THE TIMES
FRIDAY SEPTEMBER 7 2001
By Mark Henderson
Science Correspondent
The British
climate could soon become as cold as northern Canada’s
because global warming is slowing the ocean current system,
scientists said yesterday.
Researchers
have found an alarming decline in the strength of a crucial
Arctic current linked to the Gulf Stream, offering the first
evidence that the warm current that acts as northern Europe’s
central heating system may be weakening.
Such a slowdown
would be serious for Britain, bringing the harsh winters that
prevail at similar latitudes elsewhere. Britain is as far north
as Labrador but avoids Canadian weather because of the warm
water that the current carries from the Gulf of Mexico. Temperatures
in Britain are at least 5C (40F) warmer than they would be without
it.
Scientists
have long predicted that global warming could interfere with
ocean circulation, in particular the system known as Global
Conveyor or Belt, of which the Gulf Stream is a part, because
melting ice caps alter the density of seawater. A study of British
and Scandinavian researchers has now shown for the first time
that this is happening.
The volume
of water flowing through the northern loop of the Global Conveyor
Belt, which runs from the Artic to Scotland, has fallen by a
fifth over the past 20 years and the current is weakening further
by 2 to 4 per cent every year, the research shows.
As the cold
water in this current is on its way back across the Atlantic,
having been carried over from the Gulf of Mexico by the Gulf
Stream, it is likely that the latter current is also being affected,
the scientists told the British Association Science Festival
in Glasgow yesterday.
Sarah Hughes,
an oceanographer from the FRS Marine Laboratory in Aberdeen
who worked on the study, said the Gulf Stream may be in trouble:
“If cold water outflow is decreasing, we speculate that
the warm water inflow toward the Arctic, past northern Europe,
will also be reducing.”
The consequences
for Britain could be bleak and would reverse the higher temperatures
that have been anticipated as a result of global warming. “We
do not yet know if we will lose the warmth it brings completely,
but we must continue the monitoring work,” Ms Hughes said.
“It seems that in the past the Conveyor Belt has stopped
and started, sometimes as quickly as within one or two years.
When it stops, northern Europe is cooled by about 5C and we
get a climate similar to that of northern Canada.
“Presently,
European governments are planning for climate change based on
predication of slow steady warming.
The planning
needed for a rapid cooling is very different. Within a decade,
we will know one way or the other.”
The Global
Conveyor Belt works because of differing densities of warm and
cool water. In the Atlantic, warm water rises in the heat of
the Caribbean and drifts northwards and eastwards. When it reaches
Britain, Iceland and Scandinavia it sinks, sending a cold counter-current
across the ocean in the opposite direction.
Extra fresh
water in the North Atlantic, released by ice caps melting because
of global warming, could interfere with the system because it
would lower the salinity and thus the density of seawater in
the region, reducing its ability to sink and sustain the current.
The Gulf
Stream transports 27,000 times as much energy as the maximum
output of all Britain’s power stations, so the effect on
the country’s climate would be great.
