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Younger Dryas

Younger Dryas
Significant cooling in the Northern Hemisphere took place during the Younger Dryas, but there was also warming in the Southern Hemisphere. Precipitation had substantially decreased (brown) or increased (green) in many areas across the globe. Altogether, this indicates large changes in thermohaline circulation as the cause[1]
Etymology
Alternate spelling(s)YD
Synonym(s)Loch Lomond Stadial
Nahanagan Stadial
Usage information
Celestial bodyEarth
Definition
Chronological unitChron
Stratigraphic unitChronozone
Atmospheric and climatic data
Mean atmospheric CO2 contentc. 240 ppm
(0.9 times pre-industrial)
Mean surface temperaturec. 10.5 °C
(3 °C below pre-industrial)

The Younger Dryas (YD) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP).[2] It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the North Atlantic Ocean cooled and annual air temperatures decreased by ~3 °C (5.4 °F) over North America, 2–6 °C (3.6–10.8 °F) in Europe and up to 10 °C (18 °F) in Greenland, in a manner of decades.[3] Cooling in Greenland was particularly rapid, taking place over just 3 years or less.[1][4] At the same time, the Southern Hemisphere had experienced warming.[3][5] This period ended as rapidly as it began, with dramatic warming over ~50 years, which had transitioned the Earth from the glacial Pleistocene epoch into the current Holocene.[1]

The Younger Dryas onset was not fully synchronized; in the tropics, the cooling was spread out over several centuries, and the same was true of the early-Holocene warming.[1] Even in the Northern Hemisphere, temperature change was highly seasonal, with much colder winters, cooler springs, yet no change or even slight warming during the summer.[6][7] Substantial changes in precipitation have also taken place, with cooler areas experiencing substantially lower rainfall, while warmer areas received more of it.[3] Northern Hemisphere growing season length had declined.[7] Land ice cover experienced little net change,[8] but sea ice extent had increased, contributing to ice–albedo feedback.[3] This increase in albedo was the main reason for net global cooling of 0.6 °C (1.1 °F).[3]

During the preceding period, the Bølling–Allerød Interstadial, rapid warming in the Northern Hemisphere[9]: 677  was offset by the equivalent cooling in the Southern Hemipshere.[10][8] This "polar seesaw" pattern is consistent with changes in thermohaline circulation (particularly the Atlantic meridional overturning circulation or AMOC), which greatly affects how much heat is able to go from the Southern Hemisphere to the North. Southern Hemisphere cools and the Northern Hemisphere warms when the AMOC is strong, and the opposite happens when it is weak.[10] The scientific consensus is that severe AMOC weakening explains the climatic effects of the Younger Dryas.[11]: 1148  It also explains why the Holocene warming had proceeded so rapidly once the AMOC change was no longer counteracting the increase in carbon dioxide levels.[8]

AMOC weakening causing polar seesaw effects is also consistent with the accepted explanation for Dansgaard–Oeschger events, with YD likely to have been the last and the strongest of these events.[12] However, is some debate over what caused the AMOC to become so weak in the first place. The hypothesis historically most supported by scientists was the interruption from an influx of fresh, cold water from North America's Lake Agassiz into the Atlantic Ocean.[13] While there is evidence of meltwater travelling via Mackenzie River,[14] this hypothesis may be not be consistent with the lack of sea level rise during this period,[15] so other theories have also emerged.[16] An extraterrestrial impact into the Laurentide ice sheet (where it would have left no impact crater) was proposed as an explanation, but this hypothesis has numerous issues and no support from mainstream science.[17][18] A volcanic eruption as an initial trigger for cooling and sea ice growth has been proposed more recently,[19] and the presence of anomalously high levels of volcanism immediately preceding the onset of the Younger Dryas has been confirmed in both ice cores[20] and cave deposits.[21]

