More and more areas of year-round unfrozen ground are found in interior and northwest Alaska and will continue to increase due to climate change, according to a new study by scientists at the University of Alaska’s Fairbanks Geophysical Institute.
The scientists said the spread of taliks – volumes of unfrozen soil within permafrost areas – has major implications for the movement of carbon between organisms, minerals and the atmosphere. Taliks will also affect the transfer of material such as nutrients into the water and encourage the development of thermokarsts, areas of submerged land formed by the thawing of permafrost.
Their findings were published in the journal today nature geosciences.
Louise Farquharson, a research assistant professor, wrote the paper. Geophysics Professor Emeritus Vladimir Romanovsky, Research Assistant Professor Alexander Kholodov, and Research Associate Professor Dmitry Nicolsky are co-authors. All four are in the Permafrost Laboratory at the Geophysical Institute. Romanovsky, Kholodov and Nicolsky are also associated with institutions in Russia.
“We are in a transition phase where we often see talic formation but can also freeze again if we have a year with little snow and very cold winter temperatures or a cool summer,” Farquharson said. “After about 2030, however, our summer and winter air temperatures will warm enough that we will have talic formation regardless of snow.”
“I think it’s important that people know that what we’ve seen so far, for example, with the permafrost degradation in Fairbanks, is not a steady state,” she said. “The rate and magnitude of permafrost degradation will likely accelerate if Talik development really takes off.”
Taliks can occur in a variety of locations: between the top of the permafrost and the bottom of the seasonally frozen layer, within the permafrost due to water currents, and within the permafrost due to previous thaw events, e.g. B. after a lake has been drained. They can also cut through the entire permafrost column where the permafrost is thin, often due to the presence of rivers or lakes.
More talcs will form across a larger area of Alaska as summer and winter temperatures rise and the depth of summer soil thaws begins to exceed the depth of winter frosts.
Consequences may include the movement of material previously trapped in frozen ground through the new water. Dissolved organic carbon, dissolved nitrogen, and pollutants like mercury could eventually find their way into streams and rivers.
Widespread degradation of permafrost will also create challenges for new construction and maintenance of existing buildings and other infrastructure.
Scientists analyzed ground temperature data from 1999 to 2020 collected at dozens of Alaskan locations in the Permafrost Laboratory’s monitoring network. They then selected 54 of these sites for the study, covering an area of approximately 186,000 square miles.
Of the 54, scientists observed incomplete freezing and the early stages of talik formation at 24 sites in the winter of 2017-2018, up from three in the previous year.
Historically, taliks have been primarily associated with rivers and deluge lakes, as well as in wildfire-affected areas, removing the thermally protective vegetation and therefore allowing deeper summer thaws. None of the sites surveyed by the UAF team were affected by disturbances such as surface water or wildfires.
Talik formation in the study area accelerated significantly in 2017-2018 due to higher air temperature and above-average snowfall, the scientists found. Due to its insulating properties, heavy snow slows the transfer of heat from the ground to the atmosphere, increasing the time it takes for the ground to refreeze and, in some cases, preventing complete refreezing.
The research team’s modeling and observations show that talc formation at the study sites occurred only briefly in the 50 to 60 years prior to 2017-2018.
The team also writes that current permafrost thawing estimates and forecasts underestimate the magnitude of the thaw because they fail to account for the impact of widespread talic formation.
Researchers predicted that by 2030, under the International Panel on Climate Change’s high-emission scenario, talic formation will have started in up to 70% of the discontinuous permafrost zone, regardless of snow conditions. By 2090, talik thickness may reach 40 feet in areas with black spruce forests and warmer ecosystems.
“Our climate trajectory will likely make talic formation a major driver of permafrost degradation in the discontinuous permafrost zone and eventually, as temperatures continue to warm, in the continuous permafrost zone farther north,” Farquharson said. “And not only in Alaska, but also in other arctic regions.”
“Talik formation is becoming a really important mechanism of permafrost degradation,” she said.
Arctic greening thaws permafrost, promotes runoff
Louise M. Farquharson et al., Subaerial Talik Formation Observed Across the Discontinuous Alaskan Permafrost Zone, nature geosciences (2022). DOI: 10.1038/s41561-022-00952-z
Scientists Find New Indicators of Alaskan Permafrost Thawing (2022, June 7)
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