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31.
Anthony G. Patt Detlef P. van Vuuren Frans Berkhout Asbjørn Aaheim Andries F. Hof Morna Isaac Reinhard Mechler 《Climatic change》2010,99(3-4):383-402
Adaptation is an important element on the climate change policy agenda. Integrated assessment models, which are key tools to assess climate change policies, have begun to address adaptation, either by including it implicitly in damage cost estimates, or by making it an explicit control variable. We analyze how modelers have chosen to describe adaptation within an integrated framework, and suggest many ways they could improve the treatment of adaptation by considering more of its bottom-up characteristics. Until this happens, we suggest, models may be too optimistic about the net benefits adaptation can provide, and therefore may underestimate the amount of mitigation they judge to be socially optimal. Under some conditions, better modeling of adaptation costs and benefits could have important implications for defining mitigation targets. 相似文献
32.
Nicolas Rolland Isabelle Larocque Pierre Francus Reinhard Pienitz 《Quaternary Research》2009,72(1):27-37
This study presents the Late-Holocene evolution of a northern Southampton Island (Nunavut, Canada) lake, using fossil chironomids supported by sedimentological evidences (XRF, grain size and CNS). All proxies revealed a relatively stable environment during the last millennium with short-lived events driving changes in the entire lake ecosystem. The chironomid-based paleotemperatures revealed variations of significant amplitude coincident with changes in the sediment density and chemical composition of the core. Higher temperature intervals were generally correlated to lower sediment density with higher chironomid concentration and diversity. Higher temperatures were recorded from cal yr AD 1160 to AD 1360, which may correspond to the Medieval Warm Period. Between cal yr AD 1360 and AD 1700, lower temperatures were probably related to a Little Ice Age event. This study presents new information on the timing of known climatic events which will refine our knowledge of the paleoclimate and climatic models of the Foxe Basin region. It also provides a new framework for the evolution of such freshwater ecosystems under the “Anthropocene” and underlines the importance of including sedimentological proxies when interpreting chironomid remains as this combined approach provides an extended overview of the past hydrological and geochemical changes and their impacts on lake biota. 相似文献
33.
Julia CURIO Yongren CHEN Reinhard SCHIEMANN ANDrew G.TURNER Kai Chi WONG Kevin HODGES Yueqing LI 《大气科学进展》2018,35(8):965-980
Tibetan Plateau vortices(TPVs) are mesoscale cyclones originating over the Tibetan Plateau(TP) during the extended summer season(April–September).Most TPVs stay on the TP,but a small number can move off the TP to the east.TPVs are known to be one of the main precipitation-bearing systems on the TP and moving-off TPVs have been associated with heavy precipitation and flooding downstream of the TP(e.g.,in Sichuan province or over the Yangtze River Valley).Identifying and tracking TPVs is difficult because of their comparatively small horizontal extent(400–800 km) and the limited availability of soundings over the TP,which in turn constitutes a challenge for short-term predictions of TPV-related impacts and for the climatological study of TPVs.In this study,(i) manual tracking(MT) results using radiosonde data from a network over and downstream of the TP are compared with(ii) results obtained by an automated tracking(AT) algorithm applied to ERA-Interim data.Ten MT-TPV cases are selected based on method(i) and matched to and compared with the corresponding AT-TPVs identified with method(ii).Conversely,ten AT-TPVs are selected and compared with the corresponding MT-TPVs.In general,the comparison shows good results in cases where the underlying data are in good agreement,but considerable differences are also seen in some cases and explained in terms of differences in the tracking methods,data availability/coverage and disagreement between sounding and ERA-Interim data.Recommendations are given for future efforts in TPV detection and tracking,including in an operational weather forecasting context. 相似文献
34.
In the river Oder high-waters of the river with high nutrient loads and low biological activity mainly occur during winter. Thus, a remarkable portion of the annual load passes the estuary untransformed. During summer high level of biological activity is observed in the whole estuary, but while more than 10 mol/l dissolved inorganic nitrogen (DIN) is found in the Großes Haff, where the theoretical water-residence time is only 1 month, in the western part of the estuary, where the water-residence time is approximately 3 months, all DIN is transformed into organic matter.The transformed nutrients settle partly as biological products, but they are released again in these shallow waters due to biological and physical degradation, and transported into the Baltic Sea.This behaviour may explain why in the sediments of the Oderhaff with a sedimentation rate of 1 mm/year only 1% of the annual nutrient load of the Oder river can be found. 相似文献
35.
