Misox fluctuation

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Reconstructed central Greenland temperature curve with a clear negative deflection at 8200 years BP.

The Misox fluctuation ( called 8.2 kiloyear event in the Anglo-American region ) was a sharply defined, relatively short-term climate change around 8,200 years Before Present . The name is derived from the Misox valley in the Swiss Alps , in the deposits of which it was first detected in 1960 by the Swiss botanist Heinrich Zoller (1923–2009). In the course of the Misox fluctuations in Mesolithic Central , Northern and Western Europe, there was a regionally different but considerable cooling of around 2 ° C on average over the course of a few decades. It can also be found in the Greenland ice. The climatic fluctuations, triggered by an interruption of the thermohaline circulation of the North Atlantic Current , the northern extension of the Gulf Stream , had effects as far as the Middle East . In Mesopotamia were droughts and the conversion to a semi-arid climate the result.

The climatic effects of the Misox fluctuation can be demonstrated in the development of vegetation in Europe for a good hundred years. After less than 100 years, the rewarming took place as fast as the cooling, after the flow conditions in the North Atlantic had stabilized again.

Dating

According to the English name, the beginning of the Misox fluctuation is 8200 years BP or 6250 years BC. Chr. Indicated. In Greenland it is 6,225 BC. BC. The fluctuation thus falls into the Elder Atlantic . The misox fluctuation is equivalent to Bond event 5 .

The climatic fluctuation was detected for the first time for the alpine region by means of pollen analysis studies of moor sediments in the Misox valley in the Swiss canton of Graubünden . This discovery was made in 1960 by Heinrich Zoller (1923–2009), Professor of Botany at the University of Basel . Investigations at Soppensee (Switzerland) and Schleinsee (southern Germany) showed that the layered sediments show a similar change in pollen distribution in comparison. The data could be correlated and absolutely dated for a layer of tephra that occurred in the sediments of both lakes. A rapid change in vegetation at the time of the Misox fluctuation was also evident for the montane altitude range .

distribution

Since the Greenland ice cores of the GRIP (" Greenland Ice Core Project ") and the GISP (" Greenland Ice Sheet Project ") fluctuated around 6200 years BC. BC can be determined, the thesis is proven that this climate change was global or at least widespread in the northern hemisphere .

In Norwegian lakes, the profiles of sediments could also be correlated with the anomaly found in the ice cores 8200 years ago. The cooling confirmed by these investigations is called the Finse event in Norway .

causes

Map of the glaciations at Lake Agassiz and Lake Ojibway approx. 7900 BP. Teller and Leverington, 2004 (US Geological Survey)

The Misox fluctuation followed the final breakup of the Laurentian Ice Sheet , which triggered a gigantic pulse of meltwater from the Ojibway and Agassiz lakes in North America. The water masses made their way over Hudson Bay into the North Atlantic . The enormous freshwater entry into the North Atlantic under tied largely the creation of denser and therefore sedimenting higher salinarem water in high latitudes normally due to the freezing out of ice takes place. Due to this disruption of the thermohaline circulation , the heat transport to the North Atlantic via the Gulf Stream came to a standstill. After the freshwater pulse subsided, the formation of deep water began again.

Effects

Estimates of the cooling achieved depend on the interpretation of the proxy data . The values ​​vary between 1 and 5 ° C. In Greenland the drop in temperature was 3.3 ° C, which took place here in less than 20 years, the fluctuation lasted a total of around 150 years, the cold maximum extended over 60 years. Tropical records from ancient coral reefs in Indonesia suggest a cooling of 3 ° C. At the same time, carbon dioxide concentrations fell by around 25 ppm over a period of around 300 years .

Sea level

The original meltwater pulse caused the sea ​​level to rise by 0.5 to 4 meters. Based on estimates of the volume of the two lakes Ojibway and Agassiz as well as the size of the crumbling ice sheet , values ​​of 0.4 to 1.2 meters are achieved. Sea level data from today's delta regions , however, contain a signal for a rapid rise of 2 to 4 meters, which superimposes that for the general, post-Pleistocene sea level rise. Due to the isostatic effects of the displaced meltwater masses, the meltwater signal only reached its full strength far away from the place of origin ( Hudson Bay ). For example, only around 20% of the global average is achieved in the Mississippi Delta, 70% in Northwest Europe and 105% in Asia. The cooling during the Misox fluctuation was temporary, but the rise in sea level caused by the meltwater pulse was permanent.

vegetation

Evidence of cooling within the Early Holocene , which was previously considered to be climatically stable, led to the rapid recognition and dissemination of pollen analysis in the representation of paleoclimatic relationships. With such cooling occurs within a period of a few decades in the higher levels of the Alps to the decline of silver fir ( Abies alba ), spruce ( Picea abies ), larch ( Larix decidua ), mountain pine ( Pinus mugo ) and their replacement by shrubs such as juniper ( Juniperus communis ), sea ​​buckthorn ( Hippophae rhamnoides ), willow ( Salix sp. ), green alder ( Alnus viridis ), heather family (Ericaceae), heather ( Calluna vulgaris ) and crowberry ( Empetrum nigrum ). This change in the species spectrum is also evident in the pollen that was preserved in the deposits of lakes and bogs.

