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The Late Saalian period (160 - 140 ka): insight on an unusual glaciation
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
Stockholm University, Faculty of Science, Department of Meteorology .
Laboratoire de Glaciologie et Géophysique de l'Environnement - Grenoble (France).
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This work focuses on the climate evolution over the Late Saalian period (160 - 140 ka) over Eurasia. At this time, the Eurasian ice sheet was larger and higher than during the Last Glacial Maximum. June insolation over the high latitudes presents a large fluctuation over this period: two glacial minima toward 160 and 140 ka and a large insolation peak toward 150 ka. From the geological evidence chronology, it seems clear that the large Eurasian ice sheet already reached its maximum extent at 160 ka. To understand how this ice sheet could survive the 150 ka June insolation maximum, we use several numerical models to simulate the evolution of the vegetation cover, the surface ocean temperatures and finally the evolution of the Late Saalian climate over the three time slices 140, 150 and 160 ka. Results show that the Late Saalian climate variations are dominated by orbital forcings, responding to a large eccentricity enhancing the precession effect especially at 140 ka. From 160 to 150 ka, the surface ocean exhibits open water conditions in the North At- lantic during summer while sea surface temperature at 140 ka are clearly colder with a large sea ice extent reaching 40◦ N in both the North Atlantic and the North Pacific. This corresponds to a milder climate before 140 ka inducing a larger positive surface mass balance despite the 150 ka insolation peak because of larger precipitation rates. On the contrary, the drastic cooling caused by the astronomical forcing at 140 ka leads to a drier climate cancelling ablation and reducing the accumulation over the ice sheet.

URN: urn:nbn:se:su:diva-29302OAI: diva2:232273
Available from: 2009-08-21 Created: 2009-08-20 Last updated: 2010-01-14Bibliographically approved
In thesis
1. On the Late Saalian glaciation: A climate modeling study
Open this publication in new window or tab >>On the Late Saalian glaciation: A climate modeling study
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the glaciation of the Late Saalian period (160 -140 ka) over Eurasia. The Quaternary Environment of the Eurasian North (QUEEN) project determined that during this period, the Eurasian ice sheet was substantially larger than during the entire Weichselian cycle and especially that of the Last Glacial Maximum (21 ka, LGM). The Late Saalian astronomical forcing was different than during the LGM while greenhouse gas concentrations were similar. To understand how this ice sheet could have grown so large over Eurasia during the Late Saalian, we use an Atmospherical General Circulation Model (AGCM) coupled to an oceanic mixed layer and a vegetation model to explore the influence of regional parameters, sea surface temperatures (SST) and orbital parameters on the surface mass balance (SMB) of the Late Saalian Eurasian ice sheet.

At140 ka, proglacial lakes, vegetation and simulated Late Saalian SST cool the Eurasian climate, which reduce the ablation along the southern ice sheet margins. Dust deposition on snow has the opposite effect. The presence of a Canada Basin ice-shelf during MIS6 in the Arctic Ocean, does not affect the mass balance of the ice sheet. According to geological evidence, the Late Saalian Eurasian ice sheet reached its maximum extent before 160 ka. Northern Hemisphere high latitude summer insolation shows a large insolation peak near 150 ka. The simulated climate prior to 140 ka is milder and ablation is larger along the southern margins of the Eurasian ice sheet although the mean annual SMB is positive. The Late Saalian Eurasian ice sheet may have been large enough to generate its own cooling, thus maintaining itself over Eurasia. 

Place, publisher, year, edition, pages
Stockholm: Department of Geology and Geochemistry, Stockholm University, 2009. 53 p.
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 335
Climate modeling, Eurasian ice sheet, Quaternary, Saalian, surface mass balance, SST
National Category
Earth and Related Environmental Sciences
Research subject
Marine Geoscience
urn:nbn:se:su:diva-29284 (URN)978-91-7155-914-2 (ISBN)
Public defence
2009-09-14, Laboratoire de Glaciologie et Géophysique de l'Environnement, Université Joseph Fourier, 54 rue Moliére, St-Martin d'Héres Cedex, France, 10:00 (English)
Joint PhD Degree between Stockholm University and Université Joseph Fourier At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Submitted. Paper 5: Manuscript.Available from: 2009-08-30 Created: 2009-08-20 Last updated: 2009-08-21Bibliographically approved

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Colleoni, FlorenceLiakka, JohanJakobsson, Martin
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