NSF PR 98-41 - August 4, 1998
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Massive Ocean Current May Provide Clues to Global
Warming
Scientists aboard the world's largest scientific drill
ship, the JOIDES Resolution, will soon study a cold-water
current that today is 100 times the size of the mighty
Amazon River. The geologists will set sail from Sydney,
Australia, August 16 on an expedition supported in
part by the National Science Foundation (NSF), a major
contributor to the international Ocean Drilling Program
(ODP), under the aegis of which the research will
take place.
"Racing at remote southwest Pacific Ocean depths,
the Deep Western Boundary Current (DWBC) forms part
of a global system of ocean circulation that distributes
heat around the planet, and may play a key role in
controlling climate change," explains Bruce Malfait,
ODP director at NSF. "This current channels 40 percent
of the world's newly formed, cold deep water throughout
the oceans."
The current's role in controlling climatic changes
will be studied by a team of 26 scientists representing
nine countries. Geologists Bob Carter of James Cook
University (Australia) and Nick McCave of Cambridge
University (UK) will head the scientific team that
will reconstruct the history of the world's largest
deep ocean current.
The scientists will seek answers to questions about
climate change by analyzing samples of deep-sea mud,
which is shaped by the deep currents to form great
mounds on the sea floor. Core samples will be collected
from deep within these mounds.
As the DWBC passes from the Southern Ocean into the
Pacific, it runs adjacent to the landmass of New Zealand.
Mountains associated with the active faults and volcanoes
of New Zealand provide an abundant source of eroded
rock detritus. This sand and mud is fed into the path
of the DWBC along several large deep-sea channels.
Under the influence of the current, the fine-grained
muds are then molded into huge deep-sea sediment drifts.
Some of these drifts are several hundred miles long,
and their sedimentary layers preserve a unique archive
of changes in climate.
"Previous ODP studies of deep-sea sediment drifts
in the North Atlantic have contributed enormously
to our understanding of climate change in the northern
hemisphere," explains McCave. "We anticipate that
southern hemisphere drilling will result in a truly
global picture."
To investigate the history of the DWBC and its sediment
drifts, the scientific team will take core samples
as deep as 1,500 feet below the seafloor, using advanced
drilling technology aboard the JOIDES Resolution.
A hydraulic piston corer will push directly into the
upper layers of sediment, enabling scientists to recover
delicately layered deep-sea muds in an almost undisturbed
state.
Subsequent studies of the core materials, both aboard
the ship and in land-based laboratories, will allow
the scientists to reconstruct climate changes that
have occurred in the southern Pacific ocean, as well
as changes in the strength of the DWBC. Scientists
will continue to study whether global warming changes
the strength of the current. They also want to know
if changes in the current would cause further warming,
or whether it might trigger cooling and the onset
of another period of glaciation.
Texas A&M University in College Station, Texas, is
science operator of the JOIDES Resolution. The JOIDES
will return to Wellington, New Zealand on October
8 following the current expedition.
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