California experienced centuries-long droughts in the past 20,000 years that coincided with the thawing of ice caps in the Arctic, according to a new study by UC Davis doctoral student Jessica Oster and geology professor Isabel Montañez.
The finding, which comes from analyzing stalagmites from Moaning Cavern in the central Sierra Nevada, was published online Nov. 5 in the journal Earth and Planetary Science Letters.
Global warming gets a lot of attention due to the prospects of huge low lying areas getting submerged. But big changes in regional climate - whether human caused or not - seem much more interesting to me. Such changes could occur at any time.
Ratios of elements in stalagmites provide some indication of changing levels of precipitation.
The sometimes spectacular mineral formations in caves such as Moaning Cavern and Black Chasm build up over centuries as water drips from the cave roof. Those 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," Montañez said. "These are the only climate records of this type for California for this period when past global warming was occurring."
Cooling periods make California wetter.
At the end of the last ice age about 15,000 years ago, climate records from Greenland show a warm period called the Bolling-Allerod period. Oster and Montanez's results show that at the same time, California became much drier. Episodes of relative cooling in the Arctic records, including the Younger Dryas period 13,000 years ago, were accompanied by wetter periods in California.
During the Medieval Warm Period what is now the western United States had an epic drought from 900 to 1300 AD. Imagine such a drought started in the 21st century. How to prevent large areas from becoming mostly uninhabitable due to lack of water? Could we build enough nuclear power plants near oceans to desalinate and pump water a thousand miles inland? What would be the cost?
Alternatively, could windmills in oceans upwind of continents be used to pump more moisture into the air before winds blow over continents? Picture a future where nanotechnology makes manufacturing cheap. This could become an affordable way to bring water inland.
|Share |||Randall Parker, 2009 November 10 11:06 PM Climate Trends|