Dogger Bank Research Articles

Spatial and temporal variability in larval connectivity of North Sea plaice Pleuronectes platessa between spawning grounds and coastal European nurseries

Annual year-class strength in North Sea plaice Pleuronectes platessa Linnaeus, 1758 appears to be determined by the connectivity of eggs and larvae between open-sea spawning grounds and coastal nursery areas. Hydrodynamic modelling studies indicate that coastal nurseries can be supplied with larvae from multiple offshore spawning locations. To verify this, we compared relative size-frequency distributions of demersal juvenile plaice just after larval immigration between coastal nurseries as a proxy for larval origin. During 12 yr, up to 21 stations in the Dutch coastal zone and international Wadden Sea were visited and sampled at the beginning of May at the end of larval immigration. The results of the size-frequency analysis showed 2 distinct clusters of stations. The first cluster included all stations along the Dutch coast and Wadden Sea up to Wangerooge in the German East Frisian Wadden Sea, most likely dominated by supply from spawning grounds in the Southern Bight, with contributions from the English Channel and the Dogger Bank. The second cluster included all stations in the North Frisian Wadden Sea, most likely supplied from spawning grounds in the German Bight and near the Dogger Bank. The higher interannual variability in the first cluster might be caused by a larger variability in the relative contributions from multiple spawning areas (English Channel, Southern Bight, Dogger Bank). The comparison of the relative size-frequency distributions at the end of larval immigration introduced in this study may also be a useful tool for the validation of connectivity modelling studies in other areas and for other species.

Oil Company Investment in Offshore Windfarms: A Business Case

European petroleum majors have moved into offshore windfarm projects, with large investments and ambitious capacity and production targets. In aggressive bidding for Contracts for Difference in the UK, where oil companies have played a key part, we have seen the inflation-adjusted strike price fall 65% from 2015 to 2019. Researchers question whether LCOE will fall to the same extent and would like to see more research on the economic return of the companies making offshore wind investment. We address this by a transparent project economics analysis of the UK bottom-fixed Dogger Bank project. It is the largest offshore windfarm project in the world under development and the UK is the country with highest off-shore wind capacity. The project is owned by Equinor, SSE Renewables and ENI. Our analysis shows that the project is expected to be unprofitable. Several of the input variables, however, are subject to considerable estimation uncertainty. We also present a low case and a high case scenario. Decomposition of the high case reveals factors that can contribute to a profitable wind power industry. We discuss financial issues facing oil company investment portfolios combining low return/ low risk renewables and high return/high risk petroleum. Offshore windfarms are organised as special purpose vehicle (SPV) companies. We analyse the economic interactions between the SPVs and the oil companies, and address accounting and financial issues.

Spatial separation of larval sprat (Sprattus sprattus) and sardine (Sardina pilchardus) related to hydrographical characteristics in the North Sea

AbstractClupeid fish species are widely distributed and of highly variable stock sizes. In the North Sea, the common clupeid species are herring (Clupea harengus) and sprat (Sprattus sprattus), but during recent decades, the generally more southerly distributed sardine (Sardina pilchardus) have been more frequently observed. Comparative studies of early life stages of small pelagic clupeids are scarce, and their abilities to co‐exist and relations to environmental characteristics are vastly understudied. We here investigated and compared distributional patterns of co‐occurring larval sprat and sardine in the North Sea, hypothesizing that they are separated into spatial niches linked to specific hydrographical characteristics. Sampling was carried out by a large ring‐net during standard fish surveys (IBTS Q3) in August 2018, 2019, and 2020. Sprat larvae were found widespread across the area of investigation, with the highest concentration in the central North Sea off the eastern and northern flanks of Dogger Bank, where abundances could reach 20 larvae/m2. Sardine larvae, on the other hand, showed their highest abundances in the Southern and German Bights. Distributions of the two species appeared complementary, and statistical correlations were indicative of separate hydrographical niches, where sardine larvae resided in relatively warmer and fresher water. The relative abundances of sardine versus sprat varied between years. Sardine larvae were especially abundant in 2020, twice as abundant as sprat, and observations indicate increasing importance of sardines in the North Sea.

