Hidden landscapes: North Sea reveals secrets of ancient ice sheet
Scientists have determined that over the last million years, land formations created by a massive ice sheet have been concealed under thick layers of silt. New images from the North Sea reveal this.
Researchers detailed their latest findings in the scientific journal Science Advances. New, detailed 3D images facilitated the discovery of significant structures beneath the North Sea's surface. The evidence presented in the sources also challenges the existing model of early North Sea glaciation.
The structures were hidden in the post-glacial layer of clay
Following the ancient glacier, researchers encountered a thick layer of clay covering an area of approximately 10,000 square kilometres. The clay averages 30 metres in thickness, with some places reaching up to 120 metres. The thickest part is located on the Norwegian side, in the northeast. Researchers believe that the clay was formed from sediments deposited by the glacier that once moved through this region. According to today's maps, the glacier covered Norway and extended toward the British Isles.
Patterns on the sea floor come from strong ocean currents
Scientists captured these hidden structures, describing them in "clear and incredible" detail, buried under about 1 kilometre of silt. The images show patterns on the seafloor consistent with the advancement and retreat of a single, large ice sheet, which existed about a million years ago—contradicting theories that more miniature ice sheets repeatedly expanded and retreated during this period. These theories were based on numerous scratch marks that some researchers believed were caused by glaciers. However, it turns out they originate from strong ocean currents.
"We see only conclusive evidence of one major ice advance during this period," said Christine Batchelor, senior lecturer in physical geography at the University of Newcastle in the UK and co-author of the new study describing the landforms, in an interview with Live Science. She added that areas outside the current research region might still contain evidence of several smaller ice sheets.
The scientific team used high-resolution sound wave data to reveal the landforms. As the researchers reported, they were not searching for anything specific and were surprised to find evidence of a single grounded ice sheet—an ice sheet that rests on land rather than on water. From these findings, researchers can reconstruct the glacial past of the region.
Determining how ice behaved during major climate changes is crucial
A giant ice sheet formed during the last glacial period known as the Middle Pleistocene Transition (MPT), which lasted from 1.3 million to 700,000 years ago. The ice age itself began about 2.6 million years ago and ended 11,700 years ago. The research focused on the MPT because it marks a time when glacial periods suddenly became more intense and shifted from occurring every 40,000 years to every 100,000 years.
"The main reason we are interested in this broad time period from about a million years ago is that this is when climate change occurs," said Batchelor. "Glacial periods become longer and more intense, so there is a lot of effort focused on trying to determine why this change happened," she added.
The new research does not yet provide answers, but understanding where ice spread during critical moments for climate change over a million years ago can help scientists recreate a picture of the conditions that led to these global transformations and contribute to the study of contemporary climate changes.
