Why Snow Matters

A snow drought happening across the western U.S. is creating dramatic shifts. In this episode, we spoke with Dr. McKenzie Skiles, Director of the Snow Hydrology Resarch-to-Operations Laboratory (Snow HydRO Lab) and associate professor at the School of Environment, Society & Sustainability at the University of Utah. Dr. Skiles specializes in snow monitoring, modeling and remote sensing, and investigates the impacts of mineral dust and other light-absorbing particles on snow. She explained why changing snowfall and snowmelt patterns have implications for recreation and water security in the west.

To learn more about Dr. Skiles and her research, visit the Snow HydRO Lab webpage here. 

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Transcript

Why Snow Matters

Sarah: Welcome to Come Rain or Shine podcast of the U.S. Geological Survey. Southwest Climate Adaptation Science Center, or Southwest CASC 

Emile: and supported by New Mexico State University and the University of Arizona. We are your co-hosts, Emile Elias 

Sarah: and Sarah Leroy. Here we highlight stories to share the most recent advances in science, weather and climate adaptation, and innovative practices to support resilient landscapes and communities.

Emile: We believe that sharing some of the most innovative, forward thinking and creative scientific research and adaptation solutions will strengthen our collective ability to respond to even the most challenging impacts of climate change in one of the hottest and driest regions of the world.

Emile: So today we're speaking with Dr. McKenzie Skiles. She's the director of the Snow Hydrology Research Operations Lab and an associate professor at the school of Environment, Society and Sustainability at the University of Utah. Dr. Skiles’ research and expertise focuses on how much water is held in the snow, how snow is changing over time, and how dust and other light absorbing particles impact snow in the western United States.

Welcome Dr. Skiles. Thank you so much for being with us today. It's fun to talk with a familiar person on this podcast, and I just want to learn about your path. So can you start us off with telling us how you ended up studying snow? 

McKenzie: Sure. Thank you so much for having me. First. And yeah, I grew up in Anchorage, Alaska, and growing up I noticed a lot of changes going on around me.

There was less snow cover. There were, you know, rapidly melting glaciers and more broadly across Alaska, you know, the permafrost was melting and people's homes were basically falling into the tundra. And I knew that I wanted to study climate change, and I didn't know exactly what route that was going to take. And I was also skiing a lot, and so I chose University of Utah for my undergraduate because I knew there was close access to snow, and it was a great school. And as I was sort of exploring what I wanted to do, I found mapping and GIS as a really powerful way to explore change. And originally that sort of took the avenue of vegetation change, and then I – totally separately– was doing avalanche work and training to be in like, snow safety, and that was kind of two separate paths. And then I met my graduate advisor, who was a snow hydrologist, and that kind of changed everything for me. I didn't know that you could have that as a job. And so I switched gears and started doing fieldwork with him, and the combination of being able to study change and also be out in the snow was just a really great combination. And and I've been doing it ever since. 

Emile: I love that your path was not entirely direct, right? You followed your passion and you knew that there was something you wanted to study related to climate change. But then you went a variety of ways looking at vegetation and then kept your passion around skiing and snow, and that's how we're led to you now.

And I think that's a similar story for a lot of scientists, is just the path is not always a direct one. So that's fun. And you already hit on this a little bit, but I think you might be able to expand on what scientists, what trends scientists are observing in terms of snowpack and snowmelt runoff across the western United States.

McKenzie: This is a particularly relevant year to be discussing this, because across the western U.S., we're in a pretty dramatic snow drought right now, and I think it's really emblematic of what is happening more broadly in terms of snow. And that is that when we do get precipitation at lower and mid elevations, it's falling as rain rather than snow, and that is a challenge because we live in a semi-arid environment, and when you get it as rain, more of that water goes to the atmosphere, plants, soils, rather than getting stored as snow. And so that is one thing we're seeing. We're accumulating less snow at the start of the season, leading to shallower snowpacks. And then during the melt season, with land use change and surface disturbance, we see increasing levels of dust in the western U.S. and dust is deposited on the snowpack, making it darker and accelerating melt.

