scholarly journals The role of heat wave events on the occurrence and persistence of thermal stratification in the southern North Sea

2022 ◽  
Author(s):  
Wei Chen ◽  
Joanna Staneva ◽  
Sebastian Grayek ◽  
Johannes Schulz-Stellenfleth ◽  
Jens Greinert
Keyword(s):  
Potential Energy ◽  
Water Column ◽  
Heat Wave ◽  
North Sea ◽  
Thermal Stratification ◽  
Early Stage ◽  
Southern North Sea ◽  
The North ◽  
The North Sea

Abstract. Extremes in temperatures not only directly affect the marine environment and ecosystems but also have indirect impacts on hydrodynamics and marine life. The role of heat wave events responsible for the occurrence and persistence of thermal stratification was analysed using a fully coupled hydrodynamic and wave model within the framework of the Geesthacht Coupled cOAstal model SysTem (GCOAST) for the North Sea. The model results were assessed against satellite reprocessed data and in situ observations from field campaigns and fixed MARNET stations. To quantify the degree of stratification, a potential energy anomaly over the water column was calculated. A linear correlation existed between the air temperatures and the potential energy anomaly in the North Sea excluding the Norwegian Trench and the area south of 54° N latitude. Contrary to the northern part of the North Sea, where the water column is stratified in the warming season each year, the southern North Sea is seasonally stratified in years when a heatwave occurs. The influences of heatwaves on the occurrence of summer stratifications in the southern North Sea are mainly in the form of two aspects, i.e., a rapid rise in sea surface temperature at the early stage of the heatwave period and a relatively higher water temperature during summer than the multiyear mean. Another factor that enhances the thermal stratification in summer is the memory of the water column to cold spells earlier in the year. Differences between the seasonally stratified northern North Sea and the heatwave-induced stratified southern North Sea were attributed to changes in water depth.

Distributions and fluxes of contaminant metals in the North Sea: comparisons between field measurements and model simulations using NOSTRADAMUS

2008 ◽  
Vol 5 (1) ◽  
pp. 51 ◽  
Author(s):  
A. D. Tappin ◽  
P. J. Statham ◽  
J. D. Burton ◽  
S. Gellers-Barkmann
Keyword(s):  
Water Column ◽  
North Sea ◽  
Formal Model ◽  
Transport Model ◽  
Field Measurements ◽  
Particle Settling ◽  
Southern North Sea ◽  
The North ◽  
The North Sea ◽  
Contaminant Metals

Environmental context. The North Sea, which is of significant ecological, economic and recreational value to NW Europe, has for many years received enhanced inputs of contaminant metals arising from human activity around its shores. Fluxes of copper, nickel, zinc, chromium and other constituents throughout the southern North Sea were estimated using a numerical model in order to identify the main sources and sinks for these metals. Comparison of model output with independent and other data showed good agreement in general. The results indicate that models of the kind developed here can be used to provide useful information on contaminant metal transport in coastal waters. Abstract. The steady-state 2-D vertically integrated numerical transport model NOSTRADAMUS has been used to simulate concentrations, distributions and fluxes of dissolved and particulate Cu, Cr, Ni and Zn in the southern North Sea between 51 and 56°N. The model results for the metals, and also for salinity and suspended sediments, were compared with field measurements from the Natural Environment Research Council (NERC) North Sea Project (NSP). The model generated realistic concentrations of all constituents, and in many cases reproduced the major features of the distributions, i.e. higher concentrations in the coastal zones and lower values in the central region. The sensitivity of the model results to variations in forcing data was extensively tested. In most cases, the default data provided the best results (quantified by residual sums of squares scores) despite no formal model calibration having been undertaken. Simulated fluxes indicated that metal inputs across the open sea boundaries were significant (Cu, 51%; Cr, 36%; Ni, 57%; Zn, 32%), although for Cu, Ni and Zn, river inputs were also important (13–15%). Metal transfers associated with particle settling and resuspension were significant (23–55%), and resuspended sediments were a minor net source, relative to particle settling, of Cu, Ni and Zn to the water column over the simulated year. In contrast, the resuspension of sediment from the seabed appeared to be a major source of Cr to the water column, a feature not explained at present. The major export from the North Sea in the model was through the northern boundary adjacent to the coast of Denmark. The fraction lost was in the range 61%, for Zn, to 90%, for Cr. Model results were compared with available independent data. The comparisons showed that the simulated constituent transfers approximated reasonably well with contemporary understanding of metal, and other constituent, fluxes in this region. These outcomes serve to emphasise the underlying capabilities of the model, and it can be concluded that NOSTRADAMUS provides the basis for heuristic studies of contaminant metals in the southern North Sea.

scholarly journals The Size of Diatoms II. Further Observations on Rhizosolenia styliformis (Brightwell)

