Earth Surface Processes, Landforms and Sediment Deposits – By J S Bridge and R V Demicco     

Stephanie  Mills 《The Geographical journal》2009,175(3):242-243

  相似文献   

Water surface mapping from airborne laser scanning using signal intensity and elevation data     

Bernhard Höfle  Michael Vetter  Norbert Pfeifer  Gottfried Mandlburger  Johann Stötter 《地球表面变化过程与地形》2009,34(12):1635-1649

In recent years airborne laser scanning (ALS) evolved into a state‐of‐the‐art technology for topographic data acquisition. We present a novel, automatic method for water surface classification and delineation by combining the geometrical and signal intensity information provided by ALS. The reflection characteristics of water surfaces in the near‐infrared wavelength (1064 nm) of the ALS system along with the surface roughness information provide the basis for the differentiation between water and land areas. Water areas are characterized by a high number of laser shot dropouts and predominant low backscatter energy. In a preprocessing step, the recorded intensities are corrected for spherical loss and atmospheric attenuation, and the locations of laser shot dropouts are modeled. A seeded region growing segmentation, applied to the point cloud and the modeled dropouts, is used to detect potential water regions. Object‐based classification of the resulting segments determines the final separation of water and non‐water points. The water‐land‐boundary is defined by the central contour line of the transition zone between water and land points. We demonstrate that the proposed workflow succeeds for a regulated river (Inn, Austria) with smooth water surface as well as for a pro‐glacial braided river (Hintereisfernerbach, Austria). A multi‐temporal analysis over five years of the pro‐glacial river channel emphasizes the applicability of the developed method for different ALS systems and acquisition settings (e.g. point density). The validation, based on real time kinematic (RTK) global positioning system (GPS) field survey and a terrestrial orthophoto, indicate point cloud classification accuracy above 97% with 0·45 m planimetric accuracy (root mean square error) of the water–land boundary. This article shows the capability of ALS data for water surface mapping with a high degree of automation and accuracy. This provides valuable datasets for a number of applications in geomorphology, hydrology and hydraulics, such as monitoring of braided rivers, flood modeling and mapping. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Change and variability in sea ice during the 2007–2008 Canadian International Polar Year program     

David G. Barber  Matthew G. Asplin  Richard L. Raddatz  Lauren M. Candlish  Scot Nickels  Stephanie Meakin  Klaus P. Hochheim  Jennifer V. Lukovich  Ryan J. Galley  Simon J. Prinsenberg 《Climatic change》2012,115(1):115-133

In this paper we describe sea ice change and variability during the Canadian International Polar Year (IPY) program and examine several regional and hemispheric causes of this change. In a companion paper (Barber et al., Climate Change 2012) we present an overview of the consequences of this observed change and variability on ecosystem function, climatically relevant gas exchange, habitats of primary and apex predators, and impacts on northern peoples. Sea ice-themed research projects within the fourth IPY were designed to be among the most diverse international science programs. They greatly enhanced the exchange of Inuit knowledge and scientific ideas across nations and disciplines. This interdisciplinary and cultural exchange helped to explain and communicate the impacts of a transition of the Arctic Ocean and ecosystem to a seasonally ice-free state, the commensurate replacement of perennial with annual sea ice types and the causes and consequences of this globally significant metamorphosis. This paper presents a synthesis of scientific sea ice research and traditional knowledge results from Canadian-led IPY projects between 2007 and 2009. In particular, a summary of sea ice trends, basin-wide and regional, is presented in conjunction with Inuit knowledge of sea ice, gathered from communities in northern Canada. We focus on the recent observed changes in sea ice and discuss some of the causes of this change including atmospheric and oceanic forcing of both dynamic and thermodynamic forcing on the ice. Pertinent results include: 1) In the Amundsen Gulf, at the western end of the Northwest Passage, open water persists longer than normal and winter sea ice is thinner and more mobile. 2) Large areas of summer sea ice are becoming heavily decayed during summer and can be broken up by long-period waves being generated in the now extensive open water areas of the Chukchi Sea. 3) Cyclones play an important role in flaw leads??regions of open water between pack ice and land-fast ice. They delay the formation of new ice and the growth of multi-year ice. 4) Feedbacks involving the increased period of open water, long-period wave generation, increased open-ocean roughness, and the precipitation of autumn snow are all partially responsible for the observed reduction in multiyear sea ice. 5) The atmosphere is observed as remaining generally stable throughout the winter, preventing vertical entrainment of moisture above the surface.  相似文献   

