Temporal and spatial variability of geochemical backgrounds in the Windmill Islands,East Antarctica: Implications for climatic changes and human impacts

To establish a natural background and its temporal and spatial variability for the area around Casey Station in the Windmill Islands, East Antarctica, the authors studied major and trace element concentrations and the distribution of organic matter in marine and lacustrine sediments. A wide range of natural variability in trace metal concentrations was identified between sites and within a time scale of 9 ka (e.g., Ni 5–37 mg kg⁻¹, Cu 20–190 mg kg⁻¹, Zn 50–300 mg kg⁻¹, Pb 4.5–34 mg kg⁻¹). TOC concentrations are as high as 3 wt.% at the marine sites and 20 wt.% at the lacustrine sites, and indicate highly productive ecosystems. These data provide a background upon which the extent of human impact can be established, and existing data indicate negligible levels of disturbance. Geochemical and lithological data for a lacustrine sediment core from Beall Lake confirm earlier interpretation of recent climatic changes based on diatom distribution, and the onset of deglaciation in the northern part of the Windmill Islands between 8.6 and 8.0 ka BP. The results demonstrate that geochemical and lithological data can not only be used to define natural background values, but also to assess long-term climatic changes of a specific environment. Other sites, however, preserve a completely different sedimentary record. Therefore, inferred climatic record, and differences between sites, can be ascribed to differences in elevation, distance from the shore, water depth, and local catchment features. The extreme level of spatial variability seems to be a feature of Antarctic coastal areas, and demonstrates that results obtained from a specific site cannot be easily generalized to a larger area.     

Climate or development: is ODA diverted from its original purpose?

We analyze the interaction of climate and development policy that has taken place since the early 1990s. Increasing dissatisfaction about the results of traditional development cooperation and the appeal of climate policy as a new policy field led to a rapid reorientation of aid flows. At the turn of the century, over 7% of aid flows were spent on greenhouse gas emissions mitigation. However, the contribution of emissions mitigation projects to the central development objective of poverty reduction as specified in the Millennium Development Goals is limited and other project types are likely to be much more effective. Adaptation to climate change can be expected to have higher synergies with poverty alleviation than mitigation, primarily through its impact on health, the conservation of arable land and the protection against natural disasters. An analysis of the Clean Development Mechanism shows that projects addressing the poor directly are very rare; even small renewable energy projects in rural areas tend to benefit rich farmers and the urban population. Use of development aid for CDM projects and / or their preparation via capacity building is thus clearly not warranted. We further analyze whether the use of development aid for climate policy could be justified as a countermeasure against the emission increase related to successful development itself. However, countries that are achieving an improvement of human development from a low level are unlikely to increase their energy consumption substantially. Only at a level where the middle class expands rapidly, energy consumption and greenhouse gas emissions soar. Thus targeting middle class energy consumption by appliance efficiency standards and public transport-friendly urban planning are the most effective measures to address developing country emissions. Rural renewable energy provision in poor countries has a much higher impact on poverty, but a much lower impact on greenhouse gas emissions. We conclude that while there are valid reasons for long-term collaboration with emerging economies on greenhouse gas mitigation, there should be a separate budget line for such activities to avoid “obfuscation” of a decline of resources aimed at poverty alleviation. Nevertheless, mitigation will remain attractive for donors because it ensures quick disbursements and relatively simple measures of success. Moreover, mitigation activities in developing countries provide politicians in industrialized countries with a welcome strategy to divert the attention of their constituencies from the lack of success in reducing greenhouse gas emissions domestically.     

On multicomponent gas diffusion and coupling concepts for porous media and free flow: a benchmark study

Computational Geosciences - Multicomponent gas transport in porous media and at the interface between porous media and free flow occurs in a wide range of technical and environmental systems....     

Multitemporal terrestrial laser scanning point clouds for thaw subsidence observation at Arctic permafrost monitoring sites

