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dc.contributor.authorHofstede, C.
dc.contributor.authorChristoffersen, P.
dc.contributor.authorHubbard, B.
dc.contributor.authorDoyle, S.H.
dc.contributor.authorYoung, T.J.
dc.contributor.authorDiez, A.
dc.contributor.authorEisen, O.
dc.contributor.authorHubbard, Alun Lloyd
dc.date.accessioned2018-08-22T08:40:52Z
dc.date.available2018-08-22T08:40:52Z
dc.date.issued2018-01-09
dc.description.abstractOutlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast‐flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near the centerline, 30 km upstream of the calving front, to interpret the physical nature of the ice and bed. We identify one notably englacial and two notably subglacial seismic reflections on both profiles. The englacial reflection represents a change in crystal orientation fabric, interpreted to be the Holocene‐Wisconsin transition. From Amplitude‐Versus‐Angle (AVA) analysis we infer that the deepest ∼80 m of ice of the parallel‐flow profile below this reflection is anisotropic with an enhancement of simple shear of ∼2. The ice is underlain by ∼45 m of unconsolidated sediments, below which there is a strong reflection caused by the transition to consolidated sediments. In the across‐flow profile subglacial properties vary over small scale and the polarity of the ice‐bed reflection switches from positive to negative. We interpret these as patches of different basal slipperiness associated with variable amounts of water. Our results illustrate variability in basal properties, and hence ice‐bed coupling, at a spatial scale of ∼100 m, highlighting the need for direct observations of the bed to improve the basal boundary conditions in ice‐dynamic models.en_US
dc.description.sponsorshipUK National Environment Research Councilen_US
dc.descriptionSource at <a href=https://doi.org/10.1002/2017JF004297> https://doi.org/10.1002/2017JF004297</a>.en_US
dc.identifier.citationHofstede, C., Christoffersen, P., Hubbard, B., Doyle, S.H., Young, T., Diez, A., ... Hubbard, A.L. (2018). Physical Conditions of Fast Glacier Flow: 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland. Journal of Geophysical Research - Earth Surface, 123(2), 349-362. https://doi.org/10.1002/2017JF004297en_US
dc.identifier.cristinIDFRIDAID 1570392
dc.identifier.doi10.1002/2017JF004297
dc.identifier.issn2169-9003
dc.identifier.issn2169-9011
dc.identifier.urihttps://hdl.handle.net/10037/13525
dc.language.isoengen_US
dc.publisherAmerican Geophysical Union (AGU)en_US
dc.relation.journalJournal of Geophysical Research - Earth Surface
dc.relation.projectIDinfo:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/en_US
dc.rights.accessRightsopenAccessen_US
dc.subjectVDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Kvartærgeologi, glasiologi: 465en_US
dc.subjectVDP::Mathematics and natural science: 400::Geosciences: 450::Quaternary geology, glaciology: 465en_US
dc.subjectsubglacialen_US
dc.subjectslidingen_US
dc.subjectdeformationen_US
dc.subjectanisotropyen_US
dc.subjectpatchesen_US
dc.subjectseismicen_US
dc.titlePhysical Conditions of Fast Glacier Flow: 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenlanden_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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