Dating and melting
You can think of the Arctic permafrost as a giant kitchen freezer.If you put organic (carbon-based) matter in your freezer, the food will stay intact. And as the bacteria consume the food, they produce carbon dioxide, methane, and other gases and chemicals that smell terrible.
Permafrost is a layer of frozen soil that covers 25 percent of the Northern Hemisphere.“Plants are growing in permafrost regions, and when those plants die, because of the cold temperature, they don't fully decompose, so some of that organic carbon is left behind,” Holmes says.When the permafrost thaws, “it starts to rot, it starts to decompose, and that's what's releasing carbon dioxide and methane,” he says.But if the freezer compressor breaks, it will slowly heat up. For tens of thousands of years, permafrost has acted like a freezer, keeping 1,400 gigatons (billion tons) of plant matter carbon trapped in the soil.(That’s more than double the amount of carbon currently in the atmosphere.) Some of the plant matter is more recent, and some is from glacial ice ages that radically transformed a lush landscape into a tundra.