Reconstruction of the density profile, surface mass balance history and vertical strain profile on the divide of the Derwael Ice Rise in coastal Dronning Maud Land, East Antarctica.

• Main Author: Philippe, Morgane
• Other Authors: Tison, Jean-Louis, Pattyn, Frank, Debaille, Vinciane, Hubbard, Bryn, Dehairs, Frank
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universite Libre de Bruxelles 2017
• Subjects: Glaciologie; Ice core; surface mass balance; accumulation; vertical strain rate; density; Antarctica; Antarctic; East Antarctica; Dronning Maud Land; Antarc*; DML; ice core; Ice Sheet; Ice Shelf; Ice Shelves; Sea ice
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/254506; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/5/ThesisManuscriptEmbargo.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/7/Appendix.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/8/ContratDiPhilippe.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/3/Contents.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/6/ThesisManuscriptNoEmbargo.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/254506/4/Appendix2.pdf

Antarctic mass balance is mainly controlled by surface mass balance (SMB, i.e. the net effect of precipitations at the surface of the ice sheet) and ice discharge at its margins, mostly through ice shelves. These floating ice bodies made from ice flowing from the continent to the ocean are buttressed by ice rises (elevation of the sea floor on which ice shelf re-grounds) such as the Derwael Ice Rise (DIR) in Dronning Maud Land (DML). In addition to this role important to consider in the future contribution of Antarctica to sea level rise, ice rises are also “climate dipsticks” helping to reconstruct the climate of the past centuries to millennia at high resolution. Due to their coastal location, they witness the changes happening there more rapidly than inland. Furthermore, their internal stratigraphy forms arches that allow to assess their stability, to date their own formation and therefore, in some cases, to constrain the past extension of the ice sheet at the scale of several millennia. As part of the IceCon project :Constraining ice mass changes in Antarctica, this thesis aimed to drill a 120 m ice core (named IC12 for the IceCon project, 2012) at the divide of the DIR and perform physico-chemical analyses to study its density and its internal annual layering with the aim of reconstructing SMB of the last two centuries. We also recorded a virtual image of the borehole using an optical televiewer (OPTV) to assess the ability of this instrument to reconstruct a density profile and measure vertical strain rates when the logging is repeated in the same borehole after a sufficient period of time (here, 2 years).The results show a general increase in snow accumulation rates (SMB) of 30-40% during the 20th century, particularly marked during the last 20-50 years. SMB variability is governed to a large extent by atmospheric circulation and to a lesser extent by variations in sea ice cover. The vertical velocity profile measured from repeat borehole OPTV was applied to refine SMB correction and the results fall in ...