Impact of climate on landscape form,sediment transfer and the sedimentary record     

Rebekah M. Harries  Boris Gailleton  Linda A. Kirstein  Mikael Attal  Alexander C. Whittaker  Simon M. Mudd 《地球表面变化过程与地形》2021,46(5):990-1006

The relationship between climate, landscape connectivity and sediment export from mountain ranges is key to understanding the propagation of erosion signals downstream into sedimentary basins. We explore the role of connectivity in modulating the composition of sediment exported from the Frontal Cordillera of the south-central Argentine Andes by comparing three adjacent and apparently similar semi-glaciated catchment-fan systems within the context of an along-strike precipitation gradient. We first identify that the bedrock exposed in the upper, previously glaciated reaches of the cordillera is under-represented in the lithological composition of gravels on each of three alluvial fans. There is little evidence for abrasion or preferential weathering of sediment sourced from the upper cordillera, suggesting that the observed bias can only be explained by sediment storage in these glacially widened and flattened valleys of the upper cordillera (as revealed by channel steepness mapping). A detailed analysis of the morphology of sedimentary deposits within the catchments reveals catchment-wide trends in either main valley incision or aggradation, linked to differences in hillslope–channel connectivity and precipitation. We observe that drier catchments have poor hillslope–channel connectivity and that gravels exported from dry catchments have a lithological composition depleted in clasts sourced from the upper cordillera. Conversely, the catchment with the highest maximum precipitation rate exhibits a high degree of connectivity between its sediment sources and the main river network, leading to the export of a greater proportion of upper cordillera gravel as well as a greater volume of sand. Finally, given a clear spatial correlation between the resistance of bedrock to erosion, mountain range elevation and its covariant, precipitation, we highlight how connectivity in these semi-glaciated landscapes can be preconditioned by the spatial distribution of bedrock lithology. These findings give insight into the extent to which sedimentary archives record source erosion patterns through time.  相似文献   

Displaced-Beam Small Aperture Scintillometer Test. Part I: The Wintex Data-Set   总被引：2，自引：2，他引：0  

H. A. R. De Bruin  W. M. L. Meijninger  Ann-Sofi Smedman  Mikael Magnusson 《Boundary-Layer Meteorology》2002,105(1):129-148

The friction velocity (u_*) and the sensible heat flux density (H) determined with a displaced-beam small aperture scintillometer (DBSAS) and a hot-film eddy correlation system are compared. Random errors in the DBSAS are relatively small, compared to scatter found with two eddy-correlation systems. Assuming that the hot-film system yields the true fluxes, theDBSAS appears to overestimate u_* when u_* is less than 0.2 m s^-1 and to underestimate u_* at high wind speeds. This implies that the DBSAS measurements of theinner scale length of turbulence, l₀, a direct measure for the dissipation rate of kinetic turbulent energy, are biased. Possible causes for these results are discussedin detail. A correction procedure is presented to account for effects of random noise and of so-called inactive turbulence or sensor vibrations. The errors in u_* cause errors in the DBSAS measurements of the structure parameter of temperature C_T ². The derived H appears to be less sensitive to errors in l₀ and C_T ², because errors in these quantities tend to cancel out.  相似文献   

Comparison of UV and IR Laser Ablation ICP-MS on Silicate Reference Materials and Implementation of Normalisation Factors for Quantitative Measurements     

Mikael Motelica-Heino  Olivier F.X. Donard 《Geostandards and Geoanalytical Research》2001,25(2-3):345-359

Direct analysis of geological reference materials was performed by LA-ICP-MS using two Nd:YAG laser systems operating at 266 nm and 1064 nm. The aim of this work was to compare UV and IR laser ablation and to assess the potential of the technique for the quantitative bulk analysis of rocks, sediments and soils. The laser sampling process was investigated and the analytical performance of both systems was compared. The influence of the laser operating conditions and the nature of the matrix on ICP-MS response factors calculated for major, minor and trace elements was evaluated. Under consistent laser settings, the response factors appeared to be matrix dependent. For a given matrix, the response factors were also significantly different for the two lasers. Normalisation with a single matrix element was effective only for matrices with similar mineralogy. When operating at 266 nm instead of 1064 nm, matrix effects could be reduced but not overcome. However, variations of the response factors between the different matrices appeared to be similar within distinct groups of elements, reflecting geochemical associations. When using multiple internal standards, matrix effects but also effects of the laser wavelength, could be fully compensated.  相似文献   

Biological record of added manganese in seawater: a new efficient tool to mark in vivo growth lines in the oyster species Crassostrea gigas     

Vincent Barbin  Karl Ramseyer  Mikael Elfman 《International Journal of Earth Sciences》2008,97(1):193-199

