The impact of marine shallow-water hydrothermal venting on arsenic and mercury accumulation by seaweed Sargassum sinicola in Concepcion Bay, Gulf of California

2013 ◽  
Vol 15 (2) ◽  
pp. 470 ◽  
Author(s):  
María Luisa Leal-Acosta ◽  
Evgueni Shumilin ◽  
Nicolai Mirlean ◽  
Francisco Delgadillo-Hinojosa ◽  
Ignacio Sánchez-Rodríguez
Keyword(s):  
Shallow Water ◽  
Gulf Of California ◽  
Mercury Accumulation ◽  
The Impact ◽  
Hydrothermal Venting

scholarly journals Paleoenvironment of the Lower–Middle Cambrian Evaporite Series in the Tarim Basin and Its Impact on the Organic Matter Enrichment of Shallow Water Source Rocks

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 659
Author(s):  
Mingyang Wei ◽  
Zhidong Bao ◽  
Axel Munnecke ◽  
Wei Liu ◽  
G. William M. Harrison ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shallow Water ◽  
Tarim Basin ◽  
Water Environment ◽  
Water Source ◽  
Major Elements ◽  
Source Rocks ◽  
Middle Cambrian ◽  
Sedimentary Environments ◽  
The Impact

Just as in deep-water sedimentary environments, productive source rocks can be developed in an evaporitic platform, where claystones are interbedded with evaporites and carbonates. However, the impact of the paleoenvironment on the organic matter enrichment of shallow water source rocks in an evaporite series has not been well explored. In this study, two wells in the central uplift of the Tarim Basin were systematically sampled and analyzed for a basic geochemical study, including major elements, trace elements, and total organic carbon (TOC), to understand the relationship between TOC and the paleoenvironmental parameters, such as paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity. The results show that the Lower–Middle Cambrian mainly developed in a fluctuating salinity, weak anoxic to anoxic, continuous dry and hot, and proper shallow water environment. The interfingering section of evaporites, carbonates, and claystones of the Awatag Fm. have higher paleoproductivity and higher enrichment of organic matter. Paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity jointly control the organic matter enrichment of shallow water source rocks in the evaporite series. The degree of enrichment of organic matter in shallow water source rocks first increases and then decreases with the increase in paleosalinity. All the samples with high content of organic matter come from the shallower environment of the Awatag Fm.

scholarly journals Measuring the Impact of Observations on the Predictability of the Kuroshio Extension in a Shallow-Water Model

2012 ◽  
Vol 42 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Werner Kramer ◽  
Henk A. Dijkstra ◽  
Stefano Pierini ◽  
Peter Jan van Leeuwen
Keyword(s):  
Shallow Water ◽  
Particle Filtering ◽  
Predictive Power ◽  
Kuroshio Extension ◽  
Water Model ◽  
Ensemble Prediction ◽  
Shallow Water Model ◽  
One Year ◽  
The Impact ◽  
The Kuroshio

Abstract In this paper, sequential importance sampling is used to assess the impact of observations on an ensemble prediction for the decadal path transitions of the Kuroshio Extension. This particle-filtering approach gives access to the probability density of the state vector, which allows the predictive power—an entropy-based measure—of the ensemble prediction to be determined. The proposed setup makes use of an ensemble that, at each time, samples the climatological probability distribution. Then, in a postprocessing step, the impact of different sets of observations is measured by the increase in predictive power of the ensemble over the climatological signal during one year. The method is applied in an identical-twin experiment for the Kuroshio Extension using a reduced-gravity shallow-water model. This study investigates the impact of assimilating velocity observations from different locations during the elongated and the contracted meandering states of the Kuroshio Extension. Optimal observation locations correspond to regions with strong potential vorticity gradients. For the elongated state the optimal location is in the first meander of the Kuroshio Extension. During the contracted state it is located south of Japan, where the Kuroshio separates from the coast.

