Tide gauge data analysis of the pole tide in the North Sea

Abstract. The European Slope Current provides a shelf-edge conduit for Atlantic Water, a substantial fraction of which is destined for the northern North Sea, with implications for regional hydrography and ecosystems. Drifters drogued at 50 m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988–2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely recruited from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25–50 % reductions of these density gradients over 1996–1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10–40 % of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a general decline in this percentage over 1988–2007. Salinities in the Slope Current correspondingly decreased, evidenced in ocean analysis data. Further to the north, in the Atlantic Water conveyed by the Slope Current through the Faroe–Shetland Channel (FSC), salinity is observed to increase over this period while declining in the hindcast. The observed trend may have broadly compensated for a decline in the Atlantic inflow, limiting salinity changes in the northern North Sea during this period. Proxies for both Slope Current transport and Atlantic inflow to the North Sea are sought in sea level height differences across the FSC and between Shetland and the Scottish mainland (Wick). Variability of Slope Current transport on a wide range of timescales, from seasonal to multi-decadal, is implicit in sea level differences between Lerwick (Shetland) and Tórshavn (Faroes), in both tide gauge records from 1957 and a longer model hindcast spanning 1958–2012. Wick–Lerwick sea level differences in tide gauge records from 1965 indicate considerable decadal variability in the Fair Isle Current transport that dominates Atlantic inflow to the northwest North Sea, while sea level differences in the hindcast are dominated by strong seasonal variability. Uncertainties in the Wick tide gauge record limit confidence in this proxy.

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Storm Tilo over Europe in November 2007: storm surge and impacts on societal and energy infrastructure

Advances in Geosciences ◽

10.5194/adgeo-49-187-2019 ◽

2019 ◽

Vol 49 ◽

pp. 187-196 ◽

Cited By ~ 1

Author(s):

Anthony James Kettle

Keyword(s):

Water Level ◽

Storm Surge ◽

North Sea ◽

Tide Gauge ◽

Winter Storms ◽

Energy Infrastructure ◽

The North ◽

Short Period ◽

Pressure Centre ◽

The North Sea

Abstract. Storm Tilo on 8–9 November 2007 ranks among the serious winter storms in northern Europe over the past 30 years. Its low pressure centre passed across the northern North Sea, and this led to a cold air outbreak in northwest Europe. Strong north winds across the North Sea contributed to a high storm surge that was serious for coastal regions in eastern England, the Netherlands and Germany. Storm winds and unusually high waves caused shipping accidents and damage to some offshore energy infrastructure. This report presents an outline of the met-ocean conditions and a short overview of storm impacts on societal and energy infrastructure. The progress of the storm surge around the North Sea is analysed using data from the national tide gauge networks. A spectral analysis of the water level data is used to isolate the long period storm surge and short period oscillations (i.e., <4.8 h) from the tidal signal. The calculated skew surge is compared with literature reports for this storm and also with another serious North Sea storm from 31 October–1 November 2006 (Storm Britta). The short period oscillations are compared with the platform and shipping incident reports for the 2 d storm period. The results support previous reports of unusual wave and water level dynamics during some severe regional winter storms.

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North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry

Earth System Science Data ◽

10.5194/essd-13-3733-2021 ◽

2021 ◽

Vol 13 (8) ◽

pp. 3733-3753

Author(s):

Denise Dettmering ◽

Felix L. Müller ◽

Julius Oelsmann ◽

Marcello Passaro ◽

Christian Schwatke ◽

...

Keyword(s):

Sea Level ◽

North Sea ◽

Tide Gauge ◽

Sea Level Changes ◽

Adaptation Measures ◽

Isostatic Adjustment ◽

The North ◽

Sea Level Anomalies ◽

Vertical Land Motion ◽

The North Sea

Abstract. Information on sea level and its temporal and spatial variability is of great importance for various scientific, societal, and economic issues. This article reports about a new sea level dataset for the North Sea (named North SEAL) of monthly sea level anomalies (SLAs), absolute sea level trends, and amplitudes of the mean annual sea level cycle over the period 1995–2019. Uncertainties and quality flags are provided together with the data. The dataset has been created from multi-mission cross-calibrated altimetry data preprocessed with coastal dedicated approaches and gridded with an innovative least-squares procedure including an advanced outlier detection to a 6–8 km wide triangular mesh. The comparison of SLAs and tide gauge time series shows good consistency, with average correlations of 0.85 and maximum correlations of 0.93. The improvement with respect to existing global gridded altimetry solutions amounts to 8 %–10 %, and it is most pronounced in complicated coastal environments such as river mouths or regions sheltered by islands. The differences in trends at tide gauge locations depend on the vertical land motion model used to correct relative sea level trends. The best consistency with a median difference of 0.04±1.15 mm yr−1 is reached by applying a recent glacial isostatic adjustment (GIA) model. With the presented sea level dataset, for the first time, a regionally optimized product for the entire North Sea is made available. It will enable further investigations of ocean processes, sea level projections, and studies on coastal adaptation measures. The North SEAL data are available at https://doi.org/10.17882/79673 (Müller et al., 2021).

