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Статті в журналах з теми "Water Column Depth (WCD)"
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Nau, Amy, Vanessa Lucieer, Yoann Ladroit, Haris Kunnath, and Tara Martin. "Multibeam sonar water column data simulation for improved and automated detection of gas seeps." Journal of the Acoustical Society of America 154, no. 4_supplement (October 1, 2023): A92—A93. http://dx.doi.org/10.1121/10.0022905.
Повний текст джерелаАнотація:
Water column data (WCD) collected by multibeam echosounders (MBES) provide valuable datasets for the detection of gas bubbles. However, the presence of noise patterns, primarily caused by sidelobe interference from seafloor reverberation, limits the usability of WCD. We present a method for simulating characteristic noise patterns in WCD, particularly in Mills Cross configurations, by simulating predicted seafloor reverberation and transducer artefacts. The simulation is based on a reference pattern created from a subset of data and then applied as a correction based on the depth and seafloor backscatter of each ping within the dataset. Noise patterns can be removed by subtracting the simulated data from the original data, allowing for improved analysis of near-benthic water column features such as gas seeps. This method requires no prior knowledge of specific transducer characteristics, making it applicable to a wide range of MBES systems and acoustic targets. This method was applied to two MBES datasets collected simultaneously over a seep field in the Bay of Plenty, New Zealand, as part of the Quantitative Ocean-Column Imaging (QUOI) voyage in July 2018. We demonstrate the utility of applying a reference pattern for detecting the spatial extent of gas seep bases mapped using two different frequencies.
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Ghannami, Mohamed Ali, Sylvie Daniel, Guillaume Sicot, and Isabelle Quidu. "A Likelihood-Based Triangulation Method for Uncertainties in Through-Water Depth Mapping." Remote Sensing 16, no. 21 (November 2, 2024): 4098. http://dx.doi.org/10.3390/rs16214098.
Повний текст джерелаАнотація:
Coastal environments, which are crucial for economic and strategic reasons, heavily rely on accurate bathymetry for safe navigation and resource monitoring. Recent advancements in through-water photogrammetry have shown promise in mapping shallow waters efficiently. However, robust uncertainty modeling methods for these techniques, especially in challenging coastal environments, are lacking. This study introduces a novel likelihood-based approach for through-water photogrammetry, focusing on uncertainties associated with camera pose—a key factor affecting depth mapping accuracy. Our methodology incorporates probabilistic modeling and stereo-photogrammetric triangulation to provide realistic estimates of uncertainty in Water Column Depth (WCD) and Water–Air Interface (WAI) height. Using simulated scenarios for both drone and airborne surveys, we demonstrate that viewing geometry and camera pose quality significantly influence resulting uncertainties, often overshadowing the impact of depth itself. Our results reveal the superior performance of the likelihood ratio statistic in scenarios involving high attitude noise, high flight altitude, and complex viewing geometries. Notably, drone-based applications show particular promise, achieving decimeter-level WCD precision and WAI height estimations comparable to high-quality GNSS measurements when using large samples. These findings highlight the potential of drone-based surveys in producing more accurate bathymetric charts for shallow coastal waters. This research contributes to the refinement of uncertainty quantification in bathymetric charting and sets a foundation for future advancements in through-water surveying methodologies.
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Lu, Yanhong, Xiaomin Xia, Shunyan Cheung, Hongmei Jing, and Hongbin Liu. "Differential Distribution and Determinants of Ammonia Oxidizing Archaea Sublineages in the Oxygen Minimum Zone off Costa Rica." Microorganisms 7, no. 10 (October 15, 2019): 453. http://dx.doi.org/10.3390/microorganisms7100453.
Повний текст джерелаАнотація:
Ammonia oxidizing archaea (AOA) are microbes that are widely distributed in the ocean that convert ammonia to nitrite for energy acquisition in the presence of oxygen. Recent study has unraveled highly diverse sublineages within the previously defined AOA ecotypes (i.e., water column A (WCA) and water column B (WCB)), although the eco-physiology and environmental determinants of WCB subclades remain largely unclear. In this study, we examined the AOA communities along the water columns (40–3000 m depth) in the Costa Rica Dome (CRD) upwelling region in the eastern tropical North Pacific Ocean. Highly diverse AOA communities that were significantly different from those in oxygenated water layers were observed in the core layer of the oxygen minimum zone (OMZ), where the dissolved oxygen (DO) concentration was < 2μM. Moreover, a number of AOA phylotypes were found to be enriched in the OMZ core. Most of them were negatively correlated with DO and were also detected in other OMZs in the Arabian Sea and Gulf of California, which suggests low oxygen adaptation. This study provided the first insight into the differential niche partitioning and environmental determinants of various subclades within the ecotype WCB. Our results indicated that the ecotype WCB did indeed consist of various sublineages with different eco-physiologies, which should be further explored.
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Vahtmäe, Ele, Tiit Kutser, and Birgot Paavel. "Performance and Applicability of Water Column Correction Models in Optically Complex Coastal Waters." Remote Sensing 12, no. 11 (June 8, 2020): 1861. http://dx.doi.org/10.3390/rs12111861.
Повний текст джерелаАнотація:
Maps of submerged aquatic vegetation (SAV) are of primary importance for the sustainable management of coastal areas and serve as a basis for fundamental ecological studies. Various water column correction (WCC) models are successfully applied in clear Case-1 waters to compensate for the variable water depth effect. The performance of the WCC in less clear Case-2 waters is rarely assessed. In this study, the performance and applicability of model-based WCC algorithms in the complex Baltic Sea were analyzed. The bottom reflectance was retrieved from the Compact Airborne Spectrographic Imager (CASI) water surface reflectance by applying the Maritorena and Lee WCC algorithms. The Maritorena model retrieved bottom spectra that showed large variations in reflectance magnitudes. The Lee model was more successful in retrieving reasonable spectral magnitudes, although only in a rather narrow wavelength region (550–600 nm). Shorter and longer spectral regions were significantly overcorrected, resulting in unrealistic spectral shapes. Sensitivity analysis indicated that slight under- or overestimation of water depth and water column constituents affect retrieval of correct bottom spectra in Case-2 waters. To assess the performance of WCC models in improving the SAV quantification, the surface reflectance, as well as the retrieved bottom reflectance, were correlated with the corresponding in situ estimated SAV percent cover (%SAV). Although the quality of the Lee WCC model was not considered high, the spectral region least affected by the input parameters variations (550–600 nm) can be used for the SAV quantification. Application of the Lee model provided better results in %SAV assessment than not performing the WCC correction.
