British Irish Ice Sheet Research Articles

Behavioural tendencies of the last British–Irish Ice Sheet revealed by data–model comparison

ABSTRACTIntegrating ice‐sheet models with empirical data pertaining to palaeo‐ice sheets promotes advances in the models used in sea‐level predictions and can improve our understanding of past ice‐sheet behaviour. The large number of empirical constraints on the last British–Irish Ice Sheet make it ideal for model–data comparison experiments. Here, we present an ensemble of 600 model simulations, which are compared with data on former ice‐flow extent, flow geometry and deglaciation timing. Simulations which poorly recreate data were ruled out, allowing us to examine the remaining physically realistic simulations which capture the ice sheets' behavioural tendencies. Our results led to a novel reconstruction of behaviour in the data‐poor region of the North Sea, insights into the ice stream, potential ice‐shelf and readvance dynamics, and the potential locations of peripheral ice caps. We also propose that the asynchronous behaviour of the British–Irish Ice Sheet is a consequence of the geography of the British Isles and the merging and splitting of different bodies of ice through saddle merger and collapse. Furthermore, persistent model–data mismatches highlight the need for model development, especially regarding the physics of ice–ocean interactions. Thus, this work highlights the power of integrating models and data, a long‐held aim of palaeoglaciology.

The late Quaternary glacial depositional environment at Filey Bay, eastern England: Accretionary mechanisms for thick sequences of tills and stratified diamictons

Construction of the Holderness/Flamborough Head moraine belt on the East Yorkshire coast, England, records the oscillatory onshore flow of the North Sea Lobe of the British-Irish Ice Sheet from ~25.8 to ~19.7 ka BP, during which time a thick sequence of multiple diamictons and associated stratified sediments were emplaced. The sedimentology of a >40 m thick stratigraphy through the moraine belt at Filey Bay, in combination with local borehole records, is used here to reconstruct the depositional processes associated with glacier ice moving ca., 12 km onshore and damming the mouth of the Vale of Pickering, which resulted in the accumulation of an unusually thick and complex sequence of deposits traditionally classified as the “Filey till”. The base of the sedimentary sequence comprises stratified diamictons, which are interpreted as glacilacustrine deposits emplaced predominantly by sediment gravity flows in an ice-contact ‘mud apron’ on the distal slope of a subaqueous push ridge constructed in the earliest proglacial lake in Filey Bay; a vertical increase in coarse-grained lithofacies records increasing glacier proximity. Glacier overriding of the mud apron is recorded by a stacked sequence of tills that interdigitate with lake sediments inland. A zone of till-lake sediment interdigitation migrated first westward during North Sea Lobe advance and then eastward during its retreat, into and out of Glacial Lake Pickering, respectively. Multiple tills and intra-till stratified beds and lenses at the top of the sequence at Filey represent alternating deforming bed-sliding bed facies (subglacial traction tills and subglacial canal fills) associated with the construction of inset push moraines, constructed by sub-marginal incremental thickening or punctuated aggradation. This depositional scenario addresses the problems arising from genetic classifications of substantial accumulations of glacigenic diamictons as ‘till’ when modern analogues indicate only modest thicknesses of subglacial traction till beneath glaciers. Onshore thickening of glacigenic deposits through subaqueous push moraine construction and mud apron progradation is compatible with glacier surging behaviour, but not necessarily solely diagnostic of a surging North Sea Lobe during the last glaciation.

The timing and magnitude of the British–Irish Ice Sheet between Marine Isotope Stages 5d and 2: implications for glacio‐isostatic adjustment, high relative sea levels and ‘giant erratic’ emplacement

