Constraint of GIA in Northern Europe and the North Sea with Geological RSL and GPS Data

2021 ◽  
Author(s):  
Karen Simon ◽  
Riccardo Riva ◽  
Bert Vermeersen
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Tide Gauge ◽  
Data Driven ◽  
Northern Europe ◽  
Additional Measure ◽  
The North ◽  
Vertical Land Motion ◽  
The North Sea ◽  
Semi Empirical

<p>This study focusses on improved constraint of the millennial time-scale glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to present-day sea-level budgets. The study area extends from the coastal regions of northern Europe to Scandinavia. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. Specifically, 71 geological rates of GIA-driven RSL change are inferred from Holocene proxy data. Rates of vertical land motion from GNSS at 108 sites provide an additional measure of regional GIA deformation; within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa. Both datasets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models show discrepancies. The model validation in the North Sea region suggests that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, indicating that geological rates from Holocene data can provide an important additional constraint for data-driven approaches to GIA estimation. The geological proxy rates therefore provide a unique dataset with which to complement or validate existing data-driven approaches that use satellite era rates of change.</p>

Constraint of GIA in Northern Europe with Geological RSL and VLM Data

2020 ◽  
Author(s):  
Karen Simon ◽  
Riccardo Riva
Keyword(s):  
North Sea ◽  
Tide Gauge ◽  
Northern Europe ◽  
British Isles ◽  
Additional Measure ◽  
Isostatic Adjustment ◽  
The North ◽  
Vertical Land Motion ◽  
The North Sea ◽  
Semi Empirical

<p>In this study, we focus on better constraint of the long term glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to total present-day rates of change. The main study area extends from the coastal regions of northern Europe to Scandinavia. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. Specifically, 70 geological rates of GIA-driven RSL change are inferred from Holocene data; peak RSL fall is indicated in central Scandinavia and the northern British Isles where past ice sheets were thickest, RSL rise is indicated in the southern British Isles and along the northern European coastline. Rates of vertical land motion from GPS at 108 sites provide an additional measure of regional GIA deformation. Within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa; both datasets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models are discrepant. The model validation in the North Sea region indicates that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, suggesting that the geological rates provide an important additional constraint of present-day GIA.</p>

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

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).

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

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).

scholarly journals Large-scale forcing of the European Slope Current and associated inflows to the North Sea

Ocean Science ◽  
2017 ◽  
Vol 13 (2) ◽  
pp. 315-335 ◽  
Author(s):  
Robert Marsh ◽  
Ivan D. Haigh ◽  
Stuart A. Cunningham ◽  
Mark E. Inall ◽  
Marie Porter ◽  
...  
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Tide Gauge ◽  
Density Gradients ◽  
Current Transport ◽  
Tide Gauge Records ◽  
The North ◽  
Wide Range ◽  
The North Sea ◽  
Northern 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.

The impact of baroclinity on tidal ranges in the North Sea

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

<p>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.</p>

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

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

<p>Storm Xaver impacted the northern Europe on 5-6 December 2013.  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.  Strong sustained north winds led to a high storm surge that impacted all countries bordering the North Sea.  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.  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.  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.</p><p>The storm was important for energy infrastructure and particularly for wind energy infrastructure.  In the northern North Sea, petroleum platforms were evacuated and operations closed ahead of the storm as a precautionary measure.  A number of onshore wind turbines were badly damaged by high winds and lightning strikes in the UK and Germany.  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.   In the German Bight, the FINO1 offshore wind energy research platform was damaged at the 15 m level by large waves.  This was the third report of storm damage to this platform after Storm Britta in 2006 and Storm Tilo in 2007.  Researchers have highlighted the need to reassess  the design criteria for offshore wind turbines based on these kinds of extreme meteorological events.  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.</p><p>The present conference contribution presents a literature review of the major events during Storm Xaver and impacts on energy infrastructure.  Tide gauge records are reanalyzed to trace the progress of the storm surge wave around the North Sea.  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.  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.  Discussion is made of offshore wave records during the storm.  Storm Xaver is compared with two damaging offshore storms in 2006 and 2007.</p>

scholarly journals On analysing sea level rise in the German Bight since 1844

2010 ◽  
Vol 10 (2) ◽  
pp. 171-179 ◽  
Author(s):  
T. Wahl ◽  
J. Jensen ◽  
T. Frank
Keyword(s):  
Time Series ◽  
Sea Level Rise ◽  
Sea Level ◽  
North Sea ◽  
German Bight ◽  
Tide Gauge ◽  
South Eastern ◽  
The North ◽  
Positive Acceleration ◽  
The North Sea

