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Encyclopedia > Younger Dryas
Three temperature records, the GRIP one clearly showing the Younger Dryas event at around 11 kyr BP
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Three temperature records, the GRIP one clearly showing the Younger Dryas event at around 11 kyr BP

The Younger Dryas stadial, named after the alpine / tundra wildflower Dryas octopetala, and also referred to as the Big Freeze [1], was a brief (approximately 1300 ± 70 years [1]) cold climate period following the Bölling/Allerød interstadial at the end of the Pleistocene between approximately 12.7 to 11.5 ky BP [2], and preceding the Preboreal of the early Holocene. In Ireland, the period has been known as the Nahanagan Stadial, while in the UK it has been called the Loch Lomond Stadial. Image File history File links From the Vostok and EPICA (Antarctica) and GRIP (Greenland) ice cores: d-o-18, last 40kyr. ... Image File history File links From the Vostok and EPICA (Antarctica) and GRIP (Greenland) ice cores: d-o-18, last 40kyr. ... A stadial is a period of even-colder temperatures during an ice age. ... The Mountain Avens or White Dryas (Dryas octopetala L.) is a alpine and arctic flower of Eurasia. ... The Allerød period is a part of a temperature oscillation towards the end of the last Ice Age in Europe, where temperatures in the Northern Atlantic region rose from glacial to almost present day level in the Bølling and Allerød periods and returned to glacial levels in... The Pleistocene epoch (pronounced like ply-stow-seen) is part of the geologic timescale. ... The Boreal in paleoclimatology was the first Blytt-Sernander period, pollen zone and chronozone of Holocene north Europe. ... The Holocene epoch is a geological period that extends from the present back about 10,000 radiocarbon years. ...


The Younger Dryas is also a Blytt-Sernander climate period detected from layers in north European bog peat. It is dated approximately 12,900-11,500 BP calibrated, or 11,000-10,000 BP uncalibrated. An Older Dryas stadial had preceded the Allerød, approximately 1000 years before the Younger Dryas; it lasted 300 years [3]. The Blytt-Sernander classification, or sequence, is a series of north European climatic periods or phases based on the study of Danish peat bogs by Axel Blytt (1876) and Rutger Sernander (1908). ... Before Present (BP) years are the units of time (counted backwards to the past) used to report raw radiocarbon ages and dates referenced to the BP scale origin in the year AD 1950. ... The Older Dryas was a cold, dry Blytt-Sernander period and pollen zone of North Europe dated to roughly 14,000-13,600 BP calibrated, 12,000-11,700 uncalibrated. ...

Contents


Abrupt climate change

The Younger Dryas saw a rapid return to glacial conditions in the higher latitudes of the Northern Hemisphere between 12,900 – 11,500 years before present (BP)[2] in sharp contrast to the warming of the preceding interstadial deglaciation. The transitions each occurred over a period of a decade or so [Alley et al., 1993].Thermally fractionated nitrogen and argon isotope data from Greenland ice core GISP2 indicates that the summit of Greenland was ~15 °C colder than today during the Younger Dryas [3]. In the UK, coleopteran (fossil beetle) evidence suggests mean annual temperature dropped to approximately -5 °C [4], and periglacial conditions prevailed in lowland areas, while icefields and glaciers formed in upland areas [5]. Nothing of the size, extent, or rapidity of this period of abrupt climate change has been experienced since [2]. A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... Isotopes are forms of an element whose nuclei have the same atomic number - the number of protons in the nucleus - but different mass numbers because they contain different numbers of neutrons. ... Ice Core sample taken from drill. ... Suborders Adephaga Archostemata Myxophaga Polyphaga See subgroups of the order Coleoptera Beetles are one of the most diverse groups of insects. ... Periglacial refers to places in the edges of glacial areas, normally those related to past ice ages rather than those in the modern era. ... Austrias longest glacier, the Pasterze, winds its 8 km (5 mile) route at the foot of Austrias highest mountain, the Grossglockner A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years Climate change refers to the variation in the Earths global climate or regional climates over time. ...


Was the Younger Dryas global?

