Ross Ice Shelf Icequakes Associated With Ocean Gravity Wave Activity

Chen, Z.; Bromirski, Peter D.; Gerstoft, Peter; Stephen, Ralph A.; Lee, Won Sang; Yun, Sukyoung; Olinger, S.; Aster, R. C.; Wiens, Douglas A.; Nyblade, A.

doi:10.1029/2019gl084123

Cited by 41 publications

(51 citation statements)

References 37 publications

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“…Nevertheless, we note that the icy shell of Enceladus is likely to be both seismically quieter (due to a lack of atmospheric and surface ocean processes) and less attenuative (due to much lower temperatures; ∼−198°C) than the Ross Ice Shelf. Olinger et al (2019) and Chen et al (2019) showed that the rift WR4 is seismically active, and here we have here demonstrated that rift WR6 is seismogenic as well. Both rifts are seaward of the ice shelf compressive arch induced by the marginal stresses of the flowing ice shelf (which advects seaward at speeds in excess of 1 km/year near its ocean edge) and thus experience a background laterally biaxial extensional stress field (e.g., Lipovsky, 2020).…”

Section: Tablesupporting

confidence: 77%

Projected Seismic Activity at the Tiger Stripe Fractures on Enceladus, Saturn, From an Analog Study of Tidally Modulated Icequakes Within the Ross Ice Shelf, Antarctica

et al. 2021

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Dissipation of tidal energy is expected to generate seismicity on icy‐ocean worlds; however, the distribution and timing of this seismic activity throughout an orbital cycle is not known. We used new observations from an icy‐ocean‐world analog environment on Earth to examine the relationship between tidally driven tensile stress and seismic activity within an ice shell. We investigated a pair of rifts within Antarctica's Ross Ice Shelf which are tidally stressed in a manner analogous to the orbital cycle of tidal stress experienced by Enceladus' Tiger Stripe Fractures. We found that seismic activity at the Antarctic rifts is sensitive to both the amplitude and the rate of tensile stress across the rifts. We combined these findings with calculated stress values along Enceladus' Tiger Stripe Fractures to predict seismic‐activity levels expected along the ice‐shell fractures. We predict a peak in seismicity along the four Tiger Stripe Fractures when Enceladus is 90°–120° past pericenter in its orbit around Saturn, at which point tensile stresses would reach ∼2/3 of their maximum value. We also used the magnitude distribution of icequakes along Antarctic rifts to investigate implications for the likely size of stick‐slip rupture patches along icy faults on Enceladus. Our findings predict that the Tiger Stripe Fractures should produce sustained, low‐magnitude seismic events that involve rupture along discrete portions of each fracture's total length. We predict that seismicity would fall to 50% of peak levels when stresses across the Tiger Stripe Fractures are dominantly compressional.

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Section: Tablesupporting

confidence: 77%

Projected Seismic Activity at the Tiger Stripe Fractures on Enceladus, Saturn, From an Analog Study of Tidally Modulated Icequakes Within the Ross Ice Shelf, Antarctica

et al. 2021

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“…A flow-normal gradient in interannual velocity difference was observed between DR10 and DR14, located on opposite sides of a major east–west trending rift and separated by 20 km (Figs 1a and 5, Section 4.2). This flow-normal gradient may result from rift activity associated with shear stresses along the nearby rift tip near the suture zone, and with enhanced ice-quake activity in that region (Chen and others, 2019; Olinger and others, 2019). The incoherent anomaly observed at the three ice-front stations (DR01, DR02 and DR03) could also be explained by local calving events and/or variable near-front melting that perturbs the general ice-flow pattern along the front.…”

