A CAMBRIDGE scientist has warned that the “decaying” of the Greenland ice sheet risks pushing up the sea level and threatens coastal cities around the world.

Peter Wadhams, professor of ocean physics and head of the polar ocean physics group at the University of Cambridge, said he had observed first hand drastic changes to conditions in the Arctic.

The 71-year-old, who has led 55 expeditions to the region during his career, compared flowing melt water to the Niagara Falls as ice in the region disappeared.

Speaking from near the settlement of Kangerlussuaq on the south-west edge of Greenland, Mr Wadhams said there had been “large changes” to the area since his last visit five years ago.

“It’s certainly a far more rapid rate of ice loss going on now than at any time in the past,” he said.

“The rate of global sea level rise … is really completely dependent now on the loss from the Greenland ice sheet, that’s going to be going up quite rapidly.

“The first time I was here 30 years ago there was never any melt from the Greenland ice sheet even in summer.”

The professor, who first visited the Arctic in 1969, said the melting of ice had moved from the low-altitude edges of the Greenland ice sheet to include its surface at the centre.

“It’s coming down more or less like Niagara Falls, down through holes all over the ice sheet,” he said.

Mr Wadhams said 300 cubic kilometres of ice was lost from the Greenland sheet every year.

If the entire Greenland ice sheet melted the sea level would rise by seven metres, flooding most of the world’s coastal cities, the professor warned.

“It’s decaying and decaying quite rapidly,” he said.