Arctic warming linked with Calif. droughts

November 11, 2009 12:00:00 AM PST
The Sierra Nevada is giving up age-old secrets that could help better understand climate change - evidence of what happens when the Arctic ice melts has been locked away, inaccessible in mountain caves until now.

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In the study of climate change, this is a new frontier. In Moaning Cave, 200 feet below the Sierra Nevada, is where thousands of years of dripping rainwater evaporates, leaves stalagmites and in their chemical residue what may be a cautionary tale for present times.

"We have looked 10,000 years into the geologic record," says U.C. Davis geologist Dr. Isabel Montanez, who found her evidence by analyzing the chemical make-up of stalagmites in the caves. She dated and then correlated them with temperature records from ice cores taken in Greenland.

"When temperatures increase in the arctic, they reroute jet stream, which normally brings winter water to California."

"The chemistry of the rainwater changes based on temperature above the cave, the rainfall, and the vegetation there is," says U.C. Davis researcher Jessica Oster.

Oster will be getting her Ph.D. soon in paleoclimatology. While earning it, she, and Montanez have made a remarkable discovery, which shows a long-term, direct connection between rising arctic temperatures, and drought in the Sierra Nevada.

"What we know now is that repeatedly, in the past, as we warm up in the high latitudes, we're impacted here," says Montanez.

The stalagmites show four major droughts in 8,000 years and each of them coincides with core records of melting arctic ice. The shortest drought lasted decades. The longest lasted centuries.

"What the climate models tell us is that as we lose ice, the jet stream is very sensitive to that, and migrates northward as that ice amount decreases," says Montanez.

And it is the jet stream with its Pacific storms that delivers water to the Sierra Nevada and the rest of California. Which leads to an obvious question: Is this state's present drought connected to Arctic warming?

Academically, it is hard to say.

"There's a difference between weather and climate," says Oster.

"I can see that in the past that has been bad news in terms of our rainfall. Yes, I would guess that there is some connection that would be relevant, again," says Montanez.

It is evidence of history repeating itself, written in stone.

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