Dynamics of tidal mixing fronts in the North Sea

1993 ◽  
Vol 343 (1669) ◽  
pp. 431-446 ◽  
Keyword(s):  
North Sea ◽  
Baroclinic Instability ◽  
Acoustic Doppler Current Profiler ◽  
Hf Radar ◽  
Tidal Mixing ◽  
The North ◽  
Current Profiler ◽  
Shelf Sea ◽  
The North Sea ◽  
New Generation

Twenty years since the discovery of tidal mixing fronts there are still few convincing observations of the velocity field associated with these structures. Simple models of shelf sea fronts predict strong along-front jets, weaker convergent circulations and instabilities. During the North Sea Project a series of studies of the Flamborough frontal system has used a new approach based upon novel combinations of modern instrumentation (HF radar, acoustic Doppler current profiler, Decca-Argos drifting buoys and towed undulating CTD) and have provided one of the first directly observed pictures of shelf sea frontal circulation. Observational confirmation of jetlike along-front flow has been found together with evidence of cross-frontal convergence. A new generation of eddy-resolving models will help to focus the next phase of frontal circulation studies in relation to questions concerning baroclinic instability and eddy generation.

scholarly journals Analysis of tidal currents in the North Sea from shipboard acoustic Doppler current profiler data

2018 ◽  
Vol 162 ◽  
pp. 1-12 ◽  
Author(s):  
Håvard Vindenes ◽  
Kjell Arild Orvik ◽  
Henrik Søiland ◽  
Henning Wehde
Keyword(s):  
North Sea ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
The North ◽  
Current Profiler ◽  
The North Sea ◽  
Profiler Data

scholarly journals Metabarcoding reveals different zooplankton communities in northern and southern areas of the North Sea

2020 ◽  
Author(s):  
Jan Niklas Macher ◽  
Berry B. van der Hoorn ◽  
Katja T. C. A. Peijnenburg ◽  
Lodewijk van Walraven ◽  
Willem Renema
Keyword(s):  
North Sea ◽  
Zooplankton Community ◽  
Taxonomic Diversity ◽  
Molecular Techniques ◽  
Trophic Levels ◽  
List Type ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Zooplankton Communities

AbstractZooplankton are key players in marine ecosystems, linking primary production to higher trophic levels. The high abundance and high taxonomic diversity renders zooplankton ideal for biodiversity monitoring. However, taxonomic identification of the zooplankton assemblage is challenging due to its high diversity, subtle morphological differences and the presence of many meroplanktonic species, especially in coastal seas. Molecular techniques such as metabarcoding can help with rapid processing and identification of taxa in complex samples, and are therefore promising tools for identifying zooplankton communities. In this study, we applied metabarcoding of the mitochondrial cytochrome c oxidase I gene to zooplankton samples collected along a latitudinal transect in the North Sea, a shelf sea of the Atlantic Ocean. Northern regions of the North Sea are influenced by inflow of oceanic Atlantic waters, whereas the southern parts are characterised by more coastal waters. Our metabarcoding results indicated strong differences in zooplankton community composition between northern and southern areas of the North Sea, particularly in the classes Copepoda, Actinopterygii (ray-finned fishes) and Polychaeta. We compared these results to the known distributions of species reported in previous studies, and by comparing the abundance of copepods to data obtained from the Continuous Plankton Recorder (CPR). We found that our metabarcoding results are mostly congruent with the reported distribution and abundance patterns of zooplankton species in the North Sea. Our results highlight the power of metabarcoding to rapidly assess complex zooplankton samples, and we suggest that the technique could be used in future monitoring campaigns and biodiversity assessments.HighlightsZooplankton communities are different in northern and southern areas of the North SeaMetabarcoding results are consistent with known species distributions and abundanceMetabarcoding allows for fast identification of meroplanktonic species

scholarly journals Depth-averaged instantaneous currents in a tidally dominated shelf sea from glider observations

