Document Type
Article
Publication Date
2021
DOI
10.1029/2020jc016456
Publication Title
Journal of Geophysical Research: Oceans
Volume
126
Issue
1
Pages
1-18
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 United Kingdom 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 United Kingdom 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.
Rights
© 2020 The Authors.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Data Availability
Article states: "Data from GESLA (Global Extreme Sea Level Analysis, GESLA Version 2P. Woodworth et al. 2017), Open Earth (Deltares, http://opendap.deltares.nl/thredds/catalog/opendap/rijkswaterstaat/waterbase/27_Waterhoogte_in_cm_t.o.v._normaal_amsterdams_peil_in_oppervlaktewater/nc/catalog.html), and the responsible German authorities (Wasser- und Schifffahrtsverwaltung des Bundes via the portals of the associated Central Data Management, ZDM, https://www.portalnsk.de) were used."
Original Publication Citation
Jänicke, L., Ebener, A., Dangendorf, S., Arns, A., Schindelegger, M., Niehüser, S., Haigh, I. D., Woodworth, P., & Jensen, J. (2021). Assessment of tidal range changes in the north sea from 1958 to 2014. Journal of Geophysical Research: Oceans, 126(1), 1-18, Article e2020JC016456. https://doi.org/10.1029/2020jc016456
Repository Citation
Jänicke, Leon; Ebener, Andra; Dangendorf, Sönke; Arns, Arne; Schindelegger, Michael; Niehüser, Sebastian; Haigh, Ivan D.; Woodworth, Philip; and Jensen, Jürgen, "Assessment of Tidal Range Changes in the North Sea from 1958 to 2014" (2021). CCPO Publications. 356.
https://digitalcommons.odu.edu/ccpo_pubs/356
ORCID
0000-0002-3679-5234 (Dagendorf)