ABSTRACTThe extent, chronology and dynamics of the pre‐Marine Isotope Stage (MIS) 2 last British–Irish Ice Sheet (BIIS) are not well known. Although the BRITICE‐CHRONO Project has detailed the maximum extent and retreat phases of the last BIIS for the period after 30 ka and into the Last Glacial Maximum (LGM), the Project identified several pre‐existing datasets and generated new data that implied glaciation pre‐dating the LGM but which post‐dated the Last Interglacial (Eemian; MIS5e); these data are reviewed here. There are no dated till units but are other indicators clearly indicative of glaciation: deep‐sea ice‐rafted detritus flux into the adjacent NE Atlantic, cosmogenic rock‐exposure age dating from glaciated surfaces in Wales and the island of Lundy (Bristol Channel), and optically stimulated luminescence (OSL) ages of proximal glacifluvial sequences on the Isle of Lewis (Outer Hebrides) and in the Cheshire Basin. Taken together these indicate BIIS inception during MIS5d, growth into MIS4 and evidence for dynamic retreat–advance phases during MIS3. OSL evidence for high relative sea level indicated by raised beaches in southern Ireland during MIS4 and 3 at a time of lowered glacio‐eustatic sea level indicates substantial glacial isostatic loading, explained by the early growth of the BIIS during the last cold stage. High relative sea level during MIS4 and 3 coincident with adjacent calving ice sheet margins provides an explanation for the rafted giant erratics found around the shores of southern Britain and Ireland.

The kinematic significance of subglacial bedforms and their use in palaeo-glaciological reconstructions

Subglacial bedforms are relevant geomorphic markers for palaeo-glaciological reconstructions. Due to the complexity of thermomechanical interactions between ice, till and water on subglacial beds, their formation processes and significance in palaeo-glaciology are still controversial. Based on the measurement and comparison of morphometric characteristics (length, width, amplitude, area and volume) of ∼250 000 bedforms formed below terrestrial ice sheets during the last glacial period, we propose a unified kinematic model, consistent with the ‘bed deformation model’, whereby bedform shapes and orientations depend on their degree of evolution and reflect the magnitude and orientation of finite bed deformation in response to motion of the overlying ice. Two application examples from the Low Land Ice Dome (British-Irish Ice Sheet) and Keewatin Ice Dome (Laurentide Ice Sheet) demonstrate how this model enables the derivation of palaeo-glaciological maps of finite bed deformation, which can then be used to better constrain ice flow directions, their relative velocities, and the location of subglacial drainage routes.

British–Irish Ice Sheet and polar front history of the Goban Spur, offshore southwest Ireland over the last 250 000 years

Deep Sea Drilling Program (DSDP) Site 548 was cored in 1984 at a water depth of 1256 m on the Goban Spur, offshore southwest Ireland. Coring retrieved a ~100‐m‐thick Pleistocene contourite sequence. This study uses planktonic foraminiferal assemblage and benthic foraminiferal oxygen isotope analyses to establish an age model for the upper 40 m of this core. This site's multidisciplinary analyses of planktonic foraminiferal assemblages, lithic grains, facies and calcium carbonate concentration reveal a 250 000‐year record of the North Atlantic polar front variability and British–Irish Ice Sheet (BIIS) history. The sequence is characterized by alternations of ice rafted debris (IRD) laden pelagic mud facies with calcium carbonate‐rich silty sand contourite facies that track glacial/interglacial cycles. The polar front migrated southward across the area several times during glacial maxima and stadial periods, while warmer Mediterranean Outflow Water (MOW) flowed northward across the region during interglacial and interstadial periods depositing contourites. Lithic analyses reveal a complex history of IRD deposition associated with iceberg calving from the Laurentide Ice Sheet and northwest European ice sheets, mainly the BIIS. Comparison between the Goban Spur (DSDP Site 548) and the Celtic Margin (MD03‐2692) and central North Atlantic Integrated Ocean Drilling Program (IODP) Site U1308 suggests differences between the ‘non‐Laurentide Ice Sheet’ Heinrich Events (HE) 6 and 3 at the Goban Spur, with IRD from the BIIS being prominent during HE 6 and IRD from other European ice sheets north of the BIIS likely being more dominant during HE 3. The nature of lithics in IRD‐rich horizons during Terminations 3, 3A, 2 and 1 suggests significant iceberg calving episodes preceding BIIS retreat during the onset of interstadial intervals.