2016 ◽  
Author(s):  
Lucas Merckelbach
Keyword(s):  
Real Time ◽  
North Sea ◽  
Current Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Real Time Mode ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Better Than

Abstract. Ocean gliders have become ubiquitous observation platforms in the ocean in recent years. They are also increasingly used in coastal environments. The coastal observatory system COSYNA has pioneered the use of gliders in the North Sea, a shallow tidally energetic shelf sea. For operational reasons, the gliders operated in the North Sea are programmed to resurface every 3–5 hours. The glider's deadreckoning algorithm yields depth averaged currents, averaged in time over each subsurface interval. Under operational conditions these averaged currents are a poor approximation of the instantaneous tidal current. In this work an algorithm is developed that estimates the instantaneous current (tidal and residual) from glider observations only. The algorithm uses a second-order Butterworth low-pass filter to estimate the residual current component, and a Kalman filter based on the linear shallow water equations for the tidal component. A comparison of data from a glider experiment with current data from an ADCP deployed nearby shows that the standard deviations for the east and north current components are better than 7 cm s−1 in near-real time mode, and improve to better than 5 cm s−1 in delayed mode, where the filters can be run forward and backward. In the near-real time mode the algorithm provides estimates of the currents that the glider is expected to encounter during its next few dives. Combined with a behavioural and dynamic model of the glider, this yields predicted trajectories, the information of which is incorporated in warning messages issued to ships by the (German) authorities. In delayed mode the algorithm produces useful estimates of the depth averaged currents, which can be used in (process-based) analyses in case no other source of measured current information is available.

Dynamics of tidal mixing fronts in the North Sea

1994 ◽  
pp. 53-68 ◽  
Author(s):  
A. E. Hill ◽  
I. D. James ◽  
P. F. Linden ◽  
J. P. Matthews ◽  
D. Prandle ◽  
...  
Keyword(s):  
North Sea ◽  
Tidal Mixing ◽  
The North ◽  
The North Sea

scholarly journals Depth-averaged instantaneous currents in a tidally dominated shelf sea from glider observations

2016 ◽  
Vol 13 (24) ◽  
pp. 6637-6649 ◽  
Author(s):  
Lucas Merckelbach
Keyword(s):  
Real Time ◽  
North Sea ◽  
Current Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Real Time Mode ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Better Than

Abstract. Ocean gliders have become ubiquitous observation platforms in the ocean in recent years. They are also increasingly used in coastal environments. The coastal observatory system COSYNA has pioneered the use of gliders in the North Sea, a shallow tidally energetic shelf sea. For operational reasons, the gliders operated in the North Sea are programmed to resurface every 3–5 h. The glider's dead-reckoning algorithm yields depth-averaged currents, averaged in time over each subsurface interval. Under operational conditions these averaged currents are a poor approximation of the instantaneous tidal current. In this work an algorithm is developed that estimates the instantaneous current (tidal and residual) from glider observations only. The algorithm uses a first-order Butterworth low pass filter to estimate the residual current component, and a Kalman filter based on the linear shallow water equations for the tidal component. A comparison of data from a glider experiment with current data from an acoustic Doppler current profilers deployed nearby shows that the standard deviations for the east and north current components are better than 7 cm s−1 in near-real-time mode and improve to better than 6 cm s−1 in delayed mode, where the filters can be run forward and backward. In the near-real-time mode the algorithm provides estimates of the currents that the glider is expected to encounter during its next few dives. Combined with a behavioural and dynamic model of the glider, this yields predicted trajectories, the information of which is incorporated in warning messages issued to ships by the (German) authorities. In delayed mode the algorithm produces useful estimates of the depth-averaged currents, which can be used in (process-based) analyses in case no other source of measured current information is available.

