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The simplest definition of permafrost is ground that has been frozen for at least two years. But it’s so much more than that. In much of the Arctic, that ground has been frozen for tens of thousands of years. And a huge amount of it is frozen — permafrost rests in 25% of all the land area in the northern hemisphere.

The top few feet of the permafrost is what’s known as the “active layer.” This topsoil does thaw with yearly seasonal changes, and is home to a thriving ecosystem. So how do scientists know there’s permafrost underneath it? They have these things called thaw depth probes, which is basically just a T-bar, a steel rod that's a centimeter in diameter and 1.5 meters or so long. They poke the ground with it. Eventually, if you dig deep enough, the permafrost again thaws due to heat from the Earth’s core.

There are dangers buried in the permafrost. But there are also natural treasures yet to be discovered. The ice preserves all ancient animal remains and human history in the region. Think of Ötzi, the remarkably preserved 5,000 year corpse found in the Alps. If he had thawed, what was left of his body would have decomposed, and a window into the world he lived in would have been lost forever. There may be other Ötzis in the Arctic. Or preserved bits of mammoth DNA yet to be discovered. The melting may make some of these treasures briefly accessible but also threatens to quickly destroy them. According to Scientific American, once a specimen is uncovered and thawed, researchers have a year at most to recover it before it completely breaks down.

This is the fifth part of a 5 episode series on climate change and new diseases. You can check them all out using this link.


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