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Sea level rise after the last ice age: more knowledge

New geological data has given more insight into the rate and magnitude of global sea level rise following the last ice age, about 11,700 years ago. This information is of great importance to understand the impact global warming has had on the ice caps and on sea level rise. The findings have been published in the scientific journal Nature by researchers from Deltares, LIAG, BGR, Utrecht University, TNO Netherlands Geological Service, Delft University of Technology, the Netherlands Institute for Sea Research (NIOZ), University of Leeds, University of Sheffield, University of Amsterdam.

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BGR archive image: The Doggerland, the bridge between Great Britain and the European mainland, disappeared due to sea rise in the early Holocene.

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Global sea level will rise rapidly in the coming century; perhaps by more than 1 metre. This is primarily caused by increasing concentrations of greenhouse gases (source: IPCC). Submerged peat layers from the North Sea show that these rates were seen in two earlier phases: 10,300 and 8,300 years ago. Ice sheets melted then due to rapid warming after the last ice age.

Drilling from the North Sea. In the center you can clearly see how a layer of brown peat is covered by a layer of gray clay, the moment (8700 years ago) that this part of the North Sea was flooded.

Better understanding of sea level rise

The new knowledge into the rate of sea level rise during the early Holocene offers an important point of reference for scientists and policymakers, especially as we are now faced with a similar situation with rapidly melting ice sheets due to global warming. The research provides valuable new insights for the future.

As a result of the current rise in greenhouse gas concentrations, climate models by the Intergovernmental Panel on Climate Change (IPCC) expect sea levels to rise by several metres by 2300. Some scenarios indicate a rise of more than one metre per century. An important difference with the early Holocene is that the consequences of sea level rise are far greater today and in the future. This is due to a growth in population and the current presence of infrastructure, cities and economic activity.

Unique dataset in the North Sea region

Global sea level rose quickly following the last ice age.  This was as a result of global warming and the melting of enormous ice caps that covered North America and Europe. Until now, the rate and extent of sea level rise during the early Holocene were not known due to a lack of sound geological data from this period. Using a unique dataset for the North Sea region, the researchers have now been able to make highly accurate calculations for the first time. They analysed a range of boreholes from the area in the North Sea that was once Doggerland, a land bridge between Great Britain and mainland Europe. This area flooded as sea level rose.

By analysing the submerged peat layers from this area, dating them and applying modelling techniques, researchers showed that, during two phases in the early Holocene, rates of global sea level rise briefly peaked at more than a metre per century. By comparison, the current rate of sea level rise in the Netherlands is about 3 mm annually, the equivalent of 30 centimetres per century, and is expected to increase.

Furthermore, until now there has been considerable uncertainty about the total rise between 11,000 and 3,000 years ago. Estimates varied between 32 and 55 metres. The new study has eliminated that uncertainty and it shows that the total rise was around 38 metres.

Chronological Classification at LIAG

The foundation for the new scientific findings was based on data from various peat layers, including those obtained from the German Bight through expeditions with the BGR. The dating and subsequent chronological classification of the sediments formed the basis for the modeling and were carried out at the geochronology laboratory of the LIAG Institute for Applied Geophysics. Radiocarbon dating, also known as the 14-C method, relies on determining the radioactive isotope 14C, which decays with a half-life of 5730 years. This isotope forms in the upper layers of the atmosphere and is absorbed by all living organisms and the oceans.

"The results from the sediment analysis provide, for the first time, precise data from the submerged Doggerland, offering crucial insights into the interplay between climate, ice melt, and sea level rise," explains Prof. Dr. Manfred Frechen, co-author and head of measurements at the geochronology laboratory at LIAG for the study. "These comparative values can serve as a foundation to help prepare for future changes caused by anthropogenic global warming and the resulting sea level rise."

Backgroundinformationen

Partner:

  • Deltares, Utrecht und Delft, Die Niederlande (Hauptautorenschaft)
  • Wageningen University and Research, Wageningen, Die Niederlande
  • University of Sheffield, Sheffield, UK
  • Utrecht University, Utrecht, Die Niederlande
  • Delft University of Technology, Delft, Die Niederlande
  • Leeds University, Leeds, UK
  • LIAG Institute for Applied Geophysics, Hannover, Deutschland
  • Royal Netherlands Institute for Sea Research (NIOZ), ‘t Horntje, Die Niederlande
  • TNO – Geological Survey of the Netherlands, Utrecht, Die Niederlande
  • Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Deutschland
  • University of Amsterdam, Amsterdam, Die Niederlande
  • VU University Amsterdam, Amsterdam, Die Niederlande

 

Contact at LIAG

Science
Prof. Dr. Manfred Frechen
Manfred.Frechen(at)liag-institut.de  

Public Relations
Greta Clasen
Tel.: 0511 643 2066
greta.clasen(at)liag-institut.de

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