TERRASAR-X OBSERVATIONS OF ANTARCTIC OUTLET GLACIERS IN THE ROSS SEA SECTOR Kenneth Jezek 1 , Wael Abdel Jaber 2,3 , Dana Floricioiu 2 1 Byrd Polar Research Center, Ohio State University, Columbus, OH, USA 2 German Aerospace Center (DLR), Remote Sensing Technology Institute, Oberpfaffenhofen, Germany 3 Technical University of Munich, Remote Sensing Technology, Munich, Germany
Ice surface velocity:
Crucial parameter for mass balance estimation of glaciers and ice sheets.
Fundamental factor to establish the state of glaciers and predict sea level variations.
Interferometric SAR data requirements for ice surface velocity:
Short repeat pass time span for high frequency SAR (C-, X-band) to avoid decorrelation
Left looking capabilities for areas South of 80°S. Available for: Radarsat-1/2 (1997/2008 campaigns), COSMO-SkyMed and TerraSAR-X.
Antarctic ice velocity: ERS-1/2 (1996), RSAT-1 (1997, 2000) [Rignot et al, 2008]. Status 2000, update ongoing!
2nd satellite TDX-1 (launched for TanDEM-X mission) operational since Oct. 2010 (for TerraSAR-X mission)
Left and right imaging capabilities
Various imaging modes and incidence angles
Spatial resolution in stripmap mode, single look complex data: < 3 m in slant range and azimuth
Very accurate orbit estimation
11 days repeat pass cycle
During the 2007-2008 International Polar Year (IPY) DLR initiated the acquisition and processing of interferometric TerraSAR-X data over important sectors of the polar ice sheets.
TSX-1 TSX-1 & TDX-1
TerraSAR-X acquisition plan over the Ross Sea Sector of Antarctica
Swath width: 30 km
Resolution: <3 m
Nimrod Beardmore 80°S Byrd Shackleton Amundsen Scott Van der Veen and Whillans Kamb Bindshadler Crary Reedy MacAyeal Ross Ice Shelf Courtesy: Katy Farness, OSU N
Nimrod Glacier (82.6°S, 160.7°E)
Two main tributaries: Nimrod and Marsh Glacier
Length: 135 km
Glacier in balanced state: mass balance 0.88 ± 0.39 Gt/a (after L. Stearns, 2010, in press)
Ross Ice Shelf Marsh Gl. Kon-Tiki Nunatak TerraSAR-X image (2009) Nimrod Gl. flowing around the Kon-Tiki Nunatak TerraSAR-X mosaic (2009) http://vervoortantarctica.blogspot.com/ N az rg
Byrd Glacier (80.5°S, 157.5°E)
One of the largest catchment basins in Antarctica (1 101 725 km 2 )
Fjord length: 136 km, width: 24 km
Ice export into the Ross Ice Shelf: 22.32 ± 1.72 Gt/a
Byrd Gl. view upstream from Mt. Quackenbush TerraSAR-X mosaic (2010) Ross Ice Shelf az rg N
Ice velocity derivation by speckle tracking
Displacement for each patch is obtained from the position of the peak of the incoherent cross-correlation function (CCF).
A regular grid of patches with size of 256 2 pixels and 50% overlap is used.
Input: Stripmap geocoded images: 1.25 m pixel spacing, ~1.3 looks, <3 m sp. resolution.
Correlation between repeat pass images is given by the speckle pattern (smooth, highly coherent areas) or by the image texture (e.g. crevasses).
NIMROD, Pair 000 Byte per pixel of input: 2 Master / Slave patch mean: 189.45242 186.07397 Patch size= 256 Crop size= 32 Oversampling factor=16 Central pixel on sras image (origin is LL), x: 9000, y: 32472 UTM Coords (easting - northing) [m]: 2324900.000 11137160.000 Displacement before interpolation: 1 -2 [pix] peakwidth x/y = 14 14 Corr. coeff: 0.52106100 Accuracy [pixel x/y] = 0.049388256 0.049388256 Corr. coeff: 0.52106100 Accuracy [meter x/y/abs] = 0.061735320 0.061735320 0.087306927 SNR1: 13.374758 ( 11.262859 dB) SNR2: 12.374988 ( 10.925448 dB) CC function - Mean: 269.38077 Min: 0.00500107 Max: 3602.90 Oversampled Max: 3613.71 Displacement after interpolation (+ is East and North): 0.812500 -2.06250 [pix] 1.01562 -2.57812 [m] displacement in 11 days [pix]: 2.21677 displacement in 11 days [m]: 2.77096 angle of displacement: 291.501 -68.4986 (Deg, from East, anti-ckw is positive) displacement /day [m]: 0.251906 displacement /year [m]: 91.9455 NIMROD, pair 000 Byte per pixel of input: 2 Master / Slave patch mean: 184.13252 183.36140 Patch size= 256 Crop size= 32 Oversampling factor=16 Central pixel on sras image (origin is LL), x: 8280, y: 12492 UTM Coords (easting - northing) [m]: 