Climate-CH<sub>4</sub> feedback from wetlands and its interaction with the climate-CO<sub>2</sub> feedback

Abstract

Abstract. The existence of a feedback between climate and methane (CH 4 ) emissions from wetlands has previously been hypothesized, but both its sign and amplitude remain unknown. Moreover, this feedback could interact with the climate-CO 2 cycle feedback, which has not yet been accounted for at the global scale. These interactions relate to (i) the effect of atmospheric CO 2 on methanogenic substrates by virtue of its fertilizing effect on plant productivity and (ii) the fact that a climate perturbation due to CO 2 (respectively CH 4 ) radiative forcing has an effect on wetland CH 4 emissions (respectively CO 2 fluxes at the surface/atmosphere interface).We present a theoretical analysis of these interactions, which makes it possible to express the magnitude of the feedback for CO 2 and CH 4 alone, the additional gain due to interactions between these two feedbacks and the effects of these feedbacks on the difference in atmospheric CH 4 and CO 2 between 2100 and pre-industrial time (respectively CH 4 and CO 2 ). These gains are expressed as functions of different sensitivity terms, which we estimate based on prior studies and from experiments performed with the global terrestrial vegetation model ORCHIDEE.Despite high uncertainties on the sensitivity of wetland CH 4 emissions to climate, we found that the absolute value of the gain of the climate-CH 4 feedback from wetlands is relatively low (<30 % of climate-CO 2 feedback gain), with either negative or positive sign within the range of estimates.Correspondence to: B. Ringeval (bruno.ringeval@lsce.ipsl.fr) Whereas the interactions between the two feedbacks have low influence on CO 2 , the CH 4 could increase by 475 to 1400 ppb based on the sign of the C-CH 4 feedback gain.Our study suggests that it is necessary to better constrain the evolution of wetland area under future climate change as well as the local coupling through methanogenesis substrate of the carbon and CH 4 cycles -in particular the magnitude of the CO 2 fertilization effect on the wetland CH 4 emissions -as these are the dominant sources of uncertainty in our model.

Species interactions and distinct microbial communities in high Arctic permafrost affected cryosols are associated with the CH4 and CO2 gas fluxes

“…Soil CH 4 flux also varies across the Arctic, ranging from wet, low centred polygonal Siberian tundra that act as a source of CH 4 over growing season (Sachs et al, 2010), to upland polar desert soils that act as CH 4 sinks (Brummell et al, 2014;Emmerton et al, 2014). Overall, due to extensive permafrost coverage, Arctic soils are modelled to become future CO 2 and CH 4 sources (Ringeval et al, 2010).…”

Methane emissions from floodplains in the Amazon Basin: challenges in developing a process-based model for global applications

“…LPJ-Bern (Wania et al, 2010;Spahni et al, 2011;Zürcher et al, 2011), DLEM (Tian et al , 2011Xu et al, 2010) and LPJ-WSL (Hodson et al, 2011) show larger CH 4 flux densities along the Amazon River than elsewhere in the basin, while SDGVM (Hopcroft et al, 2011), ORCHIDEE (Ringeval et al, 2011) and CLM4Me (Riley et al, 2011) densities at the boundary of the basin. Nevertheless, the maximum values obtained by LPX are lower than those of OR-CHIDEE and CLM4Me.…”

“…The top-down approach, also referred to as atmospheric inverse modeling, optimally combines atmospheric observations of CH 4 , a model of atmospheric chemistry and transport, and a priori information about sources and sinks (e.g., Bergamaschi et al, 2009;Bousquet et al, 2006, Monteil et al, 2011. The bottom-up approach integrates the available information about wetland CH 4 emissions at the process level into regional (Bohn et al, 2007) and global terrestrial models (e.g., Riley et al, 2011;Ringeval et al, 2011). The two approaches are complementary, in that they address different spatial scales and are constrained by observations relevant to different parts of the CH 4 budget.…”

Spatial Patterns of Iron- and Methane-Oxidizing Bacterial Communities in an Irregularly Flooded, Riparian Wetland

“…Apart from being a crucial habitat for many animals, plants, and humans, wetlands are also the largest biological source of the greenhouse gas methane (Ringeval et al, 2011). Cycling of nutrients and emission of methane from wetlands is strongly intertwined due to the oxic–anoxic conditions in close proximity (Kogel-Knabner et al, 2010; Burgin et al, 2011) which is especially distinct for iron and methane (Laanbroek, 2010).…”