And so it's a double whammy. We're getting less snow in the first place, and we're getting faster melt in the spring and summer. But, that being said, there's also a component of variability in all of this. And so some years we're still getting really big winters and a lot of precipitation is snow. And then some years like this year, we're getting almost none at all. And so there's just really dramatic shifts. But overall we're seeing less snow-covered area, and that has implications not just for water resources because that's where most of our water comes from in the West, but also regional climate – because snow is so bright, it reflects a lot of incoming sunlight. And as we get less of it, darker underlying surfaces are exposed for longer.

And that also has implications. So it's both hydrology and climate that are being impacted. 

Emile: As I mentioned in our intro, you lead a lab at the University of Utah that focuses on research and operations around snow hydrology. And so can you tell us a little bit about the lab and some of the research that you're conducting?

McKenzie: Yeah, we have a lot of exciting stuff happening in the lab. And my vision when I first started it was to be able to carry out cutting edge research, but also be able to translate that into useful tools that benefit people outside of academia. And so we do a range of research from sort of, fundamental research to applied, and that can look like, you know, we have one project right now where we're putting out more instrumentation sites to observe the energy balance of snow. So that's on the side of longwave radiation and and solar radiation that's not measured at traditional snow observation sites, but measures the type of information we need to model mountain snowpacks. And then we can take information like that and build it into these distributed models where we're running simulations about snow accumulation and snow melt over, you know, the entire headwaters of the Colorado River basin.

And in those distributed models that we're running at big scales, we also integrate remote sensing information to inform about current conditions. And so the gamut of research runs from observations to remote sensing to numerical modeling, and then interacting with stakeholders to understand how we can make or co-develop tools that are useful for them.

Emile: Excellent. Thanks. And this leads perfectly to the next question, which is around the operations part of your work. So how does the research impact operations and what types of managers are you working with? 

McKenzie: We work very closely - our closest stakeholder partners is the Colorado Basin River Forecast Center, and they themselves have numerous stakeholders that they are providing forecasts to. And working with them makes a lot of sense, because my research has really focused in the upper Colorado River Basin and Great Basin, and that's their forecast region – and those areas are heavily snowmelt dominated. And so when I think about operational partners, it's anyone who is working in an applied science, who's providing, who's taking information and then providing it to others outside of the ivory tower, the academic world, providing useful, applied, practical information. And that primarily means for my group, people that are actually producing operational hydrologic forecasts. And we're thinking about, you know, how we can provide information like remote sensing information that's useful for them, but also how we can transition operational models or research-based models into operational environments.

And that's not as easy as it sounds, because in operational environments, they are beholden to provide as accurate forecasts as they can and change can be quite slow because you want to be using methods that are reliable and known. And so, often it takes many years or even decades to test new approaches and assess if they're useful. 

And so the current way that snowmelt is forecasted in the western U.S. is statistically based. It uses these long calibrated records. And in the face of climate change, errors can result when the conditions in the current year are outside of that calibrated record. And so our goal is to get process-based modeling that doesn't rely on these long calibrated records into the hands of operational users and make it a seamless transition, not put the load on them to understand how to run these models, but to make them easy to run and integrate into operations.

Emile: And how are the managers responding to that? Because I know they're very busy. They do have this long tradition of sort of entrenched ways of evaluating things in a pretty contentious water system. And so I think that – I'm sure – that there would be a lot of interest in integrating more information or different ways of looking at the same problem.

And so I'm just wondering if you've had any success or stories around ways that people are using and integrating that information yet, or if it's just a long process of conversations and evaluations? 

McKenzie: Yeah, it is a long process of evaluations and conversations. I started this process when I started at the University of Utah eight years ago, talking to the Colorado Basin River Forecast Center, understanding how their operations work and how we might be able to fit aspects of our process based modeling into their current framework.

And just in the last few years, we have the model running in-house, for them to evaluate. And so it takes a while. And, you know, currently, the way that we approach that is that it's not replacing the current way that they forecast snowmelt. It's just an additional piece of information that they have that they can look at and review.

And in potentially basins where the snow is not behaving as we might expect, they have this other piece of information that they can look at and take into account. And I think that has to be the first step. They get to evaluate it and see if it's useful. And we hope, we hope it is. In order to facilitate that, I have had researchers from my group actually sit in their office and work with them, because they are busy and we can't expect them to just know what's going on in the research world and take it up and apply it themselves. That's just not practical. They're worried about providing accurate forecasts, and so the more that the research world can do to help facilitate that, I think that's a really important and potentially overlooked part of research. Like you want to be doing useful applied research, but you can't just do it and then and put it out in the world and expect them to take it up.

