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Abstract: Well-resolved event-based stratigraphies in marine sediments spanning a significant portion of the last glacial period (60–8 kyr) provide a unique opportunity for time–stratigraphic correlation in the North Atlantic region. Here, we review the current methods available to chronologically constrain these event-based stratigraphies, highlighting, in particular, the value of tephrochronology as an independent tool to validate correlations between records. While the INTIMATE protocols (; Blockley et al., 2011) are equally applicable to marine and terrestrial records, spatially and temporally variable marine radiocarbon reservoir age effects (MREs) provide a challenge to using marine radiocarbon in the former as an independent chronostratigraphic tool. Despite the inherent uncertainties associated with ‘tuning’, we conclude that the mid-points of the common abrupt warming transitions associated with the well-defined, millennial-scale climate oscillations (the Dansgaard–Oeschger (D/O) cycles) observed in the oxygen isotopes of the Greenland ice cores and North Atlantic sea surface temperature (SST) records currently provide the most robust correlation tie-points from which to derive age control. In this invited INTIMATE special issue article we propose a new protocol for establishing marine event-based chronostratigraphies in the North Atlantic region and focus on areas of chronological potential in palaeoceanographic research. [Copyright &y& Elsevier]

The Easington Raised Beach, in Shippersea Bay, County Durham, is the most northerly known interglacial beach deposit in England. It lies directly on Magnesian Limestone bedrock at 33m O.D. and is covered by glacial sediments attributed to the Devensian. Detailed sedimentological analysis suggests that it is an interglacial beach, which is supported by the presence of pebbles bored by marine organisms and littoral, temperate-climate, marine macro- and micro-fossils. It comprises beds of unconsolidated, bedded, imbricated, well-rounded sands and gravels, overlain by similar, but calcreted, deposits. The gravel fraction is dominated by Magnesian and Carboniferous limestone, with orthoquartzite, flint, and porphyries also present; these are far-travelled erratics that must have derived from the erosion of older glacially transported sediments. Previous workers have described erratics derived from the Oslofjord region of Norway in the raised beach gravel, although rocks diagnostic of a Scandinavian origin have not been recovered as part of this study. The heavy-mineral suite is rich in epidote, dolomite, clinopyroxenes, garnet, tourmaline, and micas. The beach was dated previously by conventional amino acid analysis of the shells, which suggested a Marine Isotope Stage (MIS) 7 age, albeit with a reworked component from MIS 9. This has been confirmed by new optically stimulated luminescence (OSL) dates, which indicate that the beach formed between 240 and 200kaBP. New amino acid racemisation analyses, using a modified technique, broadly support this interpretation but must await more comparative data before they can be assessed fully. The strong indication of an MIS 7 age for the formation of the beach has implications for the uplift history of northeastern England during the Pleistocene, and indicates an uplift rate of 0.19mma−1. The stable isotope geochemistry indicates that the cementation occurred during an interglacial period, whilst U-Series dating of the cement indicates that cementation occurred mostly during the Holocene, and is genetically related to the overlying Devensian till. This work has formed part of a full re-appraisal of the glacial sequence in eastern County Durham, the results of which suggest that the Warren House Formation pre-dates the raised beach, and that the Devensian Horden Till overlies the raised beach. [ABSTRACT FROM AUTHOR]

Abstract: Field-collected living specimens of the benthic foraminifera Haynesina germanica were maintained in the laboratory and fed a naturally occurring motile benthic diatom assemblage dominated by Pleurosigma angulatum. The extracellular removal of diatom contents was inferred for P. angulatum in controlled experiments. A characteristic pattern of fracturing of the diatom frustule was observed that was directly attributed to foraminiferal feeding/sequestration mechanisms. These feeding/sequestration mechanisms have a potentially important bearing on our understanding of foraminiferal aperture morphology, foraminiferal evolution and the preservation of diatoms in marine sediments. Recognition of this characteristic breakage pattern of diatom frustules may provide insight into the natural importance of foraminifera in grazing diatom biofilms. [Copyright &y& Elsevier]