Cultural history

The climatic and consequently cultural and historical changes in the early Atlantic, which extend over several centuries, can only be correlated with the very abrupt misox fluctuation with difficulty. At this point in time, drier conditions had established themselves in North Africa , and in East Africa there was even more than five centuries of drought . In western Asia, especially in Mesopotamia , the climate had cooled down over three centuries with simultaneous aridification. This is likely to have caused the expansion of irrigation for arable farming in Mesopotamia. Only the better yields provided the basis for the urban civilization that developed there. But it could also have been the reason for climate-related emigration . In Anatolia ( Anatolia hypothesis ) and the Middle East (Mesopotamia), the climate had cooled down during the Misox fluctuation with simultaneous aridification .

Climate and postglacial expansion in the Middle East, with the Misox fluctuation (8.2 kiloyear event with arrow).

See also

literature

  • W. Dansgaard, SJ Johnsen, HB Clausen, D. Dahl-Jensen, NS Gundestrup, CU Hammer, CS Hvidberg, JP Steffensen, AE Sveinbjornsdottir, J. Jouzel and G. Bond: Evidence for general instability of past climate from a 250- kyr ice-core record. Nature, 364, pp. 218-220, 1993
  • PM Grootes et al .: Comparison of oxygen isotope records from GISP2 and GRIP Greenland ice-cores In: Nature 366, pp. 552-554, 1993
  • H. Zoller: Pollen analysis studies on the vegetation history of Insubric Switzerland In: Memoranda of the Swiss Natural Research Society 83, pp. 45–156, 1960
  • H. Zoller, C. Schindler, and H. Röthlisberger: Postglacial glacier positions and climatic fluctuations in the Gotthard massif and the Vorderrhein area. Negotiations of the Natural Research Society in Basel 77, pp. 97–164, 1966
  • H. Zoller: Vegetation in the Stone Age in Switzerland. Article in: Basler Nachrichten v. December 12, 1961

Individual evidence

  1. ↑ cf. RB Alley: The Younger Dryas cold interval as viewed from central Greenland . In: Quaternary Science Reviews . January 2000, doi : 10.1016 / S0277-3791 (99) 00062-1 .
  2. ^ A b Heinrich Zoller: Pollen analysis studies on the history of vegetation in insubric Switzerland. Memoranda of the Swiss Society for Natural Sciences. Vol. 83, 1960, pp. 45-156.
  3. ↑ a b Peter Rasmussen, Mikkel Ulfeldt Hede, Nanna Noe-Nygaard, Annemarie L. Clarke, Rolf D. Vinebrooke: Environmental response to the cold climate event 8200 years ago as recorded at Højby Sø, Denmark. Geological Survey of Denmark and Greenland Bulletin, 15, 2008, pp. 57–60 ( PDF )
  4. ↑ G. Bond et al. : A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates . In: Science . tape 278 (5341) , 1997, pp. 1257-66 .
  5. ^ Zoller, Schindler and Röthlisberger 1966
  6. ↑ Willy Tinner and Brigitta Ammann: How mountain forests react - faster than you think . Chapter 3. ( PDF ( Memento of the original from October 2, 2006 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. ) @1@ 2Template: Webachiv / IABot / www.botany.unibe.ch
  7. ↑ Atle Nesje, Svein Olaf Dahl: The Greenland 8200 cal. Yr BP event detected in loss-on-ignition profiles in Norwegian lacustrine sediment sequences . Journal of Quaternary Science, 16, 2, pp. 155-166, 2001
  8. ↑ Barber, DC et al .: Forcing of the cold event 8,200 years ago by catastrophic drainage of Laurentide Lakes . In: Nature . tape 400 (6742) , 1999, pp. 344-8 .
  9. ↑ T. Kobashi et al. : Precise timing and characterization of abrupt climate change 8200 years ago from air trapped in polar ice . In: Quaternary Science Reviews . tape 26 , 2007, p. 1212-1222 .
  10. ^ Wagner, Friederike et al .: Rapid atmospheric CO2 changes associated with the 8,200-years-BP cooling event . In: Proceedings of the National Academy of Science USA Band 99 (19) , 2002, pp. 12011-4 .
  11. ↑ Hijma, Marc P. and Cohen, Kim M .: Timing and magnitude of the sea-level jump preluding the 8.2 kiloyear event . In: Geology . tape 38 (3) , 2010, p. 275-8 .
  12. ↑ Kendall, Roblyn A. et al: The sea-level fingerprint of the 8.2 ka climate event . In: Geology . tape 36 (5) , 2008, pp. 423-6 .
  13. ^ Bernhard Weninger, Eva Alram-Stern, Eva Bauer, Lee Clare, Uwe Danzeglocke, Olaf Jöris, Claudia Kubatzki, Gary Rollefson, Henrieta Todorova: The Neolithization of Southeast Europe as a Result of the Abrupt Climate Change around 8200 cal BP . In: Detlef Gronenborn (ed.): Climate change and cultural change in Neolithic societies in Central Europe, 6700–2200 BC. Chr. Verlag des Römisch-Germanisches Zentralmuseums, Mainz 2005, ISBN 3-88467-096-4 , p. 75–117 ( online [PDF; 2.2 MB ]).