scholarly journals DEFORMATION OF ROTATIONAL TIDAL CURRENTS IN SHALLOW COASTAL WATER

1970 ◽  
Vol 1 (12) ◽  
pp. 130
Author(s):  
Harold Gohren
Keyword(s):  
Bottom Sediment ◽  
North Sea ◽  
Coastal Water ◽  
Current System ◽  
Tidal Currents ◽  
Elbe Estuary ◽  
Residual Currents ◽  
A Current

Along gently sloping coasts of seas having rotary tidal currents, the symmetry of the rotary current is interrupted where the water is shallow As a result, residual counter currents are formed The dynamics of such a current system are described based on current measurements in the Elbe Estuary (southeastern North Sea) The residual currents of this area result in the movement of bottom sediment and are most likely responsible for a series of similar appearing morphologic features.

The hydrography and plankton of the Moray Firth

1986 ◽  
Vol 91 ◽  
pp. 37-56 ◽  
Author(s):  
J. A. Adams ◽  
J. H. A. Martin
Keyword(s):  
North Sea ◽  
Coastal Water ◽  
Standing Stock ◽  
Dry Weight ◽  
Residual Currents ◽  
The North ◽  
Southern Shore ◽  
Moray Firth ◽  
Standing Stocks ◽  
Mixed Water

SynopsisThe Moray Firth forms part of the north British coastal area of the North Sea and is distinguished by its depth, hydrography and plankton from the offshore northern North Sea. The 35·0 or 35·1 × 103 isohaline can be taken as the boundary between the two areas.Geographical and seasonal variations in temperature and salinity are described in terms of a belt of low salinity coastal water in the inner firth and along its southern shore and of “mixed” water to the north and east. During the winter the “mixed” water is warmer than the coastal water, during the summer it is colder. Tidal streams are dominantly semi-diurnal, relatively weak in the inner firth and relatively strong in the outer firth. Residual currents are largely wind driven, and some are caused by tidal effects.Geographical variation in the seasonal changes in the phytoplankton standing stock is related to water column stratification. The early spring standing stocks are highest in the inner firth and off the southern shore. During the summer and early autumn, phytoplankton is most abundant below the pycnocline. Average zooplankton standing stocks increase from 0·2–0·6 g dry weight (100m3) 1 in winter to 1.0 g (100m3) 1 exceptionally 4·5 g (100m3) 1. in summer. Standing stocks in November–December range from 0·3 to 1·8 g (100m3) 1.

Currents in Johnstone Strait, British Columbia: Supplemental Data on the Vancouver Island Side

1977 ◽  
Vol 34 (5) ◽  
pp. 697-703 ◽  
Author(s):  
Richard E. Thomson
Keyword(s):  
Cross Sections ◽  
Volume Transport ◽  
Tidal Currents ◽  
Estuarine Circulation ◽  
Phase Lag ◽  
Mean Flow ◽  
Tidal Constituent ◽  
Residual Currents ◽  
Large Phase ◽  
A Current

Records from a current meter recently found adrift after 3 yr have been used to complete previously published cross sections of mean flow and tidal currents in Johnstone Strait. The new plots emphasize the cross-channel asymmetry of the estuarine circulation and the large phase lag of the upper layer current relative to the bottom currents for the diurnal (K1) tidal constituent. A recalculation of the net volume transport shows that its magnitude and direction remain undeterminable to the order of ± 103 m3∙s−1. Key words: tidal currents, residual currents, estuarine circulation, Johnstone Strait

MAPPING TIDAL CURRENTS AND RESIDUAL CURRENTS BY USE OF COASTAL ACOUSTIC TOMOGRAPHY

2017 ◽  
Author(s):  
Xiao-Hua Zhu ◽  
Xiao-Hua Zhu ◽  
Ze-Nan Zhu ◽  
Ze-Nan Zhu ◽  
Xinyu Guo ◽  
...  
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Mean Amplitude ◽  
Momentum Equation ◽  
Tidal Currents ◽  
Acoustic Tomography ◽  
Mean Values ◽  
Residual Currents ◽  
Water Depths ◽  
Deep Area

