Search

We present laboratory experiments on the growth of a tubular ice structure surrounding a plume of cold brine that descends under gravity into water with a higher freezing point. Brinicles are geological analogues of these structures found under sea ice in the polar regions on Earth. Brinicles are hypothesized to exist in the oceans of other celestial bodies, and being environments rich in minerals, serve a potentially analogous role as an ecosystem on icy-ocean worlds to that of submarine hydrothermal vents on Earth. [ABSTRACT FROM AUTHOR]

We employ nonequilibrium molecular dynamics simulations to investigate the structure and dynamics of a cholesteric liquid crystal confined between atomically corrugated solid walls. By choosing walls normal to the helical axis, we can study systems with an arbitrary cholesteric pitch without exposing the cholesteric helix to a spurious stress. We investigate the effects of local heating and flow and their joint effects. A steady-state laminar Poiseuille flow is initiated by means of an external body force. Flow alone (i.e., without local heating) in a direction normal to the helical axis does not affect the cholesteric pitch. If the liquid crystal is heated in a small region, the cholesteric helix becomes unstable and melts locally. However, if local heating and flow are combined, a nontrivial synergistic effect is observed in that the helical structure recuperates the better, the higher the speed of the flow is. [ABSTRACT FROM AUTHOR]

We present laboratory experiments on the growth of a tubular ice structure surrounding a plume of cold brine that descends under gravity into water with a higher freezing point. Brinicles are geological analogues of these structures found under sea ice in the polar regions on Earth. They may be important for the energy budget of sea ice. Brinicles are hypothesized to exist in the oceans of other celestial bodies, and being environments rich in minerals, serve a potentially analogous role as an ecosystem on icy ocean worlds to that of submarine hydrothermal vents on Earth. [ABSTRACT FROM AUTHOR]

During the past 20 years, multi-channel radar emerged as a key tool for deciphering an ice sheet's internal architecture. To assign ages to radar reflections and connect them over large areas in the ice sheet, the layer genesis has to be understood on a microphysical scale. Synthetic radar trace modelling based on the dielectric profile of ice cores allows for the assignation of observed physical properties' variations on the decimetre scale to radar reflectors extending from the coring site to a regional or even whole-ice-sheet scale. In this paper we rely on the available dielectric profiling data of the northern Greenland deep ice cores: NGRIP, NEEM and EGRIP. The three records are well suited for assigning an age model to the stratigraphic radar-mapped layers, and linking up the reflector properties to observations in the cores. Our modelling results show that the internal reflections are mainly due to conductivity changes. Furthermore, we deduce fabric characteristics at the EGRIP drill site from two-way-travel-time differences of along and across-flow polarized radarwave reflections of selected horizons (below 980 m). These indicate in deeper parts of the ice column an across-flow concentrated c-axis fabric. [ABSTRACT FROM AUTHOR]

Impurities in polar ice do not only allow the reconstruction of past atmospheric aerosol concentrations but also influence the physical properties of the ice. However, the localisation of impurities inside the microstructure is still under debate and little is known about the mineralogy of solid inclusions. In particular, the general mineralogical diversity throughout an ice core and the specific distribution inside the microstructure is poorly investigated; the impact of the mineralogy on the localisation of inclusions and other processes is thus hardly known. We use dust particle concentration, optical microscopy, and cryo-Raman spectroscopy to systematically locate and analyse the mineralogy of micro-inclusions in situ inside 11 solid ice samples from the upper 1340 m of the East Greenland Ice Core Project ice core. Micro-inclusions are more variable in mineralogy than previously observed and are mainly composed of mineral dust (quartz, mica, and feldspar) and sulfates (mainly gypsum). Inclusions of the same composition tend to cluster, but clustering frequency and mineralogy changes with depth. A variety of sulfates dominate the upper 900 m, while gypsum is the only sulfate in deeper samples, which however contain more mineral dust, nitrates, and dolomite. The analysed part of the core can thus be divided into two depth regimes of different mineralogy, and to a lesser degree of spatial distribution, which could originate from different chemical reactions in the ice or large-scale changes in ice cover in northeast Greenland during the mid-Holocene. The complexity of impurity mineralogy on the metre scale and centimetre scale in polar ice is still underestimated, and new methodological approaches are necessary to establish a comprehensive understanding of the role of impurities. Our results show that applying new methods to the mineralogy in ice cores and recognising its complexity, as well as the importance for localisation studies, open new avenues for understanding the role of impurities in ice cores. [ABSTRACT FROM AUTHOR]

