Multi-elemental composition of authigenic carbonates in benthic foraminifera from the eastern Bering Sea continental margin (International Ocean Discovery Program Site U1343)

This is the final version. Available from Elsevier via the DOI in this record. Bering Sea sediments represent exceptional archives, offering the potential to study past climates and biogeochemistry at a high resolution. However, abundant hydrocarbons of microbial origin, especially along the eastern Bering Sea continental margin, can hinder the applicability of palaeoceanographic proxies based on calcareous foraminifera, due to the formation of authigenic carbonates. Nonetheless, authigenic carbonates may also bear unique opportunities to reconstruct changes in the sedimentary redox environment. Here we use a suite of visual and geochemical evidence from single-specimens of the shallow infaunal benthic foraminiferal species Elphidium batialis Saidova (1961), recovered from International Ocean Discovery Program (IODP) Site U1343 in the eastern Bering Sea, to investigate the influence of authigenic carbonates on the foraminiferal trace metal composition. Our results demonstrate that foraminiferal calcite tests act as a nucleation template for secondary carbonate precipitation, altering their geochemistry where organoclastic sulphate reduction and anaerobic oxidation of methane cause the formation of low- and high-Mg calcite, respectively. The authigenic carbonates can occur as encrusting on the outside and/or inside of foraminiferal tests, in the form of recrystallization of the test wall, or as banding along natural laminations within the foraminiferal test walls. In addition to Mg, authigenic carbonates are enriched in U/Ca, Mn/Ca, Fe/Ca, and Sr/Ca, depending on the redox environment that they were formed in. Our results demonstrate that site-specific U/Ca thresholds are a promising tool to distinguish between diagenetically altered and pristine foraminiferal samples, important for palaeoceanographic reconstructions utilising the primary foraminiferal geochemistry. Consistent with previous studies, U/Mn ratios of foraminifera at IODP Site U1343 increase according to their degree of diagenetic alteration, suggesting a potential response of authigenic U/Mn to the microbial activity in turn linked to the sedimentary redox environment.BGS University Funding Initiative Ph.D. studentshi

Surface changes in the eastern Labrador Sea around the onset of the Little Ice Age

Despite the relative climate stability of the present interglacial, it has been punctuated by several centennial-scale climatic oscillations; the latest of which are often colloquially referred to as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA). The most favored explanation for the cause of these anomalies is that they were triggered by variability in solar irradiance and/or volcanic activity and amplified by ocean-atmosphere-sea ice feedbacks. As such, changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) are widely believed to have been involved in the amplification of such climatic oscillations. The Labrador Sea is a key area of deep water formation. The waters produced here contribute approximately one third of the volume transport of the deep limb of the AMOC and drive changes in the North Atlantic surface hydrography and subpolar gyre circulation. In this study, we present multiproxy reconstructions from a high-resolution marine sediment core located south of Greenland that suggest an increase in the influence of polar waters reaching the Labrador Sea close to MCA-LIA transition. Changes in freshwater forcing may have reduced the formation of Labrador Sea Water and contributed toward the onset of the LIA cooling. © 2014. The Authors

Relation of sortable silt grain-size to deep-sea current speeds: Calibration of the ‘Mud Current Meter’

