The Frozen Ground of the Far North is Thawing.

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Rising temperatures are thawing grounds that are historically frozen year-round, or permafrost.

Scientists at  Woodwell Climate Research Center  are studying what is causing this, how fast it is happening, and what implications this has for both the local environment and global climate change. To learn more about why the ground is thawing, we have to start at the beginning.

Permafrost is ground that has remained frozen for two or more years. It is found anywhere temperatures are low enough underground to stay below freezing. Permafrost can be found in high mountain ranges even in very warm latitudes, but it is most common in the Arctic and sub-Arctic.

Here, vast expanses of land are covered by a thin layer of soil that freezes and thaws based on the seasons, called the active layer, while permafrost extends underneath, sometimes hundreds of feet deep.

Indigenous peoples have rich and complex histories in these environments. They have developed lifestyles that enable them to live sustainably in permafrost lands. Later settlers have often struggled to adapt.

Structures built on permafrost can be ripped apart as the land freezes and thaws around them. Building foundations have to be placed below the active layer to be stable. Another complication is heat. The accumulated heat of a modern building can seep into the dirt underneath it and thaw the ground. Modern structures have to install systems to pull heat out and away from the building, while still keeping it warm inside.

When built properly, a building resting on permafrost can be as stable as anywhere else. It is, however, more expensive. Both due to the extra systems needed and the cost of shipping materials like concrete up north. All of this work can be undone in only a few years if the climate that created the permafrost begins to change.

When people living in the South think of Arctic climate change, they often think of a polar bear on a piece of sea-ice or a receding glacier. But beyond the ice, entire landscapes are changing.

A key consequence of the unusually high rate of heating in the Arctic, or Arctic Amplification, is that permafrost across the region is beginning to thaw. The ground-ice is melting, and the active layer is deepening. In many areas, like much of the Alaskan interior, permafrost is expected to disappear over the next century.

Similarly detailed data do not exist to project permafrost thawing across the entire Arctic, but what data do exist tells an ominous story. Many areas today are not totally covered in permafrost. Instead, patches exist between areas of unfrozen soil, forming a hodge-podge landscape called sporadic or discontinuous permafrost. Under one climate scenario these areas will become totally thawed, while areas of thaw will form inside what are currently continuous layers of permafrost.

Permafrost thaw affects the entire landscape, even in areas far from any visible human development. Slight increases in the ground temperature can spark a chain reaction of events that turn stable permafrost into a thermokarst landscape. Distinctive features form as ground-ice melts and the land surface collapses on itself.

Along hillslopes and valleys, thawing ground-ice can trigger landslide-like events called Retrogressive thaw slumps (RTS). These can be sudden, dramatic events, forming cliffs taller than a house seemingly overnight.

RTS events west of Fort McPherson (left) eroded the edges of a valley and caused a nearby lake to drain. Such events are expected to become more and more common as the Arctic continues to warm.

In flatter areas, ground-ice melts and pools on the surface as wetlands or lakes. Trees that relied on permafrost for stability collapse into these pools, and rings of tilted trees are called drunken forests.

Thaw can cause a building to fall as easily as it can bring down a tree. As the active layer deepens it can envelop building foundations. The thawing cycle can then break infrastructure that was once stable. Even outside of settlements, thaw changes the entire cycle of a landscape. As the very contours of the landscape change, plants and animals move with it. Old hunting grounds are not reliable, and plants do not grow in the same places as they used to for decades or centuries. Even though the land has been known intimately by Indigenous Peoples for millennia, it is changing in ways that they have never seen before, and can no longer predict.

People living in the Arctic used to expect minor changes in the land and permafrost thaw. Historically permafrost ebbed and swelled, and lifeways developed to exist alongside that change. Thermokarst pools made important watering grounds, and the ridges that form during RTS events can even be used to climb a previously inaccessible slope. Many of the words scientists use to describe thermokarst features come from Arctic Indigenous languages. But the difference today is speed and scale. The current pace of change is much faster than it has ever been, causing hardship for communities, as well as many plants and animals, to adapt.

Scientists are unsure how much carbon will be released as the permafrost continues to thaw. Estimates range from 30 to as high as 150 billion tonnes of carbon released into the atmosphere by 2100. This is the difference between permafrost emitting every year as much as Japan or the entire United States.

Arctic warming has created a feedback loop. When permafrost thaws it releases carbon which causes the atmosphere to warm more, further accelerating permafrost thaw, and the cycle continues on.

Climate change is happening now, and many times faster than it has happened in Earth's recorded history. Plants and animals struggle to adapt and migrate fast enough, and human communities who depend on these natural relationships are thrown into a crisis that they did not cause. Developing a better understanding of the mechanisms of permafrost thaw has never been more important.

Scientists often work close to the ground, taking soil samples and placing sensors to record moisture, temperature, and other measurements. They are interested not just in how permafrost thaws, but where it is thawing faster, and what is happening to the landscape as it changes.

Large augers are used to drill into the soil that can collect core samples over a meter long. Permafrost contains layers that tell the story of the landscape. Wildfires can burn off the top organic layers, leaving a visible line in the soil.

Permafrost cores provide a window into the past. Layers that are closer to the surface can be completely different from layers at greater depths. The different sections of the core provide information about what the climate was like, what plants and animals were present, and can even determine which bacteria were most active.

This is easier said than done. Arctic fieldwork brings its own challenges. Winters are long and unforgiving. Summer brings huge clouds of mosquitos or black flies that cling to every exposed surface. Researchers often wear bug jackets for protection from pesky biting insects.

Weather also plays an important role in researchers' ability to access areas and collect samples. While some locations are easy to get to by foot, others require using a helicopter. Long stretches of cloudy, rainy days can postpone sample collection for days, weeks, or even months. For scientists who study water, windy, stormy weather can prevent safe ferry-crossings, while long stretches of dry, hot weather can cause a shallow stream to completely dry up.

Permafrost is largely out of sight, out of mind to most people living in lower latitudes. But for plants, animals, and humans that live in permafrost environments, permafrost is a fundamental characteristic of the landscape. Rapid environmental change and permafrost thaw are creating daily challenges for thousands of Arctic residents and Indigenous communities, and for the hardest hit, represents a true humanitarian crisis.

Permafrost is also a sleeping giant for climate change. Greenhouse gas emissions from thawing permafrost have the potential to thwart society's ability to limit global warming to agreed-upon thresholds such as 1.5 or 2 degrees Celsius above preindustrial. And even though people living in Arctic communities contribute only a miniscule amount of greenhouse gas emissions, they have been most affected by climate change. The science and implications of permafrost have never been more important."

Learn more about how Woodwell Climate Research Center  here 

Photography | Chris Linder

Other images from Shutterstock, Flickr, and Wikimedia. All map data is open-source.

Maps and graphics made by Carl Churchill for Woodwell Climate Research Center.