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Catherine Robin Shannon Nudds Phillip MacAulay André Godin Bodo De Lange Boom Jason Bartlett 《Marine Geodesy》2016,39(2):195-222
Since the advent of Global Navigation Satellite Systems, it has been possible to perform hydrographic survey reductions through the ellipsoid, which has the potential to simplify operations and improve bathymetric products. This technique requires a spatially continuous separation surface connecting chart datum (CD) to a geodetic ellipsoid. The Canadian Hydrographic Service (CHS), with support from the Canadian Geodetic Survey, has developed a new suite of such surfaces, termed Hydrographic Vertical Separations Surfaces, or HyVSEPs, for CD and seven tidal levels. They capture the spatial variability of the tidal datum and levels between tide gauges and offshore using semiempirical models coupling observations at tide stations with relative sea-level rise estimates, dynamic ocean model solutions, satellite altimetry, and a geoid model. HyVSEPs are available for all tidal waters of Canada, covering over seven million square kilometers of ocean and more than 200,000 kilometers of shoreline. This document provides an overview of the CHS's modeling approach, tools, methods, and procedures.
The HyVSEP for CD defines the new hydrographic datum for the tidal waters of Canada. HyVSEPs for other tidal levels are fundamental for coastal studies, climate change adaptation and the definition of the Canadian shoreline and offshore boundaries. HyVSEPs for inland waters are not discussed. 相似文献
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Virender K. Sharma Aurelie Moulin Frank J. Millero Concetta De Stefano 《Marine Chemistry》2006,99(1-4):52
The dissociation constants (pK1, pK2 and pK3) for cysteine have been measured in seawater as a function of temperature (5 to 45 °C) and salinity (S = 5 to 35). The seawater values were lower than the values in NaCl at the same ionic strength. In an attempt to understand these differences, we have made measurements of the constants in Na–Mg–Cl solutions at 25 °C. The measured values have been compared to those calculated from the Pitzer ionic interaction model. The lower values of pK3 in the Na–Mg–Cl solutions have been attributed to the formation of Mg2+ complexes with Cys2− anionsThe stability constants have been fitted toafter corrections are made for the interaction of Mg2+ with H+.The pK1 seawater measurements indicate that H3Cys+ interacts with SO42−. The Pitzer parameters β0(H3CysSO4), β1(H3CysSO4) and C(H3CysSO4) have been determined for this interaction. The formation of CaCys as well as MgCys are needed to account for the values of pK2 and pK3 in seawater.The consideration of the formation of MgCys and CaCys in seawater yields model calculated values of pK1, pK2 and pK3 that agree with the measured values to within the experimental error of the measurements. This study shows that it is important to consider all of the ionic interactions in natural waters when examining the dissociation of organic acids. 相似文献
Mg2+ + Cys2− = MgCys
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We analyze the dependence of climatic variations of the location of the upper boundary of the hydrogen-sulphide zone in the
Black Sea on the variations of the sea level and various types of atmospheric circulation (according to A.A. Girs). It is
discovered that the level of correlation between the indicated parameters is high and that the corresponding plots are in
good qualitative agreement. The accumulated results enable us to make an assumption that there exists an 80–100-yr cycle of
variation of all analyzed parameters and that the long-term variations of the location of the upper boundary of the hydrogen-sulphide
zone can be regarded as a manifestation of global climatic variations.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
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The possibility to apply natural acoustic ocean noise in the ocean and noise of distant vessels as sounding signals in order to determine the physical parameters of a water layer is considered in this paper. We developed the methods making it possible to suppress the non-diffuse components of noise produced, e.g., by local vessels and to account for hydrophone motion. These methods are applied to the noise records obtained in the course of a year-long experiment on long-range sound propagation in the Pacific Ocean. We confirmed experimentally our theoretical predictions as to the possibility of retrieving deterministic acoustic ray travel times in a nonuniform environment from a mutual correlation function of imperfectly diffuse (gradually anisotropic and spatially nonuniform) noise without invoking any data on its source. We performed passive measurements of sound velocity in the ocean with a relative error of about 0.1% by correlation of noise fields recorded with vertical aerials. This accuracy approaches that needed for oceanological applications. Further investigations are necessary to study the feasibility of passive acoustic tomography and thermometry in the ocean at distances of tens and hundreds of kilometers and the possibility to use simpler arrays not equipped with hydrophone positioning systems. 相似文献
