Detecting changing river temperatures in England and Wales          下载免费PDF全文

Harriet G. Orr  Gavin L. Simpson  Sophie des Clers  Glenn Watts  Mike Hughes  Jamie Hannaford  Michael J. Dunbar  Cédric L. R. Laizé  Rob L. Wilby  Richard W. Battarbee  Rob Evans 《水文研究》2015,29(5):752-766

Changes in water temperature can have important consequences for aquatic ecosystems, with some species being sensitive even to small shifts in temperature during some or all of their life cycle. While many studies report increasing regional and global air temperatures, evidence of changes in river water temperature has, thus far, been site specific and often from sites heavily influenced by human activities that themselves could lead to warming. Here we present a tiered assessment of changing river water temperature covering England and Wales with data from 2773 locations. We use novel statistical approaches to detect trends in irregularly sampled spot measurements taken between 1990 and 2006. During this 17‐year period, on average, mean water temperature increased by 0.03 °C per year (±0.002 °C), and positive changes in water temperature were observed at 2385 (86%) sites. Examination of catchments where there has been limited human influence on hydrological response shows that changes in river flow have had little influence on these water temperature trends. In the absence of other systematic influences on water temperature, it is inferred that anthropogenically driven climate change is driving some of this trend in water temperature. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.  相似文献   

High concentrations of amorphous,biogenic Si (BSi) in the sediment of a small high-latitude lake: implications for biogeochemical Si cycling and for the use of BSi as a paleoproxy     

Petra Tallberg  Sophie Opfergelt  Jean-Thomas Cornelis  Anne Liljendahl  Jan Weckström 《Aquatic Sciences - Research Across Boundaries》2015,77(2):293-305

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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   

Tropical peatlands: current plight and the need for responsible management          下载免费PDF全文

Sophie M. Green  Susan Page 《Geology Today》2017,33(5):174-179

Peatlands are important carbon stores, but when drained (e.g. for agriculture), this carbon is released to the atmosphere as carbon dioxide (CO₂, a greenhouse gas). Globally, at least 15% of peatlands have been drained, mostly in Europe and South‐east Asia, and are responsible for 5% of human‐derived CO₂ emissions. Peatlands have been exploited for generations, but not without local to global consequences, particularly in South‐East Asia. However, recognition of the continuous environmental toll caused by peatland exploitation is leading to a need to change attitudes and practices, in order to propel a move towards a more balanced and responsible use of peat in both northern and tropical peatlands.  相似文献   

Reconstruction or dislocation: Barnes or Sayer on the political economy of space?     

Keith Bassett 《Geoforum》1996,27(4):453-460

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Hydrothermal studies in a new diamond anvil cell up to 10 GPa and from −190°C to 1200°C     

W. A. Bassett  A. H. Shen  M. Bucknum  I-Ming Chou 《Pure and Applied Geophysics》1993,141(2-4):487-495

The new hydrothermal diamond anvil cell (HDAC) has been designed for optical microscopy and X-ray diffraction at pressures up to 10 GPa and temperatures between –190°C and 1200°C. Laser light reffected from the top and bottom anvil faces and the top and bottom solid sample faces produce interference fringes that provide a very sensitive means of monitoring the volume of sample chamber and for observing volume and refractive index changes in solid samples due to transitions and reactions. Synchrotron radiation has been used to make X-ray diffraction patterns of samples under hydrothermal conditions. Individual heaters and individual thermocouples provide temperature control with an accuracy of ±0.5°C. Liquid nitrogen directly introduced into the HDAC has been used to reduce the sample temperature to –190°C. The - phase boundary of quartz has been used to calculate the transition pressures from measured transition temperatures. With this method we have redetermined 5 isochores of H₂O up to 850°C and 1.2 GPa at which the solution rate of the quartz became so rapid that the quartz dissolved completely before the - transition could be observed. When silica solutions were cooled, opal spherules and rods formed.  相似文献   

Temperature And Wind Velocity Oscillations Along a Gentle Slope During Sea-Breeze Events     

Sophie?BastinEmail author  Philippe?Drobinski 《Boundary-Layer Meteorology》2005,114(3):573-594