Emile: Right, exactly. Well, that's really exciting that they are, you know, that the model’s now being used, or at least, working in their office. So that's great. Congratulations. And so you mentioned this before, but I want to take a deeper dive on this topic. A lot of your work has focused on the impacts of dust on snow across the western United States and I'm wondering if you can give us an overview of the research, but also, you know, what are the sources of the dust and how specifically and where specifically does that impact snow melt? And, then how does that integrate into impacting water supply? 

McKenzie: I will go back to how I got into this and got started. My first field season was in the San Juan Mountains of southwestern Colorado in 2009, and I remember going out multiple times that season, and the first couple times the snow was clean and that, those mountains are just like the, the they are some of my favorites. They're they're beautiful and they're remote, and you really feel just how much water we can get from snow when you're there. Because you look out and there's just these huge peaks and they're all covered in snow. And then after our first couple visits where it was, you know, exactly what we picture is snow covered peaks. We went back and and the mountains were blanketed in this really dark red dust.

And it's such a dramatic shift from this clean, bright snow to the mountains almost looking like they're covered in soil rather than snow. And, you know, I think that was a really interesting process to me. I wanted to understand it more and that is really the thing that got me hooked. And I wanted to compare the impacts of snow darkening from dust deposition to the impacts from climate warming.

And that sort of led down the research path that's defined the rest of my career. And what we found was that a lot of the dust was coming from regional sources, so relatively close to the southern Colorado Plateau. And work from colleagues tells us that modern levels of dust deposition are much more elevated than they were before modern settlement of the West.

So we can link the amount of dust we see today to human activity. And that first human activity that led to surface disturbance and soil erosion was grazing. So just widespread grazing across the West. And then the Taylor Grazing Act was enacted in the 1920s. And we actually saw a decline in dust. But then there's other activities that have led to surface disturbance, moving past that.

So, you know, everyone will be familiar with the Dust Bowl. So agriculture has led to dust. More modern oil and gas development has led to dust, just widespread sort of land use change. Any sort of surface disturbance makes soils more available for transport by wind and the removal of vegetation increases wind speeds at the surface. And so if you have removal of vegetation or surface disturbance, you make those soils more available for transport.

And we know that it's probably convolved a little bit with climate warming and drought, but that it's primarily linked to human activity and that there is a lot of variability from year to year. We see dust on snow deposition happening every year, but some years are really extreme, like 2009 when I first went out, that was one of the dustiest years over the time that we've been observing dust on snow, and we've had a couple other really extreme years since then, and we don't fully understand what causes those extreme dust years, which still makes this a really interesting problem to study.

We've gotten better at observing it. We can look at it from remote sensing. We can build it into models to understand the impact. But we still don't really understand exactly what is the driving force behind that. And that's really critical. That's the next step because dust on snow can advance snow melt by a month in normal years, but up to two months in these really extreme dust years and that shift in snow melt timing is critical because it decouples when water arrives from when we need it. So normally snow melt arrives at the start of the growing season when we can use it for irrigation, when landscapes need it for ecosystem health, and if we decouple and melt it too soon, we don't get to use that water in the most efficient way. And we're left with less water towards the end of the summer. And so understanding the processes that really drive that variability, that's what we're working on now.

Emile: I imagine that decoupling that you mentioned can have some pretty significant impacts on everything, but also on recreation or river-based recreation. And I wonder if you can speak to that. 

McKenzie: Yeah. So what happens with rivers is that you get earlier and faster runoff. So you still get a similar amount of water. You can lose a little bit more to evapotranspiration, but that earlier and faster runoff leads to lower flows in the mid and late summer.

And that can impact water-based recreation and fishing. With fishing, the temperatures get too high. It's not healthy for that ecosystem or the fish in a lot of places have restrictions on fishing when the water temperature is above a certain level. And so, you know, it just changes the whole dynamic of how we are able to interact with rivers.

And so it impacts us. But then it's also impacting the ecosystems themselves. 

