The Gulf Stream does not appear to
be slowing down, say US scientists who have used satellites to monitor
tell-tale changes in the height of the sea.
Confirming work by other scientists
using different methodologies, they found dramatic short-term variability but
no longer-term trend.
A slow-down – dramatised in the
movie The Day After Tomorrow – is projected by some models of climate change.
The research is published in the
journal Geophysical Research Letters.
The stream is a key process in the
climate of Western Europe, bringing heat northwards from the tropics and
keeping countries such as the UK 4-6C warmer than they would otherwise be.
It forms part of a larger movement
of water, the Atlantic Meridional Overturning Circulation, which is itself one
component of the global thermohaline system of currents.
Between 2002 and 2009, the team
says, there was no trend discernible – just a lot of variability on short
The satellite record going back to
1993 did suggest a small increase in flow, although the researchers cannot be
sure it is significant.
“The changes we’re seeing in
overturning strength are probably part of a natural cycle,” said Josh
Willis from Nasa’s Jet Propulsion Laboratory in California.
“The slight increase in
overturning since 1993 coincides with a decades-long natural pattern of Atlantic
heating and cooling.”
Driven by Hollywood, a popular
image of a Gulf Stream slowdown shows a sudden catastrophic event driving snowstorms
across the temperate lands of western Europe and eastern North America.
That has always been fantasy – as,
said Josh Willis, is the idea that a slow-down would trigger another ice age.
“But the Atlantic overturning
circulation is still an important player in today’s climate,” he added.
“Some have suggested cyclic
changes in the overturning may be warming and cooling the whole North Atlantic
over the course of several decades and affecting rainfall patterns across the
US and Africa, and even the number of hurricanes in the Atlantic.”