WW-I-8: Sea levels

The picture shows a narrow sandy coast. The edge of the dune has broken off.Click to enlarge
Sea level rise puts the coastlines at risk.
Source: Photograph: © jomo333 / stock.adobe.com

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents


WW-I-8: Sea levels

The calculated mean values of selected sea level measurements recorded in the North and Baltic Seas in the course of 19 years illustrate the rise in sea levels. In most cases, these increases in sea level are significant.

The line chart shows the average of the annual mean tide water over 19 years for Cuxhaven (North Sea) from 1843, for Travemünde (Ostsee) from 1853, for Kiel (Ostsee) from 1901, for Wittdün (North Sea) from 1936, for Saßnitz (Ostsee) from 1954 and for Borkum (North Sea) from 1963. All time series show a significantly increasing trend.
WW-I-8: Sea levels

The line chart shows the average of the annual mean tide water over 19 years for Cuxhaven (North Sea) from 1843, for Travemünde (Ostsee) from 1853, for Kiel (Ostsee) from 1901, for Wittdün (North Sea) from 1936, for Saßnitz (Ostsee) from 1954 and for Borkum (North Sea) from 1963. All time series show a significantly increasing trend.

Source: BfG (level database of the Federal Water and Shipping Administration)

The sea levels of North Sea and Baltic Sea are rising

The glaciers and ice sheets on the poles are melting thus providing the seas with large quantities of meltwater. At the same time rising water temperatures make the sea water expand. Consequently, this leads to global rise of sea levels. The Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) published in September 2019 by the Intergovernmental Panel on Climate Change (IPCC) provides projections of earth system models for mean global sea level rise and for extreme values and their frequency, based on scenarios of socio-economic development. The probable bandwidth of mean global sea level rise for the end of this century compared to the year 2000 is between 61–110 cm, while the median is estimated as 84 cm. These values are higher than stated in the previous IPCC case report published in 2013, because new findings suggest a higher contribution of meltwater from the antarctic ice sheet. The SROCC also demonstrates that, as a consequence of sea level rise, storm surge water levels be higher than before. It is expected that sea levels will continue to rise beyond the year 2100 and that they will remain high.

However, increases in sea levels occur in very different ways regionally and locally; this also applies to the North Sea and the Baltic Sea. Water levels along the German coastlines have been measured regularly for over 150 years. This makes it possible to state concrete figures regarding the changes. In the southern part of the German Bight the mean sea level rise in the course of the past 100 years amounted to 1.1–1.9 mm per annum – not including land subsidence effects. This means that the rates of increase for the North and Baltic Seas are just slightly below the values for global sea level rise. However, if the influence of land subsidence is taken into account, the rates of increase in some German coastal zones reach values of 1.6–2.9 mm per annum.

The North Sea is subject to tidal changes. The mean value of mid-tide (MTmw) is therefore of crucial importance. In contrast, the Baltic Sea – owing to its geographical location and tenuous link with the oceans – is subject to comparatively weak tidal influence; this is why in this case the annual mean water levels (MW) are relevant. For these coefficients of water level, a ⁠moving average⁠ across 19 years was calculated. For the selected North Sea levels at Cuxhaven as well as Borkum and Wittdün on Amrum, the mid-tide levels suggest significantly rising values. The Baltic Sea levels at Kiel, Travemünde and Saßnitz also show a significant rise in sea level. Differences between the rate of sea level rise in the North Sea and the Baltic Sea are due to differences in vertical land movement.

For coastal regions, in particular estuaries and low-lying coastal zones, rising sea levels signify a very slow increase in risks from storm surges. Estimates for the development by end of this century vary.

Another consequence of rising sea levels is progressive coastal erosion which affects sandy coastal zones exposed to sea surges, thus also affecting many popular bathing beaches. Such coastal sections are the foundation of tourist development in the North Sea and Baltic Sea areas. This confronts coastal protection authorities with additional challenges. Likewise, the operation of waterways is expected to face additional challenges, e.g. in terms of sediment management.



WW-I-7: Water temperature in the sea

WW-I-9: Intensity of strom surges

WW-R-4: Investment in coastal protection



Designing integrated development strategies for ecosystems in coastal zones including estuaries. Establishing sanctuaries for ecosystems affected by sea level rise. Making use of synergies between nature conservation and coastal protection (DAS, ch. 3.2.5)

Examining and documenting any changes in currents, erosion or sedimentation in estuaries and shipping routes, arising from the predicted sea level rise (DAS, ch. 3.2.11)

For existing or planned industrial sites, consideration must be given, both nationally and internationally, to the impacts of climate change such as the consequences of the expected sea level rise in areas near a coastline. (DAS, ch. 3.2.12)

Sea level rise and the related groundwater level rise as well as the increase in coastal erosion tendencies call for extra efforts in the protection of coastal zones. This is required as a foundation for essential new focal points regarding the development of coastal landscapes. (DAS, ch. 3.2.14)