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Mazouz, Radia, Naima Filali, Zhour Hattab, and Kamel Guerfi. "Valorization of granulated slag of Arcelor-Mittal (Algeria) in cationic dye adsorption from aqueous solution: column studies." Journal of Water Reuse and Desalination 6, no. 1 (September 14, 2015): 204–13. http://dx.doi.org/10.2166/wrd.2015.049.
Повний текст джерелаАнотація:
A continuous adsorption study in a fixed-bed column was carried out using granulated slag (GS) as an adsorbent for the removal of methylene blue (MB) from aqueous solution. The effects of various parameters, such as initial dye concentration, flow rate, bed depth, and pH were investigated. Obtained results confirmed that the breakthrough time and exhaustion time were dependent on these factors. The adsorption capacity of GS was calculated at the 50% breakthrough point for different conditions. The highest breakthrough capacity (q,exp = 0.296 mg.g–1) was obtained with a 15 cm bed height and a 2 mL.min–1 rate by using a 10 mg.L–1 initial MB concentration at pH 7.5. Bohart–Adams, Bed Depth Service Time (BDST), and Thomas models were applied to experimental data to determine the characteristic parameters of the column. The Thomas model was found suitable for the description of the whole breakthrough curve, while the Bohart–Adams model was only used to predict the initial part of the dynamic process. The data were in good agreement with the BDST model. Thus, the granulated slag can be used as an adsorbent in the treatment of wastewater. Desorption was carried out with a deionized water as the desorbing agent, and reuse study was investigated.
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Khélifi, N., and M. Frank. "A major change in North Atlantic deep water circulation 1.6 million years ago." Climate of the Past 10, no. 4 (July 29, 2014): 1441–51. http://dx.doi.org/10.5194/cp-10-1441-2014.
Повний текст джерелаАнотація:
Abstract. The global ocean–climate system has been highly sensitive to the formation and advection of deep overflow water from the Nordic Seas as integral part of the Atlantic Meridional Overturning Circulation (AMOC) but its evolution over the Pliocene–Pleistocene global cooling is not fully understood. In particular, changes in the sources and mixing of prevailing deep waters that were involved in driving overturning throughout the Pliocene–Pleistocene climate transitions are not well constrained. Here we investigate the evolution of a substantial deep southward return overflow of the AMOC over the last 4 million years. We present new records of the bottom-water radiogenic neodymium isotope (&varepsilon;Nd) variability obtained from three sediment cores (DSDP site 610 and ODP sites 980/981 and 900) at water depths between 2170 and 5050 m in the northeast Atlantic. We find that prior to the onset of major Northern Hemisphere glaciation (NHG) ∼3 million years ago (Ma), &varepsilon;Nd values primarily oscillated between −9 and −11 at all sites, consistent with enhanced vertical mixing and weak stratification of the water masses during the warmer-than-today Pliocene period. From 2.7 Ma to ∼2.0 Ma, the &varepsilon;Nd signatures of the water masses gradually became more distinct, which documents a significant advection of Nordic Seas overflow deep water coincident with the intensification of NHG. Most markedly, however, at ∼1.6 Ma the interglacial &varepsilon;Nd signatures at sites 610 (2420 m water depth (w.d.)) and 980/981 (2170 m w.d.) synchronously and permanently shifted by 2 to 3 &varepsilon;Nd units to less radiogenic values, respectively. Since then the difference between glacial and interglacial &varepsilon;Nd values has been similar to the Late Quaternary at each site. A decrease of ∼2&varepsilon;Nd units at 1.6 Ma was also recorded for the deepest water masses by site 900 (∼5050 m w.d.), which thereafter, however, evolved to more radiogenic values again until the present. This major &varepsilon;Nd change across the 1.6 Ma transition reflects a significant reorganization of the overturning circulation in the northeast Atlantic paving the way for the more stratified water column with distinct water masses prevailing thereafter.
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Pan, Tianshi, Shibo Wang, Lijun Zuo, and Qiang Liu. "Influence of Grain on Green Patterns and Their Underlying Surface Characteristics on Water Conservation: A Case Study in a Semiarid Area." Forests 14, no. 10 (October 9, 2023): 2020. http://dx.doi.org/10.3390/f14102020.
Повний текст джерелаАнотація:
Water-conservation enhancement is a crucial objective of regional ecological restoration projects in arid and semiarid areas, and it is significantly influenced by land use/cover change (LUCC). The Grain for Green Project (GFGP) is a common strategy for ecological restoration. However, insufficient attention has been paid to the impact of reforestation patterns and the underlying surface characteristics on the effectiveness of GFGP in enhancing water conservation. In this study, a Soil and Water Assessment Tool (SWAT) scenario-based simulation was conducted to assess changes in water-conservation depth (WCD) in the Zhangjiakou section of the Guanting Reservoir basin. Redundancy analysis (RDA) and a mixed linear model were employed to determine the effects of different reforestation patterns and their underlying slope gradient and soil-type characteristics on WCD variation. The results showed that there were differences in the effect characteristics of reforestation patterns and different vegetation types on WCD changes; the effectiveness of increased water conservation is associated with the adaptation of reforestation plants to underlying characteristics. Returning farmland to evergreen forests was the most effective approach, leading to a relative increase in WCD that was 2.6 times greater than the relative increase in total WCD. WCD decreased with the slope gradient, with WCD decreasing by 0.2 mm for every 1° increase in slope. Converting grassland to evergreen forests on slopes greater than 16.19° and converting deciduous forests to grassland on slopes less than 16.19° would further increase WCD, promoting the synergistic development of ecosystem services. This study provides insights into the development of more efficient reforestation strategies to enhance water conservation in a complex terrain area.
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Kao, S. J., K. K. Liu, S. C. Hsu, Y. P. Chang, and M. H. Dai. "North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific." Biogeosciences 5, no. 6 (December 6, 2008): 1641–50. http://dx.doi.org/10.5194/bg-5-1641-2008.
Повний текст джерелаАнотація:
Abstract. Sedimentary δ15 N records in two IMAGES cores (MD012404 and MD012403) retrieved from the Okinawa Trough (OT) in the western North Pacific reveal deglacial increases with two peaks occurring during the Bølling/Allerød and the Preboreal/early Holocene periods. These peaks are synchronous with previously reported δ15 N peaks in the Eastern Tropical North Pacific, although the amplitudes (from 3.8 to 5.8‰) are much smaller in the OT. Similar δ15 N values for the last glacial maximum and the late-Holocene observed by us at a site far from the present-day zones of water-column denitrification (WCD) indicate that the mean 15 N/14 N of nitrate in the upper ocean did not differ much between the two climate states. The accumulation rate of organic carbon and total sulfur content are used as indices of the local WCD potential. The results suggest that enhancement of global WCD rather than local denitrification should be responsible for the deglacial maxima of sedimentary δ15 N in the Okinawa Trough. Our data could provide additional constraints to better understand changes in nitrogen budget during the glacial to interglacial transition.
