Image copyright NASA/SUOMI NPP/SIMON PROUD Image caption This view of the iceberg was taken by Nasa's Suomi NPP satellite

One of the biggest icebergs ever recorded has just broken away from Antarctica.

The giant block is estimated to cover an area of roughly 6,000 sq km; that's about a quarter the size of Wales.

A US satellite observed the berg on Wednesday while passing over a region known as the Larsen C Ice Shelf.

Scientists were expecting it. They'd been following the development of a large crack in Larsen's ice for more than a decade.

The rift's propagation had accelerated since 2014, making an imminent calving ever more likely.

The more than 200m-thick tabular berg will not move very far, very fast in the short term. But it will need to be monitored. Currents and winds might eventually push it north of the Antarctic where it could become a hazard to shipping.

An infrared sensor on the American space agency's Aqua satellite spied clear water in the rift between the shelf and the berg on Wednesday. The water is warmer relative to the surrounding ice and air - both of which are sub-zero.

"The rift was barely visible in these data in recent weeks, but the signature is so clear now that it must have opened considerably along its whole length," explained Prof Adrian Luckman, whose Project Midas at Swansea University has followed the berg's evolution most closely.

The event was confirmed by other spacecraft such as Europe's Sentinel-1 satellite-radar system.

Image copyright Copernicus Sentinel (2017) ESA/Andrew Flemming Image caption Europe's Sentinel-1 satellite-radar system confirmed the calving event

How does it compare with past bergs?

The new Larsen berg is probably in the top 10 biggest ever recorded.

The largest observed in the satellite era was an object called B-15. It came away from the Ross Ice Shelf in 2000 and measured some 11,000 sq km. Six years later, fragments of this super-berg still persisted and passed by New Zealand.

In 1956, it was reported that a US Navy icebreaker had encountered an object of roughly 32,000 sq km. That is bigger than Belgium. Unfortunately, there were no satellites at the time to follow up and verify the observation.

It has been known also for the Larsen C Ice Shelf itself to spawn bigger bergs. An object measuring some 9,000 sq km came away in 1986. Many of Larsen's progeny can get wound up in a gyre in the Weddell sea or can be despatched north on currents into the Southern Ocean, and even into the South Atlantic.

A good number of bergs from this sector can end up being caught on the shallow continental shelf around the British overseas territory of South Georgia where they gradually wither away.

Media playback is unsupported on your device Media caption Helen Fricker: "Iceberg calving is the natural background mass-loss process"

What is the significance of the calving?

In and of itself, probably very little. The Larsen C shelf is a mass of floating ice formed by glaciers that have flowed down off the eastern side of the Antarctic Peninsula into the ocean. On entering the water, their buoyant fronts lift up and join together to make a single protrusion.

The calving of bergs at the forward edge of the shelf is a very natural behaviour. The shelf likes to maintain an equilibrium and the ejection of bergs is one way it balances the accumulation of mass from snowfall and the input of more ice from the feeding glaciers on land.

Media playback is unsupported on your device Media caption File footage from the British Antarctic Survey showed the crack developing

That said, scientists think Larsen C is now at its smallest extent since the end of the last ice age some 11,700 years ago, and about 10 other shelves further to the north along the Peninsula have either collapsed or greatly retreated in recent decades.

The two nearby, smaller shelves, Larsen A and Larsen B, disintegrated around the turn of the century; and a warming climate very probably had a role in their demise.

But Larsen C today does not look like its siblings. Prof Helen Fricker, from the Scripps Institution of Oceanography, told BBC News: "The signs we saw at Larsen A and B - we're not seeing yet. The thinning we saw for Larsen A and B - we're not seeing. And we're not seeing any evidence for large volumes of surface meltwater on the order of what you would need to hydro-fracture the ice shelf.

"Most glaciologists are not particularly alarmed by what's going on at Larsen C, yet. It's business as usual."

Researchers will be looking to see how the shelf responds in the coming years, to see how well it maintains a stable configuration, and if its calving rate changes.

There was some keen interest a while back when the crack, which spread across the shelf from a pinning point known as the Gipps Ice Rise, looked as though it might sweep around behind another such anchor called the Bawden Ice Rise. Had that happened, it could have prompted a significant speed-up in the shelf's seaward movement once the berg came off.

