scholarly journals Increasing turbidity in the North Sea during the 20th century due to changing wave climate

Ocean Science ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 1615-1625 ◽  
Author(s):  
Robert J. Wilson ◽  
Michael R. Heath
Keyword(s):  
Shear Stress ◽  
20Th Century ◽  
North Sea ◽  
Water Clarity ◽  
Wave Climate ◽  
Current Data ◽  
Bed Shear Stress ◽  
Secchi Disc ◽  
The North ◽  
The North Sea

Abstract. Data on Secchi disc depth (the depth at which a standard white disc lowered into the water just becomes invisible to a surface observer) show that water clarity in the North Sea declined during the 20th century, with likely consequences for marine primary production. However, the causes of this trend remain unknown. Here we analyse the hypothesis that changes in the North Sea's wave climate were largely responsible by causing an increase in the concentrations of suspended particulate matter (SPM) in the water column through the resuspension of seabed sediments. First, we analysed the broad-scale statistical relationships between SPM and bed shear stress due to waves and tides. We used hindcasts of wave and current data to construct a space–time dataset of bed shear stress between 1997 and 2017 across the northwest European Continental Shelf and compared the results with satellite-derived SPM concentrations. Bed shear stress was found to drive most of the inter-annual variation in SPM in the hydrographically mixed waters of the central and southern North Sea. We then used a long-term wave reanalysis to construct a time series of bed shear stress from 1900 to 2010. This shows that bed shear stress increased significantly across much of the shelf during this period, with increases of over 20 % in the southeastern North Sea. An increase in bed shear stress of this magnitude would have resulted in a large reduction in water clarity. Wave-driven processes are rarely included in projections of climate change impacts on marine ecosystems, but our analysis indicates that this should be reconsidered for shelf sea regions.

scholarly journals Increasing turbidity in the North Sea during the 20<sup>th</sup> century due to changing wave climate

2019 ◽  
Author(s):  
Robert J. Wilson ◽  
Michael R. Heath
Keyword(s):  
Shear Stress ◽  
North Sea ◽  
Climate Change Impacts ◽  
Water Clarity ◽  
Wave Climate ◽  
Current Data ◽  
Bed Shear Stress ◽  
The North ◽  
White Disk ◽  
The North Sea

Abstract. Data on Secchi disk-depth (the depth at which a standard white disk lowered into the water just becomes invisible to a surface observer) show that water clarity in the North Sea declined during the 20th century, with likely consequences for marine primary production. However, the causes of this trend remain unknown. Here we analyze the hypothesis that changes in the North Sea's wave climate were largely responsible, by increasing the concentrations of suspended particulate matter (SPM) in the water column through re-suspension of seabed sediments. First, we analyzed the broad-scale statistical relationships between SPM and bed shear stress due to waves and tides. We used hindcasts of wave and current data to construct a space-time dataset of bed shear stress between 1997 and 2017 across the northwest European Continental Shelf, and compared the results with satellite-derived SPM concentrations. Bed shear stress was found to drive most of the inter-annual variation in SPM in the hydrographically mixed waters of the central and southern North Sea. We then used a long-term wave reanalysis to construct a time series of bed shear stress from 1900 to 2010. This shows that bed shear stress increased significantly across the shelf over this period, explaining more than half of the observed decline in water clarity over this period. Wave-driven processes are rarely included in projections of climate change impacts on marine ecosystems, but our analysis indicates that this should be reconsidered for shelf sea regions.

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.

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.

scholarly journals Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery

2007 ◽  
Vol 64 (8) ◽  
pp. 1543-1550 ◽  
Author(s):  
R. S. T. Ferro ◽  
E. G. Jones ◽  
R. J. Kynoch ◽  
R. J. Fryer ◽  
B-E. Buckett
Keyword(s):  
North Sea ◽  
Water Clarity ◽  
Light Level ◽  
Separation Performance ◽  
Separate Species ◽  
Trawl Fishery ◽  
The North ◽  
Acoustic Methods ◽  
Commercial Species ◽  
The North Sea

Abstract Ferro, R. S. T., Jones, E. G., Kynoch, R. J., Fryer, R. J., and Buckett, B-E. 2007. Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery. – ICES Journal of Marine Science, 64: 1543–1550. In the North Sea, Scottish vessels target haddock, cod, whiting, monkfish, saithe, and flatfish in a mixed whitefish trawl fishery. These species mature at different sizes and hence have a range of minimum landing sizes. Their different shapes and swimming capabilities imply different selection characteristics when escaping from trawl gear. However, they are often caught at the same time on the same grounds. Optimal exploitation can only be achieved by ensuring that the selection of each species varies appropriately with length during the fishing process. This paper describes one part of a large European project to develop species-selective trawl gear to improve the exploitation pattern of North Sea cod, while maintaining the catch of other important commercial species. A gear suitable to the Scottish mixed whitefish fishery was fitted with a horizontal panel in the tapered part of the net to separate species into an upper and lower compartment. Trials were conducted on research vessels to measure separation performance for nine species in different light conditions, at different towing speeds, and with different lengths of panel. Most haddock, whiting, and saithe pass above the panel, whereas most cod, flatfish, and monkfish pass below it. Towing speed and panel length had no significant effect on separation. At lower light levels during the night (April at latitude 58° to 61°N), fewer dab, sole, plaice, and cod pass below the panel. Observations and measurements of fish behaviour using acoustic methods are described. They suggest that the height at which fish enter the net mouth may be influenced by light level and water clarity.