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Somes, C. J., A. Oschlies, and A. Schmittner. "Isotopic constraints on the pre-industrial oceanic nitrogen budget." Biogeosciences 10, no. 9 (September 6, 2013): 5889–910. http://dx.doi.org/10.5194/bg-10-5889-2013.
Повний текст джерелаАнотація:
Abstract. The size of the bioavailable (i.e., "fixed") nitrogen inventory in the ocean influences global marine productivity and the biological carbon pump. Despite its importance, the pre-industrial rates for the major source and sink terms of the oceanic fixed nitrogen budget, N2 fixation and denitrification, respectively, are not well known. These processes leave distinguishable imprints on the ratio of stable nitrogen isotopes, δ15N, which can therefore help to infer their patterns and rates. Here we use δ15N observations from the water column and a new database of seafloor measurements to constrain rates of N2 fixation and denitrification predicted by a global three-dimensional Model of Ocean Biogeochemistry and Isotopes (MOBI). Sensitivity experiments were performed to quantify uncertainties associated with the isotope effect of denitrification in the water column and sediments. They show that the level of nitrate utilization in suboxic zones, that is the balance between nitrate consumption by denitrification and nitrate replenishment by circulation and mixing (dilution effect), significantly affects the isotope effect of water column denitrification and thus global mean δ15NO3–. Experiments with lower levels of nitrate utilization within the suboxic zone (i.e., higher residual water column nitrate concentrations, ranging from 20 to 32 μM) require higher ratios of benthic to water column denitrification, BD : WCD = 0.75–1.4, to satisfy the global mean NO3– and δ15NO3– constraints in the modern ocean. This suggests that nitrate utilization in suboxic zones plays an important role in global nitrogen isotope cycling. Increasing the net fractionation factor &varepsilon;BD for benthic denitrification (&varepsilon;BD = 0–4‰) requires even higher ratios, BD : WCD = 1.4–3.5. The model experiments that best reproduce observed seafloor δ15N support the middle to high-end estimates for the net fractionation factor of benthic denitrification (&varepsilon;BD = 2–4‰). Assuming a balanced fixed nitrogen budget, we estimate that pre-industrial rates of N2 fixation, water column denitrification, and benthic denitrification were between 195–350 (225), 65–80 (76), and 130–270 (149) Tg N yr−1, respectively, with our best model estimate (&varepsilon;BD = 2‰) in parentheses. Although uncertainties still exist, these results suggest that marine N2 fixation is occurring at much greater rates than previously estimated and the residence time for oceanic fixed nitrogen is between ~ 1500 and 3000 yr.
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Wang, Jiarui, Junju Zhou, Dongfeng Ma, Xi Zhao, Wei Wei, Chunfang Liu, Dongxia Zhang, and Chunli Wang. "Impact of Ecological Restoration Project on Water Conservation Function of Qilian Mountains Based on InVEST Model—A Case Study of the Upper Reaches of Shiyang River Basin." Land 12, no. 10 (September 28, 2023): 1850. http://dx.doi.org/10.3390/land12101850.
Повний текст джерелаАнотація:
Scientifically evaluating the influence of ecological restoration projects on the water conservation function (WCF) of regional ecosystems is the foundation for formulating regional ecological restoration policies and optimizing and adjusting ecological restoration projects. In this paper, we considered fully the runoff generation and confluence process in the Qilian Mountains with the actual situation of the basin and re-rated the parameter Z to improve the simulation accuracy of InVEST model. On this basis, the impact of ecological restoration project on the WCF in the upper reaches of Shiyang River Basin (SRB) in the eastern part of Qilian Mountains was quantified. The results showed that, on the whole, the water conservation depth (WCD) of forest land was the largest (138.5 mm) and that of cultivated land was the smallest (24.78 mm), while the water conservation coefficient of forest land was also the largest (93.36%) and that of unused land was the smallest (16.67%). From 1986 to 2018, the WCD showed an increasing trend in the upper reaches of SRB, among them, the WCD in the western tributaries increased faster than that in the eastern tributaries from 1986 to 2000. The significantly increased areas were mainly distributed in the middle reaches of the western tributaries and the river source areas of the eastern tributaries, while the significantly decreased areas were mainly distributed in the river source areas of the western tributaries and the cultivated land expansion area in the middle reaches of the eastern tributaries. From 2000 to 2018, the WCD of the eastern tributaries increased more than that of the western tributaries. The significantly increased areas were mainly distributed in the four eastern tributaries, and the significantly decreased areas were scattered in the middle and lower reaches of each tributary. From 1986 to 2000, the overall influence of land use change on the increase in WCD was negative, while the influence of climate and land use change on the increase in water conservation were both positive from 2000 to 2018. The influence of land use change on WCD was different in different tributaries. Among them, that of the western tributaries (except the Dongda River) was positive in two different periods, while that of the eastern tributaries (except the Xiying River) was changed from negative to positive. The implementation of ecological restoration project was one of the main reasons for the improvement of WCF in Qilian Mountains from 2000 to 2018, with a contribution of 9.04%. In the future, the protection and restoration of decreased areas of WCF should be strengthened, and the Z value determined in this paper is expected to be applied in the arid inland river basins of northwest China.
Дисертації з теми "Water Column Depth (WCD)"
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Ghannami, Mohamed Ali. "Statistical Inference of Water Column Depth through Radiometric and Geometric Analysis of Spectral Imagery." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2024. http://www.theses.fr/2024ENTA0008.
