Flexural waves in the Ross Ice Shelf

Williams, R. T.; Robinson, Edwin S.

doi:10.1029/jc086ic07p06643

Cited by 23 publications

(28 citation statements)

References 13 publications

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“…(Okal and MacAyeal, 2006)) and are probably excited by passing meteorological conditions and by ocean swell propagating into the Antarctic from afar (e.g. Williams and Robinson, 1981;MacAyeal and others, 2006b). The band of noise in the 0.01-0.06 Hz range is well displayed by the spectrograms of all example events shown in Figure 5a.…”

Section: Background Noisementioning

confidence: 98%

Seismic observations of glaciogenic ocean waves (micro-tsunamis) on icebergs and ice shelves

MacAyeal¹,

Okal

Aster

et al. 2009

J. Glaciol.

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Seismometers deployed over a 3 year period on icebergs in the Ross Sea and on the Ross Ice Shelf, Antarctica, reveal that impulsive sources of ocean surface waves are frequent (e.g. ∼200 events per year in the Ross Sea) in the ice-shelf and iceberg-covered environment of coastal Antarctica. The 368 events recorded by our field deployment suggest that these impulsive events are generated by glaciological mechanisms, such as (1) small-scale calving and edge wasting of icebergs and ice-shelf fronts, (2) edge-on-edge closing and opening associated with iceberg collisions and (3) possibly the impulsive opening of void space associated with ice-shelf rifting and basal crevasse formation. The observations described here provide a background of glaciogenic ocean-wave phenomena relevant to the Ross Sea and suggest that these phenomena may be exploited in the future (using more purposefully designed observation schemes) to understand iceberg calving and ice-shelf disintegration processes.

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Section: Background Noisementioning

confidence: 98%

Seismic observations of glaciogenic ocean waves (micro-tsunamis) on icebergs and ice shelves

MacAyeal¹,

Okal

Aster

et al. 2009

J. Glaciol.

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“…Tsunami‐generated peak beam power occurs at a lower frequency than the peak IG response (Figure ; black dots in Figures a and b). These results are consistent with flexural‐gravity wave theory [ Fox and Squire , ] and with prior IG wave‐generated flexural‐gravity wave measurements determined using a sparse gravimeter array on the RIS [ Williams and Robinson , ].…”

Section: Water‐ice‐coupled Flexural‐gravity Wave Propagation Charactementioning

confidence: 99%

Tsunami and infragravity waves impacting Antarctic ice shelves

et al. 2017

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The responses of the Ross Ice Shelf (RIS) to the 16 September 2015 8.3 (Mw) Chilean earthquake tsunami (>75 s period) and to oceanic infragravity (IG) waves (50–300 s period) were recorded by a broadband seismic array deployed on the RIS from November 2014 to November 2016. Here we show that tsunami and IG‐generated signals within the RIS propagate at gravity wave speeds (∼70 m/s) as water‐ice coupled flexural‐gravity waves. IG band signals show measureable attenuation away from the shelf front. The response of the RIS to Chilean tsunami arrivals is compared with modeled tsunami forcing to assess ice shelf flexural‐gravity wave excitation by very long period (VLP; >300 s) gravity waves. Displacements across the RIS are affected by gravity wave incident direction, bathymetry under and north of the shelf, and water layer and ice shelf thicknesses. Horizontal displacements are typically about 10 times larger than vertical displacements, producing dynamical extensional motions that may facilitate expansion of existing fractures. VLP excitation is continuously observed throughout the year, with horizontal displacements highest during the austral winter with amplitudes exceeding 20 cm. Because VLP flexural‐gravity waves exhibit no discernable attenuation, this energy must propagate to the grounding zone. Both IG and VLP band flexural‐gravity waves excite mechanical perturbations of the RIS that likely promote tabular iceberg calving, consequently affecting ice shelf evolution. Understanding these ocean‐excited mechanical interactions is important to determine their effect on ice shelf stability to reduce uncertainty in the magnitude and rate of global sea level rise.

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“…The seismometer recorded a variety of signals during the field campaign [ Okal and MacAyeal , 2006] including earthquakes, tsunamis, iceberg‐generated tremor and, what is featured in the present study, sea swell incident on the ice shelf from points of origin distributed across the North and South Pacific, the Indian and the Southern oceans. In this respect, a unique aspect of this deployment is that the seismometer on the floating ice shelf responds not only to elastic waves propagating in the ice, but directly to the motion of the ice shelf as a whole, even if the ice is totally rigid (e.g., as when the ice shelf rocks and bobs, as described by Okal and MacAyeal , 2006), as well as to flexure of the ice shelf as it attempts to conform to the ocean surface on which it floats (e.g., as is the case of flexural gravity waves described by Williams and Robinson , 1981). Indeed, Okal and MacAyeal [2006] showed that this seismometer (and similar ones located on nearby drifting icebergs) recorded the 3‐D motion of the surface of the sea during the great 2004 Sumatra tsunami.…”

Section: Summary Of Ice Shelf Seismometer Signalsmentioning

confidence: 99%

“…Their research indicated that icebergs can display a resonant response to swell, however their field program was short, and only involved several days of operation. Gravimeters used to study ocean tides on the Ross Ice Shelf [ Williams and Robinson , 1981] also detected motions attributed to ocean swell with period below 100 s at a location about 600 km south of the seaward ice front where the ice shelf thickness was approximately 500 m. In both prior measurement efforts, the results came at the cost of very great logistical effort, thus making further study less appealing.…”

Section: Introductionmentioning

confidence: 99%

Seismic observations of sea swell on the floating Ross Ice Shelf, Antarctica

2009

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[1] A seismometer operating on the floating Ross Ice Shelf near its seaward ice front (Nascent Iceberg) for 340 days (out of 730 days) during the 2004, 2005, and 2006 Antarctic field seasons recorded the arrival of 93 distantly sourced ocean swell events displaying frequency dispersion characteristic of surface gravity waves propagating on deep water. Comparison of swell event dispersion with the NOAA Wave Watch III (NWW3) ocean wave model analysis reveals that 83 of these events were linked to specific storms located in the Pacific, Southern, and Indian oceans. Nearly all major storms in the NWW3 analysis of the Pacific Ocean were linked to signals observed at the Nascent site during the period of seismometer operation. Swell-induced motion of the Ross Ice Shelf is found to increase by several orders of magnitude over the time period that sea ice surrounding Antarctica decreases from its maximum extent (October) to its minimum extent (February). The amplitude of vertical vibration of the ice shelf in the frequency band between 0.025 and 0.14 Hz varies between tens of micrometers to millimeters as sea ice decays to its minimum seasonal extent. This suggests that climate influence on sea ice extent may indirectly modulate swell energy incident on the calving margins of the Antarctic Ice Sheet. The largest swell signals observed on the Ross Ice Shelf come from storms in the tropical Pacific and Gulf of Alaska. These remote events emphasize how the iceberg calving margin of Antarctica is connected to environmental conditions well beyond Antarctica.

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Flexural waves in the Ross Ice Shelf

Cited by 23 publications

References 13 publications

Seismic observations of glaciogenic ocean waves (micro-tsunamis) on icebergs and ice shelves

Seismic observations of glaciogenic ocean waves (micro-tsunamis) on icebergs and ice shelves

Tsunami and infragravity waves impacting Antarctic ice shelves

Seismic observations of sea swell on the floating Ross Ice Shelf, Antarctica

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