Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

Hart, Jane K.; Martinez, Kirk; Basford, Philip J.; Clayton, Alexander; Robson, Benjamin Aubrey; Young, David

doi:10.1038/s41467-019-09547-6

Cited by 24 publications

(41 citation statements)

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“…Recent instrumental and geophysical studies at Skálafellsjökull – an active temperate glacier with a similar landsystem signature to Fjallsjökull (cf. Evans and Orton, ; Chandler et al ., , c) – have shown that it has a very low water‐storage capacity and surface meltwater is rapidly transferred to the glacier bed via crevasses and moulins (Hart et al, , , ). A combination of this efficient englacial drainage system and high meltwater inputs results in saturated subglacial tills throughout the melt season at Skálafellsjökull (cf.…”

Section: Synthesis and Discussionmentioning

confidence: 99%

“…A combination of this efficient englacial drainage system and high meltwater inputs results in saturated subglacial tills throughout the melt season at Skálafellsjökull (cf. Hart et al ., , ). The instrumental work has also recorded high water pressures during the entire melt season, which have been suggested to reflect an inefficient, distributed drainage system (Hart et al ., ; cf.…”

Section: Synthesis and Discussionmentioning

confidence: 99%

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Sub‐annual moraine formation at an active temperate Icelandic glacier

Chandler

Evans

et al. 2020

Earth Surf Processes Landf

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This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low‐relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub‐annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub‐annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt‐driven squeeze events and (ii) larger push moraines formed during winter re‐advances. We suggest the development of this process‐form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice‐marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process‐form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Section: Synthesis and Discussionmentioning

confidence: 99%

Section: Synthesis and Discussionmentioning

confidence: 99%

Sub‐annual moraine formation at an active temperate Icelandic glacier

Chandler

Evans

et al. 2020

Earth Surf Processes Landf

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“…A combination of this efficient englacial drainage system and high meltwater inputs results in saturated subglacial tills throughout the melt season at Skálafellsjökull (cf. Hart et al, 2015Hart et al, , 2019b. The instrumental work has also recorded high water pressures during the entire melt season, which have been suggested to reflect an inefficient, distributed drainage system (Hart et al, 2019b;cf.…”

Section: Controls On Sub-annual Moraine Formationmentioning

confidence: 95%

“…Hart et al, 2015Hart et al, , 2019b. The instrumental work has also recorded high water pressures during the entire melt season, which have been suggested to reflect an inefficient, distributed drainage system (Hart et al, 2019b;cf. Schoof, 2010).…”

Section: Controls On Sub-annual Moraine Formationmentioning

confidence: 95%

“…Recent instrumental and geophysical studies at Skálafellsjökullan active temperate glacier with a similar landsystem signature to Fjallsjökull (cf. Evans and Orton, 2015;Chandler et al, 2016a, c) have shown that it has a very low water-storage capacity and surface meltwater is rapidly transferred to the glacier bed via crevasses and moulins (Hart et al, 2015(Hart et al, , 2019a(Hart et al, , 2019b. A combination of this efficient englacial drainage system and high meltwater inputs results in saturated subglacial tills throughout the melt season at Skálafellsjökull (cf.…”

Section: Controls On Sub-annual Moraine Formationmentioning

confidence: 99%

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Sub-annual moraine formation at an active temperate Icelandic glacier

Chandler

Evans

et al. 2020

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2020) 'Subannual moraine formation at an active temperate Icelandic glacier.', Earth surface processes and landforms., 45 (7).The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.ABSTRACT: This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öraefajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height~1.2 m) and a group of comparatively low-relief moraines (mean height~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub-annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for subannual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt-driven squeeze events and (ii) larger push moraines formed during winter re-advances. We suggest the development of this process-form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice-marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process-form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin.

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

Baurley

Robson

Hart

2020

Earth Surf Processes Landf

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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 ± 0.36 m day−1 in 1991 to 3.50 ± 0.25 m day−1 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 0.55 km2 year−1. Over the same period, the eastern arm retreated by ~3.50 km, 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 ~300 m‐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. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

Cited by 24 publications

References 68 publications

Sub‐annual moraine formation at an active temperate Icelandic glacier

Sub‐annual moraine formation at an active temperate Icelandic glacier

Sub-annual moraine formation at an active temperate Icelandic glacier

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

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