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La cartographie précise des eaux peu profondes, particulièrement en zones côtières, reste un défi majeur, notamment en ce qui concerne les incertitudes dans la mesure de la profondeur de la colonne d’eau (WCD). Cette précision est essentielle tant pour la navigation que pour la recherche, qui s’est jusqu’ici principalement concentrée sur l’estimation de la WCD sans considérer pleinement les incertitudes associées. Les méthodes traditionnelles, qu’elles soient radiométriques ou géométriques, présentent chacune leurs limitations spécifiques. Notre travail propose un cadre d’inférence basé sur la vraisemblance pour estimer rigoureusement ces incertitudes. L’approche se développe selon deux axes : une analyse radiométrique fondée sur la modélisation du transfert radiatif avec des techniques semi-analytiques, et une approche géométrique basée sur la triangulation stéréophotogrammétrique. Cette double méthodologie permet d’évaluer les biais et les erreurs inhérents à chaque approche. Le développement de ces cadres d’inférence dans les domaines radiométrique et géométrique est validé par des simulations réalistes, permettant une compréhension approfondie des incertitudes dans l’estimation de la WCD. Nos résultats démontrent l’efficacité de cette approche pour quantifier les incertitudes dans les deux types d’estimations. Cette recherche apporte une contribution significative à la télédétection passive et aux sciences marines en proposant des méthodes fiables pour évaluer les incertitudes dans la cartographie des eaux peu profondesThe complexities of mapping shallow water bodies, particularly coastal areas, have long been studied, yet a focused understanding of Water Column Depth (WCD) uncertainties remains notably lacking. While accurate measurement of these uncertainties is crucial for reliable bathymetric charts and safe navigation, current research has primarily focused on WCD estimation without considering associated uncertainties. Traditional approaches, whether radiometric or geometric analyses of spectral imagery, face distinct limitations in optically complex waters and featureless seabeds, respectively. Our work introduces a likelihood-based inference framework designed for robust estimation of WCD uncertainties through two main objectives. First, we develop a radiometric inferential approach based on Radiative Transfer (RT) modeling with Semi-Analytical (SA) techniques, enabling detailed analysis of uncertainties and inherent biases. Second, we establish a geometric inferential approach using stereo-photogrammetric triangulation to evaluate WCD uncertainties from a geometric perspective. These frameworks are validated through realistic simulations, focusing on understanding and quantifying WCD uncertainties. Our findings confirm the effectiveness of the likelihood-based inference framework in quantifying uncertainties for both radiometric and geometric WCD estimations. This research makes a significant contribution to passive remote sensing and marine science by providing reliable, comprehensive methods for assessing uncertainties in shallow water mapping
Частини книг з теми "Water Column Depth (WCD)"
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Vega-Moreno, Daura, Bárbara Abaroa-Pérez, and J. Joaquín Hernández-Brito. "Analysis of Marine Microplastics in the Water Column Sampled up to 300 M Depth." In Springer Water, 139–44. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45909-3_22.
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Cheng, Feng, Tao Liu, Zhiyuan Ma, Jiabin Chen, Shuo Li, Ruilong Liang, Yaoguang Zhang, and Xin Zhao. "Variation of strength of cement-soil mixing column with depth in dredger fill site." In Water Conservancy and Civil Construction Volume 1, 191–98. London: CRC Press, 2023. http://dx.doi.org/10.1201/9781003450818-29.
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Fjeldså, Jon. "Feeding ecology." In The Grebes Podicipedidae, 58–75. Oxford University PressOxford, 2004. http://dx.doi.org/10.1093/oso/9780198500643.003.0007.
Повний текст джерелаАнотація:
Abstract Grebes obtain most of their food by diving. Since their feeding is usually hidden to our eyes, finding out how they feed and what they eat presents a problem. Pertinent questions relate to hunting methods, depths, where they find their food, etc. We need to ask if a bird is a searcher or a pursuit hunter, a generalist or specialist? In addition to knowing the depth of the water where it feeds, we may want to know if it hunts near the surface, throughout the water column, around submergent vegetation, or at the bottom.
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Cohen, Andrew S. "The Chemical Environment of Lakes." In Paleolimnology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195133530.003.0008.
Повний текст джерелаАнотація:
Understanding lake chemistry is critical for correctly interpreting the geochemical archives of lake deposits. Elemental and isotopic distributions in lakes are closely linked to external climatic and watershed processes. Solute concentrations regulate the distribution of organisms, and the precipitation or dissolution of mineral phases. Both fossils and minerals leave sedimentary archives, and when we can interpret aspects of ancient water chemistry from these records we may be able to reconstruct paleoclimate or prior human activity around the lake. Interpretation of isotopic records likewise requires an initial understanding of their behavior in lakes and the links between this behavior and external factors such as rainfall or nutrient discharge. Oxygen (O2) is the second most abundant component of the atmosphere (∼ 21%) after nitrogen (∼ 78%): Paleolimnological indicators of oxygenation at the sediment–water interface may provide clues as to the nature and frequency of water-column mixing, water depth, the lake’s trophic condition, and possibly climate. Thus, it is important to understand how oxygen is generated and consumed in lakes to properly interpret the oxygenation archives and filters. Oxygen is dissolved in lakes directly from air, and as a byproduct of photosynthesis by autotrophic organisms (multicellular plants, algae, and photosynthetic bacteria), greatly simplified as: . . . 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2 (4:1) . . . Photosynthesis is performed by both organisms on the lake floor (phytobenthos), and by floating algae and bacteria (phytoplankton). Molecular oxygen is lost from the water column through respiration, secondary oxidation of organic or inorganic compounds in the water column or sediments, or directly to the atmosphere following supersaturation. Oxygen concentrations in the water column are a function of productivity, respiration, temperature, and mixing, all of which vary both diurnally and seasonally within a lake, and because of climatic or morphometric differences between lakes. To understand this variation, it is useful to return to our examples at Junius Ponds #5 and #7. In dimictic Junius Pond #7, the water column just below the ice is well oxygenated during the winter, but is anoxic at the lake floor.
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"Island in the Stream: Oceanography and Fisheries of the Charleston Bump." In Island in the Stream: Oceanography and Fisheries of the Charleston Bump, edited by Douglas C. Weaver and George R. Sedberry. American Fisheries Society, 2001. http://dx.doi.org/10.47886/9781888569230.ch8.
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<em>Abstract .</em>— Trophic relationships of dominant fishes associated with hard-bottom features of the upper continental slope of the southeastern United States are linked to pelagic prey occurring throughout the water column. Deflection of the Gulf Stream by the Charleston Bump is often associated with upwelling and increased water column productivity in this region of the southeastern Atlantic coast of the United States, leading to increased food availability along the shelf/slope margin. Planktivorous reef fishes take advantage of Zooplankton that is swept onto the outer shelf and upper slope, and are abundant in upper slope rocky habitats of the Charleston Lumps (~ 200 m depth). While upper slope reefs are numerically dominated by yellowfin bass <em> Anthias nicholsi, </em>a demersal planktivore, large predators of the upper slope, including snowy grouper <em> Epinephelus niveatus </em>and blueline tilefish <em> Caulolatilus microps, </em>primarily feed on benthic invertebrates. Blake Plateau reefs in the vicinity of the Charleston Bump (400-600 m depth) are dominated by vertically migrating predators such as alfonsinos <em> Beryx </em>spp., mesopelagic fishes and squids, and the large demersal wreckfish <em> Polyprion americanus. </em>Stomach contents of wreckfish reveal that vertically migrating organisms support dense aggregations of this large predator in areas of elevated topography at depths that are usually food poor.
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Mallin, Michael A. "The Physical Nature of River Ecosystems." In River Ecology, 3–24. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780199549511.003.0002.
