Frequency of large volcanic eruptions over the past 200 000 years

Abstract

Abstract. Volcanic eruptions are the dominant cause of natural variability in climate forcing on timescales up to multidecadal. Large volcanic eruptions lead to global-scale climate effects and influence the carbon cycle on long timescales. However, estimating the frequency of eruptions is challenging. Here we assess the frequency at which eruptions with particular deposition fluxes are observed in the EPICA Dome C ice core over the last 200 kyr. Using S isotope analysis we confirm that most of the largest peaks recorded at Dome C are from stratospheric eruptions. The cumulative frequency through 200 kyr is close to linear, suggesting an approximately constant rate of eruptions. There is no evidence for an increase in the rate of events recorded in Antarctica at either of the last two deglaciations. Millennial variability is at the level expected from recording small numbers of eruptions, while multimillennial variability may be partly due to changes in transport efficiency through the Brewer–Dobson circulation. Our record of events with sulfate deposition rates > 20 and >50 mg m−2 contains 678 and 75 eruptions, respectively, over the last 200 kyr. Calibration with data on historic eruptions and analysis of a global Quaternary dataset of terrestrial eruptions indicates that sulfate peaks with deposition rates > 20 and >50 mg m−2 correspond to explosive eruptions of magnitude ≥ 6.5 and ≥7, respectively. The largest recorded eruption deposited just over 300 mg m−2.

Los Chocoyos supereruption did not trigger millennial scale cooling

“…Previous work confirms the stratospheric and likely tropical origin of this eruption deposit, which is the second largest of the last 100 ka in the EDC core, by the presence of one of the largest mass independent fractionation sulfur isotope signatures on record from a volcanic aerosol ice core deposit (Δ 33 S = +2.99 ± 0.14 ‰ (2 SD) 26 ). In this case, the large positive Δ 33 S rules out a contribution of proximal, tropospheric sulfate which would result in a muted or 0 ‰ Δ 33 S value in the ice core 27,28 .…”

“…Having identified the LCY sulfate peak in both Greenland and Antarctica, we use new and existing continuous sulfate (and sulfur) concentration data across the volcanic peak to estimate the total sulfate deposition in each ice core following established methods (see methods) 26,41,42 . In addition to NEEM, NGRIP and EDC, further high-resolution sulfate data from corresponding LCY candidate peaks identified in Greenland ice core GISP2 and Antarctic ice core EDML are used to improve our estimation of sulfur deposition at both poles.…”

New estimates of sulfate diffusion rates in the EPICA Dome C ice core

“…Volcanic sulfate peaks are many times greater in magnitude than the sulfate background, which is dominated by marine sources. Furthermore, these easily identifiable signals occur regularly through time (Wolff et al, 2023), meaning evolution of their form resulting from diffusion and ice thinning can be traced down-core. In this study, we use EDC sulfate data measured using fast ion chromatography (FIC) (Severi et al, 2015;Fudge et al, 2023).…”

“…The long-term background signal was removed from the sulfate data by subtracting a 200 yr moving median. Following Wolff et al (2023), we multiply the residual sulfate concentrations between 0 and 358.6 m by (1/0.7) to account for a calibration discrepancy identified between FIC and standard ion chromatography measurements on EDC ice. Note that although this adjustment will impact our quantification of peak height and peak area in this depth interval, there is no impact on the estimation of diffusion rate.…”

“…Each of these peaks are bordered by regions of relative sulfate depletion, hence the hypothesis that sulfate has moved, even been "sucked", into the peak horizon (see Fig. 3 of Wolff et al (2023)). Although Traversi et al (2009) found these peaks first appeared beyond 2800 m depth (~450 ka), we found some similar peaks during our analysis of shallower/younger ice.…”