4:15 PM - 4:30 PM
[ACC26-09] Long-term variations of hydrogen peroxide in Greenland ice cores over the past 200 years
Atmospheric oxidants including ozone (O3), hydroxyl radicals (OH), and hydrogen peroxide (H2O2) play essential roles in atmospheric chemistry through removal of greenhouse gases such as methane (CH4) as well as formation of aerosols. H2O2 is the only oxidant that can be preserved in ice cores and thus is expected to provide a constraint on the past oxidant chemistry. However, it has been pointed out that H2O2 records in ice cores may be altered by post-depositional loss, although H2O2 is more likely to be preserved at sites with greater snow accumulation [Frey et al., 2006]. In this study, we analyzed H2O2 records over the past 200 years based on the SE-Dome II (67.19°N, 36.47°W, 3160.7 m above sea level) ice core, where the snow accumulation rate is specifically high (> 1 m/year) within Greenland (Iizuka et al., 2021).
H2O2 in the SE-Dome II ice core ranged from 26.7 ppb to 143.1 ppb with a long-term trend characterized by increase from 1800s to 1860s, decrease until 1900s, and again increase from 1970s. The comparison of annual H2O2 concentration with the seasonal accumulation rate reconstructed for the SE-Dome II ice core showed no significant correlation (r < 0.1), suggesting that seasonality in snow accumulation rate is not a determining factor in preserved H2O2. This result supports the hypothesis that H2O2 in the SE-Dome II ice core reflects atmospheric H2O2 variation. Our results were compared with H2O2 records in other Greenland ice cores from Dye2 [McConnell et al., 2013], Dye3 [Sigg and Neftel., 1991], Summit [Sigg and Neftel., 1991; McConnell et al., 2013], and Tunu [McConnell et al., 2016], which showed generally consistent long-term variations in H2O2. Principal component analysis using the H2O2 data from all sites yielded the PC1 responsible for 35% variance, which was also generally consistent with the trend observed in the SE-Dome II ice core. This suggests that the trend in the PC1 is common over Greenland and reflects variations of atmospheric H2O2. The decrease in H2O2 from 1860s to 1970s found in the PC1 coincides with the increases of black carbon (BC) and sulfate aerosols (SO42-) recorded in Greenland ice cores, which is attributed to combustion of fossil fuels [McConnell et al., 2007]. This co-variation implies that H2O2 decreases in Greenland ice cores reflect the reduction of H2O2 production due to the accelerated uptake of precursor HO2 by aerosols, of which importance for oxidant chemistry have been recognized in the recent studies [Mao et al.,2013; Ke Li et al., 2019].
H2O2 in the SE-Dome II ice core ranged from 26.7 ppb to 143.1 ppb with a long-term trend characterized by increase from 1800s to 1860s, decrease until 1900s, and again increase from 1970s. The comparison of annual H2O2 concentration with the seasonal accumulation rate reconstructed for the SE-Dome II ice core showed no significant correlation (r < 0.1), suggesting that seasonality in snow accumulation rate is not a determining factor in preserved H2O2. This result supports the hypothesis that H2O2 in the SE-Dome II ice core reflects atmospheric H2O2 variation. Our results were compared with H2O2 records in other Greenland ice cores from Dye2 [McConnell et al., 2013], Dye3 [Sigg and Neftel., 1991], Summit [Sigg and Neftel., 1991; McConnell et al., 2013], and Tunu [McConnell et al., 2016], which showed generally consistent long-term variations in H2O2. Principal component analysis using the H2O2 data from all sites yielded the PC1 responsible for 35% variance, which was also generally consistent with the trend observed in the SE-Dome II ice core. This suggests that the trend in the PC1 is common over Greenland and reflects variations of atmospheric H2O2. The decrease in H2O2 from 1860s to 1970s found in the PC1 coincides with the increases of black carbon (BC) and sulfate aerosols (SO42-) recorded in Greenland ice cores, which is attributed to combustion of fossil fuels [McConnell et al., 2007]. This co-variation implies that H2O2 decreases in Greenland ice cores reflect the reduction of H2O2 production due to the accelerated uptake of precursor HO2 by aerosols, of which importance for oxidant chemistry have been recognized in the recent studies [Mao et al.,2013; Ke Li et al., 2019].