Impurities deposited in polar ice enable the reconstruction of the atmospheric aerosol concentration of the past. At the same time they impact the physical properties of the ice itself such as its deformation behaviour. Impurities are thought to enhance ice deformation, but observations are ambiguous due to a shortage of comprehensive microstructural analyses. For the first time, we systematically analyse micro-inclusions in polar fast flowing ice, i.e. from the East Greenland Ice Core Project ice core drilled through the Northeast Greenland Ice Stream. In direct relation to the inclusions we derive the crystal preferred orientation, fabric, grain size, and microstructural features at 10 depths, covering the Holocene and Late Glacial. We use optical microscopy to create microstructure maps to analyse the in situ locations of inclusions in the polycrystalline, solid ice samples. Micro-inclusions are more variable in spatial distribution than previously observed and show various distributional patterns ranging from centimetre-thick layers to clusters and solitary particles, independent of depth. In half of all samples, micro-inclusions are more often located at or close to the grain boundaries by a slight margin (in the areas occupied by grain boundaries). Throughout all samples we find strong indications of dynamic recrystallisation, such as grain islands, bulging grains, and different types of sub-grain boundaries. We discuss the spatial variability in micro-inclusions, the link between spatial variability and mineralogy, and possible effects on the microstructure and deformation behaviour of the ice. Our results emphasise the need for holistic approaches in future studies, combining microstructure and impurity analysis. [ABSTRACT FROM AUTHOR]

This study focuses on articulation of national identity on social media, specifically Twitter. First, it tackles discursive and other devices employed by politicians in order to negotiate national identity on social media platforms such as Twitter. Second, the study tries to identify whether populist rhetoric strategies are adopted to disseminate political agenda through social media and if and how these contribute to the articulation of national identity. The article takes a case study of Twitter accounts of current highest political representatives of the United States and Canada, Donald Trump and Justin Trudeau, respectively. Drawing methodologically mainly on Teun van Dijk's ideological square (1998), it aims to show that national and political agendas are often intertwined and inherently connected. The findings suggest, however, that, even though the techniques are often similar, the extent and purpose of their employment varies. [ABSTRACT FROM AUTHOR]

We investigate the temperature dependence of the helical pitch of a cholesteric liquid crystal by means of Monte Carlo simulations. We carry out both lattice and off-lattice simulations to assess the impact of geometric and modelling constraints on the properties of the cholesteric phase. For the off-lattice simulations we develop boundary conditions commensurate with the cholesteric phase and derive an analytic expression for the helical wavenumber q that works well qualitatively. We find that the common simplification of constraining the orientation of the mesogens to planes normal to the helical axis makes q temperature-independent, as predicted by a mean-field theory of van der Meer et al. [J. Chem. Phys. 65 , 3935 (1976)]. However, if mesogens are allowed to rotate in three dimensions, q will increase with temperature, as the isotropic-cholesteric transition is approached from below, in agreement with experiments for a number of substances. Our simulations indicate that the temperature-independent q is merely a consequence of the overly restricted orientational degrees of freedom to points on the unit circle in the model on which the mean-field theory is based. [ABSTRACT FROM AUTHOR]

The ice microstructure in the lower part of the North Greenland Eemian Ice Drilling (NEEM) ice core consists of relatively fine-grained ice with a single maximum crystallographic preferred orientation (CPO) alternated by much coarser-grained ice with a partial (great circle) girdle or multi-maxima CPO. In this study, the grain-size-sensitive (GSS) composite flow law of Goldsby and Kohlstedt (2001) was used to study the effects of grain size and premelting (liquid-like layer along the grain boundaries) on strain rate in the lower part of the NEEM ice core. The results show that the strain rates predicted in the fine-grained layers are about an order of magnitude higher than in the much coarser-grained layers. The dominant deformation mechanisms, based on the flow relation of Goldsby and Kohlstedt (2001), between the layers is also different, with basal slip rate limited by grain boundary sliding (GBS-limited creep) being the dominant deformation mechanism in the finer-grained layers, while GBS-limited creep and dislocation creep (basal slip rate limited by non-basal slip) contribute both roughly equally to bulk strain in the coarse-grained layers. Due to the large difference in microstructure between finer-grained ice and the coarse-grained ice at premelting temperatures (T>262 K), it is expected that the fine-grained layers deform at high strain rates, while the coarse-grained layers are relatively stagnant. The difference in microstructure, and consequently in viscosity, between impurity-rich and low-impurity ice can have important consequences for ice dynamics close to the bedrock. [ABSTRACT FROM AUTHOR]

