Assessing the continuity of the blue ice climate record at Patriot Hills, Horseshoe Valley, West Antarctica

We use high resolution Ground Penetrating Radar (GPR) to assess the continuity of the Blue Ice Area (BIA) horizontal climate record at Patriot Hills, Horseshoe Valley, West Antarctica. The sequence contains three pronounced changes in deuterium isotopic values at ~18 cal ka, ~12 cal ka and ~8 cal ka. GPR surveys along the climate sequence reveal continuous, conformable dipping isochrones, separated by two unconformities in the isochrone layers, which correlate with the two older deuterium shifts. We interpret these incursions as discontinuities in the sequence, rather than direct measures of climate change. Ice-sheet models and Internal Layer Continuity Index plots suggest that the unconformities represent periods of erosion occurring as the former ice surface was scoured by katabatic winds in front of mountains at the head of Horseshoe Valley. This study demonstrates the importance of high resolution GPR surveys for investigating both paleo-flow dynamics and interpreting BIA climate records

Inland extent of the Weddell Sea Rift imaged by new aerogeophysical data

Peer reviewedPostprin

Protected Planet Report 2018

In 2010, Parties to the Convention on Biological Diversity (CBD) adopted a Strategic Plan for Biodiversity 2011-2020, including its 20 Aichi Biodiversity Targets, in order to address biodiversity loss, ensure the sustainable use of natural resources, and equitable sharing of benefits. The Protected Planet Report 2018 provides an update of progress towards Aichi Biodiversity Target 11 at the global scale. Each chapter of the report examines a specific element of Target 11. The findings in the report are based on data held in the World Database on Protected Areas (WDPA) as of July 2018. For the first time, the printed Protected Planet Report is complemented by an online version, regularly updated with all the latest data, which can be explored at the following address: www.livereport.protectedplanet.net. Since the Strategic Plan was adopted, there has been significant progress towards achieving elements of Aichi Target 11, particularly in terms of land and sea coverage. However, significant efforts are needed to achieve other elements of the target

Biocompatibility and Physiological Thiolytic Degradability of Radically Made Thioester-Functional Copolymers: Opportunities for Drug Release

Being nondegradable, vinyl polymers have limited biomedical applicability. Unfortunately, backbone esters incorporated through conventional radical ring-opening methods do not undergo appreciable abiotic hydrolysis under physiologically relevant conditions. Here, PEG acrylate and di(ethylene glycol) acrylamide-based copolymers containing backbone thioesters were prepared through the radical ring-opening copolymerization of the thionolactone dibenzo[c,e]oxepin-5(7H)-thione. The thioesters degraded fully in the presence of 10 mM cysteine at pH 7.4, with the mechanism presumed to involve an irreversible S–N switch. Degradations with N-acetylcysteine and glutathione were reversible through the thiol–thioester exchange polycondensation of R–SC(═O)–polymer–SH fragments with full degradation relying on an increased thiolate/thioester ratio. Treatment with 10 mM glutathione at pH 7.2 (mimicking intracellular conditions) triggered an insoluble–soluble switch of a temperature-responsive copolymer at 37 °C and the release of encapsulated Nile Red (as a drug model) from core-degradable diblock copolymer micelles. Copolymers and their cysteinolytic degradation products were found to be noncytotoxic, making thioester backbone-functional polymers promising for drug delivery applications

Englacial architecture and age-depth constraints across the West Antarctic Ice Sheet

he englacial stratigraphic architecture of internal reflection horizons (IRHs) as imaged by ice‐penetrating radar (IPR) across ice sheets reflects the cumulative effects of surface mass balance, basal melt, and ice flow. IRHs, considered isochrones, have typically been traced in interior, slow‐flowing regions. Here, we identify three distinctive IRHs spanning the Institute and Möller catchments that cover 50% of West Antarctica's Weddell Sea Sector and are characterized by a complex system of ice stream tributaries. We place age constraints on IRHs through their intersections with previous geophysical surveys tied to Byrd Ice Core and by age‐depth modeling. We further show where the oldest ice likely exists within the region and that Holocene ice‐dynamic changes were limited to the catchment's lower reaches. The traced IRHs from this study have clear potential to nucleate a wider continental‐scale IRH database for validating ice sheet models

