A conversation with graduate student Danielle Perrot about hydrological research aided by Wingscapes time lapse cameras
Watching snow melt might sound as dull as the proverbial drying paint, but Danielle Perrot sparks with enthusiasm about the impact of dust and pine needles on the finer details of how and when snow turns into water. Perrot is a graduate student at the University of Colorado working at the Institute of Arctic and Alpine Research, and Wingscapes recently reached her to learn more about her research.
Q: Why are you interested in melting snow?
DP: The mountain West depends heavily on snow melt for water resources. I’m from California, and I grew up skiing and spending a lot of time in the mountains when I was a kid, so that’s how I originally got interested.
I’m a snow hydrologist, but I like to think that I also do some eco-hydrology in the sense that I’m studying the interactions of an entire ecosystem, in terms of plants — in my case, trees — and snow melt. In the past, I’ve studied the effects of the mountain pine beetle [and the resulting dead trees] on snow melt, and my data had this dust layer in the snowpack that I was not able to incorporate into my modeling.
So I became really interested in how dust deposition in forested areas is affecting snowmelt. There’s a lot of research being done in alpine areas, particularly in Southern Colorado, but not a lot in forested areas.
Q: Is global climate change one of the factors driving your research?
DP: There are a lot of scientific questions about the effects of global climate change — if we have warmer winters, what’s going to happen to our snowpack? That obviously impacts our ecosystems.
For instance, some recent studies have shown that the mountain pine beetle’s life cycle has been extended because of warmer temperatures in the winter. That allows the beetle to reproduce more and infest more areas, and my colleagues and I are finding that when you have defoliation of the trees, you increase the energy the snow receives in the sun’s shortwave radiation, so that by itself helps increase snowmelt rates. But when you lose forest canopy, that material has to go somewhere, right? What we’re seeing is that it goes onto the snowpack in the form of dead needles. It decreases the reflectivity of that surface, which is called the albedo, and when you decrease albedo, you have more sunlight being absorbed by the surface and still faster melt rates.
They’re seeing the same thing in alpine areas with dust deposition. What I’m really interested in is how the albedo of dust on snow may be different or similar to that of needles on snow, and what happens when you have both.
Q: What do your experiments entail?
DP: We have a test plot at the Niwot Ridge Long-term Ecological Research site, which is maybe 40 minutes outside of Boulder, Co. We don’t get a lot of natural dust deposition here, so we have a lot of control over how much dust we want to put on our snow surface. We have snow and air temperature sensors at the site and will be measuring albedo with an albedometer.
Since lodgepole pines are the primary species the beetles infest, we collected a bunch of lodgepole pine needles from under beetle-killed lodgepoles, weighed them, and got an average mass for the samples that we’re putting on the snow surface.
Last year, we were crushing up rock dust for hours and hours in the lab. Luckily this year I was able to find a company near Boulder that makes things out of exactly the same stone I was crushing. A byproduct of their work was this dust, which they donated. That was really helpful!
We deposit known amounts of dust, litter, or dust and litter on the surface in strips. Then we can see how that known concentration of dust or litter is interacting with the snow once it’s buried in the snow pack or comes back to the surface.
This year, we first deposited the dust and needles at the end of February. Since then, we’ve been going up once a week and monitoring how the snowpack layering is changing, how the different grain sizes are changing, and where we’re seeing the most melt.
Q: What results have you observed so far?
DP: We did this first deposition right before a big snowstorm, which is typically when you see natural dust deposition events, and we tried to mimic that. But it’s been uncharacteristically warm here for about the past two weeks. It’s March, and you’d expect that kind of weather in May. So we’ve seen really big, abnormal melt rates that we weren’t anticipating this time of year. We’re hoping it will snow and get cold again and that we can do another deposition event so we can see how those layers will interact.
What I’m seeing right now is a little difference between a dust layer and a needle layer in the snowpack. The dust layer causes a lot of melt and then refreezing around it, which creates a barrier in the snow pack. I’m not seeing that so much with the needles.
Q: And how do your measurements translate into snowmelt, water flows, and, ultimately, drinking and irrigation water — or floods?
DP: We make discreet temperature measurements in the snowpack at every 10 centimeters, and those correspond to density measurements we take of the snow. From that we can determine the liquid water content of the snow pack, and that’s what people care about when planning hydrological flows and water resources.