Small Rise in Global Temperature may Trigger Permafrost Melt: Study

A new analysis on Siberian caves suggests that the permanently frozen ground (permafrost) in large parts of the country could thaw, if there is a global temperature rise of 1.5 degrees Celsius.

This could trigger the release of carbon from the soil and cause damages to natural and human environments. If the Siberian permafrost melts, it could release over 1,000 giga-tons of carbon dioxide and methane into the atmosphere, potentially increasing global warming.

An international team of experts led by Anton Vaks of Oxford University studied cave growths called stalactites and stalagmites across Siberia. Stalactites and stalagmites only grow when liquid rainwater and snow melt drips into the caves, and they record 500,000 years of changing permafrost conditions, including warmer periods similar to the climate of today.

The research team analyzed 36 speleothems (cave formation) in six caves and used radiometric dating techniques to date the growth of cave formations. They reconstructed the last 500,000 years of climate through the decay of radioactive particles in the stone, reports Scientific American.

Data obtained from the Ledyanaya Lenskaya Cave - near the town of Lensk (at latitude of 60 degrees North) - showed that the last time stalactite growth took place was about 400,000 years ago, when there was no permafrost at that latitude during that period.

The time correlates with the warm period (Marine Isotopic Stage 11), when the global temperature was 1.5 degrees Celsius higher than today. Even periods when the world was 0.5-1 degree Celsius warmer than today did not see any growth of stalactites in the northernmost cave, suggesting that around 1.5 degrees Celsius is warm enough to thaw even the coldest of permafrost regions, the researchers said.

"Although it wasn't the main focus of our research our work also suggests that in a world 1.5 degrees Celsius warmer than today, warm enough to melt the coldest permafrost, adjoining regions would see significant changes with Mongolia's Gobi Desert becoming much wetter than it is today and, potentially, this extremely arid area coming to resemble the present-day Asian steppes," Dr. Vaks said in a statement.

The findings of the study, "Speleothems reveal 500 kyr history of Siberian permafrost", are published in this week's Science Express.