Seasonal Variability in Regional Ice Flow Due to Meltwater Injection Into the Shear Margins of Jakobshavn Isbræ

Cavanagh, J.; Lampkin, D. J.; Moon, Twila

doi:10.1002/2016jf004187

Cited by 14 publications

(22 citation statements)

References 81 publications

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“…The afflux from rivers and melt ponds into water-filled crevasses may triggered hydro-fracturing [32]. The coincident coordinated drainage occurs during the peak in meltwater production, which means that lake drainage events occurred during a high melt period [56,57].…”

Section: Meltwater Infiltrating Crevassesmentioning

confidence: 99%

Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

Jiang

Huang

2021

Remote Sensing

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Both a decrease of sea ice and an increase of surface meltwater, which may induce ice-flow speedup and frontal collapse, have a significant impact on the stability of the floating ice shelf in Greenland. However, detailed dynamic precursors and drivers prior to a fast-calving process remain unclear due to sparse remote sensing observations. Here, we present a comprehensive investigation on hydrological and kinematic precursors before the calving event on 26 July 2017 of Petermann Glacier in northern Greenland, by jointly using remote sensing observations at high-temporal resolution and an ice-flow model. Time series of ice-flow velocity fields during July 2017 were retrieved with Sentinel-2 observations with a sub-weekly sampling interval. The ice-flow speed quickly reached 30 m/d on 26 July (the day before the calving), which is roughly 10 times quicker than the mean glacier velocity. Additionally, a significant decrease in the radar backscatter coefficient of Sentinel-1 images suggests a rapid transformation from landfast sea ice into open water, associated with a decrease in sea ice extent. Additionally, the area of melt ponds on the floating ice tongue began to increase in mid-May, quickly reached a peak at the end of June and lasted for nearly one month until the calving occurred. We used the ice sheet system model to model the spatial-temporal damage and stress on the floating ice, thereby finding an abnormal stress distribution in a cracked region. It is inferred that this calving event may relate to a weakening of the sea ice, shearing of the tributary glacier, and meltwater infiltrating crevasses.

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Section: Meltwater Infiltrating Crevassesmentioning

confidence: 99%

Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

Jiang

Huang

2021

Remote Sensing

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“…Direct estimates of n range considerably from 2.5 to 4.5 (Bons et al, 2018;Dahl-Jensen and Gundestrup, 1987;Gillet-Chaulet et al, 2011;Lüthi et al, 2002;Ryser et al, 2014). Other aspects of ice flow such as crevasses that are common in regions of concentrated fast flow (Cavanagh et al, 2017;Lampkin et al, 2013) and in extensional regimes (Poinar et al, 2015) are not accounted for in high-order inversions but could significantly impact the relationship between the velocity field and higherorder stresses (stress gradients). Together, these aspects make it difficult to confidently estimate the rheology to invert for tractions across the Greenland Ice Sheet and use the spatial relationship between basal traction and velocity to infer bed properties.…”

Section: Introductionmentioning

confidence: 99%

Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

et al. 2021

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Abstract. On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that controls ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight major drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr–Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry of the grounded regions in Greenland is mainly dictated by Weertman-type hard-bed physics up to velocities of approximately 450 m yr−1, except within the Northeast Greenland Ice Stream and areas near floatation. Depending on the catchment, behavior of the fastest-flowing ice (∼ 1000 m yr−1) directly inland from marine-terminating outlets exhibits Weertman-type rate strengthening, Mohr–Coulomb-like behavior, or is not confidently resolved given our methodology. Given the complex basal boundary across Greenland, the relationships are captured reasonably well by simple traction laws which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a first constraint on the physics of basal motion over the grounded regions of Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.

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“…range considerably from 2.5 to 4.5 (Bons et al, 2018;Dahl-Jensen and Gundestrup, 1987;Gillet-Chaulet et al, 2011;Lüthi et al, 2002;Ryser et al, 2014). Other aspects of ice flow such as crevasses that are common in regions of concentrated fast flow (Cavanagh et al, 2017;Lampkin et al, 2013) and in extensional regimes (Poinar et al, 2015), are not accounted for in high-order inversions but could significantly impact the relationship between the 70 velocity field and higher-order stresses (stress gradients). Together, these aspects make it difficult to confidently estimate the rheology to invert for tractions across the Greenland Ice Sheet and use the spatial relationship between basal traction and velocity to infer bed properties.…”

Section: Introductionmentioning

confidence: 99%

Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

Maier¹,

Gimbert²,

Gillet-Chaulet³

et al. 2020

Preprint

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Abstract. On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that control ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr-Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry over the grounded regions of the Greenland ice sheet is mainly dictated by Weertman-type hard-bed physics. Given the complex basal boundary across Greenland, the relationships are captured surprisingly well by simple traction laws over the entire velocity range, including regions with velocities over 1000 m/yr, which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a fundamental constraint on the physics of basal motion in Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.

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Seasonal Variability in Regional Ice Flow Due to Meltwater Injection Into the Shear Margins of Jakobshavn Isbræ

Cited by 14 publications

References 81 publications

Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

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