Thawing permafrost is roiling the Arctic landscape, driven by a hidden world of changes beneath the surface as the climate warms

The Conversation

<span class="caption">Permafrost and ice wedges have built up over millennia in the Arctic. When they thaw, they destabilize the surrounding landscape.</span> <span class="attribution">Michael Robinson Chavez/The Washington Post via Getty Images</span>

There are strange things happening in the landscape.

Massive lakes, several square miles in size, have disappeared in a few days. The hills are slumping. Ice-rich ground collapses, leaving the landscape wavy, and in some locations creating vast fields of large, sunken polygons.

There is evidence that the long-frozen soil below the surface is thawing. It is bad news for the communities built above it.

I study these dynamic landscape interactions and have been documenting the various ways landscape change has accelerated over time. There are hidden changes that hold a warning for the future.

What is permafrost?

In Canada, Russia and Alaska, perennially frozen soil covers 25% of the land. The organic matter of dead plants and animals is rich.

The structural integrity of many northern landscapes is maintained by the frozen soils.

As temperatures rise and precipitation changes, ground ice becomes vulnerable to thaw and collapse. The interwoven fabric that has delicately shaped these dynamic ecosystems has been unraveling as the ground warms. The risk of wildfires has been increasing across the northern part of the world.

<span class="caption">Thawing permafrost can cause the ground to sink and crack in places, destabilizing roads and buildings.</span> <span class="attribution">Orjan F. Ellingvag/Corbis via Getty Images</span>

Global warming is being amplified by something else under the surface. The soils that have been frozen for thousands of years begin to thaw when the ground thaws.

Carbon dioxide and methane are potent greenhouse gases. Warmer temperatures thaw more soil, releasing more organic material for microbes to feast on and produce more greenhouse gases.

The evidence: disappearing lakes

There is mounting evidence of climate change.

One of the most striking examples of recent patterns of northern landscape transitions is the disappearance of large lakes.

The lakes are draining as the drainage channels develop, or vertically through taliks, where the unfrozen soil under the lake gradually deepens until the permafrost is penetrated and the water draining away.

There is overwhelming evidence that the surface water is declining. Satellite observations show lake drainage may be linked to degradation of the permafrost. It increases with warmer and longer summer seasons.

Over the past five years, there have been some of the highest rates of catastrophic lake drainage in northwestern Alaska.

The disappearance of lakes across the permafrost extent is likely to affect the livelihoods of Indigenous communities as water quality and water availability important for waterfowl, fish and other wildlife shift.

Slumping hills and polygon fields

The thaw and collapse of buried ice is causing hillsides to slump at increasing rates across the Russian and North American Arctic, sending soil, plants and debris sliding downslope.

Over the past two decades, the disturbed land surfaces in northern Siberia have increased over 300%. In northern and northwestern Canada, slumping accelerated with warmer and wetter summers.

<span class="caption">An ice wedge dated to the late Pleistocene era in Noatak National Preserve in Alaska.</span> <span class="attribution">David Swanson/National Park Service</span>

In flat terrain, ice wedges can create unusual geometric patterns and changes across the land.

Over the course of hundreds of years, melting snow causes cracks in the soil to form wedges of ice. The edges of polygons are created by troughs in the ground above them. The freezing and thawing process results in the formation of plican features similar to those seen at the bottom of drying mud flats. The ground collapses as ice wedges melt.

The impact of only a few warm summers can change the landscape dramatically, as the surface begins to sink into depressions with the melting of ice in the soil below. Climate warming has increased the rates of ice wedge thawing.

The thaw has been accelerated by wildfire. The rate of thaw and vertical collapse of the frozen terrain increased after fires in the permafrost regions. The rate of change in northern landscapes may increase because of climate warming and wildfire disturbance.

The impact of recent climate and environmental change has been felt at lower latitudes. The elevated permafrost islands heaved above the wetlands have rapidly degraded across Alaska, Canada and Scandinavia. They look like cargo ships filled with shrubs and trees.

Why does it matter?

Cold temperatures and short growing seasons have limited the decomposition of dead plants and organic matter in the north. 50% of global soil organic carbon is stored in frozen soils.

The rapid transitions we are seeing today will speed up the decomposition of buried permafrost carbon and above-ground vegetation.

<span class="caption">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.</span> <span class="attribution">Joshua Stevens/NASA</span> — 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

Climate models suggest the impacts of such transitions could be dire. A recent study published in Nature Communications suggested that a scenario of strong warming by the end of the century could result in a 12-fold increase in carbon losses.

The atmosphere is estimated to hold less carbon than the permafrost. In parts of Siberia and northern Alaska the frost depths are over 3000 feet. The average is around 300 feet. If the world remains on its current warming trajectory, some of the shallow permafrost, 10 feet deep or 888-282-0465 888-282-0465 888-282-0465 888-282-0465, would likely thaw.

Methane, a potent greenhouse gas 30 times more effective at warming the planet than carbon dioxide, is produced by microbes in water-logged environments that lack oxygen.

It's not clear how big of a problem thaw permafrost will become for the climate. We know that it is releasing greenhouse gases. The causes and consequences of permafrost thaw are active research frontiers.

The face of high-latitude ecosystems will continue to change for years to come because of the thaw of previously frozen landscapes. Living with the risks and costs of slumping land and destabilizing soil will be a challenge for people living in these areas.

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The Conversation is a news site dedicated to sharing ideas from academic experts. It was written by a University of Illinois student.