Methane released by thawing permafrost from some Arctic lakes can significantly speed up climate change, according to a new Fairbanks study by the University of Alaska.
The study, published on August 15 in the journal Nature Communications focuses on the carbon that is released by thawing permafrost under thermo-smokers. Such lakes develop when heating soil, causing ice to melt out of the ice, causing the surface to collapse and creating water basins. Those pools speed up permafrost thawing among the expanding lakes, providing food for microbes that produce the greenhouse gases carbon dioxide and methane.
Main author Katey Walter Anthony and her colleagues studied hundreds of thermal lakes in Alaska and Siberia over a period of 12 years, measuring their growth and how much methane bubbled to their surface. By combining fieldwork results with remote sensing data of changes in the lake over the past two years, they have determined that the "abrupt defrosting" among such lakes is likely to release large amounts of permafrost carbon in the atmosphere this century. The activity on the lake could double the release of terrestrial landscapes by 2050.
The effort, carried out by a team of American and German researchers, is part of a 10-year NASA-funded project to better understand the effects of climate change on climate change. Arctic. Additional support from the National Science Foundation enabled scientists from the UAF and the Alaska Division of Geological and Geophysical Surveys to collect data on permafrost location, defrosting and associated greenhouse gas emissions from lakes in the Goldstream Valley in the Alaskan interior.
The researchers found the introduction of greenhouse gases under thermoconstrictors is relatively fast, with deep defrosting taking place over decades. Permafrost in terrestrial environments generally experiences shallow seasonal defrosting for longer periods of time. The release of that surface permafrostaarde carbon is often compensated by increased growth in vegetation.
"Thermokarst lakes offer a completely different scenario: when the lakes form, they defrost these permafrost areas," said Walter Anthony, associate professor at UAF's Water and Environmental Research Center. "Instead of centimeters thaw, which is common for terrestrial environments, we have seen 15 meters of thaw under newly formed lakes in Goldstream Valley in the last 60 years."
Emissions of thermo-smokers are currently not included in global climate models because their small size makes individual lakes more difficult to make. However, the authors of the study show that these lakes are hotspots of permafrost carbon release. They claim that not including them in global climate models overlooks their feedback effect, which occurs when greenhouse gas emissions from permafrost promote global warming. This feedback is important because methane is about 30 times more potent than carbon dioxide as a heat-retaining gas.
Existing models currently attribute about 20 percent of the permafrost carbon feedback from this century to methane, while the remainder is due to carbon dioxide from terrestrial soils. By incorporating thermo-pollutants, methane becomes the dominant driver, responsible for 70 to 80 percent of the warming caused by carbon permafrost by this century. By adding thermokarst methane to the models, the effect of the feedback is comparable to that of land use change, the second largest source of man-made warming.
In contrast to shallow, gradual thawing of terrestrial permafrost, the abrupt thaw under thermo-polluting is irreversible this century. Even climate models that project only moderate warming of this century must, according to the study, include their emissions.
"You can not stop the release of carbon from these lakes as soon as they form," said Walter Anthony. "We can not circumvent this source of global warming."