Configuration and timing of Ungava Bay ice streams, Labrador-Ungava, Canada

Jansson, Krister N.; Stroeven, Arjen P.; Klemån, Johan

doi:10.1080/03009480310001146

Cited by 22 publications

(32 citation statements)

References 31 publications

(42 reference statements)

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“…A growing body of research is exploring the evolution of bedrock bedforms 67 and the implications for understanding ice sheet and ice stream dynamics. Studies have been 68 undertaken on submarine and on terrestrial landforms, reporting roches moutonnées and 69 whalebacks (e.g., Gordon, 1981;Sugden et al, 1992;Roberts and Long, 2005;Roberts et al, 2010; 70 Krabbendam and Glasser, 2011), large glacially moulded bedrock ridges often controlled by bedrock 71 structure (Roberts et al, 2010), mega-scale crag-and-tail forms (Jansson et al, 2003; Ottesen et al, 72 2008), erosional mega-grooves (Bradwell et al, 2008;Roberts et al, 2010), crag and tails, and other 73 crudely streamlined bedforms with blunt stoss and tapered lee sides (Lowe and Anderson, 2002; Ó 74 Cofaigh et al, 2002;Ó Cofaigh et al, 2013). In central west Greenland, sedimentary bedforms are 75 sparse, and areal scour dominates low elevation terrain (< 1000 m above sea level, asl) (Sugden, 76 1974; Glasser and Warren, 1990;Roberts and Long, 2005), so the majority of terrestrial glacial 77 landforms are erosional.…”

Section: Importance Of Glacial Bedforms 42mentioning

confidence: 99%

Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

et al. 2015

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Citation for published item:vneD FF nd oertsD hFrF nd eD fFF nd ¡ y gofighD gF nd ieliD eF @PHISA 9gontrols on suglil edrok edform development t the se of the ummnnq se tremD est qreenlndF9D qeomorphologyFD PQI F ppF QHIEQIQF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This paper investigates the controls on the formation of subglacially eroded bedrock bedforms 17 beneath the topographically confined region upstream of the Uummannaq Ice Stream (UIS). During 18 the last glacial cycle, palaeoglaciological conditions are believed to have been similar for all sites in 19 the study, characterised by thick, fast-flowing ice moving over a rigid bedrock bed. Classic bedrock 20 bedforms indicative of glacially eroded terrain were mapped, including p-forms, roches moutonnées, 21 and whalebacks. Bedform long axes and plucked face orientations display close correlation (parallel 22 and perpendicular) to palaeo-ice flow directions inferred from striae measurements. Across all sites, 23 elongation ratios (length to width) varied by an order of magnitude between 0.8:1 and 8.4:1. 24Bedform properties (length, height, width, and long axis orientation) from four subsample areas, 25 *Revised manuscript with no changes marked Click here to view linked References 2 form morphometrically distinct populations, despite their close proximity and hypothesised 26 similarity in palaeoglaciological conditions. 27 28Variations in lithology and geological structures (e.g., joint frequency; joint dip; joint orientation; 29 bedding plane thickness; and bedding plane dip) provide lines of geological weakness, which focus 30 the glacial erosion, in turn controlling bedform geometries. Determining the relationship(s) between 31 bedding plane dip relative to palaeo-ice flow and bedform shape, relative length, amplitude, and 32 wavelength has important ramifications for understanding subglacial bed roughness, cavity 33 formation, and likely erosion style (quarrying and/or abrasion) at the ice-bed interface. This paper 34 demonstrates a direct link between bedrock bedform geometries and geological structure and 35 emphasises the need to understand bedrock bedform characteristics when reconstructing 36 palaeoglaciological conditions. 37 38Keywords: ice stream; glacial erosion; bedrock bedform; abrasion; quarrying; Greenland ice sheet 39 3 Introduction 40 41 Importance of glacial bedforms 42An understanding of past ice sheet dynamics can significantly improve our understanding of current 43 and potential future ...

