Glacial sediment and landform record offshore NW Scotland: a fjord–shelf–slope transect through a Late Quaternary mid-latitude ice-stream system

Bradwell, Tom; Stoker, Martyn S.

doi:10.1144/m46.152

Cited by 7 publications

(9 citation statements)

References 37 publications

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“…Falcini and others: Quantifying bed roughness beneath contemporary and palaeo-ice streams fjord system (Bradwell and Stoker, 2016;Bradwell and others, 2016). Increases in ice velocity are inferred from changes to landform elongation ratios located on the central Minch inner shelf (East Shiant Bank), which Bradwell and Stoker (2015) suggested is caused by the bed substrate changing from rough bedrock to smooth sediment.…”

mentioning

confidence: 99%

Quantifying bed roughness beneath contemporary and palaeo-ice streams

et al. 2018

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Bed roughness is an important control on ice-stream location and dynamics. The majority of previous bed roughness studies have been based on data derived from radio-echo sounding (RES) transects across Antarctica and Greenland. However, the wide spacing of RES transects means that the links between roughness and flow are poorly constrained. Here, we use Digital Terrain Model/bathymetry data from a well-preserved palaeo-ice stream to investigate basal controls on the behaviour of contemporary ice streams. Artificial transects were set up across the Minch Palaeo-Ice Stream (NW Scotland) to mimic RES flight lines over Institute and Möller Ice Streams (Antarctica). We then explored how different data-resolution, transect orientation and spacing, and different methods, impact roughness measurements. Our results show that fast palaeo-ice flow can occur over a rough, hard bed, not just a smooth, soft bed, as previous work has suggested. Smooth areas of the bed occur over both bedrock and sediment covered regions. Similar trends in bed roughness values were found using Fast Fourier Transform analysis and standard deviation methods. Smoothing of bed roughness results can hide important details. We propose that the typical spacing of RES transects is too wide to capture different landform assemblages and that transect orientation influences bed roughness measurements in both contemporary and palaeo-ice-stream setting.

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confidence: 99%

Quantifying bed roughness beneath contemporary and palaeo-ice streams

et al. 2018

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“…Dickens et al 2016;Graham & Hodgson 2016). The volume also has a temporal reach that includes many Quaternary examples, from the now deglaciated shelves and fjords of the northern mid-latitudes, such as those offshore of the British Isles and eastern Canada, and in the Baltic (Bradwell & Stoker 2016b;Greenwood et al 2016;, to the fjords of New Zealand (Barnes et al 2016a, b) and the continental shelf of Antarctica in the Southern Hemisphere Klages et al 2016; Simkins et al Further back in time, 3D seismic-reflection methods allow examples of glacimarine landforms to be drawn not only from the seafloor, encompassing the LGM and subsequent deglaciation where sedimentation rates are low and landforms are not buried by post-glacial sedimentation, but also from much deeper in the record. Published research using 3D seismic datasets is currently relatively limited, but available cubes collected by industry have allowed some investigations of deeply buried palaeo-shelf surfaces and their landforms, especially in the Quaternary sediments of the Norwegian margin and the North Sea (e.g.…”

Section: Geographical Coveragementioning

confidence: 99%

“…5). The environmental continuum extends from relatively mild glacier-influenced environments such as those of the western British Isles and the Gulf of Maine (Bradwell & Stoker 2016b;, through the intermediate environments of, for example, Svalbard and the Antarctic Peninsula Dowdeswell et al 2016b), to the coldest settings of the Arctic Ocean and East Antarctica O'Brien et al 2016). The ancient glacimarine system of Late Ordovician northern Africa (Le Heron 2016) concludes this section of the Atlas, noting that it is interpreted as a relatively mild palaeo-glacial setting.…”

Section: Structure and Organization Of The Atlasmentioning

confidence: 99%

Introduction: an Atlas of Submarine Glacial Landforms

Dowdeswell

Canals

Jakobsson

et al. 2016

Memoirs

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Glacial landforms and sediments exposed sub-aerially have been the subject of description, analysis and interpretation for more than a century (e.g. De Laski 1864; De Geer 1889). Indeed, such features provided important initial observations informing Louis Agassiz's ideas that ice was a key instrument in sculpting the landscape and that glaciers and ice sheets had extended to mid-latitudes during the past, implying that Earth's climate must have changed considerably through time (Agassiz 1840). It is only in the last few decades that attention has begun to focus on the marine evidence for the past growth and decay of ice sheets that is recorded in submarine landforms and sediments preserved on high-latitude continental margins. This interest has been driven, in part, by the recognition that sediments deposited below wave-base are often well preserved in the Quaternary geological record, and may be less subject to erosion and reworking than their terrestrial counterparts. In addition, new marine-geophysical technologies have enabled increasingly high-resolution imaging and penetration of the high-latitude seafloor, most notably using multibeam swathbathymetric and three-dimensional (3D) seismic-reflection methods, and modern ice-strengthened and ice-breaking research vessels have allowed the effective deployment of these increasingly sophisticated instruments in the often ice-infested waters of the Arctic and Antarctic seas.The geological record from high-latitude continental margins is now recognized to provide key information on former ice-sheet extent, the direction and nature of past ice flow and dynamics, and a well-preserved window on the detailed form and composition of former ice-sheet beds (e.g. Ottesen et al. 2005;Anderson et al. 2014;Jakobsson et al. 2014). The geometry and distribution of submarine glacial landforms on the seafloor, and the underlying glacial-sedimentary stratigraphic record with which they are associated, is the topic of this volume. The aims and purpose of the Atlas are: (1) to provide a comprehensive set of examples of the full range of individual submarine glacial landforms and assemblages of landforms produced beneath and at the marine margins of glaciers and ice sheets; and (2) to integrate this information over entire fjord -shelf -slope systems across the full climatic range of glacier-influenced marine settings, in order to better understand the morphology and architecture of glacimarine environments. This evidence is used to reconstruct the growth, decay and dynamics of past ice sheets, including those of Quaternary and more ancient ice ages.

