Norway’s ancient ice sheet may have retreated more than 600 meters per day at the end of the last glaciation. That’s 10 times faster than previous estimates, suggesting that modern glaciers may be melting into the seabed much faster than scientists previously thought, says Christine Batchelor of Newcastle University in the United Kingdom. „It potentially shows us that ice sheets are physically capable of retreating at rates that are orders of magnitude faster than anything we’ve seen [before],“ she says. „It’s a warning of what could happen if we continue on our trajectory—or especially if we end up on an upward trajectory—of warming in the coming decades.“ Ice floes are attached to the seafloor until rising sea temperatures break the connection by melting the ice-ocean interface on the seafloor, leaving the ice floating as an ice shelf. The boundary of ice attached to bedrock is called the grounding line. For the past 50 years, scientists have used satellite data to track the location of grounding lines in ice floes in Antarctica and Greenland. The receding grounding lines have raised global sea levels by about 0.7 millimeters per year since the 1990s. But Batchelor and her colleagues suspected that the satellite data might not tell the whole story. They decided to take a closer look at the history of grounding line changes at the end of the last glacial period, 15,000 to 19,000 years ago. At that time, the Scandinavian ice sheet began to retreat as the climate began to warm as part of a natural cycle of heating and cooling, Batchelor says.