Snowpack fluxes of methane and carbon dioxide from high Arctic tundra

Abstract

Measurements of the land‐atmosphere exchange of the greenhouse gases methane (CH4) and carbon dioxide (CO2) in high Arctic tundra ecosystems are particularly difficult in the cold season, resulting in large uncertainty on flux magnitudes and their controlling factors during this long, frozen period. We conducted snowpack measurements of these gases at permafrost‐underlain wetland sites in Zackenberg Valley (NE Greenland, 74°N) and Adventdalen Valley (Svalbard, 78°N), both of which also feature automatic closed chamber flux measurements during the snow‐free period. At Zackenberg, cold season emissions were 1 to 2 orders of magnitude lower than growing season fluxes. Perennially, CH4 fluxes resembled the same spatial pattern, which was largely attributed to differences in soil wetness controlling substrate accumulation and microbial activity. We found no significant gas sinks or sources inside the snowpack but detected a pulse in the δ13C‐CH4 stable isotopic signature of the soil's CH4 source during snowmelt, which suggests the release of a CH4 reservoir that was strongly affected by methanotrophic microorganisms. In the polygonal tundra of Adventdalen, the snowpack featured several ice layers, which suppressed the expected gas emissions to the atmosphere, and conversely lead to snowpack gas accumulations of up to 86 ppm CH4 and 3800 ppm CO2 by late winter. CH4 to CO2 ratios indicated distinctly different source characteristics in the rampart of ice‐wedge polygons compared to elsewhere on the measured transect, possibly due to geomorphological soil cracks. Collectively, these findings suggest important ties between growing season and cold season greenhouse gas emissions from high Arctic tundra.

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

“…In the recent work by Pirk et al (2016), the authors demonstrated that the fluxes of CH 4 1050 through the snowpack of permafrost Arctic wetlands during wintertime reflected a continuous emission of low amounts of gas still being produced in the soil, rather than solely the release of gas stored in the soil that was produced during the preceding growing season. These observations are in agreement with those from Mast et al (1998), where the authors reported evidence of microbial activity throughout winter in subalpine soils permitted by the insulat-1055 ing effect of the snow layer.…”

“…and control the accumulation of gas, microbial activity, diffusion rates of gases, and the amount of oxygen in the soil (Sturtevant et al, 2012;Wickland et al, 1999;Pirk et al, 2016).…”

“…In bo-100 real peat bogs of West Siberia, cold season CH 4 emissions contribute from 3.5 to 11 % of the annual CH 4 fluxes (Panikov and Dedysh, 2000). In other Arctic permafrost tundra ecosystems, however, winter CH 4 emissions were one to two orders of magnitude lower than the emissions during summer, and only accumulate in the snowpack in the presence of layers of ice blocking their exit route to the atmosphere (Pirk et al, 2016). Wickland et al (1999) ter (Blanc-Betes et al, 2016;Domine et al, 2015).…”

“…in boreal forest soils (Kim 95 et al, 2007;Wahlen and Reeburgh, 1992), boreal peat bogs in Western Siberia (Panikov and Dedysh, 2000;Smagin and Shnyrev, 2015), boreal fens (Rinne et al, 2007), and subalpine soils (Mast et al, 1998;Wickland et al, 1999). Other relevant wintertime studies from Arctic permafrost and wetland areas include the Alaskan tundra and in the Zackenberg valley in northern Greenland (Mastepanov et al, 2008;Pirk et al, 2016). In bo-100 real peat bogs of West Siberia, cold season CH 4 emissions contribute from 3.5 to 11 % of the annual CH 4 fluxes (Panikov and Dedysh, 2000).…”

“…This translates into lower CH 4 emissions to the atmosphere from November 2015 until 1010 the end of the year than during the same period in 2014. Because seasonal changes in soil wetness must be taken into account for modeling year-round gas emissions in permafrost Arctic tundra environments (Pirk et al, 2016), the JSBACH-methane version used for this …”