A second-order global solution of the ideal resonance problem

The Ideal Resonance Problem, as formulated in 1966 (Paper I), is defined by the Hamiltonian Following the procedure adopted in the construction of a first-orderglobal solution (Papers II, III, and V), we derive a second-order solution from the von Zeipel-Bohlin recursive algorithm of Paper II. The singularities inherent in the Bohlin expansion in powers of μ have been suppressed by means of theregularizing function of Paper III, and the singularities in the coefficients atAB″=0 have been removed by thenormalization technique of Paper V. As a check, it is shown that the global solution includes asymptotically theclassical solution, expanded in powers ofμ ², and carrying thecritical divisor B′.     

The importance of population,climate change and CO2 plant physiological forcing in determining future global water stress

Future levels of water stress depend on changes in several key factors including population, climate-change driven water availability, and a carbon dioxide physiological-forcing effect on evaporation and run-off. In this study we use an ensemble of the HadCM3 climate model forced with a range of future emissions scenarios combined with a simple water scarcity index to assess the contribution of each of these factors to the projected population living in water stress over the 21st century.Population change only scenarios increase the number of people living in water stress such that at peak global population 65% of people experience some level of water stress. Globally, the climate model ensemble projects an increase in water availability which partially offsets some of the impacts of population growth. The result is 1 billion fewer people living in water stress by the 2080s under the high end emissions scenarios than if population increased in the absence of climate change.This study highlights the important role plant-physiological forcing has on future water resources. The effect of rising CO₂ is to increase available water and to reduce the number of people living in high water stress by around 200 million compared to climate only projections. This effect is of a similar order of magnitude to climate change.     

Last glacial–interglacial sea-ice cover in the SW Atlantic and its potential role in global deglaciation

Sea-ice growth and decay in Antarctica is one of the biggest seasonal changes on Earth, expanding ice cover from 4 × 10⁶ km² to a maximum of 19 × 10⁶ km² during the austral winter. Analyses of six marine sediment cores from the Scotia Sea, SW Atlantic, yield records of sea-ice migration across the basin since the Lateglacial. The cores span nearly ten degrees of latitude from the modern seasonal sea-ice zone to the modern Polar Front. Surface sediments in the cores comprise predominantly diatomaceous oozes and muddy diatom oozes that reflect Holocene conditions. The cores exhibit similar down-core stratigraphies with decreasing diatom concentrations and increasing magnetic susceptibility from modern through to the Last Glacial Maximum (LGM). Sediments in all cores contain sea-ice diatoms that preserve a signal of changing sea-ice cover and permit reconstruction of past sea-ice dynamics. The sea-ice records presented here are the first to document the position of both the summer and winter sea-ice cover at the Last Glacial Maximum (LGM) in the Scotia Sea. Comparison of the LGM and Holocene sea-ice conditions shows that the average winter sea-ice extent was at least 5° further north at the LGM. Average summer sea-ice extent was south of the most southerly core site at the LGM, and suggests that sea-ice expanded from approximately ～61°S to ～52°S each season. Our data also suggest that the average summer sea-ice position at the LGM was not the maximum extent of summer sea-ice during the last glacial. Instead, the sediments contain evidence of a pre-LGM maximum extent of summer sea-ice between ～30 ka and 22 ka that extended to ～59°S, close to the modern average winter sea-ice limit. Based on our reconstruction we propose that the timing of the maximum extent of summer sea-ice and subsequent retreat by 22 ka, could be insolation controlled and that the strong links between sea-ice and bottom water formation provide a potential mechanism by which Southern Hemisphere regional sea-ice dynamics at the LGM could have a global impact and promote deglaciation.     

Coupled HM analysis using zero‐thickness interface elements with double nodes. Part I: Theoretical model

In recent years, the authors have proposed a new double‐node zero‐thickness interface element for diffusion analysis via the finite element method (FEM) (Int. J. Numer. Anal. Meth. Geomech. 2004; 28 (9): 947–962). In the present paper, that formulation is combined with an existing mechanical formulation in order to obtain a fully coupled hydro‐mechanical (or HM) model applicable to fractured/fracturing geomaterials. Each element (continuum or interface) is formulated in terms of the displacements (u) and the fluid pressure (p) at the nodes. After assembly, a particular expression of the traditional ‘u–p’ system of coupled equations is obtained, which is highly non‐linear due to the strong dependence between the permeability and the aperture of discontinuities. The formulation is valid for both pre‐existing and developing discontinuities by using the appropriate constitutive model that relates effective stresses to relative displacements in the interface. The system of coupled equations is solved following two different numerical approaches: staggered and fully coupled. In the latter, the Newton–Raphson method is used, and it is shown that the Jacobian matrix becomes non‐symmetric due to the dependence of the discontinuity permeability on the aperture. In the part II companion paper (Int. J. Numer. Anal. Meth. Geomech. 2008; DOI: 10.1002/nag.730 ), the formulation proposed is verified and illustrated with some application examples. Copyright © 2008 John Wiley & Sons, Ltd.     

Downwelling and upwelling regimes: Connections between surface fronts and abyssal circulation

Recent observations in the Sea of Japan show evidence of convection to a depth of roughly 1000 m in the winter of 2000, situated along the polar front. Numerical simulations have shown that this deep mixing is associated with both ageostrophic frontal circulations and pre-existing larger-scale downwelling regimes. The downwelling regimes appear to be a result of interactions between frontal meandering and deep circulation in this basin over bottom topography anomalies. The coupling between the frontal dynamics and the deep circulation are explored by analogy to atmospheric frontal circulations through the semigeostrophic Sawyer–Eliassen equation, solved numerically for the case of the Sea of Japan. As in the atmospheric case, a vertical coupling between the upper and lower circulations can produce a localized region of downwelling that can be conducive to deeper mixing than that forced solely from surface fluxes.     

