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| Titel |
An approach to derive regional snow lines and glacier mass change from MODIS imagery, western North America |
| VerfasserIn |
J. M. Shea, B. Menounos, R. D. Moore, C. Tennant |
| 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 ; 7, no. 2 ; Nr. 7, no. 2 (2013-04-18), S.667-680 |
| Datensatznummer |
250017958
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| Publikation (Nr.) |
 copernicus.org/tc-7-667-2013.pdf |
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| Zusammenfassung |
| We describe a method to calculate regional snow line elevations and annual
equilibrium line altitudes (ELAs) from daily MODIS imagery (MOD02QKM) on
large glaciers and icefields in western North America. An automated cluster
analysis of the cloud-masked visible and near-infrared bands at 250 m
resolution is used to delineate glacier facies (snow and ice) for ten
glacierized regions between 2000–2011. For each region and season, the
maximum observed value of the 20th percentile of snow-covered pixels
(ZS(20)) is used to define a regional ELA proxy (ELAest). Our
results indicate significant increases in the regional ELA proxy at two
continental sites (Peyto Glacier and Gulkana Glacier) over the period of
observation, though no statistically significant trends are identified at
other sites. To evaluate the utility of regional ELA proxies derived from
MOD02QKM imagery, we compare standard geodetic estimates of glacier mass
change with estimates derived from historical mass balance gradients and
observations of ZS(20) at three large icefields. Our approach yields
estimates of mass change that more negative than traditional geodetic
approaches, though MODIS-derived estimates are within the margins of error at
all three sites. Both estimates of glacier mass change corroborate the
continued mass loss of glaciers in western North America. Between 2000 and
2009, the geodetic change approach yields mean annual rates of surface
elevation change for the Columbia, Lillooet, and Sittakanay icefields of
−0.29 ± 0.05, −0.26 ± 0.05, and
−0.63 ± 0.17 m a−1, respectively. This study provides a new
technique for glacier facies detection at daily timescales, and contributes
to the development of regional estimates of glacier mass change, both of
which are critical for studies of glacier contributions to streamflow and global sea level rise. |
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