Penultimate Glacial Period

Short description: Glacial age that occurred before the Last Glacial Period

Diagram of glacial cycles, with the Penultimate Glacial Period labelled as MIS 6.

The Penultimate Glacial Period (PGP) is the glacial period that occurred before the Last Glacial Period. The penultimate glacial period is officially unnamed just like the Last Glacial Period. The PGP lasted from ~194,000 years ago at the end of the Marine Isotope Stage 7 (MIS 7) interglacial, to ~135,000 years ago, and was succeeded by the Last Interglacial.[1] The PGP also occurred during Marine Isotope Stage 6 (MIS 6).[2] At the glacial ages' height, it is known to be the most extensive expansion of glaciers in the last 400,000 years over Eurasia, and could be the second or third coolest glacial period over the last 1,000,000 years, as shown by ice cores.[3] Due to this, the global sea level dropped to between 92 and 150 metres below modern-day global mean sea level.[1] The penultimate glacial period expanded ice sheets and shifted temperature zones worldwide, which had a variety of effects on the world's environment, and the organisms that lived in it.[4] At its height, the penultimate glacial period was a more severe glaciation than the Last Glacial Maximum.[2] The PGP covers the last period of the Saalian glaciation in Europe, called the Wolstonian Stage in Britain, and is equivalent to the Illinoian in North America.

## Contents

* 1 Cause
* 2 Effects
* 2.1 Europe
* 2.2 Asia
* 2.3 North America
* 2.4 South America
* 2.5 Africa
* 2.6 Antarctica
* 3 References

## Cause

Much like the last glacial period, the penultimate glacial period was caused by a great orbital eccentricity of Earth.[5] This eccentricity causes greater seasonal impacts than normal because it limits the amount of sunlight that reaches the earth's surface, lowering the temperature.[6] Due to this, northern insolation (the amount of sunlight that reaches the surface) is reduced, meaning that during summer, less heat is exposed to the snows of the winter, which don't completely melt.[1] This buildup of ice and snow over thousands of years eventually leads to residual ice sheets, which would also reflect light away from the earth, further cooling the earth.[7] A decrease in greenhouse gas concentrations such as CO2, are a result of the expanded ice sheets.[5] This is because as the Earth cooled, and ice sheets expanded, the ocean waters became colder, which then could absorb more CO2 from the atmosphere.[8] These factors all feedback into each other: as the ice sheets extended, more CO2 was absorbed, and more light was reflected off the ice sheets, furthermore expanding the ice sheets, this self-reinforcing cooling setting the world into a glacial period.[8]

## Effects

The Penultimate Glacial Maximum around 140,000 years ago was the most extensive glaciation in Eurasia in the last 400,000 years. It was colder in high latitudes and warmer in the tropics than the Last Glacial Maximum.[1]

### Europe

In northern Europe, the biggest expansion of glaciation of the last 400,000 years covered the northern region in a thick ice sheet, which caused a drastic reduction of vegetation.[8] In the Mediterranean, polar winds from the now extended ice sheets brought cooler and wetter conditions that caused a significant reduction in large vegetation such as trees.[5] Pollen sequences found from MIS 6 indicated that early in the glacial period, tree abundance fluctuated heavily.[9]

Later in the glacial period, extreme conditions were followed by a mainly treeless landscape all across Europe.[9] This rendered Europe a polar desert just south of the now expanded ice sheets, and the rest of Europe was left with a sporadic herb based plant cover.[9] Europe north of the Alps was a tundra-steppe of predominantly grasses, sedges, and chenopods,[9] while land south of the Alps featured discontinuous steppe vegetation patterns.[9] There were some refugia in the sheltered areas of the mountainous Alps and the western Balkans where tree populations survived.[9] This was due to temperature variations not being extreme in these locations, as well as precipitation still being sufficient.[9] This is unlike the rest of Europe, such as in France where pollen samples revealed a precipitation decrease of almost 60% compared to the modern day.[8] The drastic changes in the climate also resulted in increased storms in the North Atlantic, affecting Europe as well as North America.[1]

### Asia

Isotope dating was conducted in Hulu Cave, eastern China, and found that the penultimate glacial period's presence was felt in central China.[10] The dating showed an increased presence of oxygen-18, an isotope that reflects the meteoric water and cave temperature, as well as precipitation of the penultimate glacial period.[10] This data led to the confirmation of intense monsoons that impacted most of south-east Asia, and up to modern day Xi'an China.[10] The increase in the intensity of monsoons was due to the orbital shifting of the planet, but was amplified by the ice sheets that formed for the same reason.[10] These factors combined then affected the atmospheric hydrological cycle, creating more intense seasonal winds that led to increased precipitation over south-east Asia.[10]

