Volcanic influences on the atmospheric methane budget

• Main Authors: Gauci, V., Blake, S., Stevenson, D.
• Format: Conference Object
• Language: unknown
• Published: 2003
• Subjects: Fuller; Laki; ice core
• Online Access: https://oro.open.ac.uk/33586/; http://adsabs.harvard.edu/abs/2003EAEJA.14674G

It is well known that volcanic gases can pollute the atmosphere. Certain volcanic gases can produce biogeochemical effects that lead to an indirect volcanic effect on the atmosphere. Microbially mediated emission of CH 4 from wetlands can be reduced as a result of SO 4 -- deposition by stimulating competitive exclusion of methanogens by sulfate reducing microorganisms. Hence, a large emission of volcanic SO 2 could lead to a fall in atmospheric CH 4 . We have developed a simple mathematical model to explore the effects of the Icelandic Laki eruption that occurred in 1783 and compare the results with ice-core records of late 18th century atmospheric methane. Field experiments have shown that methane emission rates are suppressed for at least 2 years after a short episode of S deposition which is likely due to reoxidation of reduced sulfur compounds back to SO 4 -- at steep redox gradients that exist within wetlands. Using Stevenson et al.'s (2003) model, we estimate a reduction in methane emission from northern wetlands of ca. 10 Tg/year (a 6 percent reduction). Our model predicts a decrease in the mean global atmospheric methane concentration of up to 5 ppbv (0.7 percent) and a c. 15 year period of lowered methane. Ice-core data (Etheridge et al., 1998) show a possible dip in atmospheric methane growth rate at the correct time, but a fuller comparison is compromised by the coarseness of the record. Our study suggests that basaltic eruptions that are at least the size and duration of Laki can induce a measurable reduction in atmospheric methane.