Halving of the northern wetland CH¡sub¿4¡/sub¿ source by a large Icelandic volcanic eruption

Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online's data policy on reuse of materials please consult the policies page. [1] Northern temperate and high-latitude wetlands are a major source of the greenhouse gas methane (CH 4). Here, we estimate the sensitivity in the strength of this source to the effects of large Icelandic volcanic eruptions such as the Laki eruption of 1783–1784. We applied spatially explicit modeled sulfate aerosol and S deposition fields from a Laki eruption simulation to a climate-sensitive model of CH 4 emissions from wetlands. We estimate that the combined influence on climate and S deposition from the Laki eruption halved the output of CH 4 from wetlands north of 30°N for the first 12 months following the eruption. The largest short-term component responsible for the CH 4 suppression is the aerosol-influenced surface cooling, although the effect of large-scale S deposition on CH 4 emissions provides a longer-term suppressive effect on emissions. Together, we estimate this combination of processes to result in an annual suppression of $20 Tg CH 4 in the year of the eruption and two subsequent years. Further, the impact of the eruption on atmospheric CH 4 concentration extends beyond the likely duration of suppressed emission. The modeled effect of this large Icelandic eruption is consistent with ice core records of atmospheric CH 4 concentrations at the time and is equivalent, in size, to the current estimated suppressive effect of industrially derived S pollution on the global wetland CH 4 source.