Emile: Excellent. Thanks. And probably skiing too, when we're thinking about recreation in different ways. But so speaking of that, you work in some pretty harsh environments, some remote environments, and you need to get out into the field. So can you tell us a little bit about your field methods or how you reach some of the remote locations where you take measurements?

McKenzie: Yeah, the places where we do fieldwork are remote and we are frequently skiing into them. A lot of them are in areas that you wouldn't be able to access with something like a snowmobile or a track vehicle. We ski into them and we carry our equipment with us, either in backpacks or, using sleds that we drag behind us.

And typically when you go out, you know, you think about doing fieldwork for a couple of hours. And for us, it's rarely a couple hours. It's either an entire day or we spend weeks kind of out in the springtime. We're really interested in snow melt. And so we typically are doing these long field campaigns in the spring and we spend, you know, multiple days going around to different sites that are in the headwaters of the Colorado River basin and digging snow pits, collecting snow samples, taking other measurements with specialized equipment.

And we also, over the last couple of years, have incorporated drones into our field work. So we're carrying the drones out there and then flying them over our study plots to better understand spatial variability. So it's a really useful tool. But it's another thing that we have to carry. 

Emile: Can you describe a snow pit for our listeners, people that might not have seen one?

McKenzie: Yeah. So it is where you excavate the snow using a snow shovel that basically breaks down and fits in your backpack. You excavate the snow all the way to the ground, and you have one vertical face that is smooth, that allows you to collect observations of the snowpack from the surface of the snow all the way to the ground.

And we're observing sort of basic variables like snow depth, snow layering, snow temperature, and the type of snow grain - properties of snow grains - that are in those layers. And you can imagine that if you dig all the way down to the ground, that there's these different snow layers that are basically like a record or a library of all the different precipitation events that have happened over the season.

And each one of those layers looks a little bit different, has slightly different properties. And so we're recording those properties. And then we're also collecting snow samples that we bring back to the lab. And we can analyze for things like dust or black carbon or algae, those darkening aerosols that we are concerned about in terms of snowmelt rates.

Emile: Excellent. Thanks. So most people that do field research have some harrowing stories about things that happened in the field. We've certainly had some people on the podcast before that have some exciting stories about different aspects of field research. So do you have any stories that you'd want to share? 

McKenzie: Sure, in the field site that I visited the most - it's the one that's in the San Juan Mountains that I first started doing field research at – during my PhD, I was really fortunate to get the opportunity to live by that field site and do snowpit observations every single day, from when there was the most snow on the ground until snow melted out. Basically, we just really wanted to do detailed study of the processes controlling snow melt.

So it was my job to go and dig a snow pit every day, make observations, and then also I was doing measurements with an instrument called a field spectrometer. And that measures incoming sunlight across all of the wavelengths. And so it gives you this unique spectral signature or fingerprint of snow and how it's reflecting sunlight. And that instrument is not light, but you can bring it in on a backpack. And so when I was leaving the field site for the day, I had a bunch of snow samples and a field spectrometer in the backpack. And it was late season and the snow was just coated in dust, and it was a pretty high dust year. It was 2013. And you know, when you get enough dust concentrated at the surface, it's almost like you're not skiing on snow anymore. It's like you're hitting soil. And so I was skiing with this heavy backpack, and I was on tele skis, and I hit one of these patches and my ski just stopped and I kept going forward and broke my bindings, and I landed on the edge of my ski with my knee. And just sliced it, sliced it open.

And I was at a bit of a loss of what to do, because I didn't want to leave this expensive research instrument in the field. But I couldn't carry it out with me. And I think about it now, and it's funny that I was more worried about the instrument than my knee, but I sort of stashed it and my broken skis behind a tree and then had to walk out, basically like postholing through the rest of the snow, which was excruciating.

Get to my car, drive down to Uray, Colorado, where there's not really a clinic. And I at that point had lost a lot of blood and had to have a neighbor drive me down to Montrose, Colorado, so I could go to the emergency room. And so that was sort of a traumatic event that relates directly back to what I was studying - the dust kind of got back at me, and ultimately was fine. I got staples and was able to continue doing field work after a couple of weeks. 

