What is the active layer? The soil just beneath the ground surface thaws in the summer and refreezes in the winter. This is called the active layer Figure 3. The active layer in Canada is generally 0. The colder the climate, the thinner the active layer. Therefore, thin active layers can be found in the high arctic, whereas the thickest active layers occur near the southern limits of permafrost. What is a talik? This means that it is not permafrost but it is also not part of the active layer Figure 4.
The existence of a talik is often a sign that the permafrost is degrading. Taliks may also occur at depth, for example generated by constant flow of water.
Beneath large water bodies, a talik may form that connects all the way through the bottom of the permafrost. This is called a through talik. Why is permafrost changing? Permafrost is controlled by the energy balance at the ground surface. If that changes, so will ground temperatures and the characteristics of the permafrost. Extra heat can come from a warming climate, deeper snow cover, or surface disturbance.
All of these increase the thickness of the active layer, resulting in thaw of the top layers of the permafrost and if this continues for decades, potentially the loss of the entire permafrost body. Where permafrost contains a lot of ground ice, its thaw results in thermokarst processes, which include subsidence and landsliding. Changes in the permafrost and active layer may affect surface water drainage, which can then also affect the permafrost. Why is permafrost important?
Lakes and ponds have drained in some places and formed in others where once-solid land has collapsed. But with northern Canada warming about three times as fast as the rest of the world, climate change threatens the permanence of vast stretches of this frozen ground — and the ecosystems and communities it supports.
For the people living in the subarctic Dehcho region of the Northwest Territories, the changes have been stark. While the impacts are felt most acutely in the North, permafrost thaw has implications for the global climate as well. Scientists are now investigating how increased warming of the North could be part of a vicious cycle known as the permafrost carbon feedback loop — the more the climate warms, the more permafrost thaws and potentially emits more greenhouse gasses, which further warms the climate and thaws more permafrost.
Permafrost holds twice as much carbon as the atmosphere, and roughly 15 per cent of that stored carbon is vulnerable to being released, Merritt Turetsky, director of the Institute of Arctic and Alpine Research at the University of Colorado Boulder, told The Narwhal in an interview. While Turetsky said emissions from permafrost are small relative to human-caused carbon pollution, they are an added burden on a climate already in crisis. People always tell us they love our newsletter. The risks to infrastructure in Dehcho communities loom in the future — potentially amplified by the permafrost carbon feedback loop — but permafrost thaw has already taken a toll in the region, Norwegian said.
For traditional land users, who harvest food by hunting and fishing, these are worrying shifts that have made travel more dangerous, Norwegian added. And now, with even more emissions potentially being released as part of the permafrost carbon feedback loop, permafrost melt threatens to accelerate further.
And with it, the effects on the already altered region could accelerate as well. Dehcho elders say they have already observed dramatic changes to the landscape in the region, including forests dying off and being replaced by wetlands. Photo: Environment and Climate Change Canada. A map created by WWF-Canada for its wildlife protection assessment indicates the levels of soil carbon across Canada.
Map: WWF-Canada. A diverse array of microbes breathe in oxygen and breathe out carbon dioxide, as humans do, Stein said. Specialized microorganisms called methanogens, meanwhile, generate methane, a greenhouse gas more powerful than carbon dioxide, as a by-product of metabolism. In response, some scientists are now investigating the potential to use another set of specialized microbes that consume methane, called methanotrophs, to help counteract the methane-generating methanogens awoken by permafrost thaw.
Growing more peat moss was just one of the potential responses to the permafrost carbon feedback loop discussed during a March dialogue series hosted by the Permafrost Carbon Feedback Action Group.
Mike Brown, a Vancouver venture capitalist focused on climate change, established the group in partnership with the Permafrost Association of Canada to help address the challenge of greenhouse gas emissions from thawing permafrost. Over the course of the next century, permafrost thaw could emit as many greenhouse gases as deforestation and other land use change, Ted Schuur, a professor of ecosystem ecology at Northern Arizona University, said during the first webinar. A researcher measures thawing permafrost on Herschel Island, a few kilometres off the Yukon coast.
Dramatic changes to landscapes in the North could be accelerated by the permafrost carbon feedback loop. The basic premise of solutions to the permafrost carbon feedback loop is simple: reduce permafrost thaw to reduce the emissions it releases. How to prevent permafrost thaw is where things get complicated.
The greatest thicknesses in Canada are over 1, m at high elevations in parts of Baffin and Ellesmere islands, ranging down to 60—90 m at the southern limit of the continuous permafrost zone. The thickness of active layer permafrost ranges from under 10 cm on Ellesmere in porous sediments to 15 m at high altitudes in the fissured, impermeable rocks in the mountains of southwestern Alberta on the outer margin of continuous permafrost.
Distinctive landforms are associated with permafrost see Periglacial Landform. These landforms include ice wedges, polygonal ground and pingos. Ice wedges result from the ground cracking in winter, followed by the cracks being filled with snow and meltwater during spring and summer. Pingos are ice-cored mounds up to m high. They are formed when water in the ground changes to ice and expands so that the resulting ice masses force the overlying ground upwards.
Thawing of permafrost often results in the ground sinking where ice was present, and in the formation of thaw lakes or mounds hummocks. This terrain, called thermokarst, can be induced by human activities or by climate change. Permafrost poses significant challenges to modern human settlement and industrial activity. For example, permafrost makes agriculture difficult, contributing to the higher cost of food in northern Canada. Heated homes and buildings are generally built on top of piles with enough air space underneath to avoid thawing the permafrost.
Similarly, paved roads or runways require an insulating layer so as not to warm the ground and subsequently melt the permafrost. Because the ground is frozen, garbage and sewage disposal is also difficult in areas with permafrost, as is the grounding of electrical devices. As much garbage is incinerated as possible, while electrical cables are usually placed above ground to avoid being severed by the earth cracking in winter.
Water and sewage pipes must be insulated or placed in insulated boxes on piles called utilidors. The permafrost areas of the northern hemisphere are underlain by significant reserves of oil, gas, diamonds and metal ores. However, permafrost poses a challenge to extracting these resources. Once extracted, there are also challenges in getting these commodities to market.
Soil temperatures in many areas are rising as a result of climate change.
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