Landform assemblages and sedimentary processes along the Norwegian Channel Ice Stream

Ottesen, Dag; Stokes, Chris R.; Bøe, Reidulv; Rise, Leif; Longva, Oddvar; Thorsnes, Terje; Olesen, Odleiv; Bugge, Tom; Lepland, Aivo; Hestvik, Ole B.

doi:10.1016/j.sedgeo.2016.01.024

Cited by 31 publications

(23 citation statements)

References 74 publications

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“…A major deglaciation event at around this time is also substantiated by AMS radiocarbon ages of plant remains from cored lacustrine sediments on Jæren, somewhat farther south of the fjord (Knudsen, ). Finally, thick sequences (up to several hundred meters) of glaciomarine sediments around the mouth of Boknafjorden that accumulated before 13.5 cal ka BP (Bøe et al ., ) are consistent with a prolonged period of ice stability during deglaciation (Svendsen et al ., ; Ottesen et al ., ). Thus, we find it plausible that ∼16 ka marks the end of a prolonged halt or re‐advance of the ice front position at the mouth of Boknafjorden.…”

Section: Discussionmentioning

confidence: 97%

Deglaciation of Boknafjorden, south‐western Norway

Gump

Briner

Mangerud

et al. 2017

J Quaternary Science

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We present 30 10Be ages from glacial erratic boulders to constrain the deglaciation of the Scandinavian Ice Sheet in the Boknafjorden region, south‐western Norway. The southern part of the island Karmøy, located at the mouth of this fjord system, became free of glacier ice before 16 ka, probably because of the sudden break up of the Norwegian Channel Ice Stream at 20–18 ka. The ice sheet margin then stabilized at the fjord mouth until a second retreat phase commenced at or slightly before 16 ka. A calving bay developed in Boknafjorden after 16 ka, and in the course of the next millennium the ice front retreated to the inner fjord branches. In contrast, a major outlet glacier that filled the Hardangerfjorden farther to the north did not start to retreat from the fjord mouth until after 15 ka, probably in response to the Bølling warming. Thus, not only did Boknafjorden experience major retreat before Bølling warmth, but there was a variable response of south‐western fjord glaciers in Norway consistent with prior observations of non‐climatic forcing of marine‐terminating outlet glaciers.

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Section: Discussionmentioning

confidence: 97%

Deglaciation of Boknafjorden, south‐western Norway

Gump

Briner

Mangerud

et al. 2017

J Quaternary Science

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“…Wellner et al , ; Nitsche et al , ]. The irregular surface depressions in Figure c bear resemblance to hill‐hole pairs observed in bathymetric data in the Norwegian Channel where they are thought to represent the imprint of sediment slabs that froze onto the glacier sole and were removed/displaced [ Ottesen et al , ]. However, if the surface depressions in Figure c are similarly interpreted as hill‐hole pairs, their estimated volumes are an order of magnitude smaller than those observed in the Norwegian Channel.…”

Section: Discussionmentioning

confidence: 95%

High‐resolution sub‐ice‐shelf seafloor records of twentieth century ungrounding and retreat of Pine Island Glacier, West Antarctica

et al. 2017

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Pine Island Glacier Ice Shelf (PIGIS) has been thinning rapidly over recent decades, resulting in a progressive drawdown of the inland ice and an upstream migration of the grounding line. The resultant ice loss from Pine Island Glacier (PIG) and its neighboring ice streams presently contributes an estimated ∼10% to global sea level rise, motivating efforts to constrain better the rate of future ice retreat. One route toward gaining a better understanding of the processes required to underpin physically based projections is provided by examining assemblages of landforms and sediment exposed over recent decades by the ongoing ungrounding of PIG. Here we present high‐resolution bathymetry and sub‐bottom‐profiler data acquired by autonomous underwater vehicle (AUV) surveys beneath PIGIS in 2009 and 2014, respectively. We identify landforms and sediments associated with grounded ice flow, proglacial and subglacial sediment transport, overprinting of lightly grounded ice‐shelf keels, and stepwise grounding line retreat. The location of a submarine ridge (Jenkins Ridge) coincides with a transition from exposed crystalline bedrock to abundant sediment cover potentially linked to a thick sedimentary basin extending upstream of the modern grounding line. The capability of acquiring high‐resolution data from AUV platforms enables observations of landforms and understanding of processes on a scale that is not possible in standard offshore geophysical surveys.

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“…Figure 17. Minch Ice Stream and Hebridean Ice Stream; Bradwell et al, 2007;Bradwell, 2013;Bradwell and Stoker, 2015;Dove et al, 2015;Krabbendam et al, 2016) and Scandanavia (Ottesen et al, 2016). The NSL departed the north Norfolk coast after 22.8-21.5 ka BP, leaving till wedges and arcuate moraine complexes on the seafloor as it migrated northwards (green lines; Dove et al, 2017;Roberts et al, 2018).…”

Section: Subglacial Sediment and Landform Genesismentioning

confidence: 99%

“…The retreat of the NSL based on new and existing radiocarbon and OSL ages from the east coast of the UK and the offshore areas of Durham and Northumberland. The transition from scoured and streamlined bedrock terrain to MSGL has also been used to infer an increase in ice flow velocity as ice passes from hard to soft bedded substrates in other ice stream onset settings such as the Hebridean Ice Stream and Norwegian Channel ice Stream (Dove et al, 2015;Ottesen et al, 2016). New dates from the Durham area and offshore suggest the ice margin became quasi-stable as a large grounding zone wedge developed (W1) at some time around 19.5-19.9 ka.…”

Section: Subglacial Sediment and Landform Genesismentioning

confidence: 99%

The mixed‐bed glacial landform imprint of the North Sea Lobe in the western North Sea

Roberts

Grimoldi

Callard

et al. 2019

Earth Surf Processes Landf

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During the last glacial cycle an intriguing feature of the British‐Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England. Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega‐scale glacial lineations and grounding zone wedges. The resultant ‘mixed‐bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont‐lobe margin with a net surplus of sediment to a partially erosive, quasi‐stable, marine‐terminating, ice stream lobe as the NSL withdrew northwards. Glaciomarine sediments (AF4) drape the underlying subglacial mixed‐bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed‐bed landsystem being a response to grounding line instability. © 2018 John Wiley & Sons, Ltd.

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Landform assemblages and sedimentary processes along the Norwegian Channel Ice Stream

Cited by 31 publications

References 74 publications

Deglaciation of Boknafjorden, south‐western Norway

Deglaciation of Boknafjorden, south‐western Norway

High‐resolution sub‐ice‐shelf seafloor records of twentieth century ungrounding and retreat of Pine Island Glacier, West Antarctica

The mixed‐bed glacial landform imprint of the North Sea Lobe in the western North Sea

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