Tidal vorticity and residual circulation

doi:10.1016/0198-0149(81)90062-5

Deep Sea Research Part A. Oceanographic Research Papers

Volume 28, Issue 3, March 1981, Pages 195-212

https://doi.org/10.1016/0198-0149(81)90062-5 Get rights and content

Abstract

Circulatory residuals, generated by the non-linear interaction of tidal oscillatory flow and topography, are studied by examining the advection of the vorticity of the tidal flow. The time histories of the vorticity of individual fluid elements are obtained from a simple Lagrangian model and used to obtain the Eulerian spatial distribution of residual vorticity. Different vorticity generating mechanisms are identified, and typical magnitudes and spatial scales of the residual circulation associated with them are tabulated. The possibility of thus estimating the magnitude and extent of residual flows generated by topographic features is illustrated by considering the example of the Hurd Deep in the English Channel. The implications of the results for the numerical modelling of shelf seas are considered.

References (8)

J.M. Huthnance
Tidal current asymmetries over the Norfolk Sandbanks
Estuarine and Coastal Marine Science
(1973)
N.S. Heaps
Linearized vertically-integrated equations for residual circulation in coastal seas
Deutsche Hydrographische Zeitschrift
(1978)
J.M. Huthnance
On mass transports generated by tides and long waves
Journal of Fluid Mechanics
(1980)
E. Maier-Reimer
Residual circulation in the north Sea due to the M₂ tide and mean annual wind stress
Deutsche Hydrographische Zeitschrift
(1977)

There are more references available in the full text version of this article.

Cited by (141)

