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Global
Warming And The Gulf Stream
Wind
and the rotation of the Earth are important in determining the flow of
surface currents and local areas of upwelling and downwelling, but the
true driving force of deep water movement is thermohaline circulation.
Credit:
British Society For Geomorphology
Sometimes called the ocean conveyer belt, this mechanism is responsible
for bringing the oxygen that sustains life to the deepest reaches of the
sea, and in moving warmer waters from the tropics towards the poles.
Movement of this conveyer belt depends on sinking of cold water in
certain polar regions, thereby triggering the global thermohaline
circulation.
THE
ARCTIC HALOCLIINE—When sea ice forms, it releases salt into surface waters.
These waters become denser and sink to form the Arctic halocline—a layer of
cold water that acts as barrier between sea ice and deeper warmer water that
could melt the ice. (Illustration by Jayne Doucette, WHOI)
Benjamin
Franklin's Chart of The Gulf Stream
The
Gulf Stream, together with its northern extension towards Europe, the
North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean
current that originates in the Gulf of Mexico, exits through the Strait
of Florida, and follows the eastern coastlines of the United States and
Newfoundland before crossing the Atlantic Ocean. At about 30°W, 40°N,
it splits in two, with the northern stream crossing to northern Europe
and the southern stream recirculating off West Africa. The Gulf Stream
influences the climate of the east coast of North America from Florida
to Newfoundland, and the west coast of Europe. This warm water then
flows up the Norwegian coast, with a westward branch warming Greenland's
tip, at 60°NIt keeps northern Europe about nine to eighteen degrees
warmer in the winter than comparable latitudes elsewhere.
In
this false-color Terra MODIS image, the Gulf Stream can be seen flowing
to the northeast off of the United State’s eastern seaboard. This
image is a false-color representation of water temperatures of the
Atlantic, and since the Gulf Stream is a warm current, it shows up
clearly against the surrounding waters. Temperatures are shown in a
color range; progressing from low to high are purple, blue, turquoise,
green yellow, orange, and red. Black represents a lack of data, and is
used predominantly to represent land. The Gulf Stream shows up as a
winding rope of orange and yellow against the cooler green and blue
waters. NASA
Global warming
could alter this. Because freshwater is less dense than seawater,
increased precipitation, melting of polar glaciers and ice caps could
block the system by reducing the amount of cold water that sinks
downwards.
As
water travels through the water cycle, some water will become part of
The Global Conveyer Belt and can take up to 1,000 years to complete this
global circuit. It represents in a simple way how ocean currents carry
warm surface waters from the equator toward the poles and moderate
global climate. NASA Graphic
In
the Atlantic, warm, high-salinity water flows northward in the Gulf
Stream along the east coast of North America. Some of this water
continues northeastward in the North Atlantic Current toward Iceland and
Norway. Off the coast of Greenland, a portion of the surface water
cools, becomes dense, and sinks. A further portion of surface water
continues into the Arctic Ocean before also cooling and sinking.
Together these sinking plumes off Greenland and in the Arctic form
"deep water" that plays an important role in global oceanic
circulation.
Credit: NASA , UNEP, NSIDC,USGS
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