Limits on the effect of pressure on isotopic fractionation

The equilibrium distribution of oxygen isotopes between calcium carbonate and water was determined at 500°C at pressures from 1 to 20 kbar and at 700°C at pressures of 0.5 and 1 kbar. At both temperatures, the pressure-dependence of the fractionation factor was below the limit of detection. The experimental results are consistent with theoretical estimates of the volume change due to isotope substitution. Application of the theory to silicate systems leads to the conclusion that pressure effects on oxygen isotopic fractionation between silicates are < 0.2% at pressures of tens of kilobars. Thus the observed large variations of O¹⁸/O¹⁶ ratio in kimberlitic eclogites cannot be attributed to the effect of pressure     

Extreme wave events and sampling variability

Ocean Dynamics - Wave field data are affected not only by the accuracy of instruments recording them but also by sampling variability, an uncertainty due to the limited number of observations. For...     

Using Multiple Methods to Understand the Nature of Relationships in Social Networks

Effective natural resource management (NRM) often depends on collaboration through formal and informal relationships. Social network analysis (SNA) provides a framework for studying social relationships; however, a deeper understanding of the nature of these relationships is often missing. By integrating multiple analytical methods (including SNA, evidence ratings, and perception matrices), we were able to investigate the nature of relationships in NRM social networks across five service types (e.g., technical advice, on-ground support) in our case study region, Daly catchment Australia. Only one service type was rated as highly associated with free choice in establishing relationships: technical advice/knowledge. Beneficial characteristics of NRM organizations, such as collaborative and transparent, were associated with the presence of freely chosen relationships between organizations. Our results suggest a need to improve our understanding of organizational roles and characteristics, in particular for use in applied NRM contexts, such as network weaving or disseminating information.     

The impacts of a Laki-like eruption on the present Swedish society

In this study, we analyse and discuss the possible impacts on the Swedish society of a volcanic eruption on Iceland, emitting ash particles and large quantities of sulphur dioxide. A scenario was developed, based on the historical Laki eruption of 1783–1784, to describe the content of a potential sulphur fog over time in Sweden. Due to its high complexity and the many uncertainties in the underpinning scientific data, the scenario was developed using a cross-disciplinary approach incorporating experts from different scientific fields. An analysis of the impacts of the hazard on human health, environment and technical equipment was then performed and, finally, representatives from national authorities assessed the overall societal challenges in responding to the consequences of a massive volcanic eruption. The analysis shows that it is the peak concentrations of sulphur dioxide and sulphuric acid rather than the longer periods of moderate concentrations that contribute most to the negative consequences for human health and environment. Altogether, three societal challenges were identified: the ability to compile and disseminate relevant information fast enough, to perform continuous measurements of concentrations of different substances in affected areas and to meet the large demand for medical care.     

Economics of climate policy and collective decision making

This paper explores the reasons why economic instruments of climate change are reluctantly applied and stresses the need for interdisciplinary research linking economic theory and empirical testing to deliberative political procedures. It is divided in three parts. The first one recalls the main issues in implementing Cost-Benefit Analysis such as information problems, uncertainties, discounting the future and irreversibilities. The second part shows how these issues can be treated in integrated assessment and techno-economic models and presents a case study, which shows that

• The chosen scenario tends to stabilize atmospheric CO₂ concentration at around 550 ppm in the long run.
• Exclusion of possibility to trade CO₂ emission permits under a cap regime would increase the cost of emission abatement for OECD countries.
• Combining different flexibility instruments might lead to significant gains in the overall cost of climate policy.

The third part presents results of a survey conducted among the main economic and environmental associations in Switzerland. The survey reveals conflicting views on economic instruments. It shows how the social acceptability of these instruments can be improved in taking explicitly into account these opposing views of special interest groups. Therefore, policy scenarios should be selected in combining techno-economic models with empirical studies about their political and normative context.     

An International Relations perspective on the global politics of carbon dioxide capture and storage

With the publication of the IPCC Special Report on Carbon dioxide Capture and Storage (CCS), CCS has emerged as a focal issue in international climate diplomacy and energy collaboration. This paper has two goals. The first goal is to map CCS activities in and among various types of intergovernmental organisations; the second goal is to apply International Relations (IR) theories to explain the growing diversity, overlap and fragmentation of international organisations dealing with CCS. Which international organisations embrace CCS, and which refrain from discussing it at all? What role do these institutions play in bringing CCS forward? Why is international collaboration on CCS so fragmented and weak? We utilise realism, liberal institutionalism and constructivism to provide three different interpretations of the complex global landscape of CCS governance in the context of the similarly complicated architecture of global climate policy. A realist account of CCS's fragmented international politics is power driven. International fossil fuel and energy organisations, dominated by major emitter states, take an active role in CCS. An interest-based approach, such as liberal institutionalism, claims that CCS is part of a “regime complex” rather than an integrated, hierarchical, comprehensive and international regime. Such a regime complex is exemplified by the plethora of international organisations with a role in CCS. Finally, constructivism moves beyond material and interest-based interpretations of the evolution of the institutionally fragmented architecture of global CCS governance. The 2005 IPCC Special Report on CCS demonstrates the pivotal role that ideas, norms and scientific knowledge have played in transforming the preferences of the international climate-change policy community.     

Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria

Few well-dated, quantitative Holocene temperature reconstructions exist from high-altitude sites in the Central Eastern Alps. Here, we present a chironomid-based quantitative reconstruction of mean July air temperatures (T_July) throughout the Holocene for a remote high-mountain lake, Schwarzsee ob Sölden, situated above the treeline at 2796 m a.s.l. in the Austrian Alps. Applying a chironomid-temperature inference model developed from lakes of the Alpine region to a high-resolution chironomid record from the lake provides evidence for early Holocene (ca 10000–8600 cal yr BP) T_July of up to 8.5 °C, i.e. >4 °C above the modern (1977–2006) mean July temperature. The reconstruction reveals the so-called ‘8.2-ka cold event’ centered at ca 8250–8000 cal yr BP with temperatures ca 3 °C below the early-Holocene thermal maximum. Rather warm (ca 6 °C) and productive conditions prevailed during ca 7900–4500 cal yr BP. The chironomid record suggests a climate transition between ca 5200 and 4500 cal yr BP to cooler T_July. A distinct cooling trend is evident from ca 4500 until ca 2500 cal yr BP. Thereafter, the study site experienced its coldest conditions (around 4 °C or less) throughout the rest of the Holocene, with the exception of the warming trend during the late 20th century. Beside other factors, the Northern Hemisphere summer insolation seems to be the major driving force for the long-term trends in T_July at high altitudes in the Eastern Alps. Due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set, the chironomid-based temperature reconstruction fails to track phases of the late-Holocene climatic history with T_July cooler than 4 °C. Further chironomid-based palaeoclimate model and down-core studies are required to address this problem, provide more realistic T_July estimates from undisturbed high-altitude lakes in the Alps, and extract a reliable regional temperature signal.     

Modeling the morphodynamic response of tidal embayments to sea-level rise

Sea-level rise has a strong influence on tidal systems, and a major focus of climate change effect studies is to predict the future state of these environmental systems. Here, we used a model to simulate the morphological evolution of tidal embayments and to explore their response to a rising sea level. The model was first used to reproduce the formation of channels and intertidal flats under a stable mean water level in an idealised and initially unchannelled tidal basin. A gradual rise in sea level was imposed once a well-developed channel network had formed. Simulations were conducted with different sea-level rise rates and tidal ranges. Sea-level rise forced headward erosion of the tidal channels, driving a landward expansion of the channel network and channel development in the previously non-inundated part of the basin. Simultaneously, an increase in channel drainage width in the lower part of the basin occurred and a decrease in the overall fraction of the basin occupied by channels could be observed. Sea-level rise thus altered important characteristics of the tidal channel network. Some intertidal areas were maintained despite a rising sea level. However, the size, shape, and location of the intertidal areas changed. In addition, sea-level rise affected the exchange of sediment between the different morphological elements. A shift from exporting to importing sediment as well as a reinforcement of the existing sediment export was observed for the simulations performed here. Sediment erosion in the inlet and the offshore transport of sediment was enhanced, resulting in the expansion of the ebb-tidal delta. Our model results further emphasise that tidal embayments can exhibit contrasting responses to sea-level rise.     

Gamma-ray bursts from unstable Poynting-dominated outflows

Poynting-flux driven outflows from magnetized rotators are a plausible explanation for gamma-ray burst engines. We suggest a new possibility for how such outflows might transfer energy into radiating particles. We argue that, in a region near the rotation axis, the Poynting flux drives non-linearly unstable large-amplitude electromagnetic waves (LAEMW) that 'break' at radii     where the MHD approximation becomes inapplicable. In the 'foaming' (relativistically reconnecting) regions formed during the wave breaks, the random electric fields stochastically accelerate particles to ultrarelativistic energies which then radiate in turbulent electromagnetic fields. The typical energy of the emitted photons is a fraction of the fundamental Compton energy     with     plus additional boosting due to the bulk motion of the medium. The emission properties are similar to synchrotron radiation, with a typical cooling time ∼10⁻³ s. During the wave break, the plasma is also bulk accelerated in the outward radial direction and at larger radii can produce afterglows due to interactions with the external medium. The near equipartition fields required by afterglow models may be due to magnetic field regeneration in the outflowing plasma (similar to field generation by LAEMW in laser–plasma interactions) and mixing with the upstream plasma.