The "smell of the sea" tied to climate change?
In a recent
report, a Livermore researcher, along with colleagues from Los Alamos
and Oak Ridge national laboratories and the New Mexico Institute of
Mining and Technology, found through computer modeling that dimethyl
sulfide (DMS) will increase significantly in certain parts of the ocean
and decrease in others if the world continues with a business-as-usual
fossil fuel dependency.
DMS, a sulfur-containing compound that affects the heat balance of the
Earth, is one of the major precursors for aerosols and cloud
condensation in the marine boundary layer over much of the remote ocean.
DMS is produced by marine plankton and represents the largest source of
natural sulfur emissions. Upon reaching the atmosphere, DMS is
converted into sulfate aerosols, which reflect sunlight and can
stimulate cloud formation.
"We found that DMS is locally much more sensitive to climate change than
in previous modeling studies," said LLNL's Philip Cameron-Smith. "The
shift in emissions will change the heating patterns."
The Southern Ocean is a locale where the effects of global climate
change are noticeable. In this region, there is substantial biological
production, carbon drawdown and convective return of nutrients.
Using climate simulations with a global ocean biogeochemical model,
scientists looked at the impact of present-day (355 parts per million)
and future (970 parts per million) concentrations of carbon dioxide in
the atmosphere on DMS levels and emissions in the Southern Hemisphere.
What they found was quite a surprise: In the future scenario, the
average DMS emission to the atmosphere was 150 percent more than current
levels in the Southern Ocean. Team members found that sea ice changes
and ocean ecosystem composition shifts caused by changes in temperature,
mixing, nutrient and light regimes caused the increase in DMS in their
"DMS emissions in the Southern Ocean are significantly more sensitive to
climate change than previously thought," Cameron-Smith said. "The
melting of the southern sea-ice has a large impact on DMS flux in the
model, because it opens up a lot of cold open water in which the
DMS-producing plankton thrive (particularly a species called
Phaeocystis). This compensates for the warming of the ocean in other
areas where Phaeocystis stops growing so well."
In the future, scientists may have to consider how ocean acidification,
which is tied directly to climate warming, could affect the plankton
community, and therefore DMS production.