Mid-Pleistocene Transition
The Mid-Pleistocene Transition (MPT), also known as the Mid-Pleistocene Revolution (MPR),
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 sensitivity to this decrease, and gradual removal of regoliths from northern hemisphere areas subject to glacial processes during the Quaternary.[2] The reduction in CO2 may be related to changes in volcanic outgassing, the burial of ocean sediments, carbonate weathering or iron fertilization of oceans from glacially induced dust.[8]
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. Later glaciations were increasingly based on core areas, with thick ice sheets strongly coupled to bare bedrock.[4]
It has also been proposed that an enlarged deep ocean carbon inventory in the Atlantic Ocean played a role in the increase in amplitude of glacial-interglacial cycles because this increase in carbon storage capacity is coincident with the transition from 41-kyr to 100-kyr glacial-interglacial cycles.[9]
However, a 2020 study concluded that ice age terminations might have been influenced by obliquity since the Mid-Pleistocene Transition, which caused stronger summers in the Northern Hemisphere.[10] Evidence suggests that fluctuations in the volume of the West Antarctic Ice Sheet continued to be governed dominantly by fluctuations in obliquity until about 400,000 years ago.[11]
In Australia the MPT resulted in the formation of the dunes of Fraser Island and the Cooloola Sand Mass. The increasing amplitude of sea level variations led to increased redistribution of sediments stored on the seafloor across the continental shelf. The development of Fraser Island indirectly led to the formation of the Great Barrier Reef by drastically decreasing the flow of sediment to the area of continental shelf north of Fraser Island, a necessary precondition for the growth of coral reefs on such an enormous scale as found in the Great Barrier Reef.[12]
See also
- 100,000-year problem
- Chibanian
- Milankovitch cycles
- Paleoclimatology
- Paleothermometer
- Timeline of glaciation
References
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- ^ doi:10.1016/j.quascirev.2006.07.008. Archived from the original(PDF) on 31 August 2017. Retrieved 5 April 2019.
- ^ S2CID 254484999. Retrieved 19 April 2023.
- S2CID 247844873. Retrieved 20 January 2023.
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- ^ "Chalk et al. (2017): Causes of ice age intensification across the Mid-Pleistocene Transition, PNAS December 12, 2017 114 (50) 13114-13119".
- S2CID 133953916. Retrieved 20 December 2023.
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- S2CID 254326281. Retrieved 19 April 2023.
- S2CID 253538370.