The Arctic does not only consist of pack ice on the ocean. The land masses surrounding the Arctic Ocean are in many cases frozen soils that thaw at the surface only in summer and then refreeze. These permafrost soils have always been considered a carbon sink because they hold vast amounts of organic material, sequestering carbon that would otherwise be released into the atmosphere as greenhouse gases. But as the Arctic warms, the sink is increasingly becoming a source. An international study with AWI participation shows how strong this source is and will be.
If push comes to shove and global warming continues to gain momentum in the Arctic, permafrost could release more greenhouse gases than the entire United States has in its 150-plus years of industrial development. As a result, the climate could warm even faster and tipping points could be passed more quickly than previously assumed. That’s one of nine scenarios obtained by an international research team led by Northern Arizona University NAU and the International Permafrost Carbon Network, based on an extensive study. The team, consisting of 21 scientists, now hope their work, published in the journal Annual Review of Environment and Resources, will provide important help for policymakers to reconsider and redefine climate targets. This is because, according to the study’s findings, the extent of emissions depends primarily on efforts to curb warming.
The research team, led by lead author Professor Ted Schuur of NAU, used not just a few studies, but collected more than a decade’s worth of work to build a comprehensive and more detailed picture of the impact of greenhouse gas emissions from permafrost on global warming. For the first time, hydrological and biogeochemical dynamics and local tipping points were also considered. The latter in particular are very important, as at individual sites in the Arctic researchers have observed sudden thawing and nonrefreezing of the ground. Such places are already more of a carbon source than a carbon sink, and the authors estimate that about 20 percent of the entire permafrost region is already threatened, and the situation is worsening at an accelerating rate. “Changes we are witnessing in the field show the urgent need to curb emissions and keep permafrost carbon in the ground,” says Ted Schuur.
The head of permafrost research at the Alfred Wegener Institute AWI, Dr. Guido Grosse, who is also a co-author of the study, puts it into perspective: “Permafrost emissions will be a large and substantial contributing factor to atmospheric greenhouse gases, no matter which of the possible scenarios becomes reality.” But the study shows that how much countries reduce their emissions will have a significant impact. If global warming could be limited to 2°C or below through the rapid implementation of emissions reductions or even stopps, the amount of carbon escaping from permafrost in the form of greenhouse gases, such as carbon dioxide and methane, would be about 4.5 times less than if nothing were done. In the case of the latter, even greater efforts would then have to be made to mitigate the effects of climate warming, because “the role of permafrost would be even more significant in warming and forms a bigger hurdle,” he continues.
However, the study not only provides various emissions scenarios, but the authors also highlight ways in which efforts could be made to create even better and more accurate models. Above all, they are relying on even better remote sensing techniques using satellites with even more accurate measuring instruments. Because that would allow more accurate models to be created locally instead of just globally or regionally. But such satellites are few and far between, which is why the team is calling for more cooperation from the international community and extending the call to emissions reduction efforts.
However, considering the prevailing geopolitical reality, due to which for example information and work on permafrost comes from only less than 50 percent of permafrost areas, it will likely be some time before these calls can be put into action.
Dr Michael Wenger, PolarJournal
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