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Coastal nature-based solution (NBS) projects have been on the rise over the past few years. In France, the expression is being increasingly used at a local level, and new projects are developing on the coast. However, they face various limitations, involving both technical challenges and social acceptability issues. Based on data from the perception survey conducted by the DIGUES research programme in the Authie Bay in 2021 and a numerical model used to assess the efficiency of flood protection measures developed as part of a flood action and prevention programme, this study aimed to highlight the gap between perceptions and misconceptions surrounding NBS-like scenarios and more objective modelling data. It offers a cross-comparison of these two datasets. For this purpose, the scenarios used to assess public perception in the DIGUES survey were translated in the numerical model to study the difference between perceived protection and actual protection in the Authie Bay, the opportunity for dyke relocation in an NBS scenario, and the effectiveness of the NBSs according to their scale. Overall, these results demonstrated a real benefit for implementing dyke relocation through breaches, compared to other scenarios for the Authie Bay.
The influence of compressibility on shear flow turbulence is investigated within a self-preservation framework. This study focuses on the axisymmetric jet to examine compressibility effects in a slowly spatially evolving flow, unlike mixing layers, where the convective Mach number remains constant. Revisiting self-preservation, an a priori description of the compressible scaling for Reynolds stresses and higher-order velocity moments is developed. Turbulence moments are found to scale with powers of the spreading rate, suggesting Reynolds stress anisotropy results from compressibility effects consistent with self-preservation of the governing equations. Particle image velocimetry measurements for Mach 0.3 and perfectly expanded Mach 1.25 jets confirm the scaling predictions. The attenuation function, $\varPhi (M_c)$, describing the relationship between the convective Mach number, $M_c$, and the spreading rate, follows a similar trend in jets and mixing layers, where a higher $M_c$ results in reduced spreading rates. In the jet where $M_c$ decays, the relationship between the local $M_c$ and turbulence attenuation remains captured through $\varPhi (M_c)$, which scales proportionally with the spreading rate. A new scale is introduced, where the pressure in the mean momentum equation is substituted. The difference between the streamwise and radial-Reynolds-normal stresses was found to be a scale which is independent of Mach number and spreading rate. Further analysis of the Reynolds-stress-transport budget shows that internal redistribution of energy occurs within the Reynolds-normal stresses, and the role of pressure modification in turbulence attenuation supports previous observations. These findings confirm that the compressible axisymmetric jet exhibits self-preservation, with scaling extending into supersonic regimes.
Flame–flame interactions in continuous combustion systems can induce a range of nonlinear dynamical behaviours, particularly in the thermoacoustic context. This study examines the mutual coupling and synchronisation dynamics of two thermoacoustic oscillators in a model gas-turbine combustor operating within a stochastic environment and subjected to external sinusoidal forcing. Experimental observations from two flames in an annular combustor reveal the emergence of dissimilar limit cycles, indicating localised lock-in of thermoacoustic oscillators. To interpret these dynamics, we introduce a coupled stochastic oscillator model with sinusoidal forcing terms, which highlights the critical role of individual synchronisation in enabling local lock-in. Furthermore, through stochastic system identification using this phenomenological low-order model, we mathematically demonstrate that a transition towards self-sustained oscillations can be driven solely by enhanced mutual coupling under external forcing. This combined experimental and modelling effort offers a novel framework for characterising complex coupled flame dynamics in practical combustion systems.
Glacial lakes in the Himalayas have expanded significantly in recent decades, increasing the potential risk of outburst floods. However, limited field surveys and systematic assessments leave downstream communities vulnerable. Accurate volume estimation of glacial lakes is essential for modelling flood dynamics, yet in-situ bathymetric data remain scarce. In this study, we surveyed four glacial lakes—Kya Tso Lake, Panchi Nala Lake, Gepang Gath Lake and Samudra Tapu Lake—in the Chandrabhaga basin, western Himalayas. Depth measurements were conducted using a portable inflatable kayak in August 2022 and an echo sounder mounted on an uncrewed surface vehicle in August 2024. Bathymetric modelling revealed maximum depths of 16 m, 10 m, 46 m, and 59 m, with corresponding storage capacities of 0.89, 0.44, 24.12, and 24.69 × 10⁶ m3, respectively. Volume estimates derived from empirical equations showed substantial discrepancies of ± 36–1736% compared to in-situ measurements. Despite several operational challenges, this study provides valuable in-situ bathymetric data for future modelling and hazard assessment of rapidly expanding glacial lakes in the region. The findings emphasise the need for robust field-based bathymetric datasets to refine empirical volume estimation models for Himalayan glacial lakes.