© 2017 Elsevier Ltd Fine grain-size parameters have been used for inference of palaeoflow speeds of near-bottom currents in the deep-sea. The basic idea stems from observations of varying sediment size parameters on a continental margin with a gradient from slower flow speeds at shallower depths to faster at deeper. In the deep-sea, size-sorting occurs during deposition after benthic storm resuspension events. At flow speeds below 10–15 cm s −1 mean grain-size in the terrigenous non-cohesive ‘sortable silt’ range (denoted by SS¯, mean of 10–63 µm) is controlled by selective deposition, whereas above that range removal of finer material by winnowing is also argued to play a role. A calibration of the SS¯ grain-size flow speed proxy based on sediment samples taken adjacent to sites of long-term current meters set within ~100 m of the sea bed for more than a year is presented here. Grain-size has been measured by either Sedigraph or Coulter Counter, in some cases both, between which there is an excellent correlation for SS¯ (r = 0.96). Size-speed data indicate calibration relationships with an overall sensitivity of 1.36 ± 0.19 cm s −1 /μm. A calibration line comprising 12 points including 9 from the Iceland overflow region is well defined, but at least two other smaller groups (Weddell/Scotia Sea and NW Atlantic continental rise/Rockall Trough) are fitted by sub-parallel lines with a smaller constant. This suggests a possible influence of the calibre of material supplied to the site of deposition (not the initial source supply) which, if depleted in very coarse silt (31–63 µm), would limit SS¯ to smaller values for a given speed than with a broader size-spectrum supply. Local calibrations, or a core-top grain-size and local flow speed, are thus necessary to infer absolute speeds from grain-size. The trend of the calibrations diverges markedly from the slope of experimental critical erosion and deposition flow speeds versus grain-size, making it unlikely that the SS¯ (or any deposit size for that matter) is simply predicted by the deposition threshold. A more probable control is the rate of deposition of the different size fractions under changing flows over several tens of years (the typical averaging period of a centimetre of deposited sediment). This suggestion is supported by a simple depositional model for which the deposited SS¯ is calculated from measured currents with a size-varying depositional threshold. More surficial sediment samples taken near long-term current meter sites are needed to make calibrations more robust and explore regional differences

Deep water flow speed and surface ocean changes in the subtropical North Atlantic during the last deglaciation

Climate fluctuations during the last deglaciation have been linked to changes in the North Atlantic Meridional Overturning Circulation (MOC) through its modulation of northward marine heat transport. Consequently, much research into the causes of rapid climate change has focused on the northern North Atlantic as a key component of global ocean circulation. The production of cold, deep waters in the Southern Ocean is an important factor in the Earth's heat budget, but the involvement of deep Southern Sourced Water (SSW) in deglacial climate change has yet to be fully established. Here we use terrigenous silt grain size data from two ocean sediment cores retrieved from the western subtropical North Atlantic to reconstruct past changes in the speed of deepwater flow. The first core site is located under the influence of Lower North Atlantic Deep Water (LNADW), and is representative of changes in the MOC. The second core site is close to the modern boundary between LNADW/SSW and is therefore ideally positioned to detect changes in SSW delivery to the North Atlantic. We find evidence for a broad-scale difference in flow speed changes at the two sites, with the presence of a vigorous, but poorly ventilated SSW mass at ~ 4200 m water depth during the cold episodes of the last deglaciation when shallower (2975 m water depth) grain size and geochemical data suggest that Northern Sourced Water (NSW) was suppressed

Reconstructing North Atlantic marine climate variability using an absolutely-dated sclerochronological network

This is the final version of the article. Available from Elsevier via the DOI in this record.Reconstructing regional to hemispheric-scale climate variability requires the application of spatially representative and climatically sensitive proxy archives. Large spatial networks of dendrochronologies have facilitated the reconstruction of atmospheric variability and inferred variability in the Atlantic Ocean system. However, the marine environment has hitherto lacked the direct application of the spatial network approach because of the small number of individual absolutely-dated marine archives. In this study we present the first analyses of a network of absolutely-dated annually-resolved growth increment width chronologies from the marine bivalves Glycymeris glycymeris and Arctica islandica. The network contains eight chronologies spanning > 500 km along the western British continental shelf from the southern Irish Sea to North West Scotland. Correlation analysis of the individual chronologies and a suite of climate indices, including the Atlantic Multidecadal Oscillation (AMO), Central England surface air temperature (CET), northeast Atlantic sea surface temperatures (SST's) and the winter North Atlantic Oscillation (wNAO), demonstrates that, despite the large geographical distances been sites and the heterogeneous nature of the marine environment, the increment width variability in these series contains an element of coherence likely driven by a common response to changing environmental forcing. A nested Principal component analysis (PCA) was used to construct five composite series which explain between 31% and 74% of the variance across the individual chronologies. Linear regression analyses indicate that the composite series explain up to 41% of the variance in Northeast Atlantic SSTs over the calibration period (1975–2000). Calibration verification (reduction of error [RE] and coefficient of efficiency [CE]) statistics indicate that the composite series contains significant skill at reconstructing multi-decadal northeast Atlantic SST variability over the past two centuries (1805–2010). These data suggest that composite series derived from sclerochronology networks can facilitate the robust reconstruction of marine climate over past centuries to millennia providing invaluable baseline records of natural oceanographic variability.This work was supported financially by the NERC funded project Climate of the Last Millennium Project (CLAM; project No. NE/N001176/1) and the Marie Curie Frame work Partnership Annually Resolved Archives of Marine Climate Change (ARAMACC; Project No. FP7 604802). The authors would like to thank the three anonymous reviewer‘s for their constructive comments during the peer review process