Emile: That's amazing that you were able to continue doing the field work after that. Yeah. You're not alone. Scientists always think about their equipment first, how they're gonna put that out. Well, so that just speaks to how difficult it is to get field data, right.

It's I mean, it's really important. It's critical you're out there, but it's hard. And so there are other methods, other ways of using information and collecting information. You mentioned using drones, but you also use other types of remotely sensed data. And so I'm curious what types of remotely sensed data you use, to augment the field data that you collect and how that's expanded our understanding of snow-related research.

McKenzie: So when I first started doing field work, it became obvious to me very quickly that there's a lot of spatial variability. Snow is not the same in every place you go, and that's controlled by so many factors. It's controlled by terrain, by vegetation, by variable wind speeds. There's just so many variables that go into the complexity of snow in mountain environments that we can't make enough observations by hand to actually record all of that variability, to really understand how much water is held as snow in the mountains.

And so we need remote sensing to fill the gaps between observations and landscape-scale processes. And there's a lot of people doing exciting remote sensing work for snow across different technologies. But for me, I really focus on optical remote sensing. And that uses either reflected sunlight from the surface or LiDAR, which is an active technique that emits a laser pulse and then measures the reflected signal back, and from that, from LiDAR, we can map snow depth by flying, once when there's no snow, and then flying again when there is snow and we can take the difference between these basically surface pulses at different times to get at snow depth and total snow volume over watersheds. And the optical remote sensing part can tell us where the snow is and what the properties are of that snow at the surface. And I'll just say that it, you know, neither one of these is telling us all the information that we need to know. So we have to combine multiple sources. So the optical remote sensing that's from satellites, that can give us sort of daily snapshots of the snow when there's not clouds in the way, but it's relatively coarse. It's at 500-meter spatial scale. And so it's not giving us this really resolved image of the mountain snowpack. And then the LiDAR, that's being done from airplanes right now, and so you can get really high resolution information, but you're only doing it when you can go out and fly a plane. 

And so we can combine the satellite remote sensing which gives us this like sort of fuzzy picture about what's going on with ground observations and airplane observations to get a good understanding of what's going on with snow in the mountains.

Emile: Excellent. Thanks. And I wonder about glaciers. Do you do any work specifically on glaciers, and if so, what can you tell us about the glaciers you have worked on? 

McKenzie: I've been really fortunate to translate my work about dust on snow in the western U.S. to other environments across the globe, including glaciated environments. And what we're interested in with glaciers, is that, you know, if you get dust that lands on seasonal snow, it's going to melt out and you kind of start over again the next winter.

But on glaciers, whatever lands on them is staying there over time. And so it can accumulate over multiple seasons and get much darker. And when you have, you know, dark aerosols at the surface as the seasonal snow on the glacier melts out, those aerosols are exposed at the surface during all of summer. So I can have a much larger impact over a much longer time frame on glaciers.

And that is relevant for things beyond dust. It's also really relevant for fires. So fires happen primarily in the summer, and they're emitting ash and smoke and charred woody debris, and that can land on glaciers and stay at the surface of the glacier all summer, where it's sort of decoupled from when there's seasonal snow. So right now, the dark aerosols that are emitted from fire are the largest concern for glaciated environments.

And then there's also, when you get enough liquid water and nutrients at the glacier surface, you can get algae blooms. And people might know this as watermelon snow. It's sort of this like bright red snow. It can also be purple or green or even black. There's a number of different algae that will bloom but most commonly, I think most people would be familiar with this sort of pink or red snow.

And for seasonal snow that shows up right at the end of the season right before it melts out, doesn't have a huge impact. But on glaciers, it shows up mid-summer and stays. Those blooms just stay at the surface, making it darker, and the intensity and area of those blooms is increasing with climate change. And so that's something that we're keeping an eye on.

And could be an impact for glacier melt moving into the future.

 Emile: Sounds really critical and important to look at and interesting as well. Complicated stuff. So we're talking to you during this year where there's very low snowpack in a lot of the western southern mountains. So I'm thinking about Colorado specifically, where you did some of your PhD research, and it makes me think of cloud seeding, right, where communities are trying, like looking for solutions, looking for any way to ensure that there's more snow for that particular year.

And I wonder if you have any thoughts on cloud seeding or other solutions that people are looking towards to try to increase snowpack locally so they have water for the following year? 

