Second crack splits off in Antarctic Larsen C ice shelf

An enormous crack splitting through an Antarctic ice shelf has splintered off into two separate branches.

A rift has been slowly growing through the Larsen C ice shelf in recent years, speeding up since late 2015.

When it reaches the edge of the shelf, which is off the continent's northernmost point it's likely to fracture off a massive iceberg around 5000 square kilometres - three times the size of Stewart Island.

The break-off of such a large iceberg could destabilise the ice shelf and potentially lead to its eventual destruction.

At the beginning of May, Project MIDAS, which has been tracking the rift, observed a new development.

"While the previous rift tip has not advanced, a new branch of the rift has been initiated approximately 10km behind the previous tip, heading towards the ice-front," it said.

It says while the length of the rift hasn't been increasing, it's been widening for several months.

"This widening has increased noticeably since the development of the new branch, as can be seen in measurements of the ice flow velocity."

Larsen C ice shelf Antarctica rift crack (Project MIDAS)
The current location of the rift on Larsen C, as of May 1 2017 (Project MIDAS)

Larsen C is the third ice shelf to be named after the explorer in the region; its neighbours, Larsen A and B, both splintered into nothingness after similar events.

Project MIDAS says once this iceberg breaks off, the shelf will be left at "its most retreated position ever recorded".

"This event will fundamentally change the landscape of the Antarctic Peninsula."

The crack is still being monitored, with glaciologists unsure exactly when the ice will give in and splinter off.

"To be modelling these cracks is extremely challenging. It's a little bit like being able to predict the next earthquake," glaciologist Professor Eric Rignot said last month.

As ice shelves float on the water, the effect on global sea level rise if they do melt is minimal. A bigger concern is whether the shelves are holding back the greater ice sheets - land-based ice which, if it melted, would affect sea level.

The crack is still being monitored by Project MIDAS, a part of the British Antarctic Survey, and NASA, however now that it's winter down south, it's harder for the scientists to see new changes.

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