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Section: Importance Of Glacial Bedforms 42mentioning

confidence: 99%

Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

et al. 2015

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“…They inferred several discrete palaeo-ice-flow sets based on the distribution of bedforms. Furthermore, Jansson et al (2003) suggested that the high density and high elongation of drift and bedrock features indicated that the Ungava Bay area acted as the pathway of a major Laurentide ice stream. Roberts and Long (2005) examined glacial bedforms in gneissose bedrock adjacent to the fast-flowing Jakobshavns Isbrae in west Greenland.…”

Section: Previous Work Using Large-scale Bedrock Forms To Infer Palamentioning

confidence: 99%

“…However, only a few studies have attempted to make inferences about palaeo-ice-flow velocity based on medium-and large-scale glacially eroded bedrock features. These include key papers by Evans (1996), Hall andGlasser (2003), Jansson et al (2003), and Roberts and Long (2005). Evans (1996) showed how subtle differences in bedform morphology could be used as a proxy for s ubglacial pressure conditions.…”

Section: Previous Work Using Large-scale Bedrock Forms To Infer Palamentioning

confidence: 99%

Megagrooves and streamlined bedrock in NW Scotland: The role of ice streams in landscape evolution

2008

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New multibeam bathymetry data, onshore high-resolution elevation data (NEXTMap) and fieldwork in the Ullapool area of NW Scotland reveal large-scale megagrooves and streamlined bedrock forms in a well-defined ~20-km wide zone. The landsystem is typical of a coherent flow corridor within a grounded ice sheet on bedrockdominated terrain. We describe the morphology of the large-scale features, discuss their likely formation, and consider the wider implications for ice-sheet dynamics. Based on the strongly convergent bedform distribution, the presence of megagrooves and highly elongate bedrock forms, we interpret the erosional landscape to be the signature of a fast-flowing tributary that once fed the The Minch palaeo-ice stream -a major artery of the last British-Irish ice sheet. The exact genesis of bedrock megagrooves remains uncertain, although focused subglacial abrasion is likely to have carved most of the shallow, strongly parallel, features; whilst glacial meltwater may have carved or modified others. Bedform morphometry is used to discriminate zones reflecting the degree of glacial streamlining (elongation ratios <5:1 or >5:1). We interpret these zones to represent the transition from potentially cold-based slow ice-sheet flow to warm-based fast flow. Based on these results, and the presence of ribbed moraines, we suggest a bedform continuum model for onset zones of palaeoice streams on rigid beds. Rapid spatial bedform evolution is suggested to reflect an increase in subglacial erosive power that may be diagnostic of palaeo-ice-sheet thermal boundaries (i.e. from cold-to warm-based), and is also consistent with the expected downstream increase in ice velocity within an ice-stream onset zone. Finally, this study speculates on the role played by basal meltwater in ice-stream initiation and the role of ice streams and their tributaries in landscape evolution.

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“…10C) (Stokes and Clark, 2002). The bedforms include whalebacks, which are often associated with periods of former fast-flow (Jansson et al, 2003).…”

Section: Bedform Progression and Elongationmentioning

confidence: 99%

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

Graham

Larter

Gohl

et al. 2009

Quaternary Science Reviews

175

173

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a b s t r a c tThe presence of a complex bedform arrangement on the sea floor of the continental shelf in the western Amundsen Sea Embayment, West Antarctica, indicates a multi-temporal record of flow related to the activity of one or more ice streams in the past. Mapping and division of the bedforms into distinct landform assemblages reveals their time-transgressive history, which implies that bedforms can neither be considered part of a single downflow continuum nor a direct proxy for palaeo-ice velocity, as suggested previously. A main control on the bedform imprint is the geology of the shelf, which is divided broadly between rough bedrock on the inner shelf, and smooth, dipping sedimentary strata on the middle to outer shelf. Inner shelf bedform variability is well preserved, revealing information about local, complex basal ice conditions, meltwater flow, and ice dynamics over time. These details, which are not apparent at the scale of regional morphological studies, indicate that past ice streams flowed across the entire shelf at times, and often had onset zones that lay within the interior of the Antarctic Ice Sheet today. In contrast, highly elongated subglacial bedforms on sedimentary strata of the middle to outer shelf represent a timeslice snapshot of the last activity of ice stream flow, and may be a truer representation of fast palaeo-ice flow in these locations. A revised model for ice streams on the shelf captures complicated multi-temporal bedform patterns associated with an Antarctic palaeo-ice stream for the first time, and confirms a strong substrate control on a major ice stream system that drained the West Antarctic Ice Sheet during the Late Quaternary.

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Configuration and timing of Ungava Bay ice streams, Labrador-Ungava, Canada

Cited by 22 publications

References 31 publications

Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

Megagrooves and streamlined bedrock in NW Scotland: The role of ice streams in landscape evolution

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

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