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Characterising the structures within glaciers can give unique insight into ice motion processes. On debris-covered glaciers, traditional structural glaciological mapping is challenging because the lower glacier is hidden by the supraglacial debris layer. Here, we use high-resolution optical televiewer (OPTV) image logs from four boreholes drilled into Khumbu Glacier, Nepal, to overcome this limitation and investigate englacial structural features within a Himalayan debris-covered glacier. The OPTV logs show structural features that are up to an order of magnitude thinner than those observed at the glacier surface and reveal five structural units: (I) primary stratification of ice; (II) debris-rich planes that conform with the primary stratification; (III) water-healed crevasse traces; (IV) healed crevasse traces; and (V) steeply dipping planes of basally derived fine sediment near the glacier terminus. The OPTV logs also reveal that the primary stratification both decreases in dip with depth (by up to 56° over 20 m) and rotates with depth (by up to 100° over 20 m) towards parallelism with the proximal lateral moraine. This transformation and the presence of relict layers of basally derived sediment raised into an englacial position – possibly involving thrusting – near the glacier's now stagnant terminus reveal a previously more dynamic glacier regime.
|Number of pages||12|
|Journal||Journal of Glaciology|
|Early online date||19 Dec 2022|
|Publication status||E-pub ahead of print - 19 Dec 2022|
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Borehole optical televiewer (OPTV) logs of boreholes drilled into Khumbu Glacier, Nepal, in 2017 and 2018 as part of EverDrill research project
Hubbard, B., Miles, K. & Quincey, D. J., UK Polar Data Centre, 11 Jan 2019
Summary of instrumentation installed in boreholes drilled into Khumbu Glacier, Nepal, in 2017 and 2018 as part of EverDrill research project
Hubbard, B., Miles, K., Quincey, D. J. & Miles, E. S., UK Polar Data Centre, 09 Jan 2019
- 1 Finished
Everdrill: Accessing the interior and bed of a Himalayan debris-covered glacier to forecast future mass loss
Hubbard, B., Quincey, D. J. & Rowan, A. V.
Natural Environment Research Council
01 Oct 2016 → 31 Aug 2019
Project: Externally funded research