Roelof Rietbroek Mathias Fritsche Christoph Dahle Sandra-Esther Brunnabend Madlen Behnisch Jürgen Kusche Frank Flechtner Jens Schröter Reinhard Dietrich 《Surveys in Geophysics》2014,35(6):1267-1283
We investigated two ‘gap-filler’ methods based on GPS-derived low-degree surface loading variations (GPS-I and GPS-C) and a more simple method (REF-S) which extends a seasonal harmonic variation into the expected Gravity Recovery and Climate Experiment (GRACE) mission gap. We simulated two mission gaps in a reference solution (REF), which is derived from a joint inversion of GRACE (RL05) data, GPS-derived surface loading and simulated ocean bottom pressure. The GPS-I and GPS-C methods both have a new type of constraint applied to mitigate the lack of GPS station network coverage over the ocean. To obtain the GPS-C solution, the GPS-I method is adjusted such that it fits the reference solution better in a 1.5 year overlapping period outside of the gap. As can be expected, the GPS-I and GPS-C solutions contain larger errors compared to the reference solution, which is heavily constrained by GRACE. Within the simulated gaps, the GPS-C solution generally fits the reference solution better compared to the GPS-I method, both in terms of spherical harmonic loading coefficients and in terms of selected basin-averaged hydrological mass variations. Depending on the basin, the RMS-error of the water storage variations (scaled for leakage effects) ranges between 1.6 cm (Yukon) and 15.3 cm (Orinoco). In terms of noise level, the seasonal gap-filler method (REF-S) even outperforms the GPS-I and GPS-C methods, which are still affected by spatial aliasing problems. However, it must be noted that the REF-S method cannot be used beyond the study of simple harmonic seasonal variations. 相似文献
36.
Anna Schneider Horst H. Gerke Thomas Maurer Stefan Seifert Rossen Nenov Reinhard F. Hüttl 《地球表面变化过程与地形》2012,37(7):708-725
To quantify landscape change resulting from processes of erosion and deposition and to establish spatially distributed sediment budgets, ‘models of change’ can be established from a time series of digital elevation models (DEMs). However, resolution effects and measurement errors in DEMs may propagate to these models. This study aimed to evaluate and to modify remotely‐sensed DEMs for an improved quantification of initial sediment mass changes in an artificially‐created catchment. DEMs were constructed from photogrammetry‐based, airborne (ALS) and ground‐based laser scanning (TLS) data. Regions of differing morphological characteristics and vegetation cover were delineated. Three‐dimensional (3D) models of volume change were established and mass change was derived from these models. DEMs were modified region‐by‐region for rill, interrill and alluvial areas, based on logical and hydro‐geomorphological principles. Additional DEMs were constructed by combining multi‐source, modified data. Models were evaluated by comparison with d‐GPS reference data and by considering sediment budget plausibility. Comprehensive evaluation showed that DEM usability depends on a relation between the technique used to obtain elevation data, surface morphology and vegetation cover characteristics. Photogrammetry‐based DEMs were suited to quantification of change in interrill areas but strongly underestimated surface lowering in erosion rills. TLS DEMs were best suited to rill areas, while ALS DEMs performed best in vegetation‐covered alluvial areas. Agreement with reference data and budget plausibility were improved by modifications to photogrammetry‐ and TLS‐based DEMs. Results suggest that artefacts in DEMs can be reduced and hydro‐geomorphic surface structures can be better represented by applying region‐specific modifications. Photogrammetry‐based DEMs can be improved by combining higher and lower resolution data in defined structural units and applying modifications based on principles given by characteristic hydro‐geomorphic evolution. Results of the critical comparative evaluation of remotely‐sensed elevation data can help to better interpret DEM‐based quantifications of earth‐surface processes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
37.
Microstructural and magnetic investigations (anisotropy of magnetic susceptibility, AMS) on sections across basement–cover interfaces (BCI) revealed a complex evolution in the crystalline basement rocks beneath and in the basal units of the Caledonian fold-and-thrust belt: (1) Pre-Caledonian mylonitic fabrics in basement granite relate to steep shear zones. (2) Palaeoweathering formed smectite and illite at the expense of feldspar and mica. Secondary Fe-bearing clay minerals and the intensity of the chemical weathering control the bulk susceptibility. Changing susceptibility and AMS relate to a (time) sequence from primary magnetite to secondary paramagnetic clay to pyrite and ferrimagnetic pyrrhotite. (3) Burial compaction with BCI-parallel fabrics. (4) Caledonian cleavage, overprinted by décollement zones with S–C–C′ fabrics. Décollement cataclasis overprinted pre-existing magnetic fabrics and produced horizontal magnetic lineations and subhorizontal foliations defined by the S–C–C′ fabrics. Clay mineral enrichment, together with subsequent, BCI-parallel compaction fabrics, decreased the shear strength in the basement rocks beneath the BCI. Detachments initiated at such low-strength zones and produced allochthonous units with their footwall within crystalline basement rocks, an observation of general importance for orogenic fold-and-thrust belts. 相似文献
38.
