An iceberg said to be twice the size of Manhattan has broken free from the Petermann Glacier in Greenland.
NASA satellite images have helped scientists to trace movements ever since breaks in the ice were detected several years ago.
The speed at which changes to the glacier have taken place are said to have surprised experts.
The Petermann Glacier connects the Greenland ice sheet to the Arctic Ocean. Two years ago it unleashed another massive ice chunk into the sea.
Icebergs from the glacier have caused problems for shipping in waters near Canada.
The latest movement is not predicted to have an impact on sea levels as the ice was already part of a shelf that was effectively floating.
One researcher described the changes as dramatic, but said it was too early to attribute the loss of ice to global warming.