Pacific Ocean Undercurrent May Be A Key To Understanding Global Climate Change

DE KALB, ILL. -- Most scientists studying global climate change look to the atmosphere. Paul Loubere peers into the deep, dark abyss of the eastern Pacific Ocean.

Loubere has found evidence that the equatorial undercurrent--a deep-sea river originating in the Antarctic Ocean--exerts substantial control over marine life activity nearly halfway around the globe near the equator.

Because the marine life regulates the release of carbon dioxide to the atmosphere, Loubere believes nature's watery pipeline also may provide a key to unraveling mysteries of climate change, including global warming.

Loubere, a professor of Geology and Environmental Geosciences at Northern Illinois University, shares his research findings on the possible effects of the equatorial undercurrent in the Aug. 3 issue of the prestigious journal, Nature.

"Until now, it's mostly been assumed that ocean conditions in the eastern equatorial Pacific were largely controlled by atmospheric conditions, such as the trade winds blowing across the tropics," Loubere said. "My research presents the first evidence that there's something else to seriously consider here. And it demonstrates how the climates of different regions of the earth--in this case the South Pole and the Pacific equator--are intrinsically linked."

Loubere studied marine life in the eastern equatorial Pacific Ocean, a primary region for exchange between deeper and surface ocean waters and between the ocean and the atmosphere. The eastern equatorial Pacific is responsible for the greatest release of carbon dioxide from oceans to the atmosphere.

Marine life, particularly the microscopic floating plants known as plankton, absorb carbon dioxide and therefore help regulate its atmospheric release. This is important to temperature regulation of the planet because carbon dioxide is a "greenhouse gas."

Working hundreds of miles off the coast of Peru, near the Galapagos Islands, Loubere over three years took hundreds of sediment samples from four seabed locations to reconstruct a record or marine life activity over the past 130,000 years. All of the locations come under the influence of the southern trade winds. Two of the sites also are affected by the south equatorial current carrying chemical fingerprints of waters originating in the subantarctic.

The biological records varied greatly, depending on proximity to the undercurrent, Loubere discovered. "If tropical or atmospheric processes were controlling things, we should have seen the same biological record everywhere," he said. "The only way to explain that is the influence of the equatorial undercurrent. Where the undercurrent exerts its greatest influence, there's a distinctly different pattern of biological activity through time."

Running about 300 to 400 feet below the ocean's surface, the undercurrent feeds tropical marine life by delivering nutrients, such as carbon dioxide, nitrate, phosphate and iron. About half of the carbon dioxide that could be released into the atmosphere is instead absorbed by plankton and recycled into the ocean.

As documented by researchers in the past, the equatorial undercurrent stretches thousands of miles, originating at some point south of New Zealand and flowing all the way to the tropics. It then flows along the equator from the West Pacific to the East Pacific, where it makes its way to the ocean surface.

"It's quite amazing," Loubere said, "almost like a secret river running in the ocean depths. The question now becomes, could this secret river carry the pulse of the planet's climatic heartbeat from the high latitudes to the tropics?"

Loubere's research was funded through grants from the National Science Foundation.