Permafrost, or permanently frozen ground, contains 1.5 trillion grams of carbon worldwide, double the amount currently in the atmosphere. Alpine permafrost alone, which (unlike arctic permafrost) is found closer to the equator at high elevations like the Tibetan Plateau, contains 85 trillion grams of carbon.
The permafrost in these areas is likely to thaw faster in the face of climate change, and when this happens large amounts of carbon dioxide and methane stored in the ice will be released, further driving climate change.
As a result, the climate on Earth will be similar to that of the mid-Pliocene warm period, between 3.3 million and 3 million years ago, when the extent of permafrost was much less than it was. is today, according to a team of scientists. .
“Atmospheric carbon dioxide concentrations today are similar to or even higher than those of the Middle Pliocene due to the burning of fossil fuels, so scientists refer to this period as an analogue of our present climate and the near future. “, explains Carmala. Garzione, dean of the University of Arizona College of Science, author of a new study.
“We are not yet feeling the full effects of increased atmospheric carbon dioxide because our Earth system is taking time to adjust,” Garzione notes. “The Pliocene is an important time as an ancient analog of how the Earth will adapt to the carbon dioxide that humans have already released into the atmosphere.”
Examination of Tibetan permafrost
Scientists examined fine-grained carbonate minerals at the bottom of a lake on the Tibetan Plateau, which sits more than 4.5 km above sea level and has the largest region of alpine permafrost in the world. planet, to estimate the temperature range during the Pliocene period from 5.3 million to 2.6 million years ago and the Pleistocene period from 2.6 million to 11,700 years ago.
The team then created a computer model of what the climate was likely to be like during the Pliocene. What they found was that “not only was the average temperature of much of the Tibetan Plateau above freezing in the Pliocene, but so was many of the alpine regions around the world,” they explain.
“Ultimately, the model suggests that at current levels of atmospheric carbon dioxide, 20% of Arctic permafrost land area and 60% of Alpine permafrost land area will be lost in the future.
High altitude alpine regions are more sensitive than high latitude arctic regions to warming under higher atmospheric carbon dioxide conditions.
In other words, the alpine regions, which also include the Mongolian Plateau in Central Asia, the Rocky Mountains in North America and parts of the Andes in South America, will be particularly vulnerable to rising temperatures over the coming decades. .
“Much attention has been paid to the stability of Arctic permafrost, as it covers more land and contains a large pool of organic carbon trapped in permafrost, but we also need to be aware that alpine regions can lose more permafrost proportionally and are important to understand the potential release of carbon under global warming scenarios,” Garzione points out.
By Daniel T. Cross. Articles in English