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

The late-Quaternary relative sea-level (RSL) history of Ireland is complex, positioned at the margins of the former British-Irish Ice Sheet, and subject to the influence of ice unloading and forebulge collapse. Geophysical models of post-glacial isostatic adjustment (GIA) provide estimates of the pattern of RSL change since deglaciation which may be tested and validated with empirical data from proxy records. For the region of northwest Ireland, there is a paucity of high-quality RSL data and, therefore, equivocal evidence to support the GIA models that predict a mid to Late-Holocene RSL highstand of between +0.5 and +2 m above present. This study aims to investigate this model-data discrepancy by reconstructing RSL change from a near continuous salt-marsh sequence at Bracky Bridge, Donegal, spanning the last ca. 2500 years. We develop a transfer function model to reconstruct the vertical position of sea level using a regional diatom training set to quantify the indicative meaning and predict the palaeomarsh elevation of the core samples. A chronology is provided by a combination of 14C and 210Pb data, with sample specific ages derived from an age-depth model using a Bayesian framework. Our reconstruction shows ca. 2 m of relative sea-level rise in the past 2500 years. This is not compatible with some previously published sea-level index points from the region, which we re-interpret as freshwater/terrestrial limiting data. These results do not provide any evidence to support a Mid-Holocene RSL highstand above present sea level. Whilst none of the available GIA models replicate the timing and magnitude of the Late-Holocene RSL rise in our reconstruction, those which incorporate a thick and extensive British-Irish Sea Ice Sheet provide the best fit.

Reconstruction of the palaeo‐sea level of Britain and Ireland arising from empirical constraints of ice extent: implications for regional sea level forecasts and North American ice sheet volume

ABSTRACTReconstructions of palaeo‐sea level are vital for predicting future sea level change and constraining palaeo‐ice sheet reconstructions, as well as being useful for a wide array of applications across Quaternary Science. Previous reconstructions of the palaeo‐sea level of Britain and Ireland relied on a circular tuning of glacio‐isostatic models: input ice sheet thicknesses and extents were iteratively altered to fit relative sea level data. Here we break that circularity by utilizing new data from the BRITICE‐CHRONO project, which constrains the position of the British–Irish ice sheet margin through time, and we compare derived glacio‐isostatic modelling to the rich relative sea level record. We test a combination of plausible ice thickness scenarios which account for the uncertainty of ice margin position over the North Sea, demonstrating the region where regional sea level data could distinguish between different glaciation scenarios. Our optimal reconstruction is then combined with several global‐scale reconstructions. As the signal of the British–Irish Ice Sheet is constrained, we demonstrate how the relative sea level record of Britain and Ireland can be used to test reconstructions of far‐field ice sheets (e.g. Antarctica, Eurasia and the Laurentide). The derived palaeo‐topography data are likely to be useful for multiple disciplines. Finally, our improved method of sea level reconstruction impacts predictions of contemporary vertical land motion.

Stratigraphic and palaeo-geomorphological evidence for the glacial-deglacial history of the last British-Irish Ice Sheet in the north-western Irish Sea

During its maximum extent around 25–23 ka BP, the British-Irish Ice Sheet extended to near the present-day shelf break with a large ice stream, the Irish Sea Ice Stream, occupied much of the present-day Celtic and Irish Seas. The different episodes of advance and retreat of the ice sheet have been extensively constrained onshore, with models based on feature characterisation and dating helping to understand the retreat pattern of the ice sheet. Offshore, glacial geomorphologies in the Irish Sea have been mostly recognised on the United Kingdom side but remains poorly constrained on the Irish side. In this paper, based on the analysis of an extensive seismic dataset, an update of the stratigraphic model of the northern Irish Sea, with new sub-units, is proposed with a mapping of newly discovered buried geomorphology. Characterisation of the geomorphology, including megascale glacial lineations, subglacial meltwater channels, moraines, and iceberg scours, has been used to extend the constraints on ice sheet retreat offshore. The transition from late glacial to marine setting has been constrained based on the mapping of marine sediment subunits and their terminations. This paper brings new constraints offshore, in a previously understudied area, and synthesises all the results into an updated conceptual model highlighting stratigraphic units succession and associated processes linked to geomorphology, within the context of a rapidly retreating ice stream.

Eurasian Ice Sheet derived meltwater pulses and their role in driving atmospheric dust activity: Late Quaternary loess sources in SE England

The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25–23.5 ka and 20–19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon U–Pb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.

