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Ice Sheets and Landsat. Robert Bindschadler NASA Goddard SFC. Some Cold Hard Facts. Ice Sheets 10% of land area is ice covered Sea Level Ice sheets hold 70 meters of sea level equivalent Variation of Sea Level -125 meters to +5 meters Rate of Sea Level Change

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Ice sheets and landsat l.jpg

Ice Sheets and Landsat

Robert Bindschadler

NASA Goddard SFC


Some cold hard facts l.jpg
Some Cold Hard Facts

  • Ice Sheets

    • 10% of land area is ice covered

  • Sea Level

    • Ice sheets hold 70 meters of sea level equivalent

  • Variation of Sea Level

    • -125 meters to +5 meters

  • Rate of Sea Level Change

    • 3 mm/yr. (50% rate increase in last decade)


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Landsat Image Mosaic of Antarctica

  • 1131 Landsat scenes (+ 2 ASTER)

  • circa 2000

  • Summer 2007 completion date


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Landsat tells Glaciologists about:

  • Coastal change

  • Calving

  • Surface velocity

  • Elevation

    • Change in elevation


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Ice Measurements with Landsat

  • Coastal change

  • Calving

  • Surface velocity

  • Elevation

    • Change in elevation


Elevation l.jpg
Elevation?

  • Ice sheet surface:

    • Nearly constant albedo

    • Diffusive reflector

  • Image brightness becomes a slope map (in direction of solar illumination)

    • +1 DN = + 8 cm across a 15-m pixel

  • Slopes used to interpolate elevations between control elevation profiles


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100 km

Checking Digital Elevation Models with Shaded Relief Images

ICESat Digital Elevation Model

ICESat elevation precision = +20 cm


Landsat gives the right answer l.jpg

ICESat tracks

Image-based slopes can provide an accurate interpolation

Landsat gives the “right” answer

ICESat DEM

Landsat-7

30 km

30 km


New science l.jpg

Elevation range 2003-06 (m)

0 9m

MOA (NSIDC)

New Science

Conway Ridge

Mercer Ice Stream (A)

Repeat-pass elevation changes are revealing subglacial water movement

Whillans Ice Stream (B)

Engelhardt Ridge



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Image Contributions to New Science of Subglacial Hydrology

  • Image-derived slopes to adjust elevation to reference track

    • Repeat tracks are close and parallel, but NOT exact repeats

    • Spatial (cross-track) elevation differences can be confused with temporal elevation differences

  • Image differencing to show spatial extent

Observed Ground Track Footprint Location:

Reference Ground Track:


1 image based profile adjustment l.jpg

Adjusted profiles shifted along track

Elevation (m)

No adjustment

Latitude

Elevation (m)

Latitude

1. Image-based Profile Adjustment

Sun

30o

reference profile

measured profiles


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Adjustment to Reference Track

Elevation Difference (m)


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Image Differences

2. Image Differencing

Images

Radiometric resolution is critical to success—8-bit data won’t suffice


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Conclusions

  • Landsat data continue to be used in new, innovative ways by glaciologists

  • The most important LDCM enhancement for ice-sheet research is improved radiometric resolution

    • 8-bit is inadequate

    • 12-bit is required


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