7
Contents
Résumé ... 3
Abstract ... 4
Remerciements ... 5
List of abbreviations ... 10
Objectives and outline ... 11
1 GENERAL INTRODUCTION ... 14
1.1 Motivation ... 14
1.2 The cryosphere and the climate ... 14
1.2.1 Description of the cryosphere ... 14
1.2.2 How is Antarctic ice affected by climate change? ... 17
1.2.3 Climate-cryosphere feedbacks in Antarctica ... 18
1.3 Contribution of Antarctica to sea level rise ... 21
1.3.1 Global relative contribution to sea level rise ... 21
1.3.2 Methods for estimating the contribution of Antarctica to sea level rise ... 22
1.3.3 Mass balance of coastal Antarctica... 22
1.4 The IceCon project : Constraining ice mass changes in Antarctica ... 26
1.5 The climate record of Antarctic ice rises ... 27
1.5.1 Ice core record (centennial to millennial scale) ... 27
1.5.2 Englacial stratigraphy (millennial scale) ... 30
1.6 Specific properties of Antarctic ice shelves ... 31
1.6.1 Subglacial channels (a contribution to basal mass balance) ... 32
1.6.2 Melt ponds (a contribution to surface mass balance) ... 33
2 METHODS ... 35
2.1 Main study site and ice core drilling within the IceCon project ... 35
2.2 Physical measurements ... 37
2.2.1 Density ... 37
2.2.2 Vertical movement ... 39
2.2.3 Submergence velocity and strain rate determination ... 43
2.3 Chemical analyses... 43
2.3.1 Water stable isotopic composition ... 44
8
2.3.2 Ion chromatography ... 45
2.3.3 Electric Conductivity Measurements ... 46
3 RESULTS AND DISCUSSION ... 47
3.1 Ice shelf density reconstructed from optical televiewer borehole logging: Determining the density profile of the ice core ... 47
3.1.1 Introduction ... 47
3.1.2 Field site and methods... 49
3.1.3 OPTV luminosity and core density ... 50
3.1.4 Summary and discussion ... 55
3.1.5 Acknowledgements ... 55
3.1.6 References ... 55
3.2 Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica: Dating the ice core and reconstructing past accumulation rates ... 57
3.2.1 Introduction ... 58
3.2.2 Field site and methods... 59
3.2.3 Results ... 64
3.2.4 Discussion ... 72
3.2.5 Conclusions ... 75
3.2.6 Data Availability ... 75
3.2.7 Acknowledgements ... 76
3.2.8 References ... 76
3.3 A new method using repeated OPTV records to reconstruct “in-situ” submergence velocities and vertical strain rates of firn and ice at Derwael ice rise and related applications ... 83
3.3.1 High-resolution vertical velocity and strain rates reconstructed from optical televiewer- based layer differencing: Derwael ice rise, East Antarctica ... 83
3.3.2 Implications for SMB corrections ... 96
3.3.3 Independent check on the age-depth profile and preliminary implications for the steady- state hypothesis ... 99
4 CONTRIBUTION TO OTHER STUDIES ... 101
4.1 Surface Mass Balance of Antarctic ice rises ... 101
4.1.1 Temporally stable surface mass balance asymmetry across an ice rise derived from radar internal reflection horizons through inverse modeling ... 101
4.1.2 High variability of climate and surface mass balance induced by Antarctic ice rises ... 105
9
4.2 Specific features of Antarctic ice shelves ... 107
4.2.1 Constraining variable density of ice shelves using wide-angle radar measurements ... 109
4.2.2 Massive subsurface ice formed by refreezing of ice-shelf melt ponds ... 112
4.3 IceCon : Constraining ice mass changes in Antarctica ... 114
4.4 Ice core evidence of SMB dissymmetry around ice rises: preliminary results ... 115
5 GENERAL CONCLUSION ... 118
5.1 Synthesis of the findings ... 118
5.2 Perspectives for future work ... 119
5.2.1 Additional ice core drilling and analyses ... 119
5.2.2 Optical televiewer method ... 120
5.2.3 Implications for regional and large scale climate ... 120
References ... 122
List of publications ... 133
Appendix ... 135
