Motion of Glaciers, Sea Ice, and Ice Shelves in Canisteo Peninsula, West Antarctica Observed by 4-Pass Differential
Interferometric SAR Technique
Hyangsun Han and Hoonyol Lee
Kangwon National University, KOREA
ContentsIntroduction
Study Area and Data
Method
Analysis of Differential Interferogram
Conclusion
IntroductionImportance of POLAR REGION
Glaciers, Sea Ice, and Ice Shelves are closely related to the Global Warming and Sea Level RisingThe motion of glaciers and the degradation of sea ice and ice shelves in the Antarctic are being acceleratedLarge changes have been observed in the West Antarctica
Usefulness of Synthetic Aperture Radar (SAR) for the polar researchSAR is not affected solar radiation or atmosphere conditionsDifferential SAR interferometry technique is useful in extracting the surface displacement of glaciers, sea ice, and ice shelves
IntroductionObjective
Extraction of interferometric phases from ERS-1/2 tandem pairs of Canisteo Peninsula, West AntarcticaAnalysis of the motion of glaciers, sea ice, ice shelves, and their kinematic interactions by using 4-pass DInSAR technique
Study Area
Radarsat-1 mosaic image of the Antarctic
Canisteo Peninsula near Amundsen Sea in West Antarctica(100 km×100 km)
Study Area
Canisteo Peninsula near Amundsen Sea in West Antarctica(100 km×100 km)
Center Location :73˚ 57´ 46˝ S / 101˚ 53´ 26˝ W
Ice shelves and small islands around the peninsulaSeveral glaciers of different size on the coastal areaCrevasses between the peninsula and ice shelves
Geocoded ERS-1 SAR image of the study area (1995/10/21, 100 km×100 km)
Azimuth
Range
Amundsen Sea
Canisteo Peninsula
Ice shelfIce shelf
ERS-1/2 SAR DataERS-1 SAR1995/10/21
ERS-1 SAR1996/03/09
ERS-2 SAR1995/10/22
ERS-2 SAR1996/03/10
Azimuth Range Azimuth Range
Azimuth Range Azimuth Range
ERS-1/2 SAR Data
Track Orbit(ERS-1/2)
Date(ERS-1, ERS-2)
*Bperp(m) *Ha (m)
278
22310/26371995/10/21
1995/10/2240.0 243.2
24314/46411996/03/09
1996/03/10152.4 63.9
*Bperp: Perpendicular baseline*Ha: Height ambiguity
MethodSAR Interferometry (InSAR)
Using the difference of phases between two or more SAR imagesWidely used to extract topography and deformation of surface
Differential SAR Interferometry (DInSAR)Extracting displacement of surface by removing topographic phases2-pass (accurate DEM is nedded), 3-pass, and 4-pass DInSARApplication: measuring displacements by earthquake and volcano, ground subsidence, motion pattern of glaciers and ice shelves, etc.
4-Pass DInSARFor the 2-pass DInSAR
An accurate DEM is neededRadarsat-1 Mapping Project (RAMP) DEM is the best for the Antarctic
RAMP DEM is not accurate enough to apply 2-pass DInSARThe horizontal resolution of 400 m in the study area
Use of 4-pass DInSAR technique4-pass DInSAR can extract surface displacement without DEMUse of two interferogramsOne interferogram is used to estimate the topographic phases (topo-pair) to be subtracted from the other interferogram containing the phases of deformation (diff-pair)
Interferogram GenerationGeneration of SLC image
Offsets estimation
Co-registration
Generation of multi-look interferogram
Estimation of interferometric baseline
Generation of earth-flattened interferogram
Decision of topo-pair and diff-pairOctober 21-22, 1995
Perpendicular baseline: 40 mHeight ambiguity: 243.2 mThe springtime of the AntarcticMany changes occur over the surface
March 9-10, 1996Perpendicular baseline: 152 mHeight ambiguity: 63.9 mInterferogram well shows topographic phases
Weaknesses and limitationsMore changes occur in March than October due to the high temperatureSome phases of deformation in the topo-pair interferogramA gap of 5 months between two pairs
Diff-pair
Topo-pair
Erath-Flattened InterferogramThe earth-flattened interferogram extracted from diff-pair
The positive fringes on glaciers and sea ice
Many circular fringes on ice shelves
No fringes on some sea ice due to large movement of sea ice during a day
Some topographic phases
Erath-Flattened InterferogramThe earth-flattened interferogram extracted from topo-pair
The topographic phases are well displayed
No interferometric phases in the sea
Some fringes by surface displacement
Differential InterferogramThe differential interferogram
The major parts of topography were removed
Fringes by deformation were shown in the differential interferogram
One fringe (from purple to yellow, cyan, and purple again) represents the change of 2.83 cm from radar to ground
Analysis of Differential Interferogram
Interaction between glaciers and sea ice
The largest glacier in Canisteo Peninsula
Glacier moves toward the sea ice
The sea ice shows up rise interferometric phases
The pushing glacier gave repulsive force to sea ice which type is land-fast ice
The land-fast ice showed the structure of anticline
Interaction between glaciers and sea ice
Other glaciers in Canisteo Peninsula
Glacier rapidly moved to land-fast ice
The interferometic phases of the adjoining land-fast ice indicated the up rise of ice surface
Analysis of Differential Interferogram
Interaction between glaciers and sea ice
Glacier and sea ice indicated the interferometric phase of the same direction
Sea ice was moved by the motion of glacier in the same horizontal direction towards the sea
The sea ice is similar to the land-fast ice
The ice type is the land-fast ice weakly harnessed to sea bottom or pack ice not harnessed at all
Analysis of Differential Interferogram
Sea ice motion and type
Sea ice showed rapid motion by ocean tide → Pack Ice
The land-fast ice indicated a little motion
The sea ice type can be classified
Analysis of Differential Interferogram
Sea ice motion and type
Sea ice showed rapid motion by ocean tide → Pack Ice
The land-fast ice indicated a little motion
The sea ice type can be classified
Analysis of Differential Interferogram
Interferometric phases on ice shelf
Many circular interferometric phases on the ice shlef
They are observed in both the topo-pair and diff-pair interferogram
Seamounts or unidentified islands may be under the bottom of the ice shelf
→ a cause for the motion on the surface of ice shelf
Analysis of Differential Interferogram
ConclusionWe revealed dynamic features of glaciers, sea ice, ice shelves and their interactions by applying 4-pass DInSAR to ERS-1/2 tandem pairs
The upwelling sea ice by repulsive force against the fast motion of glaciers is observed
Sea ice showing the motion in the same direction with the glaciers could be land-fast ice weakly connected to sea bottom or pack ice
We could classify the sea ice type and decide a clear boundary between different ice types
The circular fringes on ice shelves were caused by seamounts or unidentified islands at the bottom of the ice shelves
For more detailed analysis, it is necessary to apply numerical analysis and modeling