Cryospheric%20Applications%20of%20Synthetic%20Aperture%20Radar

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Cryospheric Applications of Synthetic Aperture
Radar
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Climate Change and Variability Research for
2015-2020

• If current climate projections are correct, then
  climate changes of the next ten to twenty years
  will significantly and noticeably impact human
  activities. This impact will shift research from
  climate change detection to research on the
  predictive capability necessary to protect life
  and property, promote economic vitality, enable
  environmental stewardship, and support a broad
  range of decision-makers.
• 
  
  (NRC Decadal Survey, Climate Panel)

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Climate Research 2005-2015

• Realization of future climate change forces our
  decadal vision to extend outside of the current
  state of the science in several ways
• Climate change research will be increasingly tied
  to improving predictive capabilities
• The drive to create more comprehensive models
  will grow significantly
• The family of forecasting products will grow
  substantially.
• The tie between climate research and societal
  benefit will emphasize regional or higher spatial
  resolution climate prediction.
• The connection between climate and specific
  impacts on natural and human systems will require
  a more comprehensive approach to environmental
  research.

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Earths Cold Regions and Global Climate

• Earths cold regions and their icy cover are well
  documented indicators of climate change
• High latitude/elevation processes are important
  drivers in climate change
• Climatologically we are in unfamiliar territory,
  and the worlds ice cover is responding
  dramatically.

ERS/AMM/MAMM
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Science Challenges in Cryospheric Research

• Ice Sheets Understand the polar ice sheets
  sufficiently to predict their contribution to
  global sea level rise.
• Sea ice Understand sea ice sufficiently to
  predict its response and influence on global
  climate change and biological processes
• Seasonal snow cover measure how much water is
  stored as seasonal snow and document its
  variability
• Glaciers Understand glaciers and ice caps in
  the context of their hydrologic and biologic
  systems and their contributions to global
  processes including sea level rise
• Ice and Atmosphere Understand the interactions
  between the changing polar atmosphere and the
  changes in sea ice, glacial ice, snow, and
  surface melt.
• Permafrost Map extent and variability
• As a system Understand how changes in the
  cryosphere affect human activity

Jacobshavn Fjord, K. Farness, 5/05
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Glaciers and Ice Sheets Grand Challenges

• Understand the polar ice sheets sufficiently to
  predict their response to global climate change
  and their contribution global sea level rise

• What is the mass balance of the polar ice sheets?
• How will the mass balance change in the future?

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Reservoirs of Fresh Water
Ice Thickness Average 2500m Maximum 4500m
Fresh Water Resource Polar Ice Sheets and
Glaciers 77 East Antarctica 80 West
Antarctica 11 Greenland 8 Glaciers
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National Geographic Magazine
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Retreat of Antarctic Ice Sheet and Sea Level Rise
Consequences
Causes
Sea level rise 6 m
Collapse of West Antarctic Ice Sheet
Sea level rise 73 m
Melting Entire Antarctic Ice Sheet
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Solving the ice sheet problem Mapping, Surface
Properties, Dynamics and Mass Balance
Net Accumulation
SAR contributes new knowledge about surface
structure, ice sheet extent, and surface
velocity.
Ice In
Side Drag
Ice out
driving stress
Surface Topo
MAMM InSAR Velocity, Lambert Glacial Basin, 2000
basal drag
Bottom Topo
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Mass Balance

• Ice sheet mass balance is described
• by the mass continuity equation

Altimeters
Act/Pass. Microwave
InSAR
No spaceborne technique available
Evaluations of the left and right hand sides of
the equation will yield a far more complete result
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Ice Dynamics and Prediction
Force Balance Equations
No Sat. Cover
Satellite Altimetry
Basal Drag, Inferred at best
Terms related to gradients in ice velocity
(InSAR) integrated over thickness
Understanding dynamics coupled with the
continuity equations yields predictions on future
changes in mass balance
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Radarsat-1
Synthetic Aperture Radar Overview
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SAR Imaging Characteristics

