Spatial Variation in Radar-Derived Basal Properties of Rutford Ice Stream, West Antarctica

Schlegel, Rebecca; Murray, Tavi; Smith, Andrew M.; Brisbourne, Alex; Booth, Adam; King, Edward C.; Clark, Roger A.

doi:10.1002/essoar.10505715.1

Cited by 2 publications

(9 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We observe, for instance, fewer icequakes northeast of the central high than southwest of it within the broad domain of stiff sediments downstream of the bed character boundary. A lower radar reflectivity has been inferred for the latter, which suggests outcropping bedrock or very compressed sediments (Schlegel et al., 2021). Thus, larger regions of reduced seismicity within stiff till units could indicate the presence of compressed sediment or outcropping bedrock.…”

Section: Discussion and Interpretationmentioning

confidence: 99%

“…In addition to icequake occurrence, the basal hydraulic system of RIS varies dependent on bed rheology (Murray et al., 2008). Based on radar and seismic surveys, it was shown that water channels or bodies exist in the region of soft sediments over a long distance along the landforms (at least 1 km long and 200 m wide, King, Woodward, et al., 2004; Murray et al., 2008; and Schlegel et al., 2021). Furthermore, water may be present on top of MSGL ridges (King, Hindmarsh, et al., 2009; Murray et al., 2008; Schlegel et al., 2021).…”

Section: Survey Locationmentioning

confidence: 99%

“…Based on radar and seismic surveys, it was shown that water channels or bodies exist in the region of soft sediments over a long distance along the landforms (at least 1 km long and 200 m wide, King, Woodward, et al., 2004; Murray et al., 2008; and Schlegel et al., 2021). Furthermore, water may be present on top of MSGL ridges (King, Hindmarsh, et al., 2009; Murray et al., 2008; Schlegel et al., 2021). Within the stiffer sediment region, free water appears in isolated spots and pools (Murray et al., 2008; Schlegel et al., 2021).…”

Section: Survey Locationmentioning

confidence: 99%

“…Furthermore, water may be present on top of MSGL ridges (King, Hindmarsh, et al., 2009; Murray et al., 2008; Schlegel et al., 2021). Within the stiffer sediment region, free water appears in isolated spots and pools (Murray et al., 2008; Schlegel et al., 2021).…”

Section: Survey Locationmentioning

confidence: 99%

See 3 more Smart Citations

Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica

et al. 2021

Self Cite

View full text Add to dashboard Cite

Mass transfer from the ice sheet interior to the oceans is dominated by ice stream flow (Rignot et al., 2011), which, in turn, is governed by deformation within the ice, and friction and deformation at the bed, that is, the contact between ice and underlying sediments or bedrock. Furthermore, tidally induced modulations influence the flow dynamics of some ice streams, likely by introducing pressure modulation at the bed (Anandakrishnan et al., 2003; Gudmundsson, 2006). Poorly constrained processes and conditions at ice stream beds, therefore, contribute to the uncertainty in sea-level rise projections. Better understanding of the dynamic response of ice streams to a warming climate and oceans therefore requires improved models of these basal processes and the spatial variation in properties. Here, we focus on the understanding of basal sliding and deformation characteristics through the analysis of naturally occurring micro-earthquakes at the ice-bed interface. These events are used to examine the nature of basal slip, tidal influences, and spatial and temporal variations. The beds of ice streams consist of bedrock and sediment, often known as till. Till stiffness is variable and depends on the dynamic conditions and material properties. Ice flow at the bed is then facilitated by a combination of slip over a hard bed and by slip and deformation within a soft bed. Fluids further modulate basal ice stream flow. Where bedrock is exposed or subglacial till has relatively low permeability and is of Abstract Microseismicity, induced by the sliding of a glacier over its bed, can be used to characterize frictional properties of the ice-bed interface, which are a key parameter controlling ice stream flow. We use naturally occurring seismicity to monitor spatiotemporally varying bed properties at Rutford Ice Stream, West Antarctica. We locate 230,000 micro-earthquakes with local magnitudes from −2.0 to −0.3 using 90 days of recordings from a 35-station seismic network located ∼40 km upstream of the grounding line. Events exclusively occur near the ice-bed interface and indicate predominantly flow-parallel stick-slip. They mostly lie within a region of interpreted stiff till and along the likely stiffer part of mega-scale glacial lineations. Within these regions, micro-earthquakes occur in spatially (<100 m radius) and temporally (mostly 1-5 days activity) restricted event-clusters (up to 4,000 events), which exhibit an increase, followed by a decrease, in event magnitude with time. This may indicate event triggering once activity is initiated. Although ocean tides modulate the surface ice flow velocity, we observe little periodic variation in overall event frequency over time and conclude that water content, bed topography and stiffness are the major factors controlling microseismicity. Based on variable rupture mechanisms and spatiotemporal characteristics, we suggest the event-clusters relate to three end-member types of bed deformation: (1) continuous creation and seismogenic destruction of small-scale bed-roughness, (2...

show abstract

Section: Discussion and Interpretationmentioning

confidence: 99%

Section: Survey Locationmentioning

confidence: 99%

Section: Survey Locationmentioning

confidence: 99%

Section: Survey Locationmentioning

confidence: 99%

See 2 more Smart Citations

Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…The data, which supported the main findings of this work (Power reflected from the bed reflection acquired using the surface radar data), are available via the UK Polar Data Centre (UK PDC): https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01438 (Schlegel et al., 2020).…”

Section: Data Availability Statementmentioning

confidence: 58%

Radar Derived Subglacial Properties and Landforms Beneath Rutford Ice Stream, West Antarctica

et al. 2022

Self Cite

View full text Add to dashboard Cite

Basal properties beneath ice streams and glaciers are known to be a control for ice flow dynamics, hence knowledge of them is crucial for predicting sea level due to changes in glacial dynamics. Basal properties, processes and topography also drive the formation of subglacial landforms. Bed properties beneath Rutford Ice Stream (West Antarctica) have previously been described using seismic acoustic impedance measurements at a sparse spatial coverage. Here, we derive bed properties in a 15 × 17 km grid of surface radar data with coverage and sampling much higher than previous seismic studies. Bed reflection amplitudes in surface radar data were calibrated using sediment porosities (ranging from 0.4–0.5) derived from seismic acoustic impedance. We find the bed properties are spatially variable, consisting of low porosity material in some areas and soft sediment in other areas. Comparison of seismic and surface radar data imply the low porosity material to be a consolidated sediment or sedimentary rock. Mega‐scale glacial lineations (MSGLs) are ubiquitous on the bed and consist of soft, high porosity, probably deforming sediment, consistent with previous interpretations of MSGLs. We find some MSGLs have high reflectivity on their crest, interpreted as water bodies overlying high porosity sediment, whereas the trough around and the upstream end of some landforms consist of low porosity material. Integrating these different observations, we place constraints on possible explanations for the occurrence of water on the crest of landforms.

show abstract

Spatial Variation in Radar-Derived Basal Properties of Rutford Ice Stream, West Antarctica

Cited by 2 publications

References 1 publication

Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica

Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica

Radar Derived Subglacial Properties and Landforms Beneath Rutford Ice Stream, West Antarctica

Contact Info

Product

Resources

About