Overcoming the challenges of a shallow-water sparse wide-azimuth survey to improve deep reservoir imaging in the East China Sea

2019 ◽  
Vol 38 (8) ◽  
pp. 610-616
Author(s):  
Yun Wei ◽  
Hua Chen ◽  
Senqing Hu ◽  
Peipei Deng ◽  
Yongdeng Xiao ◽  
...  
Keyword(s):  
Shallow Water ◽  
East China Sea ◽  
Three Dimensional ◽  
Water Layer ◽  
Velocity Model ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
Well Data ◽  
The Impact

A new broadband wide-azimuth towed-streamer (WATS) survey was acquired to better resolve reservoir compartments in a shallow-water region of the East China Sea. To offset the shortcomings of narrow-azimuth acquisition along the strike direction, two vessels were added side-by-side as additional source vessels to form the WATS acquisition geometry for this survey. This WATS acquisition was much sparser than typical WATS surveys used in deepwater environments due to its one-sided configuration. The combination of sparse acquisition, shallow water, and deep targets set the challenge of how to optimally reveal the potential of side-gun data to improve the final image. Three-dimensional effects and severe aliasing in the crossline direction pose significant challenges for side-gun data processing. We present a comprehensive workflow to resolve these challenges consisting of 3D deghosting, 3D model-based water-layer demultiple, 3D surface-related multiple elimination, and 4D regularization for sparse and shallow-water wide-azimuth data. A tilted orthorhombic velocity model is built with better constraints from the wide-azimuth data, leading to improved fault positioning and imaging. Side-gun data clearly enhance the final target reservoir image and tie better with well data due to improved illumination. A new channel is discovered based on interpretation from the inverted VP/VS, explaining the previous incorrect prediction for one failed well that was drilled into a thinner and shallower channel unconnected to the main reservoir. An analysis of the impact of side-gun data from different offsets and azimuths shows that better azimuthal distribution within middle offset ranges had a more significant impact than far offsets in the final image of this survey. This information provides valuable reference in similar geologic conditions for future acquisition designs.

scholarly journals Improvement of anisotropic porosity models with a merging technique

2018 ◽  
Vol 40 ◽  
pp. 06023
Author(s):  
Martin Bruwier ◽  
Pierre Archambeau ◽  
Sébastien Erpicum ◽  
Michel Pirotton ◽  
Benjamin Dewals
Keyword(s):  
Shallow Water ◽  
Flow Characteristics ◽  
Threshold Value ◽  
Computational Grid ◽  
Computational Time ◽  
Time Step ◽  
Shallow Water Models ◽  
The Cost ◽  
The Impact ◽  
Porosity Model

Anisotropic porosity shallow-water models are used to take into account detailed topographic information through porosity parameters multiplying the various terms of the shallow-water equations. A storage porosity is assigned to each cell to reflect the void fraction in the cell and a conveyance porosity is used at each edge to reproduce the impact of subgrid obstacles on the flux terms. To guaranty the numerical stability, the time step depends on the value of the porosity parameters. This may hamper severely the computational efficiency in the presence of cells with low values of storage porosity. Cartesian grids are particularly sensitive to such a case since the meshing stems directly from the choice of the grid size. In this paper, this problem is addressed by using an original merging technique consisting in merging cells with a storage porosity lower than a threshold value with neighbouring cells. The model was tested for modelling a prismatic channel with different orientations between the Cartesian computational grid and the channel direction. The results show that the standard anisotropic porosity model (without merging) improves the reproduction of the flow characteristics; but at the cost of a significantly higher computational time. In contrast, the computational time is drastically reduced and the accuracy preserved when the merging technique is used with the porosity model.

Influence of Wave Shape on the Impact of Shallow-Water Waves on Vertical Walls

2006 ◽  
Author(s):  
Claudio Zanzi ◽  
Pablo Go´mez ◽  
Julia´n Palacios ◽  
Joaqui´n Lo´pez ◽  
Julio Herna´ndez
Keyword(s):  
Shallow Water ◽  
Level Set ◽  
Water Waves ◽  
High Speed ◽  
Numerical Study ◽  
Local Level ◽  
Wave Shape ◽  
Shallow Water Waves ◽  
Vertical Walls ◽  
The Impact

A numerical study of the impact of shallow-water waves on vertical walls is presented. The air-liquid flow was simulated using a code for incompressible viscous flow, based on a local level set algorithm and a second-order approximate projection method. The level set transport and reinitialization equations were solved in a narrow band around the interface using an adaptive refined grid. The wave is assumed to be generated by a plunger which is accelerated in an open channel containing water. An arbitrary Lagrangian-Eulerian method was used to take into account the relative movement between the plunger and the end wall of the channel. The evolution of the free surface was visualized using a laser light sheet and a high-speed camera, with a sampling frequency of 1000 Hz. Several simulations were carried out to investigate the influence of the shape of the wave approaching the wall on the relevant quantities associated with the impact. The wave shape just before the impact was changed varying the total length of the channel. The results are compared with experimental results and with results obtained by other authors.