### North America

In contrast to Europe, there is no geological evidence to support a similarly sized ice sheet in North America.[1] Ice-rafted debris from the Hudson area indicates that during MIS6, there were far fewer icebergs in the North Atlantic than in the last glacial period.[4] Simulations testing the extent of an ice sheet in North America have shown that a smaller ice sheet is probable, as the simulation produced weather data that is consistent with hypothesized temperatures at the time.[4] This simulation showed the precipitation rates over North America doubled during MIS6, which would have been a result of the icy winds expanding southward further into the continent, as well as the increased storms.[4]

A 2019 study suggested that the Penultimate Glacial Period was warmer in North America than the Last Glacial Period.[11]

### South America

In South America, the intensity of the South American Summer Monsoon (SASM) varied with a cyclical periodicity of about 3,500 years, with gradual increases in the SASM's strength being punctuated by sudden decreases. These sudden decreases are thought to be related to Dansgaard-Oeschger events.[12]

### Africa

Oceanic cores, taken from western Africa, show the deserts expanded, pushing the savannah and the tropical rainforests downward, and oak trees occupying the Mediterranean coast, disappeared.[9] This is thought to have occurred due to southward migration of the subtropical, and high pressure zone of the Mediterranean.[9]

The time interval during which the PGP took place coincided with numerous important phases of hominin evolution in Africa, including the evolution of Homo sapiens, the transition from the Acheulean to the Middle Palaeolithic, and other critical cultural and behavioural innovations.[13] Several studies have suggested that H. sapiens went through a genetic bottleneck during the Penultimate Glacial Period which reduced numbers to a low level, but a 2012 analysis of three modern African populations finds no evidence for a bottleneck at this time.[2] The dislocation of vegetation during the PGP was thought to have displaced H. sapiens,[9] although studies have shown that the region which the early humans occupied was very lightly disturbed, and a bottleneck due to the Penultimate Glacial Period is thus unlikely to have occurred.[2]

### Antarctica

The Antarctic Zone expanded northwards until encompassing the northern Kerguelen Plateau, as evidenced by the maximum abundance of the radiolarians Dictyophimus bicornis, Pseudodictyophimus gracilipes, and P. platycephalus during this glacial.[14]

