Deglaciation and proglacial lakes

Glaciers and ice sheets are important constituents of the Earth's land surface. Current worldwide retreat of glaciers has implications for the environment and for civilisation. There are a range of geomorphic changes occurring in cold environments and it is anticipated that these will be accentuated as a consequence of climate change. In particular, the number and size of proglacial lakes is currently increasing as a result of deglaciation and their significance for the physical environment and for society is becoming increasingly apparent. This article provides an overview of the major interdependent relationships between climate change, glaciers and proglacial lake development. In particular, it describes the key processes and impacts associated with proglacial lake evolution with reference to examples drawn from the European Alps, North America, the Himalayas, the Andes, Greenland, New Zealand and Iceland.     

Ejection behavior characteristics in experimental cratering in sandstone targets

Abstract– Within the frame of the MEMIN research unit (Multidisciplinary Experimental and Numerical Impact Research Network), impact experiments on sandstone targets were carried out to systematically study the influence of projectile mass, velocity, and target water saturation on the cratering and ejection processes. The projectiles were accelerated with two‐stage light‐gas guns (Ernst‐Mach‐Institute) onto fine‐grained targets (Seeberger sandstone) with about 23% porosity. Collection of the ejecta on custom‐designed catchers allowed determination of particle shape, size distribution, ejection angle, and microstructures. Mapping of the ejecta imprints on the catcher surface enabled linking of the different patterns to ejection stages observed on high‐speed videos. The increase in projectile mass from 0.067 to 7.1 g correlates with an increase in the total ejected mass; ejecta angles, however, are similar in range for all experiments. The increase in projectile velocity from 2.5 to 5.1 km s^?1 correlates with a total ejecta mass increase as well as in an increase in comminution efficiency, and a widening of the ejecta cone. A higher degree of water saturation of the target yields an increase in total ejecta mass up to 400% with respect to dry targets, higher ejecta velocity, and a steeper cone. These data, in turn, suggest that the reduced impedance contrast between the quartz grains of the target and the pores plays a primary role in the ejecta mass increase, while vaporization of water determines the ejecta behavior concerning ejecta velocity and particle distribution.     

Secular variations in seawater chemistry controlling dolomitization in shallow reflux systems: insights from reactive transport modelling

Dolomitization often plays a critical role in the pore network development of platform carbonates, with implications for reservoir quality distribution. Understanding both the hydrological system driving dolomitization and the chemistry of the fluids involved is fundamental to constrain predictions of the geometry and the petrophysical properties of dolomite bodies. Here, the role of secular variations in seawater Mg/Ca as a control on dolomitization and early porosity modification was evaluated using one‐dimensional reactive transport models and fluids based on modern (aragonite sea), Mississippian and Aptian (calcite sea) seawaters. The sensitivity of dolomitization to a range of extrinsic controls (brine salinity, temperature, fluid flow rate and pCO₂) and to intrinsic reactivity of the sediments (effective reactive surface area) was also explored. Simulations suggest faster calcite replacement by dolomite for seawaters with higher Mg/Ca, indicating that dolomitization potential is determined more by Mg/Ca rather than saturation index. Increasing evaporative concentration enhances reaction rate independent of the effect of enhanced density‐driven fluid flux. In addition to brine composition, effective surface area of precursor sediments and temperature exert a critical control on replacement rate, while secular variations of pH and carbonate alkalinity associated with changes in pCO₂ are only secondary controls. Above flow rates of 0·01 m yr^?1 replacive dolomitization is reaction‐limited rather than flux limited, favouring alteration of fine‐grained carbonates and suggesting that preferential alteration of grainstone units is rare unless head gradients are low. Post‐replacement dolomite cementation is flux dependent, and thus favoured in areas of high head gradient and high permeability sediments and, contrary to replacement, supersaturation is a more important driver than Mg/Ca. While uncertainties remain regarding low‐temperature dolomitization kinetics, the capability of numerical simulations to decouple individual controls provides new insights which can be used, in conjunction with traditional comparative sedimentology, to generate more rigorous conceptual models for individual reservoir settings.     

