Cave Deposits Reveal a Permafrost-Free Arctic
By Kaja Šeruga, Eos/AGU.
Excerpt: About 15% of the land area in the Northern Hemisphere is currently covered by perennially frozen soil known as permafrost. But that has not always been the case. As global temperatures fluctuated in Earth’s past, patches of that frozen soil periodically thawed and refroze. A recent study in Nature Communications shows that the Arctic was mostly free of permafrost 8.7 million years ago, when the average global temperature was 4.5°C (8.1°F) higher than it is today. Permafrost is a huge reservoir of CO2, and thawing comes with repercussions because it feeds back into future warming. ...As permafrost thaws, the organic matter in the soil begins to decompose, releasing carbon dioxide and methane into the atmosphere. The Intergovernmental Panel on Climate Change estimates 14–175 billion tons of CO2 could be released into the atmosphere by thawing permafrost for every 1°C of global warming....