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Colleoni, Florence; Wekerle, Claudia; Näslund, Jens-Ove; Brandefelt, Jenny; Masina, Simona (1 April 2016). "Constraint on the penultimate glacial maximum Northern Hemisphere ice topography (≈140 kyrs BP)". Quaternary Science Reviews 137: 97–112. doi:10.1016/j.quascirev.2016.01.024. Bibcode: 2016QSRv..137...97C.
2. ↑ 2.0 2.1 2.2 2.3 Sjödin, Per; E. Sjöstrand, Agnès; Jakobsson, Mattias; Blum, Michael G.B. (1 July 2012). "Resequencing Data Provide No Evidence for a Human Bottleneck in Africa during the Penultimate Glacial Period". Molecular Biology and Evolution 29 (7): 1851–1860. doi:10.1093/molbev/mss061. PMID 22319141.
3. ↑ Jouzel, J.; Barkov, N. I.; Barnola, J. M.; Bender, M.; Chappellaz, J.; Genthon, C.; Kotlyakov, V. M.; Lipenkov, V. et al. (July 1993). "Extending the Vostok ice-core record of palaeoclimate to the penultimate glacial period". Nature 364 (6436): 407–412. doi:10.1038/364407a0. Bibcode: 1993Natur.364..407J.
4. ↑ 4.0 4.1 4.2 4.3 Manabe, S.; Broccoli, A. J. (1985). "The influence of continental ice sheets on the climate of an ice age". Journal of Geophysical Research 90 (D1): 2167. doi:10.1029/JD090iD01p02167. Bibcode: 1985JGR....90.2167M.
5. ↑ 5.0 5.1 5.2 Roucoux, K. H.; Tzedakis, P. C.; Lawson, I. T.; Margari, V. (August 2011). "Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina, north-west Greece". Journal of Quaternary Science 26 (6): 616–626. doi:10.1002/jqs.1483. Bibcode: 2011JQS....26..616R.
6. ↑ Holbourn, Ann; Kuhnt, Wolfgang; Clemens, Steven; Prell, Warren; Andersen, Nils (December 2013). "Middle to late Miocene stepwise climate cooling: Evidence from a high-resolution deep water isotope curve spanning 8 million years". Paleoceanography 28 (4): 688–699. doi:10.1002/2013PA002538. Bibcode: 2013PalOc..28..688H.
7. ↑ Baumann, Karl-Heinz; Lackschewitz, Klas S.; Mangerud, Jan; Spielhagen, Robert F.; Wolf-Welling, Thomas C.W.; Henrich, Rüdiger; Kassens, Heidemarie (1 March 1995). "Reflection of Scandinavian Ice Sheet Fluctuations in Norwegian Sea Sediments during the Past 150,000 Years". Quaternary Research 43 (2): 185–197. doi:10.1006/qres.1995.1019. Bibcode: 1995QuRes..43..185B. http://oceanrep.geomar.de/31248/1/1-s2.0-S0033589485710198-main.pdf.
8. ↑ 8.0 8.1 8.2 8.3 Wainer, Karine; Genty, Dominique; Blamart, Dominique; Bar-Matthews, Miryam; Quinif, Yves; Plagnes, Valérie (15 April 2013). "Millennial climatic instability during penultimate glacial period recorded in a south-western France speleothem". Palaeogeography, Palaeoclimatology, Palaeoecology 376: 122–131. doi:10.1016/j.palaeo.2013.02.026. Bibcode: 2013PPP...376..122W.
9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 Van Andel, T.; Tzedakis, P. C. (1 January 1996). "Palaeolithic landscapes of Europe and environs, 150,000-25,000 years ago: An overview". Quaternary Science Reviews 15 (5–6): 481–500. doi:10.1016/0277-3791(96)00028-5. Bibcode: 1996QSRv...15..481V.
10. ↑ 10.0 10.1 10.2 10.3 10.4 Cheng, Hai; Edwards, R. Lawrence; Wang, Yongjin; Kong, Xinggong; Ming, Yanfang; Kelly, Megan J.; Wang, Xianfeng; Gallup, Christina D. et al. (1 March 2006). "A penultimate glacial monsoon record from Hulu Cave and two-phase glacial terminations". Geology 34 (3): 217–220. doi:10.1130/G22289.1. Bibcode: 2006Geo....34..217C.
11. ↑ Batchelor, Cameron J.; Orland, Ian J.; Marcott, Shaun A.; Slaughter, Richard; Edwards, R. Lawrence; Zhang, Pu; Li, Xianglei; Cheng, Hai (2019-11-28). "Distinct Permafrost Conditions Across the Last Two Glacial Periods in Midlatitude North America" (in en). Geophysical Research Letters 46 (22): 13318–13326. doi:10.1029/2019GL083951. ISSN 0094-8276. Bibcode: 2019GeoRL..4613318B. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083951.
12. ↑ Burns, Stephen J.; Welsh, Lisa Kanner; Scroxton, Nick; Cheng, Hai; Edwards, R. Lawrence (4 February 2019). "Millennial and orbital scale variability of the South American Monsoon during the penultimate glacial period" (in en). Scientific Reports 9 (1): 1234. doi:10.1038/s41598-018-37854-3. ISSN 2045-2322. PMID 30718651. Bibcode: 2019NatSR...9.1234B.
13. ↑ Foerster, Verena; Asrat, Asfawossen; Bronk Ramsey, Christopher; Brown, Erik T.; Chapot, Melissa S.; Deino, Alan; Duesing, Walter; Grove, Matthew et al. (26 September 2022). "Pleistocene climate variability in eastern Africa influenced hominin evolution" (in en). Nature Geoscience 15 (10): 805–811. doi:10.1038/s41561-022-01032-y. ISSN 1752-0908. PMID 36254302. Bibcode: 2022NatGe..15..805F.
14. ↑ Civel-Mazens, M.; Crosta, X.; Cortese, G.; Michel, E.; Mazaud, A.; Ther, O.; Ikehara, M.; Itaki, T. (1 July 2021). "Antarctic Polar Front migrations in the Kerguelen Plateau region, Southern Ocean, over the past 360 kyrs". Global and Planetary Change 202. doi:10.1016/j.gloplacha.2021.103526. ISSN 0921-8181. Bibcode: 2021GPC...20203526C. https://archimer.ifremer.fr/doc/00696/80832/84409.pdf. Retrieved 25 December 2023.