Isolating and Reconstructing Key Components of North Atlantic Ocean Variability From a Sclerochronological Spatial Network

This is the final version. Available from AGU via the DOI in this record.Our understanding of North Atlantic Ocean variability within the coupled climate system is limited by the brevity of instrumental records and a deficiency of absolutely dated marine proxies. Here we demonstrate that a spatial network of marine stable oxygen isotope series derived from molluscan sclerochronologies (δ18Oshell) can provide skillful annually resolved reconstructions of key components of North Atlantic Ocean variability with absolute dating precision. Analyses of the common δ18Oshell variability, using principal component analysis, highlight strong connections with tropical North Atlantic and subpolar gyre (SPG) sea surface temperatures and sea surface salinity in the North Atlantic Current (NAC) region. These analyses suggest that low-frequency variability is dominated by the tropical Atlantic signal while decadal variability is dominated by variability in the SPG and salinity transport in the NAC. Split calibration and verification statistics indicate that the composite series produced using the principal component analysis can provide skillful quantitative reconstructions of tropical North Atlantic and SPG sea surface temperatures and NAC sea surface salinities over the industrial period (1864–2000). The application of these techniques with extended individual δ18Oshell series provides powerful baseline records of past North Atlantic variability into the unobserved preindustrial period. Such records are essential for developing our understanding of natural climate variability in the North Atlantic Ocean and the role it plays in the wider climate system, especially on multidecadal to centennial time scales, potentially enabling reduction of uncertainties in future climate predictions

Annually resolved North Atlantic marine climate over the last millennium

This is the final version of the article. Available from Nature Publishing Group via the DOI in this record.Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ(18)O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ(18)O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key drivers of climate variability over the last millennium. During the pre-industrial period (AD 1000-1800) variability in the sub-polar North Atlantic leads changes in Northern Hemisphere surface air temperatures at multi-decadal timescales, indicating that North Atlantic Ocean dynamics played an active role in modulating the response of the atmosphere to solar and volcanic forcing.We thank the members of the RV Bjarni Sæmundsson (Cruise No. B05-2006). This work was supported by the NERC-funded ULTRA project (Grant Number NE/H023356/1), NERC-funded CLAM project; (Project No. NE/N001176/1) and EU Millennium Project (Project number 017008). This study is a contribution to the Climate Change Consortium for Wales (C3W). We thank Brian Long (Bangor University) and Dr Julia Becker (Cardiff University) for their technical support, and Dr Manfred Mudelsee for his assistance with the trend analysis. We thank Dr Jessica Tierney and an anonymous reviewer for providing the constructive comments in the reviewing process

Closure of the Bering Strait caused Mid-Pleistocene Transition cooling

This is the final version. Available from Springer Nature via the DOI in this record. Data availability: All data generated during this study supporting its findings are available within the paper and the supplementary information.The Mid-Pleistocene Transition (MPT) is characterised by cooling and lengthening glacial cycles from 600–1200 ka, thought to be driven by reductions in glacial CO2 in particular from ~900 ka onwards. Reduced high latitude upwelling, a process that retains CO2 within the deep ocean over glacials, could have aided drawdown but has so far not been constrained in either hemisphere over the MPT. Here, we find that reduced nutrient upwelling in the Bering Sea, and North Pacific Intermediate Water expansion, coincided with the MPT and became more persistent at ~900 ka. We propose reduced upwelling was controlled by expanding sea ice and North Pacific Intermediate Water formation, which may have been enhanced by closure of the Bering Strait. The regional extent of North Pacific Intermediate Water across the subarctic northwest Pacific would have contributed to lower atmospheric CO2 and global cooling during the MPT.Natural Environment Research Council (NERC)National Research Foundation of Kore