• Range Res pulse width
• Azimuth L / 2
• ( 25 m resolution with 3 looks)

l
Platform
SEASAT 23 cm HH SIR 23, 5.7, 3.1 cm
pol JERS-1 23 cm HH ERS-1/2 5.7 cm
VV Radarsat-1 5.7 cm HH ALOS 23 cm
pol Radarsat-2 5.7 cm pol TerraSAR-X 3.1 cm pol
l 0 e r
penetration depth
2 p e r
(several meters even at C-band)
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Coherent Properties of SAR

• Interferometric SAR measures surface elevation
  and surface displacement

b
Velocity
q
Topo
a
z r sin( cos-1 f l / 2 p b - q) dz ( df )
r l / 4p b
x
z
r
x f l / (4p sinb)
Fringes are determined by baseline, surface
slope, flow speed and flow direction!
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Coherent Properties of SAR (cont.)

• Phase coherence can be used for change detection

lt a0 a1 gt
0 and 1 denote observations at successive times
mean values computed over many (20 x 4) pixels
r
lt a0 2 gt lt a1 2 gt
Decorrelation occurs because of 1) thermal
noise 2) baseline decorrelation 3)
decorrelation of the scattering centers.
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Acquisition Planning
Instrument Selection Target selection and
priority Minimize onboard resources Minimize
downlink requirements Conflict resolution
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Geocoding
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RAMS-1 Processing System
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RADARSAT-1 Image Mosaics of Antarctica
2000
1997
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Fine Beam Single Look Mini-Mosaics
MAMM Mini-Mosaic
Orthorectified MAMM Frame
AMM-1 Tile
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Ice Margin Mapping
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• Ice margin mapping algorithm

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Histograms for Local Dynamic Thresholding
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Greenland Application (ice, rock, ocean)
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AMM-1
MAMM Blocks to date
Liu and Jezek
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1997
Composite Ice Shelves in the Southeastern
Antarctic Peninsula Reclassifying ice tongue and
fast ice covered areas as composite ice tongues
reduces peninsula ice shelf area by 3500 km2 The
composite shelf shown here retreated by 1200 km2
between 1997 and 2000
2000
Jezek, Liu, Thomas, Gogineni, and Krabill
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Coastline derived from 1963 DISP Imagery

• Accuracy
• Image positional accuracy 2 pixels (200 m)
• Relative accuracy of extracted coastline 1 pixel
• Absolute geographical accuracy of extracted
  coastline 200 m 500 m (worst case with light
  cloud cover)

(Kim and Jezek)
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Advance and Retreat of Ice Shelves
0.8 decrease in Ice Shelf extent between 1963
and 1997
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Continuing the Time Series with MODIS
Ross Ice Shelf Margin 1963 (yellow), 1983/89
(green), 1997 (blue), 2000 (red) coastlines
draped over the 2003/04 MOSDIS mosaic.
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Short-Term Change Detection Coherence over 24
days
MAMM Coherence Map April, 05
Equivalent range of i and j Fine beam 9 x
9 Standard beams 6 x 24
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Shear Margins and Grounding lines
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Dry Valleys
Lake Bonney
Royal Society Range
Bowers Piedmont Gl.
Kukri Hills
Taylor Valley
Ferrar Gl.
Lake Fryxell
Wilson Piedmont Gl.
AMM-1 - Coherence
1997 SAR Mosaic
MAMM - Coherence
Beam S2 Look angle 24.265
Beam S2 Look angle 28.152
Coherence variations observable on Ferrar Glacier
that are absent in the power image. Lakes are
contrast reversed
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Dome C
MAMM - Coherence
1997 SAR image
AMM-1 - Coherence
Snow dunes and distinctly different, small scale
(10 km) coherence patterns in AMM-1 and MAMM data
collected over the interior East Antarctic Ice
Sheet. Origin is undetermined..
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Decorrelation Stripes
1997 SAR Mosaic
MAMM - coherence
AMM-1 - coherence
Beam S2 Baseline 177 m Look angle 24.265
Beam S2 Baseline 149.32 m Look angle 28.515
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Decorrelation Stripes with the Prevailing
Windfield Vector
AMM-1 SAR Mosaic Resolution 100m
AMM-1 Coherence Mosaic Resolution 200m
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Geophysical Information From Backscatter
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Accumulation Rate from Backscatter
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Accumulation Rate Model for Greenland
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Accumulation Rates in Greenland
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A Tour of Antarctica from Space