Late Glacial ice advances in southeast Tibet

The sensitivity of Tibetan glacial systems to North Atlantic climate forcing is a major issue in palaeoclimatology. In this study, we present surface exposure ages of erratic boulders from a valley system in the Hengduan Mountains, southeastern Tibet, showing evidence of an ice advance during Heinrich event 1. Cosmogenic nuclide analyses (¹⁰Be and ²¹Ne) revealed consistent exposure ages, indicating no major periods of burial or pre-exposure. Erosion-corrected (3 mm/ka) ¹⁰Be exposure ages range from 13.4 to 16.3 ka. This is in agreement with recalculated exposure ages from the same valley system by [Tschudi, S., Schäfer, J.M., Zhao, Z., Wu, X., Ivy-Ochs, S., Kubik, P.W., Schlüchter, C., 2003. Glacial advances in Tibet during the Younger Dryas? Evidence from cosmogenic ¹⁰Be, ²⁶Al, and ²¹Ne. Journal of Asian Earth Sciences 22, 301–306.]. Thus this indicates that local glaciers advanced in the investigated area as a response to Heinrich event 1 cooling and that periglacial surface adjustments during the Younger Dryas overprinted the glacial morphology, leading to deceptively young exposure ages of certain erratic boulders.     

A model for multiphase flow and transport in porous media including a phenomenological approach to account for deformation—a model concept and its validation within a code intercomparison study

Multiphase flow processes in unsaturated cohesive soils are often affected by deformation due to swelling and shrinking as a result of varying water contents. This paper presents a model concept which is denoted ‘phenomenological’ in terms of the processes responsible for soil deformation, since the effects of deformation on flow and transport are only considered by constitutive relations that allow an adaptation of the hydraulic properties. This new model is validated in a detailed intercomparison study with two state-of-the-art models that are capable of explicitly describing the processes relevant for the deformation. A ‘numerical experiment’ with a state-of-the-art reference model is used to produce ‘measurement data’ for an inverse-modelling-based estimation of the model input parameters for the phenomenological concept.     

The competing models for the origin and internal evolution of granitic pegmatites in the light of melt and fluid inclusion research

In this paper we discuss the main petrogenetic models for granitic pegmatites and how these models have evolved over time. We suggest that the present state of knowledge requires that some aspects of these models to be modified, or absorbed into newer ones. Pegmatite formation and internal evolution have long supposed the need for highly water- and flux-enriched magmas to explain the differences between pegmatites and other intrusives of similar major element composition. Compositions and textural characteristics of fluid and melt inclusions in pegmatite minerals provide strong evidence for such magmas. Furthermore, we show that melt inclusion research has increased the number of potential flux components, which may include H₂O, OH^?, CO₂, HCO ₃ ^? , CO ₃ ^2? , SO ₄ ^2? , PO ₄ ^3? , H₃BO₃, F , and Cl, as well as the elements Li, Na, K, Rb, Cs, and Be, herein described as melt structure modifiers. In this paper we emphasize that the combined effect which these components have on the properties of pegmatite melts is difficult to deduce from experimental studies using only a limited number of these components. The combination and the amount of the different magmatic species, together with differences in the source region, and variations in pressure and temperature cause the great diversity of the pegmatites observed. Some volatile species, such as CO ₃ ^2? and alkalis, have the capacity to increase the solubility of H₂O in silicate melt to an extraordinary degree, to the extent that melt-melt-fluid immiscibility becomes inevitable. It is our view that the formation of pegmatites is connected with the complex interplay of many factors.     

It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.     

Climate impact of high northern vegetation: Late Miocene and present

The Late Miocene belongs to the late phase of the Cenozoic. Climate at that time was still warmer and more humid as compared to today, especially in the high latitudes. Corresponding to the climate situation, palaeobotanical evidences support that vegetation in the high northern latitudes changed significantly from the Late Miocene until today. To quantify the climate impact of this vegetation change, we analyse how vegetation in the high northern latitudes contribute to climate evolution. For that, we perform climate modelling sensitivity experiments for the present and for the Late Miocene (Tortonian, 11–7 Ma). For our present-day sensitivity experiment, we introduce the Tortonian vegetation in the high northern latitudes. For our Tortonian sensitivity experiment, we introduce the modern vegetation on the same grid cells. In the Tortonian and in the present, the modern vegetation leads to a strong cooling of the northern extratropics (up to −4°C). Nevertheless, the meridional heat transports remain nearly unchanged in both cases. In general, the vegetation impact on climate is similar in the Tortonian and in the present. However, some exceptions occur. Due to the Tethys Ocean in the Tortonian, temperatures decline only weakly in eastern Europe and western Asia. In the Tortonian climate, temperatures on the Sahara realm rise (up to +1.5°C), while the temperatures do not change remarkably in the present-day climate. This different behaviour is caused by a stronger and more sensitive hydrological cycle on the Sahara region during the Tortonian.     

Automatic Representation of Geographical Data from a Semantic Point of View through a New Ontology and Classification Techniques

Providing Geographical Information Systems with mechanisms for processing geo‐data based on their semantics may help to solve problems like heterogeneity. This is because GIS could process geo‐data focusing on their meaning and not on their syntax and/or structure. An important aspect for achieving these objectives is the establishment of an automatic means of correspondence between geo‐data and their conceptualization in Higher Levels Ontologies (HLO). In this article, a new type of Ontology is proposed (Data‐Representation Ontology (DRO)). This Ontology describes the semantic embedded in geo‐data, which cannot be represented in current types of Ontologies. Across this Ontology, heterogeneous geographical data can be integrated in the semantic space contributing positively to the development of solutions for the problems of interoperability between heterogeneous systems. Likewise, we propose a new method for the automatic generation of the DRO and its interrelationships with HLO, based on pattern classification techniques. The experiments show that once the DRO is generated, the classifier can classify all data correctly. Thus, these data are semantically enriched. Moreover, this article shows how the topological relationships can enrich the semantics in the generated Ontology and increase the effectiveness of spatial analysis.     

