Effect of thickness of planar nozzles on erosion depth of levee soils subjected to plunging water     

Chung Rak Song  Jinwon Kim  James Tyler Kidd  Alexander Cheng  David Admiraal 《国际泥沙研究》2018,33(3):243-249

In this study, the effect of the thickness of a planar jet on the erosion depth when the jet impinges on a surface composed of cohesive soil was analytically and numerically evaluated. The results showed that the erosion depth was practically independent of the nozzle thickness for erosion depths shallower than the potential core length (i.e. the region of the jet in which the central flow velocity is the same as the nozzle velocity). The relation between nozzle thickness and erosion depth was non-linear with continuously variable slope for erosion depths deeper than the potential core length. Finally, the relation was approximately linear when the erosion depth converged to the equilibrium erosion depth. The findings of this study indicate that direct and fast prediction of the erosion depth in the field is possible using the data from a small scale soil erosion test with similar flow velocities.  相似文献   

Surface melt-driven seasonal behaviour (englacial and subglacial) from a soft-bedded temperate glacier recorded by in situ wireless probes     

Jane K. Hart  Kirk Martinez  Philip J. Basford  Alexander I. Clayton  Graeme M. Bragg  Tyler Ward  David S. Young 《地球表面变化过程与地形》2019,44(9):1769-1782

We investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique Glacsweb wireless in situ probes (embedded in the ice and the till) combined with other techniques [including ground penetrating radar (GPR) and borehole analysis]. During the melt season (spring, summer and autumn), high surface melt leads to high water pressures in the englacial and subglacial environment. Winter is characterized by no surface melting on most days (‘base’) apart from a series of positive degree days. Once winter begins, a diurnal water pressure cycle is established in the ice and at the ice/sediment interface, with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag. This direct surface melt also drives water pressure changes in the till. Till deformation occurred throughout the year, with the winter rate approximately 60% that of the melt season. We were able to show the bed comprised patches of till with different strengths, and were able to estimate their size, relative percentage and temporal stability. We show that the melt season is characterized by a high pressure distributed system, and winter by a low pressure channelized system. We contrast this with studies from Greenland (overlying rigid bedrock), where the opposite was found. We argue our results are typical of soft bedded glaciers with low englacial water content, and suggest this type of glacier can rapidly respond to surface-driven melt. Based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets, which may become more channelized in winter, and more responsive to changes in meltwater inputs. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Assessing regional‐scale spatio‐temporal patterns of groundwater–surface water interactions using a coupled SWAT‐MODFLOW model          下载免费PDF全文

Ryan T. Bailey  Tyler C. Wible  Mazdak Arabi  Rosemary M. Records  Jeffrey Ditty 《水文研究》2016,30(23):4420-4433

Interaction between groundwater and surface water in watersheds has significant impacts on water management and water rights, nutrient loading from aquifers to streams, and in‐stream flow requirements for aquatic species. Of particular importance are the spatial patterns of these interactions. This study explores the spatio‐temporal patterns of groundwater discharge to a river system in a semi‐arid region, with methods applied to the Sprague River Watershed (4100 km²) within the Upper Klamath Basin in Oregon, USA. Patterns of groundwater–surface water interaction are explored throughout the watershed during the 1970–2003 time period using a coupled SWAT‐MODFLOW model tested against streamflow, groundwater level and field‐estimated reach‐specific groundwater discharge rates. Daily time steps and coupling are used, with groundwater discharge rates calculated for each model computational point along the stream. Model results also are averaged by month and by year to determine seasonal and decadal trends in groundwater discharge rates. Results show high spatial variability in groundwater discharge, with several locations showing no groundwater/surface water interaction. Average annual groundwater discharge is 20.5 m³/s, with maximum and minimum rates occurring in September–October and March–April, respectively. Annual average rates increase by approximately 0.02 m³/s per year over the 34‐year period, negligible compared with the average annual rate, although 70% of the stream network experiences an increase in groundwater discharge rate between 1970 and 2003. Results can assist with water management, identifying potential locations of heavy nutrient mass loading from the aquifer to streams and ecological assessment and planning focused on locations of high groundwater discharge. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Geoarchaeological Investigations in Mesoamerica Move into the 21st Century: A Review     

Nicholas P. Dunning  Carmen McCane  Tyler Swinney  Matthew Purtill  Jani Sparks  Ashley Mann  Jon‐Paul McCool  Chantal Ivenso 《Geoarchaeology》2015,30(3):167-199

Over the past thirty years, geoarchaeology has moved from the fringe to mainstream status within Mesoamerican archaeological investigations. This review focuses on works published since the year 2000. Five themes are identified as central to recent studies: (1) the correlation of environmental change and cultural history; (2) anthropogenic environmental impacts; (3) ancient land cover, land use, and diet; (4) archaeological prospection; and (5) provenance studies. These themes are often interwoven in the application of complex systems approaches that allow scientists to more accurately model the intricacies of ancient human–environment interactions.  相似文献   

A ‘string function’ for describing the propagation of large-scale potential energy anomalies in a rotating fluid     

R. H. Tyler  R. Käse 《地球物理与天体物理流体动力学》2013,107(1-2):31-64

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Notes on sheet 48 N.W. (Shropshire)     

W.H. Tyler 《Proceedings of the Geologists' Association. Geologists' Association》1925,36(4):377-378

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Seasonality and selectivity in the feeding ecology and reproductive biology of deep-sea bathyal holothurians     