A new deal for lone parents? Training lone parents for work in West London

In this paper we explore the impacts of the training programmes offered to lone mothers with young children on the Government's 'New Deal for Lone Parents' in one local labour market: West London. Our research suggests that regulatory workfare policies are (re)producing and reinforcing gendered inequalities in the labour market by encouraging lone mothers to undertake training in feminised occupational areas such as childcare. We will argue that in a local economy such as West London where more childcare workers are desperately needed to enable other more highly skilled workers to take up employment opportunities, such training programmes may be doing little more than exacerbating the already gendered and class-based polarisation of the labour market – embedding low-skilled, poorly qualified lone mothers into low-paid jobs.     

Commodifying the countryside: the impact of out-of-school care on rural landscapes of children's play

The growing interest in rural geography has highlighted that symbolic representations of the 'rural idyll' are often contradictory to the lived experiences of many rural children. Increasingly, children's spatial mobility is restricted due to adult concerns over children's use of public space, and the continuing privatization of rural space. Whilst children are prevented from using the countryside as a resource, there is also a lack of provision and spaces dedicated to children's play. One exception to this is the development of out-of-school care schemes. The rapidly expandingout-of-school care service is providing rural children with a significant, well-resourced place for children to play. This paperexamines children's experiences of playing in the countryside, and discusses the impact of the developing out-of-school care service on the daily lives of children who experience the service. The paper also considers the impact of commodifying children's play on the ability of all children to access a local play service.     

A multi‐dimensional analysis of pro‐glacial landscape change at Sólheimajökull,southern Iceland

Pro‐glacial landscapes are some of the most active on Earth. Previous studies of pro‐glacial landscape change have often been restricted to considering either sedimentological, geomorphological or topographic parameters in isolation and are often mono‐dimensional. This study utilized field surveys and digital elevation model (DEM) analyses to quantify planform, elevation and volumetric pro‐glacial landscape change at Sólheimajökull in southern Iceland for multiple time periods spanning from 1960 to 2010. As expected, the most intense geomorphological changes persistently occurred in the ice‐proximal area. During 1960 to 1996 the pro‐glacial river was relatively stable. However, after 2001 braiding intensity was higher, channel slope shallower and there was a shift from overall incision to aggradation. Attributing these pro‐glacial river channel changes to the 1999 jökulhlaup is ambiguous because it coincided with a switch from a period of glacier advance to that of glacier retreat. Furthermore, glacier retreat (of ~40 m yr^?1) coincided with ice‐marginal lake development and these two factors have both altered the pro‐glacial river channel head elevation. From 2001 to 2010 progressive increase in channel braiding and progressive downstream incision occurred; these together probably reflecting stream power due to increased glacier ablation and reduced sediment supply due to trapping of sediment by the developing ice‐marginal lake. Overall, this study highlights rapid spatiotemporal pro‐glacial landscape reactions to changes in glacial meltwater runoff regimes, glacier terminus position, sediment supply and episodic events such as jökuhlaups. Recognizing the interplay of these controlling factors on pro‐glacial landscapes will be important for understanding the geological record and for landscape stability assessments. Copyright © 2014 John Wiley & Sons, Ltd.     

‘Body training’: Investigating the embodied training choices of/for mothers in West London

Framed by the UK Government’s efforts to combat social exclusion by encouraging a shift from welfare to work through (re)training, this paper explores the types of training courses being offered to and taken by women with young children in West London. Drawing upon qualitative research, the paper explores the actual and desired uptake of ‘body training’ courses among mothers, linked, in part, to the current ‘body work’ skills gap in the local economy. The encouragement given to women and the interest they have in engaging in ‘body training’ is, we suggest, linked to the discursive construction and performance of a highly feminised and, often, maternal identity, which emphasises women’s caring role and the caring self. By probing the body/training nexus through the motivations and choices of mothers in West London the paper raises questions about gender identity and stereotyping in relation to training-for-work policies and the role of training in (re)inforcing the woman-body coupling within Western dualistic thought.