How thawing permafrost could fuel climate warming
The Arctic is warming more than twice as fast as the rest of the world, and some scientists believe that thawing permafrost — ground frozen since the last Ice Age — is about to release enormous amounts of climate-warming emissions.
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Just centimeters below the Earth’s surface is a ticking time bomb that could detonate as global temperatures rise. It’s called permafrost.
Permafrost is found at high altitudes in mountains such as the Himalayas, the Andes and the Southern Alps of New Zealand, as well as at the poles in Antarctica and, especially, in the Arctic.
Permafrost is a lot like concrete. In permafrost, ice binds together soil, rocks, sand and organic matter. Some of that organic matter includes the remains of plants and animals that have been frozen since the last Ice Age, more than 11,000 years ago.
Now, human-induced climate change – caused by the buildup in the atmosphere of greenhouse gas emissions from industrial activity, mainly the burning of coal, oil and natural gas – is raising global temperatures and driving heat waves that can cause permafrost to thaw. And as permafrost thaws, the organic matter locked within it is starting to decompose, a process that releases even more climate-warming carbon dioxide and methane into the atmosphere.
Scientists estimate that permafrost in the Northern Hemisphere alone holds about 1.5 trillion tonnes of carbon. That’s twice what is in the atmosphere now, and three times more than what humans have emitted since the Industrial Revolution began.
For now, the permafrost emissions are being absorbed by plants and trees and fueling their growth. But soon, scientists say, the emissions will be so high that the trees won’t be able to keep up.
How bad will it get?
Measuring changes in the permafrost is extremely challenging. Imagery and measurements taken by satellites can only tell us so much. Scientists also drop instruments into boreholes and measure greenhouse gas levels at the ground surface to learn what’s happening in the permafrost.
Permafrost really varies: some areas are mostly rock while others are mostly ice. Thaw in each of these cases has vastly different outcomes for carbon emissions.
The Intergovernmental Panel on Climate Change (IPCC) has laid out several possible trajectories for cumulative emissions up to 2100 in order to help guide policymakers. Those trajectories, last updated six years ago, envision a range of scenarios from aggressive attempts to rein in man-made, climate-warming emissions – the scenario recommended by scientists to keep average global temperatures from rising more than 2 °C above pre-industrial levels – to a scenario in which emissions continue unchecked. This ‘business as usual’ scenario could see temperatures rise by about 5 °C by the end of the century.
For the maps in this graphic, Reuters is using this highest – and perhaps most likely – emissions scenario.
Currently, the world is following the unchecked-emissions trajectory, with the burning of fossil fuels in electricity production, manufacturing and transportation responsible for the bulk of emissions today. Efforts to bring down emissions could be frustrated by the additional greenhouse gas burden from climate change impacts such as thawing permafrost; the IPCC scenarios don’t account for this phenomenon.
Permafrost covers almost 20 million square kilometers, or about five times the size of the European Union. With unfettered industrial emissions, nearly half of the world’s near-surface permafrost is expected to thaw within 20 to 40 years, according to an analysis published in March 2019 in the Nature journal Scientific Data.
A global concern
Permafrost plays a key role in balancing the planet’s temperature by freezing carbon-rich organic matter – a bit like frozen compost – and preventing its decay. When permafrost thaws, that decay starts up again, emitting carbon dioxide and methane.
Scientists fear that permafrost emissions – whatever the mix of carbon dioxide and methane – will outpace trees’ ability to absorb them.
There is more than three times as much carbon frozen in permafrost as in all of the forests on the planet, including the Amazon, scientists say.
Cycle of permafrost thaw
Emissions from thawing permafrost contribute to atmospheric concentrations of greenhouse gases, further fueling global warming.
The greenhouse gases are emitted largely by microbes, as they feed on thawing organic material in the permafrost. But plants and trees that die due to heat stress or fire also contribute; not only do the plants and trees stop absorbing carbon, they also release carbon they’ve accumulated.
The best way to prevent permafrost from thawing is to limit climate change by reducing fossil fuel emissions and protecting forests, scientists say. But once permafrost thaws, there’s nothing that can be done to stop the carbon from being released.
Northern exposure
Warmer temperatures in the Arctic are causing snow and ice to disappear. As ice covering the sea shrinks back, it exposes darker waters that absorb solar radiation rather than reflecting it back out of the atmosphere. This is called the albedo effect, and helps explain why the Arctic region is warming so much faster than the rest of the world. This chart shows how much average surface air temperatures have changed at different latitudes since 1960.
Most of the Northern Hemisphere’s permafrost occurs between 60°N and 68°N.
Smaller changes in surface air temperature happen across latitudes that have less land mass.
Most of the Northern Hemisphere’s permafrost occurs between 60°N and 68°N.
Smaller changes in surface air temperature happen across latitudes that have less land mass.
The Siberian Arctic town of Verkhoyansk in June registered a record high temperature of 38 degrees Celsius (100.4 Fahrenheit) during a prolonged heat wave.
Record fires have also engulfed vast swathes of Siberian Russia, emitting more carbon dioxide than Switzerland or Norway do in a year.
The boreal forests of the Arctic have evolved to survive and thrive from occasional fires that would naturally occur every few decades or centuries in the region. But the more recent fires are different, scientists say. They are starting months earlier than they ever have before, and are smoldering through the winter as underground ‘zombie fires.’
The more intense fires are also burning up peat bogs. A forest might grow back in a few decades and reabsorb the carbon it released when it burned; a peat bog is the accumulation of thousands of years of partial decomposition.
Trouble in the Arctic
Permafrost has long been a solid base for construction, but a thawing Arctic is changing that. When the frozen ground thaws, it shifts and subsides unpredictably.
A fuel tank at a power station run by a nickel mining company in the remote Russian city of Norilsk lost pressure on May 29 and leaked 15,000 tonnes of diesel into the local river system and an additional 6,000 tonnes into the surrounding subsoil.
The company’s billionaire co-owner, Vladimir Potanin, blamed thawing permafrost driven by climate change as one reason for the spill, saying it eroded the tank’s foundation.
In a 2018 study published in Nature, scientists found 69% of all Arctic infrastructure could be at risk of damage by mid-century due to thawing permafrost. More than 3.6 million people live in the areas that will be affected.
Potential risk of infrastructure damage
Severity of risk for near-surface permafrost areas as measured under the ‘business as usual’ scenario where no additional climate change measures are in place by 2080
Scientists already have found dramatic signs of permafrost thaw: in Siberia, giant craters are forming as gases from decomposing matter build up underground and then explode.
Sources: Hjort, J., Karjalainen, O., Aalto, J. et al. Degrading permafrost puts Arctic infrastructure at risk by mid-century. Nat Commun 9, 5147 (2018); Karjalainen, O., Aalto, J., Luoto, M. et al. Circumpolar permafrost maps and geohazard indices for near-future infrastructure risk assessments. Sci Data 6, 190037 (2019); Brown, J., O. Ferrians, J. A. Heginbottom, and E. Melnikov. 2002. Circum-Arctic Map of Permafrost and Ground-Ice Conditions, Version 2. Boulder, Colorado USA. NSIDC; National Snow and Ice Data Center; NASA Goddard Institute for Space Studies; United Nations Environment Programme; Natural Earth; Indiemapper
Edited by Katy Daigle and Rosalba O’Brien