Characterization and differentiation of sublittoral sandbanks in the southeastern North Sea

Marine sublittoral sandbanks are essential offshore feeding grounds for larger crustaceans, fish and seabirds. In the southern North Sea, sandbanks are characterized by considerable natural sediment dynamics and are subject to chronic bottom trawling. However, except for the Dogger Bank, sandbanks in the southeastern North Sea have been only poorly investigated until now. We used an extensive, multi-annual dataset covering ongoing national monitoring programmes, environmental impact assessments, and basic research studies to analyse benthic communities on sublittoral sandbanks, evaluating their ecological value against the backdrop of similar seafloor habitats in this region. The analysis revealed complex spatial structuring of sandy seafloor habitats of the southeastern North Sea. Different infauna clusters were identified and could be specified by their composition of characteristic species. The sandbanks shared common structural features in their infauna community composition although they were not necessarily characterized by particularly high biodiversity compared to other sandy habitats. A close association of one of the main bioturbators in the southern North Sea, the sea urchin Echinocardium cordatum, with sandbanks was detected, which may promote the sediment-bound biogeochemical activity in this particular seafloor habitat. This would corroborate the status of sandbanks as sites of high ecological value calling for consideration in marine conservation.

Stratigraphic and geotechnical characterization of regionally extensive and highly competent shallow sand units in the southern North Sea

A detailed stratigraphic and geotechnical investigation of the uppermost 50 m below the sea floor was carried out for parts of the German North Sea sector using combined information from shallow seismic reflection surveys, 50‐m‐long sediment cores and cone penetration tests covering an area of ~150 km2. While most recent studies concentrate on unusual features such as buried tunnel‐ or river‐valleys, this study focused on the less well understood, regionally dominant sand units deposited after the retreat of the last glaciers in this region. We identified two sandy units which dominate the late‐ to post‐Saalian geology: (i) the Upper Fluvial Member, believed to be derived from deposition of the Weser, Ems and Elbe palaeorivers as well as other tributaries of the Elbe Palaeovalley in the NE during the Saalian; and (ii) the Aeolian Member, which correlates with periglacial deposits of Weichselian age. Additionally, a Saalian Buried Valley Member believed to comprise fluvial deposit was also identified. Key stratigraphic units within the uppermost 50 m below the sea floor were also identified and mapped. Detailed geotechnical properties were obtained for each of the individual stratigraphic units. The regional extent of the Aeolian and Upper Fluvial Members was documented in the region west of the Elbe Palaeovalley and south of the Dogger Bank, where their geotechnical properties are important for foundation design. In conclusion, the study complements the established regional geotechno‐stratigraphy and offers new and detailed publically accessible information beneficial for offshore wind farm development within the region.

Biomarker insights into a methane-enriched Holocene peat-setting from “Doggerland” (central North Sea)

Peats formed widespread early after the Last Glacial Maximum around the coast of the Dogger Bank, the central high of the now flooded “Doggerland” (central North Sea). Here we present biomarker and gas geochemical insights into near-surface peat cored at 43 m water depth. Based on their probable age of ~10 ka before present (BP), the peats are likely part of the so-called basal Holocene peats. Pore waters in the samples document slight methane enrichments in peat layers (up to 250 nM methane vs 60 nM above the peat layer) and δ13C-values of methane ranging between ca. −46‰ and −60‰ PDB. Ethane, propane, and n-butane were also found and may either document upward migration of thermogenic hydrocarbons in the past or, more likely, peat-specific gases, which is indicated by accompanying abundant unsaturated analogs (i.e. ethene and propene). High concentrations of elemental sulfur (up to 19 wt.%) and sulfur-specific transformation products of plant triterpenoids (Des-A-triterpenoids) point to microbial generation during and/or slightly after peat-formation as hydrocarbon source. Biomarkers indicated that peats were formed in a variable environment with high contributions from higher plant wax material. However, a C20 highly branched isoprenoid (HBI) likely records abundant diatoms typical of an oligotrophic lake environment. In addition, all samples contained a suite of bacterial hopenes and fernenes (hop-17(21)-ene, diploptene, fern-7(8)-ene). A strongly fluctuating methane-flux and/or -turnover during peat formation is recorded in partially high 13C-depletions of <−60‰ PDB of these biomarkers. This underlines the importance of peat layers for methane generation and consumption on “Doggerland” during the Holocene.

