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| Titel |
Monitoring ice shelf velocities from repeat MODIS and Landsat data – a method study on the Larsen C ice shelf, Antarctic Peninsula, and 10 other ice shelves around Antarctica |
| VerfasserIn |
T. Haug, A. Kääb, P. Skvarca |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 4, no. 2 ; Nr. 4, no. 2 (2010-05-06), S.161-178 |
| Datensatznummer |
250001645
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| Publikation (Nr.) |
 copernicus.org/tc-4-161-2010.pdf |
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| Zusammenfassung |
| We investigate the velocity field of the Larsen C ice shelf, Antarctic
Peninsula, over the periods 2002–2006 and 2006–2009 based on repeat optical
satellite data. The velocity field of the entire ice shelf is measured using
repeat low resolution MODIS data (250 m spatial resolution). The
measurements are validated for two ice shelf sections against repeat medium
resolution Landsat 7 ETM + pan data (15 m spatial resolution).
Horizontal surface velocities are obtained through image matching
using both orientation correlation operated in the frequency domain and normalized crosscorrelation
operated in the spatial domain, and the two methods compared. The uncertainty in the
displacement measurements turns out to be about one fourth of the pixel size for the MODIS
derived data, and about one pixel for the Landsat derived data. The
difference between MODIS and Landsat based speeds is −15.4 m a−1
and 13.0 m a−1, respectively, for the first period for the two
different validation sections on the ice shelf, and −26.7 m a−1 and
27.9 m a−1 for the second period for the same sections. This leads
us to conclude that repeat MODIS images are well suited to measure ice shelf
velocity fields and monitor their changes over time. Orientation
correlation seems better suited for this purpose because it
produces fewer mismatches, is able to match images with regular
noise and data voids, and is faster. Since it can match images
with regular data voids it is possible to match Landsat 7 ETM+
images even after the 2003 failure of the Scan Line Corrector (SLC off) that
leaves significant image stripes with no data. Image matching based on the
original 12-bit radiometric resolution MODIS data produced slightly better
results than using the 8-bit version of the same images. Streamline
interpolation from the obtained surface velocity field on Larsen C indicates
ice travel times of up to 450 to 550 years between the inland boundary and the
ice shelf edge. In a second step of the study we test our method successfully
on 10 other ice shelves around Antarctica demonstrating that the approach
presented could in fact be used for large scale monitoring of ice shelf
dynamics. |
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