Massive Ocean Current May Provide Clues To Global Warming

August 04, 1998

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.

National Science Foundation

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