Baltic Sea datums and their unification as a basis for coastal and seabed studies

AbstractThis paper presents examples of application of a common reference datum, such as NAP, within the elevation EVRS reference system for the Baltic Sea. A common reference datum allowed for setting the geographical pattern of occurrence of extreme sea levels in the Baltic Sea. The eastern Baltic coasts exposed to western air masses are vulnerable to extreme hydrological events (the Gulf of Finland, the Gulf of Riga and the Gulf of Bothnia). On the contrary, the Swedish coasts of the central and northern Baltic are the least threatened by extreme sea levels. The south-western coasts of the Baltic Sea (the Bay of Mecklenburg and the Bay of Kiel) cover the basins with the most frequent and the most severe storm falls and extremely low sea levels. Demonstration of the Baltic surface deformation magnitude during a storm event is another example of NAP application. The instantaneous height difference between the north-eastern and southwestern coasts was 356 cm, which resulted from the negative impact of pressure (water cushion) induced by a dynamic and deep low-pressure system moving through the Baltic Sea. The common reference datum allowed for visualization of the so-called “theoretical water” distribution which has a wide application in the hydraulic engineering within the coastal zone. In addition, the study provides examples of differences that may be observed during storm events between the real sea-level data and the hydrodynamic model forecast. This is of great practical significance in terms of forecasting storm surges in the Baltic Sea.

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Geographical diversity in the occurrence of extreme sea levels on the coasts of the Baltic Sea

Journal of Sea Research ◽

10.1016/j.seares.2020.101890 ◽

2020 ◽

Vol 159 ◽

pp. 101890

Author(s):

Tomasz Wolski ◽

Bernard Wiśniewski

Keyword(s):

Baltic Sea ◽

The Baltic Sea ◽

Sea Levels ◽

Extreme Sea Levels ◽

The Baltic

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Statistical Downscaling of daily extreme Sea Level with Random Forest: Examples from South-East Asia and the Baltic Sea

10.5194/egusphere-egu2020-10082 ◽

2020 ◽

Author(s):

Svenja Bierstedt ◽

Eduardo Zorita ◽

Birgit Hünicke

Keyword(s):

Random Forest ◽

Baltic Sea ◽

East Asia ◽

Sea Level ◽

Large Scale ◽

South East Asia ◽

The Baltic Sea ◽

Sea Levels ◽

Extreme Sea Levels ◽

The Baltic

The coastlines of the Baltic Sea and Indonesia are both relatively complex, so that the estimation of extreme sea levels caused by the atmospheric forcing becomes complex with conventional methods. Here, we explore whether Machine Learning methods can provide a model surrogate to compute more rapidly daily extremes in sea level from large-scale atmosphere-ocean fields. We investigate the connections between the atmospheric and ocean drivers of local extreme sea level in South East Asia and along the Baltic Sea based on statistical analysis by Random Forest Models, driven by large-scale meteorological predictors and daily extreme sea level measured by tide-gauge records over the last few decades.First results show that in some Indonesian areas extremes are driven by large-scale climate fields; in other areas they are incoherently driven by local processes. An area where random forest predicted extremes show good correspondence to observed extremes is found to be the Malaysian coastline. For the Indonesian coasts, the Random Forest Algorithm was unable to predict extreme sea levels in line with observations. Along the Baltic Sea, in contrast, the Random Forest model is able to produce reasonable estimations of extreme sea levels based on the large-scale atmospheric fields. An analysis of the interrelations of extreme sea levels in the South Asia regions suggests that either the data quality may be compromised in some regions or that other forcing factors, distinct from the large-scale atmospheric fields, may also be involved.

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Simulating extreme sea levels at the Baltic Sea coast from synthetic cyclones

10.5194/egusphere-egu2020-10271 ◽

2020 ◽

Author(s):

Jani Särkkä ◽

Jani Räihä ◽

Matti Kämäräinen ◽

Kirsti Jylhä

Keyword(s):

Baltic Sea ◽

Sea Level ◽

Water Volume ◽

The Baltic Sea ◽

Data Set ◽

Sea Levels ◽

Extreme Sea Levels ◽

Level Model ◽

The Baltic ◽

Sea Coast

Coastal areas are under rapid changes. Management to face flooding hazards in changing climate is of great significance due to the major impact of flooding events in densely populated coastal regions, where also important and vulnerable infrastructure is located. The sea level of the Baltic Sea is affected by internal fluctuations caused by wind, air pressure and seiche oscillations, and by variations of the water volume due to the water exchange between the Baltic Sea and the North Sea through the Danish Straits. The highest sea level extremes are caused by cyclones moving over the region. The most vulnerable locations are at the ends of the bays. St. Petersburg, located at the eastern end of the Gulf of Finland, has experienced major sea floods in 1777, 1824 and 1924.In order to study the effects of the depths and tracks of cyclones on the extreme sea levels, we have developed a method to generate cyclones for numerical sea level studies. A cyclone is modelled as a two-dimensional Gaussian function with adjustable horizontal size and depth. The cyclone moves through the Baltic Sea region with given direction and velocity. The output of this method is the gridded data set of mean sea level pressure and wind components which are used as an input for the sea level model. The internal variations of the Baltic Sea are calculated with a numerical barotropic sea level model, and the water volume variations are evaluated using a statistical sea level model based on wind speeds near the Danish Straits. The sea level model simulations allow us to study extremely rare but physically plausible sea level events that have not occurred during the observation period at the Baltic Sea coast. The simulation results are used to investigate extreme sea levels that could occur at selected sites at the Finnish coastline.

