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In flat terrain, ice wedges are able to develop, creating unusual geometric patterns and changes across the land.
Over decades to centuries, melting snow seeps into cracks in the soil, building up wedges of ice. These wedges cause troughs in the ground above them, creating the edges of polygons. Polygonal features naturally form as a result of the freezing and thawing process in a way similar to that seen at the bottom of drying mud flats. As ice wedges melt, the ground above collapses.
  An ice wedge dated to the late Pleistocene era in Noatak National Preserve in Alaska. (David Swanson / National Park Service)
Even in extremely cold high Arctic environments, the impacts of only a few uncommonly warm summers can dramatically change the surface of the landscape, transitioning previously flat terrain into undulating as the surface begins to sink into depressions with the melting of ice in the soil below. Overall rates of ice wedge thawing have increased in response to climate warming.
Across many Arctic regions, this thawing has also been hastened by wildfire. In a recent study, colleagues and I found that wildfires in Arctic permafrost regions increased the rate of thaw and vertical collapse of the frozen terrain for up to eight decades after fire. Because both climate warming and wildfire disturbance are projected to increase in the future, they may increase the rate of change in northern landscapes.
The impact of recent climate and environmental change have also been felt at lower latitudes in the lowland boreal forest. There, ice-rich permafrost plateaus — elevated permafrost islands heaved above adjacent wetlands — have rapidly degraded across Alaska, Canada and Scandinavia. They can look like cargo ships filled with sedges, shrubs, and trees sinking into wetlands.
Why does it matter?
Frigid temperatures and short growing seasons have long limited the decomposition of dead plants and organic matter in northern ecosystems. Because of this, nearly 50 percent of global soil organic carbon is stored in these frozen soils.
The abrupt transitions we’re seeing today — lakes becoming drained basins, shrub tundra turning into ponds, lowland boreal forests becoming wetlands — will not only hasten the decomposition of buried permafrost carbon, but also the decomposition of above-ground vegetation as it collapses into water-saturated environments.
  Russia has a large part of the world’s permafrost. When Russia invaded Ukraine in early 2022, some Western institutions paused funding for scientific studies there after years of international cooperation. (Joshua Stevens / NASA)
  Red areas are talik, or unfrozen ground above permafrost, expected in the 2050s in five northern Alaska parks. Permafrost thickness varies with climatic conditions and landscape history. For example, the active layer that thaws in summer may be less than a foot thick near Prudhoe Bay, Alaska, or a few feet thick near Fairbanks, while the average permafrost thickness below these sites has been estimated to be around 2,100 to 300 feet, respectively (about 660 to 90 meters), but varies greatly. (National Park Service)
Climate models suggest the impacts of such transitions could be dire. For example, a recent modeling study published in Nature Communications suggested permafrost degradation and associated landscape collapse could result in a 12-fold increase in carbon losses in a scenario of strong warming by the end of the century.
This is particularly important because permafrost is estimated to hold twice as much carbon as the atmosphere today. Permafrost depths vary widely, exceeding 3,000 feet in parts of Siberia and 2,000 feet in northern Alaska, and rapidly decrease moving south. Fairbanks, Alaska, averages around 300 feet (90 meters). Studies have suggested that much of the shallow permafrost, 10 feet (3 meters) deep or less, would likely thaw if the world remains on its current warming trajectory.
To add insult to injury, in water-logged environments lacking oxygen, microbes produce methane, a potent greenhouse gas 30 times more effective at warming the planet than carbon dioxide, though it doesn’t stay in the atmosphere as long.
  Funnels used to collect methane are seen in an area of marshland at a research post at Stordalen Mire near Abisko, Sweden, July 29, 2019. Picture taken July 29, 2019. (Hannah McKay / Reuters File Photo)
How big of a problem thawing permafrost is likely to become for the climate is an open question. We know it is releasing greenhouse gases now. But the causes and consequences of permafrost thaw and associated landscape transitions are active research frontiers.
One thing is certain: The thawing of previously frozen landscapes will continue to change the face of high-latitude ecosystems for years to come. For people living in these areas, slumping land and destabilizing soil will mean living with the risks and costs, including buckling roads and sinking buildings. 
Mark J. Lara is assistant professor in plant biology and geography at University of Illinois at Urbana-Champaign.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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