Earth, wind and fire: island energy landscapes of the Anthropocene

Carbon-based systems of energy are rapidly unravelling. The imperative of climate emergency is reshaping energy landscapes, in some instances leading to the reappraisal of energy options hitherto sidelined. This paper deals with the emerging energy landscapes of the Netherlands and Iceland through historically informed tales that focus on islands. While vastly different in historical and geographical context and scale, these cases reveal the necessity of geographical nuance facilitated by the ways insular places offer insights into energy imaginaries of the Anthropocene. The former is a historicised narrative about the reinvention of wind energy as natural gas is being ousted. It focuses on the proposed Dogger Bank Power Link Islands, the first of which is scheduled to emerge in the coming years. The latter, also historically informed, identifies the context for current large wind energy proposals in Iceland, and then contrasts these with the authors’ empirical observations from the small peripheral island of Grímsey. There wind energy is also being reinvented for ousting the predominant oil infrastructure on the island. These cases represent experimental opportunities for envisioning Anthropocene futures intended to destabilize imaginaries of growth in ways that open spaces for negotiation and contestation. They problematize dominant narratives that render wind energy development visible and knowable as a necessary intervention. Emergent from this is wind’s decentred energy landscape in the Anthropocene; an epoch where energy is revealed in its importance to our societies, dispelling the human exceptionalism implicit in the nomenclature whilst at the same time showing how our actions come to matter. The collision of the Earth and ourselves under the terms of climate emergency begs the question whether our differences are the only ones that matter? But also, if it matters what we have done, then surely it matters what we have not done and chosen to ignore.

Effect of a new offshore gas platform on harbor porpoises in the Dogger Bank

AbstractOffshore Oil and Gas (O&G) exploration and production has been cycling from cradle to grave for over 100 years, spanning many generations of marine fauna. Despite global occurrence of offshore infrastructure, implications of their presence for apex predators, including cetaceans, is understudied. We analyzed data from autonomous underwater passive‐echolocation‐click detectors (C‐PODs) deployed at an offshore O&G production platform and at control locations to investigate acoustic activity of harbor porpoises (Phocoena phocoena) from 2015 to 2020, before, during, and after platform construction. Despite a statistically significant decrease in porpoise detections following platform construction and initial drilling operations (2015–2016), detections returned to baseline levels within five months. We detected no long‐term effects of platform presence on porpoise‐detection rates. While additional study is required to further understand activity of porpoise at O&G platforms during continued operation through to decommissioning, our findings, nonetheless, have important implications for Environmental Impact Assessments (EIAs), which do not currently consider effects of platform presence on marine mammals in any context other than short‐term noise mitigation. While we know porpoise forage at ageing platforms, this is the first study to demonstrate porpoise also utilize space around new platforms, which must be accommodated in long‐term EIA processes.

Seismic morphologies of submerged late glacial to Early Holocene landscapes at the eastern Dogger Bank, central North Sea Basin – implications for geo-archaeological potential

Abstract The inundated Doggerland in the North Sea Basin has been a coveted research target for many years owing to its key location with respect to geological evolution since the last glaciation and its archaeological potential related to prehistoric hunter–gatherer populations. Still, many uncertainties related to glacial and sea-level forcing on erosion and deposition remain, and the first discovery of submerged settlements is yet to be reported. In this study, we present a range of seismic morphologies and facies characteristic for the late glacial and Holocene succession near a major drainage system at the eastern Dogger Bank. Five of these facies are dominant in the area while two facies can be associated with a terrestrial–fluvial landscape buried 0–22 m below the seafloor. We detect various erosion levels of the terrestrial–fluvial landscape that are greatest towards the south where sediment has been removed, probably owing to combined terrestrial–fluvial and marine erosion. We find that five subareas show geo-archaeological potential in terms of (1) the preservation degree of terrestrial strata based on erosion estimates, (2) the accessibility of terrestrial strata based on burial depths and (3) the palaeolandscape configuration based on the spatial setting in relation to the drainage system and the palaeocoastlines. We further document a geological evolution of the study area, which is comparable with the evolution at the western Dogger Bank. However, we find more evidence for an extended flooding period because of the vicinity to the major drainage system and the Elbe Paleo Valley. We propose that our approach can be used as a workflow for marine investigations that focus on submerged hunter–gatherer heritage.