1946 ◽  
Vol 26 (3) ◽  
pp. 271-284 ◽  
Author(s):  
R. S. Wimpenny
Keyword(s):  
North Sea ◽  
Indicator Species ◽  
Separate Species ◽  
Southern North Sea ◽  
Auxospore Formation ◽  
The North ◽  
The North Sea ◽  
Set Up ◽  
The Antarctic

1. Diameter measurements of Rhizosolenia styliformis from the Antarctic, the subtropical Atlantic and Pacific Oceans and from the North Sea and neighbouring waters have made it appear necessary to set up two varieties, oceanica and semispina, in addition to the type of the species R. styliformis. The type as I describe it has been called var. longispina by Hustedt, but elsewhere it has often been figured as the var. oceanica of this paper. Var. semispina is synonymous with the form represented by Karsten as R. semispina Hensen. It differs from R. semispina as drawn by Hensen and its synonym R. hebetata forma semispina Gran, but is thought likely to be linked by intermediates. If this is so R. hebetata may have to be extended to include and suppress R. styliformis, as var. semispina is linked to the type by intermediates. Var. oceanica has no intermediate forms and, if R. hebetata is to be extended, this variety should be established as a separate species.2. Var. oceanica is absent from the southern North Sea and appears to be an indicator species related to oceanic inflow.3. Auxospore formation was observed for the type in the southern North Sea in 1935 and biometric observations suggest that a period of 3-4 years elapsed between the production of auxospore generations in that area. Outside the southern North Sea for the type, measurements give no indication of auxospore generations occurring at intervals exceeding a year. While auxospore formation has been seen in var. oceanica from the Shetlands area samples of June 1935 and July 1938, this phenomenon has not been observed for var. semispina.

scholarly journals The impact of sedimentary alkalinity release on the water column CO<sub>2</sub> system in the North Sea

2016 ◽  
Vol 13 (3) ◽  
pp. 841-863 ◽  
Author(s):  
H. Brenner ◽  
U. Braeckman ◽  
M. Le Guitton ◽  
F. J. R. Meysman
Keyword(s):  
Coastal Zone ◽  
North Sea ◽  
Dissolved Inorganic Carbon ◽  
Co2 Uptake ◽  
Overlying Water ◽  
Southern North Sea ◽  
The North ◽  
Alkalinity Generation ◽  
The North Sea ◽  
The Impact

Abstract. It has been previously proposed that alkalinity release from sediments can play an important role in the carbonate dynamics on continental shelves, lowering the pCO2 of seawater and hence increasing the CO2 uptake from the atmosphere. To test this hypothesis, sedimentary alkalinity generation was quantified within cohesive and permeable sediments across the North Sea during two cruises in September 2011 (basin-wide) and June 2012 (Dutch coastal zone). Benthic fluxes of oxygen (O2), alkalinity (AT) and dissolved inorganic carbon (DIC) were determined using shipboard closed sediment incubations. Our results show that sediments can form an important source of alkalinity for the overlying water, particularly in the shallow southern North Sea, where high AT and DIC fluxes were recorded in near-shore sediments of the Belgian, Dutch and German coastal zone. In contrast, fluxes of AT and DIC are substantially lower in the deeper, seasonally stratified, northern part of the North Sea. Based on the data collected, we performed a model analysis to constrain the main pathways of alkalinity generation in the sediment, and to quantify how sedimentary alkalinity drives atmospheric CO2 uptake in the southern North Sea. Overall, our results show that sedimentary alkalinity generation should be regarded as a key component in the CO2 dynamics of shallow coastal systems.

scholarly journals Linked sediment and water-column methanotrophy at a man-made gas blowout in the North Sea: Implications for methane budgeting in seasonally stratified shallow seas

2016 ◽  
Vol 61 (S1) ◽  
pp. S367-S386 ◽  
Author(s):  
Lea Steinle ◽  
Mark Schmidt ◽  
Lee Bryant ◽  
Matthias Haeckel ◽  
Peter Linke ◽  
...  
Keyword(s):  
Water Column ◽  
North Sea ◽  
The North ◽  
The North Sea ◽  
Shallow Seas

Marine Growth on North Sea Fixed Steel Platforms: Insights From the Decommissioning Industry

2014 ◽  
Author(s):  
Chadi Mallat ◽  
Alistair Corbett ◽  
Glyn Harris ◽  
Marc Lefranc
Keyword(s):  
North Sea ◽  
Gas Industry ◽  
Southern North Sea ◽  
The North ◽  
The North Sea ◽  
Insight Into

It is reputed in the Oil & Gas industry that marine growth is overestimated in the North Sea. Can we quantify this overestimation to better tackle the challenges marine growth incurs? This paper provides insight into the intrinsic and diverse nature of marine growth. It documents the biofouling development and the factors that affect it globally. Focus is made on fixed steel platforms in the North Sea approaching the end of their economic lives. A methodology to quantify the weight of marine growth is proposed and illustrated. 28 years after its installation, the weight of marine growth accumulated on Valhall 2/4G jacket located in Southern North Sea is evaluated based on the proposed method. It is confirmed that the current regulations overestimate the weight of marine growth in the North Sea.