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Abstract This chapter describes the longitudinal nature of river ecosystems, from headwaters to the estuary, explaining the fates of rainfall and its effects, infiltration to groundwater, rain-driven erosion both outside and within streams, the various within-stream physical features and how such features impact biota. The size of various particles is discussed, how the water currents move particles, how such particles shape habitat and carry pollutants, and how the water interacts with the riparian zone. Water temperature, a product of season and latitude, causes stratification of deeper rivers and estuaries, impacting distribution of suspended solids, nutrients, and plankton. Light within the water column is a major driver of the micro-and-macroscopic plant community and is strongly impacted by turbidity and water color. Simple equations are described using examples to determine the light attenuation coefficient, and how it is used to compute the amount of available light at a given depth is computed, as well as how current mixing impacts average light.
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Morgan, Steven G. "Dispersal." In Developmental Biology and Larval Ecology, 383–407. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190648954.003.0014.
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Dispersal of benthic crustaceans primarily occurs by larvae, which can be transported far from parents. However, larval dispersal is reduced by depth regulation in a sheared water column, where surface and bottom currents flow at different rates or directions, and navigation by postlarvae recruiting to adult habitats. Larvae undertake migrations between adult and larval habitats that range from retention near adult habitats to cross-shelf migrations. The extent of these migrations is regulated by depth preferences and vertical migrations that are timed exogenously or endogenously by diel and tidal cycles over planktonic development. Depth regulation is cued primarily by gravity, hydrostatic pressure, and light, and secondarily by temperature, salinity, and turbulence. Settlement stages navigate to suitable settlement sites using hierarchies of acoustic, chemical, visual, and celestial cues that are effective at different distances. The extent of larval migrations between adult and larval habitats as well as diel vertical migrations may be set by the vulnerability of larvae to abundant planktivorous fish in estuaries and nearshore waters. The timing of larval release and vertical swimming by larvae changes across tidal regimes to conserve migrations between adult and larval habitats across species ranges while minimizing predation.
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Ivaldi, Roberta, Geraldine Palacios Torres, Maurizio Demarte, Roberto Nardini, and Luigi Sinapi. "Integrated Mapping of the Seafloor Applied to Different Environments with Innovative Technologies: The Case Study of Molloy Hole (Arctic Ocean)." In NATO Science for Peace and Security Series - D: Information and Communication Security. IOS Press, 2024. http://dx.doi.org/10.3233/nicsp240029.
Повний текст джерелаАнотація:
Based on marine geophysical data collected during the IT-Navy HIGH NORTH20 and HIGH NORTH21 campaigns, a 3D integrated mapping of a region between 78.5-81°N and 1-12°E, where the Molloy Hole is located (Fram Strait – Arctic Ocean), has been developed. The Molloy Hole is the deepest undersea feature of the Arctic Ocean and plays a structural key role in the ocean geodynamics in terms of new ocean seafloor and gravitational mass movement, sink or barrier to the dynamics of the water masses with confined sedimentary processes in the presence of melting ice, polar and Atlantic water. The ocean surface (water and ice), the water column and the seabed data, thanks to an integrated-multidisciplinary approach and harmonization techniques named ‘imagery box’, has been processed using MATLAB R2021b to obtain a high-resolution 3D model. In particular, the research activities collected water column, bathymetry and acoustic backscatter from multibeam sonar surveys, CTD (Conductivity Temperature Depth) data, and sedimentary samples from box corers. The need for visualization to aid in the comprehensive analysis of all elements of this imaginary box is the main reason behind this research. Consequently, it seeks to integrate in situ and remote sensing measurements to provide an integrated mapping of the study area as a one single product. To achieve this goal, it is essential to optimize the process by standardizing the file formats so that all data can converge into a complete 3D depiction of the elements that compose the ocean: sea surface, water column and seafloor. The unification of distinct geospatial data should be of great help to scientists when analyzing their own ‘imaginary boxes’. This mapping is an integrated data product starting from the raw data to create a unique processing tool, and to produce a complete and comprehensive depiction of the 3D marine environment. This 3D integrated mapping highlights the undersea features as the drivers of the dynamics of the Molloy Hole from the sea surface to the ocean bottom.
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Mladenov, Philip V. "6. Deep-ocean biology." In Marine Biology: A Very Short Introduction, 115–34. Oxford University Press, 2020. http://dx.doi.org/10.1093/actrade/9780198841715.003.0007.
Повний текст джерелаАнотація:
The deep ocean is currently defined as the water column and ocean bottom greater than 500 metres, which is the depth at which seasonal variation in temperature and salinity and the influence of sunlight is minimal. This habitat encompasses roughly 90 per cent of the ocean’s volume yet this vast region is the least investigated and understood environment on the planet. ‘Deep-ocean biology’ explains that there are many issues for the existence of life in the deep ocean: lack of light, extreme pressure, scarcity of food, and temperature. However, deep-ocean animals have adapted to their surroundings. The diversity of deep-ocean benthic animals is described along with the unique ecosystems found around hydrothermal vents and seamounts.
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"Early Life History of Fishes in the San Francisco Estuary and Watershed." In Early Life History of Fishes in the San Francisco Estuary and Watershed, edited by Andrew K. Rockriver. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569599.ch7.
Повний текст джерелаАнотація:
<em>Abstract.</em>—The goal of this study was to determine if the vertical distribution of larval delta smelt <em>Hypomesus transpacificus </em>and striped bass <em>Morone saxatilis </em>was affected by tidal stage and diel period. Delta smelt and striped bass have similar early life histories in that their larvae drift downstream from freshwater spawning habitats to brackish water rearing habitats. Little is known on whether the larvae undergo a vertical migration as they move downstream. Conical plankton nets were used to collect larval fishes from the surface, middle, and bottom sections of the main channels of the Sacramento and San Joaquin rivers. Samples were collected over six paired day–night cruises. Approximately 45,000 fish were collected; 82% were striped bass and 2% were delta smelt. More delta smelt were caught at night than during the day, and more at middle depth than surface or bottom. Very few striped bass were found at surface during day; most were caught at middle depth. Both species were fairly dispersed throughout the water column at night. Although striped bass larvae appear to undergo a small surface to middepth migration, this study indicates that larval delta smelt and striped bass do not undergo a mass diel or tidal vertical migration as they drift down the Sacramento and San Joaquin rivers.
Тези доповідей конференцій з теми "Water Column Depth (WCD)"
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Roberts, R., C. O’Brien, R. Sheppard, Y. Moslehy, and M. Kitson. "Wandoo A – Reliability Methodology for Determination of Probability of Failure of a Braced Caisson Structure." In Offshore Technology Conference. OTC, 2024. http://dx.doi.org/10.4043/35427-ms.