Composition and origin of organic matter in surface sediments of Lake Sarbsko: A highly eutrophic and shallow coastal lake (northern Poland) 总被引:1,自引:0,他引:1
Micha? Woszczyk Achim Bechtel Reinhard Gratzer Maciej J. Kotarba Miko?aj Kokociński Jens Fiebig Roman Cie?liński 《Organic Geochemistry》2011,42(9):1025-1038
We present an organic geochemical study of surface sediments of Lake Sarbsko, a shallow coastal lake on the middle Polish Baltic coast. The aim was to provide evidence concerning the origin of the organic matter (OM) and its compositional diversity in surface deposits of this very productive, highly dynamic water body. The content and composition of the OM in the bottom sediments were investigated at 11 sampling stations throughout the lake basin. OM sources were assigned on the basis of bulk indicators [total organic carbon (TOC), total nitrogen (TN), δ13CTOC and δ15N and extractable OM yield], biomarker composition of extractable OM and compound-specific C isotope signatures. The source characterization of autochthonous compounds was verified via phytoplankton analysis. The distribution of gaseous hydrocarbons in the sediments, as well as temporal changes in lake water pH, the concentration of DIC (dissolved inorganic carbon) and δ13CDIC were used to trace OM decomposition.The sedimentary OM is composed mainly of well preserved phytoplankton compounds and shows minor spatial variability in composition. However, the presence of CH4 and CO2 in the bottom deposits provides evidence for microbial degradation of sedimentary OM. The transformation of organic compounds in surface, bottom and pore waters via oxidative processes influences carbonate equilibrium in the lake and seasonally favours precipitation or dissolution of CaCO3.The data enhance our understanding of the relationships between the composition of sedimentary OM and environmental conditions within coastal ecosystems and shed light on the reliability of OM proxies for environmental reconstruction of coastal lakes. 相似文献
39.
Reinhard Gratzer Achim BechtelReinhard F. Sachsenhofer Hans-Gert LinzerDoris Reischenbacher Hans-Martin Schulz 《Marine and Petroleum Geology》2011,28(6):1171-1186
The Alpine Foreland Basin is a minor oil and moderate gas province in central Europe. In the Austrian part of the Alpine Foreland Basin, oil and minor thermal gas are thought to be predominantly sourced from Lower Oligocene horizons (Schöneck and Eggerding formations). The source rocks are immature where the oil fields are located and enter the oil window at ca. 4 km depth beneath the Alpine nappes indicating long-distance lateral migration. Most important reservoirs are Upper Cretaceous and Eocene basal sandstones.Stable carbon isotope and biomarker ratios of oils from different reservoirs indicate compositional trends in W-E direction which reflect differences in source, depositional environment (facies), and maturity of potential source rocks. Thermal maturity parameters from oils of different fields are only in the western part consistent with northward displacement of immature oils by subsequently generated oils. In the eastern part of the basin different migration pathways must be assumed. The trend in S/(S + R) isomerisation of ααα-C29 steranes versus the αββ (20R)/ααα (20R) C29 steranes ratio from oil samples can be explained by differences in thermal maturation without involving long-distance migration. The results argue for hydrocarbon migration through highly permeable carrier beds or open faults rather than relatively short migration distances from the source. The lateral distance of oil fields to the position of mature source rocks beneath the Alpine nappes in the south suggests minimum migration distances between less than 20 km and more than 50 km.Biomarker compositions of the oils suggest Oligocene shaly to marly successions (i.e. Schoeneck, Dynow, and Eggerding formations) as potential source rocks, taking into account their immature character. Best matches are obtained between the oils and units a/b (marly shale) and c (black shale) of the “normal” Schöneck Formation, as well as with the so-called “Oberhofen Facies”. Results from open system pyrolysis-gas chromatography of potential source rocks indicate slightly higher sulphur content of the resulting pyrolysate from unit b. The enhanced dibenzothiophene/phenanthrene ratios of oils from the western part of the basin would be consistent with a higher contribution of unit b to hydrocarbon expulsion in this area. Differences in the relative contribution of sedimentary units to oil generation are inherited from thickness variations of respective units in the overthrusted sediments. The observed trend towards lighter δ13C values of hydrocarbon fractions from oil fields in a W-E direction are consistent with lower δ13C values of organic matter in unit c. 相似文献
40.
Numerous ordered defect structures are known that are related to the sodium chloride (or MgO) structure type, thus they are basically cubic closest packed (ccp) arrangements with vacancies. For example the NbO type is an MgO type in which one quarter each of the anions and the cations are missing compared to the ccp in such a way that both anions and cations are in square-planar coordination. In spinel, Al2MgO4, one half of the octahedrally coordinated cations are missing compared with the MgO type and only one eighth of the tetrahedrally coordinated sites within the ccp are occupied. What these cases have in common is that all these derivatives are rather dense. This is different in pharmacosiderite, K[Fe4(OH)4As3O12]. 6 to 7H2O, where one half of the anion positions, three quarters of the octahedral sites and five eighth of the tetrahedral sites remain vacant, compared to the spinel type. Pharmacosiderite is a wide open porous structure with zeolitic properties. We are illustrating these relationships using a Bärnighausen symmetry tree and by tables relating the various structure types to each other. 相似文献