Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, Nepal
This study presents volume and mass changes of seven (five partially debris-covered, two debris-free) glaciers in the upper Langtang catchment in Nepal. We use a digital elevation model (DEM) from 1974 stereo Hexagon satellite data and seven DEMs derived from 2006–2015 stereo or tri-ste...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-09-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/10/2075/2016/tc-10-2075-2016.pdf |
| _version_ | 1828420247147773952 |
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| author | S. Ragettli S. Ragettli T. Bolch T. Bolch F. Pellicciotti |
| author_facet | S. Ragettli S. Ragettli T. Bolch T. Bolch F. Pellicciotti |
| author_sort | S. Ragettli |
| collection | DOAJ |
| description | This study presents volume and mass changes of seven (five partially debris-covered, two debris-free) glaciers in the upper Langtang
catchment in Nepal. We use a digital elevation model (DEM) from 1974 stereo
Hexagon satellite data and seven DEMs derived from 2006–2015 stereo or
tri-stereo satellite imagery (e.g., SPOT6/7). The availability of multiple
independent DEM differences allows the identification of a robust signal and narrowing down of the uncertainty about recent volume changes. The volume changes calculated over several multiyear periods between 2006 and 2015 consistently indicate that glacier thinning has accelerated with respect to the period 1974–2006. We calculate an ensemble-mean elevation change rate of
–0.45 ± 0.18 m a<sup>−1</sup> for 2006–2015, while for the period 1974–2006 we compute a rate of −0.24 ± 0.08 m a<sup>−1</sup>. However,
the behavior of glaciers in the study area is heterogeneous, and the presence
or absence of debris does not seem to be a good predictor for mass balance
trends. Debris-covered tongues have nonlinear thinning profiles, and we show
that recent accelerations in thinning correlate with the presence of
supraglacial cliffs and lakes. At stagnating glacier areas near the glacier
front, however, thinning rates decreased with time or remained
constant. The April 2015 Nepal earthquake triggered large avalanches in the
study catchment. Analysis of two post-earthquake DEMs revealed that the
avalanche deposit volumes remaining 6 months after the earthquake are
negligible in comparison to 2006–2015 elevation changes. However, the
deposits compensate about 40 % the mass loss of debris-covered tongues of
1 average year. |
| first_indexed | 2024-12-10T15:08:38Z |
| format | Article |
| id | doaj.art-63eb0698db0e428f91448279980bdff8 |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-12-10T15:08:38Z |
| publishDate | 2016-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-63eb0698db0e428f91448279980bdff82022-12-22T01:43:59ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242016-09-01102075209710.5194/tc-10-2075-2016Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, NepalS. Ragettli0S. Ragettli1T. Bolch2T. Bolch3F. Pellicciotti4Institute of Environmental Engineering, ETH Zürich, Zurich, SwitzerlandUniversity of Zurich, Department of Geography, Zurich, SwitzerlandUniversity of Zurich, Department of Geography, Zurich, SwitzerlandInstitute for Cartography, Technische Universität Dresden, Dresden, GermanyNorthumbria University, Department of Geography, Newcastle upon Tyne, UKThis study presents volume and mass changes of seven (five partially debris-covered, two debris-free) glaciers in the upper Langtang catchment in Nepal. We use a digital elevation model (DEM) from 1974 stereo Hexagon satellite data and seven DEMs derived from 2006–2015 stereo or tri-stereo satellite imagery (e.g., SPOT6/7). The availability of multiple independent DEM differences allows the identification of a robust signal and narrowing down of the uncertainty about recent volume changes. The volume changes calculated over several multiyear periods between 2006 and 2015 consistently indicate that glacier thinning has accelerated with respect to the period 1974–2006. We calculate an ensemble-mean elevation change rate of –0.45 ± 0.18 m a<sup>−1</sup> for 2006–2015, while for the period 1974–2006 we compute a rate of −0.24 ± 0.08 m a<sup>−1</sup>. However, the behavior of glaciers in the study area is heterogeneous, and the presence or absence of debris does not seem to be a good predictor for mass balance trends. Debris-covered tongues have nonlinear thinning profiles, and we show that recent accelerations in thinning correlate with the presence of supraglacial cliffs and lakes. At stagnating glacier areas near the glacier front, however, thinning rates decreased with time or remained constant. The April 2015 Nepal earthquake triggered large avalanches in the study catchment. Analysis of two post-earthquake DEMs revealed that the avalanche deposit volumes remaining 6 months after the earthquake are negligible in comparison to 2006–2015 elevation changes. However, the deposits compensate about 40 % the mass loss of debris-covered tongues of 1 average year.https://www.the-cryosphere.net/10/2075/2016/tc-10-2075-2016.pdf |
| spellingShingle | S. Ragettli S. Ragettli T. Bolch T. Bolch F. Pellicciotti Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, Nepal The Cryosphere |
| title | Heterogeneous glacier thinning patterns over the last 40 years in Langtang
Himal, Nepal |
| title_full | Heterogeneous glacier thinning patterns over the last 40 years in Langtang
Himal, Nepal |
| title_fullStr | Heterogeneous glacier thinning patterns over the last 40 years in Langtang
Himal, Nepal |
| title_full_unstemmed | Heterogeneous glacier thinning patterns over the last 40 years in Langtang
Himal, Nepal |
| title_short | Heterogeneous glacier thinning patterns over the last 40 years in Langtang
Himal, Nepal |
| title_sort | heterogeneous glacier thinning patterns over the last 40 years in langtang himal nepal |
| url | https://www.the-cryosphere.net/10/2075/2016/tc-10-2075-2016.pdf |
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