Answering this question is hampered by the lack of a precise definition of "younger dryas" in all the records. In western Europe and Greenland, the Younger Dryas is a well-defined synchronous cool period [4]. But cooling in the tropical north atlantic may have preceeded this by a few hundred years; south america shows a less well defined initiation but a sharp termination. The "Antarctic cold reversal" appears to have started a thousand years before the younger dryas, and has no clearly defined start or end; Huybers has argued that there is fair confidence in the abscence of the yonger dryas in Antarctica, New Zealand and parts of oceania. Similarly the Southern Hemisphere cooling known as the Deglaciation Climate Reversal (DCR) began approximately 1kyr before the YD, between 14kya and 11.5 kya as noted in the Sajama ice core. The Andean climate returned to LGM conditions with colder temperatures coupled with higher precipitation (high lake stands in the altiplano). Thompson et al., 2000. Image File history File links As for Image:Epica-vostok-grip-40kyr. ...


Other features seen include:

A forest is an area with a high density of trees (or, historically, a wooded function as carbon dioxide sinks, animal habitats, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the Earths biosphere. ... Scandinavia is a region in Northern Europe named after the Scandinavian Peninsula. ... In physical geography, tundra is an area where the tree growth is hindered by low temperatures and short growing seasons. ... Dryas Categories: Plant stubs | Plants ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... Snow is precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes. ... Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Desert view in Saudi Arabia. ... Asia is the largest and most populous region or continent depending on the definition. ... The Levant Levant is an imprecise geographical term historically referring to a large area in the Middle East south of the Taurus Mountains, bounded by the Mediterranean Sea on the west, and by the northern Arabian Desert and Upper Mesopotamia to the east. ... The Natufian culture existed in the Mediterranean region of the Levant. ... The Huelmo/Mascardi Cold Reversal (HMCR) is the name given to a cooling event in South America between 11,400 and 10,200 14C years BP. This cooling began about 550 years before the Younger Dryas cooling in the Northern Hemisphere, and both periods ended at about the same time. ...

Causes of the Younger Dryas

The prevailing theory holds that the Younger Dryas was caused by a significant reduction or shutdown of the North Atlantic thermohaline circulation in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. The global climate would then have become locked into the new state until freezing removed the fresh water "lid" from the north Atlantic Ocean. This theory does not explain why South America cooled first. The thermohaline circulation is a term for the global density-driven circulation of the oceans. ... A map of the extent of Lake Agassiz Lake Agassiz was an immense lake—bigger than all of the present-day Great Lakes combined—in the center of North America, which was fed by glacial runoff at the end of the last ice age. ... World map showing North America A satellite composite image of North America. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ...


The end of the Younger Dryas

Measurements of oxygen isotopes from the GISP2 ice core suggest the ending of the Younger Dryas took place over just 40 - 50 years in three discrete steps, each lasting five years. Other proxy data, such as dust concentration, and snow accumulation, suggest an even more rapid transition, requiring a ~7 °C warming in just a few years [2],[3],[6],[7], [8]. Ice Core sample taken from drill. ...


The end of the Younger Dryas has been dated to around 9600 BC (11550 calendar years BP, occurring at 10000 radiocarbon years BP, a "radiocarbon plateau") by a variety of methods, with mostly consistent results: Raw radiocarbon measurements are usually reported as years before present (BP). ...

11530±50 BP -- GRIP ice core, Greenland [9]
11530+40-60 BP -- Kråkenes Lake, western Norway. [10]
11570 BP -- Cariaco Basin core, Venezuela [11]
11570 BP -- German oak/pine dendrochronology [12]
11640±280 BP -- GISP2 ice core, Greenland [6]

Frozen Waterfall in the Rhön mountains A natural, 4 tonne, block of ice on a beach in Iceland Ice can refer any of the 14 known solid phases of water. ... Species See List of Quercus species The term oak can be used as part of the common name of any of several hundred species of trees and shrubs in the genus Quercus, and some related genera, notably Cyclobalanopsis and Lithocarpus. ... Species About 115. ... Pinus taeda Cross section showing annual rings, Cheraw, South Carolina Pine stump showing growth rings Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree ring patterns. ...

The Younger Dryas and the beginning of agriculture

The Younger Dryas is often linked to the adoption of agriculture in Southwest Asia [14]. It is argued that the cold and dry Younger Dryas lowered the carrying capacity of the area and forced the sedentary Early Natufian population into a more mobile subsistance pattern. Further climatic deterioration is thought to have brought about cereal cultivation. While there exists relative consensus regarding the role of the Younger-Dryas in the changing subsistance patterns during the Natufian, its connection to the beginning of agriculture at the end of the period is still being debated [15]. Southwest Asia (PDF) Southwest Asia (often confused with the Middle East) is the southwestern portion of Asia. ... In ecology, carrying capacity is the measure of habitat to indefinitely sustain a population at a particular density. ... The Natufian culture existed in the Mediterranean region of the Levant. ... The Natufian culture existed in the Mediterranean region of the Levant. ...