A Novel Approach to Using Seabed Geomorphology as a Predictor of Habitat Use in Highly Mobile Marine Predators: Implications for Ecology and Conservation

Understanding how marine predators find patchily distributed prey resources in a dynamic environment is key to identifying important ecological areas for ecosystem-level conservation management. However, the mechanisms underpinning important foraging areas often result from complex interactions between static and dynamic covariates (e.g. topography and currents). Modelling habitat associations with hydrodynamic processes is rarely useful when attempting to identify and characterise foraging areas across an individual’s foraging range. Investigating the influence of static habitat features on predator behaviour can provide a more tractable baseline understanding of habitat associations, upon which additional complexity can be added. Seabed gradient covariates (e.g. slope and aspect) are often used, yet such metrics are computed at singular user-defined resolutions, and provide limited ecological insight when used in isolation. Instead, categorising the seabed into geomorphological features may provide better characterisation of seabed structure. Here we explore the utility of a pattern recognition algorithm to delineate whole geomorphological features (“geomorphons”) on the seabed (e.g. valleys, ridges, footslopes) from bathymetry data, and examine the influence of geomorphology on marine predator habitat use. We demonstrate the potential application of this approach in a case study, examining the influence of geomorphons on the at-sea behaviour of a highly mobile predator inhabiting shelf seas: the grey seal (Halichoerus grypus). We analyse GPS tracking data from three seals tagged in the southern North Sea, an area with heterogeneous geomorphology. We use hidden Markov models (HMMs) to infer foraging and travelling behaviour and model the effect of different feature types on the probability of switching between states. All three seals showed an increased probability of transitioning from travelling to foraging when encountering slopes, footslopes and hollows, and foraging activity was concentrated at slopes on the fringes of the Dogger Bank. We hypothesise that such features may host prey aggregations, and/or lead to increased prey capture success. The results suggest the importance of such areas for grey seals in the southern North Sea, a region undergoing rapid and widespread anthropogenic habitat change. This method could be incorporated into future species distribution models to improve estimates of predator distribution, informing conservation management and marine spatial planning.

A large-scale study of microplastic abundance in sediment cores from the UK continental shelf and slope

To inform risk assessments, reliable, time efficient and affordable quantification methods are required for creating a microplastic (MP) pollution baseline in the world's oceans. To facilitate this, MP abundance was investigated in sediments of three contrasting areas of the UK continental shelf: North West of Jones Bank, the Canyons in the Celtic Sea and Dogger Bank in the North Sea, utilising the Nile Red tagging method to assess its time efficiency and cost. Average MP abundance in the top 10 cm was 1050–2700 MP kg−1. MP abundance decreased with increasing sediment depth and increased with increasing water depth. The findings emphasise the extent of MP pollution and illustrate the value of Nile Red for large scale mapping at relatively low cost.

The Elbe Palaeovalley: Evolution from an ice-marginal valley to a sedimentary trap (SE North Sea)

The southeastern North Sea was a sub-aerially exposed periglacial environment during the late Weichselian. At that time, the approximately 210 km long and 40 km wide SE–NW trending Elbe Palaeovalley (EPV) was the main conduit for meltwater from the southern margin of the Scandinavian ice sheet and rivers draining the North European plain. Only few studies investigated the environmental organization of the Northwest European shelves during deglacial sea level rise resulting in vague reconstructions of the drainage systems. Here, a detailed analysis of sediment echo-sounder data and core samples are presented to study the EPV morphology and stratigraphic infill. The valley base is about 65 m below the present sea-level. This SE-NW palaeo-drainage with its braided system developed during the MIS 2 sea level fall and lowstand in a periglacial environment. During deglacial sea-level rise, the EPV evolved into an estuary with tributaries, intertidal and subtidal flats. After the early Holocene (∼10 cal ka BP), ongoing sea-level rise drowned the EPV system which became the major sedimentary trap in the southern North Sea. Successive sea level rise and associated changes in the hydrodynamic regime led to three stages of shelf organization that were recorded in the valley infill successions: (1) shallow basin with restricted connections to Atlantic water; (2) the southwestern connection with the Dover Strait; (3) the open marine environment at 5.8 cal ka BP after the drowning of Dogger Bank.