The contribution of the deep chlorophyll maximum to primary production in a seasonally stratified shelf sea, the North Sea

2013 ◽  
Vol 113 (1-3) ◽  
pp. 153-166 ◽  
Author(s):  
Liam Fernand ◽  
Keith Weston ◽  
Tom Morris ◽  
Naomi Greenwood ◽  
Juan Brown ◽  
...  
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Deep Chlorophyll Maximum ◽  
Chlorophyll Maximum ◽  
The North ◽  
Shelf Sea ◽  
The North Sea

Regional Impacts of Offshore Windfarming on the Hydro- and Ecosystem Dynamics in the North Sea

2020 ◽  
Author(s):  
Nils Christiansen ◽  
Ute Daewel ◽  
Corinna Schrum ◽  
Jeff Carpenter ◽  
Bughsin Djath ◽  
...  
Keyword(s):  
North Sea ◽  
Wind Farm ◽  
Ecosystem Dynamics ◽  
Ocean Dynamics ◽  
Offshore Wind ◽  
Tidal Mixing ◽  
Surface Boundary ◽  
The North ◽  
Wake Effects ◽  
The North Sea

<p>The production of renewable offshore wind energy in the North Sea increases rapidly, including development in ecologically significant regions. Recent studies identified implications like large-scale wind wake effects and mixing of the water column induced by wind turbines foundations. Depending on atmospheric stability, wind wakes imply changes in momentum flux and increased turbulence up to 70 km downstream, affecting the local conditions (e.g. wind speed, cloud development) near offshore wind farms. Atmospheric wake effects likely translate to the sea-surface boundary layer and hence influence vertical transport in the surface mixing layer. Changes in ocean stratification raise concerns about substantial consequences for local hydrodynamic and biogeochemical processes as well as for the marine ecosystem.<br>Using newly developed wind wake parametrisations together with the unstructured-grid model SCHISM and the biogeochemistry model ECOSMO, this study addresses windfarming impacts in the North Sea for future offshore wind farm scenarios. We focus on wind wake implications on ocean dynamics as well as on changes in tidal mixing fronts near the Dogger Bank and potential ecological consequences. At this, we create important knowledge on how the cross-scale wind farm impacts can be modelled suitably on the system scale.</p>

Recent FerryBox observations reveal a strong increase in surface seawater pCO2 in the North Sea

2021 ◽  
Author(s):  
Vlad Macovei ◽  
Yoana Voynova ◽  
Holger Brix ◽  
Wilhelm Petersen
Keyword(s):  
North Sea ◽  
Carbon Dioxide Partial Pressure ◽  
Strong Increase ◽  
Surface Seawater ◽  
Annual Cycles ◽  
The North ◽  
Regime Types ◽  
Shelf Sea ◽  
The North Sea ◽  
Spatio Temporal

<p>Surface seawater carbon dioxide partial pressure (pCO<sub>2</sub>) in the North Sea, a large temperate shelf sea, was measured between 2014 and 2018 using FerryBox-integrated membrane sensors on ships of opportunity. The use of commercial vessels ensured a high spatio-temporal resolution, with data available year-round in areas belonging to all the stratification regime types found in the North Sea. Average annual cycles revealed a dominant biological control on pCO<sub>2</sub> variability, with thermal effects modulating its amplitude. In the regions of freshwater influence, the biogeochemical characteristics of the riverine end-member also influenced the pCO<sub>2</sub> measured near shore. Deseasonalized winter trends of seawater pCO<sub>2</sub> were positive (ranging from 4.4 ± 2.0 µatm yr<sup>-1</sup> to 8.4 ± 2.9 µatm yr<sup>-1</sup> depending on the region), while the trends calculated including all deseasonalized monthly averages were even higher (ranging from 9.7 ± 2.8 µatm yr<sup>-1</sup> to 12.2 ± 1.4 µatm yr<sup>-1</sup>). All these trends were stronger than the atmospheric pCO<sub>2</sub> trend. Consequently, during our study period, the southern North Sea became a stronger source and the northern North Sea became a weaker sink for atmospheric carbon with implications for the Northwestern European Shelf carbon uptake capacity.</p>

Sign in / Sign up

Export Citation Format

Share Document