Linking North Atlantic and Alpine Last Glacial Maximum climates via a high-resolution pollen-based subarctic forest steppe record

During the last glaciation the Eurasian continent was impacted by the global reorganization of atmospheric circulation caused by North Atlantic events, through changes in moisture storm tracks modulated by orography. Our research explores the linkages between climate evolution in the North Atlantic and in the Alps between 30.6 and 12.5 ka, This period, centered on the Last Glacial Maximum, experienced the most recent phase of maximum global ice volume, corresponding to a millennia-long phase of sea-level lowstand, minima in reconstructed sea surface temperatures and isotopic values from polar ice. We present a high-resolution multiproxy record from Lake Fimon at the southern Alpine foothills, where a larch forest-steppe persisted throughout the coldest spells. We analyse the fine climate structure of the MIS 3–2 transition, of the Alpine Last Glacial Maximum stepped by HS2, and provide an unprecedented fine resolution and accurate 14C dating of the Last Glacial Maximum and the early Alpine Lateglacial. We reconstructed quantitative climate parameters based on sensitive pollen descriptors, and derived co-registered sedimentary proxies for dust flux. Reconstructed series suggest that extreme continental spells in the Alps and cold boreal winters match the timing of Heinrich Stadials 2 and 1, episodes of iceberg discharge and release of rock fragments (Ice Rafted Debris) in the North Atlantic. The initiation of the LGM at 27.3 ka is marked by a 4 °C drop in July temperatures, likely responsible for the onset of glacial build-up in the Southern Alpine piedmont. The first extreme continental spell coincides with the British-Irish-sourced IRD event at 26.2 ka and with glacier retreat in the Southern Alps, persisting in the subsequent HS2. Late Glacial glacier collapse and extreme drought occurred during the first half of the HS1, 17.4–16.2 ka. The comparison of the results obtained at Lake Fimon with other terrestrial Eurasian records and with recalibrated marine chronologies from the North Atlantic suggests in-phase reactions of the British-Irish Ice Sheet and of Alpine glaciers and ecosystems to changes in the Atlantic Meridional Circulation. Asymmetric ecoclimatic effects produced by North Atlantic events at the windward and leeward sides of the Alps confirm a southern provenance of moist air masses throughout the LGM.

Growth and retreat of the last British–Irish Ice Sheet, 31 000 to 15 000 years ago: the BRITICE‐CHRONO reconstruction

The BRITICE‐CHRONO consortium of researchers undertook a dating programme to constrain the timing of advance, maximum extent and retreat of the British–Irish Ice Sheet between 31 000 and 15 000 years before present. The dating campaign across Ireland and Britain and their continental shelves, and across the North Sea included 1500 days of field investigation yielding 18 000 km of marine geophysical data, 377 cores of sea floor sediments, and geomorphological and stratigraphical information at 121 sites on land; generating 690 new geochronometric ages. These findings are reported in 28 publications including synthesis into eight transect reconstructions. Here we build ice sheet‐wide reconstructions consistent with these findings and using retreat patterns and dates for the inter‐transect areas. Two reconstructions are presented, a wholly empirical version and a version that combines modelling with the new empirical evidence. Palaeoglaciological maps of ice extent, thickness, velocity, and flow geometry at thousand‐year timesteps are presented. The maximum ice volume of 1.8 m sea level equivalent occurred at 23 ka. A larger extent than previously defined is found and widespread advance of ice to the continental shelf break is confirmed during the last glacial. Asynchrony occurred in the timing of maximum extent and onset of retreat, ranging from 30 to 22 ka. The tipping point of deglaciation at 22 ka was triggered by ice stream retreat and saddle collapses. Analysis of retreat rates leads us to accept our hypothesis that the marine‐influenced sectors collapsed rapidly. First order controls on ice‐sheet demise were glacio‐isostatic loading triggering retreat of marine sectors, aided by glaciological instabilities and then climate warming finished off the smaller, terrestrial ice sheet. Overprinted on this signal were second order controls arising from variations in trough topographies and with sector‐scale ice geometric readjustments arising from dispositions in the geography of the landscape. These second order controls produced a stepped deglaciation. The retreat of the British–Irish Ice Sheet is now the world’s most well‐constrained and a valuable data‐rich environment for improving ice‐sheet modelling.