2324000.000 11112185.000 Displacement before interpolation: 0 -1 [pix] peakwidth x/y = 4 4 Corr. coeff: 0.38275356 Accuracy [pixel x/y] = 0.020792813 0.020792813 Corr. coeff: 0.38275356 Accuracy [meter x/y/abs] = 0.025991016 0.025991016 0.036756848 SNR1: 90.573555 ( 19.570014 dB) SNR2: 89.576592 ( 19.521945 dB) CC function - Mean: 10.541570 Min: 0.000357389 Max: 954.787 Oversampled Max: 958.024 Displacement after interpolation (+ is East and North): -0.125000 -1.06250 [pix] -0.156250 -1.32812 [m] displacement in 11 days [pix]: 1.06983 displacement in 11 days [m]: 1.33728 angle of displacement: 263.290 -96.7098 (Deg, from East, anti-ckw is positive) displacement /day [m]: 0.121571 displacement /year [m]: 44.3735 CCF: slow and smooth area NIMROD, Pair 020 Byte per pixel of input: 2 Master / Slave patch mean: 246.90729 245.42989 Patch size= 256 Crop size= 32 Oversampling factor=16 Central pixel on sras image (origin is LL), x: 13356, y: 21384 UTM Coords (easting - northing) [m]: 2274750.000 11211163.750 Displacement before interpolation: -13 -8 [pix] peakwidth x/y = 18 33 Corr. coeff: 0.12337598 Accuracy [pixel x/y] = 0.31180419 0.57164101 Corr. coeff: 0.12337598 Accuracy [meter x/y/abs] = 0.38975523 0.71455126 0.81393652 SNR1: 11.534828 ( 10.620111 dB) SNR2: 10.534860 ( 10.226288 dB) CC function - Mean: 268.90243 Min: 0.000812531 Max: 3101.74 Oversampled Max: 3113.25 Displacement after interpolation (+ is East and North): -12.7500 -7.87500 [pix] -15.9375 -9.84375 [m] displacement in 11 days [pix]: 14.9859 displacement in 11 days [m]: 18.7324 angle of displacement: 211.701 -148.299 (Deg, from East, anti-ckw is positive) displacement /day [m]: 1.70295 displacement /year [m]: 621.576 CCF: fast and crevassed area 11 days repeat pass 11 days repeat pass CCF: slow and crevassed area W-E cut N-S cut 0.156 m 1.328 m R: master (m) G: slave (s) B: (m+s)/2 W-E cut N-S cut 15.936 m 9.844 m R: master (m) G: slave (s) B: (m+s)/2
Speckle tracking: TerraSAR-X velocity map detail Patch size: 256 2 pixel (320 2 m 2 ) Patch distance: 128 pixel (160 m) 0 500 m 0.0 2.5 [m/d] 2 m/d
Speckle tracking (ST) accuracy with TerraSAR-X
Absolute accuracy of velocity estimate is affected by:
Atmospheric path delay
Solid earth tides
Orbit estimation and timing errors
Relative accuracy of an individual motion vector depends on:
Correlation coefficient γ
Patch size N
Shape of the cross-correlation function
Estimated empirically for highly coherent smooth areas  . ~10 times lower than absolute accuracy
 R. Bamler, M. Eineder, “Accuracy of differential shift estimation by correlation and split-bandwidth interferometry for wideband and delta-k SAR systems,“ IEEE Geoscience and Remote Sensing Letters, Vol. 2, No. 2, April 2005 σ CR : Cramer-Rao bound More in presentation: „Glacier flow and topography measurements with TerraSAR-X And TanDEM-X “ by Michael Eineder (session TH4.T02.5, Room 1, 4:40 PM) σ rg = 0.2 m, σ az =0.1 m
Geophysical glacier properties derived from velocity profiles
Longitudinal strain rate
Obtained from the filtered longitudinal velocity profile applying :
Computed for points of crevasses initiation (according to amplitude image)
Assumption: only longitudinal component of strain is present on glacier‘s center line
Application of Glen‘s flow law of ice + „von Mises“ and „Griffith‘s“ failure criteria , leads to:
 Forster, R., Rignot, E., Isacks, B., Jezek, K., „Interferometric radar observation of Glaciers Europa and Penguin, Hielo Patagónico Sur, Chile“, Journal of Glaciology, Vol. 45, No. 150, 1999 Δ v : velocity variation between two points Δ d : distance between two points ( Δ d ≈ 63 m ) A : flow parameter, depends on temperature, impurities and crystal orientation of ice ( A = 1.61 ∙10 -9 yr -1 kPa -3 )
23 Stripmap pairs, coverage: ~35 000 km 2
Acquired: Oct. - Nov. 2009
Nimrod Glacier: ice surface velocity from TerraSAR-X Ross Ice Shelf Plug like shape: strong side drag km 0 30 N Marsh Gl. Kon-Tiki Nunatak GL 0.0 2.5 [m/d] (L) (T) (T) SE NW 255.5 219.0 182.5 146.0 109.5 73.0 36.5 0.0 [m/a] (L) Ice flow GL 912.5 730.0 547.5 365.0 182.5 0.0 [m/a]