Photo By Sgt. David Marquis | A recently opened thermokarst pit caused by the melting of ground ice in a region...... read more read more
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HANOVER, N.H., – As Alaska warms due to climate change, permafrost researchers at the U.S. Army Engineer Research and Development Center’s (ERDC) Cold Regions Research and Engineering Laboratory (CRREL) Permafrost Tunnel Research Facility are working to address challenges with building on permafrost.
Dr. Tom Douglas, a senior science technical manager with ERDC, has been studying snow, ice and permafrost for 20 years, and while he does not consider himself a climate change scientist, the things being impacted by climate change put him in that world.
“Permafrost is a good bellwether for climate change, because it's either frozen or thawed,” said Douglas. “Though that sounds simple, the different processes that lead to that happening, like warming climates, increased fire, changing snowpack or a longer summer season — when those are altered by climate drivers ― can affect the stability of permafrost,” said Douglas. “It's really easy to measure permafrost instability; we can track it.”
The United States’ “Last Frontier” is the nickname for the state of Alaska’s permafrost — earthen material like rock, soil, ice or organic matter that remains frozen for multiple years and found beneath nearly 85 percent of the state. Frozen ground is typically very strong; however, as the ice in the permafrost begins to warm, it weakens, and foundations may begin to fail.
The permafrost tunnel is used to study a broad variety of things, and climate change is one of them. There's a lot of infrastructure work that's done in the permafrost tunnel, like subsurface tunnel detection work, biogeochemistry work and geophysics work. Douglas says CRREL does most of their work related to climate impacts above the tunnel, where the vegetation and soil regime meet the permafrost. He says CRREL studies snow, hydrology, vegetation and ground temperatures above the tunnel as well.
Kevin Bjella, a CRREL research Arctic civil engineer, says the permafrost tunnel can be used to monitor climate change by measuring the amount of carbon from vegetation and organics in frozen soils to aid climate scientists with estimates of how much carbon will be released with thawing permafrost and the accelerated warming process.
“We also are using the tunnel as a test location for new methods to measure ice content from remote sensors such as on airplanes and satellites,” said Bjella. “Repeating these measurements will tell scientists how much permafrost is lost due to climate warming.”
Climate warming is causing more precipitation with more rain and snow, which causes more runoff and more erosion of the permafrost, and the erosion aspect is probably more impactful than the warming aspect.
Douglas said that early tunnel studies focused on permafrost engineering and geotechnical properties, because the Alaska Highway expanded roads and airfields across Alaska, and the Trans-Alaska Pipeline provided needs for unique engineering solutions.
There's a couple of ways to address building on permafrost. “Let's say climate change isn't a factor,” said Douglas. “Places that are quite cold and are going to remain cold, your goals are to either avoid permafrost build on material that's not frozen or build on what we call thaw-stable permafrost.”
Douglas says a key aspect of permafrost’s definition is that it's an earthen material that's below the freezing point for multiple years; this includes bedrock, gravel, sand, ice, and organic matter and silt.
“If you can build on what we call soft-table material, that's stuff like bedrock and sand and gravel that has very little ice content inside it, whether or not it's frozen or above freezing temperatures doesn't really matter,” said Douglas. “You can construct on it with minimal issues.”
In order for ERDC to continue its mission of providing engineering solutions in areas impacted by climate change, understanding the ice content in permafrost is key.
“If ground has no ice content, it simply is a cold soil or cold rock, which is not a problem when it warms above freezing,” said Bjella. “We are working to develop methods to detect ground ice from planes and from satellites.”
In order for the U.S. Army to be 100% functional when operating on frozen ground, the Army must fully understand the frozen terrestrial environment. This means knowing the ground ice content and soil type, and when this can be done remotely, as from airplanes or satellites, this allows decisions to be made without putting people on the ground in the Arctic.
Another way to address building on permafrost is to move material onto the ground surface. One method could be to excavate high ice content, high silt content or high risk material, and backfill with gravel or cement or material that's thaw stable, which will allow for the safe building of structures above the ground.
Another step that can be taken is to artificially keep the ground frozen with techniques like thermosyphons that allow cold air to get into the ground in the winter that keep it colder than it would naturally for that location and enable the ground to stay intact during summer months. There are approximately 80,000 thermosyphons along the Alaskan pipeline which keep the vertical support to the pipeline extra cold.
“The ideas are to build on good material, avoid bad material, bring in good material, build above the ground and keep everything frozen or artificially freeze it with basic refrigeration,” said Douglas. “Some of that has nothing to do with climate change, but in some ways, you can retrofit buildings by maybe artificially cooling the ground. And we're looking into some of that technology at the tunnel.”
The permafrost tunnel has captured past climate events that have been recorded in the sediments, ice and vegetation in the walls. Deciphering these details tells the story of past warming and cooling events and allows ERDC to understand what further climate warming may do to the frozen environment.
Douglas says over the last ten years, soil depths, soil temperatures, the creation of these thermal features and the thaw degradation has increases bit by bit, and in the future, warmer climate is projected to speed up even more.
“On the one hand, it's an exciting time to live in Alaska and work for CRREL and study these topics, but it's also a challenging time, because these issues are becoming more expensive, more uncertain and more difficult for the future,” said Douglas. “In some ways, it's kind of sad to watch this happening as fast as it is, but it's also invigorating to see some of the scientific and engineering ways we can address and minimize the impacts.”
| Date Taken: | 05.09.2022 |
| Date Posted: | 05.12.2022 18:16 |
| Story ID: | 420469 |
| Location: | FOX, ALASKA, US |
| Web Views: | 106 |
| Downloads: | 0 |
This work, ERDC researchers investigate how climate change impacts permafrost, by SGT David Marquis, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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