Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review

Abstract

[1] We have reviewed the available scientific literature on how natural sources and the atmospheric fate of methane may be affected by future climate change. We discuss how processes governing methane wetland emissions, permafrost thawing, and destabilization of marine hydrates may affect the climate system. It is likely that methane wetland emissions will increase over the next century. Uncertainties arise from the temperature dependence of emissions and changes in the geographical distribution of wetland areas. Another major concern is the possible degradation or thaw of terrestrial permafrost due to climate change. The amount of carbon stored in permafrost, the rate at which it will thaw, and the ratio of methane to carbon dioxide emissions upon decomposition form the main uncertainties. Large amounts of methane are also stored in marine hydrates, and they could be responsible for large emissions in the future. The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean. Uncertainties are dominated by the sizes and locations of the methane hydrate inventories, the time scales associated with heat penetration in the ocean and sediments, and the fate of methane released in the seawater. Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out. We also identify gaps in our scientific knowledge and make recommendations for future research and development in the context of Earth system modeling.

Estimating wetland methane emissions from the northern high latitudes from 1990 to 2009 using artificial neural networks

“…According to the latest Intergovernmental Panel on Climate Change report, the radiative efficiency of CH 4 is about 25 times that of CO 2 on a 100 year time horizon [Solomon et al, 2007]. The atmospheric concentration of CH 4 has increased from a preindustrial value of about 700 ppb to a current value of about 1790 ppb [Dlugokencky et al, 2009], contributing 0.48 W m À2 [O'Connor et al, 2010] of radiative forcing to the atmosphere. Global CH 4 budget can be relatively well determined based on observations of atmospheric concentration of CH 4 .…”

Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012

“…Emission rates by this process are dependent on soil moisture, temperature and the availability of organic matter (Pelletier et al, 2007;Strom and Christensen, 2007). Much of this CH 4 does not reach the atmosphere due to consumption that occurs in oxic soil regions by methanotrophic bacteria (O'Connor et al, 2010;Parmentier et al, 2011). As a result of these competing environment-dependant factors, emissions show a large degree of spatial and temporal variability (Zhuang et al, 2006;Pickett-Heaps et al, 2011).…”

Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapor concentration field measurements

“…A highly topical example comes from environmental science: as the permafrost in arctic regions is gradually thawing, gases that affect the climate effect, such as methane, carbon dioxide or water vapor, are emitted from the soil (Anisimov and Nelson, 1997;Nakano et al, 2000;O'Connor et al, 2010;Schuur, 2009;Vonk et al, 2012;Zimov et al, 2006). This process is suspected to lead to a positive feedback on the greenhouse effect, which would increase the soil emissions even further (Field et al, 2007;Heimann and Reichstein, 2008;Luke and Cox, 2011;Olefeldt et al, 2013;Schuur, 2009).…”

“…This process is suspected to lead to a positive feedback on the greenhouse effect, which would increase the soil emissions even further (Field et al, 2007;Heimann and Reichstein, 2008;Luke and Cox, 2011;Olefeldt et al, 2013;Schuur, 2009). Although it is already known that such gases are released, there is, as of yet, little information on their absolute concentrations (O'Connor et al, 2010;Schuur, 2009;Schuur and Abbott, 2011;Vonk et al, 2012).…”