Anisotropic fluids (e.g. liquid crystals) offer a remarkable promise as optofluidic materials owing to the directional, tunable, and coupled interactions between the material, flow, and the optical fields. Here we present a comprehensive in silico treatment of this anisotropic interaction by performing nonequilibrium molecular dynamics simulations. We quantify the response of a nematic liquid crystal (NLC) undergoing a Poiseuille flow in the Stokes regime, while being illuminated by a laser beam incident perpendicular to the flow direction. We adopt a minimalistic model to capture the interactions, accounting for two features: first, the laser heats up the NLC locally; and second, the laser polarises the NLC and exerts an optical torque that tends to reorient molecules of the nematic phase. Because of this reorientation the liquid crystal exhibits small regions of biaxiality, where the nematic director is one symmetry axis and the axis of rotation for the reorientation of the molecules is the other one. We find that the relative strength of the viscous and the optical torques mediates the flow-induced response of the biaxial regions, thereby tuning the emergence, shape and location of the regions of enhanced biaxiality. The mechanistic framework presented here promises experimentally tractable routes toward novel optofluidic applications based on material-flow-light interactions. [ABSTRACT FROM AUTHOR]

The article focuses on the attitudes of two militant Islamist groups, Al Qaeda and the Islamic State, toward the issue of terrorist attacks in the energy sector. The main aim of the article is both to analyze the importance of attacks on energy infrastructure for the strategies of these two organizations, and to describe specific examples and manifestations of terrorist activities from the side of Al Qaeda and the Islamic State with regard to the energy sector in the Middle East and North Africa. The article is based on the concept of terrorist attacks on the energy sector. [ABSTRACT FROM AUTHOR]

Impurities control a variety of physical properties of polar ice. Their impact can be observed at all scales – from the microstructure (e.g., grain size and orientation) to the ice sheet flow behavior (e.g., borehole tilting and closure). Most impurities in ice form micrometer-sized inclusions. It has been suggested that these μ inclusions control the grain size of polycrystalline ice by pinning of grain boundaries (Zener pinning), which should be reflected in their distribution with respect to the grain boundary network. We used an optical microscope to generate high-resolution large-scale maps (3 μm pix-1, 8 × 2 cm2) of the distribution of micro-inclusions in four polar ice samples: two from Antarctica (EDML, MIS 5.5) and two from Greenland (NEEM, Holocene). The in situ positions of more than 5000 μ inclusions have been determined. A Raman microscope was used to confirm the extrinsic nature of a sample proportion of the mapped inclusions. A superposition of the 2-D grain boundary network and μ-inclusion distributions shows no significant correlations between grain boundaries and μ inclusions. In particular, no signs of grain boundaries harvesting μ inclusions could be found and no evidence of μ inclusions inhibiting grain boundary migration by slow-mode pinning could be detected. Consequences for our understanding of the impurity effect on ice microstructure and rheology are discussed. [ABSTRACT FROM AUTHOR]

This study describes an analytical evaluation of the quality factor QZ in a separable system in which the vector potential is known. The proposed method uses a potential definition of active and reactive power, implicitly avoiding infinite entire space integration and extraction of radiation energy. As a result, all the used quantities are finite, and the calculated QZ is always non-negative function of frequency. The theory is presented on the canonical example of the currents flowing on a spherical shell. The QZ for the dominant spherical transverse magnetic and transverse electric modes and their linear combination are found in closed forms, including both internal and external energies. The proposed analytical method and its results are compared with previously published limits of the quality factor Q. [ABSTRACT FROM AUTHOR]

