An iceberg half the size of Greater London has calved off Pine Island glacier in the Antarctic.

This week a radar instrument on the German satellite TerraSAR-X captured an image of a crack having grown to extend across the entire ice shelf at the front of the glacier since 2011. Scientists say that the 720-sqkm iceberg calved off in a natural event unrelated to the effects of global warming.

Andy Smith of the British Antarctic Survey said: "Although there's nothing to suggest this event is unusual, it's not to say that it's not interesting. We are extremely interested because we want to understand if the loss of a large block of ice has an affect on the flow of the glacier".

The large fissure in the Pine Island glacier was first spotted by a Nasa low-flying plane in 2011 at which time the iceberg was expected to break-free within a year.

The iceberg will be watched closely over the next few months as it moves and melts into the surrounding bay. Capturing this event allows researchers like Prof Angelika Humbert, a glaciologist and ice modeller with the Alfred Wegener Institute, to understand the processes that drive glaciers, and the way they fracture. "I use the images from the satellite to model the flow of the glacier and how the grounding line is retreating which allows us to predict the behaviour of the ice sheet over the next hundreds to thousands of years.

"A calving event of this size is relatively common with similar events occurring at the Pine Island glacier in 2007 and 2001".

She added: "The fact that we have radar satellites of this type that provide high resolution images on a weekly basis allows us to study calving events in real-time by following the propagation of fissures. The images allow us to really understand the processes occurring on the glacier".

Massive iceberg floating free after splitting from Pine Island glacier, Antarctica. Photograph: Alamy

The flow of the ice stream from the Pine Island Glacier has accelerated in recent years. Smith said: "The Pine Island glacier is quite significant because it is losing more ice to the sea than any other glacier in the world. The glacier is changing a lot and quickly."

Complete melting of the Pine Island glacier in the future would not only increase global sea-levels but it is also predicted that it could destabilise the entire West Antarctic ice sheet. Studying the glacier can help scientists to understand what factors contribute to the melting.

Smith said that he will form part of an expedition early next year run by the Natural Environment Research Council iSTAR programme to study the physical processes occurring on the glacier and in the surrounding ocean.