Englacial Architecture of Lambert Glacier, East Antarctica

The analysis of englacial layers using radio-echo sounding data enables the characterisation and reconstruction of current and past ice-sheet flow. Despite the Lambert Glacier catchment being one of the largest in Antarctica, discharging ~16 % of East Antarctica&rsquo;s ice, its englacial architecture has been little analysed. Here, we present a comprehensive analysis of Lambert Glacier&rsquo;s englacial architecture using radio-echo sounding data collected by the Antarctica's Gamburtsev Province Project (AGAP) North survey. We used an &ldquo;internal-layering continuity index&rdquo; (ILCI) to characterise the internal architecture of the ice and identify four macro-scale ILCI zones with distinct glaciological contexts. Whilst the catchment is dominated by continuous englacial layering, disrupted or discontinuous layering is highlighted by the ILCI at both the onset of enhanced ice flow (defined here as &gt;15 ma&minus;1) and along the shear margin, revealing the transition from internal-deformation-controlled to basal-sliding-dominated ice flow. These zones are characterised by buckled and folded englacial layers which align with the current ice-flow regime, and which we interpret as evidence that the flow direction of the Lambert Glacier trunk has changed little, if at all, during the Holocene. However, disturbed englacial layers along a deep subglacial channel that does not correspond to modern ice-flow routing suggest that ice-flow change has occurred in a former tributary which fed Lambert Glacier from grid north. As large outlet systems such as Lambert Glacier are likely to play a vital role in the future drainage of the East Antarctic Ice Sheet, constraining their englacial architecture to reconstruct their past ice flow and assess basal conditions is important.</p

The objectness of everyday life: disburdenment or engagement?

The article grew out of a conference paper, ‘The objectness of everyday life: engagement and disburdenment’, Material Geographies, UCL, September 2002. An expanded version of the paper was included in a special themed section of an issue of Geoforum. The paper intervenes into contemporary philosophical scholarship on the nature of use-value, usability, design and ethics. The article has been directly engaged with in an academic journal; Christensen, Carleton B. (2005) ‘The Material Basis of Everyday Rationality: transformation by design or education?’, Design Philosophy Papers No.4,)

Subglacial controls on the flow of Institute Ice Stream, West Antarctica

The Institute Ice Stream (IIS) rests on a reverse-sloping bed, extending >150 km upstream into the ~1.8 km deep Robin Subglacial Basin, placing it at the threshold of marine ice-sheet instability. Understanding IIS vulnerability has focused on the effect of grounding-line melting, which is forecast to increase significantly this century. Changes to ice-flow dynamics are also important to IIS stability, yet little is known about them. Here we reveal the trunk of the IIS occurs downstream of the intersection of three discrete subglacial features; a large ‘active’ subglacial lake, a newly-discovered sharp transition to a zone of weak basal sediments, and a major tectonic rift. The border of IIS trunk flow is confined by the sediment on one side, and by a transition between basal melting and freezing at the border with the Bungenstock Ice Rise. By showing how basal sediment and water dictate present-day flow of IIS, we reveal that ice-sheet stability here is dependent on this unusual arrangement

A temperate former West Antarctic ice sheet suggested by an extensive zone of bed channels

Several recent studies predict that the West Antarctic Ice Sheet will become increasingly unstable under warmer conditions. Insights on such change can be assisted through investigations of the subglacial landscape, which contains imprints of former ice-sheet behavior. Here, we present radio-echo sounding data and satellite imagery revealing a series of ancient large sub-parallel subglacial bed channels preserved in the region between the Möller and Foundation Ice Streams, West Antarctica. We suggest that these newly recognized channels were formed by significant meltwater routed along the icesheet bed. The volume of water required is likely substantial and can most easily be explained by water generated at the ice surface. The Greenland Ice Sheet today exemplifies how significant seasonal surface melt can be transferred to the bed via englacial routing. For West Antarctica, the Pliocene (2.6–5.3 Ma) represents the most recent sustained period when temperatures could have been high enough to generate surface melt comparable to that of present-day Greenland. We propose, therefore, that a temperate ice sheet covered this location during Pliocene warm periods

Assembly of infectious enteroviruses depends on multiple, conserved genomic RNA-coat protein contacts.

Picornaviruses are important viral pathogens, but despite extensive study, the assembly process of their infectious virions is still incompletely understood, preventing the development of anti-viral strategies targeting this essential part of the life cycle. We report the identification, via RNA SELEX and bioinformatics, of multiple RNA sites across the genome of a typical enterovirus, enterovirus-E (EV-E), that each have affinity for the cognate viral capsid protein (CP) capsomer. Many of these sites are evolutionarily conserved across known EV-E variants, suggesting they play essential functional roles. Cryo-electron microscopy was used to reconstruct the EV-E particle at ~2.2 Å resolution, revealing extensive density for the genomic RNA. Relaxing the imposed symmetry within the reconstructed particles reveals multiple RNA-CP contacts, a first for any picornavirus. Conservative mutagenesis of the individual RNA-contacting amino acid side chains in EV-E, many of which are conserved across the enterovirus family including poliovirus, is lethal but does not interfere with replication or translation. Anti-EV-E and anti-poliovirus aptamers share sequence similarities with sites distributed across the poliovirus genome. These data are consistent with the hypothesis that these RNA-CP contacts are RNA Packaging Signals (PSs) that play vital roles in assembly and suggest that the RNA PSs are evolutionarily conserved between pathogens within the family, augmenting the current protein-only assembly paradigm for this family of viruses