Methane Geogas Storages Discharge under Permafrost Degradation

High-latitude ecosystems are in the focus of global change studies. High-latitude ecosystems contribute up to 30% of all wetlands methane emissions according to AR4. High-latitude ecosystems are characterized with permafrost distribution. More than 107 km2 in the northern hemisphere is covered with permafrost. Permafrost soils were shown to contain layers enriched in methane and carbon dioxide as well as with pre- cursors needed for methane production and viable methanogenic microbial community. Thus the ancient methane itself, the substrate for its production and producers themselves are found in permafrost. They concentrated in various strata, geologic formations. For the North-Eastern Siberia a number of the strata were sampled for these components. More than 200 soil air samples from the cores of twenty 15-55 m boreholes were analyzed for methane and carbon dioxide concentration. The traces of acetate were also found in frozen soils. Labelled substrate experiments with soils in the laboratory gave the rates of methane production and lag phases of microbial communities for the various types of thawing permafrost soils. The volumes of the formations are calculated within the GIS based system according to state geological survey map of quaternary deposits of 1:1000000 scale. The land area was separated into three various morphologic levels dominating in the study area, as follows: Ice Complex covered watersheds, Alas Complex (Holocene Thaw Lake Depressions Deposits) and River Floodplains. The thickness and set of geologic formations for each morphologic level were specified. The study area was divided into 2.5 by 2.5 degrees Lat-Long grid to introduce to permafrost thawing model. Soil thermal characteristics were taken from the data available in literature or calculated on the basis of existing data on texture and iciness. The boundary conditions of ground surface temperature and water flow were controlled by the ensemble of GCMs models which ran under A1B and A2B emission scenarios to the year of 2100. The highest discharge of in situ methane is found for the Alas Complex covered layers occurring at 31% of the land area in the North-East Asia (the 68- 72°N, 147-162°E). The Ice Complex watersheds lacking the in situ methane and microbial community was found to support the high rates of methane production through assimilation of buried substrate by modern methanogenic communities of the active layer. Our assessment is based on the direct measurements of gas concentration within permafrost samples. The total assessment of possible efflux from permafrost of the studied area is somewhat lower than it was predicted by several studies on thermokarst conducted at Kolyma Lowland and in Alaska. Uncertainties in those assessments were analyzed.