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== Voce in lavorazione ==
en: Mid-Pleistocene Transition = Transizione del Pleistocene medio (2457)
The '''Mid-Pleistocene Transition''' ('''MPT'''),<ref name="Willeit">{{cite journal|title=Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal | Science Advances|journal=Science Advances|date=April 2019|volume=5|issue=4|pages=eaav7337|doi=10.1126/sciadv.aav7337|last1=Brovkin|first1=V.|last2=Calov|first2=R.|last3=Ganopolski|first3=A.|last4=Willeit|first4=M.|pmid=30949580|pmc=6447376}}</ref> also known as the '''Mid-Pleistocene Revolution''' ('''MPR'''),<ref>[https://sp.lyellcollection.org/content/247/1/19 Mark A. Maslin and Andy J. Ridgwell (2005): Mid-Pleistocene revolution and the ‘eccentricity myth’, Geological Society, London, Special Publications, 247, 19-34, 1 January 2005]</ref> is a fundamental change in the behaviour of [[glacial cycle]]s during the [[Quaternary]] glaciations. The transition happened approximately 1.25–0.7 million years ago, in the [[Pleistocene]] epoch.<ref name="Clark">{{cite journal|title=The middle Pleistocene transition: characteristics, mechanisms, and implications for long-term changes in atmospheric pCO2|last1=Clark|first1=Peter U|last2=Archer|first2=David|last3=Pollard|first3=David|last4=Blum|first4=Joel D|last5=Rial|first5=Jose A|last6=Brovkin|first6=Victor|last7=Mix|first7=Alan C|last8=Pisias|first8=Nicklas G|last9=Roy|first9=Martin|journal=Quaternary Science Reviews|volume=25|issue=23–24|pages=3150–3184|year=2006|publisher=Elsevier|url=http://www.geo.oregonstate.edu/files/geo/Clark%20etal.-2006-QSR.pdf|doi=10.1016/j.quascirev.2006.07.008|bibcode=2006QSRv...25.3150C}}</ref> Before the MPT, the glacial cycles were dominated by a 41,000 year periodicity with low-amplitude, thin ice sheets and a linear relationship to the [[Milankovitch cycles|Milankovitch forcing]] from axial tilt. After the MPT there have been strongly asymmetric cycles with long-duration cooling of the climate and build-up of thick ice sheets, followed by a fast change from extreme glacial conditions to a warm interglacial. The cycle lengths have varied, with an average length of approximately 100,000 years.<ref name="Willeit"/><ref name="Clark"/>
The Mid-Pleistocene Transition was long a problem to explain, as described in the article ''[[100,000-year problem]]''. The MPT can now be reproduced by numerical models that assume a decreasing level of atmospheric [[carbon dioxide]], a high [[Climate sensitivity|sensitivity]] to this decrease, and gradual removal of [[regolith]]s from northern hemisphere areas subject to glacial processes during the Quaternary.<ref name="Willeit"/> The reduction in {{CO2}} may be related to changes in volcanic outgassing, burial of ocean sediments, carbonate weathering or iron fertilization of oceans from glacially induced dust.<ref name="Chalk">[https://www.pnas.org/content/114/50/13114 Chalk et al. (2017): Causes of ice age intensification across the Mid-Pleistocene Transition, PNAS December 12, 2017 114 (50) 13114-13119]</ref>
Regoliths are believed to affect glaciation because ice with its base on regolith at the pressure melting point will slide with relative ease, which limits the thickness of the ice sheet. Before the Quaternary, northern North America and northern Eurasia are believed to have been covered by thick layers of regoliths, which have been worn away over large areas by subsequent glaciations.<ref name="Clark" /> Later glaciations were increasingly based on core areas, with thick ice sheets strongly coupled to bare bedrock.<ref name="Clark" /><ref name="Chalk" /><ref name="Willeit" />
However, a 2020 study concluded that ice age terminations might have been influenced by [[Axial tilt|obliquity]] since the Mid-Pleistocene Transition, which caused stronger summers in the [[Northern Hemisphere]].<ref>{{cite news<!--|authors=Petra Bajo, Russell N. Drysdale, Jon D. Woodhead, John C. Hellstrom, David Hodell, Patrizia Ferretti, Antje H. L. Voelker, Giovanni Zanchetta, Teresa Rodrigues, Eric Wolff, Jonathan Tyler, Silvia Frisia, Christoph Spötl, Anthony E. Fallick-->|author=Petra Bajo|display-authors=etal|title=Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition|publisher=Science|year=2020|volume=367|issue=6483|pages=1235–1239|doi=10.1126/science.aaw1114}}</ref>
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{{Portale|geografia
[[Categoria:
[[Categoria:Glaciologia]]
[[Categoria:Pleistocene]]
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