The largest ice shelf in the Arctic has fractured, releasing all the water from the freshwater lake it dammed.
The Ward Hunt Ice Shelf is located on the north coast of Ellesmere Island in Canada's Nunavut territory.
The huge mass of floating ice, which has been in place for at least 3,000 years, is now in two major pieces.
The scientists who report the break-up in the journal Geophysical Research Letters (GRL) say it is further evidence of ongoing and accelerated climate change in the north polar region.
The researchers - Warwick Vincent and Derek Mueller of Laval University in Quebec City, Canada; and Martin Jeffries of the University of Alaska Fairbanks, US - have been studying the shelf onsite and through satellite radar imagery and helicopter overflights.
This is all extremely reassuring. No wonder the White House finds it necessary to redact environmental studies to show the earth is not warming.