Changing contribution of peak velocity events to annual velocities following a multi-decadal slowdown at White Glacier

Thomson, Laura; Copland, Luke

doi:10.1017/aog.2017.46

Cited by 7 publications

(6 citation statements)

References 20 publications

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“…Similarly, Stevens et al (2016) observed at North Lake net annual flow deceleration of 1.1% per year during 2009-2013. Analogous multi-year slow-down trends of glaciers have been observed in Alaska (Truffer et al, 2005;Burgess et al, 2013) and Canada (Thomson and Copland, 2017).…”

Section: Decadal Ice Flow Variabilitysupporting

confidence: 57%

The Influence of Hydrology on the Dynamics of Land-Terminating Sectors of the Greenland Ice Sheet

et al. 2019

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Coupling between runoff, hydrology, basal motion, and mass loss ("hydrology-dynamics") is a critical component of the Greenland Ice Sheet system. Despite considerable research effort, the mechanisms by which runoff influences ice dynamics and the net long-term (decadal and longer) dynamical effect of variations in the timing and magnitude of runoff delivery to the bed remain a subject of debate. We synthesise key research into land-terminating ice sheet hydrology-dynamics, in order to reconcile several apparent contradictions that have recently arisen as understanding of the topic has developed. We suggest that meltwater interaction with subglacial channels, cavities, and deforming subglacial sediment modulates ice flow variability. Increasing surface runoff supply to the bed induces cavity expansion and sediment deformation, leading to early-melt season ice flow acceleration. In the ablation area, drainage of water at times of low runoff from high-pressure subglacial environments toward more efficient drainage pathways is thought to result in reductions in water pressure, ice-bed separation and sediment deformation, causing net slowdown on annual to decadal timescales (ice flow self-regulation), despite increasing surface melt. Further inland, thicker ice, small surface gradients and reduced runoff suppress efficient drainage development, and a small net increase in both summer and winter ice flow is observed. Predicting ice motion across land-terminating sectors of the ice sheet over the twenty-first century is confounded by inadequate understanding of the processes and feedbacks between runoff and subglacial motion. However, if runoff supply increases, we suggest that ice flow in marginal regions will continue to decrease on annual and longer timescales, principally due to (i) increasing drainage system efficiency in marginal areas, (ii) progressive depression of basal water pressure, and (iii) thinning-induced lowering of driving stresses. At higher elevations, we suggest that minor year-on-year ice flow acceleration will continue and extend further into the interior where self-regulation mechanisms cannot operate and if surface-to-bed meltwater connections form. Based on current understanding, we expect that ice flow deceleration due to the seasonal development of efficient drainage beneath the land-terminating margins of the Greenland Ice Sheet will continue to regulate its future mass loss.

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Section: Decadal Ice Flow Variabilitysupporting

confidence: 57%

The Influence of Hydrology on the Dynamics of Land-Terminating Sectors of the Greenland Ice Sheet

et al. 2019

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“…The possible reason for slight seasonal variation at points A2, B2 and F is that the glacier is poly-thermal with cold ice around its margins where ice is thin. In the studies of [1,22,26,41], daily or weekly velocity variations during summer can be clearly seen from observations. In our study, GPS observations at AL are only available in late April and early September, which means only the mean velocities between April and September can be obtained.…”

Section: Discussionmentioning

confidence: 99%

“…To ascertain how glaciers behave in the present and future, it is necessary to further investigate the ice flow velocity of glaciers, because the long-term evolution of glacier velocities, which control the delivery of ice to warm, low elevation regions, is an important component of the future stability of ice masses in a warming climate [22]. Poly-thermal glaciers are glaciers that have a mixed basal thermal regime, with a warm-based core, and cold-based ice around its snout and margins [1].…”

Section: Introductionmentioning

confidence: 99%

“…This mix of thermal regimes makes the dynamics of poly-thermal glaciers complex especially in Svalbard, because the water content in the temperate layer of a Svalbard-type poly-thermal glaciers is higher than the typical water content of temperate glaciers [23]. Peak surface velocities were observed shortly after the onset of the melt during summer for many poly-thermal glaciers with in-situ global positioning system (GPS) observations [22,24,25], in-situ total station observations [1] or interferometic synthetic aperture radar (InSAR) [26]. Among the methods in deriving velocities of glaciers, in-situ stakes observations can provide the most accurate coordinates at measuring points for a small region.…”