This study describes an effective technique for calculating modal radiation efficiency calculation based on decomposition into characteristic modes. The key assumption is that the current distribution on the perfect electric conductor is almost the same as in the case of a very good conductor, for example, metals such as copper, aluminium and silver. This assumption is verified against the conventional technique, the impedance boundary condition (IBC). The proposed approach does not require any modification of the formulation of method of moments for perfectly conducting surfaces, which is assumed for the modal decomposition. Modal efficiencies provide an additional insight that is useful especially for the design of small antennas. Taking the feeding into account, the modal losses can be summed up to obtain the total efficiency. The technique works perfectly for common metals, is fully comparable with the IBC, and can easily be incorporated into any present-day in-house solver. A numerical analysis of three antennas is presented to demonstrate the merits of the approach. Radiation efficiency of coupled dipoles, an electrically small meandered dipole, and PIFA were investigated by the presented method. The results are in perfect agreement with the reference commercial package. [ABSTRACT FROM AUTHOR]

In 2010 a reflection seismic survey was carried out on the Alpine glacier Colle Gnifetti. The processed and depth-converted data could be compared to a nearby ice core, drilled almost to the bed. Comparisons showed that the depth of the P-wave bed reflection was too shallow, while the depth of the SH-wave bed reflection fitted the ice-core length well. We are now able to explain the major part of these differences using the existing crystal orientations of the ice at Colle Gnifetti. We calculate anisotropic velocities for P- and SH-waves that are usually picked for stacking and compare them with zero-offset velocities needed for the depth conversion. Here we take the firn pack at Colle Gnifetti into account for P- and S-wave analysis. To incorporate the S-wave analysis we first derive a new equation for the relationship between density and S-wave velocity from diving waves. We show that anisotropic fabrics observed at Colle Gnifetti introduce a difference of only 1% between stacking and depthconversion velocities for the SH-wave, but 7% for the P-wave. We suggest that this difference in stacking and depth-conversion velocity for the P-wave can be used to derive information about the existing anisotropy by combining our seismic data with, for example, radar data. [ABSTRACT FROM AUTHOR]

This paper deals with practical aspects of mesh generation for the theory of characteristic modes. First, we describe a tool for surface-mesh generation in MATLAB. The tool is afterwards used for an analysis of relative convergence of modal results computed by an in-house modal analyzer in MATLAB. Different meshing scenarios are selected for a dipole, a rectangular patch, and a rectangular patch with a slot, and a recommendation for a mesh-refinement strategy is given. The study is supported by a simple error analysis, considering the approximation error in the evaluation of moment-matrix elements. It is shown that the results are also applicable for the commercial implementation in FEKO software. [ABSTRACT FROM AUTHOR]

New expressions are derived to calculate the Q factor of a radiating device. The resulting relations link Q based on the frequency change of the input impedance at the input port (Q_X, Q_Z) with expressions based solely on the current distribution on an radiating device. The question of which energies of a radiating system are observable is reviewed, and then the proposed Q factor as defined in this paper is physical. The derivation is based on potential theory rather than fields. This approach hence automatically eliminates all divergent integrals associated with electromagnetic energies in infinite space. The new formulas allow us to study the radiation Q factor for antennas without feeding (through e.g., characteristic modes) as well as fed by an arbitrary number of ports. The new technique can easily be implemented in any numerical software dealing with current densities. To present the merits of proposed technique, three canonical antennas are studied. Numerical examples show excellent agreement between the measurable Q_Z derived from input impedance and the new expressions. [ABSTRACT FROM AUTHOR]

The article focuses on Central and Eastern European (CEE) countries' experiences related to Afghanistan, Iraq and Libya, three non-European theatres of Western military operations, in predominantly Muslim lands, in the decade between 2001 and 2011. CEE countries readily became involved in two of these foreign missions (Afghanistan and Iraq) because of their deep ties to Western politico-economic structures, without direct security interests compelling them to do so, but not without normative convictions regarding what were seen by them as virtues of the two missions. In Libya, however, they were reluctant to join the Western intervention. In light of this, the article is interested in examining how political elites within the region relate to the generally constrained security policy agency that they have. A key argument advanced is that such agency may be located in how external hegemony is mediated in elite discourses of threat and legitimacy construction. This as well as the three case studies outlined in the article show that the seeming changes in CEE countries' behaviour in fact boil down to a simple set of rules guiding their behaviour. Having identified this "algorithm" as an implicit pattern of CEE foreign policy behaviour, originating in the intra-alliance security dilemma within the North Atlantic Treaty Organisation (NATO), the article formulates its conclusions about the alliance policy of these countries largely within a neorealist framework. [ABSTRACT FROM AUTHOR]

