A gigantic iceberg, baptised Petermann Island by the National Ice Center, has broken off from the glacier of the same name, in the north of Greenland, sending an "alarm signal" according to experts concerned about the consequences of rising ocean temperatures on the melting of ice caps.

Last 5 or 6 August, an iceberg covering 250 square kilometres, nearly four times the size of Manhattan, broke off from the 70 km-long tongue of ice that connected it to the mainland. The NASA researcher behind the discovery, Trudy Wohlleben, said that cracks had already raised concerns about the possible split for more than a year.

It is the largest event of its kind to occur in the region for fifty years. The iceberg is even the largest ever to be detected by a satellite. According to Andreas Muenchow of the University of Delaware (USA), it contains enough freshwater "to supply the whole of public drinking water network in the U.S. for 120 days".

Although no definite conclusion can be made, scientists are slowly coming to a consensus about the proposed rise in ocean temperatures. While it is natural for a glacier to rejects the excess ice into the fjords, the magnitude of the phenomenon tends to corroborate the thesis of the accelerated thaw of the ice cap in Greenland. For Konrad Steffen of the University of Colorado (USA): "It is an alarm signal that serves to remind us that the changes are already perceptible".

While only a few years ago meteorologists considered the Greenland ice cap to be highly stable, they now believe that its melting could cause a rise in sea levels of between 50 centimetres and one meter over the coming century.

For more information:

• Read the article in Les Echos dated 14/08/2010 (in French only)
• Read the article in LE DEVOIR dated 11/08/2010 (in French only)
• Read the article in Le Monde dated 08/08/2010 (in French only)
• Read the UNEP report dated 2008
• View the UNEP map (in French only)