High global warming potential (GWP) refrigerant leakage is the second-highest source of carbon emissions across UK supermarket retailers and a major concern for commercial organisations. Recent stringent UN and EU regulations promoting lower GWP refrigerants have been ratified to tackle the high carbon footprint of current refrigerants. This paper introduces a data-driven modelling framework for optimal investment strategies supporting the food retail industry to transition from hydrofluorocarbon (HFC) refrigeration systems to lower GWP systems by 2030, in line with EU legislation. Representative data from a UK food retailer is applied in a mixed integer linear model, making simultaneous investment decisions across the property estate. The model considers refrigeration-system age, capacity, refrigerant type, leakage and past performance relative to peer systems in the rest of the estate. This study proposes two possible actions for high GWP HFC refrigeration systems: a) complying with legislation by retrofitting with an HFO blend (e.g. R449-A) or b) installing a new natural refrigerant system (e.g. R744). Findings indicate that a standard (i.e. business-as-usual) investment level of £6 m/yr drives a retrofitting strategy enabling significant reduction in annual carbon emissions of 71% by the end of 2030 (against the 2018 baseline), along with meeting regulatory compliance. The strategy is also highly effective at reducing emissions in the short term as total emissions during the 12-year programme are 59% lower than would have been experienced if the HFC emissions continued unabated. However, this spending level leaves the business at significant risk of refrigeration system failures as necessary investments in new systems are delayed resulting in an ageing, poorly performing estate. The model is further tested under different budget and policy scenarios and the financial, environmental, and business-risk implications are analysed. For example, under a more aggressive investment approach of £50 m/yr carbon reductions are at 93% by the end of 2030, whilst also ensuring compliance with the legislative cut-off four years early in 2026 and substantially enhancing the reliability of the refrigeration systems in the portfolio. Alternatively, when emissions are minimised instead of cost with a £50 m/yr investment level, 99% decarbonisation is achieved by 2030. Overall, the study highlights the trade-offs between capital investment and system resilience requiring a careful balance of priorities and the need to have up to date information so decision makers can reliably drive a successful strategy towards more sustainable operation of refrigeration systems. Image 1 • Novel optimisation model to reduce F-gas emissions in the food retail industry. • Retrofitting R-449A or R-744 systems considered to comply with regulations. • HFC tax does not significantly curtail emissions as current policy is effective. • Under current investment levels (£6 m/yr) a 71% CO 2e reduction is achieved by 2030. • If investments are frontloaded (£50 m/yr) a 99% reduction is feasible by 2030. [ABSTRACT FROM AUTHOR]

Geochronological constraints on the deglaciation of former marine based ice streams provide information on the rates and modes by which marine based ice sheets have responded to external forcing factors such as climate change. This paper presents new 36 Cl cosmic ray exposure dating from boulders located on two moraines (Glen Brittle and Loch Scavaig) in southern Skye, northwest Scotland. Ages from the Glen Brittle moraines constrain deglaciation of a major marine terminating ice stream, the Barra-Donegal Ice Stream that drained the former British-Irish Ice Sheet, depending on choice of production method and scaling model this occurred 19.9 ± 1.5–17.6 ± 1.3 ka ago. We compare this timing of deglaciation to existing geochronological data and changes in a variety of potential forcing factors constrained through proxy records and numerical models to determine what deglaciation age is most consistent with existing evidence. Another small section of moraine, the Scavaig moraine, is traced offshore through multibeam swath-bathymetry and interpreted as delimiting a later stillstand/readvance stage following ice stream deglaciation. Additional cosmic ray exposure dating from the onshore portion of this moraine indicate that it was deposited 16.3 ± 1.3–15.2 ± 0.9 ka ago. When calculated using the most up-to-date scaling scheme this time of deposition is, within uncertainty, the same as the timing of a widely identified readvance, the Wester Ross Readvance, observed elsewhere in northwest Scotland. This extends the area over which this readvance has potentially occurred, reinforcing the view that it was climatically forced. [ABSTRACT FROM AUTHOR]

