Ocean uptake of
carbon dioxide
could drop as
carbon emissions
are cut, according to
Earth Institute at
Columbia University.
Volcanic eruptions and
human-caused changes
to CO2 in the atmosphere
strongly influence
the rate at which
the ocean absorbs
carbon dioxide,
says a new study.
"We didn't realize
until we did this work
external forcings,
like changes in the
growth of atmospheric
carbon dioxide,
dominate the variability
in the global ocean
on year-to-year
timescales.
That's a real surprise,"
said lead author
Galen McKinley,
a carbon cycle scientist
at Columbia University's
Lamont-Doherty Earth
Observatory.
"As we reduce
our emissions
our emissions
and the growth rate
of atmospheric carbon
dioxide slows down,
it's important to realize
that the ocean carbon sink
will respond by slowing down."
The paper, published in the
journal AGU Advances,
tries to resolve
the uncertainty
about what caused the ocean
to take up varying amounts
of carbon over the last
30 years.
Earth's largest
carbon sink
is the ocean.
Nearly 40 percent
of the carbon dioxide
added to the atmosphere
by fossil fuel burning
has been taken up
by the ocean.
The scientific community
has puzzled over why
the ocean briefly absorbed
more carbon dioxide
in the early 1990s,
and then slowly
took up less until 2001.
The massive eruption
of Mount Pinatubo in
the Philippines in 1991
caused the sink to
temporarily become
much larger, coincident
with the eruption.
Pinatubo was the
second-largest
volcanic eruption
of the 20th century.
The researchers found
that Pinatubo's emissions
caused the ocean to take up
more carbon in 1992 and 1993.
The carbon sink slowly
declined until 2001.
McKinley cautions that
as global emissions are cut,
there will be an interim phase
where the ocean carbon sink
will slow down and not offset
climate change as much
as in the past.