As it is, scientists are not now expecting a big change in the speed of the ice.

One fascinating focus for future study will be a strip of "warm", malleable ice that runs east-west through the shelf, reaching the ocean edge about 100km north from the Gipps Ice Rise. This strip is referred to as the Joerg suture zone. There is a large queue of cracks held behind it.

"Calving of the iceberg is not likely itself to make the existing cracks at the Joerg Peninsula suture zone more likely to jump across this boundary," observed Chris Borstad, from the University Centre in Svalbard (UNIS).

"At this stage we really don't know whether there is some larger-scale process that might be weakening this zone, like ocean melting at the base of the shelf, or whether the current rift was just a random or episodic event that was bound to happen at some point.

"We know that rifts like this periodically propagate and cause large tabular icebergs to break from ice shelves, even in the absence of any climate-driven changes.

"I am working with a number of colleagues to design field experiments on Larsen C to answer this specific question (by measuring the properties of the Joerg suture zone directly). But until we get down there and take some more measurements we can only speculate."

Image copyright Copernicus/Sentinel Data Image caption Scientists want to understand why a lot of cracks seem not to propagate across the ice shelf

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos</s>A huge iceberg more than a quarter of the size of Wales has broken off an ice shelf in Antarctica.

The dramatic loss of the block could trigger the rapid collapse of the whole shelf and cause sea levels to rise, experts said.

Scientists at the British Antarctic Survey (BAS) will now study the stability of Larsen C Ice Shelf and how its newly exposed ocean and seabed areas are populated with life.

A BAS spokesman said the iceberg had been “hanging by a thread” for months.

It formed more than 10% of the shelf at more than 6,000 km² in area and 30m of the 190m-thick block is now above sea-level.

Director of Science Professor David Vaughan said the collapse of nearby ice shelves had “resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise.

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

“There is little doubt that climate change is causing ice shelves to disappear in some parts of Antarctica at the moment.

“We see no obvious signal that climate warming is causing the whole of Antarctica to break up. However, around the Antarctic Peninsula, where we saw several decades of warming through the latter half of the 20th century, we have seen these ice shelves collapsing and ice loss increasing.

“Larsen C itself might be a result of climate change, but, in other ice shelves we see cracks forming, which we don’t believe have any connection to climate change.”

Researchers from BAS and the University of Swansea, who used satellite imagery to monitor a 170km rift in the shelf on daily basis, reported the iceberg had fully detached at 8am yesterday (wed).

The newly exposed ocean and underlying seabed have been put forward to be made into a internationally-recognised Special Area for Scientific Research.

Dr Phil Trathan, Head of Conservation Biology said: “If designated, this would restrict commercial fishing activities and provide a valuable opportunity for studying the new habitats created, including how species colonize the area and new communities develop.”

Remote sensing analyst Andrew Fleming, said: “Our glaciologists will now be watching closely to see whether the remaining Larsen C Ice Shelf becomes less stable than before the iceberg broke free, and our biologists will be keen to understand how new habitats formed by the loss of the ice are colonised.”

Conservation biologists said the “calving event” followed the collapse of ice shelves Larsen A and Larsen B further north in the continent in 1995 and 2002.

A BAS spokesman said it “will provide unique scientific opportunities for understanding how new biological communities develop and how new species occupy the newly exposed area.”</s>One of the largest icebergs on record has broken away from an ice shelf in Antarctica, scientists have announced.

A huge crack in the Larsen C Ice Shelf had left a vast iceberg weighing more than a trillion tonnes "hanging by a thread".

But now the rift has finally completed its path through the ice, researchers monitoring the berg have said.

The 5,800 square kilometre (2,200 square mile) mass has now calved, the team from the Swansea University-led Midas project said.

Data from Nasa's Aqua MODIS satellite detected the final breakthrough between Monday and Wednesday.

The calving of the iceberg, which is likely to be named A68, reduces the size of the Larsen C Ice Shelf by around 12% and will change the landscape of the Antarctic Peninsula forever, the scientists said.

