1. Natural Snowpack Vs. Human Disturbed Snowpack in the Subalpine
Brittany Engleking
Winter Ecology
Spring 2010
Mountain Research Station-University of Colorado

2. 22
Introduction:
Purpose: Analysis/observe snowpack changes once the snowpack has been disturbed.
Background: Digging snow pits disturbs the pack
Why/Objectives: Harmful to ecosystem? Animals/Soil
What we already know:
Purpose: To analysis and observe how the snowpack changes over time once the snowpack has been disturbed.
When you dig snow pits you disturb the snow to a great extent, from piling up snow to completely exposing the ground.
Hypothesis: Once the snow pack is disturbed it won’t form back the same so the layers will be different than of the undisturbed snow and more hard packed.
Subneiven layer effects ecosystem- animals have to go on top of the snow instead of burrowing through it.
Gives the animals and soil a stable environment
Snow profiles are typically used to look for weak layers in the snow to know the avalanche danger of the snow pack.“These observations provide a historical framework and general guideline to trends in snow pack stability.” (NWAC) But when you disturb the snow this is no longer the history of snowfall in an area because people have messed with the structure. If a snow pit were dug in an area where someone had previously they might not get accurate information compared to the surrounding snow that they will be skiing on.

3. Methods: Site: Open exposed ground surrounded by conifers. 1. Supplies33
Methods:
Site: Open exposed ground surrounded by conifers.
1. Supplies
2. Setup
3. Record Data/Observations
Now leave this area alone for a couple of weeks… (in my case I collected data 2 weeks later then 1 week after that)
First once you get your supplies (snow kit, shovel) dig a snow pit in an area where snow has not yet been disturbed and record data, such as depth, temperature (in the middle of every 10 cm and the top/bottom and air), and density.
Look at grain shape and size at the different layers of the snow pack.

4. First Week Snow Profiles:
The Results of the first week:
Air temp: -7 degrees C
Cloudiness/ Insolation:Partly cloudy
Precipitation: Light/little snow
Surface Hardness: 5 (2mm of soft)
Wind: 5-20 mph
73 cm was the deepest snow pit which was located on the top (if coming from the lodge) of the trench we dug closer to the trees.
The Second profile is closest to where I dug the rest of my snow pits.
Depth: 62 cm
# of layers: 7 layers Mainly ET to TG
Harder-to-softer-to-harder again
Largest grain size 4 mm

5. The Second Week: Come back to the same site55
The Second Week:
Come back to the same site
Test the undisturbed snow for comparison.
Dig two more snow pits:
Middle of Trench
Middle where we had piled up the snow: (near pit #2 from the first week also)
Where we had previously dug to the ground had filled in with snow better where it was shallow before and not as well where it was deeper. Also, there were signs of wind blown snow which could have been the cause of our trench filling in since there wasn't much new snow. In the middle of the trench where we had previously dug to the ground (next to the second snow profile site), there was really hard snow on the bottom that was hard to dig out and hard to test the density (had to use the mallet).
Air Temp: -5 degrees C
Cloudiness/ Insolation: Mostly cloudy
Precipitation: None
Wind: None
Surface Hardness: 5 (Fist)

6. Two Weeks Later:
Middle of Trench: The hardness went from a 5 to a 1 at the bottom and only the top layer was ET, the rest TG and the snow grain size never got over 2 mm.
Depth: 35 cm
Had some error this data because I didn't take temperature and density at the right intervals but we can still see the general trend of the pack.
Middle where we had piled up the snow: (near pit #2 from the first week also)
Depth: 58 cm (was 62 cm where we took the profile and we had piled snow behind us in an area about the same depth or less, this is an area of uncertainty in my project, if I were to do this again I would have recorded the snow depth before we piled up snow on that location and immediately after to better compare the changes that occurred) A difference in this pile that I noticed was that is was not covered with a fresh softer layer on the top like the other pit I dug. Also, the first two layers were ET already showing signs of rounding/TG starting to occur. This pit did not have a hard layer on the bottom like the previous one and the hardest layer was a 3 (1-finger)
Lastly I dug a pit where we had previously left alone as a sort of control. In this pit I got the same basic pattern as the pits from the first week and I took data around the middle (by pit #2 again kind of by pit #3 too). I did not find the ET/TG layer around the middle though.
Depth: 67 cm (previously 62 cm at pit #2 from the first week)
The hardness goes from 5 at top to about 2 on the bottom. The first 3 layers were ET then TG the rest. Also, there was a general pattern of increasing snow size from 1 to 5 mm (like that of pit 3)

7. 3 Weeks Later:
3 weeks since original snow pits: 2/13/10 around 11:00 AM
Air Temp: -4 degrees C
Cloudiness/ Insolation: Mostly cloudy but less so than the previous Saturday
Precipitation: Some blowing snow
Wind: Yes but not too strong
Surface Hardness: 5 (Fist) Super Soft
General:Appears snow has drifted into the hole where we had dug to the surface on the first week even more so than before. Still has not completely filled up the trench, and you can still see the mound where we had pilled the snow on the first week.
I dug a pit next to where I believed I had the week before in the area were we had dug to the ground. but it was hard to tell because of all the new snow added. This was to see how the snow has changed in 3 weeks since we had first did our tests and not just from my work the pervious week. The bottom of the pack was still very hard there and hard to reach the ground. The top 22 cm seemed very fresh and soft, new accumulation in that area some might had been blown in too since there was some wind and blowing snow.
Depth: 56 cm (compared to 35 around same area last week)
The snow size stayed between 1 and 2 mm and went from ET and a softness of 5 to TG that was rounder not as crystal like as I had seen before (possibly going back to ET?) and a softness of 1.
The spot I had dug up the last week (in the middle):
This spot had already filled up a lot , 56 cm, from one week ago and was very hard to tell where it was at so I really just had to use my best guess which I think was pretty accurate. I know that we did not get 56 cm of accumulation so much of it must has blown into the pit since the previous week. The layers were different from all the others in that it went from ET on top to TG, back to ET, then a more rounded out TG. Snow sizes all between 1-2 mm. It was similar to the snow pit that was 2 done 2 weeks after digging to the ground in that it was very hard at the bottom (Hardness: 1), and still not as deep as the surrounding snow.
Control (in the middle previously undisturbed):
Depth: 64 cm
From ET on top layer only to TG and a hardness of 5 to 3 at the bottom and a very easy to see temperature gradient. Also, like before there were layers near the bottom of really sugar snow with big crystals up to 4 cm.

8. Conclusion:
Disturbed snow had no TG on bottom=no subnevien space for animals
Animals must move along surface=exposed to predation
Also, snow pits where we dug to the ground where shallower than the rest of the snow and the sites were still distinguishable from the surrounding snow even 3 weeks after wind and more accumulation.
Humans had an impact on the snow pack by making it shallower, harder, and they layers of snow varied in composition from the undisturbed snow (from ET to TG in the undisturbed snow pit to layers that even had ET on the bottom in the disturbed ones)

9. Conclusion (count.) Shallower snowpack
Different layers than surrounding snow
Confusion of what the weak layers are if testing for an avalanche
Soil under/where snow used to be effected-colder/no longer a stable environment

10. Questions?

11. Literature Cited:
Snow Profiles for the 2009 / Season. Northwest Weather and Avalanche Center. < pits/current/>