POLAR REMOTE SENSING: ICE SHEETS
1 POLAR ICE SHEETS: INTRODUCTION 1 1 1 THE GLOBAL IMPORTANCE OF POLAR ICE SHEETS 1 10 1 2 ICE-SHEET MASS BALANCE BACKGROUND INFORMATION 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 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, COHER-ENCE TRACKING, AND INTENSITY TRACKING 109 2 9 POLARIMETRIC INTERFEROMETRIC SAR (POL-INSAR) 111 2 10 DEVELOPMENTS AND OUTSTANDING ISSUES 112 2 11 REFERENCES 116 137 3 SATELLITE REMOTE SENSING OF ICE SHEET PARAMETERS AND PROCESSES 137 3 1 INTRODUCTION 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 158 164 REFREEZING 3 3 DETECTION, MAPPING AND MONITORING OF ICE-SHEET SURFACE MELT AND 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 SATEL-LITE IMAGE-BASED PHOTOCLINOMETRY 234 3 6 4 SURFACE ELEVATION FROM SAR INTERFEROMETRY (INSAR) 237 3 7 ACCUMULATION RATE 240 247 250 3 8 ICE VELOCITY, STRAIN RATE, AND BALANCE VELOCITY/FLUX 3 8 1 FEATURE TRACKING 3 8 2 SAR INTERFEROMETRY AND ICE VELOCITY 257 BALANCE VELOCITIES AND FLUXES 265 3 8 3 3 8 4 STRAIN RATES 268 DETECTION OF VARIABILITY IN ICE FLOW AND SURGE BEHAVIOR 271 3 8 5 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 MEAS-UREMENTS 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