Remote and local forcing of a coastal lagoon: The Virginia Coast Reserve     

Richard P. Mied  William J. Schulz  Robert A. Handler  Charlotte M. Snow  Robert A. Fusina  John H. Porter 《Continental Shelf Research》2010

The effects of local and remote wind forcing of water level heights in the Virginia Coast Reserve (VCR) are examined in order to determine the significant forces governing estuarine motions over subtidal time scales. Recent (1996–2008) data from tide and wind stations in the lagoon, a tide station to the north at Sandy Hook, NJ, and one offshore wind station at the Chesapeake Light Tower are examined. Sea surface height spectrum calculations reveal significant diurnal and semidiurnal tidal effects along with subtidal variations, but a suppressed inertial signal. Sea-surface heights (SSH) with 2–5 day periods at Wachapreague, VA are coherent with those at Sandy Hook and lag them in time, suggesting that southward-propagating continental shelf waves provide subtidal variability within the lagoon. The coherence between lagoon winds and sea surface height, as well as between winds and cross-lagoon sea height gradient, were significant at a relatively small number of frequency and wind direction combinations. The frequencies at which this wind forcing occurs are the tidal and subtidal bands present to the north, so that lagoon winds selectively augment existing SSH signals, but do not generate them. The impact of the wind direction is closely related to the geometry of the lagoon and bounding landmasses. The effect of wind stress is also constrained by geometry in affecting the cross-lagoon water height gradient. Water levels at subtidal frequencies are likely forced by a combination of local wind forcing, remote wind forcing and oceanic forcing modified by the complex topography of the lagoon, shelf, and barrier islands.  相似文献   

Lake ecosystem dynamics and links to climate change inferred from a stable isotope and organic palaeorecord from a mountain lake in southwestern China (ca. 22.6–10.5 cal ka BP)     

Charlotte G. Cook  Melanie J. Leng  Richard T. Jones  Peter G. Langdon  Enlou Zhang 《Quaternary Research》2012,77(1):132-137

A detailed understanding of long-term climatic and environmental change in southwestern China is hampered by a lack of long-term regional palaeorecords. Organic analysis (%TOC, %TN, C/N ratios and δ¹³C values) of a sediment sequence from Lake Shudu, Yunnan Province (ca. 22.6–10.5 cal ka BP) indicates generally low aquatic palaeoproductivity rates over millennial timescales in response to cold, dry climatic conditions. However, the record is punctuated by two marked phases of increased aquatic productivity from ca. 17.7 to 17.1 cal ka BP and from ca. 11.9 to 10.5 cal ka BP. We hypothesise that these shifts reflect a marked, stepwise lacustrine response to Asian summer monsoon strengthening during the last deglaciation.  相似文献   

Earthquake awareness and perception of risk among the residents of Istanbul     

Tekeli-Yeşil  Sıdıka  Dedeoğlu  Necati  Braun-Fahrlaender  Charlotte  Tanner  Marcel 《Natural Hazards》2011,59(1):427-446

Awareness and perception of risk are among the most crucial steps in the process of taking precautions at individual level for various hazards. In this study, we investigated the factors affecting better knowledge and greater risk perception about earthquakes among residents of Istanbul. A field survey was carried out, and a total of 1,123 people were interviewed in two districts of Istanbul with different seismic risk levels and from three (low, moderate and high) socio-economic levels (SEL). The findings showed that although the level of knowledge regarding earthquakes and preparedness for them was promising, it could be improved. The results indicated that future preparedness programmes should target people with lower educational and socio-economic levels. The media were the leading source of information among the respondents. Location of the home was a strong influence on individuals having above average earthquake knowledge and even more on high risk perception. Socio-economic parameters (educational level, economic status, SEL of the sub-district and tenure of the home), gender and attitude score were other factors influencing greater risk perception with regard to earthquakes.  相似文献   

