Climate change, California droughts linked

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DAVIS, Calif., Nov. 12 (UPI) -- U.S. scientists say they've linked centuries-long droughts in California during the past 20,000 years with thawing of arctic ice caps.

University of California-Davis Professor Isabel Montanez and doctoral student Jessica Oster say their findings come from analyzing stalagmites at Moaning Cavern in the central Sierra Nevada Mountains.

The scientists say the mineral formations in caves build up over centuries as water drips from the cave roof. The drops of water pick up trace chemicals in their path through air, soil and rocks, and deposit the chemicals in the stalagmite.

"They're like tree rings made out of rock," Montanez said. "These are the only climate records of this type for California for this period when past global warming was occurring."

At the end of the last ice age about 15,000 years ago, climate records show a warm period called the Bolling-Allerod period. Oster and Montanez said their study shows California, at the same time, became much drier. Conversely, during episodes of relative arctic cooling, California experienced wetter conditions.

"If there is a connection to arctic sea ice then there are big implications for us in California," Montanez said. "We can't quantify precipitation, but we can see a relative shift from wetter to drier conditions with each episode of warming in the northern polar region."

The research appeared in the Nov. 5 online edition of the journal Earth and Planetary Science Letters.