New Last Glacial Maximum Ice Thickness constraints for the Weddell Sea Embayment, Antarctica

We describe new Last Glacial Maximum (LGM) ice thickness constraints for three locations spanning the Weddell Sea Embayment (WSE) of Antarctica. Samples collected from the Shackleton Range, Pensacola Mountains, and the Lassiter Coast constrain the LGM thickness of the Slessor Glacier, Foundation Ice Stream, and grounded ice proximal to the modern Ronne Ice Shelf edge on the Antarctic Peninsula, respectively. Previous attempts to reconstruct LGM-to-present ice thickness changes around the WSE used measurements of long-lived cosmogenic nuclides, primarily Be-10. An absence of post-LGM apparent exposure ages at many sites led to LGM thickness reconstructions that were spatially highly variable and inconsistent with flow line modelling. Estimates for the contribution of the ice sheet occupying the WSE at the LGM to global sea level since deglaciation vary by an order of magnitude, from 1.4 to 14.1m of sea level equivalent. Here we use a short-lived cosmogenic nuclide, in situ-produced C-14, which is less susceptible to inheritance problems than Be-10 and other long-lived nuclides. We use in situ C-14 to evaluate the possibility that sites with no post-LGM exposure ages are biased by cosmogenic nuclide inheritance due to surface preservation by cold-based ice and non-deposition of LGM-aged drift. Our measurements show that the Slessor Glacier was between 310 and up to 655m thicker than present at the LGM. The Foundation Ice Stream was at least 800m thicker, and ice on the Lassiter Coast was at least 385m thicker than present at the LGM. With evidence for LGM thickening at all of our study sites, our in situ C-14 measurements indicate that the long-lived nuclide measurements of previous studies were influenced by cosmogenic nuclide inheritance. Our inferred LGM configuration, which is primarily based on minimum ice thickness constraints and thus does not constrain an upper limit, indicates a relatively modest contribution to sea level rise since the LGM of < 4.6 m, and possibly as little as < 1.5 m

An experimental assessment of the ignition of forest fuels by the thermal pulse generated by the Cretaceous–Palaeogene impact at Chicxulub

PublishedJournal ArticleThis is an open access article available at http://jgs.lyellcollection.org/content/172/2/175.full .© The Geological Society of London A large extraterrestrial body hit the Yucatán Peninsula at the end of the Cretaceous period. Models suggest that a substantial amount of thermal radiation was delivered to the Earth’s surface by the impact, leading to the suggestion that it was capable of igniting extensive wildfires and contributed to the end-Cretaceous extinctions. We have reproduced in the laboratory the most intense impact-induced heat fluxes estimated to have reached different points on the Earth’s surface using a fire propagation apparatus and investigated the ignition potential of forest fuels. The experiments indicate that dry litter can ignite, but live fuels typically do not, suggesting that any ignition caused by impact-induced thermal radiation would have been strongly regional dependent. The intense, but short-lived, pulse downrange and at proximal and intermediate distances from the impact is insufficient to ignite live fuel. However, the less intense but longer-lasting thermal pulse at distal locations may have ignited areas of live fuels. Because plants and ecosystems are generally resistant to single localized fire events, we conclude that any fires ignited by impact-induced thermal radiation cannot be directly responsible for plant extinctions, implying that heat stress is only part of the end-Cretaceous story.Please note C.M.B. and R.M.H. contributed equally to this paper. We thank R, Spicer, G. Upchurch and V. Vajda for their useful reviews that assisted us in improving this paper. C.M.B. acknowledges funding from a Marie Curie Career Integration Grant (PyroMap PCIG10-GA-2011-303610) and a European Research Council Starter Grant ERC-2013-StG-335891-ECOFLAM and the University of Exeter. J.V.M. acknowledges funding from the Leverhulme Trust. G.R. and R.M.H. acknowledge EPSRC Doctoral Prize funding from Imperial College London. T.G. acknowledges funding from the Lise Meitner Program of the Austrian Science Fund (FWF). We also acknowledge the influence of E. Pierazzo, who passed away during the early phases of this research, whose drive to ‘bridge the gap’ between geologists, modellers and experimentalists influenced the conception of this research

Cyclospora infection linked to travel to Mexico, June to September 2015.