Abstract. In this paper, a methodology to analyse observed sea level rise (SLR) in the German Bight, the shallow south-eastern part of the North Sea, is presented. The paper focuses on the description of the methods used to generate and analyse mean sea level (MSL) time series. Parametric fitting approaches as well as non-parametric data adaptive filters, such as Singular System Analysis (SSA) are applied. For padding non-stationary sea level time series, an advanced approach named Monte-Carlo autoregressive padding (MCAP) is introduced. This approach allows the specification of uncertainties of the behaviour of smoothed time series near the boundaries. As an example, the paper includes the results from analysing the sea level records of the Cuxhaven tide gauge and the Heligoland tide gauge, both located in the south-eastern North Sea. For comparison, the results from analysing a worldwide sea level reconstruction are also presented. The results for the North Sea point to a weak negative acceleration of SLR since 1844 with a strong positive acceleration at the end of the 19th century, to a period of almost no SLR around the 1970s with subsequent positive acceleration and to high recent rates.

What can idealized storm surge simulations tell us about worst case scenarios?

2021 ◽  
Author(s):  
Elin Andrée ◽  
Jian Su ◽  
Martin Drews ◽  
Morten Andreas Dahl Larsen ◽  
Asger Bendix Hansen ◽  
...  
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
North Sea ◽  
Wind Direction ◽  
Water Levels ◽  
Sea Levels ◽  
The North ◽  
The North Sea ◽  
Sea Coast ◽  
North Sea Coast

<p>The potential impacts of extreme sea level events are becoming more apparent to the public and policy makers alike. As the magnitude of these events are expected to increase due to climate change, and increased coastal urbanization results in ever increasing stakes in the coastal zones, the need for risk assessments is growing too.</p><p>The physical conditions that generate extreme sea levels are highly dependent on site specific conditions, such as bathymetry, tidal regime, wind fetch and the shape of the coastline. For a low-lying country like Denmark, which consists of a peninsula and islands that partition off the semi-enclosed Baltic Sea from the North Sea, a better understanding of how the local sea level responds to wind forcing is urgently called for.</p><p>We here present a map for Denmark that shows the most efficient wind directions for generating extreme sea levels, for a total of 70 locations distributed all over the country’s coastlines. The maps are produced by conducting simulations with a high resolution, 3D-ocean model, which is used for operational storm surge modelling at the Danish Meteorological Institute. We force the model with idealized wind fields that maintain a fixed wind speed and wind direction over the entire model domain. Simulations are conducted for one wind speed and one wind direction at a time, generating ensembles of a set of wind directions for a fixed wind speed, as well as a set of wind speeds for a fixed wind direction, respectively.</p><p>For each wind direction, we find that the maximum water level at a given location increases linearly with the wind speed, and the slope values show clear spatial patterns, for example distinguishing the Danish southern North Sea coast from the central or northern North Sea Coast. The slope values are highest along the southwestern North Sea coast, where the passage of North Atlantic low pressure systems over the shallow North Sea, as well as the large tidal range, result in a much larger range of variability than in the more sheltered Inner Danish Waters. However, in our simulations the large fetch of the Baltic Sea, in combination with the funneling effect of the Danish Straits, result in almost as high water levels as along the North Sea coast.</p><p>Although the wind forcing is completely synthetic with no spatial and temporal structure of a real storm, this idealized approach allows us to systematically investigate the sea level response at the boundaries of what is physically plausible. We evaluate the results from these simulations by comparison to peak water levels from a 58 year long, high resolution ocean hindcast, with promising agreement.</p>

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