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A Model of the Greenland Ice Sheet Deglaciation

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A Model of the Greenland Ice Sheet Deglaciation A MODEL OF THE GREENLAND ICE SHEET DEGLACIATION Benoit Lecavalier Thesis submitted to the Faculty of Graduate and Postdoctoral Studies in partial fulfilment of the requirements for the Master of Science degree in Physics Department of Physics Faculty of Science University of Ottawa © Benoit Lecavalier, Ottawa, Canada, 2014 2 ABSTRACT The goal of this thesis is to improve our understanding of the Greenland ice sheet (GrIS) and how it responds to climate change. This was achieved using ice core records to infer elevation changes of the GrIS during the Holocene (11.7 ka BP to Present). The inferred elevation changes show the response of the ice sheet interior to the Holocene Thermal Maximum (HTM; 9-5 ka BP) when temperatures across Greenland were warmer than present. These ice-core derived thinning curves act as a new set of key constraints on the deglacial history of the GrIS. Furthermore, a calibration was conducted on a three- dimensional thermomechanical ice sheet, glacial isostatic adjustment, and relative sea-level model of GrIS evolution during the most recent deglaciation (21 ka BP to present). The model was data-constrained to a variety of proxy records from paleoclimate archives and present-day observations of ice thickness and extent. 3 DECLARATION The following is a declaration made by the lead author of the research article on the “Revised estimates of Greenland ice sheet thinning histories based on ice-core records”, which was published in the Journal of Quaternary Science Reviews and is Section 2 of this thesis. I conducted all the numerical modelling for this study, which involved the calibration of a GIA model for the Canadian Arctic by constraining it to RSL to determine vertical land motion spatially and temporally. I applied these findings and improved the methodologies needed to derive more accurate elevation histories for the Greenland ice sheet. This was performed using ice-core records, which I also used to derive temperature reconstructions at the periphery of the ice sheet. I wrote the manuscript independently, although I did receive comments from my research advisor (Glenn Milne). This research entailed the initiation of international collaborations. While my advisor supplied the models, newly established collaborators at National Resources Canada (NRCan) (David Fisher) and Niels Bohr Institute in Denmark (Bo Vinther) provided insight and feedback on my proposed methodologies based on their expertise in ice-core research. Arthur Dyke, also at NRCan, provided copious RSL data to constrain our model and finally, my collaborator in Norway (Matthew Simpson) provided a recent reconstruction of the Greenland ice sheet to input within our GIA model of sea-level change. The published results are relevant to multiple disciplines, from glaciology and Greenland field geology, to ice sheet, sea-level and climate modelling. We therefore selected a journal which has high visibility within these disciplines (5-year impact factor 5.04). Furthermore, in September 2013 the article was cited in the United Nations (UNEP & WMO) established Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (AR5 WG1). The research article on “A model of Greenland ice sheet deglaciation based on observations of ice extent and relative sea-level”, was recently submitted into the Journal of Quaternary Science Reviews and is Secton 3 of this thesis. I conducted all the numerical modelling for this study, which involved the calibration of a glaciological, GIA and RSL model for the GrIS over the deglaciation. The manuscript was written independently, although similarly to the previous publication I did receive comments from my 4 research advisor. This research established international collaborations across multiple disciplines. My advisor supplied the GIA and RSL model, while my colleague Philippe Huybrechts (Vrije Universiteit Brussel, Belgium) provided the three-dimensional thermomechanical ice sheet model. Model developments on the climate forcing component of the ice sheet model were performed in collaboration with Leanne Wake (University of Northumbria, UK). Based on weather station observations, she concluded a revised positive degree day algorithm which we implemented. I benchmarked the model and conducted several sensitivity analyses to validate the theoretical behaviour of the developments. Lev Tarasov from Memorial University provided a collection of North American ice sheet models which I amalgamated to our global ice model to study the implications to Greenland RSL. Newly established collaborators in Denmark: Nicolaj Larsen, Kristian Kjeldsen and Svend Funder (Aarhus University; University of Copenhagen) have provided ice extent and RSL data along with feedback on the resulting ice sheet reconstructions based on their expertise in Greenland field geology. Similarly, Antony Long and Sarah Woodroffe from Durham University (UK) along with Arthur Dyke (NRCan) have provided large compilations of RSL data to constrain our models. Finally, my collaborator Matthew Simpson (Norwegian Mapping Authority), who conducted the previous Huy2 model study that I build upon, has contributed through guidance and feedback on my proposed methodology. On a similar basis as the Greenland thinning curves research paper being submitted to the Journal of Quaternary Science Reviews, the Huy3 study was justifiably submitted to this same journal. 