Deposition and early alteration of evaporites   总被引：3，自引：1，他引：2  

B. Charlotte Schreiber  Mohamed El Tabakh† 《Sedimentology》2000,47(S1):215-238

  相似文献   

Deposition and early alteration of evaporites     

B. Charlotte Schreiber  Mohamed El Tabakh 《Sedimentology》2000,47(Z1):215-238

  相似文献   

Style and evolution of salt pillows and related structures in the northern part of the Northeast German Basin     

Dirk Kossow  Charlotte Krawczyk  Tommy McCann  Manfred Strecker  Jörg F.W. Negendank 《International Journal of Earth Sciences》2000,89(3):652-664

The northern part of the Northeast German Basin contains a large number of Late Permian (Zechstein) salt pillows, whereas diapiric structures are almost completely absent. This lack of diapirs facilitated the study of early stages of salt movement in the basin. Salt pillows and related structures were investigated in terms of distribution, geometry and time of initiation of salt flow within the regional geological context. The primary Zechstein thickness in the study area was reconstructed to gain more insight into the relationship between the geometry of the salt layer and the style of the salt-related structures. In this study, no clear spatial relationship between the salt structures and basement faults has been found and the location of the salt structures in this area appears to be highly independent of the underlying structural grain. The overburden is affected by minor faulting. We propose that buckling of the overburden due to regional compression significantly contributed to the initiation of the Late Jurassic to Early Cretaceous salt structures in the basin. Reverse faulting of the Gardelegen and Haldensleben Faults is related to inversion tectonics and exerted a compression on the basin fill. During the deformation, the Late Permian salt layer acted as an efficient detachment and led to a marked decoupling of the Mesozoic overburden from the underlying pre-Zechstein rocks.  相似文献   

The Use of LiDAR in Digital Surface Modelling: Issues and Errors     

Charlotte L Leigh  David B Kidner  Malcolm C Thomas 《Transactions in GIS》2009,13(4):345-361

Modelling and extracting 3D geographical data presents numerous challenges that require continual research to attempt to evolve an efficient, reliable and accurate solution. LiDAR data capture and analysis has become a preferred acquisition choice for elevation data because the resulting quality and level of detail far exceeds traditional methods for large survey areas. As with any data collection system, LiDAR is prone to errors. Analysing these errors, ascertaining causes and producing error correction strategies is vital if accurate and confident results are to be obtained. Eight years of LiDAR datasets (from 1998 to 2005) have been closely analysed for a large coastal area of South Wales. This article provides a detailed and accurate summary of the identified LiDAR data issues and subsequent errors which affect the accuracy of end products such as Digital Surface Models (DSMs).  相似文献   

Importance of geological information for assessing drain flow in a Danish till landscape     

Anne Lausten Hansen  Anne Storgaard  Xin He  Anker Lajer Hjberg  Jens Christian Refsgaard  Bo Vangs Iversen  Charlotte Kjaergaard 《水文研究》2019,33(3):450-462

There has, in recent years, been an increasing interest in developing nutrient load mitigation measures focussing on tile drains. To plan the location of such tile drain measures, it is important to know where in the landscape drain flow is generated and to understand the key factors governing drain flow dynamics. In the present study, we test two approaches to assess spatial patterns in drain flow generation and thereby assess the importance of including geological information. The approaches are the widely used topographical wetness index (TWI), based solely on elevation data, and hydrological models that include the subsurface geology. We set‐up an ensemble of 20 hydrological models based on 20 stochastically generated geological models to predict drain flow dynamics in the clay till Norsminde catchment in Denmark and test the results against TWI. We find that the hydrological models predict observed daily drain flow reasonably well. High drain flow volumes were found in stream valleys and in wetlands and lower drain flow volumes in the more hilly parts of the catchment. In spite of the apparent connection to the landscape, there was no statistically significant correlation between TWI and drain flow at grid scale (100 × 100 m). TWI was therefore not found to be a sufficient index on its own to assess where drain flow is generated, especially in the highlands of the catchment. The geology below 3 m was found to have a large impact on the drain flow, and correlations between sand percentage in the subsurface geology and drain flow volume were found to be statistically significant. Geological uncertainty therefore give rise to uncertainty on simulated drain flow, and this uncertainty was found to be high at the model grid scale but decreasing with increasing scale.  相似文献   