Professor Adrian Luckman of Swansea University, lead investigator of the Midas project, 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."

Although the iceberg weighs a trillion tonnes, it was already floating before it calved away so will have no immediate impact on sea level.

While the researchers said the calving was a "natural event", it put the ice shelf in a vulnerable position.

There are concerns that Larsen C could follow the example of its neighbouring ice shelf Larsen B, which disintegrated in 2002 after a similar event.

If the shelf loses much more area, it could result in glaciers which flow off the land behind speeding up their path to the ocean, which could have an eventual impact on sea levels - though at a very modest rate, the scientists said.</s>A massive iceberg weighing more than one trillion tons has broken away from western Antarctica, according to a UK-based research team.

Scientists from Project MIDAS had been monitoring a break in the Larsen C ice shelf — the fourth largest in Antarctica — following the collapse of the Larsen A ice shelf in 1995 and had observed significant advances in the rift over the past 12 months.

Experts said the separation of a 5,800 square km section of Larsen C was confirmed to have broken away between Monday and Wednesday by NASA’s Aqua MODIS satellite, which is capable of producing images in thermal infrared at a resolution of 1 km.

“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 kilometers of ice,” Professor Adrian Luckman of Swansea University, lead investigator of the MIDAS project said in a statement.

He told CNN the team believes the iceberg has remained intact adding, “This is part of the normal behavior of ice shelves. What makes this unusual is the size.”

Scientists believe the iceberg — likely to be named A68 — has a volume twice that of Lake Erie, one of the Great Lakes in the United States.

With the iceberg now floating independently, the area of Larsen C has been reduced by more than 12%, forever changing the landscape of the peninsula, according to experts.

Luckman said that as the sheet of ice was already floating before it carved off the shelf “there will be no immediate impact”.

“We will study the ice shelf for signs that it is reacting to the calving — but we do not expect anything much to happen for perhaps years. Icebergs are routinely monitored by various agencies, and they will be keen to keep track of this one,” Luckman added.

Calving is a natural occurrence but scientists have been exploring if climate change may have played a role in expediting the rift.

The team of researchers have not yet found “any link to human-induced climate change”, Martin O’Leary, a Swansea University glaciologist and member of the MIDAS project team, said in a statement.

Luckman added: “We have no evidence to link this directly to climate change, and no reason to believe that it would not have happened without the extra warming that human activity has caused. But the ice shelf is now at its most retreated position ever recorded and regional warming may have played a part in that.”</s>A trillion-tonne iceberg - one of the largest on record - has broken away from an ice shelf in Antarctica.

Researchers have been monitoring a huge crack in the Larsen C Ice Shelf, which had left a vast iceberg more than four times the size of London or a quarter the size of Wales "hanging by a thread".

Scientists announced on Wednesday that the rift had finally completed its path through the ice, causing the 2,200 square mile (5,800 square kilometre) iceberg to snap off.

The calving of the iceberg reduces the size of the Larsen C Ice Shelf by around 12 per cent and will change the landscape of the Antarctic Peninsula forever, the team from the Swansea University-led Midas project said.</s>A massive iceberg the size of Delaware has broken free from Antarctica and is floating in the sea.

Earlier Wednesday, scientists announced that the 6,000-square-kilometer (about 2,300 square miles) iceberg had come loose, after satellites detected it had calved off the Larsen C ice shelf on the Antarctic Peninsula.

"Put any adjective you like on it: a corker, a whopper — it's a really large iceberg," says Anna Hogg, a researcher with the United Kingdom's Centre for Polar Observation and Modelling at the University of Leeds.

"There have been some this big before," says Adrian Luckman, a glaciologist at Swansea University in the U.K. who leads a project to track changes in the ice shelf. But he adds, the roughly trillion-metric-ton iceberg is unusual. "This is certainly in the Top 10, maybe possibly in the Top 5."

Scientists had anticipated the breakup since a massive crack first opened up in the Larsen C ice shelf back in 2014. The crack grew rapidly, and by the end of last week, a roughly 3-mile sliver of ice was all that connected the iceberg to the shelf.

