Mastepanov et al. 2008

Mastepanov M, Sigsgaard C, Dlugokencky EJ, Houweling S, Strom L, Tamstorf MP, Christensen TR. 2008. Large tundra methane burst during onset of freezing. Nature 456: 628-631.

These authors describe a large emission of methane from a wet tundra site in the Greenland High Arctic, which occurred in late autumn and early winter as the ground froze. This burst of methane emission is of a similar magnitude to the total methane emission from this site during the growing season, and accounts for the previously observed “shoulder” of methane in autumn at high altitudes.

The site is Zackenberg Valley, in the north-east of Greenland at about 74ºN latitude. This site appears to be broadly similar to other High Arctic tundra meadows such as Truelove Lowlands (Devon Island) and Alexandra Fjord (Ellesmere Island) and large parts of northern Russia, with an active layer 20 to 100 cm thick. The growing season measurements here were similar to previous years, and similar to another study in Siberia.

These measurements were made using an automated methane-only laser-based system, that took readings of methane flux every hour, with a data-gathering time of 1 second. Late-season pulses of methane were not observed at lower-latitude sites, possibly because a deeper permafrost “floor” allows methane to diffuse down to deeper soil layers rather than being forced upwards. Spatial and temporal variablity of the freezing methane emissions were very high, suggesting the diffusion paths of methane squeezed out of the soil were dependent upon plant root systems and similar structures.

This paper is the reason my field season at Alexandra Fjord in 2009 may extend as late as August 25 (planned) or September 10 (worst-case scenario). The figures in this paper imply the difference between measured and modeled methane emissions became apparent approximately in late August.