Character of advance and retreat of the southwest sector of the British-Irish Ice Sheet during the last glaciation

Relict landforms and sediments across former glaciated settings provide information about ice-sheet dynamics and can contribute to the understanding of the behaviour of contemporary ice masses, for which observations are limited in spatial and temporal extent. In this study, we focus on the shelf offshore southwest Ireland, in the Celtic Sea, which was once occupied by the Irish Sea Ice Stream (ISIS), the largest ice stream draining the southern portion of the marine-terminating British-Irish Ice Sheet (BIIS). Newly acquired high-resolution multibeam echosounder, sub-bottom and core data enabled the investigation of the shelf geomorphology and of the sedimentology and chronology of glacial and glacimarine sediments. A suite of drumlins records ice sheet flow from the coastline towards the central part of the shelf in southwest Ireland. Pre-existing highs in the seafloor topography promoted the formation of arcuate and transverse landforms interpreted as a grounding-zone wedge and moraines and they document episodic retreat of the ISIS across this portion of the shelf. Observed lithofacies show consolidated subglacial till and laminated fine muds. The sediments provide evidence of ice grounded ca. 30 km off the south-west Irish coastline with subsequent deglaciation occurring under glacimarine conditions. These new data refine the current reconstructions of the dynamics of the southern BIIS. They reveal for the first time the interplay of marine- and land-based ice and the presence of grounded ice offshore SW Ireland. This study highlights the importance of high-resolution data in revealing palaeo-landscapes as valuable analogues to test possible scenarios of modern ice sheet changes.

Conserving Quaternary geoheritage in Northern Ireland

Northern Ireland has a rich and varied Quaternary geoheritage. Landforms and sediments from the last glacial phase of the Late Pleistocene are most prevalent, though the record extends from the last interglacial (MIS 5e) to the Holocene. The glacial record in the region continues to play a crucial role in the development of models of the last British-Irish Ice Sheet, with many sites having international significance. It is the role of the Northern Ireland Environment Agency to legally protect and conserve this important Quaternary heritage, and a programme of statutory designation of these sites as Areas of Special Scientific Interest (ASSIs) has been in place for over twenty years. ASSIs are selected from the Pleistocene and Holocene themes of the Earth Science Conservation Review, the process through which geological sites in Northern Ireland are assessed to determine their importance to science, and so to geoconservation. This produced a significant series of reports that have contributed much to the grey and white literature for the Quaternary in the United Kingdom and Ireland. Quaternary geoheritage is recognised in the local planning system and existing and potential UNESCO Global Geoparks further serve to promote and protect this aspect of Northern Ireland's natural heritage. This paper summarises the Quaternary history of Northern Ireland, how ASSIs are selected to reflect this and how they are monitored and managed. It also considers how to ensure continued protection and recognition for Quaternary sites and features in the region.

The role of ocean and atmospheric dynamics in the marine-based collapse of the last Eurasian Ice Sheet

Information from former ice sheets may provide important context for understanding the response of today’s ice sheets to forcing mechanisms. Here we present a reconstruction of the last deglaciation of marine sectors of the Eurasian Ice Sheet, emphasising how the retreat of the Norwegian Channel and the Barents Sea ice streams led to separation of the British-Irish and Fennoscandian ice sheets at c. 18.700 and of the Kara-Barents Sea-Svalbard and Fennoscandian ice sheets between 16.000 and 15.000 years ago. Combined with ice sheet modelling and palaeoceanographic data, our reconstruction shows that the deglaciation, from a peak volume of 20 m of sea-level rise equivalent, was mainly driven by temperature forced surface mass balance in the south, and by Nordic Seas oceanic conditions in the north. Our results highlight the nonlinearity in the response of an ice sheet to forcing and the significance of ocean-ice-atmosphere dynamics in assessing the fate of contemporary ice sheets.

10Be and 26Al exposure history of the highest mountains in Wales: Evidence from Yr Wyddfa (Snowdon) and Y Glyderau for a nunatak landscape at the global Last Glacial Maximum

Twelve 10Be and five 26Al samples from the mountains of Yr Wyddfa (Snowdon) (1085 m) (n = 7 10Be) and Y Glyderau (the Glyders) (1001 m) (n = 5 paired 10Be/26Al) in Wales provide new insights into landscape evolution in the highest mountains in the British Isles outside of Scotland. The summits of Y Glyderau are characterised by intensely modified frost-shattered surfaces and have long been recognised as exemplars of mountain summit periglacial activity in the British Isles. However, glacially transported boulders on the highest ground indicate that ice overran the summits. Bedrock and boulder surfaces at altitudes >900 m yield 10Be and 26Al exposure ages of 61–78 ka, indicating that the last Welsh Ice Cap did not override and erode Y Glyderau summits at the global Last Glacial Maximum (LGM) and the summits stood as nunataks. Both the geomorphological and the exposure dating evidence indicate ice overran the summits earlier in the last glacial cycle during MIS 4, although erosion was only partial. Thick ice over Wales at this time is consistent with evidence of an extensive British-Irish Ice Sheet that reached the continental shelf to the west in MIS 4. The ice-scoured lower slopes of Y Glyderau and the arêtes of Yr Wyddfa were exposed as the ice cap rapidly thinned between 20-16 ka marking a transition from ice cap to alpine-style glaciation. On Yr Wyddfa, the highest mountain in southern Britain, local ice breached and abraded the central parts of the Crib Goch-Crib y Ddysgl arête as high as 874 m until c. 16 ka. However, some arête crests yielded Holocene ages (4.4–9.3 ka), which reflect continual post-glacial stripping.

