Oceans and climate – Feb 23

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Dumping of CO2 threatens oceans with massive extinction, scientist says
(“Signs of life out there, disaster back here”)
Nicholas Read, Vancouver Sun
Unless we halt completely the emission of carbon dioxide from the world’s energy systems, we risk an oceanic catastrophe worse than the one associated with the disappearance of the dinosaurs.

That’s the message a chemical oceanographer and environmental scientist intends to deliver to a conference on the future of the world’s oceans today at the University of Victoria.

Ken Caldeira, who teaches out of the Carnegie Institution at Stanford University in California, says the level of acidification caused by dumping hundreds of billions of tonnes of carbon dioxide into the world’s oceans is so great that it could cause a major disruption on par with, or worse than, the sudden dumping of sulphuric acid into the oceans 65 million years ago when an asteroid slammed into the Earth’s surface.

When that happened, he said, it took 500,000 years for plankton to reappear, two million years for corals to redevelop, and 10 million years for the current level of oceanic biodiversity to re-emerge.

And unless drastic steps are taken now, Caldeira says, a similar marine disaster could occur within the next few decades.
(22 Feb 2007)
Contributor Bill Henderson writes:

Some cool graphs from Carnegie Inst. Dept. of Global Ecology

Warming oceans contain less oxygen for fish, conference told
Nicholas Read, Vancouver Sun
Some areas seeing ‘dead zones’ of excessive nitrogen, limited oxygen
—-
VICTORIA — As the temperature of the world’s oceans increases due to global warming, there may be more and more areas where oxygen in the water is either limited or absent, and that could have a deadly effect on huge numbers of marine species, a U.S. biological oceanographer warned a conference on the future of the world’s oceans Thursday.

Lisa Levin, who works out of the Integrative Oceanography Division at the Scripps Institution of Oceanography in La Jolla, Calif., told an audience at the University of Victoria that most so-called “dead zones” are caused by excessive levels of nitrogen being dumped into the oceans. Nitrogen is a component of most commercial fertilizers, and rivers carry the residue of these fertilizers from farms to the ocean, she said.

When this happens, she explained, the number of nitrogen-consuming phytoplankton rises. This, in turn, prompts a concomitant rise in the number of microbes that feed on the phytoplankton — microbes that collectively consume great quantities of oxygen.

As a consequence, the number of man-made dead zones — areas of the ocean where oxygen is either depleted or gone — has grown to more than 150 in the last 50 years, some of them several thousand square kilometres in size.

But now, because of global warming, Levin said, it’s possible that the number of such zones, where fish that need oxygen can’t thrive, could rise even higher.
(23 Feb 2007)

Southern Ocean Being “Strangled” by Greenhouse Gases
Michael Byrnes, Reuters via Planet Ark
SYDNEY – The pristine Southern Ocean, which swirls around the Antarctic and absorbs vast amounts of carbon dioxide from the atmosphere, is slowly losing a fight against industrial gases responsible for global warming, scientists say.

The Southern Ocean’s unique wind and storm conditions make it the world’s greatest carbon “sink”; the earth’s oceans absorb a third of the carbon dioxide in the atmosphere, and the Southern Ocean absorbs a third of that.

But the waters that surround Antarctica are becoming more acidic as they absorb increasing amounts of carbon dioxide produced by nations burning fossil fuels such as oil, coal and natural gas.

Deforestation and slash-and-burn farming also releases vast amounts of carbon dioxide stored in timber or peat bogs.

The more acidic an ocean gets, the less carbon dioxide it can soak up.

“It is becoming more difficult for the Southern Ocean to absorb the excess carbon dioxide,” said Dr Will Howard of Australia’s Antarctic Climate and Ecosystems Cooperative Research Centre.
(23 Feb 2007)