Preface ........................................................ ix
List of figures .............................................. xiii
List of tables ................................................ xxi
List of abbreviations ....................................... xxiii
About the author ............................................. xxix
Publisher credits ............................................ xxxi
1 Polar ice sheets: Introduction ............................... 1
1.1 The global importance of polar ice sheets ............... 1
1.2 Ice-sheet mass balance—background information .......... 10
1.2.1 Comparative characteristics of the Greenland
and Antarctic Ice Sheets ........................ 16
1.2.2 Approaches to the measurement of ice-sheet
mass balance .................................... 16
1.3 The recent revolution in satellite remote sensing ...... 21
1.4 References ............................................. 24
2 Synthetic aperture radar interferometry and related
techniques .................................................. 39
2.1 Introduction and background ............................ 39
2.2 Underlying principles and terminology of InSAR ......... 41
2.2.1 The basis of ice sheet surface elevation and
motion measurement by satellite repeat-pass
interferometry .................................. 46
2.2.2 Measurement of ice-surface displacement/
motion .......................................... 50
2.2.3 What is an interferogram? ....................... 54
2.3 Inherent constraints and sources of ambiguity and
error .................................................. 55
2.3.1 Thermal decorrelation ........................... 56
2.3.2 Temporal decorrelation .......................... 57
2.3.3 Decorrelation due to excessive target motion/
rotation ........................................ 59
2.3.4 Atmospheric and ionospheric propagation delay ... 60
2.3.5 Baseline (spatial) decorrelation ................ 62
2.3.6 Volume decorrelation, and ambiguities relating
to radar penetration depth and volume
scattering ...................................... 63
2.3.7 Image speckle ................................... 66
2.3.8 Geometric distortions and steep terrain
effects ......................................... 67
2.3.9 Estimation of phase decorrelation ............... 67
2.3.10 Processing errors and other sources of
ambiguity ....................................... 70
2.3.11 Summary of baseline-related trade-offs .......... 70
2.4 Satellite-SAR interferometric data requirements and
processing steps. ...................................... 71
2.4.1 Selection of suitable SAR images ................ 74
2.4.2 Geometric co-registration ....................... 81
2.4.3 Pre-processing and interferogram generation ..... 82
2.4.4 Phase unwrapping ................................ 84
2.4.5 Phase-to-height conversion ...................... 89
2.4.6 Interferogram geo-coding ........................ 89
2.5 The measurement of ice-sheet elevation and surface
velocity using differential InSAR techniques ........... 90
2.5.1 Ice-sheet topography from DInSAR ................ 92
2.5.2 Retrieval of ice-sheet surface motion ........... 93
2.5.3 Tidal effects on InSAR retrievals over
floating ice ................................... 101
2.6 Ice-sheet surface motion retrieval by speckle
tracking .............................................. 101
2.7 Ice-sheet surface motion retrieval by coherence
tracking .............................................. 108
2.8 Relative strengths and weaknesses of differential
InSAR, coherence tracking, and intensity tracking ..... 109
2.9 Polarimetrie Interferometric SAR (PoI-InSAR) .......... 111
2.10 Developments and outstanding issues ................... 112
2.11 References ............................................ 116
3 Satellite remote sensing of ice sheet parameters and
processes .................................................. 137
3.1 Introduction .......................................... 137
3.2 Improved detection and mapping of surface features .... 137
3.2.1 High-resolution visible-thermal infrared
methods ........................................ 137
3.2.2 Moderate-resolution visible/thermal infrared ... 145
3.2.3 Synthetic aperture radar ....................... 151
3.2.4 The mapping of ice-sheet facies ................ 158
3.3 Detection, mapping and monitoring of ice-sheet
surface melt and refreezing ........................... 164
3.3.1 Visible and thermal infrared techniques ........ 164
3.3.2 Active-microwave techniques .................... 166
3.3.3 Passive-microwave techniques ................... 169
3.3.4 Estimation of surface melt rates ............... 174
3.4 Detection and mapping of changes in ice-sheet
margins ............................................... 175
3.4.1 The collapse of the Larsen Ice Shelf ........... 177
3.4.2 Examples of recent change in the
configuration of other glacier systems ......... 183
3.5 Icebergs .............................................. 186
3.5.1 Iceberg detection and size statistics .......... 186
3.5.2 Monitoring iceberg drift ....................... 199
3.5.3 Measurement of iceberg thickness ............... 206
3.6 Measurement of ice sheet topography/elevation and
change in elevation ................................... 209
3.6.1 Surface elevation from satellite radar
altimetry ...................................... 211
3.6.2 Surface elevation from laser altimetry ......... 229
3.6.3 Improved digital elevation model construction
using satellite image-based photoclinometry .... 234
3.6.4 Surface elevation from SAR interferometry
(InSAR) ........................................ 237
3.7 Accumulation rate ..................................... 240
3.8 Ice velocity, strain rate, and balance velocity/
flux .................................................. 247
3.8.1 Feature tracking ............................... 250
3.8.2 SAR interferometry and ice velocity ............ 257
3.8.3 Balance velocities and fluxes .................. 265
3.8.4 Strain rates ................................... 268
3.8.5 Detection of variability in ice flow and
surge behavior ................................. 271
3.8.6 Ice shelf buttressing, and the impact of ice
shelf removal on outlet glaciers ............... 274
3.9 Tidal displacement of ice shelves and glacier
tongues ............................................... 276
3.10 Grounding-line (zone) detection and monitoring ........ 279
3.11 Estimates of ice discharge flux and basal melt/
freeze rates .......................................... 281
3.12 The measurement of changes in ice mass by satellite
gravity sensors ....................................... 288
3.13 The radar sounding of ice sheets from space ........... 289
3.14 Ice-sheet surface temperature ......................... 291
3.14.1 Thermal infrared techniques .................... 292
3.14.2 Passive-microwave techniques ................... 295
3.15 Ice sheet surface albedo .............................. 299
3.16 Grain size, impurity content, and surface to near-
surface characteristics ............................... 309
3.16.1 Snow-grain size and impurity content ........... 309
3.16.2 Changes in snow/firn characteristics inferred
from passive-microwave data .................... 312
3.16.3 Ice sheet roughness characteristics and proxy
wind measurements .............................. 315
3.16.4 Active-microwave remote sensing of ice-sheet
surface and near-surface characteristics ....... 318
3.17 Conclusions ........................................... 321
3.18 References ............................................ 323
Appendix ...................................................... 387
Index ......................................................... 397
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