Colossal ancient icebergs left grooves on the bottom of the North Sea

During the rapid retreat of ice sheets in northern Europe around 18,000 to 20,000 years ago, city-sized icebergs floated past the coast of Britain leaving behind preserved scour marks in the seafloor sediments of the North Sea. Research conducted by James Kirkham and his team from the British Antarctic Survey uncovered evidence of these massive icebergs, estimating them to be as wide as a mid-sized British city.

These findings suggest that the ice shelves of the British and Irish ice sheet also had tabular icebergs, similar to the spectacular ones seen in Antarctica today. The study indicates a shift from large icebergs to smaller ones as the ice shelves disintegrated in response to rising temperatures, a process observed through radiocarbon dating of sediments dating back 20,000 to 18,000 years ago.

Contrary to the belief that large calving events in Antarctica signal instability, recent research by Emma MacKie at the University of Florida suggests that these events do not necessarily indicate impending collapse. Monitoring of tabular iceberg size in satellite data since the mid-1970s shows a relatively stable trend, emphasizing that continuous large calving events are not a cause for alarm.

The study by Kirkham and MacKie highlights the importance of understanding the dynamics of ice shelves and the significance of different iceberg sizes in assessing the stability of polar ice sheets, both past and present.