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dc.contributor.authorBradwell, Tomen_UK
dc.contributor.authorFabel, Dereken_UK
dc.contributor.authorClark, Chris Den_UK
dc.contributor.authorChiverrell, Richard Cen_UK
dc.contributor.authorSmall, Daviden_UK
dc.contributor.authorSmedley, Rachel Ken_UK
dc.contributor.authorSaher, Margot Hen_UK
dc.contributor.authorMoreton, Steven Jen_UK
dc.contributor.authorDove, Daytonen_UK
dc.contributor.authorCallard, S Louiseen_UK
dc.contributor.authorDuller, Geoff A Ten_UK
dc.contributor.authorMedialdea, Aliciaen_UK
dc.contributor.authorBateman, Mark Den_UK
dc.contributor.authorBurke, Matthew Jen_UK
dc.contributor.authorMcDonald, Neilen_UK
dc.description.abstractPredicting 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 ka bp, followed by Cape Wrath at c. 24 ka bp. 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 ka bp, as the grounding‐line migrated into shoreward deepening water, coinciding with a marked change in marine geology and bed strength, the ice stream became unstable. We find that, once underway, grounding‐line retreat proceeded in an uninterrupted fashion with the rapid loss of fronting ice shelves – first in the west, then the east troughs – before eventual glacier stabilization at fjord mouths in NW Scotland by ~17 ka bp. Around the same time, ~19–17 ka bp, ice‐sheet lobes readvanced into the East Minch – possibly a glaciological response to the marine‐instability‐triggered loss of adjacent ice stream (and/or ice shelf) support in the Minch trough. An independent ice cap on Lewis also experienced margin oscillations during mid‐Greenland Stadial 2, with an ice‐accumulation centre in West Lewis existing into the latter part of Heinrich Stadial 1. Final ice‐sheet deglaciation of NW mainland Scotland was punctuated by at least one other coherent readvance at c. 15.5 ka bp, before significant ice‐mass losses thereafter. At the glacial termination, c. 14.5 ka bp, glaciers fed outwash sediment to now‐abandoned coastal deltas in NW mainland Scotland around the time of global Meltwater Pulse 1A. Overall, this work on the BIIS NW sector reconstructs a highly dynamic ice‐sheet oscillating in extent and volume for much of the last 45 000 years. Periods of expansive ice‐sheet glaciation dominated by ice‐streaming were interspersed with periods of much more restricted ice‐cap or tidewater/fjordic glaciation. Finally, this work indicates that the role of ice streams in ice‐sheet evolution is complex but mechanistically important throughout the lifetime of an ice sheet – with ice streams contributing to the regulation of ice‐sheet health but also to the acceleration of ice‐sheet demise via marine ice‐sheet instabilities.en_UK
dc.relationBradwell T, Fabel D, Clark CD, Chiverrell RC, Small D, Smedley RK, Saher MH, Moreton SJ, Dove D, Callard SL, Duller GAT, Medialdea A, Bateman MD, Burke MJ & McDonald N (2021) 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. Journal of Quaternary Science.
dc.rights© 2021 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License (, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.en_UK
dc.subjectBayesian modellingen_UK
dc.subjectice streamen_UK
dc.subjectmarine ice‐sheet instabilityen_UK
dc.titlePattern, 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 shelfen_UK
dc.typeJournal Articleen_UK
dc.citation.jtitleJournal of Quaternary Scienceen_UK
dc.type.statusVoR - Version of Recorden_UK
dc.contributor.funderNERC Natural Environment Research Councilen_UK
dc.description.notesOutput Status: Forthcoming/Available Online Additional co-authors: Sean Gilgannon, Sally Morgan, David H. Roberts, Colm ó Cofaighen_UK
dc.contributor.affiliationBiological and Environmental Sciencesen_UK
dc.contributor.affiliationUniversity of Glasgowen_UK
dc.contributor.affiliationUniversity of Sheffielden_UK
dc.contributor.affiliationUniversity of Liverpoolen_UK
dc.contributor.affiliationDurham Universityen_UK
dc.contributor.affiliationUniversity of Liverpoolen_UK
dc.contributor.affiliationBangor Universityen_UK
dc.contributor.affiliationNERC Radiocarbon Laboratoryen_UK
dc.contributor.affiliationBritish Geological Surveyen_UK
dc.contributor.affiliationNewcastle Universityen_UK
dc.contributor.affiliationAberystwyth Universityen_UK
dc.contributor.affiliationUniversity of Sheffielden_UK
dc.contributor.affiliationUniversity of Sheffielden_UK
dc.contributor.affiliationUniversity of Liverpoolen_UK
dc.contributor.affiliationBiological and Environmental Sciencesen_UK
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