Extent and retreat history of the Barra Fan Ice Stream offshore western Scotland and northern Ireland during the last glaciation

During the Last Glacial Maximum (LGM) the marine-terminating Barra Fan Ice Stream (BFIS), a major conduit of the British Irish Ice Sheet (BIIS), drained much of western Scotland and northwest Ireland with ice streaming onto the continental shelf of the Malin Sea. The extent and retreat history of this ice stream across the shelf, until now, is not well known. In particular, geochronological constraints on the history of this ice stream have thus far been restricted to deep-sea cores or terrestrial cosmogenic nuclide dating onshore, with ages across the shelf absent. To understand the possible external forcing factors acting on this marine terminating ice stream during retreat, improved geochronological constraint on its deglaciation is necessary. Here, we present new geophysical data, marine sediment cores and over forty radiocarbon dates to provide important constraints on maximum extent of the BFIS, as well as the timing and pattern of retreat back across the Malin Shelf. Dated moraines and grounding-zone wedges (GZW) seen in seafloor sub-bottom profiles provide evidence that the BFIS reached the Malin Shelf edge during the LGM and was at its maximum extent around 26.7 ka BP. The presence of two sets of GZWs suggests that the style of retreat was episodic. The new radiocarbon chronology shows that retreat from the shelf edge was underway by 25.9 ka BP, with the majority of the continental shelf ice free by 23.2 ka BP, and that glacimarine conditions were present in the Sea of Hebrides by 20.2 ka BP at the latest. Collectively, these results indicate that the majority of the Malin Shelf was free of grounded ice by ∼21.5–20 ka BP, which is up to 4000 years earlier than previously reconstructed. We attribute this early deglaciation to high relative sea level caused by glacial isostatic depression when the BIIS reached its maximum extent promoting ice shelf and grounding line instability. Two deep troughs, forming reverse bed slopes, aided the continued retreat of the BFIS. This suggests that local ice loading and bed morphology can be significant controls on the destabilisation of a marine-terminating ice stream and can override the influence of ocean and atmospheric temperatures

Post-acute COVID-19 neuropsychiatric symptoms are not associated with ongoing nervous system injury

A proportion of patients infected with severe acute respiratory syndrome coronavirus 2 experience a range of neuropsychiatric symptoms months after infection, including cognitive deficits, depression and anxiety. The mechanisms underpinning such symptoms remain elusive. Recent research has demonstrated that nervous system injury can occur during COVID-19. Whether ongoing neural injury in the months after COVID-19 accounts for the ongoing or emergent neuropsychiatric symptoms is unclear. Within a large prospective cohort study of adult survivors who were hospitalized for severe acute respiratory syndrome coronavirus 2 infection, we analysed plasma markers of nervous system injury and astrocytic activation, measured 6 months post-infection: neurofilament light, glial fibrillary acidic protein and total tau protein. We assessed whether these markers were associated with the severity of the acute COVID-19 illness and with post-acute neuropsychiatric symptoms (as measured by the Patient Health Questionnaire for depression, the General Anxiety Disorder assessment for anxiety, the Montreal Cognitive Assessment for objective cognitive deficit and the cognitive items of the Patient Symptom Questionnaire for subjective cognitive deficit) at 6 months and 1 year post-hospital discharge from COVID-19. No robust associations were found between markers of nervous system injury and severity of acute COVID-19 (except for an association of small effect size between duration of admission and neurofilament light) nor with post-acute neuropsychiatric symptoms. These results suggest that ongoing neuropsychiatric symptoms are not due to ongoing neural injury