Greenland’s peripheral glaciers and ice caps contribute disproportionately to sea-level rise relative to their small area. Winter snow accumulation directly influences glacier mass balance and downstream hydrology, but spatially extensive observations of this important mass balance component remain sparse. In this study, we present a unique multi-year (2008–2024) dataset of winter snow accumulation over A.P. Olsen Ice Cap, Northeast Greenland, from ground-penetrating radar surveys covering an average of 47 km per survey year. Our results reveal strong spatial heterogeneity that is likely influenced by wind redistribution and local topography, especially in the ablation zone. We compare our findings with automatic weather station data from three sites and outputs from the Copernicus Arctic Regional Reanalysis (CARRA). Governed by the high spatial variability, the automatic weather station point-based observations significantly underestimate regional accumulation by 40–45%. Despite the high spatial variability, the CARRA accumulated precipitation variable provides a reasonable overall mean winter snow accumulation (RMSE of 0.07 m w.e.); however, it fails to reproduce the complex non-linear relationship between snow depth and elevation observed in the radar data. Our findings emphasize the need for high-resolution, spatially extensive measurements to better understand snow accumulation on ice caps and glaciers and improve reanalysis assessments.
Wastewater treatment is critically important and ceramic-membrane engineering is one of the most effective technologies for water filtration and purification. However, the materials used in the preparation of ceramic membranes are usually expensive, e.g. ZrO and Al2O3 membranes, reverse osmosis materials such as carbon-based thin-film nanocomposite TFNC ‘carbon nanotube, graphene-oxide’. Delicate, thin membranes employed for small-scale filtration usually require optimal supports for effective operation. The purpose of the present research, therefore, was to find a less expensive material for membrane supports while, at the same time, enhancing performance. Membrane supports were thus prepared from local clay materials and (25 wt.%) CaCO3 using an extrusion technique, which enabled the production of tubular supports. The CaCO3 is responsible for creating the pores in the samples during heat treatment due to the evolution of CO2 gas. Some characteristics of the supports were evaluated using X-ray diffraction, which identified quartz, gehlenite, sillimanite, H-bearing aluminous stishovite, and wollastonite. The support treated at 1000°C displayed significant mechanical properties (flexural strength, 11.58 MPa, measured using three-point bending tests) compared with supports treated at other temperatures. Moreover, the support sintered at 1000°C had an estimated permeability factor of 1052 L/h m2.bar after performing both time- and pressure-dependent flux measurements. Such properties make it possible to use these supports as multi-scale filtration membranes for purification and filtration applications after performing a standard filtration application on dirty water, resulting in a significant difference in terms of turbidity and waste content.
It is often inferred that rising sea levels will result in widespread coastal recession. Erosion appeared prevalent in a worldwide compilation of evidence derived from maps and aerial photographs undertaken in the 1980s by the Commission on the Coastal Environment. Eric Bird, chair of the commission, inferred that >70% of sandy coastlines had retreated, a generalisation that has been widely cited. We reconsider these findings in respect of subsequent advances in shoreline mapping, including greater precision possible using geographical information systems and more frequent remote sensing imagery with increased spatial, spectral and temporal resolution. Satellite-derived shorelines now enable broad global and regional generalisations about shoreline position. Beaches fluctuate over a range of timescales, meaning that trends in their position are highly dependent on techniques and temporal scales adopted for monitoring. Recent global- and regional-scale shoreline assessments indicate that many sandy shorelines have been stable, and that detectable retreat has occurred on fewer beaches than previously inferred. Accretion is apparent on some coasts, particularly where engineering interventions protect or have reclaimed land. There is considerable variability in the behaviour of monitored beaches, and it is not yet possible to decipher a response to the gradual centimetre-scale rise in sea level of recent decades. Instead, we re-emphasise the several other factors that were considered to contribute to recession by the Commission, many of which relate to a change in sediment budget. To provide insights into future coastline behaviour, a better understanding of the multiple drivers on individual beaches is needed to discriminate between erosional events and longer-term trends in shoreline position.
A wall-modelled large eddy simulation approach is proposed in a discontinuous Galerkin (DG) setting, building on the slip-wall concept of Bae et al. (J. Fluid Mech., vol. 859, 2019, pp. 400–432) and the universal scaling relationship by Pradhan and Duraisamy (J. Fluid Mech., vol. 955, 2023, A6). The effect of the order of the DG approximation is introduced via the length scales in the formulation. The level of under-resolution is represented by a slip Reynolds number and the model attempts to incorporate the effects of the numerical discretization and the subgrid-scale model. The dynamic part of the new model is based on a modified form of the Germano identity -- performed on the universal scaling parameter -- and is coupled with the dynamic Smagorinsky model. A sharp modal cutoff filter is used as the test filter for the dynamic procedure, and the dynamic model can be easily integrated into any DG solver. Numerical experiments on channel flows show that grid independence of the statistics is achievable and predictions for the mean velocity and Reynolds stress profiles agree well with the direct numerical simulation, even with significant under-resolution. When applied to flows with separation and reattachment, the model also consistently predicts one-point statistics in the reverse flow and post-reattachment regions in good agreement with experiments. The performance of the model in accurately predicting equilibrium and separated flows using significantly under-resolved meshes can be attributed to several aspects that work synergistically: the optimal finite-element projection framework, the interplay of the scale separation and numerical discretization within the DG framework, and the consistent dynamic procedures for subgrid and wall modelling.