Grain boundary and volume diffusion experiments in yttrium aluminium garnet bicrystals at 1,723 K: a miniaturized study

Yb-Y inter-diffusion along a single grain boundary of a synthetic yttrium aluminium garnet (YAG) bicrystal has been studied using analytical transmission electron microscopy (ATEM). To investigate the diffusion, a thin-film containing Yb as the diffusant was deposited perpendicular to the bicrystal grain boundary by pulsed laser deposition (PLD). Structural properties and their change with time in both the diffusant source and the grain boundary are reported. The diffusion profiles are incorporated in a numerical diffusion model, which is applied to determine the grain boundary diffusion coefficient, D _gb , at 1.723 K it is equal to 3 × 10⁻¹⁵ m²/s. We find that grain boundary diffusion is 4.85 orders of magnitude faster than volume diffusion, which was determined from the same diffusion experiment. This result is discussed in the context of special versus general grain boundaries. Finally, we successfully tested the capability of synchrotron-based nano-X-ray fluorescence analysis to map micro-chemical patterns in two dimensions with sub-micrometre resolution.     

Experimental growth of åkermanite reaction rims between wollastonite and monticellite: evidence for volume diffusion control

Growth rates of monomineralic, polycrystalline åkermanite (Ca₂MgSi₂O₇) rims produced by solid-state reactions between monticellite (CaMgSiO₄) and wollastonite (CaSiO₃) single crystals were determined at 0.5 GPa dry argon pressure, 1,000–1,200°C and 5 min to 60 h, using an internally heated pressure vessel. Inert Pt-markers, initially placed at the monticellite–wollastonite interface, indicate symmetrical growth into both directions. This and mass balance considerations demonstrate that rim growth is controlled by transport of MgO. At 1,200°C and run durations between 5 min and 60 h, rim growth follows a parabolic rate law with rim widths ranging from 0.4 to 16.3 μm indicating diffusion-controlled rim growth. The effective bulk diffusion coefficient \( D_{\text{eff,MgO}}^{\text{Ak}} \) is calculated to 10^?15.8±0.1 m² s^?1. Between 1,000°C and 1,200°C, the effective bulk diffusion coefficient follows an Arrhenius law with E _a = 204 ± 18 kJ/mol and D ₀ = 10^?8.6±1.6 m² s^?1. Åkermanite grains display a palisade texture with elongation perpendicular to the reaction interface. At 1,200°C, average grain widths measured normal to elongation, increase with the square root of time and range from 0.4 to 5.4 μm leading to a successive decrease in the grain boundary area fraction, which, however, does not affect \( D_{\text{eff,MgO}}^{\text{Ak}} \) to a detectible extent. This implies that grain boundary diffusion only accounts for a minor fraction of the overall chemical mass transfer, and rim growth is essentially controlled by volume diffusion. This is corroborated by the agreement between our estimates of the effective MgO bulk diffusion coefficient and experimentally determined volume diffusion data for Mg and O in åkermanite from the literature. There is sharp contrast to the MgO–SiO₂ binary system, where grain boundary diffusion controls rim growth.     

It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.     

TiO2 exsolution from garnet by open-system precipitation: evidence from crystallographic and shape preferred orientation of rutile inclusions

We investigated rutile needles with a clear shape preferred orientation in garnet from (ultra) high-pressure metapelites from the Kimi Complex of the Greek Rhodope by electron microprobe, electron backscatter diffraction and TEM techniques. A definite though complex crystallographic orientation relationship between the garnet host and rutile was identified in that Rt[001] is either parallel to Grt<111> or describes cones with opening angle 27.6° around Grt<111>. Each Rt[001] small circle representing a cone on the pole figure displays six maxima in the density plots. This evidence together with microchemical observations in TEM, when compared to various possible mechanisms of formation, corroborates a precipitate origin. A review of exchange vectors for Ti substitution in garnet indicates that rutile formation from garnet cannot occur in a closed system. It requires that components are exchanged between the garnet interior and the rock matrix by solid-state diffusion, a process we refer to as “open-system precipitation” (OSP). The kinetically most feasible reaction of this type will dominate the overall process. The perhaps most efficient reaction involves internal oxidation of Fe²⁺ to Fe³⁺ and transfer from the dodecahedral to the octahedral site just vacated by $ {\text{Ti}}^{ 4+ }: 6\,{\text{M}}^{ 2+ }_{ 3} {\text{TiAl}}\left[ {{\text{AlSi}}_{ 2} } \right]{\text{O}}_{ 1 2} + 6\,{\text{M}}^{ 2+ }_{ 2, 5} {\text{TiAlSi}}_{ 3} {\text{O}}_{ 1 2} = 10\,{\text{M}}^{ 2+ }_{ 3.0} {\text{Al}}_{ 1. 8} {\text{Fe}}_{0. 2} {\text{Si}}_{ 3} {\text{O}}_{ 1 2} + {\text{M}}^{2+} + 2 {\text{e}}^{-} + 1 2\,{\text{TiO}}_{ 2} . $ OSP is likely to occur at conditions where the transition of natural systems to open-system behaviour becomes apparent, as in the granulite and high-temperature eclogite facies.