Повний текст джерелаАнотація:
The Wandoo A (WNA) fixed platform was installed in 1993 with an intended service life of 15 years. It has subsequently undergone two 5-year life extension (recertification) studies – one in 2008 and another in 2013. The original design and both recertification studies followed API RP 2A WSD guidance (American Petroleum Institute, 2002). The platform (see Fig. 1) is a braced caisson structure in 52m water depth. The structure supports five conductors: 1 through the main column, 2 external that penetrate through the skirt piles, 1 supported by an external riser caisson and 1 external. The foundation consists of five piles: 1 through the main column, 2 skirt piles, and 2 outrigger piles. The system also features a tuned liquid damper (TLD) incorporated into the main column near El. (+)17m. This damper is intended to increase the structural damping and reduce system accelerations in response to environmental loading. The TLD is a set of three tanks filled to specific levels with water. The motion of the entrapped fluid provides the damping which has been tuned to the primary structural period.
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Morris-Thomas, M. T., R. Irvin, and K. P. Thiagarajan. "The Hydrodynamic Efficiency of an Oscillating Water Column." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67371.
Повний текст джерелаАнотація:
An oscillating water column device enables the conversion of wave energy into electrical energy via wave interaction with a semi-submerged chamber coupled with a turbine for power take off. This present work concentrates on the wave interaction with the semi-submerged chamber, whereby a shore based oscillating water column (OWC) is studied experimentally to examine energy efficiencies for power take-off. The wave environment considered consists of plane progressive waves of steepnesses ranging from kA = 0.01 to 0.22 and water depth ratios varying from kh = 0.30 to 3.72, where k, A and h denote the wave number, wave amplitude and water depth respectively. The key feature of this experimental campaign is a study on the influence of geometrical parameters of the front wall on the OWC’s performance. More specifically, these parameters include: front wall draught; thickness; and aperture shape. We make use of a two-dimensional inviscid theory for an OWC for comparative purposes and to explain trends noted in the experimental measurements. The work undertaken here has revealed a broad banded efficiency centred about the natural frequency of the OWC. The magnitude and shape of the efficiency curves are influenced by the geometry of the front wall. Typical resonant efficiencies of the OWC are in the order of 70%.
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Kaleyna, P., N. Kolev, P. Savov, Ts Evgenieva, V. Danchovski, and P. Muhtarov. "Measurements of total column ozone, precipitable water content and aerosol optical depth at Sofia." In 9TH INTERNATIONAL PHYSICS CONFERENCE OF THE BALKAN PHYSICAL UNION (BPU-9). AIP Publishing LLC, 2016. http://dx.doi.org/10.1063/1.4944272.
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Roveri, Francisco Edward, Lui´s Volnei Sudati Sagrilo, Edison Castro Prates de Lima, and Federico Barranco Cicilia. "Comparing Measured and Calculated Forces of a Manifold Deployment in 940 Meters Water Depth." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37114.
Повний текст джерелаАнотація:
In August 2001 the MRL-5 production manifold was installed by PETROBRAS in 940 meters water depth at the Marlim field offshore Brazil. The semi-submersible Amethyst, using an 18-5/8” marine riser, deployed it into the location. During the manifold deploying, several in-site measurements of the hook forces (force at the drill line dead end) and the semi-submersible accelerations were done. Both time series for the vertical accelerations and forces were obtained for two positions of the manifold along the water column. The main objective of this paper is to compare the results from the column riser system numerical analysis with the riser axial forces measurements obtained by the monitoring system.
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Rahman, Anisur, Vallipuram Muthukkumarasamy, and Elankayer Sithirasenan. "The Analysis of Temperature, Depth, Salinity Effect on Acoustic Speed for a Vertical Water Column." In 2013 IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS). IEEE, 2013. http://dx.doi.org/10.1109/dcoss.2013.63.
Повний текст джерела
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Mavrakos, Spyros A., and Dimitrios N. Konispoliatis. "Hydrodynamic Analysis of a Vertical Axisymmetric Oscillating Water Column Device Floating in Finite Depth Waters." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83998.
Повний текст джерелаАнотація:
A floating oscillating water column device (OWC) consists of a vertical cylinder, with a finite wall thickness, partly submerged as an open-bottom chamber in which air is trapped above the inner water free surface. The chamber is connected with the outer atmosphere by a duct housing an air turbine. Forced by incident waves from any direction, the water surface inside pushes the dry air above through a Wells turbine system to generate power. In the present contribution the volume flows, the wave forces, the added mass and damping coefficients and the mean second-order loads for various configurations of OWC devices are being presented. Finally, it is tested how differentiations in the device’s geometry (wall thickness, draught, shape of the chamber, turbine characterises) affect the inner pressure and as a result the absorbed power by the device.
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Davies, Kent, Steve Leverette, and Neil Williams. "Design of Mono-Column TLPs for Ultra-Deepwater Applications." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37351.
Повний текст джерелаАнотація:
Previous industry discussion has notionally limited the TLP concept to water depths less than 1,500m (∼4500 ft). This paper presents the results of analysis performed to clarify the limits for mono-column TLP’s and explores means to extend the applicable range of TLP’s to ultra-deep water. Detailed coupled motion and fatigue analyses were carried out for a realistic production case over a wide range of water depths (1,000 to 3,000m) for moderate (Gulf of Mexico) and mild (West Africa) conditions. The existing Matterhorn SeaStar TLP design was used as the test platform for the study. The topsides payload and surface-well count were held constant while adapting the hull and tendons for increasing water depth. Consideration was given to both conventional and nonconventional, but near-term, tendon solutions. Following the engineering analysis, design alternatives are compared on an economic basis.
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Garcia Govea, C., Juan Jose´ Corte´s Romero, and O. Valle Molina. "Deep Water Current Observations in Lankahuasa Area in the Mexican Gulf of Mexico." In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92644.
Повний текст джерелаАнотація:
In preparation for the near future deep-water exploitation in the Mexican oil industry, the Mexican Petroleum Institute and Pemex carried out the first oceanographic sub-surface mooring installation in deep waters, in Lankahuasa area in 1500 m water depth. The aim of this project is to supply the necessary water column information for planning, installation, development and production activities for the Mexican offshore industry. Parameters measured include, current velocities, current direction, internal waves as well as traditional water quality measurements. Profiles of conductivity, temperature and Depth (CTD) from 100 m up to 2,500 m water depths were obtained from cruises where samples were taken over a wide area during January and February 2005. Salinity and density are calculated from CTD data. Oceanographical parameters were measured by 3 ADCP (Acoustic Doppler Current Profile) and by 2 current meters in the entire water column. The oceanographic situation during the deployment was characterized by the presence of an anticyclonic (clockwise rotating) eddy and a cyclonic one in the area, located to the north of 21° N. Both eddies were slowly propagating in a general southward direction.
