Contrasting thinning patterns between lake- and land-terminating glaciers in the Bhutanese Himalaya
<p>Despite the importance of glacial lake development in ice dynamics and glacier thinning, in situ and satellite-based measurements from lake-terminating glaciers are sparse in the Bhutanese Himalaya, where a number of proglacial lakes exist. We acquired in situ and satellite-based observatio...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-10-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/13/2733/2019/tc-13-2733-2019.pdf |
| Summary: | <p>Despite the importance of glacial lake development in ice dynamics and glacier thinning, in situ and satellite-based measurements from lake-terminating glaciers are sparse in the Bhutanese Himalaya, where a number of proglacial lakes exist. We acquired in situ and satellite-based observations across lake- and land-terminating debris-covered glaciers in the Lunana region, Bhutanese Himalaya. A repeated differential global positioning system survey reveals that thickness change of the debris-covered ablation area of the lake-terminating Lugge Glacier (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">4.67</mn><mo>±</mo><mn mathvariant="normal">0.07</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="e470bb8103c0d2dcc27fd5ca57813d5d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-13-2733-2019-ie00001.svg" width="64pt" height="10pt" src="tc-13-2733-2019-ie00001.png"/></svg:svg></span></span> m a<span class="inline-formula"><sup>−1</sup></span>) is more than 3 times more negative than that of the land-terminating Thorthormi Glacier (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">1.40</mn><mo>±</mo><mn mathvariant="normal">0.07</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="d90d10707e7e021003efc8a492ce57b3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-13-2733-2019-ie00002.svg" width="64pt" height="10pt" src="tc-13-2733-2019-ie00002.png"/></svg:svg></span></span> m a<span class="inline-formula"><sup>−1</sup></span>) for the 2004–2011 period. The surface flow velocities decrease down-glacier along Thorthormi Glacier, whereas they increase from the upper part of the ablation area to the terminus of Lugge Glacier. Numerical experiments using a two-dimensional ice flow model demonstrate that the rapid thinning of Lugge Glacier is driven by both a negative surface mass balance and dynamically induced ice thinning. However, the thinning of Thorthormi Glacier is minimised by a longitudinally compressive flow regime. Multiple supraglacial ponds on Thorthormi Glacier have been expanding since 2000 and have merged into a single proglacial lake, with the glacier terminus detaching from its terminal moraine in 2011. Numerical experiments suggest that the thinning of Thorthormi Glacier will accelerate with continued proglacial lake development.</p> |
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| ISSN: | 1994-0416 1994-0424 |