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“…Over the last 15 years, the Quaternary geology and glacial geomorphology of the MnIS have been studied in some detail. These studies have focused on: the landform evidence of ice streaming onshore (Bradwell et al ., 2007, 2008a: Hughes et al ., 2014); the submarine sediment and landform record (Bradwell et al ., 2008a; Stoker et al ., 2009; Bradwell and Stoker, 2015a, 2016); the evidence for thermal zonation and tributary flow (Ballantyne, 2010; Fabel et al ., 2012; Bradwell, 2013); and most recently the submarine geological record and chronology of grounding‐line retreat (Bradwell et al ., 2019). In addition to this, numerical modelling has shown the MnIS to be a dynamic yet quasi‐stable feature that dominated flow geometry in the ice sheet's NW sector (Boulton and Hagdorn, 2006; Hubbard et al ., 2009; Gandy et al ., 2019).…”

Section: Introductionmentioning

confidence: 99%

Pattern, style and timing of British–Irish Ice Sheet advance and retreat over the last 45 000 years: evidence from NW Scotland and the adjacent continental shelf

Bradwell

Fabel

Clark

et al. 2021

J Quaternary Science

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Predicting the future response of ice sheets to climate warming and rising global sea level is important but difficult. This is especially so when fast‐flowing glaciers or ice streams, buffered by ice shelves, are grounded on beds below sea level. What happens when these ice shelves are removed? And how do the ice stream and the surrounding ice sheet respond to the abruptly altered boundary conditions? To address these questions and others we present new geological, geomorphological, geophysical and geochronological data from the ice‐stream‐dominated NW sector of the last British–Irish Ice Sheet (BIIS). The study area covers around 45 000 km2 of NW Scotland and the surrounding continental shelf. Alongside seabed geomorphological mapping and Quaternary sediment analysis, we use a suite of over 100 new absolute ages (including cosmogenic‐nuclide exposure ages, optically stimulated luminescence ages and radiocarbon dates) collected from onshore and offshore, to build a sector‐wide ice‐sheet reconstruction combining all available evidence with Bayesian chronosequence modelling. Using this information we present a detailed assessment of ice‐sheet advance/retreat history, and the glaciological connections between different areas of the NW BIIS sector, at different times during the last glacial cycle. The results show a highly dynamic, partly marine, partly terrestrial, ice‐sheet sector undergoing large size variations in response to sub‐millennial‐scale climatic (Dansgaard–Oeschger) cycles over the last 45 000 years. Superimposed on these trends we identify internally driven instabilities, operating at higher frequency, conditioned by local topographic factors, tidewater dynamics and glaciological feedbacks during deglaciation. Specifically, our new evidence indicates extensive marine‐terminating ice‐sheet glaciation of the NW BIIS sector during Greenland Stadials 12 to 9 – prior to the main ‘Late Weichselian’ ice‐sheet glaciation. After a period of restricted glaciation, in Greenland Interstadials 8 to 6, we find good evidence for rapid renewed ice‐sheet build‐up in NW Scotland, with the Minch ice‐stream terminus reaching the continental shelf edge in Greenland Stadial 5, perhaps only briefly. Deglaciation of the NW sector took place in numerous stages. Several grounding‐zone wedges and moraines on the mid‐ and inner continental shelf attest to significant stabilizations of the ice‐sheet grounding line, or ice margin, during overall retreat in Greenland Stadials 3 and 2, and to the development of ice shelves. NW Lewis was the first substantial present‐day land area to deglaciate, in the first half of Greenland Stadial 3 at a time of globally reduced sea‐level c. 26 kabp, followed by Cape Wrath at c. 24 kabp. The topographic confinement of the Minch straits probably promoted ice‐shelf development in early Greenland Stadial 2, providing the ice stream with additional support and buffering it somewhat from external drivers. However, c. 20–19 kabp, as the grounding‐line migrated into shoreward deepening water, co...

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Glacial sediment and landform record offshore NW Scotland: a fjord–shelf–slope transect through a Late Quaternary mid-latitude ice-stream system

Cited by 7 publications

References 37 publications

Quantifying bed roughness beneath contemporary and palaeo-ice streams

Quantifying bed roughness beneath contemporary and palaeo-ice streams

Introduction: an Atlas of Submarine Glacial Landforms

Pattern, style and timing of British–Irish Ice Sheet advance and retreat over the last 45 000 years: evidence from NW Scotland and the adjacent continental shelf

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