El Niño events, the main warming events in the tropical Pacific Ocean that occur every two to seven years, have significant environmental and social impacts in North and South America and other parts of the world. Previous research has shown that volcanic eruptions affect El Niño-Southern Oscillation cycles, but the mechanisms of that connection have not been clear. A new study published in Scientific advances Co-author of the University of Hawai’i at Mānoa, atmospheric scientist Christina Karamperidou suggests a new explanation of how this response might occur.
Volcanoes inject large amounts of small particles, aerosols, into the atmosphere. These particles act as a mirror in the sky, reflecting sunlight back into space and causing a cooldown that lasts between one and two years, linking volcanic eruptions to the climate system.
In a computer simulation, the researchers tested the effects of a volcanic eruption that occurs in the tropics but far from the equator, in either the northern or southern hemisphere. The simulated eruption was the size of the 1815 event at Mount Tambora, when a volcanic mountain on the north coast of Sumbawa Island, Indonesia, exploded in the largest volcanic eruption in recorded history.
Conventional theories have focused on the local equatorial effects of volcanic cooling. Contrary to this, the recent study found that the cooling occurred mainly in the region outside the tropics. This distant cooling leads to a change in winds along the equator that favors the onset of El Niño conditions when the eruption occurs in the tropics and north of the equator and La Niña conditions when the eruption occurs south of the Ecuador.
“We show in this study that whether explosive volcanic eruptions lead to El Niño or La Niña conditions depends not only on the hemisphere of the eruption and the tropical Pacific state at the time of the eruption, but also on the large-scale climate conditions outside of the tropics, “said Karamperidou, an assistant professor at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).
“In fact, in a previous study, we showed that high-latitude volcanic eruptions in the northern hemisphere, for example in Iceland, can also cause El Niño conditions in the tropics,” he said. “Both studies highlight the role of the extratropical atmosphere in influencing the development of El Niño events and, ultimately, help us better predict their behavior and impacts in response not only to volcanic eruptions, but also to others. aerosol emissions inside and outside the tropical zone. “
Understanding this process provides information on the response to human-made emissions, such as COtwo and sprays. In this way, volcanoes are natural experiments that can help scientists better understand climate change caused by human activities.
The study, published in Scientific advances, was chaired by Francesco SR Pausata, previously with the Bolin Center for Climate Research and now at the University of Quebec in Montreal.
Volcanic eruptions reduce global rainfall
Francesco SR Pausata et al. The change in ITCZ and extratropical teleconnections drive ENSO’s response to volcanic eruptions, Scientific advances (2020). DOI: 10.1126 / sciadv.aaz5006
Francesco SR Pausata et al. ENSO response to high latitude volcanic eruptions in the northern hemisphere: the role of initial conditions, Geophysical research charts (2016) DOI: 10.1002 / 2016GL069575
Provided by the University of Hawaii at Manoa
Citation: Research reveals how volcanic eruptions affect El Niño (2020, June 23) retrieved June 24, 2020 from https://phys.org/news/2020-06-reveals-volcanic-eruptions-affect-el .html
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