This paper describes the implementation of a complex MATLAB tool to calculate the characteristic modes and associated antenna parameters. The first code, written in FORTRAN, was presented in the early seventieths by Harrington and Mautz. Here, we utilize MATLAB, which is widely known and used in the antenna community these days. Because eigen-decomposition is time consuming, parallel and distributed computing is used. Thanks to the hundreds of built-in functions in MATLAB, computation of the surface currents from the eigenvectors obtained, as well as other important characteristics, are very easy and effective. The practical features are discussed with two examples. [ABSTRACT FROM AUTHOR]

A new formula for the evaluation of the modal radiation Q factor is derived. The total Q of selected structures is to be calculated from the set of eigenmodes with associated eigen-energies and eigen-powers. Thanks to the analytical expression of these quantities, the procedure is highly accurate, respecting arbitrary current densities flowing along the radiating device. The electric field integral equation, Delaunay triangulation, method of moments, Rao-Wilton-Glisson basis function and the theory of characteristic modes constitute the underlying theoretical background. In terms of the modal radiation Q, all necessary relations are presented and the essential points of implementation are discussed. Calculation of the modal energies and Q factors enable us to study the effect of the radiating shape separately to the feeding. This approach can be very helpful in antenna design. A few examples are given, including a thin-strip dipole, two coupled dipoles a bowtie antenna and an electrically small meander folded dipole. Results are compared with prior estimates and some observations are discussed. Good agreement is observed for different methods. [ABSTRACT FROM PUBLISHER]

This article investigates the performance of Poland and the Czech Republic in the US-led regime change wars in Iraq and Afghanistan. The article indicates a significant gap between the Czech and Polish discourses and practices related to the two countries' contributions. In the two crises, discourses revolved around the notion of universal values and support for legal and legitimate peace support operations mandated by the UN. But the practices did not match those discourses and were actually driven by the beliefs that form the Atlanticist ideology. The article analyses the successful internalization of US discourses and threat perception in Poland and the Czech Republic through the use of ‘cascade argumentation’. The practical results of this internalization are then examined. [ABSTRACT FROM PUBLISHER]

Copyright of Osteuropa is the property of Berliner Wissenschaftsverlag GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The chosen rectangular and fractal microstrip patch antennas above an infinite ground plane are analyzed by the theory of characteristic modes. The resonant frequencies and radiation Q are evaluated. A novel method by Vandenbosch for rigorous evaluation of the radiation Q is employed for modal currents on a Rao-Wilton-Glisson (RWG) mesh. It is found that the resonant frequency of a rectangular patch antenna with a dominant mode presents quite complicated behaviour including having a minimum at a specific height. Similarly, as predicted from the simple wire model, the radiation Q exhibits a minimum too. It is observed that the presence of out-of-phase currents flowing along the patch antenna leads to a significant increase of the Q factor. [ABSTRACT FROM AUTHOR]

This article is an empirical-theoretical mapping of the Czech participation in the peacebuilding reconstruction of Afghanistan in the form of the Czech Provincial Reconstruction Team (PRT). As will become clear, an important part of such a study is a focus on the analysis of the influence of the security context and external factors on the participation and form of the Czech PRT. The study is divided into two basic parts. The first part gives the reader a necessary and sensible grounding. Specifically, it presents a contextual frame for the participation of the North Atlantic Treaty Organization (NATO) in Afghanistan. What then follows is an analysis of the domestic political debate in the Czech Republic. One of the findings is that any proper domestic political debate was absent, instead there was a polarization of the relationship between the government of the Czech Republic and the parliamentary opposition on the issue of the Czech PRT Logar. The article concludes with a question concerning the motives of the Czech government for sending the Czech PRT into Afghanistan. [ABSTRACT FROM AUTHOR]

