Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores

Abstract

The record of volcanic forcing of climate over the past 2500 years is based primarily on sulfate concentrations in ice cores. Of particular interest are large volcanic eruptions with plumes that reached high altitudes in the stratosphere, as these afford sulfate aerosols the longest residence time in the atmosphere, and thus have the greatest impact on radiative forcing. Sulfur isotopes measured in ice cores can be used to identify these large eruptions because stratospheric sulfur is exposed to UV radiation, which imparts a time-evolving mass independent fractionation (MIF) that is preserved in the ice. However sample size requirements of traditional measurement techniques mean that the MIF signal may be obscured, leading to an inconclusive result. Here we present a new method of measuring sulfur isotopes in ice cores by multi-collector inductively

Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

“…First, further refinement and confirmation of our bipolar synchronization is called for. Analysis of sulfur massindependent isotopic fractionation (Burke et al, 2019) is needed for the proposed bipolar volcanic events. For low-latitude eruptions to show up in both the Arctic and Antarctic almost certainly requires injection of materials into the stratosphere, which is reflected in  33 S. High-resolution records of 10 Be can further refine bipolar matching (Adolphi et al, 2018) in critical intervals where the volcanic record is ambiguous.…”

“…The nearest pair of bipolar eruptions is found at 25.76 and 25.94 ka, respectively, leaving enough room in the layer counting uncertainty for the Greenland acidity spike to potentially be a 'false match' offset by up to 30 years from the Antarctic Oruanui spike. The link needs to be investigated by the bipolar sulfur isotopes method to rule out a coeval local source for the NGRIP event (Burke et al, 2019). Besides the potential bipolar link, the Oruanui eruption is also relevant for comparing Greenland and Antarctic ice core time scales (Sigl et al, 2016) and it constitutes an important comparison point for 14 C ages and ice core chronologies (Muscheler et al, In review, February 2020).…”

“…For the earlier part of the Holocene, which has been less intensely studied, some 75 bipolar events have been found (Veres et al, 2013), and from around the time of the Indonesian Toba eruption occurring in Sumatra some 74 ka ago, a handful of bipolar volcanic events have been identified (Svensson et al, 2013). Recently, there has been progress in identifying stratospheric volcanic peaks in ice cores based on their sulfur isotopic fingerprints (Burke et al, 2019;Gautier et al, 2019). In this work, we expand the bipolar volcanic matching approach systematically throughout the 12-60 ka time interval.…”

Large mass-independent sulphur isotope anomalies link stratospheric volcanism to the Late Ordovician mass extinction

“…Sulphur photochemistry is one of the few processes that produces massindependent fractionation, yielding non-zero Δ 33 S values 16,29,30 . As such, S-isotopes have been successfully used in polar snow and ice cores to distinguish between stratospheric and tropospheric volcanic eruptions [16][17][18][19][20] . In the stratosphere, at or above the ozone layer, the sulphur ejected from volcanic emissions will be exposed to UV radiation, acquiring a S-MIF signal with non-zero Δ 33 S value [16][17][18][19][20]29,30 .…”

“…However, the Hg enrichments in the sedimentary rocks of the Ordovician-Silurian boundary from South China have been argued to be sulphide-hosted rather than of volcanic origin, challenging the hypothesis of a volcanic driver for the LOME 15 . Here, we report sulphur isotope data (δ 34 S, Δ 33 S and Δ 36 S) of pyrite from two sedimentary successions from South China, and we use a characteristic signal of large Δ 33 S anomalies, resulting from stratospheric photochemical reactions [16][17][18][19][20] to constrain the nature of volcanic eruptions during the Late Ordovician. Our results provide new evidence of linking stratospheric volcanic eruptions and environmental deterioration to the LOME.…”