Permafrost explained: Stunted plants and pot hole lakes are features of tundra

The huge hole in the Siberian region of Yamal could have happened only in the kind of landscape known as tundra, which is characterized by a permanently frozen layer of ground under a warmer, “active” layer where stunted plants grow during brief summers.

Even in the summer if you dig deep enough on the tundra, maybe just a few feet, maybe several, you’d hit frozen ground — permafrost. But, in the summer, as anyone who has walked across the tundra in summer’s endless daylight will tell you, it seems anything but frozen. It’s green and spongy with puddles of water to avoid.

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Siberia “pothole” lakes. (NASA)

A couple of definitions:

Permafrost: Permanently frozen subsoil that maintains a temperature below 32 degrees continuously for two years or longer

Tundra: A treeless area, usually bounded by the ocean, ice-covered areas or the tree line in polar regions, having permanently frozen subsoil and supporting low-growing vegetation such as lichens, mosses, and stunted shrubs

The English word “tundra” comes from a Finnish word meaning “treeless plain,” which is a good description of Arctic tundra. In addition to the vast stretches of mostly flat tundra around the Arctic, “alpine tundra” is found in mountains at all latitudes, such as the Rocky Mountains in the West.

These areas obviously aren’t “plains” but they are otherwise like Arctic tundra with only small bushes because they have short growing seasons. Unlike deserts, which are too dry to support much vegetation, areas of tundra are too cold for too much of the year for plants to grow very large.

Arctic tundra stretches across approximately 5 million square miles northern Alaska, Canada, Europe and Asia. The tundra’s northern boundary is the Arctic Ocean, but you can’t draw a single latitude line that marks where it ends to the south. In the European Arctic, which is warmed by Atlantic Ocean currents, you can travel to around 71 degrees north latitude before moving onto the tundra. In some parts of eastern Canada, the tundra extends as far south as around 55 degrees north latitude.

If you considered only annual precipitation, you would expect the tundra to be a desert. For instance, the annual precipitation of 4.7 inches in Barrow, Alaska, is less that half of the 11.6 inches of Tucson, Arizona.

Yet, the summer tundra around Barrow is a solid green with some tiny flowers — except for the ponds — you see little green in the desert around Tucson.

Those tundra ponds make the difference. Thank the layer of permafrost a few feet below the surface of the tundra for keeping it from being a desert. When winter’s thin covering of snow begins to melt, the permafrost keeps the water on the surface, it can’t soak into the ground. The resulting bogs and ponds supply plenty of moisture for the variety of grasses, dwarf shrubs, and flowers of the summer tundra. Even after the top layer of the soil thaws, water can’t sink far into the ground.

This damaged building in Dawson City, Canada, shows what can happen when the warm interior of a building causes the permafrost underneath to thaw. (Andrew Slater via NSIDC.org)

This damaged building in Dawson City, Canada, shows what can happen when the warm interior of a building causes the permafrost underneath to thaw. (Andrew Slater via NSIDC.org)

While the name “permafrost” has a good, solid ring to it, permafrost is anything but stable, as people around the Arctic discovered long ago. If heated buildings are built directly on the ground their heat will begin melting the permafrost under the buildings, causing destructive, uneven sinking.

The Alaska pipeline, which runs about 800 miles from the oil fields on the Arctic Ocean to the port of Valdez, is a minor tourist attraction because over half of it is above ground. The reason: permafrost. Oil is pumped through the pipeline at about 120°, which keeps it flowing in cold weather. If the pipeline were buried like those elsewhere, it would melt the permafrost, allowing the pipeline to sag and break. This is why it’s on posts. The posts are built to be radiators that expel heat to the air instead of allowing it to flow into the permafrost.

Unlike the Northern Hemisphere with its huge area of tundra, only small areas of tundra are found in the Southern Hemisphere. Almost all of Antarctica is covered by ice with a few small areas of tundra on the Antarctic Peninsula, which reaches up toward the tip of South America. As in the Northern Hemisphere relatively small areas of alpine tundra are found on some Southern Hemisphere mountains.

Adapted from “The complete Idiot’s Guide to the Arctic and Antarctic,” copyright 2002 by Jack Williams.

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