Principles of crystal growth of intermetallic and oxide compounds from molten solutions

We present a tutorial on the principles of crystal growth of intermetallic and oxide compounds from molten solutions, with an emphasis on the fundamental principles governing the underlying phase equilibria and phase diagrams of multicomponent systems.Comment: 43 pages, 24 figures; Philosophical Magazine, 201

Weekly platinum-based chemotherapy versus 3-weekly platinum-based chemotherapy for newly diagnosed ovarian cancer (ICON8): quality-of-life results of a phase 3, randomised, controlled trial

BACKGROUND: The ICON8 study reported no significant improvement in progression-free survival (a primary endpoint) with weekly chemotherapy compared with standard 3-weekly treatment among patients with epithelial ovarian cancer. All ICON8 patients were eligible to take part in the accompanying health-related quality-of-life study, which measured the effect of treatment on self-reported wellbeing, reported here. METHODS: In this open-label, randomised, controlled, phase 3, three-arm, Gynecologic Cancer Intergroup (GCIG) trial done at 117 hospital sites in the UK, Australia, New Zealand, Mexico, South Korea, and Republic of Ireland, women (aged at least 18 years) with newly diagnosed, histologically confirmed International Federation of Gynecology and Obstetrics stage IC-IV ovarian cancer and an Eastern Cooperative Oncology Group performance status of 0-2 were randomly assigned (1:1:1) centrally using minimisation to group 1 (intravenous carboplatin area under the curve [AUC]5 or AUC6 and 175 mg/m2 intravenous paclitaxel every 3 weeks), group 2 (carboplatin AUC5 or AUC6 every 3 weeks and 80 mg/m2 paclitaxel weekly), or group 3 (carboplatin AUC2 weekly and 80 mg/m2 paclitaxel weekly). Randomisation was stratified by GCIG group, disease stage, and outcome and timing of surgery. Patients and clinicians were not masked to treatment assignment. Patients underwent immediate or delayed primary surgery according to clinicians' choice. Patients were asked to complete European Organisation for Research and Treatment of Cancer QLQ-C30 and QLQ-OV28 questionnaires at enrolment, before each chemotherapy cycle, then 6-weekly up to 9 months, 3-monthly up to 2 years, and 6-monthly up to 5 years. Quality of life was a prespecified secondary outcome of the ICON8 study. Within the quality-of-life study, the co-primary endpoints were QLQ-C30 global health score at 9 months (cross-sectional analysis) and mean QLQ-C30 global health score from randomisation to 9 months (longitudinal analysis). Data analyses were done on an intention-to-treat basis. The trial is registered on ClinicalTrials.gov, NCT01654146 and ISRCTN Registry, ISRCTN10356387, and is currently in long-term follow up. FINDINGS: Between June 6, 2011, and Nov 28, 2014, 1566 patients were recruited into ICON8 (522 were included in group 1, 523 in group 2, and 521 in group 3). Baseline quality-of-life questionnaires were completed by 1438 (92%) of 1566 patients and 9-month questionnaires by 882 (69%) of 1280 patients. We observed no significant difference in global health score at 9 months (cross-sectional analysis) between study groups (group 2 vs group 1, difference in mean score 2·3, 95% CI -0·4 to 4·9, p=0·095; group 3 vs group 1, -0·8, -3·8 to 2·2, p=0·61). Using longitudinal analysis, we found lower global health scores for those receiving weekly paclitaxel than for those receiving 3-weekly chemotherapy (group 2 vs group 1, mean difference -1·8, 95% CI -3·6 to -0·1, p=0·043; group 3 vs group 1, -2·9, -4·7 to -1·1, p=0·0018). INTERPRETATION: We found no evidence of a difference in global quality of life between treatment groups at 9 months; however, patients receiving weekly treatment reported lower mean quality of life across the 9-month period after randomisation. Taken together with the lack of progression-free survival benefit, these findings do not support routine use of weekly paclitaxel-containing regimens in the management of newly diagnosed ovarian cancer. FUNDING: Cancer Research UK, Medical Research Council, Health Research Board Ireland, Irish Cancer Society, and Cancer Australia