Dynamics of ice flow and sediment transport at a polythermal glacier terminus: Storglaciaren, Sweden

Moore, Peter L.

doi:10.31274/etd-180810-2561

Cited by 6 publications

(15 citation statements)

References 87 publications

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“…). However, radar profiles and borehole video inspection of the area indicate that the feature does not continue as far south as the glacier centreline (Moore ). The debris band thus appears to be limited to the portion of the terminus abutting the small moraine mound (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden

Moore

Iverson

Uno

et al. 2012

Boreas

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P. 2013 (January): Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden.Internal structure, stable isotope composition and tritium concentration were measured in and around debrisbearing ice at the margin of Storglaciären, where englacial debris bands have previously been inferred to form by thrusting. Two types of debris bands were distinguished: (i) an unsorted diamicton band that is laterally continuous for more than 200 m, and (ii) well-sorted sand and gravel bands that are lenticular and discontinuous. Above-background tritium levels and enrichment of d 18 O and dD in ice from the diamicton band indicate entrainment by basal freeze-on since 1952. Isotopic enrichment and tritium-free ice in the sandy debris bands also indicate entrainment in freezing water, but prior to 1952. The lenticular cross-section, sorting and stratification of the sandy bands suggest that they were deposited englacially. The basally accreted diamicton band has been elevated tens of metres above the bed and presently overlies the englacially deposited sandy bands, suggesting that the stratigraphy has been disrupted. Three interpretations could account for these observations: (i) thrusting of fast-moving ice over slow, marginal ice uplifting recently accreted basal ice along the fault; (ii) folding near the margin, elevating young basal ice over older basal and englacial ice; and (iii) debris-band formation by an unknown mechanism and subsequent contamination of ice geochemical properties by meltwater flow through debris bands. Although none of these interpretations is consistent with all measurements, folding is most compatible with observations and local ice-flow kinematics.

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Section: Resultsmentioning

confidence: 99%

“…Sediment concentration varies from 45% to more than 75% by volume (Glasser et al . ; Uno ; Moore ). Stable oxygen isotope measurements of Glasser et al .…”

Section: Field Settingmentioning

confidence: 99%

Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden

Moore

Iverson

Uno

et al. 2012

Boreas

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“…3d). No up-glacier-dipping structure is evident in this profile at the expected location of the debris band, but a survey in the same area in late summer 2008 revealed a faint up-glacier-dipping reflection there (Moore, 2009). No distinct englacial planar reflections are visible in the south transect (Fig.…”

Section: Field Datamentioning

confidence: 86%

Effect of a cold margin on ice flow at the terminus of Storglaciären, Sweden: implications for sediment transport

Moore¹,

Iverson²,

Brugger

et al. 2011

J. Glaciol.

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The cold-based termini of polythermal glaciers are usually assumed to adhere strongly to an immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier. This compressive environment is commonly thought to uplift basal sediment to the surface of the glacier by folding and thrust faulting. We present model and field evidence from the terminus of Storglaciären, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier. Ice temperatures indicate that basal freezing occurs in this zone at 10 −1 -10 −2 m a −1 , but model results indicate that basal motion at rates greater than 1 m a −1 must, nevertheless, persist there for surface and basal velocities to be consistent with measurements. Estimated longitudinal compressive stresses of 20-25 kPa within the terminus further indicate that basal resistance offered by the cold-based terminus is small. These results indicate that where polythermal glaciers are underlain by unlithified sediments, ice-flow trajectories and sediment transport pathways may be affected by subglacial topography and hydrology more than by the basal thermal regime.

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“…In contrast, the study site at West Washmawapta Glacier is located near the lateral margin of the glacier and just up‐flow from a bedrock riegel in a region with an adverse basal slope [ Sanders et al , 2010]; the significant departure from a power law distribution at low interevent times observed here might therefore indicate that the riegel provides an effective physiographic obstacle to flow. Conditions at Storglaciären might be expected to fall between these two extremes: the study site here is soft‐bedded and flow results mainly from basal motion, but flow in this near‐terminal region shows generally uniform longitudinal compression [ Moore , 2009]. Further study will be necessary to determine the factors that control the form of these distributions.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…Ice in this location is approximately 40 m thick, with a cold surface layer of ∼25 m thickness overlying temperate ice; this cold layer ensures that the upper portion of boreholes drilled there freeze closed within a few days (which permits both negative pressure values and pressure heads in excess of the local ice thickness to be achieved). The mean annual surface velocity in this region is ∼9 m/yr, with slightly higher summer velocities (∼11 m/yr); repeat borehole inclinometry studies indicate that almost all of the measured surface velocity here is due to basal motion [ Moore , 2009]. The boreholes for pressure pulse measurement were drilled to within approximately 1 m of the glacier bed and instrumented with pressure transducers (Omega Engineering, Inc. Model PX302; response time: 1 ms).…”

Section: Field Datamentioning

confidence: 99%

Using pressure pulse seismology to examine basal criticality and the influence of sticky spots on glacial flow

Kavanaugh¹,

Moore²,

Dow³

et al. 2010

J. Geophys. Res.

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[1] Here we report results of water pressure pulse studies conducted at Storglaciären (Sweden) and West Washmawapta Glacier (British Columbia, Canada). Comparison of pressure pulse records with meteorological conditions at Storglaciären indicates that several periods of increased basal slip activity observed during a 10 day interval of summer 2008 were due to precipitation loading of the glacier surface, rather than to infiltration of surface water to the glacier bed; this indicates that the glacier bed was close to the failure strength for much of this interval. Pressure pulse magnitudes for the two glaciers were well-fit by power law distributions similar to those earlier observed at Trapridge Glacier (and similar in form to the Gutenberg-Richter relationship commonly used in seismology), suggesting that the mechanical processes that give rise to these distributions are robust features of soft-bedded glaciers. In contrast, interevent time distributions for both glaciers diverge from those observed at Trapridge Glacier for short recurrence intervals, suggesting that the factors that govern the rate at which these processes occur differ between glaciers. An examination of pressure pulse characteristics at West Washmawapta Glacier indicates that the establishment of a basal drainage system in summer 2008 resulted in increased stability and reduced sensitivity to meltwater input, suggesting that common assumptions about the relationship between meltwater production and ice flow are oversimplified. These results demonstrate that water pressure pulse observations can provide valuable insight into the dynamics of soft-bedded glaciers.Citation: Kavanaugh, J. L., P. L. Moore, C. F. Dow, and J. W. Sanders (2010), Using pressure pulse seismology to examine basal criticality and the influence of sticky spots on glacial flow,

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Dynamics of ice flow and sediment transport at a polythermal glacier terminus: Storglaciaren, Sweden

Cited by 6 publications

References 87 publications

Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden

Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden

Effect of a cold margin on ice flow at the terminus of Storglaciären, Sweden: implications for sediment transport

Using pressure pulse seismology to examine basal criticality and the influence of sticky spots on glacial flow

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