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Why do wet and dry eruptions affect climate differently?

Mark Jellinek, Luke Brown

  • Affiliations: Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada

  • Presentation type: Talk

  • Presentation time: Monday 09:00 - 09:15, Room R290

  • Programme No: 6.1.3

  • Theme 6 > Session 1

Abstract

The two most explosive eruptions of the satellite era resulted in dramatically different effects on Earth's climate.Whereas the subaerial 1991 Mt Pinatubo event was marked by intense stratospheric warming and corresponding surface cooling, the submarine 2022 Hunga Tonga Ha'apai event imparted virtually no significant climate change signal. We explore a hypothesis that key underlying controls are the differing efficiencies of sulfur scavenging by solid ash particles and cloud droplets condensed within eruption columns. Using an updated open-source HYDROVOLC (Rowell et al., 2022) plume model that parametrizes cloud droplet formation and sulfur uptake onto ash and into droplets, we constrain the relative activities of scavenging mechanisms within subaerial and subaqueous explosive eruptions of comparable intensity.  We find that subaerial eruptions deliver more stratospheric SO\(_2\) because plume humidity is limited by the availability of atmospheric moisture. By contrast, entrained \(text{H}_2text{O}^{(v)}\) within subaqueous volcanic jets sustain plume supersaturation, increasing the number and size of entrained droplets that absorb SO\(_2\).  We compare our model results to eruptions of observed sulfur injection in the satellite era to find that scavenging microphysics provides a theoretical basis for understanding aspects of the variability of volcanic effects on climate.  Our results provide a lookup table for climate models by extending the link between stratospheric sulfur injection and eruptive source conditions to include the effects of volcanic particles as sulfur sinks.In a companion study, we investigate the effects of source water salinity on ash hygroscopicity to distinguish scavenging regimes between freshwater and seawater eruptions.