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Numerical simulations of the Cordilleran ice sheet through the last glacial cycle
Stockholm University, Faculty of Science, Department of Physical Geography. ETH Zürich, Switzerland; GFZ German Research Centre for Geosciences, Germany.
Stockholm University, Faculty of Science, Department of Physical Geography.
Stockholm University, Faculty of Science, Department of Physical Geography.
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Number of Authors: 5
2016 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 10, no 2, 639-664 p.Article in journal (Refereed) Published
Abstract [en]

After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2-56.9 ka) and 2 (23.2-16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka).

Place, publisher, year, edition, pages
2016. Vol. 10, no 2, 639-664 p.
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-133259DOI: 10.5194/tc-10-639-2016ISI: 000379411800012OAI: oai:DiVA.org:su-133259DiVA: diva2:957994
Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2017-02-22Bibliographically approved
In thesis
1. Numerical modelling of the Cordilleran ice sheet
Open this publication in new window or tab >>Numerical modelling of the Cordilleran ice sheet
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral dissertation presents a study of the glacial history of the North American Cordillera using numerical ice sheet modelling calibrated against field evidence. This area, characterized by the steep topography of several mountain ranges separated by large inter-montane depressions, was once covered by a large-scale ice mass: the former Cordilleran ice sheet. Because of the irregular topography on which the ice sheet formed, geological studies have often had only local or regional relevance, thus leaving the Cordilleran ice sheet least understood among Pleistocene ice sheets in terms of its extent, volume, and dynamics.

Here, I present numerical simulations that allow quantitative reconstructions of the former ice sheet evolution based on approximated physics of glacier flow. These simulations show that the geometry of the Last Glacial Maximum Cordilleran ice sheet was largely controlled by sharp contrasts in regional temperature, precipitation, and daily temperature variability associated with the presence of mountain ranges.

However, this maximum stage appears short-lived and out of balance with contemporaneous climate. During most of the simulated last glacial cycle, the North American Cordillera is characterized by an intermediate state of glaciation including isolated glaciers and ice caps covering major mountain ranges, the largest of which is located over the Skeena Mountains. The numerically modelled Cordilleran ice sheet appears in constant imbalance with evolving climate conditions, while the complexity of this transient response transcends that encapsulated in two-dimensional, conceptual models of ice sheet growth and decay.

This thesis demonstrates the potential of numerical ice sheet modelling to inform on ice sheet history and former climate conditions over a glacial cycle, given that ice sheet models can be calibrated against field constraints.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2014. 27 p.
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 43
Keyword
Numerical modelling, Cordilleran ice sheet, last glacial cycle
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-106815 (URN)978-91-7447-973-7 (ISBN)
Public defence
2014-09-25, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Mansucript.

Available from: 2014-09-03 Created: 2014-08-21 Last updated: 2017-02-22Bibliographically approved

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