Soil is the world’s largest terrestrial carbon pool. It stores an estimated 2300 Pg of carbon, while the atmosphere and plants only store 700 and 1500 Pg, respectively. The carbon is soil comes from decaying plants, insects and microbes that once lived there. Frozen soils store more carbon than those in temperate places, because freezing prevents further decay of the plants that grow and die in the thawed, surface soil. Much of Greenland is covered in a layer of soil called permafrost, which has been frozen for at least two years. The frozen soil is overlain by thawed soil, so plants, grasses, and billions of microbes thrive across the landscape. Exactly how much carbon is stored in the thawed and permafrost soils in Greenland is not known. For one, sampling permafrost is very challenging—it is often deep, making it difficult to access, and it is completely solid. A shovel will not get the job done.
This year I brought a gas-powered, two man augur to Greenland to try a different method of soil sampling. A 70 cm diamond-tipped bit accompanied the drill, which is capable of coring through granite rocks. Fortunately, the drill bit WAS capable of cutting through permafrost. The bad news was that the frozen soil was too deep for us to reach in many locations that we sampled. We also had difficulty extracting the frozen core after it was cut. Although we were not successful in bringing home permafrost on our first trip, I am already scheming for a better design next year.
After our venture into permafrost extraction, we completed a nice study of the thawed, mineral soil layers down to 65 cm. We sampled 10 locations covered in grass and 10 locations covered in shrubs. We expected to see differences in the carbon content of the soil in the two vegetation types. Julia Bradley-Cook, who is working on her dissertation research in Greenland, has detailed GIS maps of vegetation types for the area. This study should give us a better understanding of the soil carbon storage underlying the surface vegetation. If vegetation is a scientifically rigorous predictor of carbon content in deeper soils, we may be able to determine how carbon is stored in grasses and shrublands in the Kangerlussuaq area.