A re-appraisal of the ENSO response to volcanism with paleoclimate data assimilation

Feng Zhu,Jonathan King,Andrew T. Wittenberg,Matthew Toohey,Gregory J. Hakim,Julien Emile-Geay,Mariano S. Morales,Kevin J. Anchukaitis

doi:10.1038/s41467-022-28210-1

Abstract

The potential for explosive volcanism to affect the El Niño-Southern Oscillation (ENSO) has been debated since the 1980s. Several observational studies, based largely on tree-ring proxies, have since found support for a positive ENSO phase in the year following large eruptions. In contrast, recent coral data from the heart of the tropical Pacific suggest no uniform ENSO response to explosive volcanism over the last millennium. Here we leverage paleoclimate data assimilation to integrate both tree-ring and coral proxies into a reconstruction of ENSO state, and re-appraise this relationship. We find only a weak statistical association between volcanism and ENSO, and identify the selection of volcanic events as a key variable to the conclusion. We discuss the difficulties of conclusively establishing a volcanic influence on ENSO by empirical means, given the myriad factors affecting the response, including the spatiotemporal details of the forcing and ENSO phase preconditioning.

Highlights

The potential for explosive volcanism to affect the El Niño-Southern Oscillation (ENSO) has been debated since the 1980s
Tree-ring based proxies, on the other hand, have been used to build long, precisely dated, and heavily replicated reconstructions that continuously span the Common Era. Their distance to ENSO centers of action means that they rely on teleconnections between the tropical Pacific and their local rainfall and temperature anomalies, leaving them vulnerable to confounding factors
Using state-of-the-art datasets and methods, combining the strengths of both coral and tree-ring records, the present evidence does not detect an effect of explosive volcanism on ENSO phase over the past millennium

Summary

Introduction

The potential for explosive volcanism to affect the El Niño-Southern Oscillation (ENSO) has been debated since the 1980s. A recent analysis of a long, monthly coral record from the heart of the tropical Pacific[26,27] suggests no uniform ENSO response to all eruptions over the last millennium, even for the largest eruptions[28] This is consistent with results from recent modeling studies using large ensembles that allow quantification of the influence of stochastic, as well as deterministic, elements[25]. Paleoclimate records offer a longer period of observation but conflicting accounts: reconstructions based mostly on tree-ring proxies[4,11–14], which experience ENSO through remote teleconnections, have been used to argue of an El Niño-like response within a year of the eruption; in contrast, reconstructions using corals from the core ENSO region27,28,30 – which provide a local, albeit discontinuous, record of ENSO variations – do not support this conclusion

Methods

Results

Conclusion