OS015-0014
Volcano-induced ENSO occurrences: an integrated assessment using targeted paleoclimate data assimilation experiments.

Wednesday, 9 December 2020
Poster
Julien Emile-Geay, University of Southern California, Los Angeles, CA, United States, Feng Zhu, University of Southern California, Department of Earth Sciences, Los Angeles, CA, United States, Kevin J Anchukaitis, University of Arizona, School of Geography, Development and Environment, Tucson, AZ, United States, Gregory J. Hakim, University of Washington, Department of Atmospheric Sciences, Seattle, WA, United States and Jonathan King, University of Arizona, Department of Geosciences, Tucson, AZ, United States
Abstract:
There is ongoing controversy as to the role of explosive volcanism in shaping ENSO behavior, with implications for our understanding of ENSO fundamentals and the safety of geoengineering scenarios. The prevailing view is that sulfate aerosol loading above a certain threshold can shift the odds in favor of a warm ENSO phase the year following an eruption. This view is borne out by models spanning a range of complexity, though there is no consensus on the underlying mechanism [e.g. Emile-Geay et al, 2008, McGregor and Timmerman 2010, Stevenson et al, 2016, Khodri et al, 2017, Pausata et al, 2020]. The relationship also seems borne out by reconstructions of ENSO state [McGregor et al, 2020], which are largely based on extratropical, moisture-sensitive tree-ring chronologies. In contrast, a new, precisely dated coral record from the heart of the tropical Pacific suggests no consistent ENSO response to volcanic forcing over the last millennium [Dee et al, 2020].

Here we use a flexible data assimilation framework [Hakim et al, 2016, Tardif et al, 2019, Zhu et al, 2019] to explore the role of proxy type and location on the analysis of the volcano-ENSO relationship. The reconstructions show a large sensitivity to all aspects investigated. In the best-validated reconstruction, a significant response to volcanism only appears for 3 out 8 eruptions considered, all with a relatively low sulfate loading. We conclude that present evidence does not support the prevailing view, and discuss the underlying reasons for this, as well as recommendations for making further progress on this pressing question.



References

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  • Zhu, F., et al. (2019), doi:10.5281/zenodo.3167723.
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