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05/29/91

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Ocean-floor record of climate change subject of researcher's honor

STANFORD -- James C. Ingle will discuss the ocean floor's evidence of past dramatic changes in Earth's climate as a 1991-92 distinguished lecturer appointed by the Joint Oceanographic Institutions, the U.S. advisory committee to the international Ocean Drilling Program.

As one of the four distinguished lecturers appointed to lecture within the international earth sciences community in 1991-92, Ingle will talk on "The Birth and Death of the Japan Sea: Evidence from Drilling the Edge of the Pacific." His focus will be the evolution of the continental margins.

Ingle, a Stanford University geology professor, led 27 scientists from seven countries who cruised the Japan Sea for two months in 1989 aboard the program's research ship Resolution. The researchers drilled and examined samples of deep sea sediment and the oceanic crust that forms the sea's floor beneath the sediments.

By inspecting layers of rock, sand, clay and microfossils above the crust, researchers were able to construct a history of volcanic and seismic activity, changing sea levels, and ancient wind patterns between Japan and the Asian mainland. This historical record makes possible an understanding of present and future climate and oceanographic changes that accompany the greenhouse effect.

"The sediment is like a tape recorder of what has occurred in the Japan Sea through time," said Ingle, who was co-chief of the two-month expedition with Kiyoshi Suyehiro of the University of Tokyo's Ocean Research Institute.

"You get an idea of the frequency and amplitude of these events and the shape of climate change as it occurs. That's one of the things we need in order to predict what's coming. If we can establish the timing and amplitude of climatic events in the recent past, it provides us with clues as to what we're facing in the future."

Some samples contained a cyclic series of dark layers full of organic material followed by layers laced with tiny animal burrows. Ingle said the organically rich layers record times when most life on the sea bottom died because of low oxygen levels. The lighter-colored layers formed as oxygen and life returned.

These alternating layers suggest that higher sea levels during warm periods allowed warm Pacific waters to enter the Japan Sea, creating vigorous circulation, productivity and oxygen-rich conditions, as at present. Then, cold climatic phases and polar ice caused lowered sea

levels, isolating the Japan Sea from the Pacific and creating a stagnant, oxygen-poor environment.

The researchers were able to "read" changes in wind patterns from layers of dust deposited on the ocean floor.

They also were able to determine what forces were responsible for the formation of the Japan Sea 20 million years ago; what processes resulted in the creation of the Philippine Sea and other seas on the margins of the western Pacific; and what produced parts of the land mass that is now California and Nevada.

To gather additional data, the expedition's scientists left a small seismograph in a hole drilled in the crust at the bottom of the Japan Sea.

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