Cyclospora cayetanensis was identified in 176 returned travellers from the Riviera Maya region of Mexico between 1 June and 22 September 2015; 79 in the United Kingdom (UK) and 97 in Canada. UK cases completed a food exposure questionnaire. This increase in reported Cyclospora cases highlights risks of gastrointestinal infections through travelling, limitations in Cyclospora surveillance and the need for improved hygiene in the production of food consumed in holiday resorts

No distinct local cuisines among humpback whales: A population diet comparison in the Southern Hemisphere

Southern hemisphere humpback whale (Megaptera novaeangliae, SHHW) breeding populations follow a high-fidelity Antarctic krill (Euphausia superba) diet while feeding in distinct sectors of the Southern Ocean. Their capital breeding life history requires predictable ecosystem productivity to fuel migration and migration-related behaviours. It is therefore postulated that populations feeding in areas subject to the strongest climate change impacts are more likely to show the first signs of a departure from a high-fidelity krill diet. We tested this hypothesis by investigating blubber fatty acid profiles and skin stable isotopes obtained from five SHHW populations in 2019, and comparing them to Antarctic krill stable isotopes sampled in three SHHW feeding areas in the Southern Ocean in 2019. Fatty acid profiles and δ13C and δ15N varied significantly among all five populations, however, calculated trophic positions did not (2.7 to 3.1). Similarly, fatty acid ratios, 16:1ω7c/16:0 and 20:5ω3/22:6ω3 were above 1, showing that whales from all five populations are secondary heterotrophs following an omnivorous diet with a diatom-origin. Thus, evidence for a potential departure from a high-fidelity Antarctic krill diet was not seen in any population. δ13C of all populations were similar to δ13C of krill sampled in productive upwelling areas or the marginal sea-ice zone. Consistency in trophic position and diet origin but significant fatty acid and stable isotope differences demonstrate that the observed variability arises at lower trophic levels. Our results indicate that, at present, there is no evidence of a divergence from a high-fidelity krill diet. Nevertheless, the characteristic isotopic signal of whales feeding in productive upwelling areas, or in the marginal sea-ice zone, implies that future cryosphere reductions could impact their feeding ecology

Incubation of ovine scrapie with environmental matrix results in biological and biochemical changes of PrPSc over time

Ovine scrapie can be transmitted via environmental reservoirs. A pool of ovine scrapie isolates were incubated on soil for one day or thirteen months and eluted prion was used to challenge tg338 mice transgenic for ovine PrP. After one-day incubation on soil, two PrPSc phenotypes were present: G338 or Apl338ii. Thirteen months later some divergent PrPSc phenotypes were seen: a mixture of Apl338ii with either G338 or P338, and a completely novel PrPSc deposition, designated Cag338. The data show that prolonged ageing of scrapie prions within an environmental matrix may result in changes in the dominant PrPSc biological/biochemical properties

Review article: Existing and potential evidence for Holocene grounding line retreat and readvance in Antarctica

Widespread existing geological records from above the modern ice sheet surface and outboard of the current ice margin show that the Antarctic Ice Sheet (AIS) was much more extensive at the Last Glacial Maximum (∼ 20 ka) than at present. However, whether it was ever smaller than present during the last few millennia, and (if so) by how much, is known only for a few locations because direct evidence lies within or beneath the ice sheet, which is challenging to access. Here, we describe how retreat and readvance (henceforth “readvance”) of AIS grounding lines during the Holocene could be detected and quantified using subglacial bedrock, subglacial sediments, marine sediment cores, relative sea-level (RSL) records, geodetic observations, radar data, and ice cores. Of these, only subglacial bedrock and subglacial sediments can provide direct evidence for readvance. Marine archives are of limited utility because readvance commonly covers evidence of earlier retreat. Nevertheless, stratigraphic transitions documenting change in environment may provide support for direct evidence from subglacial records, as can the presence of transgressions in RSL records, and isostatic subsidence. With independent age control, ice structure revealed by radar can be used to infer past changes in ice flow and geometry, and therefore potential readvance. Since ice cores capture changes in surface mass balance, elevation, and atmospheric and oceanic circulation that are known to drive grounding line migration, they also have potential for identifying readvance. A multidisciplinary approach is likely to provide the strongest evidence for or against a smaller-than-present AIS in the Holocene

Long-lived magnetism from solidification-driven convection on the pallasite parent body.

Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System.The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement No. 320750, the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 312284, the Natural Environment Research Council, Fundación ARAID and the Spanish MINECO MAT2011-23791.This is the accepted manuscript. The final version is available from Nature at http://www.nature.com/nature/journal/v517/n7535/full/nature14114.html

The opposing transcriptional functions of Sin3a and c-Myc are required to maintain tissue homeostasis.

How the proto-oncogene c-Myc balances the processes of stem-cell self-renewal, proliferation and differentiation in adult tissues is largely unknown. We explored c-Myc's transcriptional roles at the epidermal differentiation complex, a locus essential for skin maturation. Binding of c-Myc can simultaneously recruit (Klf4, Ovol-1) and displace (Cebpa, Mxi1 and Sin3a) specific sets of differentiation-specific transcriptional regulators to epidermal differentiation complex genes. We found that Sin3a causes deacetylation of c-Myc protein to directly repress c-Myc activity. In the absence of Sin3a, genomic recruitment of c-Myc to the epidermal differentiation complex is enhanced, and re-activation of c-Myc-target genes drives aberrant epidermal proliferation and differentiation. Simultaneous deletion of c-Myc and Sin3a reverts the skin phenotype to normal. Our results identify how the balance of two transcriptional key regulators can maintain tissue homeostasis through a negative feedback loop

An Outbreak of Cryptosporidium parvum across England & Scotland Associated with Consumption of Fresh Pre-Cut Salad Leaves, May 2012

Background We report a widespread foodborne outbreak of Cryptosporidium parvum in England and Scotland in May 2012. Cases were more common in female adults, and had no history of foreign travel. Over 300 excess cases were identified during the period of the outbreak. Speciation and microbiological typing revealed the outbreak strain to be C. parvum gp60 subtype IIaA15G2R1. Methods Hypothesis generation questionnaires were administered and an unmatched case control study was undertaken to test the hypotheses raised. Cases and controls were interviewed by telephone. Controls were selected using sequential digit dialling. Information was gathered on demographics, foods consumed and retailers where foods were purchased. Results Seventy-four laboratory confirmed cases and 74 controls were included in analyses. Infection was found to be strongly associated with the consumption of pre-cut mixed salad leaves sold by a single retailer. This is the largest documented outbreak of cryptosporidiosis attributed to a food vehicle

A plasmid DNA-launched SARS-CoV-2 reverse genetics system and coronavirus toolkit for COVID-19 research

The recent emergence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the underlying cause of Coronavirus Disease 2019 (COVID-19), has led to a worldwide pandemic causing substantial morbidity, mortality, and economic devastation. In response, many laboratories have redirected attention to SARS-CoV-2, meaning there is an urgent need for tools that can be used in laboratories unaccustomed to working with coronaviruses. Here we report a range of tools for SARS-CoV-2 research. First, we describe a facile single plasmid SARS-CoV-2 reverse genetics system that is simple to genetically manipulate and can be used to rescue infectious virus through transient transfection (without in vitro transcription or additional expression plasmids). The rescue system is accompanied by our panel of SARS-CoV-2 antibodies (against nearly every viral protein), SARS-CoV-2 clinical isolates, and SARS-CoV-2 permissive cell lines, which are all openly available to the scientific community. Using these tools, we demonstrate here that the controversial ORF10 protein is expressed in infected cells. Furthermore, we show that the promising repurposed antiviral activity of apilimod is dependent on TMPRSS2 expression. Altogether, our SARS-CoV-2 toolkit, which can be directly accessed via our website at https://mrcppu-covid.bio/, constitutes a resource with considerable potential to advance COVID-19 vaccine design, drug testing, and discovery science