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Tidal-stream energy resource can be predicted deterministically, provided tidal harmonics and turbine-device characteristics are known. Many turbine designs exist, all having different characteristics (e.g. rated speed), which creates uncertainty in resource assessment or renewable energy system-design decision-making. A standardised normalised tidal-stream power-density curve was parameterised with data from 14 operational horizontal-axis turbines (e.g. mean cut-in speed was ∼30% of rated speed). Applying FES2014 global tidal data (1/16° gridded resolution) up to 25 km from the coast, allowed optimal turbine rated speed assessment. Maximum yield was found for turbine rated speed ∼97% of maximum current speed (maxU) using the 4 largest tidal constituents (M2, S2, K1 and O1) and ∼87% maxU for a “high yield” scenario (highest Capacity Factor in top 5% of yield cases); with little spatial variability found for either. Optimisation for firm power (highest Capacity Factor with power gaps less than 2 h), which is important for problematic or expensive energy-storage cases (e.g. off-grid), turbine rated speed of ∼56% maxU was found – but with spatial variability due to tidal form and maximum current speed. We find optimisation and convergent design is possible, and our standardised power curve should help future research in resource and environmental impact assessment.

Acoustic telemetry was used to track salmon smolts during river migration and into the open marine coastal zone. We compared migration direction and speed with particle tracking simulations to test the hypothesis that marine migration pathways are defined by active swimming current following behaviour. Habitat-specific survival rates, movement speeds, depths and directions in riverine, estuarine, and coastal habitats were also quantified. Salmon post-smolts did not disperse at random as they entered the unrestricted, coastal zone of the North sea; rather they chose a common migration pathway. This was not the most direct route to marine feeding grounds (ca. 44° N); north in the direction of the prevailing currents. Particle modelling showed that the actual post-smolt migration route was best predicted by active swimming at 1.2 body length.sec.−1 at a bearing of 70° from north but not by current following behaviour. Fish migrating in larger groups and earlier in the migration period had increased migration success. We conclude that: post-smolts have preferred migration routes that are not predicted by the shortest direction to their ultimate destination; they do not simply use the current advantage to migrate; and that they actively swim, occasionally directly against the current prevailing at the time.

Primary production dynamics are strongly associated with vertical density profiles, which dictate the depth of stratification and mixed layers. Climate change and artificial structures (e.g. windfarms) are likely to modify the strength of stratification and vertical distribution of nutrient fluxes, especially in shelf seas where fine scale processes are important drivers, affecting the vertical distribution of phytoplankton. To understand the effect of physical changes on primary production, identifying the linkage between density and phytoplankton profiles is essential. Here, the ecological relevance of eight density layers (DLs) obtained by multiple methods that define three different portions of the pycnocline (above, centre, below) was evaluated to identify a valuable proxy for subsurface Chlorophyll-a (Chl-a mg m-3) concentrations. The associations of subsurface Chl-a with surface and deep mixing were investigated by hypothesizing the occurrence at the same depth of any DL and the maximum Chl-a layer (DMC) using Spearman correlation, linear regression, and a Major Axis analysis. Out of 1237 observations of the water column exhibiting a pycnocline, 78 % reported DMCs above the bottom mixed layer depth (BMLD). This suggests that the BMLD is a boundary trapping Chl-a in shallow waters (≤ 120 m). BMLD constantly described Chl-a vertical distribution despite surface mixing indicators, suggesting a significant contribution of deep mixing processes in supporting subsurface production under specific conditions (e.g. prolonged stratification, tidal cycle, and bathymetry). Using BMLD for defining subsurface Chl-a could be a valuable tool for understanding the spatiotemporal variability of Chl-a in shelf seas, representing a potential variable for ecological assessments.

Growing concern about the impacts of anthropogenic noise on marine life has led to a global increase in the number of acoustic monitoring programmes aiming to quantify underwater soundscapes. However, low-frequency measurements in coastal sites may be affected by flow noise that is not actually present in the environment, but is caused by tidal flow turbulence around the hydrophone. At present, there is no standard way of removing this contaminating noise. This study presents an approach to exclude tidal influences (flow noise and other tidal-related acoustic self-noise) on ambient sound measurements, using data recorded at ten Scottish coastal sites between 2013 and 2017, and with a focus on the 63 and 125 Hz 1/3-octave bands. The annual ambient sound pressure levels (SPL) of the full and “tidal influence excluded” datasets of the three most tidally affected sites were compared against hypothetical noise thresholds. For the 63 Hz 1/3-octave band, results revealed: Site-specific patterns in the amount of data excluded (28.2%–89.2%), decreases in SPL (0.7–8.5 dB), and differences in the percentage of time that noise thresholds were exceeded. The described approach may serve as a standardised way of excluding tidal influence on soundscape descriptors.