Long COVID and cardiovascular disease: a prospective cohort study

Background Pre-existing cardiovascular disease (CVD) or cardiovascular risk factors have been associated with an increased risk of complications following hospitalisation with COVID-19, but their impact on the rate of recovery following discharge is not known. Objectives To determine whether the rate of patient-perceived recovery following hospitalisation with COVID-19 was affected by the presence of CVD or cardiovascular risk factors. Methods In a multicentre prospective cohort study, patients were recruited following discharge from the hospital with COVID-19 undertaking two comprehensive assessments at 5 months and 12 months. Patients were stratified by the presence of either CVD or cardiovascular risk factors prior to hospitalisation with COVID-19 and compared with controls with neither. Full recovery was determined by the response to a patient-perceived evaluation of full recovery from COVID-19 in the context of physical, physiological and cognitive determinants of health. Results From a total population of 2545 patients (38.8% women), 472 (18.5%) and 1355 (53.2%) had CVD or cardiovascular risk factors, respectively. Compared with controls (n=718), patients with CVD and cardiovascular risk factors were older and more likely to have had severe COVID-19. Full recovery was significantly lower at 12 months in patients with CVD (adjusted OR (aOR) 0.62, 95% CI 0.43 to 0.89) and cardiovascular risk factors (aOR 0.66, 95% CI 0.50 to 0.86). Conclusion Patients with CVD or cardiovascular risk factors had a delayed recovery at 12 months following hospitalisation with COVID-19. Targeted interventions to reduce the impact of COVID-19 in patients with cardiovascular disease remain an unmet need

European impacts on coastal eastern Tasmania: Insights from a high-resolution palynological analysis of a salt-marsh core

A high-resolution pollen and micro-charcoal (>5 μm) record has been produced from a short sediment (50 cm) core recovered from a salt marsh in the Little Swanport Estuary, eastern Tasmania. This record suggests that there are four phases associated with the European settlement of the region. An initial phase from around 1830 to 1858 AD, which is similar to the previous Aboriginal period; a relatively low impact transitional phase from 1859 to 1898 AD; a rapid and marked deforestation period from 1899 to 1932 AD; and establishment of the contemporary landscape, with reforestation occurring, but with marked differences in species composition (i.e., greater representation of exotic taxa and altered understorey composition) from 1933 to 2006 AD. Key similarities are seen across Australia with the European settlement phase (i.e., addition of exotic taxa, deforestation and/or changes in vegetation composition, alterations in fire regimes and increased sedimentation rates), but high-resolution analysis suggests that these impacts may manifest in different ways depending on the local environmental setting and/or historical context of the settlement location. Furthermore, Amaranthaceae pollen representation appears to be impacted by changes in sea level. However, other factors such as human modifications, particularly grazing, and climate variability may play additional roles and further research is required to disentangle the relative effects of these factors

Phased occupation and retreat of the last British-Irish Ice Sheet in the southern North Sea: geomorphic and seismostratigraphic evidence of a dynamic ice lobe

Along the terrestrial margin of the southern North Sea, previous studies of the MIS 2 glaciation impacting eastern Britain have played a significant role in the development of principles relating to ice sheet dynamics (e.g. deformable beds), and the practice of reconstructing the style, timing, and spatial configuration of palaeo-ice sheets. These detailed terrestrially-based findings have however relied on observations made from only the outer edges of the former ice mass, as the North Sea Lobe (NSL) of the British-Irish Ice Sheet (BIIS) occupied an area that is now almost entirely submarine (c.21–15 ka). Compounded by the fact that marine-acquired data have been primarily of insufficient quality and density, the configuration and behaviour of the last BIIS in the southern North Sea remains surprisingly poorly constrained. This paper presents analysis of a new, integrated set of extensive seabed geomorphological and seismo-stratigraphic observations that both advances the principles developed previously onshore (e.g. multiple advance and retreat cycles), and provides a more detailed and accurate reconstruction of the BIIS at its southern-most extent in the North Sea. A new bathymetry compilation of the region reveals a series of broad sedimentary wedges and associated moraines that represent several terminal positions of the NSL. These former still-stand ice margins (1–4) are also found to relate to newly-identified architectural patterns (shallow stacked sedimentary wedges) in the region's seismic stratigraphy (previously mapped singularly as the Bolders Bank Formation). With ground-truthing constraint provided by sediment cores, these wedges are interpreted as sub-marginal till wedges, formed by complex subglacial accretionary processes that resulted in till thickening towards the former ice-sheet margins. The newly sub-divided shallow seismic stratigraphy (at least five units) also provides an indication of the relative event chronology of the NSL. While there is a general record of south-to-north retreat, seismic data also indicate episodes of ice-sheet re-advance suggestive of an oscillating margin (e.g. MIS 2 maximum not related to first incursion of ice into region). Demonstrating further landform interdependence, geographically-grouped sets of tunnel valleys are shown to be genetically related to these individual ice margins, providing clear insight into how meltwater drainage was organised at the evolving termini of this dynamic ice lobe. The newly reconstructed offshore ice margins are found to be well correlated with previously observed terrestrial limits in Lincolnshire and E. Yorkshire (Holderness) (e.g. MIS 2 maximum and Withernsea Till). This reconstruction will hopefully provide a useful framework for studies targeting the climatic, mass-balance, and external glaciological factors (i.e. Fennoscandian Ice Sheet) that influenced late-stage advance and deglaciation, important for accurately characterising both modern and palaeo-ice sheets