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Extreme Sea Levels in the Baltic Sea under Climate Change Scenarios. Part 1: Model Validation and Sensitivity

10.5194/os-2019-65 ◽

2019 ◽

Cited By ~ 1

Author(s):

Christian Dieterich ◽

Matthias Gröger ◽

Lars Arneborg ◽

Helén C. Andersson

Keyword(s):

Climate Change ◽

Baltic Sea ◽

Regional Climate ◽

Climate Change Scenarios ◽

Confidence Limits ◽

The Baltic Sea ◽

Sea Levels ◽

Return Levels ◽

Extreme Sea Levels ◽

The Baltic

Abstract. An ensemble of regional climate change scenarios for the Baltic Sea is validated and analyzed with respect to extreme sea levels (ESLs) in the recent past. The ERA40 reanalysis and five Coupled Model Intercomparison Project Phase 5 (CMIP5) global general circulation models (GCMs) have been downscaled with the coupled atmosphere-ice-ocean model RCA4-NEMO. Validation of 100-year return levels against observational estimates along the Swedish coast shows that the model estimates are within the 95 % confidence limits for most stations, except those on the west coast. The ensemble mean 100-year return levels turns out to be the best estimator with biases of less than 10 cm. The ensemble spread includes the 100-year return levels based on observations. A series of sensitivity studies explores how the choice of different parameterizations, open boundary conditions and atmospheric forcing affects the estimates of 100-year return levels. A small ensemble of different regional climate models (RCMs) forced with ERA40 shows the highest uncertainty in ESLs in the southwestern Baltic Sea and in the northeastern part of the Bothnian Bay. Also the Skagerrak, Gulf of Finland and Gulf of Riga are sensitive to the choice of the RCM. A second ensemble of one RCM forced with different GCMs uncovers a lower sensitivity of ESLs against the variance introduced by different GCMs. The uncertainty in the estimates of 100-year return levels introduced by GCMs ranges from 20 cm to 40 cm at different stations. It is of similar size as the 95 % confidence limits of 100-year return levels from observational records.

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MORPHOLOGIC RESPONSE OF SMALL BARRIER ISLANDS TO EXTREME SEA LEVELS ALONG THE BALTIC SEA

The Proceedings of the Coastal Sediments 2015 ◽

10.1142/9789814689977_0009 ◽

2015 ◽

Author(s):

AART KROON ◽

MIKKEL FRUERGAARD ◽

TROELS AAGAARD ◽

ALINA KABUTH

Keyword(s):

Baltic Sea ◽

Barrier Islands ◽

The Baltic Sea ◽

Sea Levels ◽

Extreme Sea Levels ◽

Morphologic Response ◽

The Baltic

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Changes in extreme sea-levels in the Baltic Sea

Tellus A Dynamic Meteorology and Oceanography ◽

10.3402/tellusa.v66.20921 ◽

2014 ◽

Vol 66 (1) ◽

pp. 20921 ◽

Cited By ~ 4

Author(s):

Andreia Ribeiro ◽

Susana M. Barbosa ◽

Manuel G. Scotto ◽

Reik V. Donner

Keyword(s):

Baltic Sea ◽

The Baltic Sea ◽

Sea Levels ◽

Extreme Sea Levels ◽

The Baltic

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The Probability of Occurrence of Extreme Sea Levels on Coasts of the Baltic Sea

Journal of Coastal Research ◽

10.2112/si95-259.1 ◽

2020 ◽

Vol 95 (sp1) ◽

pp. 1349

Author(s):

Tomasz Wolski ◽

Bernard Wiśniewski

Keyword(s):

Baltic Sea ◽

The Baltic Sea ◽

Sea Levels ◽

Probability Of Occurrence ◽

Extreme Sea Levels ◽

The Baltic

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Extreme sea levels in the Baltic Sea under climate change scenarios – Part 1: Model validation and sensitivity

Ocean Science ◽

10.5194/os-15-1399-2019 ◽

2019 ◽

Vol 15 (6) ◽

pp. 1399-1418

Author(s):

Christian Dieterich ◽

Matthias Gröger ◽

Lars Arneborg ◽

Helén C. Andersson

Keyword(s):

Climate Change ◽

Baltic Sea ◽

Regional Climate ◽

Climate Change Scenarios ◽

Confidence Limits ◽

The Baltic Sea ◽

Sea Levels ◽

Return Levels ◽

Extreme Sea Levels ◽

The Baltic

Abstract. We analyze extreme sea levels (ESLs) and related uncertainty in an ensemble of regional climate change scenarios for the Baltic Sea. The ERA-40 reanalysis and five Coupled Model Intercomparison Project phase 5 (CMIP5) global general circulation models (GCMs) have been dynamically downscaled with the coupled atmosphere–ice–ocean model RCA4-NEMO (Rossby Centre regional atmospheric model version 4 – Nucleus for European Modelling of the Ocean). The 100-year return levels along the Swedish coast in the ERA-40 hindcast are within the 95 % confidence limits of the observational estimates, except those on the west coast. The ensemble mean of the 100-year return levels averaged over the five GCMs shows biases of less than 10 cm. A series of sensitivity studies explores how the choice of different parameterizations, open boundary conditions and atmospheric forcing affects the estimates of 100-year return levels. A small ensemble of different regional climate models (RCMs) forced with ERA-40 shows the highest uncertainty in ESLs in the southwestern Baltic Sea and in the northeastern part of the Bothnian Bay. Some regions like the Skagerrak, Gulf of Finland and Gulf of Riga are sensitive to the choice of the RCM. A second ensemble of one RCM forced with different GCMs uncovers a lower sensitivity of ESLs against the variance introduced by different GCMs. The uncertainty in the estimates of 100-year return levels introduced by GCMs ranges from 20 to 40 cm at different stations and includes the estimates based on observations. It is of similar size to the 95 % confidence limits of 100-year return levels from tide gauge records.

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