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Katharina Anders Sabrina Marx Julia Boike Benjamin Herfort Evan James Wilcox Moritz Langer Philip Marsh Bernhard Höfle 《地球表面变化过程与地形》2020,45(7):1589-1600
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 相似文献
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Formation of the Wiesloch Mississippi Valley-type Zn-Pb-Ag deposit in the extensional setting of the Upper Rhinegraben, SW Germany 总被引：2，自引：0，他引：2
Katharina Pfaff Ludwig H. Hildebrandt David L. Leach Dorrit E. Jacob Gregor Markl 《Mineralium Deposita》2010,45(7):647-666
The Mississippi Valley-type (MVT) Zn–Pb–Ag deposit in the Wiesloch area, Southwest Germany, is controlled by graben-related
faults of the Upper Rhinegraben. Mineralization occurs as vein fillings and irregular replacement ore bodies consisting of
sphalerite, banded sphalerite, galena, pyrite, sulfosalts (jordanite and geocronite), barite, and calcite in the Middle Triassic
carbonate host rock. Combining paragenetic information, fluid inclusion investigations, stable isotope and mineral chemistry
with thermodynamic modeling, we have derived a model for the formation of the Wiesloch deposit. This model involves fluid
mixing between ascending hot brines (originating in the crystalline basement) with sedimentary formation waters. The ascending
brines originally had a near-neutral pH (around 6) and intermediate oxidation state, reflecting equilibrium with granites
and gneisses in the basement. During fluid ascent and cooling, the pH of the brine shifted towards more acidic (around 4)
and the oxidation state increased to conditions above the hematite-magnetite buffer. These chemical characteristics contrast
strongly with those of the pore and fracture fluid residing in the limestone aquifer, which had a pH between 8 and 9 in equilibrium
with calcite and was rather reduced due to the presence of organic matter in the limestone. Mixing between these two fluids
resulted in a strong decrease in the solubility of silver-bearing sphalerite and galena, and calcite. Besides Wiesloch, several
Pb–Zn deposits are known along the Upper Rhinegraben, including hydrothermal vein-type deposits like Badenweiler and the Michael
mine near Lahr. They all share the same fluid origin and formation process and only differ in details of their host rock and
fluid cooling paths. The mechanism of fluid mixing also seems to be responsible for the formation of other MVT deposits in
Europe (e.g., Réocin, Northern Spain; Trèves, Southern France; and Cracow-Silesia, Poland), which show notable similarities
in terms of their age, mineralogy. and mineral chemistry to the MVT deposit near Wiesloch. 相似文献
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Erin Bohensky James R.A. ButlerRobert Costanza Iris BohnetAurélie Delisle Katharina FabriciusMargaret Gooch Ida KubiszewskiGeorge Lukacs Petina PertEric Wolanski 《Global Environmental Change》2011,21(3):876-893
The extent to which nations and regions can actively shape the future or must passively respond to global forces is a topic of relevance to current discourses on climate change. In Australia, climate change has been identified as the greatest threat to the ecological resilience of the Great Barrier Reef, but is exacerbated by regional and local pressures. We undertook a scenario analysis to explore how two key uncertainties may influence these threats and their impact on the Great Barrier Reef and adjacent catchments in 2100: whether (1) global development and (2) Australian development is defined and pursued primarily in terms of economic growth or broader concepts of human well-being and environmental sustainability, and in turn, how climate change is managed and mitigated. We compared the implications of four scenarios for marine and terrestrial ecosystem services and human well-being. The results suggest that while regional actions can partially offset global inaction on climate change until about mid-century, there are probable threshold levels for marine ecosystems, beyond which the Great Barrier Reef will become a fundamentally different system by 2100 if climate change is not curtailed. Management that can respond to pressures at both global and regional scales will be needed to maintain the full range of ecosystem services. Modest improvements in human well-being appear possible even while ecosystem services decline, but only where regional management is strong. The future of the region depends largely on whether national and regional decision-makers choose to be active future ‘makers’ or passive future ‘takers’ in responding to global drivers of change. We conclude by discussing potential avenues for using these scenarios further with the Great Barrier Reef region's stakeholders. 相似文献
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Golbuu Y van Woesik R Richmond RH Harrison P Fabricius KE 《Marine pollution bulletin》2011,62(4):824-831
Coral community structure is often governed by a suite of processes that are becoming increasingly influenced by land-use changes and related terrestrial discharges. We studied sites along a watershed gradient to examine both the physical environment and the associated biological communities. Transplanted corals showed no differences in growth rates and mortality along the watershed gradient. However, coral cover, coral richness, and coral colony density increased with increasing distance from the mouth of the bay. There was a negative relationship between coral cover and mean suspended solids concentration. Negative relationships were also found between terrigenous sedimentation rates and the richness of adult and juvenile corals. These results have major implications not only for Pacific islands but for all countries with reef systems downstream of rivers. Land development very often leads to increases in river runoff and suspended solids concentrations that reduce coral cover and coral diversity on adjacent reefs. 相似文献
