Is Permafrost Truly, Well, Everlasting?

In 2010, a woolly mammoth carcass was found in Siberia near the Laptev Sea's coast. Named "Yuka," this long-extinct creature died approximately 28,000 years ago. Remarkably, her remains were so well-preserved, even showing patches of red fur, a mostly intact brain, and cell structures resembling nuclei.

How did her body remain so well-preserved instead of decaying? The simple answer is, Yuka was frozen — not within a glacier or iceberg, though. After her death, Yuka was trapped in a layer of permafrost.

What Exactly Is Permafrost, and Where Can It Be Found?

As we know, water freezes at 32 degrees Fahrenheit (0 degrees Celsius). Permafrost refers to any ground material — such as soil, sediment, and rock — that stays at or below freezing temperatures for a minimum of two consecutive years. Roughly 25 percent of the land in the Northern Hemisphere is known to harbor permafrost.

The term "permafrost" was originally introduced by American paleontologist Siemon W. Muller, a blend of the words "permanent" and "frost." Even though it has that name, permafrost doesn’t remain indefinitely. Due to climate change, it has been melting at an alarming rate, with significant consequences for the environment and economy.

Generally, permafrost is found in regions where the annual average air temperature is 0° Celsius (32° Fahrenheit) or lower. The National Snow and Ice Data Center states that most of the Northern Hemisphere’s permafrost is located between the high latitudes of 60 and 68 degrees north. Areas such as Siberia, Canada, Alaska, and parts of Scandinavia are rich with this frozen earth.

Farther south, permafrost can be discovered in high-altitude areas — like the Tibetan Plateau, the Hindu-Kush mountain range, and the Swiss Alps. While permafrost is less common below the equator, it can still be found beneath parts of New Zealand, the Andes, and Antarctica.

Just like its locations, the composition of permafrost is diverse; it’s not consistent. Some areas are ice-free, while others contain over 30 percent ice. Similarly, the depth, age, and coverage of permafrost can vary greatly.

Permafrost is often found beneath an "active layer" of soil, which experiences seasonal thawing and freezing. The thickness of permafrost itself can range from less than 3.2 feet (1 meter) to over 4,921 feet (1,500 meters).

It can also be patchy. Northern Alaska is in a "continuous permafrost zone," where more than 90 percent of the land is underlaid by permafrost. But as you move south of the Brooks Mountain Range, the situation changes. Here, in a "discontinuous permafrost zone," permafrost only covers a smaller percentage of the surface.

Snow, Trees, and Water

Although it might seem counterintuitive, snow is an excellent insulator. When thick layers of snow remain throughout the year, they can keep the ground too warm for permafrost. In areas where permafrost already exists, these insulating snow layers may even raise its temperature.

However, while snow presents a challenge, peat is quite the opposite. Common in and around the southern Arctic, peat is a type of substrate composed of partially decomposed organic matter (such as mosses and swamp plants). Generally, the ground beneath peat stays cool and shielded from solar warmth, helping to preserve permafrost.

Evergreen forests also provide valuable support. With their dense needle-covered branches, pine trees limit how much sunlight and snow reach the ground. In turn, the evergreens play a role in preventing permafrost from thawing. This explains why permafrost is often found beneath clusters of pines in high-elevation and high-altitude regions.

The relationship is mutually advantageous. Since liquid water can't pass through solid permafrost, it functions as a drainage barrier. Any unfrozen water that infiltrates the active layer gets trapped there. Unable to move deeper into the earth, this water sustains surface plants.

The Ancient Past and Unpredictable Future

Sometimes, permafrost forms in direct relation to the ground beneath it. When this happens, newly deposited soils, sediments, and rocks rapidly reach 32 degrees Fahrenheit (0 degrees Celsius). Conversely, permafrost can also develop when pre-existing unfrozen ground is cooled from the surface down.

At the very least, permafrost in Prudhoe Bay, Alaska is estimated to be around 500,000 years old. In comparison, some of the permafrost beneath Canada's Yukon Territory may be over 700,000 years old.

In the Yukon, researchers uncovered an ancient horse leg — with preserved DNA samples. Permafrost has an incredible ability to preserve organic matter for extended periods. In 2012, Russian scientists even revived live tundra plants from ice age fruits that had been frozen in permafrost for roughly 30,000 years.

Unfortunately, as permafrost melts, the organic materials trapped inside start to decompose, releasing carbon and methane into the atmosphere. These gases contribute to the acceleration of climate change. The troubling news is that, according to a 2019 study published in Nature Communications, various global permafrost deposits have warmed by around 39.7 to 32.8 degrees Fahrenheit (0.39 to 0.1 degrees Celsius) from 2007 to 2016.

Currently, about 1.7 billion tons (1.6 billion metric tons) of carbon are trapped in permafrost. Scientists are uncertain how much of this carbon will be released into the atmosphere if the thawing trends continue — or how fast this will occur. Some forecasts are quite troubling.

To add to the problem, thawing permafrost can destabilize the landscape. In Norilsk, Russia, for example, over 100 residential buildings have been damaged due to the softening of the permafrost beneath them. The warming of permafrost has also caused landslides, drained lakes, and destroyed roads.