Monolithic rectangular iceberg photographed by Nasa

Nasa has released a striking photograph of an iceberg with perfectly straight edges and pointed right-angle corners

The mile-wide 'tabular iceberg' was seen floating among sea ice off the Larsen C ice shelf by one of the US space agency's research planes.

An expert said the sharp edges of the iceberg likely indicate that it has recently detached from an ice shelf and was photographed before the sea and wind could wear down its edges. 

There has been suggestion that the iceberg could have broken away from the shelf as a result of global warming.

Kelly Brunt, a glaciologist at the University of Maryland and Nasa, said tabular icebergs gain their distinctive shape when an angular protrusion breaks off from an ice shelf.

She compared the process to a fingernail growing too long and cracking off.

"We get two types of icebergs. We get the type that everyone can envision in their head that sank the Titanic, and they look like prisms or triangles at the surface and you know they have a crazy subsurface. And then you have what are called 'tabular icebergs'," she  said.

"What makes this one a bit unusual is that it looks almost like a square," she added in an interview to Live Science. 

The monolithic berg is estimated to be 1.6km or 1 mile across with only 10 per cent of its total mass showing above the water. 

The subsurface body of tabular icebergs usually mirrors the regular-looking and geometric form of its visible part. 

It was photographed as part of Operation IceBridge, the largest ever aerial survey of the planet's ice which documents changes in the sea around Greenland and in Antartica. 

The survey is building a three-dimensional map of the ice at both poles. 

Nasa has been focussing on the Larsen C shelf since a trillion-tonne iceberg twice the size of Luxembourg broke off from it last summer.