Abstract: Tephrochronology is one of the few techniques that offer considerable, but as yet largely unrealised, potential for the correlation of North Atlantic palaeoclimatic archives spanning the MIS 4 and 5a substage period - a phase of pronounced global cooling during the initiation of the last glacial period. In this investigation, two previously unidentified rhyolitic tephra horizons believed to be sourced from Iceland were isolated within the giant piston core MD04-2822, retrieved from the Rockall Trough, North East Atlantic. One horizon was deposited at the beginning of Greenland Stadial 19 (∼70,150 a b2k) and the other around the cooling transition at the end of Greenland Interstadial 20 (∼75,320 a b2k). Density separation, EPMA and LA-ICP-MS techniques were utilised for the identification of these cryptotephra within the fine-fraction sediment (<80 μm diameter) to aid the discovery of primary deposits and to assess the role of mixing processes. An exploration of the geochemical homogeneity, co-variance of shard concentration with IRD and shard size distribution of the two tephra horizons rules out ice-rafting as a potential transport process and instead suggests deposition from primary airfall or via sea-ice rafting of airfall material. The latter processes would not cause a significant delay in deposition following a volcanic eruption due to more rapid transportation to depositional sites. Therefore, these horizons are potentially valuable chronostratigraphic markers for the GI-19 and GI-20 climatic events, two significant events that occurred around the transition between MIS 5a and 4. [Copyright &y& Elsevier]

Genetic characterisation (SSU rRNA genotyping) and Scanning Electron Microscope (SEM) imaging of individual tests were used in tandem to determine the modern species richness of the foraminiferal family Elphidiidae ( Elphidium , Haynesina and related genera) across the Northeast Atlantic shelf biomes. Specimens were collected at 25 locations from the High Arctic to Iberia, and a total of 1013 individual specimens were successfully SEM imaged and genotyped. Phylogenetic analyses were carried out in combination with 28 other elphidiid sequences from GenBank and seventeen distinct elphidiid genetic types were identified within the sample set, seven being sequenced for the first time. Genetic types cluster into seven main clades which largely represent their general morphological character. Differences between genetic types at the genetic, morphological and biogeographic levels are indicative of species level distinction. Their biogeographic distributions, in combination with elphidiid SSU sequences from GenBank and high resolution images from the literature show that each of them exhibits species-specific rather than clade-specific biogeographies. Due to taxonomic uncertainty and divergent taxonomic concepts between schools, we believe that morphospecies names should not be placed onto molecular phylogenies unless both the morphology and genetic type have been linked to the formally named holotype, or equivalent. Based on strict morphological criteria, we advocate using only a three-stage approach to taxonomy for practical application in micropalaeontological studies. It comprises genotyping, the production of a formal morphological description of the SEM images associated with the genetic type and then the allocation of the most appropriate taxonomic name by comparison with the formal type description. Using this approach, we were able to apply taxonomic names to fifteen genetic types. One of the remaining two may be potentially cryptic, and one is undescribed in the literature. In general, the phylogeographic distribution is in agreement with our knowledge of the ecology and biogeographical distribution of the corresponding morphospecies, highlighting the generally robust taxonomic framework of the Elphidiidae in time and space. [ABSTRACT FROM AUTHOR]

Building chronological frameworks for proxy sequences spanning 130–60 ka b2k is plagued by difficulties and uncertainties. Recent developments in the North Atlantic region, however, affirm the potential offered by tephrochronology and specifically the search for cryptotephra. Here we review the potential offered by tephrostratigraphy for sequences spanning 130–60 ka b2k. We combine newly identified cryptotephra deposits from the NGRIP ice-core and a marine core from the Iceland Basin with previously published data from the ice and marine realms to construct the first tephrostratigraphical framework for this time-interval. Forty-three tephra or cryptotephra deposits are incorporated into this framework; twenty three tephra deposits are found in the Greenland ice-cores, including nine new NGRIP tephras, and twenty separate deposits are preserved in various North Atlantic marine sequences. Major, minor and trace element results are presented for the new NGRIP horizons together with age estimates based on their position within the ice-core record. Basaltic tephras of Icelandic origin dominate the framework with only eight tephras of rhyolitic composition found. New results from marine core MD99-2253 also illustrate some of the complexities and challenges of assessing the depositional integrity of marine cryptotephra deposits. Tephra-based correlations in the marine environment provide independent tie-points for this time-interval and highlight the potential of widening the application of tephrochronology. Further investigations, however, are required, that combine robust geochemical fingerprinting and a rigorous assessment of tephra depositional processes, in order to trace coeval events between the two depositional realms. [ABSTRACT FROM AUTHOR]

