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> 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> 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> 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 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> 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 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 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> Early next year, an international team of explorers will investigate the area in-and-around the massive iceberg that split away from Antarctica’s Larsen C ice shelf in July 2017. As an added bonus, the researchers will also attempt to locate the wreck of the Endurance, which sunk in 1915 as part of the ill-fated Shackleton expedition.



Led by the University of Cambridge’s Scott Polar Research Institute (SPRI), and funded by the Flotilla Foundation—a Netherlands-based charitable trust—the Antarctic Weddell Sea Expedition is scheduled to take place from January to February 2019, as reported by the BBC. Using the icebreaking polar supply and research vessel SA Agulhas II, the 45-day mission will truly be an international effort, involving researchers from the UK, the US, New Zealand, and South Africa.

The primary goal of the mission will be to explore Iceberg A-68, which calved from Antarctica’s Larsen C Ice Shelf on July 12, 2017. The astoundingly huge berg features a surface area of 2,240 square miles (5,800 square kilometers), which is about the size of Delaware or about four times the size of London.



It just so happens, however, that the wreck of the Endurance—a historic three-mast ship that went down on November 21, 1915—is located nearby, some 115 to 175 miles (185 to 280 km) from the location of Iceberg A-68. Pending favorable weather and ocean conditions, the researchers will use the opportunity to search for the ill-fated ship, which rests at a depth of nearly two miles.

After drifting in the Weddell Sea ice for months, the Endurance was eventually crushed by encroaching ice. The ship had to be abandoned, with the crew of 28 escaping aboard three lifeboats. The survivors spent the next five months on Antarctica’s ice floes, eventually reaching Elephant Island. Expedition leader Ernest Shackleton, along with five others, set off for South Georgia Island—located 920 miles away—while the remaining crew waited. It wouldn’t be until August 1916 that everyone was rescued.

Next year, the Weddell Sea Expedition will travel to the last known position of the ship and conduct a search using Remotely Operated Vehicles (ROVs) provided by US company Ocean Infinity. “They are fitted with downward-looking multi-beam echosounders, which can map out on a grid the shape of the seafloor,” Julian Dowdeswell, who will lead the team, told the BBC. “You look at that for any signs of the ship and then focus in with cameras if you find something interesting.”

The researchers will also have the diary of Captain Frank Worsley at their disposal, who kept meticulous records of the Endurance’s position. The ship’s final coordinates were listed at 68°39'30.0" South and 52°26'30.0" West. Despite this knowledge, however, three prior attempts to find the ship have failed. Should the ship be located, it will be listed as a historic monument and protected by international law.

“If the expedition finds the wreck we will survey, photograph, and film it and document its condition,” Dowdeswell told The Telegraph. “If there are deep-water marine species colonizing the wreck, the marine biologists may try to obtain scientific samples using the [ROVs], if that can be deployed above the site from the ship,” adding “we will not remove any items from the wreck.”

At the Larsen C Ice Shelf, the ROVs will explore the cavity under the newly exposed shelf, map the seafloor, and investigate the overhanging ice canopy. Researchers on board the ship will extract samples of ice from the shelf, which they can read like tree rings to see the ebbs and flows of the ice over time.

But it won’t be easy. Earlier this year, a mission to the Larsen C Ice Shelf had to be canceled owing to treacherous conditions. It’s been over a century since the Endurance sunk, but Antarctica is still a very dangerous place.
A giant iceberg covering approximately 6,000 square kilometres (2,300 sq mi) breaks away from the Larsen C Ice Shelf in Antarctica.