A coastal acoustic tomography (CAT) experiment for mapping the tidal currents in the Zhitouyang Bay was successfully carried out with seven acoustic stations during July 12 to 13, 2009. The horizontal distributions of tidal current in the tomography domain are calculated by the inverse analysis in which the travel time differences for sound traveling reciprocally are used as data. Spatial mean amplitude ratios M2 : M4 : M6 are 1.00 : 0.15 : 0.11. The shallow-water equations are used to analyze the generation mechanisms of M4 and M6. In the deep area, velocity amplitudes of M4 measured by CAT agree well with those of M4 predicted by the advection terms in the shallow water equations, indicating that M4 in the deep area where water depths are larger than 60 m is predominantly generated by the advection terms. M6 measured by CAT and M6 predicted by the nonlinear quadratic bottom friction terms agree well in the area where water depths are less than 20 m, indicating that friction mechanisms are predominant for generating M6 in the shallow area. Dynamic analysis of the residual currents using the tidally averaged momentum equation shows that spatial mean values of the horizontal pressure gradient due to residual sea level and of the advection of residual currents together contribute about 75% of the spatial mean values of the advection by the tidal currents, indicating that residual currents in this bay are induced mainly by the nonlinear effects of tidal currents.

Metabolic alkalinity release from the Elbe estuary to the North Sea

2021 ◽  
Author(s):  
Mona Norbisrath ◽  
Jeannette Hansen ◽  
Kirstin Dähnke ◽  
Tina Sanders ◽  
Justus E. E. van Beusekom ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Water Column ◽  
Fresh Water ◽  
North Sea ◽  
Total Alkalinity ◽  
Elbe Estuary ◽  
Metabolic Processes ◽  
The North ◽  
Carbon Species ◽  
The North Sea

<p>The Elbe is the largest river entering the German Bight. Its estuary is a heavily used waterway connecting the sea to Germany’s biggest port in Hamburg. The Elbe navigation channel is continuously dredged, and agricultural fertilizer input from the catchment ensuing large phytoplankton blooms in the river Elbe exerts additional anthropogenic pressure. Biogeochemistry in the estuary is additionally governed by the North Sea and its strong tidal cycles, which ensure an exchange of fresh and marine waters.</p><p>The aims were to quantify the release of the carbon species total alkalinity (TA) and dissolved inorganic carbon (DIC) along the Elbe estuary, and to estimate the contribution of aerobe and anaerobe metabolic processes. Therefore, we used water samples collected continuously during a cruise in June 2019, to measure TA and DIC, and the stable isotopes of nitrate. We applied mass balances, to characterize the metabolic activity and detect their effect on the carbon species</p><p>The Elbe estuary could be subdivided into two parts: 1) an outer marine driven part, which is dominated by conservative mixing, also visible in higher TA than DIC values, and 2) an inner fresh water part in which metabolic processes play an important role.</p><p>We found a strong increase in TA and DIC (several hundred µmol kg<sup>-1</sup>) in the Hamburg port area, with higher DIC than TA values. We unraveled the water column impacts of nitrification and denitrification on TA and DIC by analyzing the stable isotopes δ<sup>15</sup>N-NO<sub>3</sub><sup>-</sup> and δ<sup>18</sup>O-NO<sub>3</sub><sup>-</sup>, and identified water column nitrification as a dominant pelagic process in the port of Hamburg and in the fresh water part further downstream. Because nitrification cannot explain the significant increase of TA and DIC in the port region, anaerobic processes such as denitrification in the sediment also appear to play an important role.</p><p> </p>

scholarly journals Towards End-2-End modelling in a consistent NPZD-F modelling framework (ECOSMOE2E_vs1.0): Application to the North Sea and Baltic Sea