Sources and biological fractionation of Silicon isotopes in the Eastern Equatorial Pacific   总被引：1，自引：0，他引：1  

Charlotte P. Beucher  Mark A. Brzezinski  Janice L. Jones 《Geochimica et cosmochimica acta》2008,72(13):3063-3073

Silicon isotopes in dissolved silicic acid were measured in the upper four kilometers between 4°N and 3°S latitude at 110°W longitude in the eastern Equatorial Pacific. Silicon isotopes became progressively heavier with silicic acid depletion of surface water as expected from biological fractionation. The value of ε estimated by applying a steady-state isotope fractionation model to data from all stations between 4°N and 3°S was −0.77 ± 0.12‰ (std. err.). When the analysis was restricted to those stations whose temperature and salinity profiles indicated that they were directly influenced by upwelling of the Equatorial Undercurrent (EUC), the resulting value of ε was −1.08 ± 0.27‰ (std. err.) similar to the value established in culture studies (−1.1‰). When the non steady state Rayleigh model was applied to the same restricted data set the resulting value of ε was significantly more positive, −0.61 ± 0.16‰ (std. err.). To the extent that the equatorial system approximates a steady state these results support a value of −1.1‰ for the fractionation factor for isotopes of Si in the sea. Without the assumption of steady state the value of ε can only be constrained to be between −0.6 and −1.1‰. Silicic acid in Equatorial Pacific Deep Water below 2000 m had a near constant δ³⁰Si of +1.32 ± 0.05‰. That value is significantly more positive than obtained for North Pacific Deep Water at similar depths at stations to the northwest of our study area (0.9-1.0‰) and it is slightly less positive than new measures of the δ³⁰Si of silicic acid from the silicic acid plume centered over the Cascadia basin in the Northeast Pacific (Si(OH)₄ > 180  μM, δ³⁰Si = +1.46 ± 0.12‰ (SD, n = 4). We show that the data from the equator and Cascadia basin fit a general trend of increasing δ³⁰Si(OH)₄ with increasing silicic acid concentration in the deep sea, but that the isotope values from the Northeast Pacific are anomalously light. The observed level of variation in the silicon isotope composition of deep waters from this single ocean basin is considerably larger than that predicted by current models based on fractionation during opal formation with no isotope effect during dissolution. Confirmation of such high variability in deep water δ³⁰Si(OH)₄ within individual ocean basins will require reassessment of the mechanisms controlling the distribution of isotopes of silicon in the sea.  相似文献   

Regional Fluxes Of Momentum And Sensible Heat Over A Sub-Arctic Landscape During Late Winter     

Ekaterine Batchvarova  Svan-Erik Gryning  Charlotte Bay Hasager 《Boundary-Layer Meteorology》2001,99(3):489-507

Based on measurements at Sodankylä Meteorological Observatory the regional (aggregated) momentum and sensible heat fluxes are estimated for two days over a site in Finnish Lapland during late winter. The forest covers 49% of the area. The study shows that the forest dominates and controls the regional fluxes of momentum and sensible heat in different ways. The regional momentum flux is found to be 10–20% smaller than the measured momentum flux over the forest, and the regional sensible heat flux is estimated to be 30–50% of the values measured over a coniferous forest.The regional momentum flux is determined in two ways, both based on blending height theory. One is a parameterised method, the other represents a numerical solution of an aggregation model. The regional sensible heat flux is determined from the theory of mixed-layer growth. At near neutral conditions the regional momentum flux can be determined independently of the regional sensible heat flux. At unstable conditions the two models become coupled.The information that is needed by the parameterised blending height method and by the mixed-layer evolution method in order to derive the regional fluxes of momentum and sensible heat can be obtained from radiosonde profiles of wind speed and temperature.  相似文献