Thousands of years ago, massive icebergs, like those seen today in Antarctica, were drifting just 90 miles off the coast of the United Kingdom.
A new study has found clear evidence of these frozen giants carving deep marks into the seafloor of the North Sea, revealing a dramatic chapter in the region’s icy past.
The findings, published in the journal Nature Communications, show that during the last ice age—about 18,000 to 20,000 years ago—huge, flat-topped icebergs broke off from glaciers covering the British and Irish Isles.
As the climate warmed and the ice sheet began to retreat, these icebergs floated out into the North Sea, dragging their heavy undersides across the seabed and leaving behind deep grooves.
These plow marks were discovered using seismic survey data gathered from the Witch Ground Basin, an area between Scotland and Norway.
The data was originally collected to help locate drilling sites but revealed stunning geological patterns hidden beneath the ocean floor.
Dr. James Kirkham, a marine geophysicist with the British Antarctic Survey (BAS), explained that the icebergs responsible for these marks were enormous—some as wide as entire cities like Cambridge or Norwich, and hundreds of meters thick.
While scientists had seen smaller iceberg scratches before, these broad marks are the first solid evidence that such large icebergs once roamed the North Sea.
The presence of these tabular, or flat-topped, icebergs suggests that the British and Irish Ice Sheet had floating ice shelves, much like those surrounding Antarctica today.
Ice shelves play a crucial role in holding back the glaciers behind them. When these shelves break apart, the glaciers can suddenly speed up and release more ice into the ocean, raising sea levels.
Dr. Kelly Hogan, another BAS researcher, said their data shows how this happened in the North Sea. Around 18,000 years ago, the types of plow marks changed—from those made by giant tabular icebergs to ones made by many smaller bergs.
This shift signals that the ice shelves had collapsed, unleashing a wave of smaller icebergs as the system broke down.
A similar event happened in 2002 when Antarctica’s Larsen B ice shelf suddenly collapsed after warming caused meltwater to crack through the ice. The glaciers behind it quickly sped up, increasing sea-level rise.
While scientists don’t yet know if the ancient collapse triggered the ice sheet’s retreat or vice versa, this study offers important clues about how modern ice shelves might respond to today’s warming world.
Source: British Antarctic Survey.
