Earth:Piora Oscillation

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Short description: Abrupt cold and wet period in the Holocene Epoch

The Piora Oscillation was an abrupt cold and wet period in the climate history of the Holocene Epoch; it is roughly dated to c. 3900-3000 BC. Some researchers associate the Piora Oscillation with the end of the Atlantic climate regime, and the start of the Sub-Boreal, in the Blytt–Sernander sequence of Holocene climates.

The spatial extent of the change is unclear; it does not show up as a major, or even identifiable, event in hemispheric temperature reconstructions.

First detection

The phenomenon is named after the Val Piora or Piora Valley in Switzerland, where it was first detected; some of the most dramatic evidence of the Piora Oscillation comes from the region of the Alps.[1] Glaciers advanced in the Alps, apparently for the first time since the Holocene climatic optimum; the Alpine tree line dropped by 100 meters. In the Middle East, the surface of the Dead Sea rose nearly 100 meters (300 feet), then receded to a more usual level. It also triggered the collapse of the Uruk period, through decreased temperatures and increased rainfall,[2] which were believed to contribute to Babylonian and Hebrew flood myths.[3]

Link to horse domestication

The Piora Oscillation has also been linked to the domestication of the horse. In Central Asia, a colder climate favored the use of horses: "The horse, since it was so adept at foraging with snow on the ground, tended to replace cattle and sheep."[4] The Piora period seems associated with a period of colder drier air over the Western and Eastern Mediterranean, and may have depressed rainfalls as far afield as the Middle East. It is also associated with a sudden onset of drier weather in the central Sahara.

Causes

The cause or causes of the Piora Oscillation are debated. A Greenland ice core, GISP2, shows a sulfate spike and methane trough c. 3250 BCE, suggesting an unusual occurrence — either a volcanic eruption or a meteor or an asteroid impact event. Other authorities associate the Piora Oscillation with other comparable events, like the 8.2 kiloyear event, that recur in climate history, as part of a larger 1500-year climate cycle.

It may also be caused by changes in solar activity and orbital parameters. [5]

See also

Notes

  1. Lamb, pp. 124, 128, 143.
  2. Radner, Karen; Moeller, Nadine; Potts, D.T. (2020). The Oxford History of the Ancient Near East: Volume I: From the Beginnings to Old Kingdom Egypt and the Dynasty of Akkad. Oxford University Press. pp. 163. ISBN 9780197521014. 
  3. Lamb, p. 128.
  4. Matossian, p. 43.
  5. Hou & Wu 2020, p. 13.

References