The environmental implications of tidal stream energy extraction need to be evaluated against the potential climate change impacts on the marine environment. Here, we study how hypothetical very large tidal stream arrays and a “business as usual” future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea. The Scottish Shelf Model, an unstructured grid three‐dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. Four scenarios have been modelled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). It is found that where tidal range is reduced a few cm by tidal stream energy extraction, it can help to counter extreme water levels associated with future sea level rise. Tidal velocities, and consequently tidal mixing, are also reduced overall by the action of the tidal turbine arrays. A key finding is that climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing, however the effect of climate change is an order of magnitude larger.

The tidal stream energy sector is now at the stage of deploying the world's first pre-commercial arrays of multiple turbines. It is time to study the environmental effects of much larger full-size arrays, to scale and site them appropriately. A theoretical array of tidal stream turbines was designed for the Pentland Firth (UK), a strait between Scotland and the Orkney Islands, which has very fast tidal currents. The practical power resource of a large array spanning the Pentland Firth was estimated to be 1.64 GW on average. The ocean response to this amount of energy extraction was simulated by an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) and analysed on both short-term and seasonal timescales. Tidal elevation mainly increases upstream of the tidal array, while a decrease is observed downstream, along the UK east coast. Tidal and residual flows are also affected: they can slow down due to the turbines action or speed up due to flow diversion and blockage processes, on both a local and regional scale. The strongest signal in tidal velocities is an overall reduction, which can in turn decrease the energy of tidal mixing and perturb the seasonal stratification on the NW European Shelf.

Seawater turbidity due to suspended particulate material (SPM) is an important property of a marine ecosystem, determining the underwater light environment and many aspects of biological production and ecology. SPM concentrations are largely determined by patterns of sediment resuspension from the seabed due to shear stress caused by waves and currents. Hence planning for the construction of large scale offshore structures which will alter regional hydrodynamics needs to consider the consequences for SPM concentrations. Here we develop a one-dimensional (vertical) model of SPM dynamics which can be used to scope the effects of changes in wave and tidal current properties at a site. We implement the model for a number of sites off the east coast of Scotland where we have extensive data sets to enable numerical parameter optimisation. The model performs well at simulating fluctuations in turbidity varying from flood-ebb tidal cycles, spring-neap cycles, storm wave events, and an annual cycle of SPM concentration which is attributed to seasonal consolidation of seabed sediments. Sensitivity analysis shows that, for the range of seabed sediment types in the study (water depth 16–50 m; mud content 0.006–0.380 proportion by weight), relatively large (50%) attenuations of tidal current speed are required to produce changes in water column turbidity which would be detectable by observations given the variability in measurements. The model has potential for application to map the large scale sensitivity of turbidity distributions to the installation of wave and tidal energy extraction arrays.

Storm surges are an abnormal enhancement of the water level in response to weather perturbations. They have the capacity to cause damaging flooding of coastal regions, especially when they coincide with astronomical high spring tides. Some areas of the UK have suffered particularly damaging surge events, and the Firth of Clyde is a region with high risk due to its location and morphology. Here, we use a three-dimensional high spatial resolution hydrodynamic model to simulate the local bathymetric and morphological enhancement of surge in the Clyde, and disaggregate the effects of far-field atmospheric pressure distribution and local scale wind forcing of surges. A climatological analysis, based on 30 years of data from Millport tide gauges, is also discussed. The results suggest that floods are not only caused by extreme surge events, but also by the coupling of spring high tides with moderate surges. Water level is also enhanced by a funnelling effect due to the bathymetry and the morphology of fjordic sealochs and the River Clyde Estuary. In a world of rising sea level, studying the propagation and the climatology of surges and high water events is fundamental. In addition, high-resolution hydrodynamic models are essential to forecast extreme events and to prevent the loss of lives, or to plan coastal defences solutions.

Densely populated coastal areas of the North Sea are particularly vulnerable to severe wave conditions, which overtop or damage sea-defences leading to dangerous flooding. Around the shallow southern North Sea, where the coastal margin is low-lying and population density is high, oceanographic modelling has helped to develop forecasting systems to predict flood risk. However coastal areas of the deeper northern North Sea are also subject to regular storm damage but there has been little or no effort to develop coastal wave models for these waters. Here we present a high spatial resolution model of northeast Scottish coastal waters, simulating waves and the effect of tidal currents on wave propagation, driven by global ocean tides, far-field wave conditions, and local air pressure and wind stress. We show that the wave–current interactions and wave–wave interactions are particularly important for simulating the wave conditions close to the coast at various locations. The model can simulate the extreme conditions experienced when high (spring) tides are combined with sea-level surges and large Atlantic swell. Such a combination of extremes represents a high risk for damaging conditions along the Scottish coast.

