They say it will take about two years for the block of ice to float south to the east coast of Canada where it will eventually melt. It is the largest Arctic iceberg to break free in almost 50 years, they say. It separated from the Petermann glacier on the far northern tip of Greenland, above the Arctic Circle. The chunk of ice is about 30km long and 10km wide.
Canadian experts discovered the new ice island using Nasa satellite images.
Glaciers are giant rivers of ice that slowly flow down from mountains. And if the mountains are near the sea, the ice ends up in the water.
Scientists say that although global warming probably played a role in creating the new iceberg, ocean currents and strong winds also helped. However, giant glaciers are breaking up every day, from the Arctic to Antarctica to South America.
The total amount of ice in the world's glaciers is slowly decreasing.
The Petermann glacier, one of Greenland's largest remaining glaciers, is also losing much of its mass as warmer sea water melts it from underneath. The Nasa images showed the glacier had lost about one-quarter of its floating ice shelf.
The World Glacier Monitoring Service conducted a survey five years ago which showed that 90 per cent of the glaciers it studied were retreating, or melting.
Scientists say the melting of glaciers could eventually cause sea levels to rise as the ice turns into water. Sea levels could rise by nearly a metre by the end of the century, they warn.
The new ice sheet will slowly drift along 'iceberg alley', where a large number of icebergs are floating in the sea. It will then enter the North Atlantic, where the Titanic hit an iceberg before sinking in 1912.
I captained my sailing boat through 'iceberg alley' last summer as I returned from the Arctic. We watched as chunks of ice as big as city buses broke off and crashed into the sea.