New insights into sea-level rise since the last ice age
New geological data provides greater insight into the rate and magnitude of global sea-level rise following the last ice age, about 11,700 years ago. This information is important for understanding the impact that global warming has had on the ice caps and on sea-level rise.
The researchers from Deltares, Utrecht University, TNO, Delft University of Technology, the Netherlands Institute for Sea Research (NIOZ), the University of Leeds, the University of Sheffield, the University of Amsterdam, LIAG and BGR published the findings in the scientific journal Nature.
Better understanding
The new knowledge of the rate of sea-level rise during the early Holocene offers an important point of reference for scientists and policymakers, especially as we are 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, due to population growth, infrastructure, cities and economic activity.
Unique dataset
The global sea level rose quickly following the last ice age, as a result of global warming and the melting of the 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 were 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, an area that flooded as the 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 3mm 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, with estimates varying between 32 and 55 metres. The new study has eliminated that uncertainty and shows that the total rise was around 38 metres.
Groundbreaking research
Marc Hijma, a geologist at Deltares and the lead author of the study, said: “With this groundbreaking research, we have taken an important step towards a better understanding of sea-level rise after the last ice age. By drawing on detailed data for the North Sea region, we can now better unravel the complex interaction between ice sheets, climate and sea level. This provides insights for both scientists and policymakers, so that we can prepare better for the impacts of current climate change, for example by focusing on climate adaptation.”
NIOZ researcher Gert-Jan Reichart is one of the initiators of this interdisciplinary research project. Together with Sytze van Heteren (TNO), he launched the data collection campaigns aboard the RV Pelagia held in 2017 and 2018. This effort expanded and ultimately led to the study now published. The chemical analysis of the drilled cores, which assisted in determining when the North Sea flooded, was mainly executed by Rick Hennekam (NIOZ). Reichart emphasized the importance of such collaborations: “Collaborations like this, where each institution brings their unique expertise and knowledge, are essential to help us understand the complex processes of climate changes in the past.”