The European Green Deal (EGD) provides a strategic framework for the European Union’s (EU) transition to climate neutrality by 2050. Yet, limited integration of socio-economic dimensions may hinder its long-term success and fairness. This study investigates the indirect impacts of socio-economic factors on EGD performance by constructing a Green Deal Performance Index (GDPI) using a multi-criteria decision-making approach for 22 EU countries over 2010–2020. We then apply an instrumental variable regression approach to estimate how emissions, shaped by structural socio-economic conditions, affect the GDPI. Our results show that the negative impact of emissions is nearly 47 times larger when socio-economic dynamics are ignored. These findings underscore the necessity of inclusive policymaking for achieving carbon neutrality, contributing to discussions on ensuring a just transition by highlighting the critical role of socio-economic dynamics. We also present implications for policymakers developing fair and equitable strategies promoting sustainability and social justice in this context.
Financial flows and financial structures are fueling climate instability and worsening inequities around the world. A stable future now requires urgent change including transformative financial innovations. Yet the pandemic and recent financial disruptions reveal how financial architecture designed to promote stability in times of crises exacerbates economic inequities and vulnerabilities. Recognizing the division in climate politics among those advocating for stable policies and a smooth transition and those calling for more radical, disruptive politics, this chapter reviews the critical role of financial innovations, including central banks’ monetary policies, in redirecting society toward a more just and stable future. We propose a paradigm shift to reconceptualize stability and politicization in finance and central banking for climate justice. We argue that current depoliticized perspectives on financial stability are worsening climate instability, and that finance, central banks, and their monetary policies are an underappreciated part of climate politics. Transformative climate policy to promote stability requires repoliticizing finance and financial innovations.
California is often seen as a homogeneous entity that uniformly values environmentalism and climate action. This image universalizes the idea of climate change and detaches it from its cultural and political settings. It also obscures how the localization of environmental policy and science within the state involves processes of public contestation and legitimation. This chapter examines the culturally contingent nature of climate policy – the assumptions and worldviews that often create conflict between community understandings of local environmental conditions and the prevailing global regulatory culture of climate change. I argue that through a reoccurring process of conflict and collaboration, a broad range of individuals and organizations is co-constituting what climate change and environmental justice mean. California’s climate change programs are fostered by certain conditions of privilege – a robust economy, racial and ethnic plurality, and progressive statewide leaders. Nonetheless, they offer clear models of how to broaden climate change worldviews and imagine various relationships among the atmosphere, economic and racial disparities, and climate change policy.
FFramework climate laws have been enacted across a growing range of countries, and are often assumed to provide stability in terms of climate policymaking. This chapter provides a more nuanced assessment. I argue that, while some common design elements of framework climate laws do indeed serve to bring stability to climate policymaking, in many respects framework climate laws depart from the ideal design type envisioned by the literature on time inconsistency, commitment devices, and non-majoritarian institutions. Moreover, framework climate laws can actually serve to make explicit political conflicts and sectoral trade-offs, and can thus serve to politicize even as they depoliticize. Furthermore, by seeking to introduce stability to climate policymaking in the sense of stability in policy design over time, framework climate laws simultaneously and deliberately seek to undermine and challenge stability as status quo. The chapter draws on examples of framework climate laws principally in European countries to illustrate the argument.
Climate activists are divided over whether to adopt strategies emphasizing stability and incremental change versus strategies promoting more extreme and immediate action. One way to promote policy stability is through private governance, that is, voluntary industry self-governance. Proponents argue this can stabilize expectations about the future, incentivize incremental reductions in emissions, and lock in policies and practices. This problem-solving approach serves to depoliticize debate but can lead to political backlash and repoliticization. I examine these dynamics through a case study of the financial sector, particularly the insurance industry. Collective attempts to ensure policy lock-in and stability include initiatives such as the United Nations Environment Programme Finance Initiative (UNEP-FI), the Glasgow Financial Alliance for Net Zero, and Net Zero Insurance Alliance. This is a case of failed depoliticization as demonstrated by the political backlash against these efforts.
The conclusion draws together the findings of the book’s fifteen analytical chapters and is divided into six sections. Each section places several individual chapters in conversation with one another. First, we reflect on how the authors engaged with stability, across the four forms we developed in the introductory chapter, before the second section does the same regarding re/politicization. Third, we engage with the running theme throughout the book that stability and re/politicization are not dichotomous but rather interact, and indeed, one can be pursued to achieve the other. Fourth, we explore manifestations of depoliticization encountered within the book and find that, in practice, many regimes pursuing stability are less depoliticized than often assumed. Fifth, we bring in the importance of temporality to our studies, before finally offering concluding remarks on the book’s arguments and suggesting avenues for future research. Throughout the volume, we have presented the antagonism between stability and re/politicization in a deliberately flexible manner, and we hope others will find it – as well as our four novel forms of each approach – to be useful in their own analyses.