Importance of Biogeomorphic and Spatial Properties in Assessing a Tidal Salt Marsh Vulnerability to Sea-level Rise     

Karen M. Thorne  Deborah L. Elliott-Fisk  Glenn D. Wylie  William M. Perry  John Y. Takekawa 《Estuaries and Coasts》2014,37(4):941-951

We evaluated the biogeomorphic processes of a large (309 ha) tidal salt marsh and examined factors that influence its ability to keep pace with relative sea-level rise (SLR). Detailed elevation data from 1995 and 2008 were compared with digital elevation models (DEMs) to assess marsh surface elevation change during this time. Overall, 37 % (113 ha) of the marsh increased in elevation at a rate that exceeded SLR, whereas 63 % (196 ha) of the area did not keep pace with SLR. Of the total area, 55 % (169 ha) subsided during the study period, but subsidence varied spatially across the marsh surface. To determine which biogeomorphic and spatial factors contributed to measured elevation change, we collected soil cores and determined percent and origin of organic matter (OM), particle size, bulk density (BD), and distance to nearest bay edge, levee, and channel. We then used Akaike Information Criterion (AICc) model selection to assess those variables most important to determine measured elevation change. Soil stable isotope compositions were evaluated to assess the source of the OM. The samples had limited percent OM by weight (<5.5 %), with mean bulk densities of 0.58 g cm^-3, indicating that the soils had high mineral content with a relatively low proportion of pore space. The most parsimonious model with the highest AICc weight (0.53) included distance from bay's edge (i.e., lower intertidal) and distance from levee (i.e., upper intertidal). Close proximity to sediment source was the greatest factor in determining whether an area increased in elevation, whereas areas near landward levees experienced subsidence. Our study indicated that the ability of a marsh to keep pace with SLR varied across the surface, and assessing changes in elevation over time provides an alternative method to long-term accretion monitoring. SLR models that do not consider spatial variability of biogeomorphic and accretion processes may not correctly forecast marsh drowning rates, which may be especially true in modified and urbanized estuaries. In light of SLR, improving our understanding of elevation change in these dynamic marsh systems will play a crucial role in forecasting potential impacts to their sustainability and the survival of these ecosystems.  相似文献   

The Awa Book of New Zealand Science – Edited by Rebecca Priestley     

George Perry 《New Zealand geographer》2010,66(2):169-170

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Pulse-length-tolerant features and detectors for sector-scan sonar imagery     

Perry  S.W. Ling Guan 《Oceanic Engineering, IEEE Journal of》2004,29(1):138-156

This paper presents a neural-network-based system to detect small man-made objects in sequences of sector-scan sonar images created using signals of various pulse lengths. The detection of such objects is considered out to ranges of 150 m by using an experimental sector-scan sonar system mounted on a vessel. The sonar system considered in this investigation has three modes of operation to create images over ranges of 200, 400, and 800 m from the vessel using acoustic pulses of a different duration for each mode. After an initial cleaning operation performed by compensating for the motion of the vessel, the imagery is segmented to extract objects for analysis. A set of 31 features extracted from each object is examined. These features consist of basic object size and contrast features, shape moment-based features, moment invariants, and features extracted from the second-order histogram of each object. Optimal sets of 15 features are then selected for each mode and over all modes using sequential forward selection (SFS) and sequential backward selection (SBS). These features are then used to train neural networks to detect man-made objects in each sonar mode. By the addition of a feature describing the sonar's mode of operation, a neural network is trained to detect man-made objects in any of the three sonar modes. The multimode detector is shown to perform very well when compared with detectors trained specifically for each sonar mode setting. The proposed detector is also shown to perform well when compared to a number of statistical detectors based on the same set of features. The proposed detector achieves a 92.4% probability of detection at a mean false-alarm rate of 10 per image, averaged over all sonar mode settings.  相似文献   

Recent Experimental Results and Modelling of High-Mach-Number Jets and the Transition to Turbulence     

P. A. Rosen  B. H. Wilde  R. J. R. Williams  J. M. Foster  P. A. Keiter  R. F. Coker  T. S. Perry  M. J. Taylor  A. M. Khokhlov  R. P. Drake  G. R. Bennett  D. B. Sinars  R. B. Campbell 《Astrophysics and Space Science》2005,298(1-2):121-128

In recent years, we have carried out experiments at the University of Rochester’s Omega laser in which supersonic, dense-plasma jets are formed by the interaction of strong shocks in a complex target assembly (Foster et al., Phys. Plasmas 9 (2002) 2251). We describe recent, significant extensions to this work, in which we consider scaling of the experiment, the transition to turbulence, and astrophysical analogues. In new work at the Omega laser, we are developing an experiment in which a jet is formed by laser ablation of a titanium foil mounted over a titanium washer with a central, cylindrical hole. Some of the resulting shocked titanium expands, cools, and accelerates through the vacuum region (the hole in the washer) and then enters a cylinder of low-density foam as a jet. We discuss the design of this new experiment and present preliminary experimental data and results of simulations using AWE hydrocodes. In each case, the high Reynolds number of the jet suggests that turbulence should develop, although this behaviour cannot be reliably modelled by present, resolution-limited simulations (because of their low-numerical Reynolds number).  相似文献   

Andrew Porteous, Dictionary of Environmental Science andTechnology, 3rd edition     

J.S. Perry 《Climatic change》2002,52(1-2):243-244

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A multidisciplinary-based conceptual model of a fractured sedimentary bedrock aquitard: improved prediction of aquitard integrity     