5 FORWARD Throughout my Master of Science program I had the opportunity to attend several conferences and workshops where I presented the research contained within this thesis. Furthermore, I took part of two summerschools where I was taught on the newest developments in my research field. I established over a dozen successful international and national collaborations with internationally renowned researchers based in the UK, Belgium, Denmark, Norway, USA, and Canada. Finally, the core of this thesis consists of two publications, both of which I am first author. In addition to these two projects I was also involved in a number of other studies which have materialized into complementing publications. Conferences & Workshops: Milne, G.A.*, Lecavalier, B.S., Kjeldsen, K.K., Kjær, K., Wolstencroft, M.,Wake, L., Simpson, M.J.R., Korsgaard, N.J., Bjørk, A., Khan, A. (2013) Uncertainty in Greenland glacial isostatic adjustment. American Geophysical Union Fall meeting, San Francisco, USA. abstract submitted. Buizert, C.*, Gkinis, V., Severinghaus, J.P., He, F., Lecavalier, B.S., Carlson, A.,White, J.W.C., Vinther, B., Brook, E.J. (2013) Greenland temperature response to climate forcing during the last deglaciation. American Geophysical Union Fall meeting, San Francisco, USA. abstract submitted. Lecavalier, B.S.*, Milne, G.A.,Wake, L., Simpson, M.J.R., Kjeldsen, K.K., Funder, S., Woodroffe, S., Long, A., Huybrechts, P., Tarasov, L., Dyke, A. (2013) Calibrating a model of the Greenland ice sheet from the last glacial maximum to present. International Geodesy Symposium, Ilullisat, Greenland . Oral presentation. Lecavalier, B.S.*, Wake, L., Milne, G.A., Marshall, S., Simpson, M.J.R., Huybrechts, P. (2013) Sensitivity of the Greenland ice sheet to the Holocene thermal maximum. PAGES Open Science Meeting, Goa, India. Oral presentation. Lecavalier, B. S.*, Milne, G. A., Vinther, B. M., Fisher, D. A., Dyke, A. S., Simpson, M. J. R., Tarasov, L. (2012) Revised estimates of Greenland ice sheet thinning histories based on ice-core records. PALSEA, Wisconsin, USA. Poster presentation. Wake, L.*, Marshall, S., Milne, G., Lecavalier, B. S., Bayou, N., Huybrechts, P., Hanna, E. (2012) Linking surface energy balance calculations and temperature index models of surface melt: Revision of the positive degree day (PDD) methodology for the Greenland ice sheet. European Geophysical Union Assembly, Vienna. Poster presentation. Lecavalier, B. S.*, Milne, G. A., Vinther, B. M., Fisher, D. A., Dyke, A. S., Simpson, M. J. R. (2011) The influence of land uplift on the isotopic temperature record from the Agassiz ice cap: implications for the Holocene thinning of the Greenland ice sheet. American Geophysical Union Fall meeting, San Francisco, USA. Poster presentation. Summerschools: Lecavalier, B.S., Milne, G. A., Simpson, M. J. R., Wake, L., Huybrechts, P., Kjeldsen, K. K., Funder, S., Tarasov, L., Long, A. J., Woodroffe, S. A.,Larsen, N.K., Dyke, A. (2013) A model of Greenland ice sheet deglaciation based on observations of ice extent and relative sea-level. ACDC summer school, Nyksund, Norway. Oral presentation. Lecavalier, B. S.*, (2011) Reconstructing the evolution of an ice sheet. Karthaus summer school, Karthaus, Italy. Oral presentation. 6 Articles Published: Lecavalier, B. S., Milne, G. A., Vinther, B. M., Fisher, D. A., Dyke, A. S., Simpson, M. J. R. (2013) Revised Estimates of Greenland ice sheet thinning histories based on ice-core records. Quaternary Science Reviews. 63: 73-82. Woodroffe, S. A., Long, A. J., Lecavalier, B.S., Milne, G. A., Bryant, C. L. (2013) Using relative sea- level data to constrain the deglacial history of southern Greenland. Quaternary Science Reviews. JQSR-D-13-00050R1, In Press. Lecavalier, B.S., Milne, G. A., Simpson, M. J. R., Wake, L., Huybrechts, P., Kjeldsen, K. K., Funder, S., Tarasov, L., Long, A. J., Woodroffe, S. A.,Larsen, N.K., Dyke, A. (Submitted) A model of Greenland ice sheet deglaciation based on observations of ice extent and relative sea-level. Quaternary Science Reviews. 7 ACKNOWLEDGEMENTS I would like to start by thanking my supervisor Glenn Milne who has been
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