Piora fluctuation

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Holocene climatic fluctuations

The two Piora fluctuations I and II, also known as the Piora oscillation , denote two Holocene temperature drops in rapid succession in Central Europe , which are assumed to be −2 to 2.5 ° C. The times vary depending on the source between 4200 and 3100 BC. Chr.

definition

The two Piora fluctuations were verified by pollen analysis on the lakes and moors of Lago di Cadagno in the Pioratal , Canton Ticino, for the western Alps . In the Tyrolean Ötztal region of the Eastern Alps , the two Rotmoos fluctuations roughly correspond to them . The death of the glacier mummy known as " Ötzi " on the Tisenjoch occurred towards the end of the second glacier advance around 5100 years ago (4500 radiocarbon years).

Chronological order

After the end of the Würm Ice Age , a warm period began about 11,700 years ago, the Holocene . As a result of the warmer climate, the tundra vegetation of the Ice Age in Central Europe and North America increasingly gave way to forest cover, initially with birch and pine trees , the pollen of which was preserved in the sediments of lakes and bogs and can be detected by pollen analyzes. In the Atlantic , the optimal climate of the Holocene, the tree line in the Alps was 200 to 300 m higher than today. The boreal belt of coniferous forest was up to 300 km further north in Siberia and North America.

The Piora fluctuations correspond to a number of globally proven climatic events towards the end of the Atlantic and at the beginning of the subboreal , so that one can speak of a global cooling. From the studies of the Greenland ice sheet from the GRIP - ice core also is a cooling by about 3350 cal BC forth (Magny and Haas of 2004.).

Piora fluctuation I

The piora oscillation I, in English as a 5.9 kilo year event referred forms part of the bond events (bond event 4) and is connected to the Rotmoos fluctuation I identical. It is located at the end of the Atlantic in the period 4100 to 3700 BC. BC and more narrowly according to Holzhauser (2009) between 3900 and 3780 BC. It ended the Neolithic subpluvial and started the desiccation of the Sahara , which continues to this day . With it began the migratory movements to the great river valleys ( Nile , etc.), the consequence of which was the emergence of the first complex, highly organized states in the 4th millennium BC. Chr. Was.

As with the previous Misox fluctuation , the southern hemisphere showed negative temperature anomalies during the Piora fluctuation I. The conditions in the northern hemisphere were less clear - the interior of North America was cold due to the remaining Laurentid ice sheet , whereas positive anomalies predominated in Scandinavia . According to Alverson (2003), temperatures in Europe are even moderate to mild. In China , the Piora fluctuation I can be detected as a cold event in the lake sediments of Erhai Lake .

Piora fluctuation II

The Piora fluctuation II is identical to the Rotmoos fluctuation II . It took place at the beginning of the Subboreal in the period 3500 to 3000 BC. (Until 3110 BC according to Holzhauser). In the Swiss Alps it is formed as a high glacier stand that reached the level of 1850.

causes

The exact causes of the Piora fluctuations are still being discussed. A combination of different factors is suspected: changes in solar radiation due to a different earth orbit (orbital forcing), changes in ocean currents or changes in solar activity. The main cause of the Piora fluctuations is likely to have been a significant reduction in solar activity . The decreased solar irradiation had possibly induced Bond events with the help of the ENSO circulation in the North Atlantic area.

consequences

Global effects of climate fluctuations were drought in many regions of the world, which resulted in the growth of steppe areas and deserts . The tundras also widened again towards the south as a result of the enlargement of the area of permafrost . In the high mountains, there was increased precipitation and the glaciers penetrating .

As a result of the Piora fluctuations, numerous changes occurred in the Neolithic cultures of Central Europe. The discovery of the man from Tisenjoch (towards the end of the Piora fluctuation II) stimulated numerous studies on the history of climate and settlement in the Alps. A change in the species composition of the plants is accompanied by a change in the slash-and-burn and settlement horizons of this time. At around 5320 BP, the level of Lake Constance began to rise rapidly, according to dating using dendrochronology and radiocarbon methods . Early human settlements on the lake shore had to be abandoned. The areas for transhumance and alpine farming were severely restricted. The increasing aridization of the Sahara may have led to the formation of irrigation cultures in the Nile Valley, which eventually led to ancient Egypt .

