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Evolution of the large-scale atmospheric circulation in response to changing ice sheets over the last glacial cycle
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2014 (English)In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 10, no 4, 1453-1471 p.Article in journal (Refereed) Published
Abstract [en]

We present modelling results of the atmospheric circulation at the cold periods of marine isotope stage 5b (MIS 5b), MIS 4 and the Last Glacial Maximum (LGM), as well as the interglacial. The palaeosimulations are forced by ice-sheet reconstructions consistent with geological evidence and by appropriate insolation and greenhouse gas concentrations. The results suggest that the large-scale atmospheric winter circulation remained largely similar to the interglacial for a significant part of the glacial cycle. The proposed explanation is that the ice sheets were located in areas where their interaction with the mean flow is limited. However, the LGM Laurentide Ice Sheet induces a much larger planetary wave that leads to a zonalisation of the Atlantic jet. In summer, the ice-sheet topography dynamically induces warm temperatures in Alaska and central Asia that inhibits the expansion of the ice sheets into these regions. The warm temperatures may also serve as an explanation for westward propagation of the Eurasian Ice Sheet from MIS 4 to the LGM.

Place, publisher, year, edition, pages
2014. Vol. 10, no 4, 1453-1471 p.
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:su:diva-106949DOI: 10.5194/cp-10-1453-2014ISI: 000339896100012OAI: oai:DiVA.org:su-106949DiVA: diva2:741819
Available from: 2014-08-29 Created: 2014-08-29 Last updated: 2017-12-05Bibliographically approved
In thesis
1. On the interaction between ice sheets and the large-scale atmospheric circulation over the last glacial cycle
Open this publication in new window or tab >>On the interaction between ice sheets and the large-scale atmospheric circulation over the last glacial cycle
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The last glacial cycle (c. 115-12 kyr BP) was the most recent in a series of recurring glaciations of the subpolar continents. Massive ice sheets evolved in Eurasia and North America, which, at their maximum, were of continental scale and together lowered the global sea-level by approximately 100 m. The paleo-modelling community has focused on the last glacial maximum (LGM, ~ 20 kyr BP), leaving the longer period when the ice sheets evolved to their LGM configurations largely unexplored.

In this thesis we study the mutual interaction between the time-mean atmospheric circulation and the evolution of the Northern Hemisphere ice sheets over the build-up phase of the last glacial cycle. Experiments are conducted with coupled atmosphere-ice-sheet models and a circulation model forced by geologically consistent reconstructions of the ice-sheet topography at key stages of the glacial cycle.

The main findings from these studies are that the ice evolution in North America may have been controlled by circulation anomalies induced by the background topography in conjunction with the ice sheets themselves. A geologically consistent pre-LGM ice sheet could only be obtained when including the North American Cordillera. However, the ice sheets' influence on the local climate conditions is also found to be paramount for this configuration. We further suggest that the incipient ice sheets may have had a limited influence on the large-scale winter circulation as a result of their location relative the westerly mean flow. The LGM Laurentide Ice Sheet (LIS) was, however, different because of its continent-wide extent, and it may therefore have had a large influence on the planetary-scale circulation, especially in the Atlantic sector. We find that the planetary waves forced by the LIS were considerably larger than at earlier times, and, as a result of a more frequent planetary wave reflection over the Atlantic Ocean basin, an altered stationary wave field and a zonalised winter jet.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2014. 49 p.
Keyword
Atmospheric stationary waves, coupled atmosphere-ice sheet modelling, stationary wave-ice sheet interactions
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-107925 (URN)978-91-7649-010-5 (ISBN)
Public defence
2014-11-11, Ahlmannsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

Available from: 2014-10-20 Created: 2014-10-03 Last updated: 2014-11-18Bibliographically approved

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