Rhyolites at Kerlingarfjöll, Iceland: the evolution and lifespan of silicic central volcanoes     

Stephanie Flude  David W. McGarvie  Ray Burgess  Andrew G. Tindle 《Bulletin of Volcanology》2010,72(5):523-538

Kerlingarfjöll central volcano is Iceland’s second largest outcrop of Quaternary rhyolite and is part of the Icelandic Western Rift Zone. Geochemical and Ar/Ar age data show that at least 21 different rhyolite eruptions have taken place at Kerlingarfjöll over the last 350 ka. Ar/Ar dating was carried out on samples of obsidian which showed variable reproducibility, illustrating the difficulty in dating young Icelandic volcanics. Nevertheless, reasonable estimates of eruption age have been derived for a number of eruptive units that are consistent with observed stratigraphy, enabling an understanding of the temporal evolution of Kerlingarfjöll. Two rhyolite magma types are present. The first is an older, low-Nb rhyolite that was erupted episodically along a cryptic curved fracture system, to form a discontinuous ring of rhyolite mountains, between 350 and 250 ka. This discontinuous ring is similar to structures observed at other volcanoes in Iceland, suggesting that the development of a curved fracture that acts as a pathway for episodic silicic eruptions is a feature of central volcano development. The second magma is a younger, high-Nb rhyolite that was erupted episodically between 250 and 68 ka in the northern part of Kerlingarfjöll, forming two clusters, both of which have areas of intense hydrothermal activity. Repose periods for rhyolite volcanism are thought to be on the order of tens of thousands of years, and it is possible that Kerlingarfjöll will erupt rhyolite again in the future.  相似文献   

Glacier reconstruction and mass‐balance modelling as a geomorphic and palaeoclimatic tool     

Simon J. Carr  Sven Lukas  Stephanie C. Mills 《地球表面变化过程与地形》2010,35(9):1103-1115

The reconstruction of former mountain glaciers has long been used to examine the implications of rapid climate shifts, for example at the last glacial–interglacial transition, and for evaluating asynchronous behaviour of mountain glaciers compared with mid‐latitude ice sheets during the Late Quaternary. Glacier reconstruction has also been used as a source of palaeoclimatic information, based on the recognition of empirical relationships between glaciers and climate. This paper reviews the application and implications of a recently revised method of glacier reconstruction (Carr and Coleman, 2007 ), based around glaciological principles of mass‐balance. This study examines how this approach can be used to test geomorphological interpretations of former mountain glaciation and also to infer precipitation fields at sites of former glaciation. Sites of Younger Dryas niche and icefield glaciation in the British Isles demonstrate how this method can verify interpretations of marginal glaciation and begin to understand the different behaviour of outlet glaciers within the same environmental regime. Examination of a site of former niche glaciation in Southern Africa demonstrates how glacier reconstruction may be used to infer annual and seasonal precipitation values and strongly supports the idea that winter precipitation in Lesotho and SE South Africa was substantially greater than present‐day values during the last glacial cycle. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Southern hemispheric westerlies control the spatial distribution of modern sediments in Laguna Potrok Aike,Argentina     

Stephanie Kastner  Christian Ohlendorf  Torsten Haberzettl  Andreas Lücke  Christoph Mayr  Nora I. Maidana  Frank Schäbitz  Bernd Zolitschka 《Journal of Paleolimnology》2010,44(4):887-902