Using novel methods to track British and Irish Ice Sheet dynamics since the Late Pleistocene, along the west Porcupine Bank, NE Atlantic

Extensive research has been undertaken to elucidate the glacial history of the British Irish Ice Sheet (BIIS) in the NE Atlantic. BRITICE-CHRONO has compiled terrestrial and marine based evidence, to provide an empirical reconstruction of ice sheet expansion and retreat during the Late Pleistocene. Across the Irish margin, particular focus has been given to seafloor sediments which contain ice-rafted debris (IRD). However, there are few publications on IRD from areas proximal to the maximum extent of the BIIS, which would offer further insights on the behaviour of the ice sheet during (de)glacial events. Previous exploratory surveys of the west Porcupine Bank (wPB) visually identified IRD on the seafloor and these present a new study site to investigate the extent of the BIIS and the course of its icebergs. Moreover, there are uncertainties about the effects of icebergs on the marine life and cold-water corals occupying the nearby Porcupine Bank Canyon. Assessing a sediment core containing an IRD analogue for the wPB would thus, have a dual purpose. In the past however, coring missions of the wPB using traditional coring methods (i.e. piston and gravity cores) were unsuccessful. Here, we utilized a novel ROV-mounted vibrocoring procedure to capture a 0.75 m IRD-bearing sediment core from the wPB. Then further novel analytical methods (computed tomography-based IRD-detection) were used to quantify IRD every 0.02 cm to provide the highest resolution record of BIIS related IRD to date. From this, several fluxes of IRD deposition onto the wPB between 31.6 and 9 ka BP were revealed and corroborated by other published records from across the NE Atlantic. It was shown that the wPB IRD fluxes occur simultaneously with other parts of the margin. The IRD signal also shows that iceberg calving occurred on the wPB during the Younger Dryas. Grain-size analysis of the core allowed for a reconstruction and interpretation of the palaeoenvironmental conditions during these IRD flux events and shows that BIIS-derived glaciers had a major impact on hydrodynamic conditions in the wPB. Subsequently, intensive scouring led to a major hiatus in the core during 27.3–17.2 ka BP. These results are a useful addition to BIIS literature on this part of the shelf. Furthermore, it shows that bottom currents were influenced by (de)glacial events, an important finding when considering the presence of nearby current-dependant benthos.

New geomorphic evidence for a multi‐stage proglacial lake associated with the former British–Irish Ice Sheet in the Vale of Pickering, Yorkshire, UK

ABSTRACTFormer proglacial lakes provide insight into the temporal and spatial evolution of past ice sheet dynamics and the glaciohydrological systems associated with them. Glacial Lake Pickering was a proglacial lake in North Yorkshire impounded by the British–Irish Ice Sheet. However, geomorphic evidence for its existence and extent is weak and contested. This paper presents, for the first time, systematic mapping of geomorphic features from high‐resolution (50 cm to 5 m) digital terrain model data and undertakes palaeogeographical reconstructions to establish Palaeolake Pickering's extent and levels. Results show only weak evidence for a 70‐m lake. This and the fact that the present landscape configuration is unable to impound such a large lake suggests that it either did not exist or is much older and that considerable landscape erosion has since taken place. There is good geomorphological evidence to support lake levels between 45 and 20 m. The new palaeogeographical reconstructions show these lake levels were initially controlled by the balance between the North Sea and the Vale of York Lobes of the British–Irish Ice Sheet with lower and later levels impounded by the Filey moraine. A multi‐stage Palaeolake Pickering with various extents and levels possibly spanning more than one glacial period has implications for other British–Irish Ice Sheet palaeolake extents reconstructed only from undifferentiated lacustrine sediments and their maximal elevation. The existence of an extensive multi‐phase proglacial Palaeolake Pickering along with other similar ones in Eastern England would have impacted mass loss and frontal dynamics via subaqueous melting and iceberg calving, potentially playing a role in controlling the dynamic behaviour of the North Sea Lobe.

