This post provides an explanation on why permafrost can cause sink-wholes and destroy construction; plus at the bottom of the post, you find the description of today’s look: A tulle skirt with utility jacket outfit idea.
- Definition of permafrost and plugins
- Impact of permafrost on construction and vice versa
- Permafrost has damaged this parking lot
- Where do sinkwholes built in permafrost?
- What are the causes of permafrost damage?
- How does this degradion of permafrost work?
- How the damage is fixed
- What happens in undisturbed discontinuous permafrost?
- Tulle skirt with utility jacket outfit idea
Disclosure: There are affiliate links in this post.
Definition of Permafrost and Plugins
Permafrost is defined as a soil layer that stay frozen for at least two consecutive years. The layer above the permafrost starts thawing every spring and refreezes in fall. This layer is called the active layer. In this layer, plants can root and grow. Obviously, the deeper this layer is, the taller vegetation can grow. Consequent, you can recognize permafrost by the look of the vegations as described in the linked post.
What’s a plugin? These are the gray polls with the outlets on the side shown in the photo below. They are needed so your car starts when temperatures are in the double negatives. Check the link for more information.
Impact of permafrost on construction and vice versa
Permafrost is a pain in the neck for any construction. I have written about the relationship of damages from houses built on permafrost vice versa some time ago. Furtermore, permafrost can cause problems when drilling for drink water and can be the source of artesian wells that sprout water even in the middle of winter.
Permafrost has damaged this parking lot
Today’s post is about an annual annoyance by permafrost in the back parking lot of the Geophysical Institute at Alaska’s first university. Nearly each year, students, staff and faculty receive an email from the operations manager that part of the parking lot is closed due to permafrost damage. One year the damage was even so large that you could have easily hidden a car in the whole caused by the permafrost damage.
Where do Sinkwholes Built in Permafrost?
Not entire Alaska is underlain by permafrost. The Fairbanks region, for instance, is an area of discontinuous permafrost. This means there are areas with and without permafrost underneath. Typically south-facing slopes have no or only few small areas with permafrost, while north slopes have a lot or are totally underlain by permafrost. This distribution is due to the amount of insolation an area receives. As you have experienced yourself at the beach, once there is shadow it’s your skin heats up less than when there is no shadow. The heat from the sunshine is conducted into the ground. Heat conduction is the transfer of heat by the molecules of the material. You well know this physical process from your iron pan’s iron handle that gets hot when you fry your breakfast eggs.
What are the causes of permafrost damage
In case of the parking lot, it is located at the top of a north facing slope. Prior to the area’s becoming a parking lot, it was covered by trees and vegetation. When the lot was paved, it was cut off from water supply by rain and snowmelt from the top. This means that now evaporative cooling doesn’t occur anymore at the top of the soil layer in summer. Furthermore, the pavement heats up much stronger than wet soil and/or vegetation. During summer more heat is transferred into the ground underneath the paved parking lot than it was when the lot was still in its natural condition.
How Does this Degradion of Permafrost Work?
Over time, this enhanced heat transfer increases the depth of the active layer underneath the pavement. The water in the active layer can’t evaporate and stays there until it finds a way to flow away. In this case, the soil layer with a sudden looses part of its mass. Large soil grains and stones remain, while the water takes away small grains (silt). Once the water flows away, the modified soil matrix collapses. The remaining grains and stones sink into the space that formerly was filled by a mixture of frozen water, soil material, and stones. In this process, the pavement, of course, sinks down too.
How the Damage Is Fixed
The next thing is the closure of the area as shown in the photos and said email is sent. In the following, the parking lot is repaired by filling the sink-whole and repaving the area. However, depending on the size of the permafrost lens underneath, it is just a matter of time when the next permafrost damage will occur due to heat conduction into the ground.
What Happens in Undisturbed Discontinuous Permafrost?
Thus, why didn’t the area collapse with the natural vegetation? I don’t know whether it didn’t happen in the area of the parking lot prior to the land-cover change. Unfortunately, I couldn’t find any information about it whether this area was a sinkwhole before. However, in general, the shadows of trees reduce the potential heating of the ground. You surely have experienced as a kid when running around bare feet that grass doesn’t get as hot as pavement. For these reasons, the heat from sunshine does not penetrate so deep into the ground by conduction as it does under the same sunshine conditions in the paved parking lot.
Of course, you can find places where a permafrost lens collapsed in a hot summer underneath vegetated areas as well (see photo above). These sink-wholes are the reason why many lawns in the Fairbanks area are not plain as the lawn in a German soccer stadium, but bumpy up and down like a test and practice path for mountain bikers.
Aren’t these sink-wholes amazing? What damages does nature cause to constructions in the area you live? Let me know, I am curious.
Tulle skirt with utility jacket outfit idea
Now let’s discuss the look of today. I went for a monochromatic look in blush with a midi tulle skirt, utility jacket and slides. The outfit creates a feminine vibe colorwise, but is “toughened up” with the utility jacket and slides. I wore it as an unexpected Casual Friday look without jeans.
Mölders, N., 2010, Land-use and land-cover changes: impact on climate and air quality, Springer Science & Business Media
Mölders, N., Kramm, G., 2009. Permafrost modeling in weather forecasts and climate projections. In: Krugger, M.I., Stern, H.P., New Permafrost and Glacier Research, Nova Science Publishers Inc., New York, 51-88.
Mölders, N., Romanovsky, V.E., 2006. Long-term evaluation of the Hydro-Thermodynamic Soil-Vegetation Scheme’s frozen ground/permafrost component using observations at Barrow, Alaska. J. Geophys. Res., 111: D04105, doi:10.1029/2005JD005957
PaiMazumder, D., Mölders, N., 2008. Sources of discrepancy between CCSM simulated and gridded observation-based soil-temperature over Siberia: The influence of site density and distribution. Proceedings of the Ninth International Conference On Permafrost, Fairbanks, AK, 1351-1357
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Photos of me: G. Kramm
Photos of permafrost damage: N. Mölders
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