Human Carbon Emissions Make Oceans Corrosive - Study
US: May 23, 2008
WASHINGTON - Carbon dioxide spewed by human activities has made ocean water
so acidic that it is eating away at the shells and skeletons of starfish,
coral, clams and other sea creatures, scientists said on Thursday.
Marine researchers knew that ocean acidification, as it's called, was
occurring in deep water far from land. What they called "truly astonishing"
was the appearance of this damaging phenomenon on the Pacific North American
continental shelf, stretching from Mexico to Canada.
"This means that ocean acidification may be seriously impacting our marine
life on our continental shelf right now, today," said Richard Feely of the
Pacific Marine Environmental Laboratory, part of the US National Oceanic and
Atmospheric Administration.
Other continental shelf regions around the world are likely to face the same
fate, he said.
Plenty of natural activities, including human breath, send the greenhouse
gas carbon dioxide into the atmosphere, but for the last 200 years or so,
industrial processes that involve the burning of fossil fuels such as coal
and petroleum have pushed emissions higher.
Oceans have long been repositories for the carbon dioxide, absorbing some
525 billion tonnes of the climate-warming substance over the last two
centuries -- about one-third of all human-generated carbon dioxide for that
period.
But the daily absorption of 22 million tonnes of the stuff has changed the
chemistry and biology of the oceans, turning it corrosive and making it
difficult or impossible for some animals to produce their calcium carbonate
shells and skeletons, the researchers said.
CHURNING OCEAN WATERS
This change has been observed over the last three decades, the scientists
said in research published in the journal Science.
The acidic waters are coming up onto the continental shelf -- the shallow
area near a big land mass like North America -- because of a long-term
churning ocean pattern that moves cold deep water up toward the surface in
the spring and summer, the scientists said.
The carbon-loaded waters that are now near the US West Coast took about 50
years to get there, starting somewhere on the ocean surface and absorbing
their share of carbon dioxide, then sinking deep down and eventually welling
upward.
The natural process called ocean respiration could not explain the high
levels of carbon dioxide that caused the corrosive water the scientists
found on the continental shelf; the addition of human-generated carbon
dioxide did.
This acidic water is corroding the shells of clams, mussels, starfish and
the free-floating sea-snails called pterapods that nourish young salmon, the
researchers said, citing data from a 2007 research cruise.
Corrosion occurred in water that absorbed carbon dioxide from the atmosphere
in 1957, when levels of this gas were considerably lower than they are now,
the researchers said.
"This means that even if we were to stop instantaneously the current rate of
rise of carbon dioxide in the atmosphere, the corrosivity of these upwelling
waters would increase for the next 50 years," said Burke Hales, a professor
of chemical oceanography at Oregon State University.
(Editing by Will Dunham and Philip Barbara)
Story by Deborah Zabarenko
REUTERS NEWS SERVICE
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