References

  1. Berger, W.H. (1990), The Younger Dryas cold spell – a quest for causes. Palaeogeography, Palaeoclimatology, Palaeoecology (Global and Planetary Change Section) 89, 219-237.
  2. Alley, R.B. (2000), The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19, 213-226.
  3. Alley et al. (1993), Abrupt accumulation increase at the Younger Dryas termination in the GISP2 ice core, Nature, 362, 527-529.
  4. Severinghaus, J.P., et al. (1998), Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice. Nature 391, 141-146.
  5. Atkinson, T.C., et al. (1987), Seasonal temperatures in Britain during the past 22,000 years, reconstructed using beetle remains. Nature 325, 587-592.
  6. Sissons, J.B. (1979), The Loch Lomond stadial in the British Isles. Nature 280, 199-203.
  7. Alley, R.B., et al. (1993), Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event. Nature 362, 527-529.
  8. Dansgaard, W., et al. (1989), The abrupt termination of the Younger Dryas climate event. Nature 339, 532-534.
  9. Taylor, K.C., et al. (1997), The Holocene-Younger Dryas transition recorded at Summit, Greenland. Science 278, 825-827.
  10. Spurk, M., et al. (1998), Revisions and extension of the Hohenheim oak and pine chronologies: New evidence about the timing of the Younger Dryas/Preboreal transition, Radiocarbon 40, 1107-1116.
  11. Gulliksen, S., et al. (1998), A calendar age estimate of the Younger Dryas-Holocene boundary at Krakenes, western Norway, Holocene 8, 3, 249-259.
  12. Hugheus radiocarbon and climate shifts during the last deglaciation, Science 290, 5498, 1951-1954. -- http://www.ngdc.noaa.gov/paleo/pubs/hughen2000/hughen2000.html
  13. Friedrich, M., et al. (1999), Paleo-environment and radiocarbon calibration as derived from Lateglacial/Early Holocene tree-ring chronologies, Quaternary International 61, 27-39. -- http://www.pages.unibe.ch/products/scientific_foci/ql_dfg/friedrichabstract.html
  14. Bar-Yosef, O. and A. Belfer-Cohen (2002), Facing environmental crisis. Societal and cultural changes at the transition from the Younger Dryas to the Holocene in the Levant. In: The Dawn of Farming in the Near East. Edited by R.T.J. Cappers and S. Bottema, pp. 55-66. Studies in Early Near Eastern Production, Subsistence and Environment 6. Berlin: Ex oriente. --
  15. Munro, N. D., (2003), Small game, the younger dryas, and the transition to agriculture in the southern levant, Mitteilungen der Gesellschaft für Urgeschichte 12, 47–64. -- PDF

See also

There have been four major periods of glaciation in the Earths past. ... // Earlier Events See Timeline of evolution See Geologic time scale Pleistocene Younger Dryas stadial Holocene 10th millennium BC Circa 10,000 BC — North America: Dire Wolf, Smilodon, Giant beaver, Ground sloth, Mammoth, and American lion all become extinct. ...

External links


  Results from FactBites:
 
Younger Dryas - Wikipedia, the free encyclopedia (1121 words)
The Younger Dryas saw a rapid return to glacial conditions in the higher latitudes of the Northern Hemisphere between 12,900 – 11,500 years before present (BP)[2] in sharp contrast to the warming of the preceding interstadial deglaciation.
In western Europe and Greenland, the Younger Dryas is a well-defined synchronous cool period [4].
The prevailing theory holds that the Younger Dryas was caused by a significant reduction or shutdown of the North Atlantic thermohaline circulation in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America.
Younger Dryas - definition of Younger Dryas in Encyclopedia (635 words)
The Younger Dryas stadial, named after the alpine / tundra wildflower Dryas octopetala, and also referred to as the Big Freeze [1], was a brief cold climate period following the Bölling/Allerød interstadial at the end of the Pleistocene, and preceding the Preboreal of the early Holocene.
The Younger Dryas saw a rapid return to glacial conditions in the higher latitudes of the Northern Hemisphere between 12,900 – 11,500 years before present (BP)[2]in sharp contrast to the warming of the preceding interstadial deglaciation.
The prevailing theory holds that the Younger Dryas was caused by a significant reduction or shutdown of the North Atlantic thermohaline circulation in response to a sudden influx of fresh water from deglaciation in North America.
  More results at FactBites »

 
 

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