Ross Ice Shelf Lamb Wave Propagation and Permanent Displacement Induced by Whillans Ice Stream Slip Events
Description:
Ice shelves are generally assumed to move slowly and steadily from their grounding lines to the ice front. Here we report the detection of ice-propagating extensional Lamb (plate) waves accompanied by pulses of permanent ice shelf displacement, observed by a network of co-located GNSS receivers and broadband seismographs deployed on the Ross Ice Shelf in 2014-2016. The extensional waves and ice shelf displacement are produced by the once or twice daily tidally triggered basal slip events of the Whillans Ice Stream (WIS), which flows into the ice shelf. The extensional waves are observed on broadband seismographs as two or three non-dispersive long-period (20 -100 s) pulses spanning 15-30 minutes, radiated at the three main sites of basal slip acceleration identified by previous studies of the WIS. The extensional wave initial particle motions are nearly horizontal and radial to the WIS, and are detected at distances of greater than 500 km. The propagation velocity of 2.8 km/s is intermediate between the shear and compressional ice velocities, with velocity and particle motions consistent with theoretical predictions for thin-plate extensional Lamb waves. Following the first extensional wave arrival, GNSS observations show that the entire ice shelf is displaced about 0.06 meters in a direction away from the WIS, with peak velocity that is more than an order of magnitude above the normal flow rate. The observed maximum particle velocities of about 0.0002 m/s imply peak dynamic strains on the order of 10-7, comparable to strains from earthquake surface waves that trigger ice quakes. These results demonstrate that stick-slip events in ice streams can produce elastic waves and short-term strain pulse that propagate across the entire downstream ice shelf.
Session: Applications and Discoveries in Cryoseismology Across Spatial and Temporal Scales - I
Type: Oral
Date: 5/2/2024
Presentation Time: 05:15 PM (local time)
Presenting Author: Douglas
Student Presenter: No
Invited Presentation:
Authors
Douglas Wiens Presenting Author Corresponding Author doug@wustl.edu Washington University in St. Louis |
Richard Aster Rick.Aster@colostate.edu Colorado State University |
Andrew Nyblade aan2@psu.edu Pennsylvania State University |
Peter Bromirski pbromirski@ucsd.edu University of California, San Diego |
Peter Gerstoft gerstoft@ucsd.edu University of California, San Diego |
Ralph Stephen rstephen@whoi.edu Woods Hole Oceanographic Institution |
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Ross Ice Shelf Lamb Wave Propagation and Permanent Displacement Induced by Whillans Ice Stream Slip Events
Category
Applications and Discoveries in Cryoseismology Across Spatial and Temporal Scales