Aggregating dispersed workers: Union organizing in the “care” industries

This paper analyzes recent union efforts to organize low-wage workers in the home- and community-based segments of homecare, childcare, and services to people with developmental disabilities in the US. In these sectors, consumer demand has combined with privatization to create an army of “flexible”, part-time, poverty-wage workers, most of them women, people of color, and immigrants. This workforce is profoundly fragmented due to the preponderance of small nonprofit employers, widespread self-employment, and spatially atomized labor performed within myriad private homes. However, service sector unions have adapted creatively to these opportunities and constraints by implementing two interlinked scale-jumping strategies to overcome care workers’ spatial and organizational atomization. One is state-by-state policy advocacy to raise labor (and service) standards industry-wide and to aggregate employment through various organizational and legal interventions. The other is coalition building with consumers and advocates at the local, state, and national level to generate essential political support for these measures. We find that the success of this strategy has been shaped in large part by the political landscape of region and the political economy of distinct care industry segments. Finally, the resulting care industry unionism constitutes a distinct strand of an emergent public services unionism—in which consumers and workers struggle to define care labor as a socially necessary public good, and workers pushed into the nebulous zone between state and market struggle to define themselves as public workers.     

Salinization and arsenic contamination of surface water in southwest Bangladesh

To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012–2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0.15 ppt in the wet season up to ~20 ppt in the dry season. On the polder, surface water exceeds the World Health Organization drinking water guideline of 10 μg As/L in 78% of shrimp ponds and 27% of rice paddies, raising concerns that produced shrimp and rice could have unsafe levels of As. Drinking water sources also often have unsafe As levels, with 83% of tubewell and 43% of freshwater pond samples having >10 μg As/L. Water compositions and field observations are consistent with shrimp pond water being sourced from tidal channels during the dry season, rather than the locally saline groundwater from tubewells. Irrigation water for rice paddies is also obtained from the tidal channels, but during the wet season when surface waters are fresh. Salts become concentrated in irrigation water through evaporation, with average salinity increasing from 0.43 ppt in the tidal channel source to 0.91 ppt in the rice paddies. Our observations suggest that the practice of seasonally alternating rice and shrimp farming in a field has a negligible effect on rice paddy water salinity. Also, shrimp ponds do not significantly affect the salinity of adjacent surface water bodies or subjacent groundwater because impermeable shallow surface deposits of silt and clay mostly isolate surface water bodies from each other and from the shallow groundwater aquifer. Bivariate plots of conservative element concentrations show that all surface water types lie on mixing lines between dry season tidal channel water and rainwater, i.e., all are related by varying degrees of salinization. High As concentrations in dry season tidal channel water and shrimp ponds likely result from groundwater exfiltration and upstream irrigation in the dry season. Arsenic is transferred from tidal channels to rice paddies through irrigation. Including groundwater samples from the same area (Ayers et al. in Geochem Trans 17:1–22, 2016), principal components analysis and correlation analysis reveal that salinization explains most variation in surface water compositions, whereas progressive reduction of buried surface water by dissolved organic carbon is responsible for the nonconservative behavior of S, Fe, and As and changes in Eh and alkalinity of groundwater.     

Food commodities, geographical knowledges and the reconnection of production and consumption: The case of naturally embedded food products

This paper focuses on a particular group of food commodities, associated with the wider turn to ‘alternative food networks’, that are described as ‘naturally embedded food products’ (NEFPs). These are commodities (specifically meats and cheeses) that utilise grassland biodiversity as an input into production to positively influence, in various ways, the final qualities of the commodity. Building on the geographical literature on commodity circuits and analysing data derived from NEFP promotional materials and focus groups with urban and rural residents in the UK, the paper interrogates the geographical knowledges that are deployed by producers in the promotion of NEFPs and how these knowledges are accommodated and contested by consumers as they bring their own geographical knowledges to the interpretation of these commodities. The paper undertakes this task in order to problematise the extent to which alternative food networks in general and NEFPs in particular are bringing about a reconnection of producers and consumers and, concomitantly, a defetishisation of food, as is claimed for them by many of their policy and academic proponents. In the process the paper reveals how the food commodities associated with alternative food networks entail the creation of new and rival fetishes paradoxically as a result of efforts to ‘thicken connections’ between the production and consumption of food.     

Vulnerability of farm water supply systems to volcanic ash fall

Agriculture is critically dependent on continuity of water quality and quantity. It is well-established that even small quantities of volcanic ash can disrupt municipal water supplies, with known impacts to quality including: acidification, increases in turbidity and ionic concentrations. In addition, delivery systems may be blocked or damaged by hard and abrasive suspended ash and related ash-cleanup operations place extra stress on water reserves. The aim of this study was to characterise the key areas of vulnerability of farm water supplies to volcanic ashfall, and to identify management recommendations to reduce these. From literature review and case studies of farms impacted by the 1991 Pinatubo (Philippines) and 1991 Hudson (Chile) eruptions, key issues were: sedimentation of irrigation ditches and drinking water ponds, turbidity induced abrasion of sprinkler nozzles and water pumps, and damage to electric pumps (by ash on air-intakes). Building on this, we characterised the water-use regimes and water supply system vulnerability of eight case-study farms from across the North Island, New Zealand. From this, we propose an index system to evaluate the vulnerability of farm water supply systems. The key contributors to the vulnerability index include: water source, storage capacity, reliance on electricity, independence/interconnectedness of system elements, volume of water use and other load factors. These allow identification of key strategies for mitigating water supply vulnerability during prevention, preparation, response and recovery phases of a volcanic eruption.