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Climate
Warming Reduces Ocean Food Supply
In a NASA study, scientists
have concluded that when Earth's climate warms, there is a
reduction in the ocean's primary food supply. This poses a
potential threat to fisheries and ecosystems.
By comparing nearly a decade of
global ocean satellite data with several records of Earth's
changing climate, scientists found that whenever climate
temperatures warmed, marine plant life in the form of microscopic
phytoplankton declined. Whenever climate temperatures cooled,
marine plant life became more vigorous or productive.
The
results provide a preview of what could happen to ocean biology
in the future if Earth's climate warms as the result of
increasing levels of greenhouse gases in the atmosphere.
"The
evidence is pretty clear that the Earth's climate is changing
dramatically, and in this NASA research we see a specific
consequence of that change," said oceanographer Gene Carl
Feldman of NASA's Goddard Space Flight Center, Greenbelt. Md. "It
is only by understanding how climate and life on Earth are linked
that we can realistically hope to predict how the Earth will be
able to support life in the future." Feldman is a co-author
on the study, which was published this week in Nature.
Phytoplankton are
microscopic plants living in the upper sunlit layer of the ocean.
They are responsible for approximately the same amount of
photosynthesis each year as all land plants combined. Changes in
phytoplankton growth and photosynthesis influence fishery yields,
marine bird populations and the amount of carbon dioxide the
oceans remove from the atmosphere.
"Rising levels of
carbon dioxide in the atmosphere play a big part in global
warming," said lead author Michael Behrenfeld of Oregon
State University, Corvallis. "This study shows that as the
climate warms, phytoplankton growth rates go down and along with
them the amount of carbon dioxide these ocean plants consume.
That allows carbon dioxide to accumulate more rapidly in the
atmosphere, which would produce more warming."
The
findings are from a NASA-funded analysis of data from the
Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument on the
OrbView-2 spacecraft, launched in 1997.
The uninterrupted
nine-year record shows in great detail the ups and downs of
marine biological activity or productivity from month to month
and year to year. Captured at the start of this data record was a
major, rapid rebound in ocean biological activity after a major
El Niño event. El Niño and La Niña are major
warming or cooling events, respectively, that occur approximately
every 3-7 years in the eastern Pacific Ocean and are known to
change weather patterns around the world.
Ocean plant
growth increased from 1997 to 1999 as the climate cooled during
one of the strongest El Niño to La Niña transitions
on record. Since 1999, the climate has been in a period of
warming that has seen the health of ocean plants diminish.
Source / Credit: NASA
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Scientific
Frontline®
Image
of the Pacific from the late 1990's
Phytoplankton
