Monster iceberg splits off Antarctic Larsen C ice shelf

After years of cracking, growing kilometre by kilometre, one of the largest icebergs in the world has finally broken off an Antarctic ice shelf.

A rift on the Larsen C ice shelf, on the continent's most northern point, has been slowly growing since it was first spotted in 2014. From the middle of last year, the crack's growth began to speed up.

Now the ice has completely crumbled, breaking off an iceberg around 5800 square kilometres - three times the size of Stewart Island. It weighs 1 trillion tonnes.

It's one of the largest icebergs measured in the world. In comparison, the iceberg which sunk the Titantic was around 0.01 square kilometres.

Scientists say while it's impossible to know for sure, it's not likely the trillion-tonne iceberg will stay in one piece.

"[It's] more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters," MIDAS's lead investigator Professor Adrian Luckman said.

As it melts it won't raise the sea level, as ice shelves already float on the water.

But the shelves hold back the greater ice sheet, land-based ice making up the bulk of the Antarctic continent.

The broken-off berg makes up around 12 percent of the area of Larsen C. Its loss is likely to speed up the destruction of the main ice shelf, until it disappears - like Larsen A and B before it.

When that's gone, there won't be as much holding the ice sheets in place. When they melt, it does cause the sea level to rise.

UK-based Project MIDAS, which has been tracking the rift, says after its jump in length, the rift began to gape and widen.

As it widened, there was more pressure, the to-be iceberg dragging at the main ice shelf to break away.

It's left the shelf at its most retreated position ever recorded - and has "fundamentally changed" the Antarctic Peninsula's landscape.

Dr Paul Holland, ice and ocean modeller at the British Antarctic Survey (BAS), said while it's not known if climate change affected the massive iceberg's calving, it is likely climate change has caused the ice shelf itself to thin.

"Iceberg calving is a normal part of the glacier life cycle, and there is every chance that Larsen C will remain stable and this ice will regrow," he said.

"However, it is also possible that this iceberg calving will leave Larsen C in an unstable configuration. If that happens, further iceberg calving could cause a retreat of Larsen C."

Glaciologist Professor Eric Rignot previously described the potential loss of the ice sheets, which make up the Antarctic continent, as being "like an eggshell that became too thin".

"It's not going to melt away. It's going to fracture," he said.

"It's going to reach a limit beyond which it is not stable."

Dr Martin O'Leary, a glaciologist who also worked as a part of the MIDAS team, said the shelf is now in a "very vulnerable position".

"This is the furthest back that the ice front has been in recorded history," he said.

"We're going to be watching very carefully for signs that the rest of the shelf is becoming unstable."