Alaskan jäätikkö. Kuva Jacqueline Schmid Pixabaystä

Arctic CO2 emissions: Will snowy winters hasten climate change?

Large layers of permafrost underlie much of the Arctic landscape. The thawing of these layers has major consequences across the north. Permafrost holds a pool of carbon that is about three times that of all the carbon in the global atmosphere today. Small changes in thaw and emissions of ancient carbon may result in big changes across the landscape and to the Earth’s atmospheric chemistry.

The increases in permafrost thaw is raising questions regarding the seasonal patterns and magnitudes of ancient carbon emissions, including the magnitude of these emissions in winter. Especially, how does different snow accumulation patters and depths between years effect ancient carbon emission rates? By measuring the 14C traits of ecosystem respired CO2 and 14CO2 in the soil, Professor Jeff Welker and his team can age the gas, just as they age ancient bones or archaeological artefacts.

Professor Jeff Welker is leading a research group which aims to track the process and analyse the impacts of increasing carbon emissions taking place across the Arctic. These impacts include changes in the Arctic’s carbon and water cycles. Welker is the University of the Arctic Research Chair and a professor in the Ecology and Genetics Research Unit at the University of Oulu and the University of Alaska Anchorage. He is the vice-chair of the profile area Arctic Interactions and Global Change in the University of Oulu.

Welker and his team have found a link between the snow coverage and the rate of ancient carbon being emitted to the atmosphere, in part by using his long-term snow manipulation experiments and 14C dating.

“We have found that in a snowier Arctic, like this winter in Lapland, more and more ancient carbon is emitted to the atmosphere” Welker says.

In winter, the deep snow isolates the soil from the very cold Arctic air, forming a warming layer between the air and the soil. Warmer winter soil temperatures allow higher rates of microbial decomposition and lead to a deeper active layer and permafrost thaw.

Welker brings the findings to a wider context with the notion that the ancient carbon emitting from the tundra to the atmosphere may be adding to the rising CO2 concentrations, especially over the past 10 years. Thus, ancient carbon emissions may and will likely be adding to future climate warming, future sea ice loss and cascading consequences across the north and beyond.

He explains that, in the last 50 years the amount of CO2 in the atmosphere has been rising about 1 ppm/year but now the rate of CO2 increases has doubled to almost 2 ppm/year.

“We believe that part of that increase is due to ancient carbon moving from deep in these soils to the atmosphere”, says Welker.

American scientist Dr. Amanda Young and Danish colleague Dr. Stine Pedersen collecting soil CO2 in Toolik Lake Field Station in Alaska.


American scientist Dr. Amanda Young and Danish colleague Dr. Stine Pedersen collecting soil CO2 in Toolik Lake Field Station in Alaska.

Artic research year round

Welker and his team measure the rates of carbon loss and analyse the sources and ages of the CO2. This research occurs at the Toolik Lake Station in Arctic Alaska during spring, summer and autumn. The researchers have now designed a system that allows them to collect samples and make measurements in winter as well.

The team has set up wells that collect carbon dioxide from different depths in the soil. Some of the traps go deep down to permafrost and some collect CO2 from near the ground surface. The carbon dioxide that is produced by microbes in the soil is collected in molecular sieve traps continuously. Traps are replaced in intervals of approximately 6 weeks. These integrated samples provide a much more robust data set than the team’s earlier studies on Greenland and Svalbard, where they collected samples on a single day. Now the measurements cover much longer periods of carbon emissions.

The samples are shipped to University of California, Irvine. The scientists then age the carbon, as one might age a bone or a mummy, using 14C aging. The results tell them what is the age of the carbon being produced and then emitted into the atmosphere. The scientists are interested in both modern and ancient carbon in the Arctic carbon cycle. Welker and his team use mixing models to estimate the fractions of ancient carbon being emitted.

 

Text: Raita Niva & Aino Soutsalmi

Last updated: 6.5.2020