Since 1916 and the onset and later refinement of pollen analytical techniques and a steadily growing number of pollen diagrams, palynologists have concluded that the Younger Dryas represented a distinct period of vegetational change in large parts of Europe during which warmer climate vegetation was replaced by that of a generally cold climate, a glacial plant succession that often contained Dryas octopetala.
This drastic change in vegetation is typically interpreted to be an effect of a sudden decrease in (annual) temperature, unfavorable for the previously rapidly northward-spreading forest vegetation.
In the Greenland Summit ice core chronology, the Younger Dryas corresponds to Greenland Stadial 1 (GS-1).
They argue that Younger Dryas events might be an intrinsic feature of deglaciations that occur at the end of glacial periods.The presence of a distinct cold period at the end of the Late Glacial interval has been known for a long time. Slyrs bavarian single malt pedro ximenez Paleobotanical and lithostratigraphic studies of Swedish and Danish bog and lake sites, e.g.The Oldest Dryas occurred approximately 1,770 calendar years before the Younger Dryas and lasted about 400 calendar years.According to the GISP2 ice core from Greenland, the Oldest Dryas occurred between about 15,070 and 14,670 calendar years BP.
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Both of these cold periods are comparable in duration and intensity with the Older Dyras and began and ended quite abruptly.These cold periods have been recognized in sequence and relative magnitude in paleoclimatic records from Greenland ice cores, European lacustrine sediments, Atlantic Ocean sediments, and the Cariaco Basin, Venezuela. Temperature-sensitive lipids, long chain alkenones, found in lake and marine sediments are well-regarded as a powerful paleothermometer for the quantitative reconstruction of past continental climates.Other proxy data, such as dust concentration, and snow accumulation, suggest an even more rapid transition, requiring about a 7 °C (13 °F) warming in just a few years. chat dk gratis Fredericia The end of the Younger Dryas has been dated to around 11550 years ago, occurring at 10000 years ago (uncalibrated radiocarbon year), a "radiocarbon plateau" by a variety of methods, with mostly consistent results: Although the start of the Younger Dryas is regarded to be synchronous across the North Atlantic region, recent research concluded that the start of the Younger Dryas might be time-trangressive even within this region.This cooling not only favored the expansion of cold-tolerant, light-demanding plants and associated steppe fauna, it also led to regional glacial advances in Scandinavia and a lowering of the regional snow line.
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The change to glacial conditions at the onset of the younger Dryas in the higher latitudes of the Northern Hemisphere between 12,900–11,500 BP in calendar years has been argued to have been quite abrupt.The Older Dryas, in turn, is preceded by another warmer stage, the Bølling oscillation that separates it from a third and even older stadial.This stadial is often, but not always, known as the Oldest Dryas.The application of alkenone paleothermometers to high-resolution paleotemperature reconstructions of older glacial terminations have found that very similar Younger Dryas-like paleoclimatic oscillations occurred during Terminations II and IV.If so, then the Younger Dryas is not the unique paleoclimatic event, in terms of size, extent, and rapidity, as it has been often regarded to be.