There’s a reason scientists and climate change activists have been raising the alarm about the melting of the planet’s permafrost for most of the last decade.

This is because, as climate change causes a general increase in global average temperatures, the consequent melting of that perpetually frozen layer of land in the Arctic has the potential to drastically change people’s way of life, not just in the north, but all over the world.

At the local level, thawing of permafrost has impacts on the way people – and animals – hunt, fish, and gather food. It has far-reaching impacts on any man-made infrastructure, which has consequential effects on inter-community access in a region where those communities tend to be widely dispersed.

And the thawing of permafrost has impacts on a global level, where the process can contribute to the release of greenhouse gases into the atmosphere, which, in a feedback loop, will further accelerate the increase in the global average temperature, which it will cause more thawing of the permafrost.

Permafrost, by definition, is any type of soil that remains at 0 C or lower for two or more consecutive years. In Canada, most of that permafrost contains water in the form of ice.

In practice, much of the world’s permafrost, predominantly north of 60 degrees latitude, has been frozen for thousands of years. That includes large swaths of Canada, Greenland, Siberia, and Alaska.

In those regions, there is a layer of soil on the surface that repeatedly thaws and refreezes as the seasons change. Scientists call this the active layer. It is typically 0.5 to 2 meters thick, with the thinnest active layers found in the northernmost regions, while the thickest layers are near the southern limits of the permafrost.

Beneath that active layer is the permanently frozen layer of permafrost. In regions where temperatures are consistently cold, such as Ellesmere Island in the High Arctic, that layer can be 700 meters thick. Further south, as in Yellowknife, it is only a few meters thick.

At the interface of the two layers, permafrost tends to contain a lot of water in the form of ice. This is significant because when ice-rich permafrost begins to melt, it undermines the stability of the soil above it.

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When that happens, sinkholes, sinkholes in the land may occur, and in cases where the ground is sloped, landslides may occur. Or, as scientists call it, an “active layer shedding fault.”

To a large extent, the thawing of a permafrost layer depends on two things: temperature and precipitation.

“If you have a warm winter where the winter is not cold enough to cool the permafrost, it is relatively bad. If you have a hot summer, that’s not good news either, ”says Fabrice Calmels, president of Permafrost Research and Geoscience at Yukon University.

“If you have a lot of snow in winter, it means that you will have a layer that isolates the cold air from the permafrost. So you keep the permafrost warmer because you put a blanket on it. So a lot of snow is not good. “

If it rains, Calmels says, that’s not good for the permafrost either, because warmer water will seep into the ground, move through its active layer, and heat the permafrost below.

When that happens, things on the surface get upset.

The topology change can be quite dramatic.

Old Crow in the Yukon is located 800 km north of Whitehorse, a three hour flight by plane, the only way to get there.

For generations, Lake Zelma, near Old Crow, has been a hunting and fishing focal point for the Vuntut Gwitchin First Nation.

But in 2007, that lake suddenly, catastrophically, drained, as a result, in part, scientists say, of melting permafrost that carved cavities beneath the lake.

That is an extreme example. There are other less sensational ones that can have far-reaching long-term consequences.

Lakes become grasslands or ponds. Traditional capture trails become inaccessible. Berries and medicinal plants cannot grow where they used to.

In the same area around Old Crow, Calmels says, the thawing of the permafrost has caused changes in the forest above. And as the forest degrades, a species of lichen attached to that forest becomes rarer. And that particular lichen is the caribou’s favorite food. If lichen rarity becomes widespread, it potentially means that caribou change their migration routes, meaning those who hunt caribou will have to change along with them.

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In areas where humans have built infrastructure on top of the permafrost, thawing of that layer often spells soil disturbance. And that means that roads can become impassable, even develop sinkholes, and airport runways can become unusable.

And that’s especially problematic in the northern 1960s, where remote communities depend on those roads and airports for all their supplies.

Just outside of Whitehorse, Calmels is tracking a permafrost fall making its way onto the Alaska Highway. If that depression suddenly split the highway in two, all highway contact between Whitehorse and some of the northern Yukon communities would be lost, as well as all access to Alaska.

In northern Quebec, scientists have placed sensors at airports in three northern communities, hoping to predict any permafrost drop before it happens.

But the cost of melting permafrost can be higher and much more global.

Buried within that frozen layer is a large amount of organic matter. In the last ice ages, in Siberia and parts of the Yukon and Alaska, large portions of the Arctic were not covered by glaciers that were constantly moving south. In these organically rich regions lived some of the planet’s legendary – now extinct – megafauna, the woolly mammoth and the great auk, as examples.

When the ice age regressed, all that organic matter, along with huge amounts of plant biomass, was buried and remains frozen in permafrost.

But when that organic matter is thawed again and exposed to the air, when the surrounding permafrost melts, nature’s organic chemical processes resume. Bacteria break down organic carbon into carbon dioxide and methane.

Once a carbon sink, permafrost now becomes a source of greenhouse gases.

And those greenhouse gases contribute to warming atmospheric temperatures, which means that, among other things, they will accelerate the permafrost thawing process.

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