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Flood Basalt Volcanic Climate Disruptions: Dynamical and Radiative Feedbacks on SO2 Emissions
  • +6
  • Scott Guzewich,
  • Luke Oman,
  • Jacob Richardson,
  • Whelley Patrick,
  • Sandra Bastelberger,
  • Kelsey Young,
  • Bleacher Jacob,
  • Ravi Kopparapu,
  • Thomas Fauchez
Scott Guzewich
NASA Goddard Space Flight Center

Corresponding Author:sguzewich@gmail.com

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Luke Oman
NASA Goddard Space Flight Center
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Jacob Richardson
University of South Florida
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Whelley Patrick
NASA Goddard Space Flight Center
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Sandra Bastelberger
ETH Swiss Federal Institute of Technology Zurich
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Kelsey Young
NASA Goddard Space Flight Center
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Bleacher Jacob
NASA Goddard Space Flight Center
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Ravi Kopparapu
NASA Goddard Space Flight Center
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Thomas Fauchez
USRA / NASA Goddard Space Flight Center
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Abstract

Volcanic flood basalt eruptions have covered 1000s of km2 with basalt deposits up to kilometers thick. The massive size and extended duration result in enormous releases of climactically-relevant gases such as SO2 and CO2. However, it is still unknown precisely how flood basalt eruptions influence climate via eruption rates and cadence, height of the volcanic plumes, and relative degassing abundance of species like SO2. Once eruptions occur, the complex interplay of photochemistry, greenhouse gas warming, changes to the atmospheric circulation, and aerosol-cloud interactions can only be properly simulated with a comprehensive global climate model (GCM). We created an eruption scenario for the Goddard Chemistry Climate Model (GEOSCCM) that emits SO2 in the near-surface atmosphere constantly and four times per year an explosive eruption that emits much more SO2 in the upper troposphere/lower stratosphere. The eruption lasts for 4 years and emits 30 Gt of SO2 total. This corresponds to ~1/10th of what may have been emitted during the Wapshilla Ridge eruption phase of the Columbia River flood basalt eruption 15-17 Ma. We use a pre-industrial atmosphere and otherwise modern initial and boundary conditions. The massive flux of SO2 into the atmosphere is quickly converted to H2SO4 aerosols. Global area-weighted mean visible band sulfate aerosol optical depth reaches 220 near the end of the eruption, comparable to cumulonimbus clouds. This reduces the surface shortwave radiative flux by 85% and top-of-atmosphere outgoing longwave flux by 70%. Contrary to our expectations, we find that the climate warms during and immediately following the eruption after a very brief initial cooling. Global mean surface temperature peaks 3-4 years after the eruption ends with a +6 K anomaly relative to a baseline simulation without the eruption. Post-eruption regional temperatures, particularly near-equatorial continental areas, see drastic rises of summertime temperatures with monthly mean temperatures equaling or exceeding 40°C. These temperature responses are radiative- and circulation-driven. The eruption warms and raises the tropical tropopause, allowing a massive flux of water vapor into the stratosphere. Stratospheric water vapor, usually ~3 parts per million reaches 1-2 parts per thousand.