Human Carbon Emissions Make Oceans Corrosive - Study
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
Story Date: 23/5/2008
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