It is still controversial to what extent the Asian monsoon was weakened at the time.

literature

  • W. Dansgaard, SJ Johnsen, HB Clausen, D. Dahl-Jensen, NS Gundestrup, CU Hammer, CS Hvidberg, JP Steffensen, AE Sveinbjornsdottir, J. Jouzel , G. Bond: Evidence for general instability of past climate from a 250- kyr ice-core record. In: Nature. 364, 1993, pp. 218-220.
  • PM Grootes et al .: Comparison of oxygen isotope records from GISP2 and GRIP Greenland ice-cores. In: Nature. 366, 1993, pp. 552-554.
  • HH Lamb: Climate and Cultural History. The influence of the weather on the course of history. Rowohlt Taschenbuch Verlag, Reinbek 1994, ISBN 3-499-55478-X .
  • Helmut Schlichtherle : L'histoire des occupations palustres dans le bassin du Federsee (Baden-Württemberg, Germany). Unpublished, 2012.
  • M. Schwarzbach: The climate of prehistory. An Introduction to Paleoclimatology. Ferdinand Enke Verlag, Stuttgart 1993, ISBN 3-432-87355-7 .
  • A. Stapfer: Pollen analysis in Val Piora (Ticino): A contribution to the climate and vegetation history of the post-ice age. In: Geographica helvetica (Geogr. Helv.) Volume 46, No. 4, 1991, pp. 156-164.
  • H. Zoller: Pollen analysis of the vegetation history of insubric Switzerland. In: Memoranda of the Swiss Natural Research Society. 83, 1960, pp. 45-156.

Web links

Individual evidence

  1. ↑ Spindler, K., among others: The man in the ice. New finds and results . Ed .: Publication of the Research Institute for Alpine Prehistory of the University of Innsbruck 2. 1995.
  2. ^ A b M. Magny, JN Haas: A major widespread climatic change around 5300 cal. Yr BP at the time of the Alpine Iceman . In: Journal of Quaternary Science . tape 19 (5) , 2004, pp. 423-430 .
  3. ↑ G. Patzelt: The timing and extent of postglacial climatic fluctuations in the Alps . In: B. Frenzel (Ed.): Dendrochronology and postglacial climatic fluctuations in Europe (=  Earth science research . Volume 13 ). Wiesbaden: Steiner 1977, p. 248-259 .
  4. ^ H. Zoller: Age and extent of postglacial climatic fluctuations in the Swiss Alps . In: B. Frenzel (Ed.): Dendrochronology and postglacial climatic fluctuations in Europe (=  Earth science research . Volume 13 ). Wiesbaden 1977, p. 271-281 .
  5. ^ H. Holzhauser: On the wrong track to the history of the glacier . In: Haller's landscapes and glaciers. Contributions to the events of the Swiss Academies 2008 for the anniversary year “Haller 300” (Ed.): Reprint from the communications of the Natural Research Society in Bern. New episode . tape 66 , 2009, p. 173-208 .
  6. ↑ Nick Brooks: Cultural responses to aridity in the Middle Holocene and increased social complexity . In: Quaternary International . tape 151 , no. 1 , 2006, p. 29-49 .
  7. ^ Heinz Wanner, among others: Structure and origin of Holocene cold events . In: Quaternary Science Reviews . tape 30 , 2011, p. 3109-3123 .
  8. ↑ KD Alverson: Paleoclimate, Global Change and the Future . Springer, New York 2003.
  9. ↑ Zhou Jing, Wang Sumin, Yang Guishan, Xiao Haifeng: Younger Dryas Event and Cold Events in Early-Mid Holocene: Record from the sediment of Erhai Lake . In: Advances in Climate Change Research . 3 (Suppl.), 2007, p. 1673-1719 .
  10. ↑ A. Wipf: Glacier-historical studies in the late and post-glacial area of ​​the rear Lauterbrunnen valley (Bernese Oberland, Switzerland) . In: Geographica Helvetica . 56, H. 2, 2001, p. 133–144 ( digital copy [PDF]).
  11. ↑ J. Emile-Geay, among others: El Niño as a mediator of the solar influence on climate . In: Paleoceanography . tape 22 , 2007.
  12. ↑ Lamb, pp. 140 f., 146, 158 f.
  13. ↑ Schlichtherle, unpublished, 2012.
  14. ↑ Schwarzbach, pp. 222-226, 241-255.
  15. ↑ J. Xiao, inter alia: Holocene weak monsoon intervals indicated by low lake levels at Hulun Lake in the monsoonal margin region of northeastern Inner Mongolia, China . In: Holocene . tape 19 , 2009, p. 899-908 .
  16. ↑ J. Zhang, inter alia: Holocene monsoon climate documented by ocygen and carbon isotopes from lake sediments and peat bogs in China: a review and synthesis . In: Quaternary Sci. Rev. Band 30 , 2011, p. 1973-1987 .