Drought lasts for centuries in North America

Stalagmites in the West Virginia cave have provided the most detailed geological record ever in the climate cycle in eastern North America over the past 7000 years. The new study confirms that during the period when the Earth received less solar radiation, the Atlantic Ocean was cold, many icebergs appeared and rainfall decreased, creating a series of droughts that lasted for centuries.

The team, led by geologist Gregory Springer of Ohio University, looked at traces of Strontium, carbon and oxygen isotopes in stalagmites, creating natural sculptures that hold information about climatic conditions. over time. Scientists found evidence of at least seven droughts during the Holoxe era, according to an article published online in Geophysical Research Letters.

Springer, professor of geoscience, said: 'This sheds light on the sun's impact on the drought on the continent.'

Geologist Gerald Bond said that every 1500 years, the fluctuation of the solar magnetic field weakens its activity and makes North Atlantic cold , creating more icebergs and icebergs, or promote the movement of sediments on the seabed. Other scientists are looking for evidence of 'Bond events' and studying their impact on rain and drought. However, so far these studies have been hampered by incomplete and detailed records.

Buckeye Creek Cave shoots provide an excellent record of the gas cycle, because West Virginia is affected by moisture and small streams from the Pacific and Gulf waters of Mexico.

Other studies attempt to glean the climate cycle data from lakes, but fish and other species often stir up sediment, confusing geological records, co-author Harold Rowe, professor of geo-science Quality at the University of Texas in Arlington, said.

Rowe said: 'The cave is still intact so far. We can see what happened within a few decades. In the Appalachian lakes, we can even observe within a millennium '.

Strontium occurs naturally in soil, and rain washes this metal element through limestone. In the dry season, strontium accumulates in stalagmites, becoming a drought indicator, Rowe explained. Carbon isotopes also record drought information, Springer added, because dry soil slows down biological activity. This makes the soil 'breathe less, changing the blend of light and heavy carbon atoms'.

Stalagmites, 7.9 inches tall, found in Buckeye Creek cave, West Virginia.It is 7000 years old.(Photo: Greg Springer, Ohio University)

In a recent study, scientists cut and polished stalagmites, examined growth classes and then used drills to get 20 specimens along the growth axis. They weigh and analyze metals and isotopes to determine the concentration over time.

The data was consistent with the Bond event, showing the link between weak solar activity and icebergs. However, the study also asserts that the climate cycle causes drought, some of which are particularly pronounced in the middle of the Holocene around 6300 to 4200 years ago. These droughts last for decades or even centuries.

Although modern records show that the temperature in the North Atlantic decreases, in fact, increases humidity and rain, but historical climate events are completely different. In the past, the tropical regions of the Atlantic Ocean also became colder, making the climate drier and creating more droughts.

The climate record shows that B America may face drought again in 500 to 1,000 years , but human-induced global warming may slow this process.

Springer said: 'Global warming will turn things like stalagmites into dust. Natural fluctuations are completely different from what we will see with global warming. '

Although some climate and drought records exist in the West and Midwest regions in North America, the Appalachian Cave has not been studied much to date. The team plans to test another stalagmite record from West Virginia and Tennessee to get a complete picture of North America's climate cycle.

Collaborators of the study included Lawrence Edwards, Ben Hardt and Hai Cheng of the University of Minnesota.