Glacial period

For longer glacial periods, see ice age.

For film, see Ice Age (2002 film).

A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate between glacial periods. The Last Glacial Period ended about 15,000 years ago.^[1] The Holocene is the current interglacial. A time with no glaciers on Earth is considered a greenhouse climate state.^[2][3][4]

Quaternary Period

Main articles: Quaternary glaciation and timeline of glaciation

Glacial and interglacial cycles as represented by atmospheric CO₂, measured from ice core samples going back 800,000 years. The stage names are part of the North American and the European Alpine subdivisions. The correlation between both subdivisions is tentative.

Within the Quaternary, which started about 2.6 million years before present, there have been a number of glacials and interglacials.^[5] At least eight glacial cycles have occurred in the last 740,000 years alone.^[6]

Penultimate Glacial Period

Main article: Penultimate Glacial Period

The Penultimate Glacial Period (PGP) is the glacial period that occurred before the Last Glacial Period. It began about 194,000 years ago and ended 135,000 years ago, with the beginning of the Eemian interglacial.^[7]

Last Glacial Period

Main article: Last Glacial Period

The last glacial period was the most recent glacial period within the Quaternary glaciation at the end of the Pleistocene, and began about 110,000 years ago and ended about 11,700 years ago.^[1] The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere and have different names, depending on their geographic distributions: Wisconsin (in North America), Devensian (in Great Britain), Midlandian (in Ireland), Würm (in the Alps), Weichsel (in northern Central Europe), Dali (in East China), Beiye (in North China), Taibai (in Shaanxi) Luoji Shan (in southwest Sichuan), Zagunao (in northwest Sichuan), Tianchi (in the Tian Shan) Jomolungma (in the Himalayas), and Llanquihue (in Chile). The glacial advance reached the Last Glacial Maximum about 26,500 BP. In Europe, the ice sheet reached Northern Germany. Over the last 650,000 years, there have been on average seven cycles of glacial advance and retreat.

Next glacial period

See also: Milankovitch cycles

Since orbital variations are predictable,^[8] computer models that relate orbital variations to climate can predict future climate possibilities. Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years.^[9] The amount of heat trapping (greenhouse) gases being emitted into the Earth's oceans and its atmosphere may delay the next glacial period by an additional 50,000 years.^[10][11]

References

1. J. Severinghaus; E. Brook (1999). "Abrupt Climate Change at the End of the Last Glacial Period Inferred from Trapped Air in Polar Ice". Science. 286 (5441): 930–4. doi:10.1126/science.286.5441.930. PMID 10542141.
2. Bralower, T.J.; Premoli Silva, I.; Malone, M.J. (2006). Bralower, T.J; Premoli Silva, I; Malone, M.J (eds.). "Leg 198 Synthesis : A Remarkable 120-m.y. Record of Climate and Oceanography from Shatsky Rise, Northwest Pacific Ocean". Proceedings of the Ocean Drilling Program. Initial Reports. Proceedings of the Ocean Drilling Program. 198. Proceedings of the Ocean drilling program.: 47. doi:10.2973/odp.proc.ir.198.2002. ISSN 1096-2158. Retrieved April 9, 2014.
3. Christopher M. Fedo; Grant M. Young; H. Wayne Nesbitt (1997). "Paleoclimatic control on the composition of the Paleoproterozoic Serpent Formation, Huronian Supergroup, Canada: a greenhouse to icehouse transition". Precambrian Research. 86 (3–4). Elsevier: 201. Bibcode:1997PreR...86..201F. doi:10.1016/S0301-9268(97)00049-1.
4. Miriam E. Katz; Kenneth G. Miller; James D. Wright; Bridget S. Wade; James V. Browning; Benjamin S. Cramer; Yair Rosenthal (2008). "Stepwise transition from the Eocene greenhouse to the Oligocene icehouse". Nature Geoscience. 1 (5). Nature: 329. Bibcode:2008NatGe...1..329K. doi:10.1038/ngeo179.
5. Gibbard, P.; van Kolfschoten, T. (2004). "Chapter 22: The Pleistocene and Holocene Epochs" (PDF). In Gradstein, F. M.; Ogg, James G.; Smith, A. Gilbert (eds.). A Geologic Time Scale 2004. Cambridge: Cambridge University Press. ISBN 978-0-521-78142-8.
6. Augustin, Laurent; et al. (2004). "Eight glacial cycles from an Antarctic ice core". Nature. 429 (6992): 623–8. Bibcode:2004Natur.429..623A. doi:10.1038/nature02599. PMID 15190344.
7. Nehme, Carole; Verheyden, Sophie; Breitenbach, Sebastian F.M.; Gillikin, David P.; et al. (July 2018). "Climate Dynamics During the Penultimate Glacial Period Recorded in a Speleothem from Kanaan Cave, Lebanon (central Levant)" (PDF). Quaternary Research. 90 (1): 10–25. Bibcode:2018QuRes..90...10N. doi:10.1017/qua.2018.18. S2CID 134924228.
8. F. Varadi; B. Runnegar; M. Ghil (2003). "Successive Refinements in Long-Term Integrations of Planetary Orbits". The Astrophysical Journal. 592 (1): 620–630. Bibcode:2003ApJ...592..620V. doi:10.1086/375560.
9. Berger A, Loutre MF (2002). "Climate: An exceptionally long interglacial ahead?". Science. 297 (5585): 1287–8. doi:10.1126/science.1076120. PMID 12193773. S2CID 128923481.
10. Tyrrell, Toby (16 November 2007). "Calcium Carbonate Cycling in Future Oceans and its Influence on Future Climates". Journal of Plankton Research. 30 (2): 141–156. doi:10.1093/plankt/fbm105.
11. Ganopolski, A.; Winkelmann, R.; Schellnhuber, H. J. (14 January 2016). "Critical Insolation–CO2 Relation for Diagnosing Past and Future Glacial Inception". Nature. 529 (7585): 200–203. Bibcode:2016Natur.529..200G. doi:10.1038/nature16494. PMID 26762457. S2CID 4466220.

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