Abstract: Certain marginal marine environments, such as the Scottish fjord systems, contain high-resolution records of palaeoclimatic change in which decadal to centennial climatic events can be resolved. This paper explores the possibilities of using tephrochronology to stratigraphically constrain the timing of such events in the Loch Sunart record (MD04-2831) on the NW coast of Scotland (UK). One tephra horizon (containing both silicic and basaltic shards) is identified within Late Holocene sediment with geochemical analyses of the basaltic shards suggesting an origin in the Veidivötn-Bárðarbunga volcanic system. Radiocarbon age estimates and stratigraphic information suggests that the AD 871 Landnám tephra is the most likely candidate. The shards identified within this horizon appear hydrated and indicate the operation of post-depositional weathering processes possibly influenced by the saline conditions of the fjord environment. [Copyright &y& Elsevier]

Abstract: The evolution and dynamics of the last British–Irish Ice Sheet (BIIS) have hitherto largely been reconstructed from onshore and shallow marine glacial geological and geomorphological data. This reconstruction has been problematic because these sequences and data are spatially and temporally incomplete and fragmentary. In order to enhance BIIS reconstruction, we present a compilation of new and previously published ice-rafted detritus (IRD) flux and concentration data from high-resolution sediment cores recovered from the NE Atlantic deep-sea continental slope adjacent to the last BIIS. These cores are situated adjacent to the full latitudinal extent of the last BIIS and cover Marine Isotope Stages (MIS) 2 and 3. Age models are based on radiocarbon dating and graphical tuning of abundances of the polar planktonic foraminifera Neogloboquadrina pachyderma sinistral (% Nps) to the Greenland GISP2 ice core record. Multiple IRD fingerprinting techniques indicate that, at the selected locations, most IRD are sourced from adjacent BIIS ice streams except in the centre of Heinrich (H) layers in which IRD shows a prominent Laurentide Ice Sheet provenance. IRD flux data are interpreted with reference to a conceptual model explaining the relations between flux, North Atlantic hydrography and ice dynamics. Both positive and rapid negative mass balance can cause increases, and prominent peaks, in IRD flux. First-order interpretation of the IRD record indicates the timing of the presence of the BIIS with an actively calving marine margin. The records show a coherent latitudinal, but partly phased, signal during MIS 3 and 2. Published data indicate that the last BIIS initiated during the MIS 5/4 cooling transition; renewed growth just before H5 (46ka) was succeeded by very strong millennial-scale variability apparently corresponding with Dansgaard–Oeschger (DO) cycles closely coupled to millennial-scale climate variability in the North Atlantic region involving latitudinal migration of the North Atlantic Polar Front. This indicates that the previously defined “precursor events” are not uniquely associated with H events but are part of the millennial-scale variability. Major growth of the ice sheet occurred after 29ka with the Barra Ice Stream attaining a shelf-edge position and generating turbiditic flows on the Barra–Donegal Fan at ∼27ka. The ice sheet reached its maximum extent at H2 (24ka), earlier than interpreted in previous studies. Rapid retreat, initially characterised by peak IRD flux, during Greenland Interstadial 2 (23ka) was followed by readvance between 22 and 16ka. Readvance during H1 was only characterised by BIIS ice streams draining central dome(s) of the ice sheet, and was followed by rapid deglaciation and ice exhaustion. The evidence for a calving margin and IRD supply from the BIIS during Greenland Stadial 1 (Younger Dryas event) is equivocal. The timing of the initiation, maximum extent, deglacial and readvance phases of the BIIS interpreted from the IRD flux record is strongly supported by recent independent data from both the Irish Sea and North Sea sectors of the ice sheet. [Copyright &y& Elsevier]