Management of the sea is increasingly complex, riddled with uncertainty and necessitates involvement from researchers across disciplines and stakeholders from multiple policy and practice sectors. This article discusses “The Cooperative Participatory Evaluation of Renewable Technologies on Ecosystem Services” (CORPORATES) research project, which developed an innovative and practical method of linking ecological processes, ecosystem services and benefits. The research was conducted in the context of licensing decisions for offshore wind farms in the North Sea (Scotland, UK). A set of linked, modular participatory processes were developed to foster cross-sector stakeholder engagement. It employed an exchange of ecological, legal, social, economic and cultural knowledge around marine ecosystem services. Workshop exercises included participatory mapping, benefit identification, and developing an understanding of linkages between ecosystem services, benefits, stakeholders’ activities and policy drivers through co-development of conceptual systems maps of the study area. The participatory exercises fostered meaningful dialogue across sectors and an ability to participate equally, despite initial differences in knowledge about ecosystem services. The development of conceptual systems maps facilitated productive discussion about trade-offs in relation to different policies. Reflective discussion identifies ways in which the developed processes could be integrated into future decision making. An assessment of the approach revealed that it operationalised a post normal science framework in terms of process oversight, multiple knowledge claims, and managing uncertainty. It developed a process that linked understanding of ecosystem functioning with the creation and implementation of policy thereby creating an ecosystem approach to marine spatial planning and licensing decisions, as required by law. This approach has extensive transferability to situations where stakeholder engagement is required to develop policy and provide feedback as part of a decision-making process. It is an engagement, outreach tool for communities and can help teach methods and processes for stakeholder engagement which enable new insights.

As oil reserves in established basins become depleted, exploration and production moves towards relatively unexploited areas, such as deep waters off the continental shelf. The Faroe-Shetland Channel (FSC, NE Atlantic) and adjacent areas have been subject to increased focus by the oil industry. In addition to extreme depths, metocean conditions in this region characterise an environment with high waves and strong winds, strong currents, complex circulation patterns, sharp density gradients, and large small- and mesoscale variability. These conditions pose operational challenges to oil spill response and question the suitability of current oil spill modelling frameworks (oil spill models and their forcing data) to adequately simulate the behaviour of a potential oil spill in the area. This article reviews the state of knowledge relevant to deepwater oil spill modelling for the FSC area and identifies knowledge gaps and research priorities. Our analysis should be relevant to other areas of complex oceanography.

High resolution measurements of the water velocity, bedforms and suspended sediment concentration were made using an Acoustic Doppler Velocimeter, acoustic bedform scanners and an Acoustic Backscatter System, under irregular free-surface waves. The waves were generated in a large scale flume facility above a number of bedform types. These data were analysed in (i) the frequency domain in order to examine the frequency at which sediment suspensions occurred in the oscillatory bottom boundary layer and the free stream; and (ii) the time domain in order to examine the instantaneous entrainment and vertical transport of sediment at intra-wave, wave average and wave group time scales. During the course of the experiments the significant wave height was systematically incremented enabling the character of sediment suspensions to be studied under a number of flow and bedform regimes. Wave groups were identified as an important control over sediment suspensions in both the wave boundary layer and free stream, with fluctuations in the suspended sediment concentration occurring at low, wave group, frequencies. However, the initial entrainment process, within the wave boundary layer, occurred at intra-wave frequencies. In contrast, in the free stream, sediment suspensions were dominated by the vertical transport of sediment at wave group time scales. During wave groups the sediment suspension field was characterised by the upward transport of sediment due to the continual injection of turbulence under a series of waves which generated a wave pumping effect. The character of a wave group is considered to be an important control over sediment suspensions in the free stream. Four distinct types of wave group were identified and the instantaneous sediment suspension field below each type examined. Such comparisons were possible using the high resolution Acoustic Backscatter System which enabled both intra-wave and wave group processes to be resolved up to 0.8 m above the bed.

The 7th UK Young Coastal Scientists and Engineers Conference welcomed 60 scientists and engineers to come together and discuss coastal research. The conference was hosted by the National Oceanography Centre in Liverpool, 30–31 March 2011. Early career practitioners and researchers presented 42 short papers on a range of topics driven by current issues addressed by UK universities, government agencies and consultancies. Although all presentations had a coastal theme, content varied from small-scale processes to regional-scale monitoring and management, covering topics such as structure impact, sediment transport, morphology, waves, currents, ecology, oxygen, estuarine systems, stratification, modelling, observation, ice, renewables and extreme events. This paper presents the keynote lecture and six abstracts considered to be of particular merit by the panel of judges. The conference continues to travel the UK and will be held at Bangor University in 2012.

On 25–26 March 2013, 52 early career scientists and engineers, studying various aspects of coastal science, met at the University of Aberdeen for the ninth Young Coastal Scientists and Engineers Conference. The conference was jointly organised by the School of Engineering, University of Aberdeen, and Marine Scotland Science. Early-career scientists, researchers and practitioners presented 23 oral and 17 poster presentations over the 2-day meeting. The papers all had a coastal theme with a large diversity in the subjects covered, including waves, currents, tidal energy, coastal erosion, sediment transport, fluid mechanics and particle tracking. This briefing paper reports on the conference, and presents the keynote lecture and four papers voted to be of especially high quality by the panel of judges.