McKenzie: Sure. This is an appealing engineering-based solution and I can understand why communities would pursue cloud seeding. What we know about cloud seeding now is that it can increase snowfall efficiency. So you get a little bit more snow from the storm when you're seeding with silver iodide. What we don't yet know is if that additional snowfall efficiency translates into more water. So when you get snowfall, a lot of things can happen to that snow. It can sublimate into the air. It can get taken up by soils or vegetation. And we don't know that threshold above which you need to get more snow to actually translate into more runoff downstream. That's the gap, right now with cloud seeding. 

And I'm actually a part of a project in Utah called Snow Scape, where we're trying to study that exact thing this season to not just link the atmospheric science side with a lot of observations of cloud seeding in the atmosphere, but with snow at the surface and stream flow, and see if we can connect all the dots, and if we can translate that increased snowfall into increased runoff.

And, if we're even able to do that with sort of one season of intensive operations, it might require many more seasons. Because one of the limitations with cloud seeding is that you need storms. And for the last month or more, we haven't had any storms. We've had this resilient ridge set up off of the West Coast, and we've just been under high pressure, no precipitation.

And you have to have a natural storm coming in to seed, in order to get that increased snowfall efficiency and so a challenge is, you know, with this adaptation strategy, is nature itself. We need nature to cooperate, in order for this to work. 

Emile: Thank you so much for sharing your research with us. Given the range of all of the different things you work on, what is the most exciting part of your work and what's the most challenging? 

McKenzie: The most exciting part of my work? I mean, I love all of the science I do and sort of pushing the boundary on what we can do with observations and remote sensing and modeling. But honestly, it's being an advisor to graduate students and training the next generation of snow hydrologists and scientists that are, you know, going to push the boundary even further and advance our science even more. I really, really enjoy being a graduate advisor. It's a fun part of my job. And it's nice to see them take an idea and, and make it their own and, and really run with it. 

And I think the, you know, the most challenging part of my job is just – and I think any anyone who studies snow and ice would say this – is that there's just sort of an aspect of grief in the work that we do. We're watching a resource disappear and we're not, you know, we're not just doing this for like sciences’ sake. We're measuring how quickly that disappearance is happening and what the implications of that disappearance is. And it can be challenging to understand if you can do anything about it. And what appeals to me about studying dust on snow is that it's quite actionable.

We can restore landscapes that produce dust and, you know, sort of have this immediate impact of keeping snow around for longer. That is a problem that I feel like can be tackled, whereas climate change just feels bigger and more nebulous and more challenging. And so I think that's an aspect that's challenging. But, you know, we can all just kind of do what we can. And for me that means understanding that change and making the way that we use snowmelt ultimately more efficient. 

Emile: Thanks for mentioning the grief. I think that's really important because it is a hard job and it comes up a lot. We actually on this podcast interviewed a professor who had written a book for students, actually, for people that you were talking about in terms of the opportunities or the exciting part of your work that's around that.

So we'll make sure to put the link to that episode in the notes to bring that up again, because I think it's important. 

Thanks for mentioning that. And if people remember only one thing from our conversation today, what would you hope that they take away with them? 

McKenzie: I would hope that people would take away one. The importance of snow cover. It provides up to 80% of our water resources in any given year, and then also as our main source of groundwater recharge.

So when you think about it, over 90% of our water is coming from snow, and that we understand the processes that are impacting snow change. And we are working to get methods into operational stakeholders to adapt to that change. But often when I speak to people outside of academia or removed from my world, they just don't understand how much water comes from snow.

And so thinking about how important the mountain snowpack is, and just paying attention to what's going on in any given year, and not just for whether or not it's good skiing, but also for our water resources. 

Emile: Dr. McKenzie Skiles, thank you so much for talking with us today. 

McKenzie: Thank you for having me. This has been a lot of fun.

Emile: Thanks for listening to Come Rain or Shine podcast of the USGS southwest CASC, New Mexico State University and the University of Arizona. If you liked this podcast, don't forget to rate or review it and subscribe for more great episodes!

Sarah: A special thanks to our production crew, Reanna Burnett and Lauren White. If you want more information, have any questions for the speakers, or would like to offer feedback, please reach out to us via our website.