Piora Oscillation

The two are also referred to as Piora oscillation Piora fluctuations I and II indicate two short successive Holocene temperature reductions in Central Europe, which are assumed to be -2 to 2.5 ° C. The times move depending on the source 4200-3100 BC

Definition

The two Piora fluctuations were detected by palynological studies on the lakes and marshes of Lake Cadagno in Piora Valley, Canton Ticino for the territory of the Western Alps. In the area of the Tyrolean Ötztal in the Eastern Alps will correspond approximately to the two Rotmoos fluctuations. The death of the known as the " Iceman " Iceman on the Hauslabjoch took place towards the end of the second glacier thrust around 5100 years ago ( 4500 radiocarbon years).

Temporal classification

After the end of the Würm Ice Age began about 11,700 years ago, a warm period, the Holocene. With the first warm climate most of Central Europe and in North America the tundra vegetation of glacial increasingly a forest cover, first by birch and pine, whose pollen were preserved in the sediments of lakes and bogs and can be detected by pollen analysis. In the Atlantic period, the climatic optimum of the Holocene, the tree line in the Alps was 200 to 300 meters higher than today. The boreal forest belt was further north in Siberia and North America up to 300 km.

The Piora fluctuations correspond to a number of the world's proven climate events towards the end of the Atlantic period and the beginning of the Sub-boreal, can be so spoken of a global cooling. From the studies of the Greenland inland ice from the GRIP ice core also a cooling of about 3,350 cal BC ( Magny and Haas 2004) is shown.

Piora variation I

The Piora variation I, known in English as designated 5.9 kilo year event, part of which forms the Bond events ( Bond event 4 ) and is the variation I Rotmoos identical. It situates itself in time at the end of the Atlantic in the period 4100-3700 BC and narrower according Holzhauser ( 2009) between 3900-3780 BC They ended the Neolithic Subpluvial and brought his continuing desiccation of the Sahara in motion. With it, the migration of the major river valleys translated ( Nile, etc.) towards a whose consequence was the appearance of the first complex, highly organized states in the 4th millennium BC.

As was the case the previous Misox variation showed the southern hemisphere during the Piora variation I negative temperature anomalies. The ratios in the northern hemisphere were less clear - the interior of North America was cold due to the Laurentide ice sheet remaining, whereas in Scandinavia prevailed positive anomalies. In Europe, according to Alverson (2003) have ruled even moderate to mild temperatures. In China, the Piora fluctuation can be detected in the lake sediments of I Erhai Lake as a cooling event.

Piora variation II

The Piora variation II is identical to the Rotmoos variation II. It took place at the beginning of the Sub-boreal in the period 3500-3000 BC ( to 3110 BC after Holzhauser ). In the Swiss Alps it is formed as glaciers high level, which occupied the level of 1850.

Causes

The exact causes for the Piora fluctuations are still being debated. It is a combination of factors suspected: changes in solar radiation due to another earth's orbit ( orbital forcing ), changes in ocean currents or an altered solar activity. Main cause of Piora fluctuations may have been a significant reduction in solar activity. The reduced sunlight had possibly induced with the help of the ENSO circulation in the North Atlantic region Bond events.

Follow

Global impacts of climate fluctuations were drought in many regions of the world that had the growth of the steppe areas and the deserts result. The tundra widened due to the increase of the area of the permafrost back out towards the south. In the high mountains has resulted in increased rainfall and an advance of the glacier.

As a result of Piora fluctuations occurred in the Neolithic cultures of Central Europe, numerous changes. The man's treasure from Hauslabjoch ( towards the end of the Piora variation II) stimulated numerous studies on climate and settlement history of the Alps. A change in the species composition of plants is accompanied by a change in the fire land clearing and settlement horizons this time. To 5320 BP, the level of Lake Constance began to rise rapidly, which resulted in the dating by dendrochronology and radiocarbon dating method. Early settlements of people on the lake shore had to be abandoned. The areas for the transhumance and Serviced were severely restricted. The increasing aridization the Sahara led possibly to the fact that trained in the Nile valley irrigated crops, which eventually introduced to Ancient Egypt.

Controversy remains to what extent the Asian monsoon at that time was weakened.