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The effect of climate forcing on numerical simulations of the Cordilleran ice sheet at the Last Glacial Maximum
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
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Number of Authors: 5
2014 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 8, no 3, 1087-1103 p.Article in journal (Refereed) Published
Abstract [en]

We present an ensemble of numerical simulations of the Cordilleran ice sheet during the Last Glacial Maximum performed with the Parallel Ice Sheet Model (PISM), applying temperature offsets to the present-day climatologies from five different data sets. Monthly mean surface air temperature and precipitation from WorldClim, the NCEP/NCAR reanalysis, the ERA-Interim reanalysis, the Climate Forecast System Reanalysis and the North American Regional Reanalysis are used to compute surface mass balance in a positive degree-day model. Modelled ice sheet outlines and volumes appear highly sensitive to the choice of climate forcing. For three of the four reanalysis data sets used, differences in precipitation are the major source for discrepancies between model results. We assess model performance against a geomorphological reconstruction of the ice margin at the Last Glacial Maximum, and suggest that part of the mismatch is due to unresolved orographic precipitation effects caused by the coarse resolution of reanalysis data. The best match between model output and the reconstructed ice margin is obtained using the high-resolution North American Regional Reanalysis, which we retain for simulations of the Cordilleran ice sheet in the future.

Place, publisher, year, edition, pages
2014. Vol. 8, no 3, 1087-1103 p.
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-106608DOI: 10.5194/tc-8-1087-2014ISI: 000338655600021OAI: oai:DiVA.org:su-106608DiVA: diva2:737615
Note

AuthorCount:5;

Available from: 2014-08-13 Created: 2014-08-12 Last updated: 2017-12-05Bibliographically 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)
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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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