Ice sheets can retreat up to 600 meters a day during periods of climate warming, 20 times faster than the highest rate of retreat previously measured. An international team of researchers used high-resolution imagery of the seafloor to reveal just how quickly a former ice sheet that extended from Norway retreated at the end of the last Ice Age, about 20,000 years ago, as per a release. The team mapped more than 7,600 small-scale landforms called ‘corrugation ridges’ across the seafloor. The ridges are less than 2.5 m high and are spaced between about 25 and 300 metres apart.
These landforms are understood to have formed when the ice sheet’s retreating margin moved up and down with the tides, pushing seafloor sediments into a ridge every low tide. Given that two ridges would have been produced each day (under two tidal cycles per day), the researchers were able to calculate how quickly the ice sheet retreated. Their results (Nature) show the former ice sheet underwent pulses of rapid retreat at a speed of 50 to 600 metres per day. This is much faster than any ice sheet retreat rate that has been observed from satellites or inferred from similar landforms in Antarctica.
