Response of the large-scale subglacial drainage system of Northeast Greenland to surface elevation changes

The influence of subglacial water on the dynamics of ice flow has been the object of increasing interest in the past decade. In this study we focus on large-scale, long-term changes in surface elevation over Northeast Greenland and the corresponding changes in subglacial water routeways. Our results show that over timescales ranging from decades to millennia the area may experience redistribution of and fluctuation in subglacial water outflux under the main glacier outlets. The fluctuations in subglacial water routing occur even in the absence of external forcing. Based on these results we conclude that changes in the subglacial water routeways are an intrinsic part of the drainage basin dynamics, where the subglacial system is likely always in a transient state. The results also imply that fluctuations at the margins observed at present might originate from changes several hundred kilometres upstream. Since surface elevation changes may propagate upstream over timescales much longer than the observational period, the cause of the fluctuations may not be present in current observational records

Competition between Diffusion and Fragmentation: An Important Evolutionary Process of Nature

We investigate systems of nature where the common physical processes diffusion and fragmentation compete. We derive a rate equation for the size distribution of fragments. The equation leads to a third order differential equation which we solve exactly in terms of Bessel functions. The stationary state is a universal Bessel distribution described by one parameter, which fits perfectly experimental data from two very different system of nature, namely, the distribution of ice crystal sizes from the Greenland ice sheet and the length distribution of alpha-helices in proteins.Comment: 4 pages, 3 figures, (minor changes

Past4Future: European interdisciplinary research on past warm climate periods.

Past4Future was a Collaborative Project in the European Union’s Framework Programme 7; it aimed to generate knowledge about climate changes during the last two interglacials. The approach was to combine proxy data with climate model simulations to investigate the existence and the cause of past abrupt climate changes during warm climate periods in order to evaluate the risk of abrupt changes in the future. Featuring contributions from a number of Past4Future participants, this Science Highlights section of PAGES Magazine showcases the cross-disciplinary nature of this very successful project that ended in December 2014

Change of the ice rheology with climatic transitions – implication on ice flow modelling and dating of the EPICA Dome C core

International audienceThe study of the distribution of the crystallographic orientations (the fabric) along ice cores supplies information on the past and current ice flows of ice-sheets. Beside the usually observed formation of a vertical single maximum fabric, the EPICA Dome Concordia ice core (EDC) shows an abrupt and unexpected strenghtening of its fabric during termination II around 1750 m depth. Such strengthenings were already observed for sites located on an ice-sheet. This suggests that horizontal shear could occur along the EDC core. Moreover, the change in the fabric leads to a modification of the viscosity between neighbouring ice layers. Through the use of an anisotropic ice flow model, we quantify the change in viscosity and investigate its implication on ice flow and dating

Change in ice rheology during climate variations – implications for ice flow modelling and dating of the EPICA Dome C core

The study of the distribution of crystallographic orientations (i.e., the fabric) along ice cores provides information on past and current ice flow in ice-sheets. Besides the usually observed formation of a vertical single maximum fabric, the EPICA Dome C ice core (EDC) shows an abrupt and unexpected strengthening of its fabric during termination II around 1750 m depth. Such strengthening has already been observed for sites located on an ice-sheet flank. This suggests that horizontal shear could occur along the EDC core. Moreover, the change in the fabric leads to a modification of the effective viscosity between neighbouring ice layers. Through the use of an anisotropic ice flow model, we quantify the change in effective viscosity and investigate its implication for ice flow and dating

PVN-LOT-414-C-005

UnlabelledEngineering microbial hosts for the production of fungible fuels requires mitigation of limitations posed on the production capacity. One such limitation arises from the inherent toxicity of solvent-like biofuel compounds to production strains, such as Escherichia coli. Here we show the importance of host engineering for the production of short-chain alcohols by studying the overexpression of genes upregulated in response to exogenous isopentenol. Using systems biology data, we selected 40 genes that were upregulated following isopentenol exposure and subsequently overexpressed them in E. coli. Overexpression of several of these candidates improved tolerance to exogenously added isopentenol. Genes conferring isopentenol tolerance phenotypes belonged to diverse functional groups, such as oxidative stress response (soxS, fpr, and nrdH), general stress response (metR, yqhD, and gidB), heat shock-related response (ibpA), and transport (mdlB). To determine if these genes could also improve isopentenol production, we coexpressed the tolerance-enhancing genes individually with an isopentenol production pathway. Our data show that expression of 6 of the 8 candidates improved the production of isopentenol in E. coli, with the methionine biosynthesis regulator MetR improving the titer for isopentenol production by 55%. Additionally, expression of MdlB, an ABC transporter, facilitated a 12% improvement in isopentenol production. To our knowledge, MdlB is the first example of a transporter that can be used to improve production of a short-chain alcohol and provides a valuable new avenue for host engineering in biogasoline production.ImportanceThe use of microbial host platforms for the production of bulk commodities, such as chemicals and fuels, is now a focus of many biotechnology efforts. Many of these compounds are inherently toxic to the host microbe, which in turn places a limit on production despite efforts to optimize the bioconversion pathways. In order to achieve economically viable production levels, it is also necessary to engineer production strains with improved tolerance to these compounds. We demonstrate that microbial tolerance engineering using transcriptomics data can also identify targets that improve production. Our results include an exporter and a methionine biosynthesis regulator that improve isopentenol production, providing a starting point to further engineer the host for biogasoline production

A unified earthquake catalogue for the North Sea to derisk European CCS operations

Carbon capture and storage (CCS) technology is essential to European decarbonisation efforts, and several offshore CO2 storage projects are being developed in the North Sea. Understanding the geomechanical response to CO2 injection is key to both the pre-characterisation and operation of a storage reservoir. A thorough assessment of seismicity gives critical insights into the stress field and faulting around reservoirs, both key controls on the geomechanical response to injection. Seismicity also illuminates potential hydraulic pathways for leakage, be it directly by revealing the extent of faults, or indirectly through fractures imaged by measurements of seismic anisotropy. High quality seismicity data is critical to underpin all of these methods of analysis. This paper presents the most complete catalogue of seismicity in the North Sea to date. The combined data are enabling revised assessments of seismic hazard and leakage risk in the North Sea, as well as a better understanding of faulting and stress. This study shows the value of unifying disparate seismicity data, allowing for more accurate seismological analyses. These lay the foundation for better management of risks for not only geologic CO2 storage, but other offshore industries and infrastructure

Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland

Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near‐surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation‐induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes are crucial to both the interpretation of ice core climate proxies and the formulation of isotope‐enabled general circulation models. Here, we present continuous measurements of the water isotopic composition in surface snow and atmospheric vapor together with near‐surface atmospheric turbulence and snow‐air latent and sensible heat fluxes, obtained at the East Greenland Ice‐Core Project drilling site in summer 2016. For two 4‐day‐long time periods, significant diurnal variations in atmospheric water isotopologues are observed. A model is developed to explore the impact of this variability on the surface snow isotopic composition. Our model suggests that the snow isotopic composition in the upper subcentimeter of the snow exhibits a diurnal variation with amplitudes in δ18O and δD of ~2.5‰ and ~13‰, respectively. As comparison, such changes correspond to 10–20% of the magnitude of seasonal changes in interior Greenland snow pack isotopes and of the change across a glacial‐interglacial transition. Importantly, our observation and model results suggest, that sublimation‐induced fractionation needs to be included in simulations of exchanges between the vapor and the snow surface on diurnal timescales during summer cloud‐free conditions in northeast Greenland