Are we facing colder winters?
- Excerpt: "If the Atlantic Ocean is moving less heat northwards, then
the atmosphere must take up the slack to keep the tropics-to-poles
system balanced. McBean said the most likely way for this to happen
would be an increase in violent storms in the area from the mid-
United States to mid-Canada. "
---------- Atlantic Currents Slowing Down -------
Are we facing colder winters?
Weaker ocean currents pose risk
Warm water not making it north
Dec. 1, 2005. 05:27 AM
MONTREALScientists have detected a weakening of key water currents
in the Atlantic Ocean, raising fears of major ecological upheavals,
including colder winters in northeastern Canada and Europe.
These currents, which continually move warm and cold water around the
Atlantic, have slowed by 30 per cent since 1992, a drop unequalled
since the last Ice Age, British researchers reported yesterday in the
If the trend continues, experts forecast that changes to the so-
called Atlantic conveyor belt could trigger major environmental
disruptions, including not only colder winters in parts of Canada and
Europe but severe declines in the North Atlantic fisheries, droughts
in India and sea levels rising as much as a metre along the eastern
seaboard of North America.
Computer projections show such catastrophic environmental effects
would hit the Northern Hemisphere within two decades of any collapse
of the Atlantic conveyor.
"The consequences would be global, not just regional," said Bill
Hare, an expert in the field, who is attending the two-week United
Nations climate change conference in Montreal.
His views were echoed by Gordon McBean, a former head of the
Meteorological Service of Canada, who directs the federal funding
agency for climate science.
"Although important for Europe's climate, this is also very important
for global climate," McBean wrote in an email.
The Atlantic conveyor carries deep cold water from the Arctic down
south to the equator and returns to the north warm water, which is
close to the surface.
If the Atlantic Ocean is moving less heat northwards, then the
atmosphere must take up the slack to keep the tropics-to-poles system
balanced. McBean said the most likely way for this to happen would be
an increase in violent storms in the area from the mid-United States
Climate change poses a threat to the Atlantic conveyor. Rising air
temperatures melt polar ice, making water flowing out of the Arctic
less salty, which is also less dense. This water then can't sink
enough to flow back south.
Disruption of the Atlantic conveyor had been widely predicted.
A report from the U.S. defence department earlier this year noted the
consequences of a slowdown in the Atlantic conveyor, saying that the
climate of Britain and northern Europe would be more like Siberia's
and the average rainfall would decline by 30 per cent.
But yesterday's report conducted by a research team from Britain's
National Oceanography Centre found the first hard evidence for the
change after comparing temperature and salinity readings from last
year to four previous snapshots dating back to 1957 all recorded by
monitoring devices along a line from Morocco to Miami.
Measurements in 1981 and 1992 had shown little change from the
readings of 1957.
But a major shift was revealed in readings from 1998 and last year,
with less of the warming current getting up to Greenland and also
less of the cold, deep returning current coming back.
Lead researcher Harry Bryden told a news conference yesterday in
London that long-term monitoring was essential to learn whether the
figures signalled a one-time readjustment or the start of a trend.
"It is like a radiator heating the atmosphere and is too important to
leave to periodic observations," Bryden said.
Bryden's concern was echoed by Canadian climate and ocean experts.
"This says that the ocean circulation isn't rock-solid stable, but we
still don't know how unstable it is," said Allyn Clark, a circulation
expert at the Bedford Institute of Oceanography in Dartmouth.
Clark said a key question is whether the weakening of the conveyor
was a trend that would continue.
Concerted research into the issue began only in the past two decades,
"It takes a long time to do the observational studies and then do the
modelling studies to answer these questions," Clark said.
British and American scientists are tackling the Atlantic conveyor
questions by deploying semi-permanent monitoring devices along a line
25 degrees north of the equator, where the earlier temperature and
salinity measurements were also taken.
The British research found evidence that much greater amounts of
water are simply going around in a circle in this subtropical region
and not completing the full circuit up to the Arctic and back.
As well, the monitoring program includes new seabed recording devices
at three crucial locations off the coast of North America to directly
measure the cold water flowing south from the Arctic, known as the
deep western boundary currents.
News of the disruptions to the Atlantic conveyor spread quickly among
participants at the U.N. climate change conference.
"This should provide added impetus to the negotiations," said Hare,
who works at the Potsdam Institute for Climate Impact Research, an
international research institute.
Conference president Stéphane Dion, the federal environment minister,
said he was not aware of the research findings.
Article in "Nature":