New climate record shows century-long droughts in eastern North America

Aug 19, 2008
The stalagmite, which is 7.9 inches long, was collected from a site in Buckeye Creek Cave, West Virginia. It is 7,000-years-old. Image: Gregory Springer, Ohio University

A stalagmite in a West Virginia cave has yielded the most detailed geological record to date on climate cycles in eastern North America over the past 7,000 years. The new study confirms that during periods when Earth received less solar radiation, the Atlantic Ocean cooled, icebergs increased and precipitation fell, creating a series of century-long droughts.

A research team led by Ohio University geologist Gregory Springer examined the trace metal strontium and carbon and oxygen isotopes in the stalagmite, which preserved climate conditions averaged over periods as brief as a few years. The scientists found evidence of at least seven major drought periods during the Holocene era, according to an article published online in the journal Geophysical Research Letters.

"This really nails down the idea of solar influence on continental drought," said Springer, an assistant professor of geological sciences.

Geologist Gerald Bond suggested that every 1,500 years, weak solar activity caused by fluctuations in the sun's magnetic fields cools the North Atlantic Ocean and creates more icebergs and ice rafting, or the movement of sediment to ocean floors. Other scientists have sought more evidence of these so-called "Bond events" and have studied their possible impact on droughts and precipitation. But studies to date have been hampered by incomplete, less detailed records, Springer said.

The stalagmites from the Buckeye Creek Cave provide an excellent record of climate cycles, he said, because West Virginia is affected by the jet streams and moisture from the Gulf of Mexico and the Pacific Ocean.

Other studies have gleaned climate cycle data from lakes, but fish and other critters tend to churn the sediment, muddying the geological record there, said study co-author Harold Rowe, an assistant professor of geological sciences at the University of Texas at Arlington.

"(The caves) haven't been disturbed by anything. We can see what happened on the scale of a few decades. In lakes of the Appalachian region, you're looking more at the scale of a millennium," Rowe said.

Strontium occurs naturally in the soil, and rain washes the element through the limestone. During dry periods, it is concentrated in stalagmites, making them good markers of drought, Rowe explained. Carbon isotopes also record drought, Springer added, because drier soils slow biological activity. This causes the soil to "breathe less, changing the mix of light and heavy carbon atoms in it," he said.

In the recent study, the scientists cut and polished the stalagmite, examined the growth layers and then used a drill to take 200 samples along the growth axis. They weighed and analyzed the metals and isotopes to determine their concentrations over time.

The data are consistent with the Bond events, which showed the connection between weak solar activity and ice rafting, the researchers said. But the study also confirmed that this climate cycle triggers droughts, including some that were particularly pronounced during the mid-Holocene period, about 6,300 to 4,200 years ago. These droughts lasted for decades or even entire centuries.

Though modern records show that a cooling North Atlantic Ocean actually increases moisture and precipitation, the historic climate events were different, Springer said. In the past, the tropical regions of the Atlantic Ocean also grew colder, creating a drier climate and prompting the series of droughts, he explained.

The climate record suggests that North America could face a major drought event again in 500 to 1,000 years, though Springer said that manmade global warming could offset the cycle.

"Global warming will leave things like this in the dust. The natural oscillations here are nothing like what we would expect to see with global warming," he said.

Though some climate and drought records exist for the Western and Midwest areas of North America, the eastern Appalachian region hasn't been studied much to date, Rowe said. The research team plans to examine additional stalagmite records from West Virginia and Tennessee to paint a better picture of North American climate cycles.

Source: Ohio University

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agg
3.5 / 5 (8) Aug 19, 2008
The climate record suggests that North America could face a major drought event again in 500 to 1,000 years, though Springer said that manmade global warming could offset the cycle.

"Global warming will leave things like this in the dust. The natural oscillations here are nothing like what we would expect to see with global warming," he said.

First we decide what we expect to see. Then we look for so called facts that support our bias.
Then we write more bullshit grants.
GrayMouser
3.7 / 5 (6) Aug 19, 2008
The article when along well enough and then jumped to the completely unwarranted conclusion that what is currently occurring isn't natural.

So much for objectivity.
rubberman
not rated yet Aug 20, 2008
AGG, perhaps you have some way for scientists to come up with funding other than grants? From what I understand, science is a non-profit endeavour until someone takes a scientific discovery and developes a practical application for it. I do agree that it is bullshit when science that is supposed to be based on drawing conclusions from physical evidence starts off with a conclusion and then tries to manipulate the data to fit it, but both the pro and anti AGW camps are guilty of this.

Graymouser is correct in saying that to draw any conclusion based on this evidence in simply not objective.
wvdirtboy
not rated yet Aug 21, 2008
Hi folks. This is Springer, the lead author of the paper described in this news posting. Several people have commented on my quote about "global warming leaving things like this in the dust." There was much more to that comment than what made the press release. Our PR person did a good job with the press release, but I have asked her to revise the "dust" paragraph to include some important caveats that are missing. Our research says nothing about Global Warming and I want it made clear that I was speculating upon a possibility... not a certainty. I'll be a little more careful next time. :-)
rubberman
not rated yet Aug 22, 2008
As long as your first name isn't Jerry....
jeffsaunders
not rated yet Oct 14, 2008
Until that comment mentioned above the article was quite good. Congrats to the PR department and yourself for doing the research.

We have so many comments in the media saying that the warming will lead to droughts and famine, when so does the cooling; it seems that a change in temperature brings a change in precipitation that can result in droughts here and floods there - no surprise that when things are different - things are different.

I hope you have based you research results on drills from more than one individual cave, as water percolation levels may be affected by other changes besides levels of precipitation. e.g. land form coverage and stream relocation could alter the amount of water and the age of water acting as the source of the water that creates the stalagmites.

P.S next time I go Caving will I find that all the stalagmites have holes in them?