2018 ◽  
Author(s):  
Ute Daewel ◽  
Corinna Schrum ◽  
Jed Macdonald
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Food Chain ◽  
Current System ◽  
Ecosystem Model ◽  
Trophic Levels ◽  
Production Model ◽  
Fish Mortality ◽  
Fish Biomass ◽  
Trophic Chain

Abstract. Coupled physical-biological models usually resolve only parts of the trophic food chain and hence, run the risk of neglecting relevant ecosystem processes. Additionally, this imposes a closure term problem at the respective “ends” of the considered trophic levels. Here we propose a consistent NPZD-Fish modelling approach (ECOSMO E2E) to address the above-mentioned problem in lower trophic ecosystem modelling, and to understand how the implementation of higher trophic levels in a NPZD model affects the simulated response of the combined North Sea and Baltic Sea ecosystem. On the basis of the coupled ecosystem model ECOSMO II we implemented one functional group that represents fish and one group representing macrobenthos in the 3d model formulation. Both groups are linked to the lower trophic levels and to each other via predator-prey relationships. The model allows investigating bottom-up impacts on primary and secondary production and cumulative fish biomass dynamics, but also top-down mechanisms on the lower trophic level production. Model results for a ten-year long simulation period (1980–1989) were analysed and discussed with respect to the observed pattern. To address the relevance of the newly implemented trophic levels for the simulated model response, we compare the performance of the ECOSMO E2E to a respective truncated NPZD model (ECOSMO II), which simulated the same time period. Additionally, we performed scenario tests to analyse the new role of the zooplankton mortality closure term in the truncated NPZD and the fish mortality term in the end-to-end model, which summarizes pressure imposed on the system by fisheries and mortality imposed by apex predators. We found that the model-simulated macrobenthos and fish spatial and seasonal pattern agree well with current system understanding. Considering a dynamic fish component in the ecosystem model resulted in slightly improved model performance with respect to representation of spatial and temporal variations in nutrients, changes in modelled plankton seasonality and nutrient profiles. Model sensitivity scenarios showed that changes in the zooplankton mortality parameter are transferred up and down the trophic chain with little attenuation of the signal, while major changes in fish mortality and in fish biomass cascade down the food chain.

Resuspension of benthic fluff by tidal currents in deep stratified waters, northern North Sea

2002 ◽  
Vol 48 (4) ◽  
pp. 259-269 ◽  
Author(s):  
C.F Jago ◽  
S.E Jones ◽  
R.J Latter ◽  
R.R McCandliss ◽  
M.R Hearn ◽  
...  
Keyword(s):  
North Sea ◽  
Tidal Currents ◽  
Northern North Sea

Fault Detection With NURBs-Based Metamodels

2006 ◽  
Author(s):  
Cameron J. Turner ◽  
Abiola M. Ajetunmobi ◽  
Richard H. Crawford
Keyword(s):  
Current System ◽  
Cost Savings ◽  
Operating Conditions ◽  
Engineering Systems ◽  
Brushless Dc Motors ◽  
Brushless Dc ◽  
Dc Motors ◽  
Modern Engineering ◽  
Incipient Faults ◽  
A Current

Developing the ability for a system to self-monitor its condition is a desirable feature in many modern engineering systems. This capability facilitates a maintenance-as-needed rather than a maintenance-as-scheduled paradigm, offering potential efficiency improvements and corresponding cost savings. By using continuously updated Non-Uniform Rational B-spline (NURBs) metamodels of system performance to monitor the system condition, the onset of incipient faults can be detected by comparison to a self-generated as-built system metamodel, providing a basis for determining off-normal operating conditions. This capability is demonstrated for three distinct fault conditions prevalent in brushless DC motors. The results show that this technique can be used to develop an as-built system metamodel, develop a current system model during system operation, and detect the presence of an incipient fault condition despite the compensation provided by a feedback control system.

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