Hogg says that the breakup, while astounding in size, will not have an effect on global sea levels. That is because this chunk of ice was already floating on water when it broke off. "This is the same as if you've got an ice cube in your gin and tonic," she says. "When the ice cube melts, it doesn't raise the volume of water in that glass."

But the consequences could be significant. The larger Larsen C ice shelf is itself holding back a large volume of "grounded ice." If the entire ice shelf breaks apart, that grounded ice could flow into the ocean, changing sea levels, Hogg says.

Luckman, however, says there is no need for panic: The breakup of the ice shelf, if it happens at all, will take years or even decades. Even then it's unclear how much ice would flow into the sea.

Nor is it clear whether climate change is behind this breakup. Although climate change has been responsible for melting in other parts of Antarctica, such as the Pine Island Glacier, researchers believe the story on the Antarctic Peninsula is more complicated. "Icebergs are calving all the time in Antarctica, and really that forms part of the natural life cycle of any ice shelf," Hogg says.

Researchers will have to continue their studies to find out whether Larsen C is being affected by climate change.</s>One of the biggest ever icebergs has been recorded breaking away from Antarctica.

The 6,000 sq km iceberg, with a likely weight of one trillion tonnes, split from the Larsen C Ice Shelf at some point between 10 and 12 July, scientists say.</s>A massive iceberg weighing more than one trillion tons has broken away from western Antarctica, according to a UK-based research team.

Scientists from Project MIDAS had been monitoring a break in the Larsen C ice shelf — the fourth largest in Antarctica — following the collapse of the Larsen A ice shelf in 1995 and had observed significant advances in the rift over the past 12 months.

Experts said the separation of a 5,800 square kilometers (2,239 square miles) section of Larsen C was confirmed to have broken away between Monday and Wednesday by NASA’s Aqua MODIS satellite, which is capable of producing images in thermal infrared at a resolution of 1 km.

“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 kilometers of ice,” Professor Adrian Luckman of Swansea University, lead investigator of the MIDAS project said in a statement.

He told CNN the team believes the iceberg has remained intact adding, “This is part of the normal behavior of ice shelves. What makes this unusual is the size.”

Scientists believe the iceberg — likely to be named A68 — has a volume twice that of Lake Erie in North America and is more than three times the size of the greater London area.

It’s half the size of the largest iceberg ever recorded: B15. With an area of 11,007 square kilometers (4,250 square miles) — about the size of the state of Connecticut or the island of Jamaica — it calved off Antarctica’s Ross Ice Shelf in March 2000.

With the iceberg now floating independently, the area of Larsen C has been reduced by more than 12%, forever changing the landscape of the peninsula, according to experts.

Luckman said that as the sheet of ice was already floating before it carved off the shelf “there will be no immediate impact.”

“This event does not directly affect anyone, and repercussions, if there are any, will not be felt for years. However, it is a spectacular and enormous geographical event which has changed the landscape.”

“We will study the ice shelf for signs that it is reacting to the calving — but we do not expect anything much to happen for perhaps years. Icebergs are routinely monitored by various agencies, and they will be keen to keep track of this one,” Luckman added.

Calving is a natural occurrence but scientists have been exploring if climate change may have played a role in expediting the rift.

The team of researchers have not yet found “any link to human-induced climate change,” Martin O’Leary, a Swansea University glaciologist and member of the MIDAS project team, said in a statement.

Luckman added, “We have no evidence to link this directly to climate change, and no reason to believe that it would not have happened without the extra warming that human activity has caused. But the ice shelf is now at its most retreated position ever recorded and regional warming may have played a part in that.”

He continued, “This event does not directly affect anyone, and repercussions, if there are any, will not be felt for years. However, it is a spectacular and enormous geographical event which has changed the landscape</s>FILE PHOTO: An aerial view of the rift in the Larsen C seen in an image from the Digital Mapping System over the Antarctica Peninsula, Antarctica, on November 10, 2016. NASA's Goddard Space Flight Center/Handout via REUTERS

LONDON (Reuters) - One of the biggest icebergs on record has broken away from Antarctica, scientists said on Wednesday, creating an extra hazard for ships around the continent as it breaks up.

