The Global Impact Of Volcanic Eruptions

Sulfate aerosols formed in the atmosphere after a volcanic eruption can spread over both of the Earth’s hemispheres to affect climate patterns.

AsianScientist (Dec. 1, 2017) – A team of researchers in China have found evidence that high-latitude volcanic eruptions can enhance the aerosol layer in the tropical stratosphere and impact the climate of both of the Earth’s hemispheres. They published their findings in Atmospheric Chemistry and Physics.

Volcanic eruptions often seize the attention of climate scientists because the sulfate aerosols formed in the volcanic plumes may remain for months to years in the stratosphere, which is the second layer of the Earth’s atmosphere. The buildup of such aerosols could reflect the sun’s radiation back into space, and this in turn could cool the Earth’s lower atmosphere or troposphere for long periods of time.

Traditionally, scientists believe that because of atmospheric circulation patterns, eruptions in the tropics could have an effect on the climate in both hemispheres, while eruptions at mid or high latitudes have a more localized impact.

In this study, scientists at the Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO) at the Institute of Atmospheric Physics of the Chinese Academy of Sciences in China, led by Dr. Wu Xue, demonstrated that high-latitude volcano eruptions enhanced the aerosol layer in the tropical stratosphere and had an impact on the climate of both hemispheres.

Wu discovered this while working on a high-latitude volcanic eruption case together with Dr. Sabine Griessbach and Dr. Lars Hoffmann from the Jülich Supercomputing Center in Germany. They used a Lagrangian particle dispersion model, called Massive-Parallel Trajectory Calculations together with multi-source satellite observations to study the transport of the volcanic aerosol from the high-latitude volcanic eruption at Sarychev.

The researchers discovered that when the Sarychev volcano erupted in June 2009, the Asian summer monsoon anticyclonic circulation was developing. The anticyclonic circulation facilitated the transport of aerosols to the tropical tropopause region, which is the boundary in the Earth’s atmosphere between the troposphere and the stratosphere.

Then, the aerosols ascended slowly in the upward branch of the Brewer-Dobson circulation (BDC)—the primary circulation current in the stratosphere—and dispersed with the poleward branches of the BDC to both hemispheres. Hence, with the help of the Asian summer monsoon’s anticyclonic circulation, this high-latitude volcanic eruption will not only influence the climate in the northern hemisphere where the Sarychev is located, but also have an impact on the southern hemisphere.

Based on their calculations, the researchers suggest that although only about four percent of the total sulfur dioxide from the Sarychev eruption (1.2±0.2×106 tons) was transported to the tropical stratosphere, it could result in 6±1×104 tons of sulfate aerosol.

The researchers noted that if Sarychev had erupted in winter, the aerosol would be confined to the polar side of the strong subtropical jets, either getting deposited or washed out from the atmosphere in a relatively short time.

“It’s all about timing. If a high-latitude volcano erupts when the ambient atmospheric conditions are favorable for transport, it is well worth more attention,” said Wu.

The article can be found at: Wu et al. (2017) Equatorward Dispersion of a High-Latitude Volcanic Plume and Its Relation to the Asian Summer Monsoon: A Case Study of the Sarychev Eruption in 2009.


Source: Chinese Academy of Sciences; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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