Hydrodynamic modelling in marginal and coastal seas — The case of the Adriatic Sea as a permanent laboratory for numerical approach
2022, Ocean Modelling
Understanding the water circulation in oceans and coastal seas is among the key topics of oceanographic and climate research. Hydrodynamic studies form the basis for many oceanographic subjects, whether sediment transport, morphology, water quality, ecological and climate changes are being investigated. Hydrodynamic modelling of oceans and coastal seas has become a fundamental tool for describing the dynamics of marine environments, revealing the human impact on the sea and promoting sustainable development of marine resources. By complementing – through data assimilation – more and more diffuse and integrated global and regional observing systems (composed of coastal gauges, moorings, buoys, satellites, drifters), hydrodynamic models provide a deterministic 4D view of the ocean state. In this context, the semi-enclosed Adriatic Sea represents a natural long-standing laboratory for hydrodynamic modelling. The peculiar historical, morphological and oceanographic characteristics of this basin and its complex coastline stimulated over decades the development and application of several ocean and coastal models. In this work, we review different aspects of hydrodynamic modelling covered by the literature, highlighting the wide variety of model applications carried out in the Adriatic Sea which could serve as examples for semi-enclosed, marginal and coastal seas worldwide. Within the scope of the review, we find that although significant progress has been made over the last few decades, most of the modelling studies underrate the importance of a detailed representation of the land-coastal-sea fluxes. We list a set of recommendations that can be used as guidelines for model implementation to broaden the applicability of hydrodynamic models in future studies. Finally, we discuss the remaining questions that still need to be further explored.
The Irish Sea bed load parting zone: Is it a mid-sea hydrodynamic phenomenon or a geological theoretical concept?
2021, Estuarine, Coastal and Shelf Science
Citation Excerpt :
Most recently, modelled residual currents and their vorticity reveals potential circulatory flow patterns around sand banks in the Irish Sea (Horrillo-Caraballo et al., 2021). Residual gyre patterns around headlands and sandbanks result from the transfer of vorticity from the tide to residual flow (Horrillo-Caraballo et al., 2021; Robinson, 1981; Zimmerman, 1981). Evidence of strong positive vorticity over sandbanks and negative vorticity over associated channels off the east coast of Ireland (e.g. Arklow Bank) indicate relatively strong residual gyre patterns in this region (Horrillo-Caraballo et al., 2021).
On tidally-dominated shelf seas, hydrodynamic flow exerts shear stress on the seabed, inducing sediment transport and seabed evolution. Net sediment transport pathways and associated bed load partings zones (the ‘head’ of sediment transport pathways) are important elements of this sediment dispersal process. A robust comprehension of these dynamics on a local and regional scale are crucial for a range of offshore activities, including the rapidly growing offshore renewable energy industry. Previous studies infer a bedload parting zone (BLP) in the central Irish Sea, yet this predominantly bedform-derived BLP remains to be fully supported by underlying hydrodynamics. This study reviews how sediment transport pathways in the Irish Sea are defined to date, investigates whether a hydrodynamic regime capable of supporting this inferred BLP exists, and if proven, aims to elucidate its origin.
Tidal asymmetry indicators, derived from the phase and amplitude relationships of numerically modelled M₂ and M₄ tidal constituents, reveal the existence of a symmetrical tidal zone in the proximity of the inferred BLP. New numerically modelled residual tidal current and bed shear stress vectors reinforce the presence of this distinct tidal character change and further reveal strong opposing tidal flows extending from this region, thus supporting the presence of a tidal flow capable of producing divergent bedload patterns. Analysis of tidal propagation through the Irish Sea Basin concludes that the origin of the BLP is mainly attributed to the intersection of the north and south tidal fronts at an inclined angle due to Coriolis Forcing and coastline interactions. Minor factors impacting the shape and location of the BLP are the change in tidal character at (a) abrupt bathymetry changes, (b) headlands and intricate coastline topography, and (c) large-scale constrictions. Further investigation into localised morphodynamics is needed. These findings are highly valuable to efficient marine spatial planning, underpinning a movement towards a climate resilient economy. The integrated approach used in this body of work can be applied to tidally-dominated continental shelves beyond the Irish Sea.
An assessment of residence and influence times in Xiamen Bay, China
2021, Estuarine, Coastal and Shelf Science
Water transport time scales are important indicators to assess the renewal of substance inside coastal embayments. Estimates of water renewal efficiency represented by residence and influence times in Xiamen Bay were made via a series of numerical experiments, using the instantaneous tracer injection method. It was found that the average e-folding threshold residence time in the bay is approximately 16.5 days, and that the residence time increases near the entrances to land because water exchange between the bay and the Taiwan Strait is the dominant water-renewal process. The seawater influence time has a similar spatial distribution to the residence time. The freshwater influence time is much shorter in the western region of the bay than in the eastern region, which shows that the influence of Jiulong River freshwater is largely restricted to the western region. The changes in the residence and influence times reveal that increased river discharge mainly accelerates water renewal in the western region of the bay, whereas increased tides mainly accelerate water renewal in the eastern region and the northern part of the western region. The drivers of water renewal were examined using effective transport velocities that were defined based on the decomposition of tracer flux, and showed that tidal residual flow determines the extent of water renewal in Xiamen Bay. The estimation of residence time is sensitive to the operation of instantaneous method. The release of tracer at spring tide results in a shorter residence time and the use of a small threshold can improve the consistency of estimated threshold residence times.
A new perspective on meso-scale shoreline dynamics through data-driven analysis
2019, Geomorphology
The twin ambits of climate change and coastal development have raised public awareness of shoreline management. Simultaneously, they have highlighted a gap in our understanding of sediment transport and morphodynamic processes at time and space scales appropriate for shoreline management purposes. Here, we analyse an exceptional set of beach surveys gathered over a period of twenty-two years along the Suffolk coast, eastern UK, that extends over approximately 80 km to investigate the meso-scale shoreline variations. The surveys have been made biannually along fixed transects spaced at approximately 1 km intervals as part of a strategic monitoring exercise undertaken by the coastal authorities to assist in shoreline management planning. Changes in beach volume, foreshore slope and shoreline position have been computed to investigate both spatial and temporal changes. The analysis reveals some distinct responses to the physical processes of tides and waves, anthropogenic interventions and geological controls. Neither a clear relationship between the presence of sea defences and beach response nor an ordered regional-scale shoreline movement are evident. Temporal variations in beach volumes and position provide a similarly complex picture with recessionary, accretionary and stable behaviour all apparent within the study site. There is evidence of quasi-cyclic behaviour at some locations as well as a reduction in variability over time-scales beyond approximately five years.
Coupling biophysical processes that sustain a deep subpopulation of Loxechinus albus and its associated epibenthic community over a bathymetric feature
2018, Estuarine, Coastal and Shelf Science
In order to contribute with more integrative strategies for better identify areas of high conservation priority we study the coupling of physical and biological processes that sustain a deep subpopulation of the most caught sea urchin (Loxechinus albus) worldwide and its associated epibenthic community over a bathymetric depression in southern Chile, which is surrounded by intensive anthropic activities. We used a remotely operated vehicle (ROV) to characterize the epibenthic community (organisms > 15 mm long) and substrate, up to a depth of 112 m in a submarine hole. Additionally, a combination of a towed and a moored Acoustic Doppler current Profiler (ADCP) was used to characterize current patterns. We found evidence that physical mechanisms transport and retain macro and micro material in the bottom of the hollow, and they contribute to homogenizing the habitat along the entire bathymetric gradient. These coupled processes allow i) that several species expand their bathymetric distribution range, ii) the existence of nursery areas for fishes, iii) that characteristic grazers in shallow habitats colonize greater depths, where filter feeders or DOM consumers generally represent the typical epifauna. We hypothesize that coupling of physical and biological processes on this bathymetric depression are key for bring on Loxechinus albus along the entire bathymetric gradient, who in turn is key to the community structure of the hollow. Given that this particular habitat is surrounded by intensive anthropic activities (eg. salmon aquaculture, mussel aquaculture, fishing, port) and a city, we suggest: Firstly, that monitoring should be undertaken in order to observe biodiversity changes in the bathymetric gradient, since it could be an indicator of conservation status. Secondly, that a proposal should be formulated to consider this zone as a Marine Protected Area.
Modelling the hydrodynamic and morphological impacts of a tidal stream development in Ramsey Sound
2018, Renewable Energy
A number of sites around the UK are being considered for development of tidal stream energy, one of which is Ramsey Sound off the coast of Pembrokeshire, South Wales. The Sound was used to test the prototype of the Delta Stream by Tidal Energy Ltd. After initial testing, a 10 MW tidal array was proposed at St David's Head. To investigate any possible environmental impacts of the array due to energy extraction, a case study of the Pembrokeshire coast was performed using a high-resolution depth averaged hydrodynamic model, Telemac2D, to investigate changes to hydrodynamics and morphodynamics. Results show that the proposed array of nine tidal energy converters will cause alterations to eddy propagation leading to changes in the velocity field up to 24 km from the tidal array. Changes in morphodynamics are predicted through alterations to the bed shear stress. Changes to the mean and maximum bed shear stress, over a 30-day period, are found to be more localised and extend 12 km from the array. These changes indicate that the proposed tidal array will lead to localised sediment accumulation and will act as a barrier to sediment transport, with potential consequences for the benthic ecology of the region.

View all citing articles on Scopus

View full text

Tidal vorticity and residual circulation

Abstract

Estuarine and Coastal Marine Science

Linearized vertically-integrated equations for residual circulation in coastal seas

Deutsche Hydrographische Zeitschrift

On mass transports generated by tides and long waves

Journal of Fluid Mechanics

Residual circulation in the north Sea due to the M2 tide and mean annual wind stress

Deutsche Hydrographische Zeitschrift

Residual circulation in the north Sea due to the M₂ tide and mean annual wind stress