Siberian lakes release more methane than previously thought
Methane bubbles from Arctic lakes contribute far more to the increase in greenhouse gases than previous measurements suggested. Overall, 10 to 63 percent more methane escapes from the arctic wetlands, report Katey W alter from the University of Alaska in Fairbanks and her colleagues. A large part of the mobilized carbon stocks comes from the ice ages.
The scientists had set up traps for rising methane in various lakes of the mammoth steppe above individual upwelling foci. Bubbles frozen in the ice had given them their positions. The subsoil of this region consists of several meters thick loess deposits that are extremely rich in organic residues. As the edges along bodies of water there increasingly thaw due to rising temperatures, this carbonaceous matter enters the lakes, where it is decomposed into methane under oxygen-free conditions. However, since it is difficult to record the spatially and temporally varying gas upwellings, previous estimates of their magnitude have been very imprecise.
Through their measurements, the researchers determined that the rising bubbles comprise 95 percent of the methane released from these lakes, with the rest escaping through molecular diffusion. Most of the gas escaped from veritable hotspots that gave off up to thirty liters of methane per day. Large amounts of methane were released, particularly along the lake shores where the permafrost is thawing. Isotope analyzes showed that the organic matter decomposed near the hotspots came almost exclusively from Pleistocene deposits, i.e. about 40,000 years "Image" was. The authors calculated that 41 to 83 percent of the methane released from Siberian lakes can be traced back to Pleistocene sediments. alt="
Based on satellite data, the researchers estimate that the area of such meltwater lakes resulting from thawing permafrost increased by almost 15 percent between 1974 and 2000. Accordingly, methane emissions are likely to have grown regionally by 58 percent.