Seismic Hazard Assessment for a Wind Farm Offshore England

Offshore wind has become a major contributor to reducing global carbon emissions. This paper presents a probabilistic seismic hazard analysis for the Sofia Offshore Wind Farm, which is located about 200 km north-east of England in the southern North Sea and will be one of the largest offshore wind farms in the world once completed. The seismic source characterization is composed of two areal seismic source models and four seismic source models derived using smoothed gridded seismicity with earthquake catalogue data processed by different techniques. The ground motion characterization contains eight ground motion models selected based on comparisons with regional data. The main findings are (1) the variation in seismic hazard across the site is negligible; (2) the main source controlling the hazard is the source that includes the 1931 Dogger Bank earthquake; (3) earthquake scenarios controlling the hazard are Mw = 5.0–6.3 and R = 110–210 km; and (4) the peak ground accelerations on rock are lower than for previous regional studies. These results could help guide future seismic hazard assessments in the North Sea.

Glacitectonic evidence of ice sheet interaction and retreat across the western part of Dogger Bank (North Sea) during the Last Glaciation

High-resolution 2D seismic data from the western side of Dogger Bank (North Sea) has revealed that the glacigenic sediments of the Dogger Bank Formation record a complex history of sedimentation and penecontemporaneous, large-scale, ice-marginal to proglacial glacitectonism. The resulting complex assemblage of glacial landforms and sediments record the interplay between two separate ice masses revealing that Late Devensian ice sheet dynamics across Dogger Bank were far more complex than previously thought, involving the North Sea lobe of the British and Irish Ice Sheet, advancing from the west, interacting with the Dogger Bank lobe which expanded from the north. The active northward retreat of the Dogger Bank lobe resulted in the development of a complex assemblage of arcuate thrust-block moraines (≤15 km wide, >30 km long) composed of highly folded and thrust sediments, separated by sedimentary basins and meltwater channels filled by outwash. The impact of the North Sea lobe was restricted to the western margin of Dogger Bank and led to deep-seated (100–150 m thick) glacitectonism in response to ice-push from the west. During the earlier expansion of the North Sea lobe, this thrust and fold complex initially occupied a frontal marginal position changing to a more lateral ice-marginal position as the ice sheet continued to expand to the south. The complex structural relationships between the two glacitectonic complexes indicates that these ice masses interacted along the western side of Dogger Bank, with the inundation of this area by ice probably occurring during the last glaciation when the ice sheets attained their maximum extents.

Large-scale assessment of masking potential by underwater ship noise the North Sea

The JOMOPANS project created one year of soundscape maps of the North Sea, based on ship information from the Automatic Identification System (AIS) and a ship source model. This assessed the potential impact of ship noise on the marine ecosystem through the masking of communication and other relevant acoustic signals. Specifically, the excess noise was quantified, which express the deterioration of the signal-to-noise ratio caused by the ship noise and hence the reduction in maximum communication range. The dominance of ship noise over natural sources was quantified as the percentage of time where excess was 20 dB or higher. A decrease in signal-to-noise ratio of 20 dB compared to a reference condition (ambient plus weather) without ships indicates a substantial decrease in communication range, and hence a substantial risk of impact on the ecosystem. Maps of excess and dominance in different frequency bands showed the largest ship contribution in the lowest frequency bands and in the most trafficked areas, with less affected areas in shallow waters, including the Dogger Bank. These maps, in combination with distribution maps of sensitive species, form the basis for the joint assessment of environmental status of the North Sea by the surrounding countries.

Direct and fast probabilistic assessment of long term monopile load distribution from combined metocean data and fully nonlinear wave kinematics

A novel method is introduced to determine the long-term extreme value distribution of variables with an associated short-term distribution. The method is applicable to e.g. the extreme value with a return period of 10.000 years for wave height, crest height of waves as well as wave-induced response and loads on offshore wind turbine monopiles. The extreme values are determined by a combination of a joint probabilistic description of the met-ocean environment and of a recently developed database of fully nonlinear wave kinematics computations. For two benchmark monopile structures, representative for the conditions at Dogger Bank and the German Bight in the North Sea, the one-hour max value of crest height, inline force and overturning moment are computed via the Rainey slender-body force model. Convolution with the joint probability of the sea state parameters in the nondimensional space of wave steepness and Ursell parameter leads to the marginal probability distribution for these parameters up to a 10.000 year return period and properly accounts for the uncertainty of the extreme value parameters in also the short-term distributions. It is found that the best extreme value fit is generally obtained with a third-order polynomial fit within the space of steepness and Ursell parameter. Compared to the Forristall crest height distribution, the inclusion of full nonlinearity leads to larger crest heights at low return period levels. However, due to its realistic treatment of the breaking limitation, lower crests are predicted at the 10.000 year level for the two positions considered in the North Sea. With further verification of the wave kinematics in combination with load models and a thorough comparison to present engineering practice, the proposed methodology provides a robust future solution for directly estimating extreme value distributions of loads and response of offshore wind turbine monopiles.

