Buried landforms reveal ancient glacial past of North Sea

An international research team including glaciologists from the University of Newcastle in the UK has discovered an extremely well-preserved glacial landform buried approximately one kilometer underground in the North Sea.

Researchers used sound wave data, known as seismic data, to reveal Ice Age landforms buried under almost 1km of mud in the North Sea. The results, reported in the journal Science Advances, suggest that the landform formed about a million years ago when an ice sheet centered in Norway spread toward the British Isles.

This is important because the timing of this ice advance corresponds to a period of global cooling called the mid-Pleistocene transition.

Glacier topography reveals how past ice sheets responded to changes in climate, which can help more accurately predict how current ice sheets will respond to a warming climate. . The challenge is that glacial landforms are often buried under thick layers of sediment, making them difficult to identify.

Dr Christine Batchelor, Senior Lecturer in Physical Geography at the University of Newcastle, played a key role in the research, assisting with the mapping and interpretation of the terrain.

“To fully understand the link between ice sheets and climate, we need to study how ice sheets responded to long-term climate change in the past,” Dr Batchelor said. “Our results, using modern seismic data, suggest that the northwestern European ice sheet expanded significantly in response to climate cooling about a million years ago.”

Lead author of the paper, Dr Dag Ottesen from the Geological Survey of Norway, said: “This study was made possible by the availability of 3D seismic data in the North Sea, allowing us to examine buried landforms in amazing detail. I was able to do it.”

3D seismic technology has been developed to assess the suitability of deposits for oil and gas or renewable infrastructure. However, this same data can be used to study buried landforms produced by glacial processes.

The mapped landscape includes streamlined features carved beneath the former ice sheet and ridges that record the scars left as the ice sheet began to retreat. Despite its age, this landform bears a striking resemblance to similar features formed by ice sheets much more recently.

Buried landforms provide new knowledge about the mechanisms by which ice sheets retreat. For such a gentle topography to remain unchanged, the previous ice sheet must have retreated rapidly through leading edge liftoff and surfacing.

In addition to the glacial landforms, the researchers also found long, narrow grooves carved into the former ocean floor, which they interpreted to have been caused by strong ocean currents. These landforms are buried even deeper than the glacial landforms, indicating that they were generated before the ice sheet advanced.

“Our high-resolution data shows that the shape and size of the grooves are consistent with their origin as ocean current grooves,” Dr. Ottesen said. “This differs from previous interpretations of these landforms as glacial landforms and rewrites our understanding of the history of North Sea glaciers.”

By providing a new level of detail about buried landforms, this discovery sheds light on the evolution of the North Sea in the recent geological past. The study shows that the North Sea was characterized by strong ocean currents until about a million years ago, after which it became more directly influenced by ice sheets.

The researchers acknowledge that a limitation of their study is a lack of data on the exact age of the landforms.

“A wealth of seismic data is now available for the North Sea,” Dr Batchelor said. “The next step is to obtain long sediment cores that will allow researchers to better understand the timing of glacial events.”

Other co-authors are Helge Løseth of Equinor ASA in Trondheim and Harald Brunstad of Aker BP ASA in Trondheim.