Climatic changes hastened death of ancient empires

December 6th, 2008 - 7:05 pm ICT by IANS  

Washington, Dec 6 (IANS) Unfavourable climatic changes might have hastened the decline of Roman and Byzantine empires more than 1,400 years ago.Based on chemical signatures in a piece of calcite from a cave near Jerusalem, a team of American and Israeli geologists pieced together a detailed record of the area’s climate from roughly from 200 B.C. to 1100 A.D.

Their analysis reveals increasingly dry weather from 100 A.D. to 700 A.D. that coincided with the fall of both Roman and Byzantine rule in the region.

The researchers, led by University of Wisconsin-Madison geology graduate student Ian Orland and John Valley, a professor, reconstructed the high-resolution climate record based on geochemical analysis of a stalagmite from Soreq Cave, located in the Stalactite Cave Nature Reserve near Jerusalem.

“It looks sort of like tree rings in cross-section. You have many concentric rings and you can analyse across these rings, but instead of looking at the ring widths, we’re looking at the geochemical composition of each ring,” says Orland.

Using oxygen isotope signatures and impurities - such as organic matter flushed into the cave by surface rain - trapped in the layered mineral deposits, Orland determined annual rainfall levels for the years the stalagmite was growing, from approximately 200 B.C. to 1100 A.D.

The current analysis used an advanced ion microprobe in the Wisconsin Secondary-Ion Mass-Spectrometer (Wisc-SIMS) lab to sample spots just one-hundredth of a millimetre across.

That represents about 100 times sharper detail than previous methods. With such fine resolution, the scientists were able to discriminate weather patterns from individual years and seasons, according to a Winconsin University release.

Their detailed climate record shows that the Eastern Mediterranean became drier between 100 A.D. and 700 A.D., including steep drops in precipitation around 100 A.D. and 400 A.D., a time when Roman and Byzantine power in the region waned.

These findings are scheduled for publication in the journal Quaternary Research.

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