B027-04
Growing Season Methane Fluxes from High Arctic Tundra in Northwest Greenland
Tuesday, 8 December 2020: 17:42
Virtual
Noah Sonnenberg1, Claudia I Czimczik2, Jeffrey M Welker3, Ulrike Seibt1 and Kadmiel Maseyk4, (1)University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (2)Univ of California, Irvine, Irvine, CA, United States, (3)University of Alaska Anchorage, Department of Biological Sciences, Anchorage, AK, United States, (4)Pierre and Marie Curie University - Paris 6, Biogeochemistry and Ecology of Continental Environments, Thiverval-Grignon, France
Abstract:
Arctic tundra soils store large amounts of organic carbon that can potentially be released as methane (CH4) to the atmosphere when permafrost is thawing. On the other hand, well-drained, aerobic soils typically constitute methane sinks. Quantifying changes in methane fluxes in response to climate change is essential to improve predictions of future levels of this important greenhouse gas in the atmosphere. This is particularly urgent for arctic regions because of their accelerated speed of warming. Ecosystem fluxes of methane from high arctic tundra were measured at a multi-factorial, long-term climate change experiment near Thule, Greenland, during the growing season in 2010-2011. Methane fluxes were monitored continuously using automated whole-ecosystem chambers and a laser spectrometer in vegetated and barren soils, in both control plots and treatment plots that were warmed and/or watered. In 2010, with overall cold and wet conditions, all plots were a net sink of methane at all times. Methane uptake was strongest in mid summer (3 nmol m-2 s-1) when soil moisture was at a minimum. Net methane uptake was reduced by up to 45 nmol m-2 d-1 in the warmed treatment compared to the control plot.
In 2011, conditions were overall drier and warmer than in 2010. All plots switched between methane sink and source, but the sink activity in vegetation covered ground was more pronounced. The tundra was an overall methane sink over the growing season with maximum uptake by vegetation covered ground occurring in late July (18 nmol m-2 s-1). Treatment with heat and/or water resulted in a decrease in net uptake of methane via the vegetation covered ground. For the heat treatment there was a decrease in net daily methane uptake of up to 54 nmol m-2 d-1 when compared to the control plot, and for the combined heat and water treatment the net uptake decreased by up to 95 nmol m-2 d-1.
In contrast to the vegetation covered ground that acted as a sink for atmospheric methane, the bare soil did not appear to behave predominantly as either a source or a sink of methane. Data indicate a potential decrease in the net uptake of atmospheric methane in high arctic tundra as the region becomes warmer and precipitation increases. However, vegetation is expected to expand in the high arctic, which would increase the uptake of methane; thus the net effect will be weaker overall.
