Motion of an Antarctic glacier by repeated tidally modulated earthquakes

Zoet, Lucas K.; Anandakrishnan, S.; Alley, Richard B.; Nyblade, A.; Wiens, Douglas A.

doi:10.1038/ngeo1555

Cited by 80 publications

(107 citation statements)

References 24 publications

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“…Healing is greater at −3°C than at −6°C, likely because more meltwater is available to refreeze (Figure ). The log‐linear dependence of healing on hold time is consistent with healing inferred by Zoet et al [], in which seismic magnitude increased with hold time (or inter‐event time) for repeating ruptures (∼25 min inter‐event) of an Antarctic outlet glacier modulated by ocean tides.…”

Section: Discussionmentioning

confidence: 99%

“…Ice also may strengthen through re‐entrainment of debris melted out during a slip event, through regelation and freeze‐on processes. Such strengthening can contribute to stick‐slip behavior [ Zoet et al ., ]. The parameter β is used to quantify the rate at which these frictional healing mechanisms occur, and is estimated through slide‐hold‐slide testing (detailed later in this paper).…”

Section: Introductionmentioning

confidence: 99%

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The effects of entrained debris on the basal sliding stability of a glacier

et al. 2013

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[1] New laboratory experiments exploring likely subglacial conditions reveal controls on the transition between stable sliding and stick-slip motion of debris-laden ice over rock, with implications for glacier behavior. Friction between a rock substrate and clasts in ice generates heat, which melts nearby ice to produce lubricating water. An increase in sliding speed or an increase in entrained debris raises heat generation and thus meltwater production. Unstable sliding is favored by low initial lubrication followed by rapid meltwater production in response to a velocity increase. Low initial lubrication can result from cold or drained conditions, whereas rapid increase in meltwater generation results from strong frictional heating caused by high sliding velocity or high debris loads. Strengthening of the interface (healing) during "stick" intervals between slip events occurs primarily through meltwater refreezing. When healing and unstable sliding are taken together, the experiments reported here suggest that stick-slip behavior is common from motion of debris-laden glacier ice over bedrock.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effects of entrained debris on the basal sliding stability of a glacier

et al. 2013

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“…Earthquakes at the glacier bed have been observed in ice-stream [53,54], outlet-glacier [5,55] and mountain-glacier [56] settings. Most authors interpret these events to be the result of stickslip behaviour at 'sticky spots', which are believed to be analogous to asperities on tectonic faults, though some basal events probably result from crack opening or closing [57].…”

Section: Implications For Glaciersmentioning

confidence: 99%

“…Variations in sliding style, including smooth sliding, stick-slip behaviour, slowdowns and switches of flow state, are attributed to basal processes (e.g. [3][4][5][6]) but are not well understood. A clearer understanding of the controls on sliding rate, including time, temperature and other basal characteristics, is essential to next-level modelling and forecasting.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of ice-on-rock friction at realistic glacier conditions

McCarthy

Savage

Nettles

2017

Phil. Trans. R. Soc. A.

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One contribution of 11 to a theme issue 'Microdynamics of ice'. Using a new biaxial friction apparatus, we conducted experiments of ice-on-rock friction in order to better understand basal sliding of glaciers and ice streams. A series of velocity-stepping and slidehold-slide tests were conducted to measure friction and healing at temperatures between −20°C and melting. Experimental conditions in this study are comparable to subglacial temperatures, sliding rates and effective pressures of Antarctic ice streams and other glaciers, with load-point velocities ranging from 0.5 to 100 µm s −1 and normal stress σ n = 100 kPa. In this range of conditions, temperature dependences of both steady-state friction and frictional healing are considerable. The friction increases linearly with decreasing temperature (temperature weakening) from μ = 0.52 at −20°C to μ = 0.02 at melting. Frictional healing increases and velocity dependence shifts from velocity-strengthening to velocityweakening behaviour with decreasing temperature. Our results indicate that the strength and stability of glaciers and ice streams may change considerably over the range of temperatures typically found at the ice-bed interface. Subject Areas: glaciology KeywordsThis article is part of the themed issue 'Microdynamics of ice'.

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“…At Taylor Glacier in Antarctica, seismic multiplets triggered by melt are used as a proxy for melt production [ Carmichael et al , ]. Icequakes commonly occur as multiplets or repeating events in a variety of settings including outlet glaciers [ Zoet et al , ]. A single region can demonstrate different types of repeating icequakes, such as Mount Rainier where they can be shallow and low frequency representing stick‐slip motion at the base of alpine glaciers [ Thelen et al , ] or they can be low‐frequency events located high on the edifice and triggered by snow loading [ Allstadt and Malone , ].…”

Section: Introductionmentioning

confidence: 99%

A previously unreported type of seismic source in the firn layer of the East Antarctic Ice Sheet

Lough

Barcheck

Wiens³

et al. 2015

JGR Earth Surface

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We identify a unique type of seismic source in the uppermost part of the East Antarctic Ice Sheet recorded by temporary broadband seismic arrays in East Antarctica. These sources, termed "firnquakes," are characterized by dispersed surface wave trains with frequencies of 1-10 Hz detectable at distances up to 1000 km. Events show strong dispersed Rayleigh wave trains and an absence of observable body wave arrivals; most events also show weaker Love waves. Initial events were discovered by standard detection schemes; additional events were then detected with a correlation scanner using the initial arrivals as templates. We locate sources by determining the L2 misfit for a grid of potential source locations using Rayleigh wave arrival times and polarization directions. We then perform a multiple-filter analysis to calculate the Rayleigh wave group velocity dispersion and invert the group velocity for shear velocity structure. The resulting velocity structure is used as an input model to calculate synthetic seismograms. Inverting the dispersion curves yields ice velocity structures consistent with a low-velocity firn layer~100 m thick and show that velocity structure is laterally variable. The absence of observable body wave phases and the relative amplitudes of Rayleigh waves and noise constrain the source depth to be less than 20 m. The presence of Love waves for most events suggests the source is not isotropic. We propose the events are linked to the formation of small crevasses in the firn, and several events correlate with shallow crevasse fields mapped in satellite imagery.

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Motion of an Antarctic glacier by repeated tidally modulated earthquakes

Cited by 80 publications

References 24 publications

The effects of entrained debris on the basal sliding stability of a glacier

The effects of entrained debris on the basal sliding stability of a glacier

Temperature dependence of ice-on-rock friction at realistic glacier conditions

A previously unreported type of seismic source in the firn layer of the East Antarctic Ice Sheet

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