Anthony C. Runkel  Robert G. Tipping  Jessica R. Meyer  Julia R. Steenberg  Andrew J. Retzler  Beth L. Parker  Jeff A. Green  John D. Barry  Perry M. Jones 《Hydrogeology Journal》2018,26(7):2133-2159

A hydrogeologic conceptual model that improves understanding of variability in aquitard integrity is presented for a fractured sedimentary bedrock unit in the Cambrian-Ordovician aquifer system of midcontinent North America. The model is derived from multiple studies on the siliciclastic St. Lawrence Formation and adjacent strata across a range of scales and geologic conditions. These studies employed multidisciplinary techniques including borehole flowmeter logging, high-resolution depth-discrete multilevel well monitoring, fracture stratigraphy, fluorescent dye tracing, and three-dimensional (3D) distribution of anthropogenic tracers regionally. The paper documents a bulk aquitard that is highly anisotropic because of poor connectivity of vertical fractures across matrix with low permeability, but with ubiquitous bed parallel partings. The partings provide high bulk horizontal hydraulic conductivity, analogous to aquifers in the system, while multiple preferential termination horizons of vertical fractures serve as discrete low vertical hydraulic conductivity intervals inhibiting vertical flow. The aquitard has substantial variability in its ability to protect underlying groundwater from contamination. Across widespread areas where the aquitard is deeply buried by younger bedrock, preferential termination horizons provide for high aquitard integrity (i.e. protection). Protection is diminished close to incised valleys where stress release and weathering has enhanced secondary pore development, including better connection of fractures across these horizons. These conditions, along with higher hydraulic head gradients in the same areas and more complex 3D flow where the aquitard is variably incised, allow for more substantial transport to deeper aquifers. The conceptual model likely applies to other fractured sedimentary bedrock aquitards within and outside of this region.  相似文献   

Mid-Holocene vertebrate bone Concentration-Lagerstätte on oceanic island Mauritius provides a window into the ecosystem of the dodo (Raphus cucullatus)     

Kenneth F. Rijsdijk  Julian P. Hume  Frans Bunnik  F.B. Vincent Florens  Claudia Baider  Beth Shapiro  Johannes van der Plicht  Anwar Janoo  Owen Griffiths  Lars W. van den Hoek Ostende  Holger Cremer  Tamara Vernimmen  Perry G.B. De Louw  Assenjee Bholah  Salem Saumtally  Nicolas Porch  James Haile  Mike Buckley  Matthew Collins  Edmund Gittenberger 《Quaternary Science Reviews》2009,28(1-2):14-24

Although the recent history of human colonisation and impact on Mauritius is well documented, virtually no records of the pre-human native ecosystem exist, making it difficult to assess the magnitude of the changes brought about by human settlement. Here, we describe a 4000-year-old fossil bed at Mare aux Songes (MAS) in south-eastern Mauritius that contains both macrofossils (vertebrate fauna, gastropods, insects and flora) and microfossils (diatoms, pollen, spores and phytoliths). With >250 bone fragments/m² and comprising 50% of all known extinct and extant vertebrate species (n_s = 44) of Mauritius, MAS may constitute the first Holocene vertebrate bone Concentration-Lagerstätte identified on an oceanic volcanic island. Fossil remains are dominated by extinct giant tortoises Cylindraspis spp. (63%), passerines (～10%), small bats (7.8%) and dodo Raphus cucullatus (7.1%). Twelve radiocarbon ages [four of them duplicates] from bones and other material suggest that accumulation of fossils took place within several centuries. An exceptional combination of abiotic conditions led to preservation of bones, bone collagen, plant tissue and microfossils. Although bone collagen is well preserved, DNA from dodo and other Mauritian vertebrates has proved difficult. Our analysis suggests that from ca 4000 years ago (4 ka), rising sea levels created a freshwater lake at MAS, generating an oasis in an otherwise dry environment which attracted a diverse vertebrate fauna. Subsequent aridification in the south-west Indian Ocean region may have increased carcass accumulation during droughts, contributing to the exceptionally high fossil concentration. The abundance of floral and faunal remains in this Lagerstätte offers a unique opportunity to reconstruct a pre-human ecosystem on an oceanic island, providing a key foundation for assessing the vulnerability of island ecosystems to human impact.  相似文献   

Improving groundwater resource accounting in irrigated areas : a prerequisite for promoting sustainable use     

S. S. D. Foster  C. J. Perry 《Hydrogeology Journal》2010,18(2):291-294

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Implications for geothermometry of aluminum substitution in quartz from Kings Mountain,North Carolina     

E. C. Perry Jr. 《Contributions to Mineralogy and Petrology》1971,30(2):125-128

The aluminum concentration of quartz from contact-metamorphosed, Al₂SiO₅ bearing quartzite at King's Mountain, North Carolina shows a regular variation with distance from an intrusive contact. Presumably this is the result of temperature-dependent solubility of aluminum in quartz, but critical comparison of these results with other recently published data shows that detailed calibration of this geothermometer has not yet been achieved.  相似文献   

Downstream migration of Geotria australis juveniles in the lower Waikato River (note)     

Perry W. Empson  Adrian S. Meredith 《新西兰海洋与淡水研究杂志》2013,47(4):643-644

Juvenile migrants of Geotria australis were caught from July to early August 1986 in plankton nets set in the lower Waikato River. Migration occurred only at night and mainly mid‐river at the surface. The mean lengths and weights (± 95%c.i.) were 107.75 ± 3.98 mm and 0.94 ± 0.08 g respectively.  相似文献