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Yang, Xiaolong, Hui Shen, Hui Li, Xiaoliang Qi, Guosen Lv, and Zhiyong Su. "A Parametric Sensitivity Study on TLP Hydrodynamic Performance in South China Sea." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41362.
Повний текст джерелаАнотація:
As a typical floating platform, TLP (Tension leg platform) is widely used around the world of the water depth from 140m to 1400m due to its significant advantages over other deep-water production systems. This paper describes a conventional TLP type application for relatively shallow water depth of 410m, it was studied for a potential development plan in China south sea. Considering the safety and efficiency in the construction, installation and operation, a comprehensive sensitivity study of the simulation results against various analysis/environment parameters (including column form, wind coefficients, tendon pretension, etc.) was carried out and the role of each critical parameter was analyzed deeply. The numerical simulations were conducted for 1000-yr Hurricane condition with collinear wind, wave, and current directions. The results based on this study show that the change of the column pattern (from round column to square column) does not have much difference on the TLP hydrodynamic performance without other conditions changed; the variation of pre-tension has limited influence to the TLP hydrodynamic performance as this relatively shallow water.
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Amano, R. S., Ammar Alkhalidi, Patrick Bryar, and Wayel Alwayel. "Water Aeration in Wastewater Treatment." In ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71524.
Повний текст джерелаАнотація:
The primary objective of this paper is to examine ways to increase the efficiency of water aeration process. This objective was completed through the use of a propeller and fan blade designs. Both Standard oxygen transfer efficiency (SOTE) and power reclamation were analyzed. Results of SOTE analysis indicated a decrease in efficiency, when compared to the standard model air diffuser. While the propeller design was able to successfully breakup the forming bubble column, the system reduced the circulatory currents that create mixing within the experimental tank. Results indicate a small SOTE drop, throughout the system. Power reclamation was able to yield, at a peak depth of 25cm (10 in) below the top water surface, 0.8W, with input energy of approximately 45 W resulting in reclamation of 1.8% of the power put into the system. This data was retrieved at a volumetric flow rate of 9.4 × 10−4 m3/s (2 CFM) with a pressure of 55kPa (8psi).
Звіти організацій з теми "Water Column Depth (WCD)"
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Starkey, Eric, Daniel McCay, Chrisopher Cooper, and Mark Hynds. Assessment of estuarine water and sediment quality at Cape Hatteras National Seashore and Cape Lookout National Seashore: 2021 data summary. National Park Service, October 2022. http://dx.doi.org/10.36967/2294854.
Повний текст джерелаАнотація:
In July 2021 the Southeast Coast Network conducted an assessment of water quality in the vicinity of Cape Hatteras and Cape Lookout National Seashores as part of the National Park Service Vital Signs Monitoring Program. Monitoring was conducted following methods developed by the Environmental Protection Agency (EPA) as part of the National Coastal Assessment Program (EPA 2010). Laboratory analysis measured chlorophyll a and total and dissolved concentrations of nitrogen and phosphorous. Field measurements included water temperature, pH, dissolved oxygen, and salinity. Water clarity, which requires a Secchi depth measurement, was obtained when possible. All measured parameters were rated as good, fair, or poor based on thresholds set by the EPA (2012). All measured parameters were rated as good, fair, or poor based on thresholds set by the EPA (2012). Water clarity was not calculated at all sites due to the shallow depth of the water in the sound. Of the sites where water clarity could be assessed (5 sites), four measured good and one fair. Sites that were too shallow to measure water clarity had water column conditions that did not preclude light from penetrating to the bottom of the water body so no ecological effects would be expected.Turbidity measurements ranged from 1.0 to 8.0 FNU (Formazin Nephelometric Units) and are good (i.e. < 25 NTU [Nephelometric Turbidity Units]) according to North Carolina Standards (NC Administrative Code 2019). Note that turbidity units of FNU and NTU are roughly equivalent. Chlorophyll a concentration was rated good at 29 sites (97%), and fair at one site (3%). Dissolved inorganic nitrogen (DIN) concentration was good at all 30 sites (100%). Dissolved inorganic phosphorus (DIP) concentration was good at all 30 sites (100%). Dissolved oxygen concentration (bottom) was rated good at all 30 sites (100%). A water-quality condition summary index was calculated for each site sampled at Cape Hatteras and Cape Lookout National Seashores based on the categorical assessments of chlorophyll a, DIN and DIP concentrations, dissolved oxygen, and water clarity. This summary index indicated good water-quality conditions at all thirty sites (100%). Based on the summary water-quality index rating, overall water-quality conditions at Cape Hatteras and Cape Lookout National Seashores during sampling in 2021 were good. For sediment, ecological condition was ranked as good at 30 sites (100%). As a result, no adverse impacts to benthic organisms due to sediment contamination are anticipated at any of the sampled sites. This ranking was assigned according to the 2010 Environmental Protection Agency, National Coastal Condition Assessment (NCCA) thresholds for sediment chemistry.
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Atkinson, E. A. Regional mapping and qualitative petroleum resource assessment of the Magdalen Basin, Gulf of St. Lawrence, Quebec, Prince Edward Island, New Brunswick, Nova Scotia, and Newfoundland and Labrador. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331452.
Повний текст джерелаАнотація:
The Geological Survey of Canada conducted a broad regional study of the Magdalen Basin in the Gulf of St. Lawrence, as part of the Marine Conservation Targets initiative. MCT is a national initiative to protect more of Canada's offshore areas, and resource assessment and related regional mapping are part of the review process. This study assembled a large seismic and geologic database that allowed new regional mapping of several key horizons in this basin. Digital seismic data was donated by industry, and reprocessing undertaken both in-house and with contractors. Wells were correlated and tops from literature were used to indentify regional reflection packages. Regionally consistent two-way time interpretations add to confidence. Depth conversion used regional time-depth functions from literature, which were developed from refraction data, with a residual correction for the water column. Nine regional depth maps and eight isopach maps were produced, including Pre-Horton Basement, Horton Group Isopach, Base Windsor Group, Top Salt, Top Bradelle Formation, Bradelle / Cumberland Isopach, and Top Cable Head Formation. These maps illustrate that the Pre-Horton basement is about 15 km deep in the centre of the basin. Two main trends are visible in the Horton Grabens, which may relate to basin formation, and no significant reactivation of deeper Appalachian structure is observed. In the basin centre, the more robust Base Windsor Unconformity horizon reaches about 12 km deep, and a key reservoir and source sequence in the Bradelle Formation reaches 7 km. These maps are useful for considering regional stratigraphy. The new mapping also constrained basin models and became the input for our Qualitative Petroleum Potential map. Basin modelling reveals scenarios where oil may be preserved. The petroleum potential of the region is highest north of Îles de la Madeleine and southeast of Îles de la Madeleine and northwest of Cape Breton.