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NorthSEAL: A new Dataset of Sea Level Changes in the North Sea from Satellite Altimetry

10.5194/essd-2021-103 ◽

2021 ◽

Author(s):

Denise Dettmering ◽

Felix L. Müller ◽

Julius Oelsmann ◽

Marcello Passaro ◽

Christian Schwatke ◽

...

Keyword(s):

Sea Level ◽

North Sea ◽

Tide Gauge ◽

Sea Level Changes ◽

Adaptation Measures ◽

Isostatic Adjustment ◽

The North ◽

Sea Level Anomalies ◽

Vertical Land Motion ◽

The North Sea

Abstract. Information on sea level and its temporal and spatial variability is of great importance for various scientific, societal and economic issues. This article reports about a new sea level dataset for the North Sea (named NorthSEAL) of monthly sea level anomalies (SLA), absolute sea level trends and sea level mean annual amplitudes over the period 1995–2019. Uncertainties and quality flags are provided together with the data. The dataset has been created from multi-mission cross-calibrated altimetry data, preprocessed 5 with coastal dedicated approaches and gridded with innovative methods to a 6–8 km wide triangular mesh. The comparison of SLA and tide gauge time series shows a good consistency with average correlations of 0.85 and maximum correlations of 0.93. The improvement with respect to existing global gridded altimetry solutions amounts to 8–10 %, and it is most pronounced in complicated coastal environments such as river mouths or regions sheltered by islands. The differences in trends at tide gauge locations depend on the vertical land motion model used to correct relative sea level trends. The best 10 consistency with a median difference of 0.04 ± 1.15 mm/year is reached by applying a recent glacial isostatic adjustment (GIA) model. With the presented sea level dataset, for the first time, a regionally optimized product for the entire North Sea is made available. It will enable further investigations of ocean processes, sea level projections and studies on coastal adaptation measures. The NorthSEAL data is available at https://doi.org/10.17882/79673 (Müller et al., 2021).

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The impact of baroclinity on tidal ranges in the North Sea

10.5194/egusphere-egu2020-19147 ◽

2020 ◽

Author(s):

Wenguo Li ◽

Bernhard Mayer ◽

Thomas Pohlmann

Keyword(s):

Sea Level ◽

North Sea ◽

Tide Gauge ◽

Tidal Range ◽

Baroclinic Mode ◽

Kelvin Wave ◽

Ocean Stratification ◽

The North ◽

The North Sea ◽

The Impact

Tidal range is one of significant contributors of coastal inundation. Therefore, it is very important to investigate the dynamics of tidal range variations over different time scales. The baroclinity has the potential to modulate surface tides through ocean stratification on seasonal scale. In order to better understand the impact of ocean stratification on tidal ranges in the North Sea, the numerical simulations were carried out in baroclinic and barotropic modes covering the period from 1948 to 2014, using the regional 3D hydrodynamic prognostic Hamburg Shelf Ocean Model (HAMSOM). In the barotropic mode, the river forcing was also included, which only increases the local sea level without any influence on the density. The tidal range difference between baroclinic and barotropic modes in winter (less stratification) and summer (strong stratification) are compared at 22 tide-gauge stations, where the simulated sea surface elevations agree well with observations from 1950 to 2014. The statistical analysis generally shows that the difference at 19 stations (86% of total stations) in summer is much larger than that in winter during more than 32 years (50% of the analysis period). This suggests that the stratification decouples the surface and bottom layers weakening the damping effects of bottom friction, which is visible even at the coastal tide-gauge stations, where the ocean water is well-mixed. Obviously, the signal induced by stratification is propagated by the tidal Kelvin wave through the North Sea. Additionally, the spatial distribution of tidal range differences indicate that the amphidromic points in the North Sea moved westward in the baroclinic mode. Regarding the seasonal mean sea level at the stations, the results show that the coastal sea level could be increased by baroclinity itself, since the river runoff freshens the coastal water in the baroclinic mode, and thus the local sea level increases due to steric effect. Consequently, the increased sea level could further weaken the damping effect. However, this is a relatively minor impact on the tidal range.

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Storm Xaver over Europe in December 2013 and its energy meteorological impacts

10.5194/egusphere-egu2020-6029 ◽

2020 ◽

Author(s):

Anthony Kettle

Keyword(s):

