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Scientists present findings on climate change, Titan's landscape

December 18, 2009 -- SF State geoscientists presented their latest research findings at the American Geophysical Union fall meeting in December, where thousands of earth and space scientists convened in San Francisco.

Black and white radar image showing fluvial systems and river canyons on the surface of Titan.

River canyons on the surface of Titan can be seen in this radar image taken by NASA's Cassini spacecraft. Credit: NASA/JPL

Algae provide climate change clues

Using algae records from the early Pliocene, a time 3-5 million years ago when the Earth's climate was warmer than today, Professor Petra Dekens and her students are investigating how global warming could affect key ocean currents and circulations.

They presented surprising evidence suggesting that coastal upwelling off the California coast was sustained during the Pliocene even though sea surface temperatures were several degrees higher than today. Long associated with cold water, coastal upwelling is the mechanism responsible for California's productive waters. Scientists are eager to find out how global warming will impact coastal upwelling because the cool, nutrient-rich water that it pulls to the surface promotes the growth of algae, which supports productivity further up the food chain, sustaining fisheries and human life.

"The fact that we are finding evidence for coastal upwelling when sea surface temperatures were 2-3 degrees Celcius warmer than the present day, challenges the assumption that upwelling has to involve cold, nutrient-rich water," said Dekens, assistant professor of geosciences. "It could be that some other mechanism brings warm, nutrient-rich water to the surface."

Evolution of Titan's landscape

While many geoscientists study the Earth's atmosphere, rocks and oceans, Professor Leonard Sklar and his students are researching the formation of the landscape on Titan, without leaving their lab here on Earth. Their studies of ice and its resistance to erosion provide critical insight into the processes that shape the surface of Titan, where the bedrock is made of ice as cold as minus 180 degrees Celcius, eroded by rivers of liquid methane. Titan, Saturn's largest moon, has an earth-like landscape complete with lakes, rivers, dunes and seas.

Sklar and his team presented results suggesting that Titan's ice is stronger than most bedrock found on earth, yet it is more brittle, causing it to erode more easily. "At Titan temperatures, our data suggest that ice bedrock is about as strong as the hardest sandstone on earth but not as strong as granite or marble. This has implications for the shape of the landscape and how dramatic it is," said Sklar, assistant professor of geosciences.

Sklar's students also presented new measurements from tests on ice as cold as minus 170 degrees Celcius which reveal that ice gets stronger as temperature decreases. Using liquid nitrogen and snow cone machines they recreated ice samples at ultra cold Titan temperature and their study is the first of its kind to test the strength and resistance of ice at such low temperatures.

"This project tests the validity of the scientific methods and theories that we use here on earth," Sklar said. "It gives us an opportunity to look at how they translate to other environments with different temperature ranges and gravity."

Saving salmon habitats

Also at the American Geophysical Union meeting, Sklar's graduate student Eric Donaldson presented his research into how the supply of the right kind of sediment to river beds affects river habitats for fish including salmon and trout. During the winter, young fish hide from storms in between boulders on river beds, but land use changes and logging can interrupt the supply of rocks and boulders to the river channel, depleting the fish's hiding places. Donaldson is determining the factors that contribute to the presence or absence of this perfect winter habitat and his results will inform restoration efforts for fish populations that are in decline.

"This project is geosciences at its best," Sklar said. "We're developing the basic scientific understanding that will help solve a very practical problem."

-- Elaine Bible


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