Late Quaternary evolution and sea-level history of a glaciated marine embayment, Bantry Bay, SW Ireland

Ireland experienced a spatially complex pattern of relative sea-level (RSL) changes and shoreline development caused by the interplay of isostatic and eustatic (ice equivalent sea level) processes since the Last Glacial Maximum (LGM). Using a combination of high-resolution marine geophysical data, vibrocores, foraminiferal analysis and 10 AMS radiocarbon dates, we reconstruct the Late Quaternary evolution and RSL history of Bantry Bay, a large (40 km long, 5–10 km wide) embayment in SW Ireland. The data indicate two infill phases: one before and one after the LGM, separated by glacial and lowstand sediments. The pre-LGM history is not dated and the depositional history is inferred. A large sediment lobe formed at the outer edge of Bantry Bay as a lowstand ice-proximal glacimarine outwash system as the ice retreated after the LGM, at a sea level ca. 80 m lower than present. Iceberg scour immediately west of this location likely relate to the break-up of the local Kerry–Cork Ice Cap. Long curvilinear ridges, seen both offshore and on top of the sediment lobe, probably formed as shoreface ridges under stronger-than-present tidal currents during a period of RSL stability (pre-14.6 ka cal BP). A subsequent infill phase is characterised by a basin-wide erosional (ravinement) surface and the deposition of inter- and sub-tidal estuarine sediments. Although our data support the general trends, our stratigraphic and radiocarbon data suggest a higher sea level between 11 and 13.5 ka cal BP than predicted by existing glacial isostatic adjustment models

The deglaciation of the western sector of the Irish Ice Sheet from the inner continental shelf to its terrestrial margin

This paper provides a new deglacial chronology for retreat of the Irish Ice Sheet from the continental shelf of western Ireland to the adjoining coastline, a region where the timing and drivers of ice recession have never been fully constrained. Previous work suggests maximum ice‐sheet extent on the outer western continental shelf occurred at ~26–24 cal. ka BP with the initial retreat of the ice marked by the production of grounding‐zone wedges between 23–21.1 cal. ka BP . However, the timing and rate of ice‐sheet retreat from the inner continental shelf to the present coast are largely unknown. This paper reports 31 new terrestrial cosmogenic nuclide (TCN ) ages from erratics and ice‐moulded bedrock and three new optically stimulated luminescence (OSL ) ages on deglacial outwash. The TCN data constrain deglaciation of the near coast (Aran Islands) to ~19.5–18.5 ka. This infers ice retreated rapidly from the mid‐shelf after 21 ka, but the combined effects of bathymetric shallowing and pinning acted to stabilize the ice at the Aran Islands. However, marginal stability was short‐lived, with multiple coastal sites along the Connemara/Galway coasts demonstrating ice recession under terrestrial conditions by 18.2–17. ka. This pattern of retreat continued as ice retreated eastward through inner Galway Bay by 16.5 ka. South of Galway, the Kilkee–Kilrush Moraine Complex and Scattery Island moraines point to late stage re‐advances of the ice sheet into southern County Clare ~14.1–13.3 ka, but the large errors associated with the OSL ages make correlation with other regional re‐advances difficult. It seems more likely that these moraines are the product of regional ice lobes adjusting to internal ice‐sheet dynamics during deglaciation in the time window 17–16 ka

