EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

New insights into the ~74 ka Toba eruption from sulfur isotopes of polar ice cores

Laura Crick1, Andrea Burke1, William Hutchison1, Stephen Sparks2, Sue Mahony2, Eric W. Wolff3, Emily A. Doyle3, James W. B. Rae1, Joel Savarino4, Mika Kohno5, Sepp Kipfstuhl6, and Gerhard Wörner5
Laura Crick et al.
  • 1School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK (
  • 2School Of Earth Sciences, University Of Bristol, Bristol, UK
  • 3Department Of Earth Sciences, University Of Cambridge, Cambridge, UK
  • 4Institut des Géosciences de l'Environnement, Grenoble, France
  • 5Department of Geochemistry, GEORG-AUGUST-UNIVERSITÄT GÖTTINGEN, Göttingen, Germany
  • 6Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

The ~74ka Toba eruption in Indonesia was one of the largest volcanic events of the Quaternary and loaded an estimated 100 million tonnes of H2SO4 into the atmosphere. Understanding the precise timing of this colossal eruption is vital to unravelling the climatic and environmental impacts of the largest volcanic events on Earth. Sulfur aerosols injected into the stratosphere following large volcanic events scatter incoming radiation and lead to global cooling, and in the case of Toba it has been suggested that it led to cooling of 1 – 5°C and extinctions of some local hominin populations. One of the most enigmatic features of the Toba eruption is that the S peak has yet to be identified in the ice core records, although numerous candidate sulfate peaks have been identified in both Arctic and Antarctic ice cores. To address this, we analysed the sulfur isotope fingerprint (δ34S and Δ33S) of 11 Toba candidates from two Antarctic ice cores by multi-collector inductively coupled plasma mass spectrometry. This approach allows us to evaluate injection altitudes and to distinguish large tropical eruptions from proximal eruptions because stratospheric sulfur aerosols undergo UV photochemical reactions that impart a sulfur mass-independent isotopic fractionation (S-MIF). In contrast, tropospheric sulfur aerosols do not exhibit S-MIF because they are shielded from the relevant UV radiation by the ozone layer.

We identify three stratospheric, tropical eruption candidates with two recording the largest Δ33S signals measured to date in the ice core archives. The largest of these Δ33S signals is >2 ‰ more negative than previous measurements of the 1257 Samalas eruption (the largest eruption of the last 2000 years), despite having a similar integrated sulfate flux for this event to the ice core. These three candidates are within uncertainly of the Ar40/Ar39 age estimates for the Toba eruption and when considered with other paleoclimate proxies place the event during the transition into Greenland Stadial 20.  Finally, we further analyse the relationship between the Toba eruption candidates and these proxies to determine the precise timing and potential climatic impacts of one of the largest eruptions of the Quaternary period.

How to cite: Crick, L., Burke, A., Hutchison, W., Sparks, S., Mahony, S., Wolff, E. W., Doyle, E. A., Rae, J. W. B., Savarino, J., Kohno, M., Kipfstuhl, S., and Wörner, G.: New insights into the ~74 ka Toba eruption from sulfur isotopes of polar ice cores, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6495,, 2021.

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