Abstract
Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean–atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO). Using nine realisations of the last millennium (LM) (850–1850 CE) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the six largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Niño and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over north-west (NW) and south-east (SE) Australia. Larger atmospheric sulfate loading during larger volcanic eruptions coincided with more persistent positive IOD and El Niño conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.
Highlights
Volcanic eruptions have significant impacts on weather and climate variability through the injection of volcanogenic material into the atmosphere
Mode specific graphs (IOD, El Niño–Southern Oscillation (ENSO), Australian precipitation) focused on the 9 years surrounding eruption
The mean of all six eruptions in each ensemble were calculated for individual years to reduce the noise associated with single eruptions, and the mean of all ensembles included in each forcing category were compared (CR, 2 × G, or “None”)
Summary
Volcanic eruptions have significant impacts on weather and climate variability through the injection of volcanogenic material into the atmosphere. The present study focuses on the under-studied relationship between large, globally significant tropical eruptions in the last millennium (850–1850 CE) and Australian precipitation. This was undertaken via the examination of the direct radiative aerosol effect and the feedbacks of two tropical modes that strongly influence Australian rainfall: the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). A statistical relationship has been demonstrated between explosive tropical volcanism and ENSO where large tropical eruptions can increase the likelihood and amplitude of an El Niño event in following years, followed by a weaker La Niña state (Adams et al, 2003). Further work by Mann et al (2005), Emile-Geay et al (2008), McGregor et al (2010), Wahl et al (2014) and Predybaylo et al (2017) supported this
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