Metabolic alkalinity release from the Elbe estuary to the North Sea

2021 ◽  
Author(s):  
Mona Norbisrath ◽  
Jeannette Hansen ◽  
Kirstin Dähnke ◽  
Tina Sanders ◽  
Justus E. E. van Beusekom ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Water Column ◽  
Fresh Water ◽  
North Sea ◽  
Total Alkalinity ◽  
Elbe Estuary ◽  
Metabolic Processes ◽  
The North ◽  
Carbon Species ◽  
The North Sea

&lt;p&gt;The Elbe is the largest river entering the German Bight. Its estuary is a heavily used waterway connecting the sea to Germany&amp;#8217;s biggest port in Hamburg. The Elbe navigation channel is continuously dredged, and agricultural fertilizer input from the catchment ensuing large phytoplankton blooms in the river Elbe exerts additional anthropogenic pressure. Biogeochemistry in the estuary is additionally governed by the North Sea and its strong tidal cycles, which ensure an exchange of fresh and marine waters.&lt;/p&gt;&lt;p&gt;The aims were to quantify the release of the carbon species total alkalinity (TA) and dissolved inorganic carbon (DIC) along the Elbe estuary, and to estimate the contribution of aerobe and anaerobe metabolic processes. Therefore, we used water samples collected continuously during a cruise in June 2019, to measure TA and DIC, and the stable isotopes of nitrate. We applied mass balances, to characterize the metabolic activity and detect their effect on the carbon species&lt;/p&gt;&lt;p&gt;The Elbe estuary could be subdivided into two parts: 1) an outer marine driven part, which is dominated by conservative mixing, also visible in higher TA than DIC values, and 2) an inner fresh water part in which metabolic processes play an important role.&lt;/p&gt;&lt;p&gt;We found a strong increase in TA and DIC (several hundred &amp;#181;mol kg&lt;sup&gt;-1&lt;/sup&gt;) in the Hamburg port area, with higher DIC than TA values. We unraveled the water column impacts of nitrification and denitrification on TA and DIC by analyzing the stable isotopes &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N-NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O-NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, and identified water column nitrification as a dominant pelagic process in the port of Hamburg and in the fresh water part further downstream. Because nitrification cannot explain the significant increase of TA and DIC in the port region, anaerobic processes such as denitrification in the sediment also appear to play an important role.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Investigations Upon the Water Movements in the English Channel. Summer, 1924

1927 ◽  
Vol 14 (3) ◽  
pp. 685-721 ◽  
Author(s):  
J. N. Carruthers
Keyword(s):  
North Sea ◽  
English Channel ◽  
Average Speed ◽  
Southern North Sea ◽  
The North ◽  
Westerly Winds ◽  
The North Sea

In July, 1924, 250 floating, and an equal number of bottom-trailing, bottles were put out at selected places in the western English Channel. Fifty of each type were put out at each of the two routine Stations E2 and E3, and the same number was “liberated” at each of three selected stretches along the steamship route from Southampton to St. Malo. Those surface bottles, which did not strand locally, travelled rapidly up Channel towards the North Sea and across it. Many bottles arrived in the Skager-Rack after performing their journey of some 700 miles at the rate of 6 miles a day and more. An adequate study of wind conditions, as recorded at several stations along the length of the Channel and at one station in the southern North Sea, revealed the fact that there was, for some 5½ months (counting from the time of liberation of the bottles), an almost uninterrupted predominance of south-westerly winds—as recorded at all stations considered. The whole area of the Channel was swept by south-westerly winds of average speed of some 9 miles a day for at least 5½ months subsequent to the time of putting out of the bottles. July, 1924, had (according to the Falmouth Observatory records) the largest proportion of westerly winds experienced for 54 years; 20 days of this month had winds with westerly components. The association of the unusually persistent westerly winds with the rapid travel of surface bottles towards and across the North Sea is interesting.

scholarly journals Warm-water decapods and the trophic amplification of climate in the North Sea

2010 ◽  
Vol 6 (6) ◽  
pp. 773-776 ◽  
Author(s):  
J. A. Lindley ◽  
G. Beaugrand ◽  
C. Luczak ◽  
J.-M. Dewarumez ◽  
R. R. Kirby
Keyword(s):  
North Sea ◽  
Warm Water ◽  
Climate Signal ◽  
Southern North Sea ◽  
The North ◽  
Ecosystem Shift ◽  
The North Sea ◽  
Induced Changes ◽  
Water Species

A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime.

Sign in / Sign up

Export Citation Format

Share Document