Scientists from the British Antarctic Survey (BAS) have revealed compelling evidence that enormous icebergs, some comparable in size to the city of Cambridge, once drifted off the coast of the UK. The discovery, published in Nature Communications, centres on distinctive grooves carved into sediments beneath the North Sea seafloor, left by these massive icebergs during the last ice age, approximately 18,000 to 20,000 years ago.
This marks the first confirmed evidence of large, tabular icebergs in UK waters, suggesting the British and Irish Ice Sheet possessed ice shelves – floating extensions of the land-based ice. Researchers explain that these icebergs, reaching up to tens of kilometres in width and hundreds of metres thick, created deep, comb-like grooves as their undersides ploughed across the seabed.
The findings are significant for understanding the dynamics of past ice sheet behaviour and, critically, for providing clues about the future stability of the Antarctic ice sheet. In Antarctica, tabular icebergs are released from ice shelves which act as a crucial buffer, holding back glacial ice and preventing rapid melting into the ocean. The regular calving of these icebergs is a natural process which maintains the equilibrium of the ice sheet.
Data collected from seismic surveys, originally used for oil and gas exploration, revealed the preserved seabed grooves. Scientists observed a shift in the type of iceberg tracks around 18,000 years ago – from large tabular bergs indicating a normal calving cycle, to numerous smaller icebergs, indicating catastrophic ice shelf disintegration. This transition mirrors events witnessed more recently, such as the 2002 collapse of the Larsen B ice shelf in Antarctica which led to a dramatic acceleration in glacial flow and a contribution to sea level rise.
“We can actually document the catastrophic collapse of these ice shelves at the end of the last ice age using our data,”
British Antarctic Survey
The researchers now hope to refine the dating of the seafloor sediments to understand if the disintegration of ice shelves caused the rapid retreat of the British and Irish Ice Sheet, or if it was a result of the retreat itself. Determining this relationship is crucial for predicting future behaviour of the Antarctic ice sheet.
