Abstract
Abstract. The supereruption of Los Chocoyos (14.6∘ N, 91.2∘ W) in Guatemala ∼84 kyr ago was one of the largest volcanic events of the past 100 000 years. Recent petrologic data show that the eruption released very large amounts of climate-relevant sulfur and ozone-destroying chlorine and bromine gases (523±94 Mt sulfur, 1200±156 Mt chlorine, and 2±0.46 Mt bromine). Using the Earth system model (ESM) of the Community Earth System Model version 2 (CESM2) coupled with the Whole Atmosphere Community Climate Model version 6 (WACCM6), we simulated the impacts of the sulfur- and halogen-rich Los Chocoyos eruption on the preindustrial Earth system. Our simulations show that elevated sulfate burden and aerosol optical depth (AOD) persists for 5 years in the model, while the volcanic halogens stay elevated for nearly 15 years. As a consequence, the eruption leads to a collapse of the ozone layer with global mean column ozone values dropping to 50 DU (80 % decrease) and leading to a 550 % increase in surface UV over the first 5 years, with potential impacts on the biosphere. The volcanic eruption shows an asymmetric-hemispheric response with enhanced aerosol, ozone, UV, and climate signals over the Northern Hemisphere. Surface climate is impacted globally due to peak AOD of >6, which leads to a maximum surface cooling of >6 K, precipitation and terrestrial net primary production decrease of >25 %, and sea ice area increases of 40 % in the first 3 years. Locally, a wetting (>100 %) and strong increase in net primary production (NPP) (>700 %) over northern Africa is simulated in the first 5 years and related to a southward shift of the Intertropical Convergence Zone (ITCZ) to the southern tropics. The ocean responds with pronounced El Niño conditions in the first 3 years that shift to the southern tropics and are coherent with the ITCZ change. Recovery to pre-eruption ozone levels and climate takes 15 years and 30 years, respectively. The long-lasting surface cooling is sustained by an immediate increase in the Arctic sea ice area, followed by a decrease in poleward ocean heat transport at 60∘ N which lasts up to 20 years. In contrast, when simulating Los Chocoyos conventionally by including sulfur and neglecting halogens, we simulate a larger sulfate burden and AOD, more pronounced surface climate changes, and an increase in column ozone. By comparing our aerosol chemistry ESM results to other supereruption simulations with aerosol climate models, we find a higher surface climate impact per injected sulfur amount than previous studies for our different sets of model experiments, since the CESM2(WACCM6) creates smaller aerosols with a longer lifetime, partly due to the interactive aerosol chemistry. As the model uncertainties for the climate response to supereruptions are very large, observational evidence from paleo archives and a coordinated model intercomparison would help to improve our understanding of the climate and environment response.
Highlights
The Los Chocoyos (LCY, 14.6◦ N, 91.2◦ W) supereruption (Kutterolf et al, 2016) of M = 8, dated to ∼ 84 kyr before the present (Rose et al, 1999), is known to be one of the largest volcanic eruptions of the past 100 000 years (Drexler et al, 1980)
The model results may have been similar for LCY 84 000 years ago, as we did not set up the simulations with observed initial conditions and there are uncertainties in the volcanic emissions
We evaluate our model results to show a lower estimate of the possible climate and environment response given the likely low estimates for our petrologically derived volcanic emissions
Summary
The sulfur gases emitted by volcanoes have a strong direct climate impact through the formation of sulfuric acid aerosols, which block incoming sunlight and cool the surface (Robock, 2000) Halogen compounds, such as chlorine and bromine, contribute to catalytic ozone depletion in the stratosphere (Brasseur and Solomon, 2005; Solomon, 1999). Recent atmospheric observations revealed that even relatively small volcanic eruptions can inject significant amounts of halogen compounds in the stratosphere (for review and overview discussions, see von Glasow et al, 2009; Krüger et al, 2015; WMO, 2018) This means that a sulfur- and halogen-rich eruption is expected to cool the Earth’s surface and potentially damage the stratospheric ozone layer, with further impacts on the surface environment through the change in the atmosphere’s transparency to harmful ultraviolet (UV), shortwave UVB, radiation (i.e., Brenna et al, 2019). No direct iodine erupted mass measurements are available for the LCY eruption
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