By the end of this century, permafrost in the rapidly warming Arctic will likely emit as much carbon dioxide and methane into the atmosphere as a major industrial nation, and potentially more than the United States has emitted since the industrial revolution began.
But this is only a possible future for the vast reserves of carbon locked up in the Arctic soil, previously perpetually frozen but now thawing. Using over a decade of synthesis science and region-based models, a new study conducted by Northern Arizona University and the international Permafrost Carbon Network and published in Annual review of the environment and resources predicts cumulative emissions from this “permafrost country” up to 2100 in low, medium and high warming scenarios.
“We hope these predictions on future Arctic carbon emissions will not only update the scientific framework, but act as new guidelines for policy makers who are working to stabilize the climate and avoid overshooting temperature targets,” he said. Ted Schuur, Regents Professor in the Department of Biology and Center for Ecosystem Science and Society at the NAU and lead author of the study.
The team estimates that in a low-warming scenario, which could be achieved if the global community limited warming to 2 ° C or less by reducing fossil fuel emissions, permafrost would release 55 petagrams (Pg) of carbon by the end of the century. in the form of greenhouse gas carbon dioxide (CO2) and methane (CH4). If nothing is done to mitigate global warming, the study estimates that the Arctic could release 232 Pg of carbon by the end of the century.
The team’s projections go beyond previous international forecasts by taking into account the unique hydrological and biogeochemical dynamics and tipping points in the permafrost zone.
For example, scientists are witnessing a sudden thaw in many permafrost regions, where rapid melting of permafrost ice causes the earth’s surface to collapse, form lakes or other changes in surface hydrology. Once previously frozen soil erodes or subsides, the carbon stored there can enter the atmosphere through microbial respiration or methane. Such rapid, nonlinear changes rapidly and permanently change the ability of permafrost to store carbon and could shift large swaths of the Arctic from carbon sinks to carbon sources. Recent estimates suggest that one fifth of the current permafrost soil is vulnerable to sudden thaw.
“Once permafrost carbon emissions increase in response to global warming, as some models predict, there will be no way to stop this process,” said Roisin Commane, assistant professor of earth and environmental sciences at Columbia. University and coauthor of the new study. “We may need to reduce our fossil fuel emissions much sooner than many governments currently plan to avoid triggering possible turning points in the Earth’s climate.”
The potential to traverse both regional and system-wide hotspots is one reason the history of Arctic carbon and its future safety remains only partially written. The new study describes nine different futures based on the evolution of global warming and the actions taken by global leaders to reduce fossil fuel emissions.
“Permafrost emissions will be an important and substantial factor contributing to atmospheric greenhouse gases, regardless of which of the possible scenarios becomes reality,” said Guido Grosse, head of the permafrost research section at the Alfred Wegener Institute in Potsdam, in Germany and co-author of the study. “But there will be huge differences between the mitigation scenarios that matter to the global global carbon budget.” Reducing human-caused emissions, Grosse said, will help ensure that permafrost makes a minor contribution to global climate warming, while “doing business as usual” will ensure that the permafrost “nation” plays a major role in warming. and will be a major obstacle to eliminating mitigation efforts.
As the Arctic is not regulated by any state and its remoteness makes the terrain difficult to monitor comprehensively, the authors point out that international efforts to reduce emissions must take this “country of permafrost” into account in climate goals and future actions. The study also highlights the importance of monitoring this rapidly changing region using collaborative networks such as the Permafrost Carbon Network and scientific tools such as remote sensing technology.
“Remote sensing products can really help us see and track what is happening at the permafrost in a physical way,” said Commane. “High-resolution sensors can see evidence of thermocarsal soil collapse, how water bodies are changing, and even how wet or icy soils are. But satellites telling us how much carbon from permafrost ends up in the atmosphere are limited. and there needs to be an investment by space agencies in these capabilities as soon as possible. “
Schuur said his research team is also seeing evidence of rapid change in the field.
“The changes we are seeing in the field show the urgent need to reduce emissions and maintain permafrost carbon in the soil. This summer, at my study site in Eight Mile Lake, Alaska, we witnessed widespread thawing of the permafrost after a winter with record snowfall, and carbon losses four times higher than the average of the last decades, “he said. “These observations correspond to the predicted tipping points in permafrost and carbon that we expect to see when man-made emissions from other parts of the Earth rapidly warm the Arctic.”
The study was written by an international team of NAU scientists, Alfred Wegener Institute, Columbia University, Brigham Young University, University of New Hampshire, University of Alaska – Fairbanks, Stockholm University, US Geological Survey, Lawrence Berkeley National Laboratory, National Center for Atmospheric Research, University of Colgate, University of Texas – El Paso, University of Alberta, Woodwell Climate Research Center, Oak Ridge National Laboratory and University of Colorado – Boulder. The Permafrost Carbon Network’s synthesis work is supported by a grant from the National Science Foundation.