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May
10, 2007
'SHORT-CIRCUIT' FOUND IN OCEAN CIRCULATION
Scientists have
discovered how ocean circulation is working in the current that flows
around Antarctica
by tracing the path of helium from underwater
volcanoes.
The team, which included researchers from the University of East Anglia,
has discovered a 'short-circuit' in the circulation of the world's
oceans that
could aid predictions about future climate change.
This process in the Southern Ocean allows cold waters that sink to the
abyss to
return to the surface more rapidly than previously thought.
This affects the Southern Ocean circulation, which links all the other
oceans,
and is also relevant to uptake and release of carbon dioxide by the sea
–
transport between the deep and surface waters in the Southern Ocean is
particularly important for this process.
Understanding oceanic circulation is important because it distributes
heat,
carbon and nutrients around the globe and therefore plays a central
role in
regulating Earth's climate.
The findings, published in Nature,
show that much of the overturning circulation - how water moves and
mixes
vertically - around Antarctica takes place just around the tip of South
America
and in the small region in the Atlantic south of the Falklands, called
the Scotia
Sea.
Co-author Prof Andrew Watson, from UEA's School of Environmental Sciences,
said they were fundamental findings.
“The Southern Ocean is the least well understood part of the
world ocean, but
one of the most important parts. We are going to have to understand its
circulation before we can make really confident predictions about how
the
climate is going to change over the next 100 years.
“This is a piece of knowledge that will help us do that. This
tells us how an
important part of it works”
Leading author Dr. Alberto Naveira Garabato, of the University
of Southampton's
School
of Ocean
and Earth Science and the National Oceanography Centre, said they
represented
an important shift in how scientists think that the ocean circulation
is
driven.
"For many years, oceanographers have regarded the circulation in the
upper
kilometre of the ocean as being independent of that in the abyss. Our
observations show that the two are very much intertwined in the
Southern Ocean,
and that this has substantial implications for how we represent the
ocean in
climate models."
The research shows that a combination of rapid mixing across and rapid
movement
along density surfaces creates a 'short-circuit' in the overturning
circulation, meaning it is more concentrated in this part of the
Southern
Ocean.
The researchers made use of a unique signal - the spread of helium
released
naturally from the Earth’s interior at deep vents in the
Pacific. The helium
dissolves in the deep sea and a plume of this marked water travels down
the
coast of Chile.
It is injected at depth into the Antarctic current on the Pacific side
of Cape Horn.
It then streams through into the Atlantic
with
the current, but in the process is spread, shifted and diffused by the
circulation. Measurements of this spreading of the helium were used to
deduce
the ‘short-circuit’.
Dr. David Stevens, from UEA’s School of Mathematics, and
Wolfgang Roether, from
the University of Bremen, Germany, are also co-authors.
##
Contact:
Cat
Bartman
University of East
Anglia
44-016-035-93007
c.bartman@uea.ac.uk
This text derived from:
http://comm.uea.ac.uk/press/release.asp?id=752
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