Deepening Arctic snowpack driving ancient greenhouse gas emissions
Human-caused climate change is altering snow cover in the Arctic; some regions with more, some with less. Using the longest snow manipulation experiment in Arctic Alaska, new research reports that deeper snow has led to permafrost thaw and thus the release of ancient carbon into the modern atmosphere. This amplification of carbon emissions taking place throughout the year may accelerate the progressive increase in atmospheric CO2 levels, global warming, and changes in the weather and climate of the north and beyond.
The research was led by University of the Arctic Research Chair, Jeff Welker of the University of Oulu and Dr. Claudia Czimczik of the University of California. New research uses Welker’s long-term International Tundra Experiment (ITEX) research program in Arctic Alaska funded continuously by the National Science Foundation. “This is the first study to directly measure and ages (using isotope techniques) mobilized ancient carbon emissions year-round. And, it shows that deeper snow, a realistic climate scenario, and currently being observed in many stations around the Arctic, has the potential to relatively quickly mobilize carbon deep in the soil, that was previously frozen for thousands of years” says Jeff Welker, Professor in the Ecology and Genetics Research Program at the University of Oulu.
“This study is the culmination of over 20 years of research at this site by my ITEX program. We first reported in 1998 that these Arctic exhibited measurable amounts of CO2 being emitted from these landscapes through the snowpack, an observation that stunned some scientists of the Arctic community; and that the rates of CO2 emissions were even higher where snow was deepened by our snow fence experiment”, says Professor Welker.
“Now we know why deeper snow keeps the soils from getting very very cold in winter (warmer than thin snow areas), facilitating permafrost thaw, winter and summer microbial decomposition of the organic matter, and that some of the winter and the summer CO2 emissions are ancient carbon (thousands of years old and previously frozen). These findings depict the importance of long-term studies and the value of using radiocarbon techniques to delineate the sources and ages of CO2 emissions across the changing Arctic”, Welker continues.
Moist snow measurements.
The team’s findings suggest that even if humanity stopped emitting planet-warming gases like carbon dioxide immediately, ancient carbon emissions from Arctic sources would still continue. “The implications are that if the climate models are right and the observations continue to show an increase in snow, then in addition to the strong warming, the snow will greatly accelerate emissions from permafrost”, says Czimczik”
Current climate change is causing snow and ice to retreat across much of the Arctic. But the same warming driving the retreat is also driving increased evaporation and, therefore, precipitation in certain regions. The deeper the snow gets, the more heat the snow traps in the soil each autumn when a blanket of snow covers the landscape. This causes the upper layers of the permafrost to thaw, which allows microorganisms to consume the thawed organic matter and, in the process, release planet-warming gases.
“Permafrost emissions are going to start earlier than we expected in most of our models,” says Czimczik. “We have an opportunity to control the emissions that are under our human control, otherwise these are going to further derail us from our climate mitigation targets.”
The research article: Pedron, S. A., Jespersen, R. G., Xu, X., Khazindar, Y., Welker, J. M., & Czimczik, C. I. (2023). More snow accelerates legacy carbon emissions from Arctic permafrost. AGU Advances, 4, e2023AV000942. https://doi.org/10.1029/2023AV000942