Spectral wave climate of the North Sea

2007 ◽  
Vol 29 (3) ◽  
pp. 146-154 ◽  
Author(s):  
Alexander V. Boukhanovsky ◽  
Leonid J. Lopatoukhin ◽  
C. Guedes Soares
Keyword(s):  
North Sea ◽  
Wave Climate ◽  
The North ◽  
The North Sea

scholarly journals Das Verb „brauen“ im Helgoländischen: mit Beibehaltung der starken Flexion und reich entwickelter Semantik

Us Wurk ◽  
2020 ◽  
Vol 69 (3-4) ◽  
pp. 105-114
Author(s):  
N. Århammar
Keyword(s):  
20Th Century ◽  
North Sea ◽  
Dictionary Entry ◽  
Figurative Meaning ◽  
Beer Brewing ◽  
The North ◽  
Starting Point ◽  
The North Sea ◽  
The Senses ◽  
Germanic Languages

The verb „brew“ in the North Frisian dialect of the North Sea island of Heligoland is in two respects remarkable: first it has retained its original strong inflection (section 1) and secondly it developed a number of special meanings during the 19/20th century (section 2). I have tried to demonstrate how this great diversity came about: The starting point for thesemantic development was probably the analogy ʽbrew kettleʼ (for beer brewing) ~ ʽsteam boilerʼ (of steam-boats). In a small seafaring nation a shift of meaning from ʽbrew (beer)ʼ → ʽdrive (a ship)ʼ may seem rather natural; less so the further steps via *ʽmove in generalʼ → ʽwalk briskly, runʼ and so on (→ ʽlive, keep house, manage to get on well (as a single)ʼand ʽbe busy, workʼ etc.). Sense 8. of the dictionary entry, a figurative meaning, stands apart, namely ʽconcoct, contrive, prepare, bring about, causeʼ: spec. evil, mischief, trouble, woe (OED). It is noted that this sense was developed in most Germanic languages and it probably represents a much older sprout on the helig. brau-tree than do the senses 2. to 7. Insection 3, I deal with the helig. idiom Bin brau ʽto bring into disorderʼ and the helig.-wfris. parallel uun Bin ~ yn ʼe/ʼt bûn ʽin disorderʼ. – In the appendix the revised and enlarged word article brau with its prefix compounds is presented

Impact of Climate Change on the North Sea Offshore Energy Sector

2018 ◽  
Author(s):  
Nicolas Fournier ◽  
Galina Guentchev ◽  
Justin Krijnen ◽  
Andy Saulter ◽  
Caroline Acton ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
North Sea ◽  
Wave Climate ◽  
Energy Industry ◽  
Strong Impact ◽  
Impact Of Climate Change ◽  
The North ◽  
Climate Indicators ◽  
The North Sea

The complex nature of the energy industry across extraction, transportation, processing, delivery and decommissioning creates significant challenges to how the sector responds, adapts and mitigates against risks posed by the changing future climate. Any disruption in this interconnected system will affect both industry and society. For example, in the summer of 2005 Hurricane Katrina and a month later Hurricane Rita had wide reaching impacts on the US offshore Oil and Gas industry which resulted in an increase in global oil prices due to loss of production and refinery shutdowns in the Gulf of Mexico. Preparing, mitigating and adapting to these climate changes is dependent upon identifying appropriate climate indicators as well as the associated critical operational thresholds and design criteria of the identified vulnerable assets. The characterization and understanding of the likely changes in these climate indicators will form the basis for adaptation plans and mitigating actions. The Met Office in collaboration with energy industry partners, under the Copernicus Clim4energy European project, has developed a Climate Change Risk Assessment tool, which allows the visualization and extraction of the most recent sea level and wave climate information to evaluate their future changes. This study illustrates the application of this tool for evaluation of the potential vulnerability of an offshore infrastructure in the North Sea. The analysis shows that for this asset there is a small increase in sea level of 0.20–0.30 m at the location of interest by 2050. However, there is a small decrease or no consistent changes projected in the future wave climate. This wave signal is small compared to the uncertainty of the wave projections and the associated inter-annual variability. Therefore, for the 2050s time horizon, at the location of interest, there is no strong impact of climate change at the annual scale on the significant wave height, the sea level and thus the associated climate change driven extreme water level. However, further analysis are required at the seasonal and monthly scales.

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