Monitoring an 'anti-greenhouse' gas: Dimethyl sulfide in Arctic air


Date:
January 30, 2023
Source:
Hokkaido University
Summary:
Data stored in ice cores dating back 55 years bring new insight
into atmospheric levels of a molecule that can significantly affect
weather and climate.


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FULL STORY ==========================================================================
Data stored in ice cores dating back 55 years bring new insight into atmospheric levels of a molecule that can significantly affect weather
and climate.


========================================================================== Dimethyl sulfide (C2H6S) is a small molecule released by phytoplankton in
the ocean, which can play a big role in regulating the Earth's climate. It encourages cloud formation above the sea, and is often called an 'anti- greenhouse gas', since clouds block radiation from the sun and lower
sea surface temperatures. At least some blocked heat will be retained
in the atmosphere, however, so the effects can be complex. Researchers
at Hokkaido University have charted evidence for increasing dimethyl
sulfide emissions linked to the retreat of sea ice from Greenland as the
planet warms. They report their findings in the journal Communications
Earth & Environment.

Modelling studies have long suggested that the decline in Arctic sea
ice could lead to increased dimethyl sulfide emission, but direct
evidence for this has been lacking. Assistant Professor Sumito Matoba
and colleagues have inferred dimethyl sulfide levels over 55 years by quantifying the related compound, methane sulfonic acid (MSA), in ice
core samples from the south-east Greenland ice sheet. MSA is directly
produced from dimethyl sulfide, serving as a stable record of dimethyl
sulfide levels. This process is part of a variety of chemical interactions among aerosols in the atmosphere.

The team, including researchers from Nagoya University and Japan's
Aerospace Exploration Agency, reconstructed the annual and seasonal MSA
flux from 1960 to 2014, at a monthly resolution. The annual MSA levels decreased from 1960 to 2001, but then markedly increased after 2002.

"We found that July to September MSA fluxes were three to six times higher between 2002 and 2014 than between 1972 and 2001," says Matoba. "We
attribute this to the earlier retreat of sea ice in recent years."
Supporting evidence comes from satellite data that has monitored the
levels of the crucial sunlight-absorbing green pigment chlorophyll-a
in the surrounding seas. The chlorophyll-a serves as an indicator of phytoplankton abundance, which in turn should correlate well with the
amount of dimethyl sulfide released by the phytoplankton.

Arctic temperatures are rising twice as fast as the global average,
and the summer seasonal sea ice extent has declined sharply in recent
decades. This increases the amount of light striking the ocean and
promotes the growth of phytoplankton.

While the latest results from the Hokkaido team add important confirmation
of the changing dimethyl sulfide levels, Matoba emphasises that long-term
and continuous monitoring of aerosols is needed. "This will be essential
to follow the current impact, and predict future impacts, of dimethyl
sulfide emissions on the global climate," he says.

* RELATED_TOPICS
o Earth_&_Climate
# Global_Warming # Climate # Oceanography # Ice_Ages
o Fossils_&_Ruins
# Early_Climate # Origin_of_Life # Fossils # Ancient_DNA
* RELATED_TERMS
o Ice_core o Weather o Greenland_ice_sheet o Climate_model
o Global_climate_model o Climate o Radiocarbon_dating o
Weather_forecasting

========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Yutaka Kurosaki, Sumito Matoba, Yoshinori Iizuka, Koji Fujita, Rigen
Shimada. Increased oceanic dimethyl sulfide emissions in areas of
sea ice retreat inferred from a Greenland ice core. Communications
Earth & Environment, 2022; 3 (1) DOI: 10.1038/s43247-022-00661-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/01/230130213938.htm

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