The flow structure on a gentle slope at Vallon dOl in the northern suburbs of Marseille in southern France has been documented by means of surface wind and temperature measurements collected from 7 June to 14 July 2001 during the ESCOMPTE experiment. The analysis of the time series reveals temperature and wind speed oscillations during several nights (about 60--90 min oscillation period) and several days (about 120–180 min oscillation period) during the whole observing period. Oscillating katabatic winds have been reported in the literature from theoretical, experimental and numerical studies. In the present study, the dynamics of the observed oscillating katabatic winds are in good agreement with the theory.In contrast to katabatic winds, no daytime observations of oscillating anabatic upslope flows have ever been published to our knowledge, probably because of temperature inversion break-up that inhibits upslope winds. The present paper shows that cold air advection by a sea breeze generates a mesoscale horizontal temperature gradient, and hence baroclinicity in the atmosphere, which then allows low-frequency oscillations, similar to a katabatic flow. An expression for the oscillation period is derived that accounts for the contribution of the sea-breeze induced mesoscale horizontal temperature gradient. The theoretical prediction of the oscillation period is compared to the measurements, and good agreement is found. The statistical analysis of the wind flow at Vallon dOl shows a dominant north-easterly to easterly flow pattern for nighttime oscillations and a dominant south-westerly flow pattern for daytime oscillations. These results are consistent with published numerical simulation results that show that the air drains off the mountain along the maximum slope direction, which in the studied case is oriented south-west to north-east.  相似文献   

Residential mobility trajectories and integration in Douala and Bafoussam,Cameroon     

Aristide Yemmafouo  Chrétien Ngouanet  Romeo Keumo Songong  Nicodème Djikeng Teufack  Sophie Ariane Djuidje 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(2):105-116

Abstract

This study examines how migrant households relocate their homes in two Cameroonian cities over the course of lifetimes or even generations. The central claim is that homeownership is the ultimate sign of integration into city life. Using qualitative and quantitative research methods (218 interviews, 30 focus groups and a household survey, sample size 686), the study argues that three key factors explain why people move: the quality of housing they can affords, the proximity to a workplace and the potential for homeownership. Three residential model trajectories are identified. The first describes a journey from being a new migrant who is a guest of family or friends in the city centre to being a married family with kids owning a home in the urban periphery. The second model continues that journey by returning back to the city centre in pursuit of more convenient, high-status home location (if finances permit). A third model describes moves to sites all over the city later in life as older individuals seek to maximize family income in the way they use multiple properties. Understanding residential mobility patterns has the potential to lead to a better public policies and more effective private investments in the housing sector.  相似文献   

Dynamics of a wave-dominated tidal inlet and influence on adjacent beaches,Currumbin Creek,Gold Coast,Australia     

Bruno Castelle  Julien Bourget  Nathalie Molnar  Darrell Strauss  Sophie Deschamps  Rodger Tomlinson 《Coastal Engineering》2007

Currumbin Creek on the Australian Gold Coast is a wave-dominated tidal inlet which exhibits a particularly active morphology. The recent history of Currumbin Creek entrance has seen rapid growth of the entrance for access to the ocean by fishermen, as a world class surfing site, and as a recreational area. Before the construction of two groynes in the 70's, Currumbin Creek entrance was highly variable in terms of inlet location and sand bar characteristics due to a cyclical behaviour of spit migration. Nowadays, the entrance is stabilised. However, natural processes continue with the entrance infilling causing flood and navigation issues, resulting in a regular dredging program to maintain an open entrance and for regular beach nourishment plans.  相似文献   

Habitats and Characteristics of the Sea Urchins Lytechinus variegatus and Arbacia punctulata (Echinodermata) on the Florida Gulf-Coast Shelf     

Sophie K. Hill  & John M. Lawrence 《Marine Ecology》2003,24(1):15-30

Abstract Lytechinus variegatus and Arbacia punctulata have been studied primarily in inshore, shallow‐water areas. However, they are abundant in deeper waters on the Florida gulf‐coast shelf and seem important components of the benthic communities there. Lytechinus variegatus occurs alone on sand bottoms and A. punctulata occurs alone on rubble bottoms in these deeper waters. The species also co‐occur there on ­heterogeneous bottoms, each in a distinct microhabitat with A. punctulata on rubble and L. variegatus on surrounding sand. Characteristics of the sea urchins in these different deeper‐water habitat types and at one nearshore site with a heterogeneous rubble‐sand bottom were compared. Over the 2‐year study, offshore individuals of both species had low gut and gonad indices and the maximum size of individuals did not change. This suggests food limitation and low production. Offshore, A. punctulata had a higher Aristotle's lantern index and lower gut and gonad indices in populations where it ­co‐occurred with L. variegatus compared to populations where it occurred alone. The ­Aristotle's lantern index of L. variegatus did not differ among the offshore sites. Neither species seemed food limited at the nearshore site. Although productivity is lower at the offshore sites, both species extend their distribution and reproduction potential by existing there.  相似文献