Fjord sediments are recognized as hotspots for the burial and storage of organic carbon, yet little is known about the long-term drivers of significant terrestrial organic carbon (OC) transfers into these coastal carbon stores. The mid-latitude fjord catchments of Scotland have a long history of human occupation and environmental disturbance. We provide new evidence to show that increased anthropogenic disturbances over the last 500 years appear to have driven a step change in the magnitude of terrestrial OC transported to the coastal ocean. Increased pressures from mining, agriculture and forestry over the latter half of the last millennium have destabilized catchment soils and remobilized deep stores of aged OC from the catchment to the coastal ocean. Here we show that fjord sediments are capable of acting as highly responsive and effective terrestrial OC sinks, with OC accumulation rates increasing up to 20% during the peak period of anthropogenic disturbance. The responsiveness and magnitude of the fjord OC sink represents a potentially significant time-evolving component of the global carbon cycle that is currently not recognized but has the potential to become increasingly important in the understanding of the role of these coastal carbon stores in our climate system. • Fjord sediments are highly responsive OC sinks adapting to changing pressures. • Human disturbance in the catchment drives aged terrestrial OC input to the fjord. • OCAR over the last 500 years have risen by 20% driven by anthropogenic disturbance. • Climate preconditions catchments increasing their sensitivity to human disturbance. [ABSTRACT FROM AUTHOR]

The genetic diversity, morphology and biogeography of Ammonia specimens was investigated across the Northeast (NE) Atlantic margins, to enhance the regional (palaeo)ecological studies based on this genus. Living specimens were collected from 22 sampling locations ranging from Shetland to Portugal to determine the distribution of Ammonia genetic types across the NE Atlantic shelf biomes. We successfully imaged (via scanning electron microscopy, SEM) and genotyped 378 Ammonia specimens, based on the small subunit (SSU) rRNA gene, linking morphology to genetic type. Phylogenetic analyses enabled identification of seven genetic types and subtypes inhabiting the NE Atlantic margins. Where possible, we linked SSU genetic types to the established large subunit (LSU) T-type nomenclature of Hayward et al. (2004). SSU genetic types with no matching T-type LSU gene sequences in GenBank were allocated new T-numbers to bring them in line with the widely adopted T-type nomenclature. The genetic types identified in the NE Atlantic margins are T1, T2, T3, T6, and T15, with both T2 and T3 being split further into the subtypes T2A and T2B, and T3S and T3V respectively. The seven genetic types and subtypes exhibit different biogeographical distributions and/or ecological preferences, but co-occurrence of two or more genetic types is common. A shore-line transect at Dartmouth (South England) demonstrates that sampling position on shore (high, middle or low shore) influences the genetic type collected, the numbers of genetic types that co-occur, and the numbers of individuals collected. We performed morphometric analysis on the SEM images of 158 genotyped Ammonia specimens. T15 and the subtypes T3S and T3V can be morphologically distinguished. We can unequivocally assign the taxonomic names A. batava and A. falsobeccarii to T3S and T15, respectively. However, the end members of T1, T2A, T2B and T6 cannot be unambiguously distinguished, and therefore these genetic types are partially cryptic. However, we confirm that T2A can be assigned to A. aberdoveyensis, but caution must be taken in warm provinces where the presence of T2B will complicate the morphological identification of T2A. We suggest that T6 should not currently be allocated to the Pliocene species A. aomoriensis due to morphological discrepancies with the taxonomic description and to the lack of genetic information. Of significance is that these partially cryptic genetic types frequently co-occur, which has considerable implications for precise species identification and accurate data interpretation. • Largest ever survey of Ammonia sp. in the Northeast Atlantic margins to aid taxonomic delineation. • All specimens are SEM imaged, SSU genotyped and morphometrically analysed. • Of seven genetic types and subtypes, four are partially cryptic, but can co-occur. • Genetic types have different biogeographies and ecologies, aiding identification. • Taxonomic assignment is currently possible for only three of the genetic types. [ABSTRACT FROM AUTHOR]