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Wadman, Heidi M., John B. Gaskin, and Anthony R. Jackson. Performance of High-Resolution, Acoustic Mapping Systems in a Fluid-Mud Environment : Testing the Effectiveness and Viability of High-Resolution, Hydrographic Survey Systems in a Fluid-Mud Environment. U.S. Army Engineer Research and Development Center, October 2024. http://dx.doi.org/10.21079/11681/49436.
Повний текст джерелаАнотація:
This study explores the use of high-resolution acoustic mapping systems to penetrate fluid-mud layers by quantitatively relating depth with operating frequency. Prior to this study, multibeam surveys have proven be an effective method to elucidate the seafloor and collect bathymetric data on various bodies of water including rivers, lakes, bays, and the oceans. These techniques are regularly used on US Army Corps of Engineers dredged and federally maintained navigation channels. The objective of the study was to test the effectiveness of commercial off-the-shelf, low-frequency, high-resolution acoustic survey systems to penetrate fluid mud and if so, determine the density at penetration. The testing method combined multibeam echosounder, sub-bottom profiler, and single-beam echo sounder. In addition, in situ testing was conducted to determine the density of fluid-mud layers using a RheoTune profiler and laboratory testing. Results indicate that the use of currently available, bathymetric mapping systems operating at 90 kHz and higher are incapable of penetrating fluid mud in riverine and coastal shallow water conditions. This study demonstrates that while multibeam technology is effective at penetrating the water column, current frequencies available on the market are unable to penetrate fluid-mud layers in a riverine and shallow-water environment.
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Barker, Amanda, Taylor Sullivan, W. Baxter, Robyn Barbato, Shawn Gallaher, Grace Patton, Joseph Smith, and Thomas Douglas. Iron oxidation–reduction processes in warming permafrost soils and surface waters expose a seasonally rusting Arctic watershed. Engineer Research and Development Center (U.S.), June 2024. http://dx.doi.org/10.21079/11681/48714.
Повний текст джерелаАнотація:
Landscape-scale changes from climate change in the Arctic affect the soil thermal regime and impact the depth to permafrost in vulnerable tundra watersheds. When top-down thaw of permafrost occurs, oxygen and porewaters infiltrate deeper in the soil column exposing fresh, previously frozen material and altering redox conditions. A gap remains in understanding how redox stratifications in thawing permafrost impact the geochemistry of watersheds in response to climate change and how investigations into redox may be scaled by coupling extensive geophysical mapping techniques. In this study, we collected soils and soil porewaters from three soil pits and surface water samples from an Arctic watershed on the North Slope of Alaska and analyzed for trace metals iron (Fe) and manganese (Mn) and Fe oxidation state using bulk and microscale techniques. We also used geophysical mapping and soil thermistors to measure active layer depths across the watershed to relate accelerating permafrost thaw to watershed geochemistry. Overall, evidence showed that Fe and Mn could be useful as geochemical indicators of permafrost thaw and release of Fe(II) from thawing permafrost and further oxidation to Fe(III) could translate to a higher degree of seasonal rusting coinciding with the warming and thawing of near surface-permafrost.
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Sommer, Stefan, Sascha Flögel, Michael Walter, and Frank Wenzhöfer. Autonomous Robotic Network to Resolve Coastal Oxygen Dynamics : Cruise No. AL547, 20.10. – 31.10.2020, Kiel – Kiel, ARCODYN. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2022. http://dx.doi.org/10.3289/cr_al547.
Повний текст джерелаАнотація:
The ALKOR cruise AL547 represents a concluding milestone of the Helmholtz innovation project ARCHES (Autonomous Robotic Networks to Help Modern Societies). The aim was to implement a heterogeneous robotic sensing network to simultaneously monitor changes in the water column and at the seafloor. The network has been developed by a consortium of partners from AWI, DLR, GEOMAR and the University of Kiel. The participating sensing platforms allow for real-time data transfer and the entire network shall be able to autonomously respond to environmental changes in the ocean. The network comprised seven different mobile and stationary platforms. Tests were conducted at the Mittelgrund working area in the entrance of the Eckernförde Bay (western Baltic Sea). During 47 stations the various sensing platforms were deployed and recovered for maintenance. A total of 87853 messages were sent using hydro-acoustics, of which 71734 messages contained O 2 data, 15177 were status messages, 926 messages were commands to trigger a change of the measurement behavior of a platform and 16 messages represented broadcasts about the environmental status. We synoptically recorded short-term O 2 time series on the different platforms, which were placed along a depth gradient in the working area. As the Eckernförde Bay is known for sporadic fish kills by anoxia we hope to contribute to a better understanding of the O 2 dynamics in coastal areas. - (ALKOR-Berichte ; AL547)
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Douglas, K., J. V. Barrie, T. Dill, T. Fralic, and N. Koshure. 2021004PGC cruise report: mapping Salish Sea marine geohazards, British Columbia. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329621.
Повний текст джерелаАнотація:
The Geological Survey of Canada (GSC) undertook marine fieldwork onboard the Canadian Coast Guard Ship (CCGS) Vector to locate and map potential geohazards and geological features in the Salish Sea in the interest of public safety from August 11-18, 2021. This work was conducted under the Natural Resources Canada Marine Geoscience for Marine Spatial Planning (MGMSP) and the Public Safety Geoscience Programs. The GSC had observed multiple potential faults in existing data near Central Haro Strait, Stuart Channel, South of Hornby Island and near Cape Lazo through existing CHIRP and multibeam bathymetry data but required further data to quantify their activity and potential seismic risk (Barrie et al, 2021). In addition to fault activity, the GSC had detected numerous large underwater landslide deposits in Howe Sound and Saanich Inlet. The GSC required further data to constrain volumes and timing of slide activity. In English Bay the origin and evolution of a field of pockmarks was poorly understood. In Burrard Inlet, the survey required a better understanding of frequency of landslides as well as depth of sediment in order to understand natural sediment depositional rates. The research expedition included deep-tow system (DTS) sub-bottom surveys and multibeam water column and bathymetric surveys in each of these areas to better understand these marine geohazards and processes. Hydrographic surveys were completed by the Canadian Hydrographic Service (CHS) at night in Pylades Channel and near Point Grey to maximize use of ship time. Weather was good, seas were calm, and good quality data were collected. The data collected will be made publicly available and have the potential to contribute to building codes and to help communities in their decision-making and understanding of risks.