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Katharina LoddersBruce Fegley Jr. 《Icarus》2002,155(2):393-424
The chemical species containing carbon, nitrogen, and oxygen in atmospheres of giant planets, brown dwarfs (T and L dwarfs), and low-mass stars (M dwarfs) are identified as part of a comprehensive set of thermochemical equilibrium and kinetic calculations for all elements. The calculations cover a wide temperature and pressure range in the upper portions of giant planetary and T-, L-, and M-dwarf atmospheres. Emphasis is placed on the major gases CH4, CO, NH3, N2, and H2O but other less abundant gases are included. The results presented are independent of particular model atmospheres, and can be used to constrain model atmosphere temperatures and pressures from observations of different gases. The influence of metallicity on the speciation of these key elements under pressure-temperature (P-T) conditions relevant to low-mass object atmospheres is discussed. The results of the thermochemical equilibrium computations indicate that several compounds may be useful to establish temperature or pressure scales for giant planet, brown dwarf, or dwarf star atmospheres. We find that ethane and methanol abundance are useful temperature probes in giant planets and methane dwarfs such as Gl 229B, and that CO2 can serve as a temperature probe in more massive objects. Imidogen (NH) abundances are a unique pressure-independent temperature probe for all objects. Total pressure probes for warmer brown dwarfs and M dwarfs are HCN, HCNO, and CH2O. No temperature-independent probes for the total pressure in giant planets or T-dwarf atmospheres are identified among the more abundant C, N, and O bearing gases investigated here. 相似文献
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Negri A Vollhardt C Humphrey C Heyward A Jones R Eaglesham G Fabricius K 《Marine pollution bulletin》2005,51(1-4):370-383
The effects of the herbicide diuron on the early life history stages of broadcast spawning and brooding corals were examined in laboratory experiments. Fertilisation of Acropora millepora and Montipora aequituberculata oocytes were not inhibited at diuron concentrations of up to 1000 microg l(-1). Metamorphosis of symbiont-free A. millepora larvae was only significantly inhibited at 300 microg l(-1) diuron. Pocillopora damicornis larvae, which contain symbiotic dinoflagellates, were able to undergo metamorphosis after 24 h exposure to diuron at 1000 microg l(-1). Two-week old P. damicornis recruits on the other hand were as susceptible to diuron as adult colonies, with expulsion of symbiotic dinoflagellates (bleaching) evident at 10 microg l(-1) diuron after 96 h exposure. Reversible metamorphosis was observed at high diuron concentrations, with fully bleached polyps escaping from their skeletons. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques demonstrated a reduction in photosynthetic efficiency (Delta F/F(m)') in illuminated P. damicornis recruits after a 2 h exposure to 1 microg l(-1) diuron. The dark-adapted quantum yields (F(v)/F(m)) also declined, indicating chronic photoinhibition and damage to photosystem II. 相似文献
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Giovanni Spagnoli Mark Hannington Katharina Bairlein Andreas Hördt Marion Jegen Sven Petersen Tea Laurila 《Geo-Marine Letters》2016,36(3):235-245
Seafloor massive sulfide (SMS) deposits are increasingly seen as important marine metal resources for the future. A growing number of industrialized nations are involved in the surveying and sampling of such deposits by drilling. Drill ships are expensive and their availability can be limited; seabed drill rigs are a cost-effective alternative and more suitable for obtaining cores for resource evaluation. In order to achieve the objectives of resource evaluations, details are required of the geological, mineralogical, and physical properties of the polymetallic deposits and their host rocks. Electrical properties of the deposits and their ore minerals are distinct from their unmineralized host rocks. Therefore, the use of electrical methods to detect SMS while drilling and recovering drill cores could decrease the costs and accelerate offshore operations by limiting the amount of drilling in unmineralized material. This paper presents new data regarding the electrical properties of SMS cores that can be used in that assessment. Frequency-dependent complex electrical resistivity in the frequency range between 0.002 and 100 Hz was examined in order to potentially discriminate between different types of fresh rocks, alteration and mineralization. Forty mini-cores of SMS and unmineralized host rocks were tested in the laboratory, originating from different tectonic settings such as the intermediate-spreading ridges of the Galapagos and Axial Seamount, and the Pacmanus back-arc basin. The results indicate that there is a clear potential to distinguish between mineralized and non-mineralized samples, with some evidence that even different types of mineralization can be discriminated. This could be achieved using resistivity magnitude alone with appropriate rig-mounted electrical sensors. Exploiting the frequency-dependent behavior of resistivity might amplify the differences and further improve the rock characterization. 相似文献