By Sean Henahan, Access Excellence

SANTA BARBARA- A series of deep sea core samples obtained by paleoceanographers at UC Santa Barbara suggest that major changes in global climate can occur in a period as short as a human lifetime.

Using core samples obtained in the Santa Barbara Channel's muddy sediments, the researchers were able to evaluate global climate changes going back 160,000 years. These studies showed that the Earth experienced two major ice ages and numerous lesser swings in climate during that time.

"That record is unmatched in detail by any other drill site in the world ocean," said James P. Kennett, director of UC Santa Barbara's Marine Science Institute, who got the multinational Ocean Drilling Program to send the Joides Resolution into the channel at the tail end of its 1992 drilling season.

Another group of scientists reported uncovering similar climate histories from layered sedimentary cores extracted from several other areas of the sea floor at an international conference on "Paleoclimatory and Paleoceanography from Laminated Sediments".

"These findings strongly confirm that what we're seeing in the Santa Barbara Channel is not simply a local pattern but part of the global climate record," said Kennett, a New Zealand-born marine geologist and pioneering paleoceanographer.

Paleoceanographers rely on the remains of the tiny marine animals - diatoms, foraminifera, radiolarians - that become trapped in the layers of sediment after they die and sink to the bottom to track global climate change. From the types of animals in different sections of the cores, the scientist determine not only their age, but what the environment was like when the organisms were alive, including prevailing temperatures, ocean currents, sea level, and other conditions.

Studies of the Santa Barbara sediments indicate that climate and oceanic circulation has fluctuated not only frequently - more than 30 times in the past 60,000 years, according to UC Santa Barbara researcher Rich Behl - but also extremely fast.

"The cores show that the oceanic circulation system can turn virtually on a button," said Kennett. "It can switch off or on within a single human lifetime."

Other researchers at the conference reported hints of similarly abrupt climatic changes in sediments extracted from widely dispersed parts of the ocean floor: the Caribbean's Carioco Basin, off Venezuela, the south-central portion of the Japan Sea, the Pakistan coast, the Gulf of California's Guaymas Basin, and the Eastern Mediterranean.

Even so, Kennett pointed out, none of these sites provides such strong and clearcut evidence of past global climate change as the sediments recovered from the Santa Barbara basin.

The secret, he explained, lies in the basin's unusual configuration. Sheltered by California's offshore Channel Islands, the bowl-shaped area acts like a giant catch basin, trapping water that remains undisturbed for long periods of time, especially during warm intervals, as the present. Under these conditions, the basin's water remains oxygen-poor. But when the Earth chills and the global oceanic circulation patterns change, younger, oxygen-rich water sweeps in from the North Pacific. The increased store of oxygen rapidly alters the basin's population of bottom-dwelling microorganisms. Instead of anaerobic (non-oxygen) types, the waters become dominated by aerobic (oxygen-dependent) species.

So responsive is the basin to such shifts, Kennett added, that it acts as an "amplifier" - recording even faint hints of climate change in its sediments.

"What we're seeing here and elsewhere is that the Earth is highly sensitive to global change. And the more we examine the climatic record, the more evidence we find that the Earth's environment is poised for change. It can easily be disrupted, and that includes ocean currents," he emphasized.