Tide‐induced microseismicity in the Mertz glacier grounding area, East Antarctica

Barruol, Guilhem; Cordier, Emmanuel; Bascou, Jérôme; Fontaine, Fabrice R.; Legrésy, B.; Lescarmontier, Lydie

doi:10.1002/2013gl057814

Cited by 25 publications

(46 citation statements)

References 31 publications

(38 reference statements)

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“…If the shelf is tilted toward the continent, the rift is under compression, and we see low levels of seismicity; if the shelf is tilted seaward, the rift is subjected to additional extensional stress, and we see high levels of seismicity. Our findings are consistent with previous observations of tidally modulated glacial seismicity (Barruol et al, 2013;Podolskiy et al, 2016) and tidally modulated ice shelf flow (Brunt et al, 2010;Makinson et al, 2012). We calculate the maximum stretching stress that could affect the rift associated with this tilt to be i g L where i is the ice density, g is the acceleration due to gravity, L is the distance from the rift to the ice front, and is the tidally induced tilt angle.…”

Section: Ice Shelf Slope From Ocean Tides Controls Diurnal Patterns Isupporting

confidence: 90%

Tidal and Thermal Stresses Drive Seismicity Along a Major Ross Ice Shelf Rift

Olinger

Lipovsky

Wiens

et al. 2019

Geophysical Research Letters

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Understanding deformation in ice shelves is necessary to evaluate the response of ice shelves to thinning. We study microseismicity associated with ice shelf deformation using nine broadband seismographs deployed near a rift on the Ross Ice Shelf. From December 2014 to November 2016, we detect 5,948 icequakes generated by rift deformation. Locations were determined for 2,515 events using a least squares grid‐search and double‐difference algorithms. Ocean swell, infragravity waves, and a significant tsunami arrival do not affect seismicity. Instead, seismicity correlates with tidal phase on diurnal time scales and inversely correlates with air temperature on multiday and seasonal time scales. Spatial variability in tidal elevation tilts the ice shelf, and seismicity is concentrated while the shelf slopes downward toward the ice front. During especially cold periods, thermal stress and embrittlement enhance fracture along the rift. We propose that thermal stress and tidally driven gravitational stress produce rift seismicity with peak activity in the winter.

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Section: Ice Shelf Slope From Ocean Tides Controls Diurnal Patterns Isupporting

confidence: 90%

Tidal and Thermal Stresses Drive Seismicity Along a Major Ross Ice Shelf Rift

Olinger

Lipovsky

Wiens

et al. 2019

Geophysical Research Letters

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“…The temperature also is modestly below freezing as near the base of the icy shells of Enceladus and Europa. The satellite lithostatic pressures are similar to those within Mertz glacier (Barruol et al, ) and Antarctic ice streams (Wiens et al, ). Tides are significant sources of stress within Mertz glacier and Antarctic ice streams, Europa, and Enceladus.…”

Section: Conditions With Europa and Enceladussupporting

confidence: 66%

“…For context, warm ice on the Earth clearly behaves in a macroscopically ductile manner as at low strain rates within glaciers (e.g., Barnes et al, 1971). At high strain rates, icequakes occur as within temperate freshwater lake ice (Ruzhich et al, 2009) and at the base of glaciers (Barruol et al, 2013;Wiens et al, 2008). Snow below 250 K squeaks when stepped upon indicating brittle failure (Patitsas, 2015).…”

Section: Slow Slip On Faults Within Cold Icementioning

confidence: 99%

Friction in Cold Ice Within Outer Solar System Satellites With Reference to Thermal Weakening at High Sliding Velocities

Sleep

2019

JGR Planets

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The icy shells of Enceladus and Europa consist from top down of cold (~100 K) ice at low (<0.1 MPa) pressure, cold ice at high pressure up to ~10 MPa, and warm ice near 273 K the base. The pressure ~10 MPa and temperature near 273 K of basal ice within Enceladus and Europa are similar to that within terrestrial glaciers that are known to have seismicity (icequakes). Warm ice easily melts during sliding so its icequakes are qualitatively explained and expected on these satellites if the macroscopic strain rates are comparable to those within terrestrial glaciers subjected to oceanic tides. However, cold ice at high pressures does not readily macroscopically melt during sliding. A dynamic weakening mechanism for crustal faults in rock may be applicable to Enceladus and Europa. Micron‐scale real contacts support ~0.4‐GPa shear tractions and normal tractions on rapidly sliding ice faults. At sliding velocities above ~0.1 m/s, the asperity tips of the contacts become hot and weak in ice. The macroscopic friction depends on the average strength of the asperity tips during the lifetimes of contact. The strength of the asperity tips self‐organizes so that frictional heating balances the heat lost from the asperity tip by conduction. The macroscopic coefficient of friction at coseismic sliding velocities decreases to a modest fraction of the low‐velocity coefficient of friction, but does not approach zero. This velocity‐weakening mechanism likely allows major icequakes within the cold interiors of Europa and Enceladus.

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“…Few studies report on tidal dependence of icequake occurrence. Von der Osten‐Woldenburg [] and Barruol et al [] report on surface crevassing resulting in high‐frequency events. Surface crevassing is maximal at falling tides due to bending along the grounding line.…”

Section: Discussionmentioning

confidence: 99%

Pattern of cryospheric seismic events observed at Ekström Ice Shelf, Antarctica

Hammer

Ohrnberger

Schlindwein

2015

Geophysical Research Letters

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Mobility of glaciers such as rapid retreat or disintegration of large ice volumes produces a large variety of different seismic signals. Thus, evaluating cryospheric seismic events (e.g., changes of their occurrence in space and time) allows to monitor glacier dynamics. We analyze a 1 year data span recorded at the Neumayer seismic network in Antarctica. Events are automatically recognized using hidden Markov models. In this study we focused on a specific event type occurring close to the grounding line of the Ekström ice shelf. Observed waveform characteristics are consistent with an initial fracturing followed by the resonance of a water‐filled cavity resulting in a so‐called hybrid event. The number of events detected strongly correlates with dominant tide periods. We assume the cracking to be driven by existing glacier stresses trough bending. Voids are then filled by seawater, exciting the observed resonance. In agreement with this model, events occur almost exclusively during rising tides where cavities are opened at the bottom of the glacier, i.e., at the sea/ice interface.

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Tide‐induced microseismicity in the Mertz glacier grounding area, East Antarctica

Cited by 25 publications

References 31 publications

Tidal and Thermal Stresses Drive Seismicity Along a Major Ross Ice Shelf Rift

Tidal and Thermal Stresses Drive Seismicity Along a Major Ross Ice Shelf Rift

Friction in Cold Ice Within Outer Solar System Satellites With Reference to Thermal Weakening at High Sliding Velocities

Pattern of cryospheric seismic events observed at Ekström Ice Shelf, Antarctica

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