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  • 1
    Online Resource
    Online Resource
    Fine Structure of Microseismic Glacial Stick‐Slip
    American Geophysical Union (AGU) ; 2021
    In:  Geophysical Research Letters Vol. 48, No. 22 ( 2021-11-28)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 48, No. 22 ( 2021-11-28)
    Abstract: We study frictional processes at the bed of a glacier by drilling through 200 m ice and reaching an active stick‐slip asperity Seismicity that is not measurable from the ice surface clusters at distinct asperities located within a confined bed region Asperities host characteristic multi‐asperity ruptures, similar to the Parkfield section of the San Andreas Fault
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2021GL096043
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Slow‐slip events on the Whillans Ice Plain, Antarctica, described using rate‐and‐state friction as an ice stream sliding law
    American Geophysical Union (AGU) ; 2017
    In:  Journal of Geophysical Research: Earth Surface Vol. 122, No. 4 ( 2017-04), p. 973-1003
    Details
    In: Journal of Geophysical Research: Earth Surface, American Geophysical Union (AGU), Vol. 122, No. 4 ( 2017-04), p. 973-1003
    Abstract: We validate a laboratory‐derived sliding law, rate‐and‐state friction, as an ice stream basal sliding law Stick‐slip cycles on the Whillans Ice Plain, West Antarctica, occur in the slow‐slip limit of sliding behavior Rate‐and‐state friction captures the transition between tidally modulated stick‐slip motion and quasi‐steady tidal modulation
    Type of Medium: Online Resource
    ISSN: 2169-9003 , 2169-9011
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrf.v122.4
    DOI: 10.1002/2016JF004183
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2017
    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2138320-0
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Glacier sliding, seismicity and sediment entrainment
    Cambridge University Press (CUP) ; 2019
    In:  Annals of Glaciology Vol. 60, No. 79 ( 2019-09), p. 182-192
    Details
    In: Annals of Glaciology, Cambridge University Press (CUP), Vol. 60, No. 79 ( 2019-09), p. 182-192
    Abstract: The evolution of glaciers and ice sheets depends on processes in the subglacial environment. Shear seismicity along the ice–bed interface provides a window into these processes. Such seismicity requires a rapid loss of strength that is typically ascribed to rate-weakening friction, i.e., decreasing friction with sliding or sliding rate. Many friction experiments have investigated glacial materials at the temperate conditions typical of fast flowing glacier beds. To our knowledge, however, these studies have all found rate-strengthening friction. Here, we investigate the possibility that rate-weakening rock-on-rock friction between sediments frozen to the bottom of the glacier and the underlying water-saturated sediments or bedrock may be responsible for subglacial shear seismicity along temperate glacier beds. We test this ‘entrainment-seismicity hypothesis’ using targeted laboratory experiments and simple models of glacier sliding, seismicity and sediment entrainment. These models suggest that sediment entrainment may be a necessary but not sufficient condition for the occurrence of basal shear seismicity. We propose that stagnation at the Whillans Ice Stream, West Antarctica may be caused by the growth of a frozen fringe of entrained sediment in the ice stream margins. Our results suggest that basal shear seismicity may indicate geomorphic activity.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.1017/aog.2019.24
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    Density matters: ice compressibility and glacier mass estimation
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Glaciology Vol. 68, No. 270 ( 2022-08), p. 831-832
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 68, No. 270 ( 2022-08), p. 831-832
    Abstract: Ice flow models typically assume that ice is incompressible, a reasonable assumption because ice density changes are indeed small and have a correspondingly small effect on the overall mass balance of glaciers and ice sheets. Given the immense volume of the ice sheets, however, even relatively small changes may influence global mean sea level to a degree that severely impacts humanity (Hauer and others, 2020). Here, we quantify the role of gravitational compression and thermal contraction in estimating ice sheet mass.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2021.132
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 5
    Online Resource
    Online Resource
    Ice shelf rift propagation: stability, three-dimensional effects, and the role of marginal weakening
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 5 ( 2020-05-27), p. 1673-1683
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 5 ( 2020-05-27), p. 1673-1683