Final deglaciation of the Malin Sea through meltwater release and calving events

During the last glacial maximum, the British–Irish Ice Sheet (BIIS) extended to the shelf edge in the Malin Sea between Ireland and Scotland, delivering sediments to the Donegal Barra Fan (DBF). Analysis of well-preserved, glacially derived sediment in the DBF provides new insights on the character of the BIIS final deglaciation and palaeoenvironmental conditions at the Younger Dryas. Chaotic/laminated muds, ice-rafted debris (IRD)-rich layers and laminated sand–mud couplets are interpreted as respectively mass transport deposits, plumites and turbidites of BIIS-transported sediments. Peaks in IRD, constrained by radiocarbon dating to after 18 cal ka BP, indicate discrete intervals of iceberg calving during the last stages of deglaciation. Glacially derived sedimentation on the slope occurred until c. 16.9 cal ka BP. This is interpreted as the last time the ice sheet was present on to the shelf, allowing glacial meltwater to reach the fan. Bioturbated and foraminifera-rich muds above glaciomarine sediments are interpreted as interglacial hemipelagites and contourites, with the presence of Zoophycos suggesting restoration of bottom currents at the transition between stadial and interstadial conditions. During the Younger Dryas, Neogloboquadrina pachyderma sinistral abundances and an isolated peak in IRD indicate the temporary restoration of cold conditions and the presence of icebergs in the region

Early deglaciation of the British-Irish Ice Sheet on the Atlantic shelf northwest of Ireland driven by glacioisostatic depression and high relative sea level

Understanding the triggers and pace of marine-based ice sheet decay is critical for constraining the future mass loss and dynamic behaviour of marine-based sectors of the large polar ice sheets in Greenland and Antarctica. Numerical models which seek to predict this behaviour need to be calibrated against data from both contemporary and palaeo-ice sheets, and the latter requires accurate reconstruction of former ice sheet extent, dynamics and timing. Marine geophysics, sediment cores, benthic foraminiferal assemblages and radiocarbon dating are used to reconstruct the extent of the last British-Irish Ice Sheet (BIIS), and the timing and style of its retreat on the Atlantic shelf northwest of Ireland. Shelf edge moraines and subglacial till recovered in cores from the outer continental shelf are dated to younger than 26.3 ka cal BP and indicate an extensive ice sheet at the Last Glacial Maximum (LGM) that was grounded to the shelf edge. Nested arcuate moraines record the subsequent episodic retreat of the ice sheet across the shelf. Lithofacies and associated foraminiferal assemblages demonstrate that this retreat occurred in a glacimarine environment as a grounded tidewater margin and that high relative sea level and cold waters prevailed during retreat. Radiocarbon dates indicate that the timing of initial ice sheet retreat from the shelf edge occurred in the interval between 26.3 and 24.8 ka cal BP, during the period of minimum global eustatic sea level, and that the ice sheet had retreated to the mid-shelf by 24.8 ka cal BP. The ‘Donegal Bay Moraine’, a large moraine at the mouth of Donegal Bay, records a major stillstand and readvance of the ice sheet during deglaciation between 20.2 and 17.9 ka cal BP. Estimated retreat rates of 5.5–35 m a−1 across the shelf demonstrate that retreat was slow. It is noteworthy that retreat was initiated in the absence of ocean warming and when eustatic sea level was at a minimum. The sea-level rise that initiated deglaciation from the shelf edge therefore, is inferred to have been a product of local glacio-isostatic crustal depression rather than external forcing. This demonstrates that marine-based sectors of ice sheets can trigger their own demise internally through glacio-isostatic adjustment and it provides an explanation for the early retreat of the BIIS on the Atlantic shelf during the global LGM (gLGM)

Lack of evidence for a substantial sea-level fluctuation within the Last Interglacial

During the Last Interglacial, global mean sea level reached approximately 6 to 9 m above the present level. This period of high sea level may have been punctuated by a fall of more than 4 m, but a cause for such a widespread sea-level fall has been elusive. Reconstructions of global mean sea level account for solid Earth processes and so the rapid growth and decay of ice sheets is the most obvious explanation for the sea-level fluctuation. Here, we synthesize published geomorphological and stratigraphic indicators from the Last Interglacial, and find no evidence for ice-sheet regrowth within the warm interglacial climate. We also identify uncertainties in the interpretation of local relative sea-level data that underpin the reconstructions of global mean sea level. Given this uncertainty, and taking into account our inability to identify any plausible processes that would cause global sea level to fall by 4 m during warm climate conditions, we question the occurrence of a rapid sea-level fluctuation within the Last Interglacial. We therefore recommend caution in interpreting the high rates of global mean sea-level rise in excess of 3 to 7 m per 1,000 years that have been proposed for the period following the Last Interglacial sea-level lowstand