The biological response of increased manganese in seawater was tested experimentally with the oyster species Crassostrea gigas by adding, once per day, a fixed quantity of MnCl₂ to the container where the oysters were living. Uptake of Mn²⁺ in the shell was traced with cathodoluminescence and quantified with a high spatial resolution proton microprobe. The daily addition of MnCl₂ resulted in the visualization of distinct growth increments seen simultaneously in both the calcitic shell and the aragonitic ligament. A relation was observed between the addition of Mn²⁺ to the seawater and incorporation of Mn in the mineral part of the shell. Thus, addition of MnCl₂ to seawater is an efficient tool to mark in vivo growth increments in bio-mineralised carbonates.  相似文献   

The challenges of monitoring national climate policy: learning lessons from the EU     

Jonas J. Schoenefeld  Mikael Hildén  Andrew J. Jordan 《Climate Policy》2018,18(1):118-128

One of the most central and novel features of the new climate governance architecture emerging from the 2015 Paris Agreement is the transparency framework committing countries to provide, inter alia, regular progress reports on national pledges to address climate change. Many countries will rely on public policies to turn their pledges into action. This article focuses on the EU’s experience with monitoring national climate policies in order to understand the challenges that are likely to arise as the Paris Agreement is implemented around the world. To do so, the research employs – for the first time – comparative empirical data submitted by states to the EU’s monitoring system. Our findings reveal how the EU’s predominantly technical interpretation of four international reporting quality criteria – an approach borrowed from reporting on GHG fluxes – has constrained knowledge production and stymied debate on the performance of individual climate policies. Key obstacles to more in-depth reporting include not only political concerns over reporting burdens and costs, but also struggles over who determines the nature of climate policy monitoring, the perceived usefulness of reporting information, and the political control that policy knowledge inevitably generates. Given the post-Paris drive to achieve greater transparency, the EU’s experience offers a sobering reminder of the political and technical challenges associated with climate policy monitoring, challenges that are likely to bedevil the Paris Agreement for decades to come.

Policy relevance

The 2009 Copenhagen summit ushered in a more bottom-up system of international climate governance. Such systems typically depend on strong monitoring approaches to assess past performance and estimate future national contributions over time. This article shows why decision makers at multiple governance levels should pay serious attention to empirical data on the experiences and challenges that have emerged around monitoring in the EU, a self-proclaimed climate leader. The analysis highlights key political and administrative challenges that policy makers will likely encounter in implementing climate policy monitoring and ensuring transparency in the spirit of the Paris Agreement.  相似文献   

Combining airborne laser scanning and Landsat data for statistical modeling of soil carbon and tree biomass in Tanzanian Miombo woodlands     

Mikael Egberth  Gert Nyberg  Erik Næsset  Terje Gobakken  Ernest Mauya  Rogers Malimbwi  Josiah Katani  Nurudin Chamuya  George Bulenga  Håkan Olsson 《Carbon balance and management》2017,12(1):8

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Application of a mass-balance model to predict PCDD/F turnover in a Baltic coastal estuary     

O. Magnus Karlsson  J. Mikael Malmaeus  Sarah Josefsson  Karin Wiberg  Lars Håkanson 《Estuarine, Coastal and Shelf Science》2010

A dynamical, process-based mass-balance model was applied to quantify the transports of polychlorinated-p-dibenzodioxins and dibenzofurans (PCDD/Fs) to, within and from the Kallrigafjärden Bay, a coastal estuary in the Baltic Sea, and to predict the PCDD/F levels in the water and sediments of the bay. Before the modelling, a one-year sampling programme was implemented in 2007–2008 to measure the flows of PCDD/Fs in tributaries entering the system, the fluxes from the adjacent sea and the levels in water, sediment and fish within the estuary. The collected data set was used as input data to the model and for validation purposes.  相似文献   

Characteristic features of air ions at Mace Head on the west coast of Ireland     

Marko Vana  Mikael Ehn  Tuukka Petj  Henri Vuollekoski  Pasi Aalto  Gerrit de Leeuw  Darius Ceburnis  Colin D. O'Dowd  Markku Kulmala 《Atmospheric Research》2008,90(2-4):278-ICNAA07

Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm³. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm^− 3 for the negative ions and 423 cm^− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm²V^− 1s^− 1 and 1.49 cm²V^− 1s^− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.  相似文献   

Modelling Fracture Propagation in Anisotropic Rock Mass     

Baotang Shen  Topias Siren  Mikael Rinne 《Rock Mechanics and Rock Engineering》2015,48(3):1067-1081

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Carbon capture and storage in developing countries: A comparison of Brazil, South Africa and India     

Mikael Román 《Global Environmental Change》2011,21(2):391-401

The ambition to introduce carbon capture and storage (CCS) technology in developing countries raises particular considerations and challenges, where, most fundamentally, pressing socio-economic needs imply that there are other political priorities than GHG mitigation. This suggests that the interest in, and viability of, large-scale deployment of CCS in developing countries has to be analyzed as a strategic issue in the overall context of national development. But what are then the strategic concerns that may influence developing countries’ decisions to pursue large-scale deployment of CCS technology? The present article takes a first step in answering this question by comparing CCS policies and ongoing activities in Brazil, India and South Africa.  相似文献