PhD Defence: Cooling of the North Sea

Climate change and sea-level rise can have significant consequences for low-lying countries such as the Netherlands. In the past, climate has changed between warm periods and cold ice ages. By studying the natural environmental response in the past, we can improve future predictions. The onset of ice ages is currently insufficiently studied, while more knowledge on this can provide insights into the interaction between climate, sea-level changes, and landscape development.
In this dissertation, a reconstruction is made of landscape and climate development in the North Sea during the onset of the last ice age (about 80-65 thousand years ago). For this, seismic data and cores from the Brown Bank Formation, present under the seabed of the North Sea, were used. The sediments from the cores contain a lot of information about developments in climate, landscape, and sea level. Through various analyses, such as chemical analyses and the study of (microscopic) fossils, we discovered that sea level remained relatively high, while climate had already cooled significantly. As a result, the southern North Sea turned into an Arctic bay. Meanwhile on land, the forests gave way to an open landscape.

Climate was very unstable during the onset of the last ice age, with relatively rapid (about 1000 years) fluctuations between cold and warmer periods. These climate fluctuations had a direct effect on the landscape in and around the North Sea, affecting the current strengths in the sea. These rapid climate fluctuations caused rapid changes in temperature, vegetation, and depositional environments in large parts of Western Europe and Greenland and can be linked to the weakening and restarting of the circulation in the Atlantic Ocean.