Siberian Caves Reveal Potential for Devastating Permafrost Thaw

Across the Arctic tundra and in Siberia there are vast stretches of frozen ground which never thaw, even during the height of summer. This permafrost has lasted for thousands of years. Now, though, scientists have announced that a mere global temperature rise of 1.5 C would be enough to start the melting of Siberian permafrost; this could have devastating consequences for the people that live there and for our atmosphere.

Permafrost covers about 24 percent of the land surface in the northern hemisphere, according to The Guardian. The permanently frozen ground actually contains gigatonnes of carbon dioxide and methane. When the permafrost melts, though, these gases are released into our atmosphere and accelerate the warming trend.

In order to study the melting permafrost and test how susceptible it might be to rising temperatures, researchers, led by experts from Oxford University, studied stalactites and stalagmites in Siberian caves that have formed over hundreds of thousands of years. These rock formations were created during periods of gradual melting, when meltwater slowly dripped into the caves and brought with it minerals that slowly hardened. When the area froze again, though, this growth stopped. Scientists cut through these structures at various points that corresponded to various time periods in the Earth's history. By examining these cores, they could measure the growth and halt of the stalactites and stalagmites.

The researchers found that the stalactites in one northern cave on the boundary of continuous permafrost grew about 400,000 years ago. At that time, temperatures were only 1.5 C higher than in pre-industrial times. This means that permafrost was most likely melting at that time, which could mean dire consequences if our own temperatures rise by that much.

Yet researchers also found that for the same period, the stalactites in another cave, called the Ledyanaya Lenskaya cave, did not grow. This showed that permafrost remained intact in that area at those temperatures. Nonetheless, it also hints that 1.5 C is a tipping point for permafrost.

Currently, global average temperatures are about .7 C above pre-industrial levels. This means that scientists who create climate models should include the possibility of melting permafrost, especially because it would have such an impact on Earth's climate and atmosphere. Consequences could include increased warming due to the release of gases, and could change the climate in the surrounding areas. For example, it's possible that Mongolia's Gobi Desert could become much wetter than it is today.

Researchers are unsure how fast or how widespread this melting would be as temperatures rise. One thing is certain, though: melting permafrost could cause serious consequences.

The findings were published in the journal Science Express.