Ian R. Hudson  Benjamin D. Wigham  David S. M. Billett  Paul A. Tyler 《Progress in Oceanography》2003,59(4):381-407

Chlorophyll and carotenoid pigments were determined from the gut sediments of five species of bathyal holothurian in the NE Atlantic, sampled shortly after the spring/summer phytoplankton bloom in 2001 and prior to the spring bloom in 2002. Three species, Laetmogone violacea, Paroriza pallens and Bathyplotes natans, sampled within a similar depth range (900–1100 m) in the summer of 2001 showed significant differences in their chlorophyll and carotenoid pigment concentrations. This suggests they may select for slightly different components from the available food resource. Four species sampled in early spring 2002, Laetmogone violacea, Paroriza pallens, Benthogone rosea and Benthothuria funebris, also had significant differences in their pigment concentrations. These species were sampled over a wider depth range (1000–3100 m) showing a bathymetric trend in pigment concentrations. There was a distinct seasonal change in the composition and concentration of the pigments, linked to a reduction in the availability of fresh organic material during autumn and winter periods.Ovarian tissue was also examined. The carotenoid pigments found in the ovary also occurred in the OM ingested by the holothurians. The dominant gonadal carotenoid pigments were β-carotene, echinenone and zeaxanthin. The potential for using these carotenoids to gain a competitive advantage through selectivity of chlorophyll and carotenoid pigment biomarkers are discussed in relation to competition for food resources by deposit-feeders. The results were also compared with selectivity in abyssal species.  相似文献   

Government-Funded Deep Geophysical Surveys to Encourage Mineral Exploration: Results from the Western Australian “Exploration Incentives Scheme”     

Michael Dentith  Klaus Gessner  Simon Johnson  Ruth Murdie  Perla Pina-Varas  Jessica Spratt  Ian Tyler  Huaiyu Yuan 《《地质学报》英文版》2018,92(Z1):16-17

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The synergistic effect of calcium on organic carbon sequestration to ferrihydrite   总被引：1，自引：0，他引：1  

Tyler D. Sowers  Jason W. Stuckey  Donald L. Sparks 《Geochemical transactions》2018,19(1):4

Sequestration of organic carbon (OC) in environmental systems is critical to mitigating climate change. Organo-mineral associations, especially those with iron (Fe) oxides, drive the chemistry of OC sequestration and stability in soils. Short-range-ordered Fe oxides, such as ferrihydrite, demonstrate a high affinity for OC in binary systems. Calcium commonly co-associates with OC and Fe oxides in soils, though the bonding mechanism (e.g., cation bridging) and implications of the co-association for OC sequestration remain unresolved. We explored the effect of calcium (Ca²⁺) on the sorption of dissolved OC to 2-line ferrihydrite. Sorption experiments were conducted between leaf litter-extractable OC and ferrihydrite at pH 4 to 9 with different initial C/Fe molar ratios and Ca²⁺ concentrations. The extent of OC sorption to ferrihydrite in the presence of Ca²⁺ increased across all tested pH values, especially at pH ≥ 7. Sorbed OC concentration at pH 9 increased from 8.72 ± 0.16 to 13.3 ± 0.20 mmol OC g^?1 ferrihydrite between treatments of no added Ca²⁺ and 30 mM Ca²⁺ addition. Batch experiments were paired with spectroscopic studies to probe the speciation of sorbed OC and elucidate the sorption mechanism. ATR-FTIR spectroscopy analysis revealed that carboxylic functional moieties were the primary sorbed OC species that were preferentially bound to ferrihydrite and suggested an increase in Fe-carboxylate ligand exchange in the presence of Ca at pH 9. Results from batch to spectroscopic experiments provide significant evidence for the enhancement of dissolved OC sequestration to 2-line ferrihydrite and suggest the formation of Fe–Ca-OC ternary complexes. Findings of this research will inform modeling of environmental C cycling and have the potential to influence strategies for managing land to minimize OM stabilization.  相似文献   

Distribution and spatial variation of hydrothermal faunal assemblages at Lucky Strike (Mid-Atlantic Ridge) revealed by high-resolution video image analysis     

Daphne Cuvelier  Joze Sarrazin  Ana Colao  Jon Copley  Daniel Desbruyres  Adrian G. Glover  Paul Tyler  Ricardo Serro Santos 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2026-2040

Whilst the fauna inhabiting hydrothermal vent structures in the Atlantic Ocean is reasonably well known, less is understood about the spatial distributions of the fauna in relation to abiotic and biotic factors. In this study, a major active hydrothermal edifice (Eiffel Tower, at 1690 m depth) on the Lucky Strike vent field (Mid-Atlantic Ridge (MAR)) was investigated. Video transects were carried out by ROV Victor 6000 and complete image coverage was acquired. Four distinct assemblages, ranging from dense larger-sized Bathymodiolus mussel beds to smaller-sized mussel clumps and alvinocaridid shrimps, and two types of substrata were defined based on high definition photographs and video imagery. To evaluate spatial variation, faunal distribution was mapped in three dimensions. A high degree of patchiness characterizes this 11 m high sulfide structure. The differences observed in assemblage and substratum distribution were related to habitat characteristics (fluid exits, depth and structure orientation). Gradients in community structure were observed, which coincided with an increasing distance from the fluid exits. A biological zonation model for the Eiffel Tower edifice was created in which faunal composition and distribution can be visually explained by the presence/absence of fluid exits.  相似文献