“Glacial speed” may seem like an oxymoron—but consider the recent record-breaking pace of Jakobshavn Isbræ, one of Greenland’s largest glaciers. By analyzing satellite images taken every 11 days from early 2009 through spring of 2013, researchers found that the ice stream’s average speed in the summer of 2012 peaked at a whopping 46 meters (half the length of a football field) per day , the researchers report today in The Cryosphere. That flow speed, between 30% and 50% faster than the peak rates seen in previous summers, is the fastest ever recorded for an ice stream in Greenland or Antarctica, the researchers say. Jakobshavn Isbræ, widely believed to have spawned the iceberg that sank the Titanic, sheds ice into a deep fjord along Greenland’s southwestern coast (image; the glacier lies over the horizon in the far background). Although Jakobshavn Isbræ’s summer surges are short-lived, the glacier’s average annual speed for the last couple of years is almost three times that measured in the 1990s. Between 2005 and 2010, Greenland’s glaciers dumped enough ice into the sea to raise sea level an average of about 0.7 millimeters per year, with Jakobshavn Isbræ contributing about one-seventh of that total. While for now the speediest, Jakobshavn Isbræ isn’t alone: Previous studies have shown that Greenland’s 200 largest glaciers have sped up, on average, about 30% in the last decade.