[Vision2020] "Science" Journal Article: Carbon Sink Reversal Increases Global Warming Risk

Ted Moffett starbliss at gmail.com
Fri May 18 13:04:28 PDT 2007


Polar ocean 'soaking up less CO2'
  By Paul Rincon
Science reporter, BBC News

*One of Earth's most important absorbers of carbon dioxide (CO2) is failing
to soak up as much of the greenhouse gas as it was expected to, scientists
say. *

The decline of Antarctica's Southern Ocean carbon "sink" - or reservoir -
means that atmospheric CO2 levels may be higher in future than predicted.

These carbon sinks are vital as they mop up excess CO2 from the atmosphere,
slowing down global warming.

The study, by an international team, is published in the journal Science.

This effect had been predicted by climate scientists, and is taken into
account - to some extent - by climate models. But it appears to be happening
40 years ahead of schedule.

The data will help refine models of the Earth's climate, including those
upon which the predictions of the Intergovernmental Panel on Climate Change
(IPCC) are based.

 Of all the CO2 emitted into the atmosphere, only half of it stays there;
the rest goes into carbon sinks.

There are two major natural carbon sinks: the oceans and the land
"biosphere". They are equivalent in size, each absorbing a quarter of all
CO2 emissions.

The Southern Ocean is thought to account for about 15% of all carbon sinks.

*Sink efficiency *

It was assumed that, as human activities released more CO2 into the
atmosphere, ocean sinks would keep pace, absorbing a comparable percentage
of this greenhouse gas.

The breakdown in efficiency of these sinks was an expected outcome, but not
until the second half of the 21st Century.

Lead researcher Corinne Le Quere and colleagues collected atmospheric CO2
data from 11 stations in the Southern Ocean and 40 stations across the

Measurements of atmospheric CO2 allowed them to infer how much carbon
dioxide was taken up by sinks. The team was then able to see how efficient
they were in comparison to one another at absorbing CO2.

"Ever since observations started in 1981, we see that the sinks have not
increased [in their absorption of CO2]," Corinne LeQuere told the BBC's
Science in Action programme.

"They have remained the same as they were 24 years ago even though the
emissions have risen by 40%."

The cause of the decline in the Southern Ocean sink, the researchers
explain, is a rise in windiness since 1958.

This increase in Southern Ocean winds has been attributed to two factors.

The first is the depletion of ozone in the upper atmosphere, which changes
the temperature of this region.

The second is recent climate change, which warms the tropics more than the
Southern Ocean.

Both these processes change atmospheric circulation over the Southern Ocean,
resulting in stronger winds.

*Churning waters *

Oceans store much of their CO2 in deep waters. But, explained Dr Le Quere,
"as the winds increase, the water in the ocean mixes more".

The British Antarctic Survey (BAS) scientist added: "The CO2 that would
normally be in the deep ocean and would just stay there instead gets brought
up to the surface and outgasses to the atmosphere."

The ocean surface becomes saturated with CO2 and cannot take up any more
from the atmosphere.

Dr Sus Honjo, from the Woods Hole Oceanographic Institution (WHOI) in
Massachusetts, US, is working on a separate project to assess the efficiency
of the Southern Ocean carbon sink, using a different method.

He said recent developments in technology now made possible very detailed
monitoring of marine carbon sinks, with some data available in real time.

"We have been way behind the modellers, who are hungry for numbers. But now
we are starting to catch up because of the new tools and instruments
available," he told BBC News.

Dr Honjo said recent evidence suggested the north-western Pacific appeared
to be another significant CO2 sink.

As CO2 is absorbed by the oceans, it makes them more acidic, harming
populations of marine organisms such as coral. The latest study suggests
that phenomenon will only get worse over the century.

"The problem is that the extra CO2 from human emissions stays in the surface
ocean and does not get removed to deep waters," said Dr Le Quere.

"So the problem gets worse, because the biological organisms affected by
ocean acidification live, of course, at the surface where there is

*Paul.Rincon-INTERNET at bbc.co.uk * <Paul.Rincon-INTERNET at bbc.co.uk>

Climate change affects Southern Ocean carbon sink


Contact: Simon Dunford
s.dunford at uea.ac.uk
University of East Anglia <http://comm.uea.ac.uk/press>

The first evidence that recent climate change has weakened one the Earth's
natural carbon 'sinks' is published this week in the journal Science.

A four-year study by scientists from the University of East Anglia (UEA),
British Antarctic Survey (BAS) and the Max-Planck Institute for
Biogeochemistry reveals that an increase in winds over the Southern Ocean,
caused by greenhouse gases and ozone depletion, has led to a release of
stored CO2 into the atmosphere and is preventing further absorption of the
greenhouse gas.

Lead author Dr Corinne Le Quéré of UEA and BAS said,

"This is the first time that we've been able to say that climate change
itself is responsible for the saturation of the Southern Ocean sink. This is
serious. All climate models predict that this kind of 'feedback' will
continue and intensify during this century. The Earth's carbon sinks – of
which the Southern Ocean accounts for 15% – absorb about half of all human
carbon emissions. With the Southern Ocean reaching its saturation point more
CO2 will stay in our atmosphere."

This new research suggests that stabilisation of atmospheric CO2 is even
more difficult to achieve than previously thought. Additionally,
acidification in the Southern Ocean is likely to reach dangerous levels
earlier than the projected date of 2050.

Professor Chris Rapley, Director of British Antarctic Survey said,

"Since the beginning of the industrial revolution the world's oceans have
absorbed about a quarter of the 500 gigatons of carbon emitted into the
atmosphere by humans. The possibility that in a warmer world the Southern
Ocean – the strongest ocean sink - is weakening is a cause for concern."
The saturation of the Southern Ocean was revealed by scrutinising
observations of atmospheric CO2 from 40 stations around the world. Since
1981 the Southern Ocean sink ceased to increase, whereas CO2 emissions
increased by 40%.
Vision2020 Post: Ted Moffett
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