Subglacial till behaviour derived from in situ wireless multi-sensor subglacial probes: Rheology, hydro-mechanical interactions and till formation

Hart, Jane K.; Rose, Kathryn C.; Martinez, Kirk

doi:10.1016/j.quascirev.2010.11.001

Cited by 27 publications

(15 citation statements)

References 102 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If water is able to flow into the dilating material, this leads to looser packing and a weakening of the sediment 21 , but if water is unable to flow into these spaces, this will result in a drop in water pressure and an increase in strength (dilation strengthening) 22 . Both of these states have been observed in laboratory tests in till 21,40 as well as from in situ studies beneath modern glaciers 37,41,42 .…”

Section: Introductionmentioning

confidence: 72%

“…The relationship between subglacial effective pressure (ice-overburden pressure minus the water pressure) and till strength can reflect changes in till behaviour. We use case stress as a proxy for till strength 37 in a similar way to previous studies using ploughmeters 41,42 . We also find both positive (probe 21 winter 2009/2010) and negative (probe 25) relationships (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Initial research led to a debate between purely linear viscous models 32 compared with plastic behaviour 33 . However, more recently various researchers have used a range of analytical techniques (in situ data, sedimentology, geotechnical experiments, computational modelling) to suggest that there may be different behaviours related to effective pressure 3,34–37 . These authors argue that at high effective pressures there is little movement (stick), at intermediate effective pressures there is creep (deformation), and at low effective pressures there is failure (slip).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

et al. 2019

Self Cite

View full text Add to dashboard Cite

Fluctuations in glacier motion are very common and are thought to be controlled by subglacial hydrology and till deformation. There are few instrumented studies that have monitored seasonal changes. We use the innovative Glacsweb subglacial in situ wireless probes, combined with dGPS and custom geophone data from an Icelandic soft-bedded temperate glacier, to show that there are two distinct seasonal styles of speed-up events. Relatively small diurnal events occur during the melt season, whilst during winter there are larger multi-day events related to positive degree days. These events are accompanied by a distinct pattern of till deformation and basal icequakes. We argue these reflect stick-slip motion which occurs when the glacier hydrological system is unable to accommodate the melt water flux generated by surface melt episodes. We show a rare fully instrumented coupled glacier/till record of contrasting summer and winter stick-slip motion and discuss its implication for till sedimentology.

show abstract

Section: Introductionmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Deviations occur throughout the stratigraphic column but at no critical point in the column nor in any specific direction, but rather changes in strength and direction appear to be somewhat arbitrary, probably a function of changing sediment rheology, porewater content and stress (cf. Kjaer et al, 2006;Hart, Rose, & Martinez, 2011;Phillips et al, 2018).…”

Section: Interpretations From O-28 Pit Pine Pointmentioning

confidence: 99%

Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada

Menzies

Paulen

Rice

et al. 2019

The Depositional Record

View full text Add to dashboard Cite

Investigations of glacial sediment exposures in a former open pit in the Pine Point Mining District, Northwest Territories, reveal evidence of changes in stress magnitude as exhibited by the movement of deformation ‘fronts’ within subglacial tills, as evident through micromorphological analysis. Indications of deformation, driven by stress fluctuations, were observed throughout a set of vertical subglacial till samples associated with the Laurentide Ice Sheet. These tills exhibit multiple sub‐lithofacies variations in concert with marked changes in microshear orientation, which can be directly related to changing stress levels within a subglacial deforming bed. The evidence of changes in till stress conditions is typical of subglacial tills occurring beneath an active temperate ice mass within a soft deforming bed. As differing ‘layers’ of till that form a mosaic‐like pattern become immobilized and ‘detached’ subjacent to the deforming bed sediments, a signature of this action is recorded within the tills as sequences of specific microstructures. These microstructures are part of a spectrum of micro‐forms that develop as consequence of changes in stress, porewater content and clay content within the ‘fault‐gouge’—like environment formed beneath an active temperate ice sheet. A model is developed that uses data from Pit O‐28 demonstrating where deformation ‘boundary front’ evidence in the form of deformation bands has developed as basal driven stress levels have penetrated active deforming sediments. The evidence from Pine Point indicates that till acts as an excellent palaeo‐strain record of past active glacial processes, subglacial basal thermal conditions and sediment mobility.

show abstract

“…These data streams are currently being used to investigate stick-slip behave as described in [1,2], and have previously been used to examine till behaviour [3]. Previous work by the Glacsweb team has tackled hardware design [4], implementing easily maintained code on the base stations [5,6] and analysing the subglacial node data [7].…”

Section: Introductionmentioning

confidence: 99%

Robust wireless sensor network performance analysis

Martinez

Basford

2011

2011 IEEE SENSORS Proceedings

View full text Add to dashboard Cite

Abstract-We show that a wireless sensor network system can be designed specifically for a set of complex deployment requirements and constraints. Among the design issues tackled are: low power design which copes with arctic winters and adaptive behaviour to cope with communications breakdowns. These techniques were implemented in a WSN deployment in Iceland in 2008 by the Glacsweb team. This paper shows how this has allowed base stations to survive the winter for the first time.Rather than scaling up the power sources to cope, the systems scale-back their activities, especially communications and dGPS sensing. Similarly instead of overdesigning the radio networks, disconnection periods were managed using large multi-level buffers. The overall success was increased by techniques introduced after the main deployment in 2008. The system is comprised of eight subglacial sensor nodes, connected to a base station on the glacier and a fixed reference station on the mountainside.

show abstract

Subglacial till behaviour derived from in situ wireless multi-sensor subglacial probes: Rheology, hydro-mechanical interactions and till formation

Cited by 27 publications

References 102 publications

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada

Robust wireless sensor network performance analysis

Contact Info

Product

Resources

About