The term solid ground takes on a new meaning in the context of permafrost. This ice-hardened earth and soil mixture is rock solid until temperatures rise above freezing. Then it turns into a festering, organic goo of water-logged mud containing the rotting remains of plants and animals that lived tens of thousands of years ago. Permafrost underlies much of the land within the Arctic circle and 24 percent of the land in the northern hemisphere. But over the years, it has morphed from an engineering problem into a climate change problem.
Permafrost formed over centuries. During that time, plants and animals lived and died with their remains frozen into the structure of the soil before complete decomposition set in. The normal carbon cycle was interrupted by this process. Plants and animals require carbon to live, and they sequester that carbon in their bodies. Under most circumstances, their death starts a process where bacteria break down the organic material and release carbon back into the atmosphere in the form of carbon dioxide and methane. Permafrost creates a time capsule where decomposition is interrupted, and the carbon remains sequestered in the icy soil.
An estimated 1,400 gigatons of carbon lies frozen in the Arctic permafrost. By comparison, the earth’s atmosphere contains only 850 gigatons of carbon.
Prior to the prominence of climate change as a global concern, permafrost was primarily considered an engineering problem. This hardened layer of frozen soil stood between Alaskan gold prospectors and their treasure during the gold rush. Brute force via blasting and thawing was the solution. So first, the permafrost was blown into chunks, then “steam points” were used to thaw out the soil chunks and retrieve the gold.
Later, during the construction of the Alaskan Highway to connect Alaska with Canada, engineers again fought with the permafrost. They found that building directly on top of the frozen earth caused it to thaw out. Then trucks and equipment sank helplessly into the resulting muck.
During the cold war, the military experimented with building bunkers into the frozen ground for the storage of military equipment. Permafrost is naturally shock-absorbing and able to withstand shock from bomb attacks. Again, the objective was elusive, and the project never took off on a large scale.
Today engineering problems still plague some areas. As global warming proceeds, the once-solid land disintegrates into unstable ground, causing infrastructure and building foundations to collapse.
The climate change era
The modern recognition of climate change as a destabilizing environmental threat prompted a new look at permafrost. As the permafrost thaws, it develops a landscape referred to as thermokarst topography. When warmed, the high ice content in the soil turns to water and promotes rapid erosion and collapse of the land surface. This land collapse results in shallow lakes, mud bogs, and mud mounds. Once unfrozen, the organic matter in the soil becomes food for bacteria. Then the bacteria rapidly consume the centuries-old organic materials and return the carbon to the atmosphere as carbon dioxide and methane.
Since the Arctic holds twice as much carbon as the atmosphere, the potential exists for massive releases of greenhouse gases from thawing permafrost. The added boost of these gases then accelerates the thawing process, so even more carbon enters the atmosphere. At some temperature tipping point, the process becomes self-sustaining and irreversible.
Research is unraveling the mysteries of permafrost, but there is still much to learn.
Arctic Warming (Source: ArcheanWeb) – https://archeanweb.com/2019/12/05/arctic-warming-climate-change/ Also:
Much ado about tipping points (Source: ArcheanWeb) – https://archeanweb.com/2020/01/10/much-ado-about-tipping-points/ Also:
Want to Study Permafrost? Get It Before It’s Gone (Source: Wired) – https://www.wired.com/story/want-to-study-permafrost-get-it-before-its-gone/ Also:
Methane and Frozen Ground (Source: National Snow and Ice Data Center) – https://nsidc.org/cryosphere/frozenground/methane.html Also:
Feature Image: Thermokarst Lakes (Modified) – By Jesse Allen and Robert Simmon – NASA Earth Observatory,- Natural-colour image of the Omulyakhskaya and Khromskaya Bays, Russia. The land around the bays is dotted with thermokarst lakes, which result from water released by thawing permafrost. The water in a thermokarst lake doesn’t always stay put; these lakes can melt through the surrounding permafrost and drain into a nearby water body, especially if it sits at a slightly lower elevation. This appears to have occurred in multiple lakes between the bays shown above – Public Domain, https://commons.wikimedia.org/w/index.php?