Release of chemical components to the atmosphere
Analyzed samples of deposits in geological layers after the event show that when the eruption happened, it also emitted enormous amounts of sulfur, chlorine and bromine to the atmosphere. Volcanic ash after the Los Chocoyos outburst is found several places in the Guatemalan highlands and in marine deposits from deep-sea cores in the Pacific, the Mexico Gulf and even in the Atlantic Ocean.
The research team had the hypothesis that such large emissions from the outburst would cause multi‐decadal consequences to the atmosphere and the global climate. But for how long? And what strength and volume would the emissions have?
To get any further on these questions the research team had to use simulation models that represent today’s knowledge of the climate system. With this approach, it allowed them to simulate the impact of a Los Chocoyos‐like eruption, and the effect of huge amounts of emissions to the atmosphere (Brenna et al 2020 ACP).
Long lasting disruption of zonal wind system
Of special interest was the effect the emission would have on the quasi‐biennial oscillation (QBO), an alternating change of every other year of zonal wind directions in the stratosphere in the tropics. The stratosphere is the second layer in the Earth’s atmosphere from approximately 15 to 50 km altitude.
– An eruption at this dimension would supply amounts of aerosols and chemistry components to the atmosphere, and according to our model simulations, the eruption would cause a ∼10 year disruption of the QBO wind, says Kirstin Krüger, author of the study.
– The change in the QBO would have started 4 months post-eruption, with abnormal easterly winds lasting ∼5 years, followed by westerlies wind, before it returned to normal QBO conditions, but with a slightly prolonged periodicity.
This disruption of the wind system is a result of heating of air caused by aerosols, and a cooling effect caused by ozone depletion after the eruption. This heating vs. cooling interact with the propagation of atmospheric waves and evolved to disrupt the QBO.
A geological event with large impact
The researchers tested out the scenario of emissions on different model ensembles, and on different volcanic forcing scenarios. The results of these supplementary studies verified the first results. They also repeated the simulations with a second model, which also backed up the robustness of the first results.
The new study in Geophysical Research Letters sheds light over what happens when such a supervolcano erupts. It would last several years, the emissions will have a peak, and it can have power to temporarily change the wind regimes in the tropical stratosphere.
Supervolcanos of today
Today it is approximately 20 supervolcanos around the world. One of the most famous is the Yellowstone Caldera in the USA. Yellowstone is known to have had two VEI 8 eruptions in the past (some 2.1 million and 640,000 years ago).