Driven by climate change, thawing permafrost is radically altering the Arctic landscape
Across the Arctic, strange things are happening to the landscape.
Massive lakes, several square miles in size, disappeared within days. Subsidence of hillsides. The ice-rich ground is collapsing, leaving the landscape undulating where it was once flat and, in places, creating vast fields of large sunken polygons.
READ MORE: How permafrost thaw is changing the Arctic
This is proof that permafrost, the long-frozen ground beneath the surface, is melting. This is bad news for the communities built above – and for the global climate.
As an ecologist, I study these dynamic landscape interactions and have documented the various ways in which permafrost-induced landscape change has accelerated over time. The hidden changes going on there are a warning for the future.
What is permafrost?
Permafrost is permanently frozen ground that covers about a quarter of the land in the Northern Hemisphere, particularly in Canada, Russia and Alaska. Much of it is rich in organic matter from plants and animals long dead and frozen in time.
These frozen soils maintain the structural integrity of many northern landscapes, providing stability to vegetated and unvegetated surfaces, similar to load-bearing support beams in buildings.
As temperatures rise and precipitation patterns change, permafrost and other forms of ground ice become vulnerable to thawing and collapse. As these frozen grounds warm, the ground destabilizes, unraveling the intertwined fabric that has delicately shaped these dynamic ecosystems over millennia. Forest fires, which have increased in the Arctic, have increased the risk.
Below the surface, something else is active – and it’s amplifying global warming. When the ground thaws, microbes begin to feast on organic matter in ground that has been frozen for millennia.
These microbes release carbon dioxide and methane, powerful greenhouse gases. As these gases escape into the atmosphere, they warm the climate further, creating a feedback loop: warmer temperatures melt more soil, releasing more organic matter for microbes to feast on and produce more greenhouse gases.
The proof: endangered lakes
Evidence of human-caused climate change is accumulating throughout the permafrost.
The disappearance of large lakes, covering several square miles, is one of the most striking examples of recent patterns of northern landscape transitions.
The lakes drain laterally as wider and deeper drainage channels develop, or vertically through taliks, where the unfrozen ground beneath the lake gradually deepens until the permafrost is penetrated and the the water is flowing.
There is now overwhelming evidence that surface waters in permafrost regions are declining. Satellite observations and analyzes indicate that lake drainage could be linked to permafrost degradation. My colleagues and I have found that it increases with warmer and longer summer seasons.
This idea came after some of the highest rates of catastrophic lake drainage — drainage that occurs over a few days due to permafrost degradation — have been observed in the past five years in northwestern India. Alaska.
The disappearance of lakes in the permafrost expanse is likely to affect the livelihoods of indigenous communities, as water quality and water availability are important for waterfowl, fish and other wildlife. change.
Sunken hills and polygon fields
The thaw and collapse of buried glacial ice is also causing hillsides to sink at an increasing rate in the Russian and North American Arctic, sending soil, plants and debris sliding downwards.
A new study in northern Siberia has found that disturbed land areas have increased by more than 300% in the past two decades. Similar studies in northern and northwestern Canada found that subsidence there was also accelerating with hotter, wetter summers.
In flat terrain, wedges of ice can develop, creating unusual geometric patterns and shifts across the land.
Over decades, if not centuries, melting snow seeps into cracks in the ground, forming wedges of ice. These corners cause depressions in the ground above them, creating the edges of the polygons. Polygonal features form naturally as a result of the freezing and thawing process in a manner similar to that seen at the bottom of drying mudflats. When the ice wedges melt, the ground above collapses.
Even in the extremely cold environments of the High Arctic, the impacts of just a few exceptionally hot summers can dramatically alter the surface of the landscape, transforming previously flat terrain into rolling terrain as the surface begins to sink into depressions with melting ice in the ground below. Global rates of ice wedge melting have increased in response to global warming.