Geosciences
Column: How erupting African volcanoes impact the Amazon’s
atmosphere
17
July, 2019
When
volcanoes erupt, they can release into the atmosphere a number of
different gases initially stored in their magma, such as carbon
dioxide, hydrogen sulfide, and sulfur dioxide. These kinds of gases
can have a big influence on Earth’s atmosphere, even at distances
hundreds to thousands of kilometres away.
A
team of researchers have found evidence that sulfur emissions from
volcanic eruptions in Africa can be observed as far as South America,
even creating an impact on the Amazon rainforest’s atmosphere. The
results of their study were published last year in the EGU journal
Atmospheric Chemistry and Physics.
In
September 2014, the Amazon rainforest’s atmosphere experienced an
unusually sharp spike in the concentration of sulfate aerosols.
During this period, the Amazon Tall Tower Observatory (ATTO) based in
Brazil reported levels of sulfate never recorded before in the Amazon
Basin.
Sulfate
aerosols are particles that take form naturally from sulfur dioxide
compounds in the atmosphere. When sulfate aerosols spread throughout
the atmosphere, the particles often get in the way of the sun’s
rays, reflecting the sunlight’s energy back to space. These
aerosols can also help clouds take shape. Through these processes,
the particles can create a cooling effect on Earth’s climate.
Sulfate aerosols can also facilitate chemical reactions that degrade
Earth’s ozone layer.
Fossil
fuel and biomass burning have been known cause an increase in
atmospheric sulfate, but researchers involved in the study found that
neither human activity increased the level of sulfate in the
atmosphere significantly. Instead, they examined whether a volcanic
eruption could be responsible.
Scientists
have suggested for some time that sulfur emissions in the Amazon
could come from African volcanoes, but until now they’ve lacked
proof to properly justify this idea.
However,
in this study the research team involved caught volcanic pair in the
act. By analysing satellite images and aerosol measurements, the
researchers found evidence that in 2014, emissions from the
neighboring Nyiragongo-Nyamuragira volcano complex in the Democratic
Republic of the Congo, central Africa, increased the level of sulfate
particles in the Amazon rainforest’s atmosphere.
Satellite
observations revealed that volcanoes experienced two explosive events
in September 2014, releasing sulfur emissions into the atmosphere.
During that year, the volcanic complex was reportedly subject to
frequent eruptive events, sending on average 14,400 tonnes of sulfur
dioxide into the atmosphere a day during such occasions. This amount
of gas would weigh more than London’s supertall Shard skyscraper.
Map
of SO2 plumes with VCD > 2.5 × 1014 molecules cm−2 color-coded
by date of observation. The 15-day forward trajectories started at 4
km (above mean sea level, a.m.s.l.) at four locations within the
plume detected on 13 September 2014 (light blue) are indicated by
black lines with markers at 24 h intervals. (Credit: Jorge Saturno et
al.)
Map of SO2 plumes with VCD > 2.5 × 1014 molecules cm−2 color-coded by date of observation. The 15-day forward trajectories started at 4 km (above mean sea level, a.m.s.l.) at four locations within the plume detected on 13 September 2014 (light blue) are indicated by black lines with markers at 24 h intervals. (Credit: Jorge Saturno et al.)
The
images further show that these emissions were transported across the
South Atlantic Ocean to South America. The sulfate particles created
from the emissions were then eventually picked up by an airborne
atmospheric survey campaign and the ATTO in the Amazon.
The
researchers of the study suggest that these observations indicate
that African volcanoes can have an effect on the Amazon Basin’s
atmosphere, though more research is needed to understand the full
extent of this impact.
By
Olivia Trani, EGU Communications Officer
References
and further reading
Saturno,
J., Ditas, F., Penning de Vries, M., Holanda, B. A., Pöhlker, M. L.,
Carbone, S., Walter, D., Bobrowski, N., Brito, J., Chi, X., Gutmann,
A., Hrabe de Angelis, I., Machado, L. A. T., Moran-Zuloaga, D.,
Rüdiger, J., Schneider, J., Schulz, C., Wang, Q., Wendisch, M.,
Artaxo, P., Wagner, T., Pöschl, U., Andreae, M. O. and Pöhlker,
C.: African
volcanic emissions influencing atmospheric aerosols over the Amazon
rain forest,
Atmospheric Chemistry and Physics, 18(14), 10391–10405,
doi:10.5194/acp-18-10391-2018, 2018.
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