The one trillion tonne iceberg, measuring 5,800 square km, calved away from the Larsen C Ice Shelf in Antarctica sometime between July 10 and 12, said scientists at the University of Swansea and the British Antarctic Survey.

The iceberg has been close to breaking off for a few months. Throughout the Antarctic winter, scientists monitored the progress of the rift in the ice shelf using the European Space Agency satellites.

"The iceberg is one of the largest recorded and its future progress is difficult to predict," said Adrian Luckman, professor at Swansea University and lead investigator of Project MIDAS, which has been monitoring the ice shelf for years.

"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," he added.

The ice will add to risks for ships now it has broken off. The peninsula is outside major trade routes but the main destination for cruise ships visiting from South America.

In 2009, more than 150 passengers and crew were evacuated after the MTV Explorer sank after striking an iceberg off the Antarctic peninsula.

The iceberg, which is likely to be named A68, was already floating before it broke away so there is no immediate impact on sea levels, but the calving has left the Larsen C ice shelf reduced in area by more than 12 percent.

The Larsen A and B ice shelves, which were situated further north on the Antarctic Peninsula, collapsed in 1995 and 2002, respectively.

"This resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise," said David Vaughan, glaciologist and director of science at British Antarctic Survey.

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

Big icebergs break off Antarctica naturally, meaning scientists are not linking the rift to manmade climate change. The ice, however, is a part of the Antarctic peninsula that has warmed fast in recent decades.

"In the ensuing months and years, the ice shelf could either gradually regrow, or may suffer further calving events which may eventually lead to collapse – opinions in the scientific community are divided," Luckman said.

"Our models say it will be less stable, but any future collapse remains years or decades away."</s>A part of the ice sheet thought to be a quarter of the size of Wales has broken off from west Antarctica.

An ominous crack has been working its way across the Larsen C ice sheet for a distance of 120 miles. Scientists have been monitoring it closely for several years, and now it seems that it has finally broken off.

It's not yet known whether the ice is in one piece – which could make it one of the largest ever icebergs – or if it has splintered into many fragments. Data from before the calving event suggests that it may not have been a "clean break", scientists from Project MIDAS announced on twitter.

Observations on the 24 and 27 June suggested that a break was imminent.

"The speed of the ice has really picked up. We don't know why, but it is probably the combined effect of wind and tide," Adrian Luckman of MIDAS told IBTimes UK at the time.

The calving event was "unusually large", and will leave the Larsen C ice shelf at its smallest size ever recorded. Iceberg calving is an ordinary part of the life cycle of ice in Antarctica, as ice flowing from the mainland pushes the sheet out into the warmer ocean, where it eventually breaks off.

However, the speed at which sea ice is being lost across the polar regions – particularly Greenland – is being accelerated by climate change, which is directly related to the carbon emissions from human activities.

The vast majority of the planet's fresh water is locked up in the ice of Antarctica. As the ice sheets begin to melt, sea levels are set to rise. However, the consequences of this iceberg calving event alone will not be dramatic.

"There will be no immediate sea level rise – the iceberg is already afloat. There may follow a long – years, decades – period of further slow decay.

"Even if the ice shelf disappears completely, and its feeding glaciers are able to flow faster, the sea level rise contribution from this part of Antarctica is very small – centimeters over decades," said Luckman.

In the wake of the break-off, scientists from the British Antarctic Survey, who collaborated with the MIDAS team, said that the event could change the local environment significantly.

"This story has just got even more interesting. Our glaciologists will now be watching closely to see whether the remaining Larsen C Ice Shelf becomes less stable than before the iceberg broke free, and our biologists will be keen to understand how new habitats formed by the loss of the ice are colonised," said BAS remote sensing analyst Andrew Fleming.

Professor David Vaughan, glaciologist and director of science at BAS, added:

"Larsen A and B ice shelves, which were situated further north on the Antarctic Peninsula, collapsed in 1995 and 2002, respectively. This resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise. If Larsen C now starts to retreat significantly and eventually collapses, then we will see another contribution to sea level rise."
A giant iceberg covering approximately 6,000 square kilometres (2,300 sq mi) breaks away from the Larsen C Ice Shelf in Antarctica.