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Assessment of tidal range changes in the North Sea from 1958 to 2014

Assessment of tidal range changes in the North Sea from 1958 to 2014
Assessment of tidal range changes in the North Sea from 1958 to 2014
We document an exceptional large‐spatial scale case of changes in tidal range in the North Sea, featuring pronounced trends between ‐2.3 mm/yr at tide gauges in the UK and up to 7 mm/yr in the German Bight between 1958 and 2014. These changes are spatially heterogeneous and driven by a superposition of local and large‐scale processes within the basin. We use principal component analysis to separate large‐scale signals appearing coherently over multiple stations from rather localized changes. We identify two leading principal components (PCs) that explain about 69% of tidal range changes in the entire North Sea including the divergent trend pattern along UK and German coastlines that reflects movement of the region's semidiurnal amphidromic areas. By applying numerical and statistical analyses, we can assign a baroclinic (PC1) and a barotropic large‐scale signal (PC2), explaining a large part of the overall variance. A comparison between PC2 and tide gauge records along the European Atlantic coast, Iceland and Canada shows significant correlations on time scales of less than 2 years, which points to an external and basin‐wide forcing mechanism. By contrast, PC1 dominates in the southern North Sea and originates, at least in part, from stratification changes in nearby shallow waters. In particular, from an analysis of observed density profiles, we suggest that an increased strength and duration of the summer pycnocline has stabilized the water column against turbulent dissipation and allowed for higher tidal elevations at the coast.
2169-9275
Jänicke, Leon
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Ebener, Andra
1ae4296f-7234-4ee4-a8b2-05a8589059c6
Dangendorf, Sönke
ba1c5cbe-a385-41dc-8a46-da8cd36cf19d
Arns, Arne
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Schindelegger, Michael
676b35a8-5b3a-4b65-a82e-21919437d4b5
Niehüser, Sebastian
673e09dc-fb8d-4b58-a59d-edc48f7b8d01
Haigh, Ivan D.
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Woodworth, Philip
7c01a80b-64c8-458b-b9b2-ca76f0f508f3
Jensen, Jürgen
5188f969-c5e8-47e2-9e27-771067712095
Jänicke, Leon
5b716e50-7229-4a12-a1f9-4445b603d707
Ebener, Andra
1ae4296f-7234-4ee4-a8b2-05a8589059c6
Dangendorf, Sönke
ba1c5cbe-a385-41dc-8a46-da8cd36cf19d
Arns, Arne
2c3fd31d-325c-4e21-b02c-b530b9c26840
Schindelegger, Michael
676b35a8-5b3a-4b65-a82e-21919437d4b5
Niehüser, Sebastian
673e09dc-fb8d-4b58-a59d-edc48f7b8d01
Haigh, Ivan D.
945ff20a-589c-47b7-b06f-61804367eb2d
Woodworth, Philip
7c01a80b-64c8-458b-b9b2-ca76f0f508f3
Jensen, Jürgen
5188f969-c5e8-47e2-9e27-771067712095

Jänicke, Leon, Ebener, Andra, Dangendorf, Sönke, Arns, Arne, Schindelegger, Michael, Niehüser, Sebastian, Haigh, Ivan D., Woodworth, Philip and Jensen, Jürgen (2020) Assessment of tidal range changes in the North Sea from 1958 to 2014. Journal of Geophysical Research: Oceans, [e2020JC016456]. (doi:10.1029/2020JC016456).

Record type: Article

Abstract

We document an exceptional large‐spatial scale case of changes in tidal range in the North Sea, featuring pronounced trends between ‐2.3 mm/yr at tide gauges in the UK and up to 7 mm/yr in the German Bight between 1958 and 2014. These changes are spatially heterogeneous and driven by a superposition of local and large‐scale processes within the basin. We use principal component analysis to separate large‐scale signals appearing coherently over multiple stations from rather localized changes. We identify two leading principal components (PCs) that explain about 69% of tidal range changes in the entire North Sea including the divergent trend pattern along UK and German coastlines that reflects movement of the region's semidiurnal amphidromic areas. By applying numerical and statistical analyses, we can assign a baroclinic (PC1) and a barotropic large‐scale signal (PC2), explaining a large part of the overall variance. A comparison between PC2 and tide gauge records along the European Atlantic coast, Iceland and Canada shows significant correlations on time scales of less than 2 years, which points to an external and basin‐wide forcing mechanism. By contrast, PC1 dominates in the southern North Sea and originates, at least in part, from stratification changes in nearby shallow waters. In particular, from an analysis of observed density profiles, we suggest that an increased strength and duration of the summer pycnocline has stabilized the water column against turbulent dissipation and allowed for higher tidal elevations at the coast.

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2020JC016456 - Accepted Manuscript
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Assessment of Tidal Range Changes - Version of Record
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Accepted/In Press date: 13 December 2020
e-pub ahead of print date: 19 December 2020

Identifiers

Local EPrints ID: 446176
URI: http://eprints.soton.ac.uk/id/eprint/446176
ISSN: 2169-9275
PURE UUID: 5afa76fa-f89e-49ec-8de9-07f1e2c2b1eb

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Date deposited: 26 Jan 2021 17:31
Last modified: 25 Nov 2021 18:42

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Contributors

Author: Leon Jänicke
Author: Andra Ebener
Author: Sönke Dangendorf
Author: Arne Arns
Author: Michael Schindelegger
Author: Sebastian Niehüser
Author: Ivan D. Haigh
Author: Philip Woodworth
Author: Jürgen Jensen

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