Section: Introductionmentioning

confidence: 99%

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Discovery of the Fastest Ice Flow along the Central Flow Line of Austre Lovénbreen, a Poly-thermal Valley Glacier in Svalbard

Ding

et al. 2019

Remote Sensing

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Ice flow velocity is a sensitive indicator of glacier variations both controlling and representing the delivery of ice and affecting the future stability of ice masses in a warming climate. As one of the poly-thermal glaciers in the high Arctic, Austre Lovénbreen (AL) is on the northwestern coast of Spitsbergen, Svalbard. The ice flow velocity of AL was investigated using in situ global positioning system (GPS) observations over 14 years and numerical modelling with Elmer/Ice. First, the ice flow velocity field of AL along central flow line was presented and the ice flow velocity is approximately 4 m/a. Obvious seasonal changes of ice flow velocity can be found in the middle of the glacier, where the velocity in spring-summer is 47% larger than in autumn–winter in 2016, and the mean annual velocity increased 14% from 2009 until 2016. Second, the numerical simulation was performed considering the poly-thermal character of the glacier, and indicated that there are two peak ice flow regions on the glacier, and not just one peak ice flow region as previously believed. The new peak ice flow zone found by simulation was verified by field work, which also demonstrated that the velocity of the newly identified zone is 8% faster than the previously identified zone. Third, although our field observations showed that the ice flow velocity is slowly increasing recently, the maximum ice flow velocity will soon begin to decrease gradually in the long term according to glacier evolution modelling of AL.

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“…Long-running observational records of glacier dynamics pre-dating c1984 (the launch of Landsat-5, e.g., Dehecq and others, 2019) are sparse globally. Several of these sites have remained the focus of continuous observation across several decades (Fischer and others, 2015; O'Neel and others, 2019) while others have only recently been re-established (Thomson and Copland, 2017a; Armstrong and others, 2020). These provide a growing geographic distribution of long-running datasets that may help identify multi-decadal dynamics missed in common parameterizations of glacier flow.…”

Section: Introductionmentioning

confidence: 99%

Multi-decadal basal slip enhancement at Saskatchewan Glacier, Canadian Rocky Mountains

Stevens

Roland²,

Zoet³

et al. 2022

J. Glaciol.

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Glacier motion responds dynamically to changing meltwater inputs, but the multi-decadal response of basal sliding to climate remains poorly constrained due to its sensitivity across multiple timescales. Observational records of glacier motion provide critical benchmarks to decode processes influencing glacier dynamics, but multi-decadal records that precede satellite observation and modern warming are rare. Here we present a record of motion in the ablation zone of Saskatchewan Glacier that spans seven decades. We combine in situ and remote-sensing observations to inform a first-order glacier flow model used to estimate the relative contributions of sliding and internal deformation on dynamics. We find a significant increase in basal sliding rates between melt-seasons in the 1950s and those in the 1990s and 2010s and explore three process-based explanations for this anomalous behavior: (i) the glacier surface steepened over seven decades, maintaining flow-driving stresses despite sustained thinning; (ii) the formation of a proglacial lake after 1955 may support elevated basal water pressures; and (iii) subglacial topography may cause dynamic responses specific to Saskatchewan Glacier. Although further constraints are necessary to ascertain which processes are of greatest importance for Saskatchewan Glacier's dynamic evolution, this record provides a benchmark for studies of multi-decadal glacier dynamics.

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Changing contribution of peak velocity events to annual velocities following a multi-decadal slowdown at White Glacier

Cited by 7 publications

References 20 publications

The Influence of Hydrology on the Dynamics of Land-Terminating Sectors of the Greenland Ice Sheet

The Influence of Hydrology on the Dynamics of Land-Terminating Sectors of the Greenland Ice Sheet

Discovery of the Fastest Ice Flow along the Central Flow Line of Austre Lovénbreen, a Poly-thermal Valley Glacier in Svalbard

Multi-decadal basal slip enhancement at Saskatchewan Glacier, Canadian Rocky Mountains

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