Volcanoes and ENSO: a re-appraisal with the Last Millennium Reanalysis

Abstract

The potential for explosive volcanism to affect the state of the El Niño-Southern Oscillation (ENSO) has been debated since the1980s. Several observational studies, largely based on tree rings, have since found support for a positive ENSO phase in the year following large eruptions. Models of different complexities also simulate such a response, detectable above the backdrop of internal variability – though they disagree on the underlying mechanisms. In contrast, recent coral data from the heart of the tropical Pacific suggest no uniform ENSO response to all eruptions over the last millennium. Here we leverage paleoclimate data assimilation to integrate the latest paleoclimate evidence into a consistent dynamical framework and re-appraise this relationship. Our analysis finds only a weak statistical association between volcanism and ENSO, suggestive of either no causal association, or of an insufficient number of large volcanic events over the past millennium to obtain reliable statistics. While currently available observations do not support the model-based inference that tropical eruptions promote an ENSO response, there are hints of a response to hemispherically asymmetric forcing, consistent with the "ITCZ shift" mechanism. We discuss the difficulties of conclusively establishing a volcanic influence on ENSO given the many degrees of freedom affecting the response, including eruption season, spatial characteristics of the forcing, and ENSO phase preconditioning.

ENSO and NAO Linkage to Strong Volcanism and Associated Post‐Volcanic High‐Latitude Winter Warming

“…The possible dynamical mechanisms that allow volcanic forcing to modulate ENSO (e.g., dynamical thermostat, subtropical wind stress curl, and land temperature contrasts, etc.) can be found in earlier studies (Dogar, Hermanson, et al, 2023;McGregor et al, 2020;Ohba et al, 2013;Predybaylo et al, 2017Predybaylo et al, , 2020Zhu et al, 2021).…”

“…The El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) are large‐scale climate variability patterns with profound global and regional climatic impacts (Dogar & Almazroui, 2022; Dogar & Sato, 2018; Dogar, Kucharski, & Azharuddin, 2017; Dogar, Stenchikov, et al., 2017; Dogar et al., 2019; Hurrel, 1995; Ineson & Scaife, 2009; Zhang et al., 2019; Zhu et al., 2021). Both these climate patterns are strongly influenced by volcanic forcing (e.g., Dogar et al., 2022; Dogar & Shahid, 2022; Dogar, Hermanson, et al., 2023; McGregor et al., 2020; Robock, 2000).…”

ENSO and NAO Linkage to Strong Volcanism and Associated Post-Volcanic High-latitude Winter Warming

“…The possible dynamical mechanisms that allow volcanic forcing to modulate ENSO (e.g., dynamical thermostat, subtropical wind stress curl, and land temperature contrasts, etc.) can be found in earlier studies (McGregor et al 2020, Zhu et al, 2021and Dogar et al, 2023.…”