Abstract. The super-eruption of Los Chocoyos, newly dated to 80.6 kyrs ago, in Guatemala 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. Using the recently released Earth System Model CESM2(WACCM6) we simulate the impacts of the sulfur- and halogen-rich Los Chocoyos (~ 15° N) eruption on the pre-industrial Earth System for the eruption month January. Our model results show that enhanced modeled sulfate burden and aerosol optical depth (AOD) persists for five years, 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) leading to a 550 % increase in surface UV over the first five 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 (NH). Surface climate is impacted globally due to peak AOD of > 6 leading to a maximum surface cooling of > 6 K, precipitation and terrestrial net primary production (NPP) decreases of > 25 %, and sea ice area increases of 40 % in the first three years. Locally, a wetting (> 100 %) and strong increase of NPP (> 700 %) over Northern Africa is simulated in the first five years related to a southwards shift of the Inter-Tropical Convergence Zone to the southern tropics. The ocean responds with El-Niño conditions in the first two years which are masked by the strong volcanic induced surface cooling. Recovery to pre-eruption ozone levels and climate takes 15 and 30 years respectively. The long lasting surface cooling is sustained by sea ice/ocean changes in the Arctic showing an immediate sea ice area increase followed by a decrease of poleward ocean heat transport at 60° N lasting up to 20 years. In contrast, when simulating Los Chocoyos conventionally, including sulfur and neglecting halogens, we simulate larger sulfate burden and AOD, more pronounced surface climate changes and an increase of column ozone. Comparing our aerosol chemistry ESM results to other super-eruption 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 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 super eruptions 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.
Hans Brenna, Steffen Kutterolf, Michael J. Mills
Atmospheric Chemistry and Physics