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Ice ages

Quaternary /
Late Cenozoic|

| Quaternary|

* Antarctica
* Greenland
* Penultimate Glacial Period
* Last Glacial Period (Last Glacial Maximum)
* 1st: Würm, Wisconsin, Weichselian, Devensian/Midlandian, Pinedale/Fraser, Merida, Llanquihue
* 2nd: Riss, Illinoian, Saale, Wolstonian, Santa María
* 3rd–6th: Mindel, Pre-Illinoian, Elster, Anglian, Rio Llico
* 7th–8th: Günz, Pre-Illinoian, Elbe or Menapian, Beestonian, Caracol (2.5 to 0 Mya)

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Pliocene
Miocene
Oligocene|

* Antarctic (34 to 2.5 Mya)

Carboniferous–Permian|

* Late Paleozoic icehouse (360 Mya to 260 Mya)

Late Ordovician glaciation|

* Andean-Saharan (460 Mya to 430 Mya)

Ediacaran|

* Gaskiers (579.88 to 579.63 Mya)
* Baykonurian (547 to 541.5 Mya)

Cryogenian|

* Sturtian (717 to 660 Mya); Marinoan (650 to 635 Mya)

Paleoproterozoic|

* Huronian (2.4 to 2.1 Gya)

Mesoarchean|

* Pongola (2.9 to 2.78 Gya)

Related topics|

* Greenhouse and icehouse Earth
* Great Oxygenation Event
* Snowball Earth
* Interglacial
* Milankovitch cycles
* Stadial

Timeline of glaciation

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Continental glaciations

General|

* Cordilleran ice sheet
* Laurentide Ice Sheet
* Last Glacial Maximum
* Canadian Shield
* Glacial history of Minnesota
* List of prehistoric lakes
* Proglacial lake
* Lake Agassiz
* Lake Chicago
* Lake Tight
* Teays River
* Post-glacial rebound
* Timeline of glaciation

Landforms|

| Erosional|

* Fjord
* Glacial striae
* Ribbon lake
* Roche moutonnée
* Tunnel valley
* U-shaped valley

|

Depositional|

* Drumlin
* Erratic block
* Moraine
* Pulju moraine
* Rogen moraine
* Terminal moraine
* Till plain
* Veiki moraine

| Glacifluvial|

* Diluvium
* Esker
* Giant current ripples
* Kame
* Kame delta
* Kettle hole
* Outwash fan
* Sandur

|

North America|

| Canada|

* Arrowhead Provincial Park, Ontario
* Big Rock (glacial erratic), Alberta
* Cypress Hills (Canada), Saskatchewan
* Eramosa River, Ontario
* Eskers Provincial Park, British Columbia
* Foothills Erratics Train, Alberta
* Lion's Head Provincial Park, Ontario
* Origin of the Oak Ridges Moraine, Ontario
* Ovayok Territorial Park, Nunavut

|

United
States|

* Chippewa Moraine State Recreation Area, Wisconsin
* Coteau des Prairies, South Dakota
* Devil's Lake State Park, Wisconsin
* Glacial Lake Wisconsin, Wisconsin
* Glacial Lakes State Park, Minnesota
* Horicon Marsh State Wildlife Area, Wisconsin
* Ice Age Floods National Geologic Trail, Idaho, Oregon & Washington
* Ice Age National Scientific Reserve, Wisconsin
* Ice Age Trail, Wisconsin
* Interstate State Park, Minnesota & Wisconsin
* Kelleys Island, Ohio
* Kettle Moraine State Forest, Wisconsin
* Lake Bonneville, Utah
* Lake Lahontan, Nevada
* Lake Missoula, Montana
* Mill Bluff State Park, Wisconsin
* Oneida Lake, New York
* Two Creeks Buried Forest State Natural Area, Wisconsin
* Withrow Moraine and Jameson Lake Drumlin Field, Washington
* Yosemite National Park, California

Eurasia and
Antarctica|

* Antarctica
* Hardangerfjord
* Killary Harbour
* Lambert Glacier
* Monte Rosa
* Ross Ice Shelf
* Svalbard

Time periods|

* Quaternary glaciation
* Illinoian Stage
* Interglacial
* Interstadial
* Penultimate Glacial Period
* Last Glacial Period
* Last Glacial Maximum
* Mousterian Pluvial
* Holocene glacial retreat
* Oldest Dryas
* Older Dryas
* Pleistocene
* Pre-Illinoian Stage
* Quaternary glaciation
* Sangamonian Stage
* Wisconsin glaciation
* Bølling-Allerød warming
* Late Glacial Interstadial
* Huelmo–Mascardi Cold Reversal
* Younger Dryas
* African humid period
* 8.2 kiloyear event
* 4.2 kiloyear event
* Piora Oscillation
* Little Ice Age

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