The Arctic is warming more quickly than almost any other region on Earth as a result of climate change. One of the better known: the continually shrinking summer sea-ice extent in the Arctic. But global warming is also leaving its mark on terrestrial permafrost. For several years, permafrost regions have been thawing more and more intensively in North America, Scandinavia and Siberia — e.g. in the extreme northwest of Alaska. Permafrost is soil that has remained permanently frozen to depths of up to several hundred metres, often since the last glacial period, roughly 20,000 years ago, or in some cases even longer.
The permafrost regions near the city of Kotzebue, Alaska, are dotted with hundreds of thaw lakes. These are formed when the permafrost soils begin to thaw and subside. Meltwater from the soil or from the winter snowfall and summer rainfall collects in the hollows. Some are several thousand