Interconnection and generation from a North Sea power hub – A linear electricity model

We research effects on the electricity market of countries surrounding the North Sea after a proposed offshore wind park in the Dogger Bank area of the North Sea has been constructed. Interconnection and generation distribution are analysed separately. The supply price of electricity for each country is calculated by a linear regression analysis to simulate the supply price for higher or lower supply. The model uses the coupling of one supply with one receiver country. Linear modelling of the electricity market combines the results for each objective to find a final state for the market. Using the historic market and weather data for 2016, the results from interconnection show an average generated value of 0.275 [M€/hour] and 82.1 [GW] of average energy flow through the hub. The results of this interconnection between the countries bring between −26% and +11% change on average electricity prices. For hub generation added in, we found an average generated value of 0.573 [M€/hour] and an average price drop of 5% for each country for an average wind power generation of 6.3 [GW] at the hub. The results show that interconnecting the similarly sized electricity markets i.e. Great Britain and Germany & the Netherlands and Denmark, where one has a higher renewable share, would bring the most price stabilization between the two as well as generate the most financial return.

Earthquakes and dams: Remote and direct monitoring of UK earthquakes affecting dam infrastructure

Although earthquake hazard in the UK is low, there is a long history of earthquakes that have been widely felt or in some cases caused damage. Although these events are relatively rare, earthquake hazard assessment is still required for structures, such as dams, where the consequence of failure may be very high. Since 1990 the UK has experienced more than 13 earthquakes of greater than magnitude 4. The largest recorded onshore earthquake was a 5.4 local magnitude (ML) (Lleyn Peninsula, 1984) and the largest offshore was the 6.1 ML (Dogger bank, 1931). Smaller earthquakes can also produce levels of ground motion more typically associated with larger earthquakes; for instance, if they are unusually shallow or otherwise close to a structure of interest. In this talk two different, but potentially complimentary, methods of monitoring reservoir infrastructure for the affects of earthquakes are considered: remote monitoring of a region with a rapid alert system combined with the use of ground motion prediction equations to assess the likely ground motions at facilities of interest and direct emplacement of seismic sensors in or around reservoir structures to provide absolute values of ground motion during an earthquake.

NEW PLANT FOR BIG BLADES

GE Renewable Energy is building a new manufacturing facility in Teesside that will supply giant blades for Dogger Bank wind turbines.

Retreat dynamics of the eastern sector of the British–Irish Ice Sheet during the last glaciation

ABSTRACTThe findings of BRITICE‐CHRONO Transect 2 through the North Sea Basin and eastern England are reported. We define ice‐sheet marginal oscillation between ~31 and 16 ka, with seven distinctive former ice‐sheet limits (L1–7) constrained by Bayesian statistical analysis. The southernmost limit of the North Sea Lobe is recorded by the Bolders Bank Formation (L1; 25.8–24.6 ka). L2 represents ice‐sheet oscillation and early retreat to the northern edge of the Dogger Bank (23.5–22.2 ka), with the Garret Hill Moraine in north Norfolk recording a significant regional readvance to L3 at 21.5–20.8 ka. Ice‐marginal oscillations at ~26–21 ka resulted in L1, L2 and L3 being partially to totally overprinted. Ice‐dammed lakes related to L1–3, including Lake Humber, are dated at 24.1–22.3 ka. Ice‐sheet oscillation and retreat from L4 to L5 occurred between 19.7 and 17.3 ka, with grounding zone wedges marking an important transition from terrestrial to marine tidewater conditions, triggered by the opening of the Dogger Lake spillway between 19.9 and 17.5 ka. L6 relates to ice retreat under glacimarine conditions and final ice retreat into the Firth of Forth by 15.8 ka. L7 (~15 ka) represents an ice retreat from Bosies Bank into the Moray Firth.