scholarly journals Effects of temperature and hypoxia on respiration, photorespiration, and photosynthesis of seagrass leaves from contrasting temperature regimes

2020 ◽  
Vol 77 (6) ◽  
pp. 2056-2065
Author(s):  
Lina M Rasmusson ◽  
Pimchanok Buapet ◽  
Rushingisha George ◽  
Martin Gullström ◽  
Pontus C B Gunnarsson ◽  
...  
Keyword(s):  
Shallow Water ◽  
Mitochondrial Respiration ◽  
Elevated Temperatures ◽  
Photosynthetic Apparatus ◽  
Coastal Ecosystems ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Photosynthetic Oxygen Evolution ◽  
Oxygen Levels ◽  
The Impact

Abstract In near-future climate change scenarios, elevated ocean temperatures with higher and more frequent peaks are anticipated than at present. Moreover, increased eutrophication and higher primary and secondary productivity will affect the oxygen levels of shallow-water coastal ecosystems, creating hypoxic conditions that can be experienced regularly, especially in dense vegetated systems. These climate-related events may impose detrimental effects on the primary productivity of seagrass. To evaluate such effects, this study combined gas exchange measurements with pulse amplitude-modulated fluorometry to assess the impact of short-time exposure to a range of water temperatures at ambient and low-oxygen levels on mitochondrial respiration, chlorophyll fluorescence (based on the Fv/F0 ratio), photosynthetic oxygen evolution, and photorespiration in leaf segments of the temperate seagrass Zostera marina and the tropical seagrass Thalassia hemprichii. We found that mitochondrial respiration in both Z. marina and T. hemprichii increased with higher temperatures up to 40°C and that low O2 caused significantly reduced respiration rates, particularly in T. hemprichii. Elevated water temperature had a clear negative effect on the Fv/F0 of both seagrass species, indicating damage or inactivation of the photosynthetic apparatus, even when light is not present. Moreover, damage to the photosynthetic apparatus was observed as an effect of elevated temperature combined with low O2 during darkness, resulting in subsequent lower photosynthesis in light. Photorespiration was present, but not promoted by increased temperature alone and will thus not further contribute to productivity losses during warmer events (when not carbon limited). This study demonstrates the negative impact of hypoxic stress and elevated temperatures on seagrass productivity, which may influence the overall health of seagrass plants as well as oxygen and carbon fluxes of shallow-water coastal ecosystems in warmer climate scenarios.

scholarly journals Middle Eocene Rhodoliths from Tropical and Mid-Latitude Regions

Diversity ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 117 ◽  
Author(s):  
Julio Aguirre ◽  
Juan C. Braga ◽  
Victoriano Pujalte ◽  
Xabier Orue-Etxebarria ◽  
Edward Salazar-Ortiz ◽  
...  
Keyword(s):  
Shallow Water ◽  
Middle Eocene ◽  
Taxonomic Composition ◽  
Coralline Algae ◽  
Fold Belt ◽  
Carbonate Platforms ◽  
Benthic Foraminifers ◽  
Tropical Areas ◽  
The Impact ◽  
Water Carbonate

During the greenhouse conditions prevailing in the early–middle Eocene, larger benthic foraminifers (LBF) spread out on carbonate platforms worldwide while rhodolith beds were scarcely represented. This reduction in rhodolith beds coincided with a relative decrease in coralline algal diversity and with a drastic decline of coral reef abundance. Middle Eocene rhodoliths from two tropical (San Jacinto Fold Belt in northern Colombia and Bahoruco Peninsula in the Dominican Republic) and two mid-latitude (Salinas Menores Ravine and Sierra del Zacatín in Southern Spain) localities were studied. Rhodolith rudstones in the tropical areas accumulated on relatively deep (several tens of meters) platform environments and were also redeposited in deeper settings downslope. In Salinas Menores, rhodoliths are dispersed in planktic foraminifer-rich marls. Miliolids are common in the infilling of constructional voids in these rhodoliths, indicating that they originally grew in shallow-water inner-shelf settings and afterwards they were transported to deeper environments. In Sierra del Zacatín, rhodoliths are scarce and coralline algae mainly occur as crusts attached to and intergrowing with corals. Here, LBF dominated shallow-water carbonate platforms. In terms of taxonomic composition, coralline algae of the order Hapalidiales are the most abundant in the study areas, followed by Sporolithales. The order Corallinales is poorly represented except in Salinas Menores, where it is relatively abundant and diverse. The impact of high temperatures due to high levels of atmospheric CO2 during the Eocene and widespread oligotrophic conditions, which favored formation of LBF-rich lithofacies, might account for the low abundance of rhodolith beds at mid and high latitudes. In contrast, the more productive equatorial regions would have favored the formation of rhodolith beds.