The security culture of the 43rd President of the USA is tested in the light of instrumental preferences, while the strategic culture is seen in the light of the measures and means used in the process of the realization of the political aims. The National Security Strategy 2002 and the decision to wage the second Iraqi War without a clear mandate of the UNSC and in spite of the negative attitude of many allies are symptoms of unilateralism and of a unique type of militarism; this militarism was generated not by the military, but by the politicians. In the military sphere, the Iraqi war was very well prepared and conducted. The article concludes that in 2001-2008, the USA failed in the field of the security culture, but it was successful in the field of the strategic culture. [ABSTRACT FROM AUTHOR]

This study deals with the issue of global terrorism. It begins with Beck's description of a pattern of behaviour which is in contradiction with the interests of civilisation. Next, it evaluates Bush's choice between two flows of social capital and his GWOT strategy from the perspective of Giddens' concept of norms and resources. The encounter between the 43rd U.S. president and the al-Qaida chief is explained as a duel between a patron and a broker. The study goes on to provide a comparison of the main actors' social networks and social capital from 9/11/2001 up to the present. In the end, the author juxtaposes the U.S. direct strategic culture and the crafty and insidious culture of al-Qaida and its allied movements. [ABSTRACT FROM AUTHOR]

Copyright of Osteuropa is the property of Berliner Wissenschaftsverlag GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Czech Journal of International Relations / Mezinárodní Vztahy is the property of Ustav Mezinarodnich Vztahu, v. v. i. (Institute of International Relations) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Closed-form equations are given for radiation quality factor of a thin-wire λ/2 dipole above an infinite electric ground plane. Particular results of interest include a simple formula for a small separation between the dipole and the ground and for one dipole in free space. [ABSTRACT FROM AUTHOR]

The section presents a reaction to the article "Reactive Energies, Impedance, and Q Factor of Radiating Structures," by G. Vandenbosch that was published in the April 2010 issue of "IEEE Transactions on Antennas and Propagation." Vandenbosch evaluated the radiated power and stored magnetic and electric energies in terms of the source currents flowing on the radiating device.

Microstructures from deep ice cores reflect the dynamic conditions of the drill location as well as the thermodynamic history of the drill site and catchment area in great detail. Ice core parameters (crystal lattice-preferred orientation (LPO), grain size, grain shape), mesostructures (visual stratigraphy) as well as borehole deformation were measured in a deep ice core drilled at Kohnen Station, Dronning Maud Land (DML), Antarctica. These observations are used to characterize the local dynamic setting and its rheological as well as microstructural effects at the EDML ice core drilling site (European Project for Ice Coring in Antarctica in DML). The results suggest a division of the core into five distinct sections, interpreted as the effects of changing deformation boundary conditions from triaxial deformation with horizontal extension to bedrock-parallel shear. Region 1 (uppermost approx. 450 m depth) with still small macroscopic strain is dominated by compression of bubbles and strong strain and recrystallization localization. Region 2 (approx. 450-1700 m depth) shows a girdle-type LPO with the girdle plane being perpendicular to grain elongations, which indicates triaxial deformation with dominating horizontal extension. In this region (approx. 1000 m depth), the first subtle traces of shear deformation are observed in the shape-preferred orientation (SPO) by inclination of the grain elongation. Region 3 (approx. 1700-2030 m depth) represents a transitional regime between triaxial deformation and dominance of shear, which becomes apparent in the progression of the girdle to a single maximum LPO and increasing obliqueness of grain elongations. The fully developed single maximum LPO in region 4 (approx. 2030-2385 m depth) is an indicator of shear dominance. Region 5 (below approx. 2385 m depth) is marked by signs of strong shear, such as strong SPO values of grain elongation and strong kink folding of visual layers. The details of structural observations are compared with results from a numerical ice sheet model (PISM, isotropic) for comparison of strain rate trends predicted from the large-scale geometry of the ice sheet and borehole logging data. This comparison confirms the segmentation into these depth regions and in turn provides a wider view of the ice sheet.This article is part of the themed issue 'Microdynamics of ice'., (© 2016 The Authors.)