Section: Discussionmentioning

confidence: 99%

Annual cycle in flow of Ross Ice Shelf, Antarctica: contribution of variable basal melting

et al. 2020

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Ice shelves play a critical role in modulating dynamic loss of ice from the grounded portion of the Antarctic Ice Sheet and its contribution to sea-level rise. Measurements of ice-shelf motion provide insights into processes modifying buttressing. Here we investigate the effect of seasonal variability of basal melting on ice flow of Ross Ice Shelf. Velocities were measured from November 2015 to December 2016 at 12 GPS stations deployed from the ice front to 430 km upstream. The flow-parallel velocity anomaly at each station, relative to the annual mean, was small during early austral summer (November–January), negative during February–April, and positive during austral winter (May–September). The maximum velocity anomaly reached several metres per year at most stations. We used a 2-D ice-sheet model of the RIS and its grounded tributaries to explore the seasonal response of the ice sheet to time-varying basal melt rates. We find that melt-rate response to changes in summer upper-ocean heating near the ice front will affect the future flow of RIS and its tributary glaciers. However, modelled seasonal flow variations from increased summer basal melting near the ice front are much smaller than observed, suggesting that other as-yet-unidentified seasonal processes are currently dominant.

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“…We showed that the major impact of sea ice in this analysis is that it prohibits wind observations, rather than distorting the observed wave event on its travel path. Sea ice attenuates higher‐frequency swell (Ardhuin et al, ; Bates & Shapiro, ; Chen et al, ; Hell et al, ; Squire & Allan, ; Squire, ; Stopa et al, ), while wave dispersion changes are minor for typical mean sea ice thicknesses of about 1.5 m in the Southern Ocean Gyres and for periods longer than 15 s (Wadhams & Doble, ; Williams et al, ). This analysis only uses the dispersion of linear deep ocean waves, so the attenuation of waves in sea ice has no effect on the analysis, as long as wave‐induced signals are detected by seismometers.…”

Section: Discussionmentioning

confidence: 99%

“…We show here (i) that this method can be used to validate state‐of‐the‐art reanalysis products (section ) and (ii) that swell from storms travels through the sea ice and impacts the Ross Ice Shelf. The methodology provides a means to verify ocean wave products and to examine both sea ice‐wave interactions and the impact of ocean swell on ice shelves (Chen et al, ; Massom et al, ; Ren & Leslie, ).…”

Section: Introductionmentioning

confidence: 99%

Estimating Southern Ocean Storm Positions With Seismic Observations

et al. 2020

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Surface winds from Southern Ocean cyclones generate large waves that travel over long distances (>1,000 km). Wave generation regions are often colocated with enhanced air‐sea fluxes and upper ocean mixing. Ocean wave spectra contain information about storm wind speed, fetch size, and intensity at their generation site. Two years of seismic observations on the Ross Ice shelf, combined with modern optimization (machine learning) techniques, are used to trace the origins of wave events in the Southern Ocean with an accuracy of ±110 km and ±2 hr from a hypothetical point source. The observed spectral energy attenuated within sea ice and in the ice shelf but retains characteristics that can be compared to parametric wave models. Comparison with the Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 reanalyses suggests that less than 45% of ocean swell events can be associated with individual Southern Ocean storms, while the majority of the observed wave events cannot be matched with Southern Ocean high wind events. Reanalysis cyclones and winds are often displaced by about 350 km or 10 hr in Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 compared to the most likely positions inferred from the seismic spectra. This high fraction of displaced storms in reanalysis products over the South Pacific can be explained by the limited availability of remote sensing observations, primarily caused by the presence of sea ice. Deviation of wave rays from their great circle path by wave‐current interaction plays a minor role.

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Ross Ice Shelf Icequakes Associated With Ocean Gravity Wave Activity

Cited by 41 publications

References 37 publications

Projected Seismic Activity at the Tiger Stripe Fractures on Enceladus, Saturn, From an Analog Study of Tidally Modulated Icequakes Within the Ross Ice Shelf, Antarctica

Projected Seismic Activity at the Tiger Stripe Fractures on Enceladus, Saturn, From an Analog Study of Tidally Modulated Icequakes Within the Ross Ice Shelf, Antarctica

Annual cycle in flow of Ross Ice Shelf, Antarctica: contribution of variable basal melting

Estimating Southern Ocean Storm Positions With Seismic Observations

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