Vanishing Sea Ice Makes Permafrost Vulnerable to Thawing

(CN) – Less summer sea ice in the Arctic can lead to increased thawing of what was once permanently frozen land – a relationship that has potentially dangerous consequences for Earth’s climate, according to a study published Wednesday.

The study in the journal Nature details how an international team of researchers discovered a shocking historical connection between ground that stays frozen year-round, known as permafrost, and the summer sea ice in the Arctic. Researchers found that permafrost thaw has occurred throughout history, but not always in tandem with increased global temperatures; instead, permafrost thawed during times when there was less summer sea ice.

This image taken from a helicopter in the High Arctic shows cracks in the permafrost. (Brocken Inaglory/Wikipedia)

Gideon Henderson, one of the authors of the study and professor in the Department of Earth Sciences at the University of Oxford, said this newfound connection suggests that with increased ice loss in the Arctic becoming a more profound issue in recent years, continued sea ice loss could have a significant influence in areas within the Northern Hemisphere with large amounts of permafrost like Siberia.

“We were surprised to find that times when permafrost melted in the past did not simply match up with times when Earth was at its warmest, but were much more likely when the Arctic was free of ice in the summer,” Henderson said in a statement accompanying the study. “This discovery about the past behavior of permafrost suggests that the expected loss of Arctic sea ice in the future will accelerate melting of the permafrost presently found across much of Siberia.”

Researchers made the discovery through a somewhat surprising means: exhaustive examination of stalagmites in Siberian caves. Scientists used mineral dating techniques to trace the ages of stalagmites and, given the kind of frost conditions needed to form stalagmites, used their ages to create a timeline on when permafrost thaw took place throughout Earth’s natural history.

It was this data that helped researchers discover the connection between increased permafrost thaw and decreased amounts of Arctic sea ice, a connection that has never been fully established before this study.

Researchers say there are several reasons why this crucial relationship exists in the first place. Less ice in the Arctic means warmer air moves from the ocean to nearby landmasses like the icy tundra of Siberia, leading to permafrost land undergoing increased thaw.

Furthermore, less sea ice leads to more moisture over land in the form of more frequent snow in autumn. While many some would think more snow means less thaw, researchers say snow acts as a blanket to protect the ground from the far more drastic winter temperatures that are to come.

The discovery is so important because it helps to not only explain the trends of permafrost thaw throughout history, but also sheds light on how permafrost thaw will occur in the future. This information could be critical to global communities around the world since permafrost contains massive amounts of carbon trapped beneath its crust for at least a thousand years. Once the permafrost thaws, the carbon has nowhere to go but into Earth’s atmosphere.

Since carbon is a leading greenhouse gas, researchers warn emissions from thawing permafrost could be potentially dangerous and consequential contributors to Earth’s ongoing struggle with climate change.

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