Transit boosting of trans-Channel katabatic winds by depressions associated with the west European storms tracks: impact on Pleistocene loess deposits

Onshore and offshore sedimentological, geochemical, geomorphological, palaeontological and geochronological studies of loess deposits located under and around the English Channel revealed that they were transported by katabatic winds generated by the British–Irish Ice Sheet. Katabatic winds, which are low-altitude wind flows, were able to jump over the low southern British hills but were stopped by the higher Brittany and Normandy hills. This regional topography is interrupted by a north–south corridor linking the northern and southern shores of Brittany where loess propagated down to the mouth of the Loire River. This long transit shows that the total distance travelled by the katabatic wind was around 750 km, which represents an unusual distance for the propagation of this wind under continental conditions. Strong similarities with Antarctica and Greenland, where well documented cases of katabatic winds are known, show that the transit of the trans-Channel katabatic winds were strongly enhanced by the seasonal drift of storms propagating in an eastward direction along the axis of the English Channel. This increasing strength of the north–south katabatic flux was probably at the origin of the transport of loess particles down to the mouth of the Loire River.

Combined control of bottom and turbidity currents on the origin and evolution of channel systems, examples from the Porcupine Seabight

The Gollum Channel System (GCS) and Kings Channel System (KCS) are situated at a key location on the eastern side of the Porcupine Seabight to provide valuable insight into British-Irish Ice Sheet dynamics and sediment supply to the Belgica cold-water coral mound province. These channel systems are the most efficient pathways for particles from the Irish Shelf edge to the Porcupine basin. The spatial and temporal variability of their activity are, therefore, likely to have significant regional consequences. However, the sedimentary processes involved in the evolution of both systems have not yet been comprehensively studied. Here, bathymetric, 2D seismic reflection and oceanographic data are used to reconstruct and compare the interplay between along-, across- and downslope processes through geomorphologic and seismic stratigraphic analyses. The initial seafloor topography of the systems was shaped in the late Miocene-late Pliocene by intense northward-flowing bottom currents during the first phases of the composite RD1 erosion event. The bases of the KCS and GCS were eroded by downslope-flowing turbidity currents during the last phase of the RD1 event. Sediment transport within the channels was probably most active during Quaternary glacial periods of lowered sea levels, and sediment carried downslope by turbidity currents was likely pirated and transported northwards by contour currents. Therefore, the channels are proposed to have been of major importance as a source of sediment and nutrients for the Belgica cold-water coral mounds and associated sediment drifts to the north. The GCS and KCS represent an area where bottom currents, turbidity currents, slope failures and hemipelagic processes have interacted throughout the Neogene and Quaternary.

Impact of katabatic winds on the environment of Neanderthals during the Middle Palaeolithic in westernmost Europe

ABSTRACTCompilation of the offshore and onshore altitudinal limits of the loess deposits of western France and southern England shows that they were deposited by low‐level wind fields. These relate to (i) the deflation of silt‐rich sediment extracted from the outwash plains of the not far distant British–Irish Ice Sheet and from the palaeo‐rivers of the Channel, and (ii) the existence of north and north‐western palaeo‐winds deduced from particle size analysis and heavy mineral distribution, and suggest (iii) that loess particles were transported by strong katabatic winds blowing from the northern ice‐covered regions towards Brittany and Normandy. Comparison between the main orientation of Neanderthal shelters and the direction of the katabatic winds shows that they were perpendicular to each other. The dominant orientation of the shelters was apparently ruled by these winds. A small‐scale study concentrating on the penultimate glaciation shows that in contrast to Brittany and Normandy where loess deposits accumulated on north‐facing cliffs, in England the same particles were deposited on the leeside of the hills. The existence of deflation zones, violently swept by Marine Isotope Stage 6 katabatic winds south of the British–Irish ice sheet, was probably at the origin of the restricted number of Neanderthals at that time in England. © 2021 John Wiley & Sons, Ltd.