Permafrost

A Yedoma, an underground ice feature, exposed by melting permafrost and erosion.

NPS / Tahzay Jones

Many parts of Alaska have a hidden underground world of frozen ground. The depth and extent of this “permafrost” varies by location, depending on average air temperatures, soil types, topography, and surface vegetation. Frozen ground is stable, providing a solid foundation for roads and buildings. Permafrost is also impermeable, so water pools on the surface instead of seeping through the soil, and creates a landscape dotted with many small lakes.

The shorter and warmer winters are affecting permafrost. – Dave Swanson, Fairbanks

Rising temperatures are melting this frozen ground and forever altering the landscape. Without this solid foundation, roads and buildings sink into the softer, non-frozen ground. Sinkholes and slumpages form when their frozen supportive underground layers thaw. And lakes previously formed by permafrost have begun to drain.

Melting Permafrost

Shifting sands of coastal barrier islands.

NPS

Because it’s so far south, Skagway doesn’t have much permafrost, so its residents weren’t too concerned about environmental change related to permafrost. In contrast, people in Nome were very concerned about the ground thawing around them.

Things have reached a tipping point, with the average temperature being above freezing, so the ground is thawing. Houses are suffering. They are shifting, which leads to sheetrock cracking, breaks in sewer lines and water pipes, and a big mess. – Charlie Lean, Nome

Our ice cellars built into the permafrost are melting. We can’t keep our traditional foods preserved in them anymore. We have to use freezers. – Roy Ashenfelter, Nome

Because of thawing permafrost, there is more slumping along the riverbanks, the rivers have larger sandbars, and there is more sediment in the river. All of this makes river travel more difficult and dangerous. – Roy Ashenfelter

A pingo formation on the otherwise flat tundra.

NPS

Loss of permafrost and thawing and slumping of ground changes the topography and landscape. Conical ice-filled hills, known as pingos, seen in regions of continuous permafrost, collapse as their internal frozen support structure melts.

Things are liquifying. Pingos are disappearing. In the 1980s, there were lots of pingos. Around 20. Today there is only one. The others have collapsed. – Charlie Lean

You can see areas where you get collapses of the permafrost, and then the liquid from that is just sort of running off, and so you get thermal erosion in addition to normal erosion that you would see with the wind and wave action. You can also see, in general, what looks to be decreases in the elevation of some areas where you’re getting drowning of the tundra. That’s really changing the near-shore habitat in some of these areas. I think that there’s a lot more happening in terms of ramifications of these changes than we fully understand. – Tahzay Jones, Anchorage

Draining Lakes

A drained lake that is now colonized by the mastodon flower, a small flowering plant.

NPS

When permafrost thaws, surface water seeps deeper, draining lakes and wetlands. Many lakes in northwest Alaska have drained in this way. Without these lakes and water, the surrounding tundra becomes drier. This changes the appearance of the landscape, what plants and animals can survive, and in some places increases the risk of wildfires.

Lakes are suddenly draining due to thawing permafrost. The water is held in because the ground around it is frozen and creates a barrier. But as permafrost thaws, it creates a passage through which the water can escape, and so the lakes drain. Flowing water then enhances thaw of permafrost. It’s a perfect storm for lake drainages. This happens naturally but is now occurring at an unprecedented rate. – Dave Swanson

More water flowing out from lakes and the tundra leaves more sediment in the waterways from bank erosion. Dropping water levels in lakes and drying wetlands also affect the fish and birds who depend on this habitat.

What’s happening in a lot of places is that lakes suddenly just drain and create no-water habitat. It now becomes filled with vegetation. That’s certainly is a change in habitat. Fish might be losers, but maybe some birds are winners? You kind of have to look at it as just a change in habitat type. – Tahzay Jones

Usually there aren’t a lot of fish in these lakes because they are shallow, but, the loss of lakes causes problems for waterfowl because they use them for nesting sites and food sources. – Dave Swanson

For more information about warming soils, changing landscapes, and lake drainage, see:

Increasing Temperatures in Alaska's National Parks
Lost Arctic Lakes

For more information about tundra fires, see:

In Alaskan Arctic, Tundra Wildfire Drives Large Loss of Nutrients from Terrestrial to Aquatic Ecosystems
NASA Studies How Arctic Wildfires Change the World
Tundra and Boreal Soils Response to Fire

Have you noticed changes to the landscape where you live? Is it wetter or drier than it used to be?

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