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Climate Change Concerns Rise As Cave Deposits Show Surprising Shift in Permafrost Over the Last 400,000 Years

Researchers from the US and Canada found evidence in mineral deposits from caves in Canada that permafrost thawing took place as recently as 400,000 years ago, in temperatures not much warmer than today. But they did not find evidence the thawing caused the release of predicted levels of carbon dioxide stored in the frozen terrain. Credit: Jeremy Shakun, Boston College Study finds Earth’s frozen surfaces became less susceptible to thawing, potentially locking in more carbon than expected.

Nearly one quarter of the land in the Northern Hemisphere, amounting to some 9 million square miles, is layered with permafrost — soil, sediment, and rocks that are frozen solid for years at a time. Vast stretches of permafrost can be found in Alaska, Siberia, and the Canadian Arctic, where persistently freezing temperatures have kept carbon, in the form of decayed bits of plants and animals, locked in the ground.

Scientists estimate that more than 1,400 gigatons of carbon is trapped in the Earth’s permafrost. As global temperatures climb, and permafrost thaws, this frozen reservoir could potentially escape into the atmosphere as carbon dioxide and methane, significantly amplifying climate change. However, little is known about permafrost’s stability, today or in the past.

Now geologists […]

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