed is just so close to us. It's on the scale of tens of miles, not hundreds of miles, like other dust source regions. And so, when dust is produced from the dry lakebed, it's really hard for us to avoid it because we live right next to it. And then it's also hard to avoid deposition on the snowpack. So, awareness of that process and just how important snow is for us and for our water resources. We wouldn't be here without the mountain snowpack and the water that it provides. Yeah, I guess both sides, awareness of dust and awareness of the importance of snow. And if we can contribute to policy that mitigates dust and helps retain our snowpack, then that's great.

Julie Kiefer: So, we're so fortunate to have the beautiful Wasatch Mountains in our backyard, which is a perfect laboratory for studying snowpack. And I've seen really cool pictures of your research site at Alta Ski Resort, which by the way, received a record 903 inches of snow this winter! For our listeners who maybe haven't seen these pictures, I mean, can you describe your outdoor research lab and the challenges of working during this epic snow year this year?

McKenzie Skiles: Yeah. So, we installed instrumentation at Atwater Study Plot when I first began at the University of Utah. So, we're going on six years of observations and the instrumentation that we put up there is measuring all of the factors that control snow accumulation and snow melt. So, it really is an outdoor laboratory.

We have instrumentation out there that's measuring stuff like air temperature, wind speeds, sunlight, continuously. And then we go up in the wintertime and dig snow pits all the way to the ground, measure snow properties and collect snow samples to supplement those instrumented observations. And normally we see snow depths on the scale of maybe 10 feet, 12 feet or something, and those snow pits are relatively easy for us to dig all the way to the ground to make observations. But this past winter, our snow pits exceeded 15 feet. I think we reached 18 feet in one of them.

Julie Kiefer: That's a lot of work.

The Atwater Study Plot at Alta Ski Resort.

McKenzie Skiles: It is a lot of work. It takes hours to excavate all of the snow all the way to the ground. The snow pits have to be bigger because you have to dig steps into them. Myself and my graduate students got a lot of exercise this year digging snow pits because we take those observations once a month during the winter when snow's accumulating, and then weekly when snow is melting. So, it's a lot of snow pits.

Julie Kiefer: Wow.

McKenzie Skiles: That's a lot of work to dig all the way to the ground. When we went up in June and all the snow was finally depleted, it was really nice to be up there and not have to dig any snow pits.

Julie Kiefer: And so what do you do when there's no snow? What does a snow lab do when there's no snow?

McKenzie Skiles: Yeah, we have a lot of work to catch up on. All of the snow samples that we have collected in the wintertime get stored in a cold storage room in my lab. And then during the summertime, that's when we pull all those snow samples out, we melt them down and we analyze for dust and other things that we might find in the snow, including soot or black carbon, which comes from urban sources and that’s also a dark particle that can accelerate snow melt. So we analyze the snow samples for all of these different things and that takes all summer.

 University of Utah civil and environmental     engineering assistant professor Carlos           Oroza (left) and U geography associate professor McKenzie Skiles.

Julie Kiefer: Wow. And so do you have other research sites in Utah and outside of Utah?

McKenzie Skiles: We have supplementary sites, what we call auxiliary sites, in Utah that don't have all of the instrumentation that we have at Atwater, but that we visit to dig snow pits that we can compare to what we see at Atwater. And that's just to capture spatial variability and see how processes are different across the Wasatch. And then we also have a number of sites in Colorado. A lot of the work that my lab does focuses on the Upper Colorado River Basin and the water resources that come from snow into the Colorado River, and that's all over Colorado, including Grand Mesa, Crested Butte, Silverton down in the San Juans. So, sort of spanning the Colorado Rockies.

Julie Kiefer: And so what's in store for the future for your research?

McKenzie Skiles: Yeah, we are working on some very big projects right now that would bring this  process-based snow melt modeling to water forecasters across the Western U.S., not just here in  Utah or in Colorado. And we're really trying to shift the way that water forecasting is done to focus more on the actual processes that control snow melt. So, we're working on these big modeling projects and also utilizing satellites to look at snow cover, snow cover trends, see how snow cover is changing over time and if we can use that to forecast how snow will change into the future.

Julie Kiefer: Do students have an opportunity to work in your lab?

McKenzie Skiles: Absolutely. We have undergraduate research opportunities through the Undergraduate Research Opportunity Program, UROP, and then also funded opportunities to do snow sample analysis, satellite image analysis. There are plenty of opportunities and if students are interested, they should get in touch with me.

Julie Kiefer: And it sounds like this work is really multidisciplinary. Do you collaborate with other parts of the U?

McKenzie Skiles: We do. We have collaborators in the Department of Atmospheric Science. They help us understand where the dust is coming from, doing modeling of dust emission and transport. And then also in civil and environmental engineering, we're working between departments to improve snow melt modeling in the West.

Julie Kiefer: I just have a curiosity question, though. You are looking at dust from different sources on the snow. How do you know where the dust is coming from?

McKenzie Skiles: Yeah, so we do back-trajectory modeling, which essentially uses our study plot where we're measuring the snow as a receptor site, is what it's called. And then we can use numerical weather prediction models to trace back where the air mass came from that arrived at that receptor site, and then look at where that air mass traveled over. And we have this land surface model with all different vegetation and land surface classification types. And every land surface has what's called a threshold frictional velocity, which is essentially the wind speed at which dust could be emitted and picked up and moved.

And so when the wind speeds exceed that amount, then the model says, okay, dust is being produced from this area. And we actually had to adapt the land surface model to accurately reflect the Great Salt Lake lake level because if it's not updated, the lake is changing so quickly from year-to-year that if it's not updated, the model will show it as having water and not just dry lakebed. So, we updated the lake levels within this model and also used measurements from somebody, I don't know if you know who Kevin Perry is in the atmospheric science department. He actually goes out and measures the wind speeds that it takes to get the dust emitted from the dry lakebed. So, we use his measurements constrained in the model when dust would actually be getting produced from the dry lakebed.

Julie Kiefer: McKenzie, this has been really fascinating and I look forward to hearing more about your research in the coming months and years. And thank you very much for being my guest on U Rising.

McKenzie Skiles: Yeah, thank you for having me.

Julie Kiefer: Listeners, that's it for today's episode of U Rising. Our executive producer is Brooke Adams and our technical producer is Robert Nelson.

I'm Julie Kiefer. Thanks for listening.