scholarly journals Adjustment of Transceiver Lever Arm Offset and Sound Speed Bias for GNSS-Acoustic Positioning

2019 ◽  
Vol 11 (13) ◽  
pp. 1606 ◽  
Author(s):  
Guanxu Chen ◽  
Yang Liu ◽  
Yanxiong Liu ◽  
Ziwen Tian ◽  
Jingnan Liu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Sound Velocity ◽  
Functional Model ◽  
Systematic Errors ◽  
Vertical Coordinate ◽  
Sea Trial ◽  
Lever Arm ◽  
Main Technique ◽  
The Impact ◽  
Velocity Bias

Global Navigation Satellite System––Acoustic (GNSS-A) positioning is the main technique for seafloor geodetic positioning. A transceiver lever arm offset and sound velocity bias in seawater are the main systematic errors of the GNSS-A positioning technique. Based on data from a sea trial in shallow water, this paper studies the functional model of GNSS-A positioning. The impact of the two systematic errors on seafloor positioning is analysed and corresponding processing methods are proposed. The results show that the offset in the lever arm measurement should be parameterised in the observation equation. Given the high correlation between the vertical lever arm offset and the vertical coordinate of the seafloor station, a sample search method was introduced to fix the vertical offset correction. If the calibration of the sound velocity profiler cannot be ensured, the correction parameter of the sound velocity bias should be solved. According to the refined functional model and corrections, the position of a seafloor station in shallow water can be determined with a precision of better than 1 cm.

THE IMPACT OF HIGH-ENERGY STORMS ON SHALLOW-WATER NAUTILUS (CEPHALOPODA) TAPHONOMY, LIFOU (LOYALTY ISLANDS)

Palaios ◽  
2014 ◽  
Vol 29 (7) ◽  
pp. 348-362 ◽  
Author(s):  
D. I. HEMBREE ◽  
R. H. MAPES ◽  
C. GOIRAN
Keyword(s):  
Shallow Water ◽  
High Energy ◽  
The Impact

Submarine preservation of massive tabular ground ice by coastal retrogressive thaw slumps

2020 ◽  
Author(s):  
Brian Moorman
Keyword(s):  
Shallow Water ◽  
Thermal Conditions ◽  
Information Modeling ◽  
The Arctic ◽  
Ground Ice ◽  
Sedimentary Architecture ◽  
Coastal Retreat ◽  
The Stability ◽  
Ground Penetrating ◽  
The Impact

<p><span>Around the Arctic Ocean there are many stretches of coastline composed of ice-rich sediments. With the dramatic climatic, oceanic and terrestrial changes that are currently occurring, there is considerable concern over the stability of these coasts and how they are being altered. With the complexity that permafrost conditions add to the coastal setting, modelling erosion involves a more detailed understanding of the physical and thermal conditions as well as the sedimentological and wave action processes. This research examines the role that the shallow water energy balance plays in preserving sub-bottom massive ice as the coastline retreats and the implications it has for secondary subsea disturbance once the water depth increases.</span></p><p><span>The study area was Peninsula Point which is approximately 10 km west of Tuktoyaktuk, NWT, Canada. The massive ice and retrogressive thaw slumps at this location are some of the more dramatic examples of the impact of ice-rich permafrost on coastal processes in the Arctic. By mapping the area with satellite and aerial imagery and conducting repeat ground penetrating radar surveys (GPR) over a 30 year period, the long-term character of coastal retreat above, and below, the water line is revealed. In winter, the GPR was pulled behind a snowmobile along transects on land, across the shoreline and out onto the near shore area of the Beaufort Sea. This provided the stratigraphic continuity between the terrestrial and sub-sea settings. The GPR revealed the massive ice and sedimentary architecture, from which vertical and lateral relationships to the coastline were determined. The roles of erosion, re-sedimentation and shallow-water thermodynamics in the degradation and preservation of massive ground ice were revealed. Using this new information, modeling of the coastal retreat and sediment contributions to the ocean demonstrated a much more complex system than previously assumed.</span></p>

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