摘要 :
The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico to collect time-series data on sediment flux from 2008 to 2012. There are continuous measurements of total mass flux and organic carbon flux (orgC)...
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The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico to collect time-series data on sediment flux from 2008 to 2012. There are continuous measurements of total mass flux and organic carbon flux (orgC) at 714 day resolution from 2008 to 2012. The flux of calcium carbonate (CaCO3), particulate nitrogen (nitro), and biogenic silica (Opal) were also measured from January-December, 2008. The mass flux ranged from 0.01 g m-2 day-1 (grams per square meter per day ) to 2.50 g m-2 day-1, with a mean mass flux of 0.20 g m-2day-1 over the 5-year study period.
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摘要 :
The central goal of this project is a deeper understanding of the dynamic adjustment of mobile sandy sediments to fluid forcing in and near the surf zone at small (1cm to 10m) and intermediate (10m to 100m) horizontal scales. The ...
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The central goal of this project is a deeper understanding of the dynamic adjustment of mobile sandy sediments to fluid forcing in and near the surf zone at small (1cm to 10m) and intermediate (10m to 100m) horizontal scales. The effort is motivated by the dual need to develop more realistic models of fluid-sediment interactions in the nearshore zone, and for suitable in situ measurement techniques to make the observations necessary to adequately test the models. The primary objectives of this project are: (1) to study the role of bedforms of different characteristic spatial pattern and scale in the local sediment flux and momentum balances, and (2) to investigate bedform genesis, growth, migration, and decay in relation to the fluid forcing conditions and predicted sediment transport rates. Of particular interest are the relationships between sediment fluxes, bedform properties, and asymmetries in the fluid motions. A key initial objective was to obtain a comprehensive set of measurements of bed adjustment through time, as a function of cross-shore position, and over a period of several months. This data set was obtained in SandyDuck, and is providing a basis for determining cross-shore differences in response synoptically, and for differences in the response trajectories through time and between forcing events, over a suitably wide range of conditions.
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摘要 :
Our research program focuses on identifying and quantifying sediment erosion, transport, and deposition processes on the continental shelf through state of the art observational techniques in both fine grained and sandy environmen...
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Our research program focuses on identifying and quantifying sediment erosion, transport, and deposition processes on the continental shelf through state of the art observational techniques in both fine grained and sandy environments. In sandy environments our goal is to understand the detailed interactions and feedbacks between hydrodynamics, bedforms, and the resulting sand transport. In fine grained such as the environments, Eel River shelf we have been investigating the role of gravitationally forced fluid mud flows in the wave boundary layer as a cross-shore transport mechanism. In certain environments bedload or near bottom suspended load can be the dominant mode of sand transport. In particular, these modes of sediment transport can have important impacts in terms of understanding erosion and deposition mechanisms in coarser sand environments with active bedform processes. These bedform processes, which may be forced by bedload transport, have been observed to change the local seafloor elevation tens of centimeters in time scales of hours to days. However, there is a lack of suitable observational techniques to measure bedload and near bottom suspended sand transport and their relationship to the hydrodynamic forcing. Therefore, we are developing and testing acoustic Doppler instrumentation that can quantitatively measure the bedload and near bottom suspended load flux magnitude and direction on a rapid time scale and its relationship to the hydrodynamic forcing. The approach for this project is based on a combination of modeling sensor geometry and response and testing actual systems in laboratory and field environments. The modeling effort will be used to guide development of sensor geometries and signal processing schemes. These will then tested using the components of Coherent Doppler Profiler developed at Dalhousie University.
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摘要 :
Sediment traps were deployed to sample vertical fluxes of particulate matter both immediately above and with the nepheloid layer on the continental slope and rise of the western North Atlantic. The data from the traps are used to ...
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Sediment traps were deployed to sample vertical fluxes of particulate matter both immediately above and with the nepheloid layer on the continental slope and rise of the western North Atlantic. The data from the traps are used to estimate the settling flux of particles and to attempt to distinguish between the primary flux (settling material from the upper water column) and the resuspended flux (settling material that has been resuspended from some region of the sea floor). From these data and from measurements of the net nepheloid standing crop of particles, estimates of the mean residence time for particles resuspended in the nepheloid layer are on the order of weeks to months from 15 to 500 m above bottom. Horizontal advection and diffusion are more important than vertical mixing in maintaining that upper portion of the nepheloid layer.
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摘要 :
The long-term goal of the sediment dynamics component of STRATAFORM is to link sediment transport processes on the continental shelf and slope to the formation and preservation of event beds in sediment deposits. Our objective is ...
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The long-term goal of the sediment dynamics component of STRATAFORM is to link sediment transport processes on the continental shelf and slope to the formation and preservation of event beds in sediment deposits. Our objective is to investigate sediment dispersal mechanisms on the continental shelf and slope. We have maintained long-term monitoring instrumentation in support of these investigations.
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摘要 :
To improve our capabilities for measuring and predicting erosion rates, sediment flux, water clarity and bed strength in muddy coastal environments, particularly with respect to their evolution through time on tidal flats.
摘要 :
The goals of this research are to develop greater understanding of the links between floc dynamics and the generation of sedimentary facies on the continental shelf. In particular, we seek greater understanding of the dynamics und...
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The goals of this research are to develop greater understanding of the links between floc dynamics and the generation of sedimentary facies on the continental shelf. In particular, we seek greater understanding of the dynamics underlying the sand-mud transition through investigation of how flocculation affects the transport and deposition of fine-grained sediments.
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摘要 :
The long-term goal of the sediment dynamics component of STRATAFORM is to link sediment transport processes on the continental shelf and slope to the formation and preservation of event beds in sediment deposits.