  1. ^ a b c d Partin, J.W.; Quinn, T.M.; Shen, C.-C.; Okumura, Y.; Cardenas, M.B.; Siringan, F.P.; Banner, J.L.; Lin, K.; Hu, H.-M.; Taylor, F.W. (2 September 2015). "Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics". Nature Communications. 6: 8061. Bibcode:2015NatCo...6.8061P. doi:10.1038/ncomms9061. PMC 4569703. PMID 26329911.
  2. ^ Rasmussen, S. O.; Andersen, K. K.; Svensson, A. M.; Steffensen, J. P.; Vinther, B. M.; Clausen, H. B.; Siggaard-Andersen, M.-L.; Johnsen, S. J.; Larsen, L. B.; Dahl-Jensen, D.; Bigler, M. (2006). "A new Greenland ice core chronology for the last glacial termination" (PDF). Journal of Geophysical Research. 111 (D6): D06102. Bibcode:2006JGRD..111.6102R. doi:10.1029/2005JD006079. ISSN 0148-0227.
  3. ^ a b c d e Carlson, A. E. (2013). "The Younger Dryas Climate Event" (PDF). Encyclopedia of Quaternary Science. Vol. 3. Elsevier. pp. 126–134. Archived from the original (PDF) on 11 March 2020.
  4. ^ Choi, Charles Q. (2 December 2009). "Big freeze: Earth could plunge into sudden ice age". Live Science. Retrieved 2 December 2009.
  5. ^ Clement, Amy C.; Peterson, Larry C. (3 October 2008). "Mechanisms of abrupt climate change of the last glacial period". Reviews of Geophysics. 46 (4): 1–39. Bibcode:2008RvGeo..46.4002C. doi:10.1029/2006RG000204. S2CID 7828663.
  6. ^ Cite error: The named reference Buizert2014 was invoked but never defined (see the help page).
  7. ^ a b Schenk, Frederik; Väliranta, Minna; Muschitiello, Francesco; Tarasov, Lev; Heikkilä, Maija; Björck, Svante; Brandefelt, Jenny; Johansson, Arne V.; Näslund, Jens-Ove; Wohlfarth, Barbara (24 April 2018). "Warm summers during the Younger Dryas cold reversal". Nature Communications. 9. doi:10.1038/s41467-018-04071-5.
  8. ^ a b c Cite error: The named reference Shakun2012 was invoked but never defined (see the help page).
  9. ^ Canadell, J.G.; Monteiro, P. M. S.; Costa, M. H.; Cotrim da Cunha, L.; Cox, P. M.; Eliseev, A. V.; Henson, S.; Ishii, M.; Jaccard, S.; Koven, C.; Lohila, A.; Patra, P. K.; Piao, S.; Rogelj, J.; Syampungani, S.; Zaehle, S.; Zickfeld, K. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Report). Cambridge, UK and New York, NY, US: Cambridge University Press. pp. 673–816. doi:10.1017/9781009157896.007.
  10. ^ a b Obase, Takashi; Abe-Ouchi, Ayako; Saito, Fuyuki (25 November 2021). "Abrupt climate changes in the last two deglaciations simulated with different Northern ice sheet discharge and insolation". Scientific Reports. 11 (1): 22359. Bibcode:2021NatSR..1122359O. doi:10.1038/s41598-021-01651-2. PMC 8616927. PMID 34824287.
  11. ^ Douville, H.; Raghavan, K.; Renwick, J.; Allan, R. P.; Arias, P. A.; Barlow, M.; Cerezo-Mota, R.; Cherchi, A.; Gan, T.Y.; Gergis, J.; Jiang, D.; Khan, A.; Pokam Mba, W.; Rosenfeld, D.; Tierney, J.; Zolina, O. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 8: Water Cycle Changes" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK and New York, NY, US: Cambridge University Press: 1055–1210. doi:10.1017/9781009157896.010.
  12. ^ Cite error: The named reference Nye2014 was invoked but never defined (see the help page).
  13. ^ Meissner, K.J. (2007). "Younger Dryas: A data to model comparison to constrain the strength of the overturning circulation". Geophysical Research Letters. 34 (21): L21705. Bibcode:2007GeoRL..3421705M. doi:10.1029/2007GL031304.
  14. ^ Cite error: The named reference Süfke2022 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Abdul2016 was invoked but never defined (see the help page).
  16. ^ Broecker, Wallace S.; Denton, George H.; Edwards, R. Lawrence; Cheng, Hai; Alley, Richard B.; Putnam, Aaron E. (2010). "Putting the Younger Dryas cold event into context". Quaternary Science Reviews. 29 (9): 1078–1081. Bibcode:2010QSRv...29.1078B. doi:10.1016/j.quascirev.2010.02.019. ISSN 0277-3791.
  17. ^ Cite error: The named reference Gramling2021 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Holliday2023 was invoked but never defined (see the help page).
  19. ^ Baldini, James U. L.; Brown, Richard J.; Mawdsley, Natasha (4 July 2018). "Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly". Climate of the Past. 14 (7): 969–990. Bibcode:2018CliPa..14..969B. doi:10.5194/cp-14-969-2018. ISSN 1814-9324.
  20. ^ Abbott, P.M.; Niemeier, U.; Timmreck, C.; Riede, F.; McConnell, J.R.; Severi, M.; Fischer, H.; Svensson, A.; Toohey, M.; Reinig, F.; Sigl, M. (December 2021). "Volcanic climate forcing preceding the inception of the Younger Dryas: Implications for tracing the Laacher See eruption". Quaternary Science Reviews. 274: 107260. Bibcode:2021QSRv..27407260A. doi:10.1016/j.quascirev.2021.107260.
  21. ^ Sun, N.; Brandon, A. D.; Forman, S. L.; Waters, M. R.; Befus, K. S. (31 July 2020). "Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P." Science Advances. 6 (31): eaax8587. Bibcode:2020SciA....6.8587S. doi:10.1126/sciadv.aax8587. ISSN 2375-2548. PMC 7399481. PMID 32789166.

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