    Abstract: Abstract. Understanding the processes that govern ice shelf extent is important to improving estimates of future sea-level rise. In present-day Antarctica, ice shelf extent is most commonly determined by the propagation of through-cutting fractures called ice shelf rifts. Here, I present the first three-dimensional analysis of ice shelf rift propagation. I model rifts using the assumptions of linear elastic fracture mechanics (LEFM). The model predicts that rifts may be stabilized (i.e., stop propagating) when buoyant flexure results in the partial contact of rift walls. This stabilizing tendency may be overcome, however, by processes that act in the ice shelf margins. In particular, loss of marginal strength, modeled as a transition from zero tangential displacement to zero tangential shear stress, is shown to favor rift propagation. Rift propagation may also be triggered if a rift is carried with the ice flow (i.e., advected) out of an embayment and into a floating ice tongue. I show that rift stability is closely related to the transition from uniaxial to biaxial extension known as the compressive arch. Although the partial contact of rift walls is fundamentally a three-dimensional process, I demonstrate that it may be parameterized within more numerically efficient two-dimensional calculations. This study constitutes a step towards a first-principle description of iceberg calving due to ice shelf rift propagation.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-14-1673-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 6
    Online Resource
    Online Resource
    Characterising sediment thickness beneath a Greenlandic outlet glacier using distributed acoustic sensing: preliminary observations and progress towards an efficient machine learning approach
    Cambridge University Press (CUP) ; 2023
    In:  Annals of Glaciology
    Details
    In: Annals of Glaciology, Cambridge University Press (CUP)
    Abstract: Distributed Acoustic Sensing (DAS) is increasingly recognised as a valuable tool for glaciological seismic applications, although analysing the large data volumes generated in acquisitions poses computational challenges. We show the potential of active-source DAS to image and characterise subglacial sediment beneath a fast-flowing Greenlandic outlet glacier, estimating the thickness of sediment layers to be 20–30 m. However, the lack of subglacial velocity constraint limits the accuracy of this estimate. Constraint could be provided by analysing cryoseismic events in a counterpart 3-day record of passive seismicity through, for example, seismic tomography, but locating them within the 9 TB data volume is computationally inefficient. We describe experiments with data compression using the frequency-wavenumber (f-k) transform ahead of training a convolutional neural network, that provides a ~300-fold improvement in efficiency. In combining active and passive-source and our machine learning framework, the potential of large DAS datasets could be unlocked for a range of future applications.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.1017/aog.2023.15
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 7
    Online Resource
    Online Resource
    Ice Shelf Rift Propagation and the Mechanics of Wave‐Induced Fracture
    American Geophysical Union (AGU) ; 2018
    In:  Journal of Geophysical Research: Oceans Vol. 123, No. 6 ( 2018-06), p. 4014-4033
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 123, No. 6 ( 2018-06), p. 4014-4033
    Abstract: I infer ice shelf wave‐induced stresses and then relate these stresses to a rift propagation criterion based in inertial fracture mechanics The lack of rift propagation during periods of high wave‐induced stresses suggests the existence of additional rift strengthening Ice shelf rifts may be stabilized as they propagate into deeper water or thinner ice
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2017JC013664
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2018
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Hydraulic Conditions for Stick‐Slip Tremor Beneath an Alpine Glacier
    American Geophysical Union (AGU) ; 2022
    In:  Geophysical Research Letters Vol. 49, No. 21 ( 2022-11-16)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 49, No. 21 ( 2022-11-16)
    Abstract: Seismogenic stick‐slip tremor occurs at the confluence of two subglacial channels during diurnal high‐melt periods on an Alpine glacier During tremor, the seismic moment released by stick‐slip sliding is ∼10 times higher than outside of tremor periods An extended spring‐loaded slider‐block model describes tremor activity with asperity loading from viscous creep and cavity formation
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2022GL100286
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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