Hypotheses concerning the circulation of the northern North Sea

Dooley, H. D.

doi:10.1093/icesjms/36.1.54

Cited by 81 publications

(31 citation statements)

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“…The SCC mostly continues along the south of Dogger Bank. The DC reduces in intensity as it enters the central North Sea (Dooley 1974). Otto et al (1990) identified ND as an area with little advection and variable, weak winddriven currents.…”

Section: Drivers Of Oxygen Depletion In the Central North Seamentioning

confidence: 99%

Spatial extent and historical context of North Sea oxygen depletion in August 2010

et al. 2012

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Prompted by recent observations of seasonal low dissolved oxygen from two moorings in the North Sea, a hydrographic survey in August 2010 mapped the spatial extent of summer oxygen depletion. Typical near-bed dissolved oxygen saturations in the stratified regions of the North Sea were 75-80 % while the well-mixed regions of the southern North Sea reached 90 %. Two regions of strong thermal stratification, the area between the Dooley and Central North Sea Currents and the area known as the Oyster Grounds, had oxygen saturations as low as 65 and 70 % (200 and 180 lmol dm -3 ) respectively. Low dissolved oxygen was apparent in regions characterised by low advection, high stratification, elevated organic matter production from the spring bloom and a deep chlorophyll maximum. Historical data over the last century from the International Council for the Exploration of the Sea oceanographic database highlight an increase in seasonal oxygen depletion and a warming over the past 20 years. The 2010 survey is consistent with, and reinforces, the signal of recent depleted oxygen at key locations seen in the (albeit sparse) historical data.

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Section: Drivers Of Oxygen Depletion In the Central North Seamentioning

confidence: 99%

Spatial extent and historical context of North Sea oxygen depletion in August 2010

et al. 2012

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“…In the last decade, the EU's Marine Strategy Framework Directive has placed on EU member states the responsibility of ensuring "good environmental status" (EU, 2008) for their territorial waters, so providing a regional regulatory driver to efforts to improve our understanding of the physical and ecological dynamics of the North Sea. The FIC has been described in broad terms as a southward-flowing current, approximately 30 nautical miles (56 km) wide (Svendsen et al, 1991), that flows through the Fair Isle Gap between the Orkney and Shetland islands (Dooley, 1974). In the North Sea, it is found close to the eastern coast of the Orkneys (Svendsen et al, 1991) in the approximate region of the 100 m isobath (Dooley, 1974;Winther and Johannessen, 2006).…”

Section: Introductionmentioning

confidence: 99%

Thermohaline forcing and interannual variability of northwestern inflows into the northern North Sea

Sheehan

Berx

Gallego

et al. 2017

Continental Shelf Research

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“…Salinity is a useful water mass tracer in the region and permits identification of the water masses present in the observations. The salinity minimum (< 35.25 g kg −1 ) to the west of the section is indicative of coastal water from around Scotland, which is freshened by river input and run-off (Dooley, 1974;Turrell et al, 1992); the salinity maximum (> 35.25 g kg −1 ) to the east of the section is indicative of water of recent Atlantic origin . Intermediate salinity (∼ 35.275 g kg −1 ) and minimum temperature (< 7.5 • C) is indicative of water that has spent the previous summer isolated beneath the seasonal thermocline (Svendsen et al, 1991;Turrell et al, 1992;Hill et al, 2008); this has been called Cooled Atlantic Water (CAW; Turrell et al, 1992).…”

Section: Comparison With Observationsmentioning

confidence: 99%

“…The region, which is influenced by cool (< 9 • C), saline (> 35.4 g kg −1 ) water found to the east of the front (Sheehan et al, 2017;Hill et al, 2008), is characterised by features excluded from the heating-stirring theory: coastal and oceanic water masses flow south into the North Sea, introducing temperature and salinity gradients that are not a consequence of heating-stirring interactions (Turrell, 1992;Hill et al, 2008;Sheehan et al, 2017), and a generally southward residual current persists throughout the year (Dooley, 1974;Turrell, 1992;Winther and Johannessen, 2006). Nevertheless, it is thought that the location of the front is at least partially influenced by the local heating-stirring balance, with tidal stirring being responsible for maintaining fully mixed conditions west of the front (Svendsen et al, 1991).…”

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confidence: 99%

Shelf sea tidal currents and mixing fronts determined from ocean glider observations

et al. 2018

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Abstract. Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tidedominated flows at high resolution. We use dive-average currents from a 2-month (12 October-2 December 2013) glider deployment along a zonal hydrographic section in the northwestern North Sea to accurately determine M 2 and S 2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day −1 . During the first part of the deployment (from mid-October until mid-November), results of a onedimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December), a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source regions. The glider observations capture the period when the front makes the transition from its summertime to wintertime state. Fronts in other shelf sea regions with oceanic influence may exhibit similar behaviour, with controlling processes and locations changing over an annual cycle. These results have implications for the thermohaline circulation of shelf seas.Copyright statement. The works published in this journal are distributed under the Creative Commons Attribution 4.0 License. This license does not affect the Crown copyright work, which is re-usable under the Open Government Licence (OGL). The Creative Commons Attribution 4.0 License and the OGL are interoperable and do not conflict with, reduce or limit each other.

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Hypotheses concerning the circulation of the northern North Sea

Abstract: The circulation of the northern North Seas has been a subject which has occup ied the attention of scientists since the end of the last century. Many

Cited by 81 publications

References 0 publications

Spatial extent and historical context of North Sea oxygen depletion in August 2010

Spatial extent and historical context of North Sea oxygen depletion in August 2010

Thermohaline forcing and interannual variability of northwestern inflows into the northern North Sea

Shelf sea tidal currents and mixing fronts determined from ocean glider observations

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