PNAS - Carbon Spike From AK Permafrost Melt Now Bigger Than Carbon Uptake In AK Forests
Soaring temperatures in the Arctic have triggered a huge seasonal surge in carbon dioxide emissions from thawing permafrost and may be tipping the region toward becoming a net source of heat-trapping greenhouse gases, a new study shows. Even into early winter, when the ground would have been frozen 40 years ago, microbes in the permafrost are continuing to release heat-trapping greenhouse gases. Carbon dioxide emissions are now outpacing the uptake of CO2 during the spring and summer growing season, the study suggests.
The study's authors, researchers from Harvard, the National Oceanic and Atmospheric Administration and other institutions, measured atmospheric CO2 in Alaska and found that emissions from October through December have increased by 73 percent since 1975 and that the increase correlates with rising summer temperatures.
The findings suggest that global climate models are underestimating how much greenhouse gas pollution will be unleashed as the Arctic continues to warm at twice the global average rate, said lead author Roisin Commane of the Harvard School of Engineering and Applied Sciences.
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Year-round measurements of CO2 emissions from permafrost have been sparse up to now, and some widely cited studies suggested that rising emissions from thawing permafrost were offset by increased uptake from Arctic forests. But according to the new research, those calculations need to be revised. Plants inhale massive amounts of CO2 in the spring and summer growing season. Then, in the fall and winter, the plants die and decompose, releasing CO2 and methane. That cycle gives the global CO2 level its signature zigzag pattern. In the Arctic, emissions during the decomposition phase are outpacing CO2 uptake during the growing season, according to the study.
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https://insideclimatenews.org/news/08052017/arctic-permafrost-thawing-alaska-temperatures-co2-emissions
