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A massive iceberg nearly four times the size of Greater London has broken away from Antarctica.

The enormous lump of ice is thought to cover an area of around 6,000 sq km, which is around 15 times the size of the Isle of Wight, twice the size of Luxembourg and a quarter the size of Wales.

The giant ice shelf – which was part of an area on the west of Antarctica named Larsen C – has been monitored by scientists for the last 10 years after a huge crack began to form. An ice shelf is a large sheet of ice attached to land.

On Wednesday US satellite date showed the iceberg had finally split off, an event called “calving”, and had started to drift into the Weddell Sea, part of the Southern Ocean.

The new trillion-tonne iceberg is thought to be one of the 10 largest icebergs ever recorded, measuring over 200-metres thick and 5,800 square km.

Is the new iceberg caused by climate change? According to Professor David Vaughan from the British Antarctic Survey, "there is little doubt that climate change is causing ice shelves to disappear in some parts of Antarctica at the moment". He added that there are no obvious signs climate change is causing the whole of Antarctica to break up - but around the Antarctic Peninsula, where we saw several decades of warming through the latter half of the 20th century, "ice shelves are collapsing and ice loss increasing". In the case of Larsen C, the calving could be a result of climate change or it could be natural. In other ice shelves cracks can form naturally with no link to warming. Glaciologist Dr Martin O’Leary from Swansea University said they are not aware of any link to climate change.

Experts will continue to track the block amid fears sea currents and winds could push it north where it could break up and stray into the path of cruise ships visiting from South America. But the iceberg is not expected to move fast.

Professor Adrian Luckman, who has followed the iceberg's formation as part of Project MIDAS at Swansea University, said: "We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice.

"We will continue to monitor both the impact of this calving event on the Larsen C ice shelf, and the fate of this huge iceberg.

"The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is 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."

Since breaking off, the Antarctic peninsula, the most northern part of the continent, is now changed in shape, scientists said.

The rift had been monitored by scientists using the European Space Agency satellites.

In the 1950s a US Navy icebreaker ship recorded an object of 32,000 sq km. Since satellites have been used, the largest iceberg seen was 11,000 sq km after breaking off in 2000.

Experts say the new huge iceberg will not directly make sea levels rise because it was already floating before it broke off. But ice shelves act as buttresses holding back glaciers flowing down to the coast.

Dr Martin O’Leary, a Swansea University glaciologist and member of the MIDAS project team, said: “Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position.

"This is the furthest back that the ice front has been in recorded history. We’re going to be watching very carefully for signs that the rest of the shelf is becoming unstable.”

The similar Larsen A and B ice shelves, which are further north on Antarctica than Larsen C, collapsed in 1995 and 2002.

David Vaughan, glaciologist and director of science at the British Antarctic Survey, told Reuters that the two ice shelves collapsing "resulting in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise."

He said: "If Larsen C now starts to retreat significantly and eventually collapses, then we will see another contribution to sea level rise."