Storm Surge ◽

North Sea ◽

Tide Gauge ◽

Offshore Wind ◽

Northern Europe ◽

Energy Infrastructure ◽

The North ◽

Short Period ◽

The North Sea ◽

The Uk

Storm Xaver impacted the northern Europe on 5-6 December 2013. &#160;It developed southeast of Greenland and passed north of Scotland and across southern Norway on a trajectory that led to a cold air outbreak across the North Sea and intense convection activity in northern Europe.&#160; Strong sustained north winds led to a high storm surge that impacted all countries bordering the North Sea. &#160;Storm Xaver was a century scale event with certain locations around the North Sea reporting their highest ever water levels since the start of modern records.&#160; Media reports from the time of the storm chronicle the scale of the disruptions, including many cancelled flights, interrupted rail networks, closed bridges and roads, coastal building collapses, and power blackouts across northern Europe. &#160;Much of this was due to the strong winds, but coastal storm surge flooding was important in the UK, and it led to interrupted port operations around the North Sea.The storm was important for energy infrastructure and particularly for wind energy infrastructure.&#160; In the northern North Sea, petroleum platforms were evacuated and operations closed ahead of the storm as a precautionary measure.&#160; A number of onshore wind turbines were badly damaged by high winds and lightning strikes in the UK and Germany.&#160; Over the North Sea, wind speeds exceeded the turbine shutdown threshold of 25 m/s for an extended period of time, with economic impacts from the loss of power generation.&#160;&#160; In the German Bight, the FINO1 offshore wind energy research platform was damaged at the 15 m level by large waves. &#160;This was the third report of storm damage to this platform after Storm Britta in 2006 and Storm Tilo in 2007. &#160;Researchers have highlighted the need to reassess&#160; the design criteria for offshore wind turbines based on these kinds of extreme meteorological events. &#160;For the offshore wind industry, an important element of energy meteorology is to characterize both the evolving wind and wave fields during severe storms as both elements contribute to turbine loads and potential damage.The present conference contribution presents a literature review of the major events during Storm Xaver and impacts on energy infrastructure.&#160; Tide gauge records are reanalyzed to trace the progress of the storm surge wave around the North Sea.&#160; A spectral analysis is used to separate the long period storm surge component, diurnal/semidiurnal tide, and short period components in the original water level record. &#160;The short period component of the tide gauge record is important as it may be linked with infragravity waves that have been implicated in certain cases of offshore infrastructure damage in addition to coastal erosion. &#160;Discussion is made of offshore wave records during the storm.&#160; Storm Xaver is compared with two damaging offshore storms in 2006 and 2007.

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Pole Tide in the North Sea-Baltic Area

Nature ◽

10.1038/246383b0 ◽

1973 ◽

Vol 246 (5433) ◽

pp. 383-383

Keyword(s):

North Sea ◽

Pole Tide ◽

The North ◽

The North Sea ◽

Baltic Area

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The nodal dependence of long-period ocean tides in the Drake Passage

10.5194/os-2018-50 ◽

2018 ◽

Author(s):

Philip L. Woodworth ◽

Angela Hibbert

Keyword(s):

Tide Gauge ◽

Drake Passage ◽

Ocean Tide ◽

Phase Lag ◽

Tide Gauge Data ◽

Long Period ◽

The North ◽

Ocean Tide Model ◽

Gauge Data ◽

Tidal Variability

Abstract. Almost three decades of bottom pressure recorder (BPR) measurements at the Drake Passage, and 31 years of hourly tide gauge data from Vernadsky station on the Antarctic Peninsula, have been used to investigate the temporal and spatial variations in this region of the three main long-period tides Mf, Mm and Mt (in order of decreasing amplitude, with periods of a fortnight, a month and third of a month respectively). The amplitudes of Mf and Mt, and the phase lags for all three constituents, vary over the nodal cycle (18.61 years) in essentially the same way as in the equilibrium tide, so confirming the validity of Doodson's nodal factors for these constituents. The amplitude of Mm is found to be essentially constant, and so inconsistent at the three-sigma level from the ±13 % (or ~ ±0.15 mbar) anticipated variation over the nodal cycle, which can probably be explained by energetic non-tidal variability in the records at monthly timescales and longer. The north-south differences in amplitude for all three constituents are consistent with those in a modern ocean tide model (FES2014), as are those in phase lag for Mf and Mt, while the difference for Mm is smaller than in the model. BPR measurements are shown to be superior to conventional tide gauge data in such tidal studies, thanks to the lower proportion of non-tidal variability in the records.

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

10.5194/egusphere-egu21-14706 ◽

2021 ◽

Author(s):

Leon Jänicke ◽

Andra Ebener ◽

Sönke Dangendorf ◽

Arne Arns ◽

Michael Schindelegger ◽

...

Keyword(s):

North Sea ◽

German Bight ◽

Large Scale ◽

Tide Gauge ◽

Tidal Range ◽

Tide Gauges ◽

Tide Gauge Records ◽

Large Spatial Scale ◽

The North ◽

The North Sea

Tide gauges throughout the North Sea basin show significant changes in the local tidal regime since the mid-20th century, especially in the German Bight area. These changes were analyzed within the DFG-funded project TIDEDYN (Analyzing long term changes in the tidal dynamics of the North Sea, project number 290112166) and the final results were recently published in J&#228;nicke et al. (2020, https://doi.org/10.1029/2020JC016456).In this paper, 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&#8217;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.We would like to present these research results and the content of the paper (cf. J&#228;nicke et al., 2020) at vEGU21, hoping to encourage subsequent questions and further discussions.

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