We studied the internal lake processes that control the spatial distribution and characteristics of modern sediments at the ICDP (International Continental Scientific Drilling Program) deep drilling site in Laguna Potrok Aike, southern Patagonia, Argentina. Sediment distribution patterns were investigated using a dense grid of 63 gravity cores taken throughout the lake basin and 40 additional shoreline samples. Analysis of the surficial sediment distribution points to distinct internal depositional dynamics induced by wind-driven lake internal currents. Distribution maps illustrate that the spatial characteristics of analysed variables are linked to high erosional wave activity. Persistent wave action and littoral erosion along all shores, especially the eastern shore, is caused by prevailing Southern Hemispheric Westerlies. Several sediment variables (grain size, benthic diatoms, total inorganic carbon and calcium) indicate re-suspension of littoral sediment followed by re-distribution to profundal accumulation areas near the eastern shore. Variations within the catchment influence sediment characteristics in the north-eastern bay. That area is characterized by different mineralogical and sedimentological conditions as well as greater accumulation of pollen, inorganic carbon and diatoms. These findings are related to the influence of episodic inflow into this bay. Spatial differences in stable isotope values throughout the lake suggest that ephemeral tributaries around the lake basin may also contribute to the detected spatial sediment variations.  相似文献   

Geochemical tracers to evaluate hydrogeologic controls on river salinization     

Moore SJ  Bassett RL  Liu B  Wolf CP  Doremus D 《Ground water》2008,46(3):489-501

The salinization of rivers, as indicated by salinity increases in the downstream direction, is characteristic of arid and semiarid regions throughout the world. Historically, salinity increases have been attributed to various mechanisms, including (1) evaporation and concentration during reservoir storage, irrigation, and subsequent reuse; (2) displacement of shallow saline ground water during irrigation; (3) erosion and dissolution of natural deposits; and/or (4) inflow of deep saline and/or geothermal ground water (ground water with elevated water temperature). In this study, investigation of salinity issues focused on identification of relative salinity contributions from anthropogenic and natural sources in the Lower Rio Grande in the New Mexico-Texas border region. Based on the conceptual model of the system, the various sources of water and, therefore, salinity to the Lower Rio Grande were identified, and a sampling plan was designed to characterize these sources. Analysis results for boron (delta(11)B), sulfur (delta(34)S), oxygen (delta(18)O), hydrogen (delta(2)H), and strontium ((87)Sr/(86)Sr) isotopes, as well as basic chemical data, confirmed the hypothesis that the dominant salinity contributions are from deep ground water inflow to the Rio Grande. The stable isotopic ratios identified the deep ground water inflow as distinctive, with characteristic isotopic signatures. These analyses indicate that it is not possible to reproduce the observed salinization by evapotranspiration and agricultural processes alone. This investigation further confirms that proper application of multiple isotopic and geochemical tracers can be used to identify and constrain multiple sources of solutes in complex river systems.  相似文献   

The planet formation imager     

John D. Monnier  Stefan Kraus  Michael J. Ireland  Fabien Baron  Amelia Bayo  Jean-Philippe Berger  Michelle Creech-Eakman  Ruobing Dong  Gaspard Duchêne  Catherine Espaillat  Chris Haniff  Sebastian Hönig  Andrea Isella  Attila Juhasz  Lucas Labadie  Sylvestre Lacour  Stephanie Leifer  Antoine Merand  Ernest Michael  Stefano Minardi  Christoph Mordasini  David Mozurkewich  Johan Olofsson  Claudia Paladini  Romain Petrov  Jörg-Uwe Pott  Stephen Ridgway  Stephen Rinehart  Keivan Stassun  Jean Surdej  Theo ten Brummelaar  Neal Turner  Peter Tuthill  Kerry Vahala  Gerard van Belle  Gautam Vasisht  Ed Wishnow  John Young  Zhaohuan Zhu 《Experimental Astronomy》2018,46(3):517-529

The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H₂O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality.  相似文献   

Proportion of Sewage Sludge to Soil Influences the Survival of Salmonella Dublin and Escherichia coli          下载免费PDF全文

Stephanie Ellis  Sean Tyrrel  Emma O'Leary  Karl Richards  Bryan Griffiths  Karl Ritz 《洁净——土壤、空气、水》2018,46(4)

  相似文献   

A study case of bioluminescence potential dynamics in the Delaware Bay with observations and modeling     

Igor Shulman  Mark A. Moline  Stephanie Anderson  Peter Sakalaukus  Clark Rowley  Sherwin Ladner 《Ocean Dynamics》2017,67(3-4):383-396