Dear EarthTalk: What is the issue with the Gulf Stream in
relation to global warming? Could it really stop or disappear
altogether? If so, what are the ramifications of this? -- Lynn Eytel, Clark Summit, PA
Part of the Ocean Conveyor Belt—a great river of ocean water that
traverses the saltwater sections of the globe—the Gulf Stream stretches
from the Gulf of Mexico up the eastern seaboard of the United States,
where it splits, one stream heading for Canada’s Atlantic coast and the
other for northern Europe and Greenland. By taking warm water from the
equatorial Pacific Ocean and carrying it into the colder North Atlantic,
the Gulf Stream warms up the eastern United States and northwestern
Europe by about five degrees Celsius (roughly nine degrees Fahrenheit),
making those regions much more hospitable than they would be otherwise.
Melting Glaciers Could Disrupt Warm Gulf Stream Currents
Among the greatest fears scientists have about global warming is that it
will cause the massive ice fields of Greenland and other locales at the
northern end of the Gulf Stream to melt rapidly, sending surges of cold
water into the ocean system and interrupting the flow of the Ocean
Conveyor Belt. One doomsday scenario is that such an event would stop or
disrupt the whole Ocean Conveyor Belt system, plunging Western Europe
into a new ice age without the benefit of the warmth delivered by the
Gulf Stream.
Gulf Stream May Affect Climate Change Worldwide
“The possibility exists that a disruption of the Atlantic currents might
have implications far beyond a colder northwest Europe, perhaps
bringing dramatic climatic changes to the entire planet,” says Bill
McGuire, a geophysical hazards professor at University College London’s Benfield Hazard Research Centre1.
Gulf Stream Disruption Could Freeze Europe and North America
Computer models simulating ocean-atmosphere climate dynamics indicate
that the North Atlantic region would cool between three and five degrees
Celsius if Conveyor circulation were totally disrupted. “It would
produce winters twice as cold as the worst winters on record in the
eastern United States in the past century,” says Robert Gagosian of the Woods Hole Oceanographic Institution2.
Gulf Stream Linked to Previous Temperature Changes
The slowing of the Gulf Stream has been directly linked with dramatic
regional cooling before, says McGuire. “Just 10,000 years ago, during a
climatic cold snap known as the Younger Dryas, the current was severely
weakened, causing northern European temperatures to fall by as much as
10 degrees Fahrenheit,” he says. And 10,000 years earlier—at the height
of the last ice age when most of northwestern Europe was a frozen
wasteland—the Gulf Stream had just two-thirds of the strength it has
now.
Could Weakened Gulf Stream Help Offset Global Warming?
A less dramatic prediction sees the Gulf Stream slowing down but not
stopping entirely, causing the east coast of North America and
northwestern Europe to suffer only minor winter temperature dips. And
some scientists even put forth the optimistic hypothesis that the
cooling effects of a weakened Gulf Stream could actually help offset the
higher temperatures otherwise caused by global warming.
Global Warming: A Planetary Experiment
To McGuire, these uncertainties underscore that fact that human-induced global warming3
is “nothing more nor less than a great planetary experiment, many of
the outcomes of which we cannot predict.” Whether or not we can trim our
addiction to fossil fuels might just be the determining factor in
whether global warming wreaks havoc4 around the world, or just causes us minor annoyances.
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