This paper investigates different methods for quantifying thaw subsidence using terrestrial laser scanning (TLS) point clouds. Thaw subsidence is a slow (millimetre to centimetre per year) vertical displacement of the ground surface common in ice-rich permafrost-underlain landscapes. It is difficult to quantify thaw subsidence in tundra areas as they often lack stable reference frames. Also, there is no solid ground surface to serve as a basis for elevation measurements, due to a continuous moss–lichen cover. We investigate how an expert-driven method improves the accuracy of benchmark measurements at discrete locations within two sites using multitemporal TLS data of a 1-year period. Our method aggregates multiple experts’ determination of the ground surface in 3D point clouds, collected in a web-based tool. We then compare this to the performance of a fully automated ground surface determination method. Lastly, we quantify ground surface displacement by directly computing multitemporal point cloud distances, thereby extending thaw subsidence observation to an area-based assessment. Using the expert-driven quantification as reference, we validate the other methods, including in-situ benchmark measurements from a conventional field survey. This study demonstrates that quantifying the ground surface using 3D point clouds is more accurate than the field survey method. The expert-driven method achieves an accuracy of 0.1 ± 0.1 cm. Compared to this, in-situ benchmark measurements by single surveyors yield an accuracy of 0.4 ± 1.5 cm. This difference between the two methods is important, considering an observed displacement of 1.4 cm at the sites. Thaw subsidence quantification with the fully automatic benchmark-based method achieves an accuracy of 0.2 ± 0.5 cm and direct point cloud distance computation an accuracy of 0.2 ± 0.9 cm. The range in accuracy is largely influenced by properties of vegetation structure at locations within the sites. The developed methods enable a link of automated quantification and expert judgement for transparent long-term monitoring of permafrost subsidence. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Calcium Isotopes (δ44/40Ca) in MPI-DING Reference Glasses, USGS Rock Powders and Various Rocks: Evidence for Ca Isotope Fractionation in Terrestrial Silicates

We report δ^44/40Ca_{(SRM 915a)} values for eight fused MPI‐DING glasses and the respective original powders, six USGS igneous rock reference materials, the U‐Th disequilibria reference material TML, IAEA‐CO1 (Carrara marble) and several igneous rocks (komatiites and carbonatites). Sample selection was guided by three considerations: (1) to address the need for information values on reference materials that are widely available in support of interlaboratory comparison studies; (2) support the development of in situ laser ablation and ion microprobe techniques, which require isotopically homogenous reference samples for ablation; and (3) provide Ca isotope values on a wider range of igneous and metamorphic rock types than is currently available in the scientific literature. Calcium isotope ratios were measured by thermal ionisation mass spectrometry in two laboratories (IFM‐GEOMAR and Saskatchewan Isotope Laboratory) using ⁴³Ca/⁴⁸Ca‐ and ⁴²Ca/⁴³Ca‐double spike techniques and reported relative to the calcium carbonate reference material NIST SRM 915a. The measurement uncertainty in both laboratories was better than 0.2‰ at the 95% confidence level. The impact of different preparation methods on the δ^44/40Ca_{(SRM 915a)} values was found to be negligible. Except for ML3‐B, the original powders and the respective MPI‐DING glasses showed identical δ^44/40Ca_{(SRM 915a)} values; therefore, possible variations in the Ca isotope compositions resulting from the fusion process are excluded. Individual analyses of different glass fragments indicated that the glasses are well homogenised on the mm scale with respect to Ca. The range of δ^44/40Ca_{(SRM 915a)} values in the igneous rocks studied was larger than previously observed, mostly owing to the inclusion of ultramafic rocks from ophiolite sections. In particular, the dunite DTS‐1 (1.49 ± 0.06‰) and the peridotite PCC‐1 (1.14 ± 0.07‰) are enriched in ⁴⁴Ca relative to volcanic rocks (0.8 ± 0.1‰). The Carrara marble (1.32 ± 0.06‰) was also found to be enriched in ⁴⁴Ca relative to the values of assumed precursor carbonates (< 0.8‰). These findings suggest that the isotopes of Ca are susceptible to fractionation at high temperatures by, as yet, unidentified igneous and metamorphic processes.     

Slip rate of trench‐parallel normal faulting along the Mejillones Fault (Atacama Fault System): Relationships with the northern Chile subduction and implications for seismic hazards

The recent tectonics of the arid northern Chile Andean western forearc is characterized by trench‐parallel normal faults within the Atacama Fault System (AFS). Since the 1995‐Mw 8.1 Antofagasta earthquake, the mechanism driving this recent and localized extension is considered to be associated with the seismic cycle within the subduction zone. Analyzing morphotectonic patterns along these faults allows examining the seismic potential associated with the subduction zone. Using field Digital Elevation Models and in situ‐produced cosmogenic ¹⁰Be, we determined a 0.2 mm/a long‐term slip rate along the Mejillones Fault, one of the most prominent structures within the AFS. This result suggests that the AFS corresponds to slow slip rate faults despite the rapid subduction context. However, the size of coseismic slips observed along the AFS faults suggests that larger subduction earthquakes (Mw > 8.1) may occur episodically in the area.