Growing season methyl bromide and methyl chloride fluxes at a sub-arctic wetland in Sweden

[1] Methyl bromide and methyl chloride fluxes were measured at several sites in a sub-arctic wetland near Abisko, Sweden (68°28′N 18°49′E) throughout the 2008 growing season. Averaged over 92 flux measurements the sub-arctic wetland was found to be a small net sink for CH3Br, with mean (±1 sd) uptake of −25 (±20) ng m−2 h−1, but a small net source of CH3Cl with mean emissions of 400 (±1600) ng m−2 h−1. Seasonal trends were observed in both CH3Br and CH3Cl net fluxes, but diurnal trends for CH3Cl only, with peak emissions observed during the afternoon. CH3Cl fluxes differed significantly with hydrological status of measurement locations; however, no other substantial correlations were observed between fluxes and external parameters (air and soil temperature and PAR). This study shows that the single previous estimated sink flux for CH3Cl in tundra globally (derived from measurements in Alaska) requires revision, although not that for CH3Br.