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Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland

Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland
Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland
Proglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide due to continued climate warming and glacier retreat, and such lakes have important consequences for the dynamics and future stability of these glaciers. In light of this, we quantified decadal changes in glacier velocity since 1991 using satellite remote sensing for Breiðamerkurjökull, a large lake-terminating glacier in Iceland. We investigated its frontal retreat, lake area change and ice surface elevation change, combined with bed topography data, to understand its recent rapid retreat and future stability. We observed highly spatially variable velocity change from 1991 to 2015, with a substantial increase in peak velocity observed at the terminus of the lake-terminating eastern arm from ~1.00±0.36m day1 in 1991 to 3.50±0.25m day1 in 2015, with mean velocities remaining elevated from 2008 onwards. This is in stark comparison to the predominately land-terminating arms, which saw no discernible change in their velocity over the same period. We also observed a substantial increase in the area of the main proglacial lake (Jökulsárlón) since 1982 of ~20 km2, equating to an annual growth rate of 0.55km2 year1. Over the same period, the eastern arm retreated by ~3.50km, which is significantly greater than the other arms. Such discrepancies between the different arms are due to the growth and, importantly, depth increase of Jökulsárlón, as the eastern arm has retreated into its ~300m-deep reverse-sloping subglacial trough. We suggest that this growth in lake area, forced initially by rising air temperatures, combined with the increase in lake depth, triggered an increase in flow acceleration, leading to further rapid retreat and the initiation of a positive feedback mechanism. These findings may have important implications for how increased melt and calving forced by climate change will affect the future stability of large soft-bedded, reverse-sloped, subaqueous-terminating glaciers elsewhere.
calving, glacier dynamics, proglacial Lakes, remote sensing, retreat, velocity
0197-9337
2647-2663
Baurley, Nathaniel Ross
d567850b-2030-4d33-8d1d-5fcad6e60417
Robson, Benjamin
34cb64eb-29ec-434a-8ff8-55f12757fffc
Hart, Jane
e949a885-7b26-4544-9e15-32ba6f87e49a
Baurley, Nathaniel Ross
d567850b-2030-4d33-8d1d-5fcad6e60417
Robson, Benjamin
34cb64eb-29ec-434a-8ff8-55f12757fffc
Hart, Jane
e949a885-7b26-4544-9e15-32ba6f87e49a

Baurley, Nathaniel Ross, Robson, Benjamin and Hart, Jane (2020) Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland. Earth Surface Processes and Landforms, 45 (11), 2647-2663. (doi:10.1002/esp.4920).

Record type: Article

Abstract

Proglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide due to continued climate warming and glacier retreat, and such lakes have important consequences for the dynamics and future stability of these glaciers. In light of this, we quantified decadal changes in glacier velocity since 1991 using satellite remote sensing for Breiðamerkurjökull, a large lake-terminating glacier in Iceland. We investigated its frontal retreat, lake area change and ice surface elevation change, combined with bed topography data, to understand its recent rapid retreat and future stability. We observed highly spatially variable velocity change from 1991 to 2015, with a substantial increase in peak velocity observed at the terminus of the lake-terminating eastern arm from ~1.00±0.36m day1 in 1991 to 3.50±0.25m day1 in 2015, with mean velocities remaining elevated from 2008 onwards. This is in stark comparison to the predominately land-terminating arms, which saw no discernible change in their velocity over the same period. We also observed a substantial increase in the area of the main proglacial lake (Jökulsárlón) since 1982 of ~20 km2, equating to an annual growth rate of 0.55km2 year1. Over the same period, the eastern arm retreated by ~3.50km, which is significantly greater than the other arms. Such discrepancies between the different arms are due to the growth and, importantly, depth increase of Jökulsárlón, as the eastern arm has retreated into its ~300m-deep reverse-sloping subglacial trough. We suggest that this growth in lake area, forced initially by rising air temperatures, combined with the increase in lake depth, triggered an increase in flow acceleration, leading to further rapid retreat and the initiation of a positive feedback mechanism. These findings may have important implications for how increased melt and calving forced by climate change will affect the future stability of large soft-bedded, reverse-sloped, subaqueous-terminating glaciers elsewhere.

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Baurley_etal.2020 - Version of Record
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Accepted/In Press date: 29 May 2020
e-pub ahead of print date: 4 July 2020
Published date: 15 September 2020
Keywords: calving, glacier dynamics, proglacial Lakes, remote sensing, retreat, velocity

Identifiers

Local EPrints ID: 444859
URI: http://eprints.soton.ac.uk/id/eprint/444859
ISSN: 0197-9337
PURE UUID: 1923a315-8cc2-4f45-95a2-aba95c222b5e
ORCID for Nathaniel Ross Baurley: ORCID iD orcid.org/0000-0002-0444-8721
ORCID for Jane Hart: ORCID iD orcid.org/0000-0002-2348-3944

Catalogue record

Date deposited: 06 Nov 2020 17:33
Last modified: 26 Nov 2021 03:17

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Contributors

Author: Benjamin Robson
Author: Jane Hart ORCID iD

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