Northern Greenland’s Petermann Glacier lost an iceberg Thursday, according to Nasa satellite images. The iceberg—twice the size of Manhattan—which broke off a tongue of ice extending from the end of the glacier, is the second such iceberg to calve off the Petermann in the past two years, surprising many experts. “It is not a collapse but it is certainly a significant event,” said a Nasa scientist. “It’s dramatic. It’s disturbing,” declared an observer from the University of Delaware. While the change in the glacier’s makeup over recent years may be perplexing and add to concerns about unusually warm temperatures thinning Greenland’s ice shelf, the latest iceberg to break off is not likely to impact sea levels because it was already floating.