Permafrost, a ground that has remained frozen for more than two years in a row, covers 30 million km2 on the planet, about half of which is in the Arctic. It contains double the CO2 present in the atmosphere and triple what has been emitted by human activities since 1850.
Temperatures in the Arctic are rising much faster than in the rest of the world as a result of climate change, by 2 ° C to 3 ° C above pre-industrial levels. The region also recorded a series of weather anomalies.
The permafrost itself experienced an average temperature rise of 0.4 ° C between 2007 and 2016,
raising concerns about the rapid rate of thaw and the potential for carbon release, notes a study led by Kimberley Miner, a researcher at NASA’s JPL space research center.
Their study expects about 4 million square kilometers of permafrost to be lost by 2100, even if global warming is contained.
Fires also play a role, the study points out. These wildfires could increase by 130% to 350% by mid-century, releasing ever more carbon from the permafrost.
Infrastructures in danger
A more immediate threat hangs over nearly 70% of roads, gas pipelines, oil pipelines, towns and factories built on permafrost, according to another study led by Jan Hjort, a researcher at the Finnish University of Oulu. Russia is particularly threatened.
Almost half of the oil and gas fields in the Russian Arctic are in areas at risk from permafrost.
In 2020, a fuel tank shattered when its foundation suddenly sank into the ground near Norilsk in Siberia, dumping 21,000 tonnes of diesel into nearby rivers.
In North America, the threat hangs over roads and pipelines as well.
While the science on permafrost is advancing, some questions remain open, particularly on the volumes of carbon that can be released.
Permafrost dynamics are often not included in Earth system models, which means that the potential impact on global warming is not adequately taken into account, Kimberley Miner and colleagues point out.
It is also unclear whether the thaw will lead to a greener Arctic region, where the plants will be able to absorb the released CO2, or on the contrary in a drier region, with an intensification of fires.