skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Friday, March 22 until 6:00 AM ET on Saturday, March 23 due to maintenance. We apologize for the inconvenience.


Title: Slow-slip events on the Whillans Ice Plain, Antarctica, described using rate-and-state friction as an ice stream sliding law: SLOW SLIP ON THE WHILLANS ICE PLAIN
NSF-PAR ID:
10035363
Author(s) / Creator(s):
 ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Earth Surface
Volume:
122
Issue:
4
ISSN:
2169-9003
Page Range / eLocation ID:
973 to 1003
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Ice sheet evolution depends on subglacial conditions, with the ice‐bed interface's strength exerting an outsized role on the ice dynamics. Along fast‐flowing glaciers, this strength is often controlled by the deformation of subglacial till, making quantification of spatial variations of till strength essential for understanding ice‐sheet contribution to sea‐level. This task remains challenging due to a lack of in situ observations. We analyze continuous seismic data from the Whillans Ice Plain (WIP), West Antarctica, to uncover spatio‐temporal patterns in subglacial conditions. We exploit tidally modulated stick‐slip events as a natural source of sliding variability. We observe a significant reduction of the till seismic wave‐speed between the WIP sticky‐spots. These observations are consistent with a poroelastic model where the bed experiences relative porosity and effective pressure increases of >11% during stick‐slips. We conclude that dilatant strengthening appears to be an essential mechanism in stabilizing the rapid motion of fast‐flowing ice streams.

     
    more » « less
  2. Abstract Here we use polarimetric measurements from an Autonomous phase-sensitive Radio-Echo Sounder (ApRES) to investigate ice fabric within Whillans Ice Stream, West Antarctica. The survey traverse is bounded at one end by the suture zone with the Mercer Ice Stream and at the other end by a basal ‘sticky spot’. Our data analysis employs a phase-based polarimetric coherence method to estimate horizontal ice fabric properties: the fabric orientation and the magnitude of the horizontal fabric asymmetry. We infer an azimuthal rotation in the prevailing horizontal c -axis between the near-surface ( z ≈ 10–50 m) and deeper ice ( z ≈ 170–360 m), with the near-surface orientated closer to perpendicular to flow and deeper ice closer to parallel. In the near-surface, the fabric asymmetry increases toward the center of Whillans Ice Stream which is consistent with the surface compression direction. By contrast, the fabric orientation in deeper ice is not aligned with the surface compression direction but is consistent with englacial ice reacting to longitudinal compression associated with basal resistance from the nearby sticky spot. 
    more » « less
  3. Abstract

    Understanding ice sheet evolution through the geologic past can help constrain ice sheet models that predict future ice dynamics. Existing geological records of grounding line retreat in the Ross Sea, Antarctica, have been confined to ice‐free and terrestrial archives, which reflect dynamics from periods of more extensive ice cover. Therefore, our perspective of grounding line retreat since the Last Glacial Maximum remains incomplete. Sediments beneath Ross Ice Shelf and grounded ice offer complementary insight into the southernmost extent of grounding line retreat, yielding a more complete view of ice dynamics during deglaciation. Here we thermochemically separate the youngest organic carbon to estimate ages from sediments extracted near the Whillans Ice Stream grounding line to provide direct evidence for grounding line retreat in that region as recent as the mid‐Holocene (7.2 kyr B.P.). Our study demonstrates the utility of accurately dated, grounding‐line‐proximal sediment deposits for reconstructing past interactions between marine and subglacial environments.

     
    more » « less