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Hossein Ghaffarian Hervé Piégay Diego Lopez Nicolas Rivière Bruce MacVicar Aurelie Antonio Emmanuel Mignot 《地球表面变化过程与地形》2020,45(10):2219-2234
Wood in rivers plays a major role both ecologically and morphologically. In recent decades, due to human activities in the river channels and along the riparian zone, wood obstruction and jamming has exacerbated flooding hazards and infrastructure damage. Therefore, it is necessary to quantify the wood flux and discharge in rivers to improve wood hazard management. Among the various methods for monitoring the wood flux in a river, the streamside videography technique is effective given its high temporal and spatial resolution. Previous work monitored the wood discharge (m3/s) using this technique in the Ain River (France) during three floods (MacVicar and Piégay, 2012), and the same method is implemented on the Isère River (France) to obtain the statistics of wood discharge for two floods. Comparison between the two sites supports the generalization of both the monitoring technique and the link between wood discharge and flood characteristics. We first show that the maximum wood discharge is observed at bankfull discharge, and we confirm the three stage model proposed by MacVicar and Piégay (2012). Additionally, transverse distributions of the number of wood pieces and corresponding wood length appear to be similar for different flood magnitudes on each site. As a technical contribution, the use of the same technique on two sites allows for recommendations on key decisions related to the location and implementation of the equipment. Both statistical and technical contributions can be used by decision makers to implement this monitoring technique, acquire the wood transport parameters, and evaluate the potential wood hazards at local scale or along a river. © 2020 John Wiley & Sons, Ltd. 相似文献
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Mapping combined with structural analyses in the foreland edge of the metamorphic core of the Himalayas in SW Nepal highlights the existence of two north‐dipping shear zones with opposite sense of shear. Here, the metamorphic core is mainly affected by non‐coaxial top‐to‐the‐south sense of shear at temperatures between 450 °C and 550 °C that switch to a top‐to‐the‐north sense of shear at the top of the metamorphic core. We regionally correlate this upper shear zone with the South Tibetan detachment system. Ar‐dating on white mica indicates that both shear zones operated between 23 Ma and 17 Ma. Restoration of the folded South Tibetan detachment in far western Nepal yields a minimum dip‐slip distance of 190 km, compatible with predictions made by models of extrusion of a weak mid‐crustal channel. Our results support an orogenic model in which channel flow in the hinterland coexisted with thrust wedge mechanics in the foreland. 相似文献
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Fractured archaeological glass blocks altered 1800 years in seawater are investigated because of their morphological analogy with vitrified nuclear waste. They provide an opportunity for understanding glass alteration in variable confined media (cracks), by studying an actual ancient system in a known stable natural environment. Characterization of the crack network from two-dimensional trace maps (length, alteration thickness, orientation) allows us to determine the three-dimensional geometric parameters (crack density, fracture ratio) and the percentage of alteration, using stereological relations. This methodology could be applied to nuclear glass. From a representative archaeological glass block, we showed that the surface developed by the cracks is 86 ± 27 times greater than the geometric surface but the volumetric alteration is 12.2 ± 4.1%, which is only 12 times greater than the volumetric alteration of the block periphery (about 1 vol%). This unexpected low value is explained by the large variation of the alteration thicknesses in the different types of cracks in relation with their location in the block. The alteration thickness is usually smaller in the internal zone than in the border zone. The alteration layers resulted from three main mechanisms (interdiffusion, glass dissolution, and secondary phase precipitation) leading to two different alteration products (a sodium-depleted layer and mainly a Mg-smectite). Geometric parameters such as the glass surface area/solution volume ratio and transport parameters (renewal of the alteration solution) strongly affected the glass dissolution kinetics. The confined conditions and the diffusive transport of reactive species favor low alteration kinetics. The precipitation of secondary phases also results in sealing of the cracks. Consequently, although it is not known if subcritical crack growth occurred, internal cracks account for only a minor contribution to the overall alteration. These results improve our understanding of alteration in cracks for assessing the predominant physical and chemical parameters that must be considered in long-term nuclear glass modeling. 相似文献
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