Breakup of Petermann Glacier August 2010. Greenland Ice Sheet Each summer, snow retreats briefly at low elevations, and a narrow strip of rocky coastline.

Breakup of Petermann GlacierAugust 2010

Greenland Ice SheetEach summer, snow retreats briefly at low elevations, and a narrow strip of rocky coastline emerges.

As it thins and fractures, sea ice that packed into the mouths of fjords over the winter takes on the look of a mosaic made from blue and white stained glass.

Glaciers flowing down from the highland interior get a little slushy, at least on top; turquoise blue pools of melt water dot the surface.

North-eastern tip of Ellesmere Island (left) in the Canadian Arctic and north-western Greenland (right).

The green and purple-colored water pictured in the lower part of the image is Nares Strait

The aqua blue and white-colored areas on the right side of the image show a portion of the Greenland ice sheet, the second largest concentration of frozen freshwater on Earth.

In reddish colors, the northern hemisphere's longest-floating glacier, Petermann, can be seen stretching across the center of the lower part of the image and emptying into Nares Strait

Evidence of Global WarmingAlmost 19 years ago to the day, this image from August 1991 shows a much longer ice-tongue protruding further towards Nares Strait, a few days before the calving of three large icebergs.

The dot line across the glacier indicates the line of fracture of the icebergs in 1991.

Petermann spawned two smaller breakaways: one of 34 sq miles in 2001 and another of 10 sq miles in 2008

The glacier tongue in July 2002. Scientists began to express concerns about a rift which had appeared in 2001 - visible here in the centre

right of this image running horizontally

The glacier tongue in July 2005. The rift is filled with thin ice and covered with snow

A thin fracture near the edge of the rift indicates that it has continued to widen in this image captured in August 2007

The size of the rift in September 2008. After its initial formation, the rift on Petermann Glacier advanced toward the

glacier front, widening as it moved

Ice Rift at eye level

31 July: the breaking of the Petermann Glacier and the movement of the new iceberg towards Nares Strait

Caught of film as the break happened

4 August: the iceberg continues to break off from the glacier

On 5 August, the iceberg was already separated from the main glacier tongue. The ice loss from the Petermann Glacier was the largest such

event in nearly 50 years, although there have been regular and smaller 'calvings'

On 5 August 2010, an enormous chunk of ice, roughly 97 square miles (251 square kilometres) in size, broke off the Petermann Glacier along the north-western coast of Greenland. The glacier lost about one-quarter of its floating

ice shelf, said researchers

7 August: The 100 sq mile chunk of ice drifts into the North Strait between Greenland and Canada

Threat to oil rigs and shipping lanes

100 mile square chunk of ice drifting with the currents