Why the Antarctic ice shelf broke apart and what it means

Sometime over the past few days, a 6,000-square-kilometre piece of ice broke off Antarctica and began its journey into open waters.

This new iceberg — some 200 square kilometres larger than P.E.I — is one of the largest in recorded history to break off the continent.

It represents more than 10 per cent of the entire Larsen C ice shelf, said Christopher Shuman, a NASA research scientist and professor of glaciology at the University of Maryland. 

And while there is a lot of talk about how climate change is affecting the poles, the calving, or breaking off, of parts of ice shelves can't be directly linked to warming temperatures, as it's something that's been seen throughout recorded history.

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"We just can't make a clear connection to this being driven by climate change at this time," Shuman said. "This is a worrisome sign for the Larsen C: you can't lose 12 or 13 per cent of your area from an ice shelf and not think, 'Hmm. Well, that's an awful lot that's gone missing.' On the other hand, there have been previous large bergs from this area."

Still, this calving event occurred in an area of the Antarctic that has experienced a warming trend since the 1950s.

"There have been large increases in temperature in this region over the last half-century or so," said Martin O'Leary, a research scientist and glaciologist at Swansea University. "Obviously we have been seeing climate change impacts, and it's possible that this is going to put the ice shelf in a much more vulnerable position."

Why it broke apart

Ice shelves form when ice sheets on land make their way to the coast and slide into the surrounding ocean or sea. If the water and the air are cold enough, the ice remains and grows on the surface of the water, with the air in the ice keeping it afloat.

But there are various forces — including weather — acting upon the ice that stretches into the ocean. They can cause it to stress and fracture, leading to calving.

The iceberg — about 6,000 square kilometres — broke away from the Larsen C ice shelf as part of the natural cycle of calving. It is shown in this satellite image released by the European Space Agency on Wednesday. (ESA/Handout via Reuters)

"There's this huge thing that's floating in the ocean that's being pushed and pulled by the forces that every boater knows about … This is a difficult circumstance for this ice to be comfortable in," Shuman said. "And that's what caused the rift to gradually grow … over time."

Though it happens from time to time, a break this large is unusual.

Consequences of calving

A bit of good news is that the calving of the Larsen C ice shelf, creating this new iceberg, won't contribute to rising sea levels as the ice was already floating in the water.

But scientists will definitely be keeping an eye on what happens to the remaining 40,000 square kilometres of the Larsen C ice shelf.

Antarctica is home to several ice shelves, with some of the biggest highlighted here. (NSIDC)

"Yes, this is an unusual event. Yes, the Larsen C will have retreated farther west than we've ever known it to have retreated before," Shuman said. "On the other hand, it has dropped large [bergs] before."

As for whether this could result in more inland ice sheets making their way to the ocean, ultimately leading to ocean rise, Shuman said that should remain stable right now, because so much of the ice shelf is left.

However, if they see the region's slow-moving glaciers start to speed up, things could change in years to come. And if they see the shelf pulling away from the ice that's holding it where it is, that could add to the chance of the Larsen C collapsing entirely. If that happens, there would be a rise in sea levels. 

"But at the moment, we don't think it'll have a dramatic impact on this ice in the Antarctic Peninsula," Shuman said.

Lifespan of the iceberg

The massive iceberg that's now floating along in the Southern Ocean, off the coast of Antarctica, will likely break up over time, Shuman said. Currents will take it on a north-northeast arc, pushing it toward the South Georgia and Sandwich Islands, just as others before it.

When the Larsen C iceberg calves, where might it end up? Follow two large icebergs from the same region back in 2001/2002 courtesy of @BYU pic.twitter.com/XF2I9a7cN6

— @adrian_luckman

"It's very likely to break into pieces; exactly what those pieces will look like is too early to tell," Shuman said.

But it's unlikely to pose a threat to shipping in the area, Shuman said. "In this age of ready access to satellites and whatnot, and internet connection on sailboats, you'd have to be pretty unlucky to be surprised by this guy."

As for the lifespan of this new iceberg, it's likely to take years — perhaps five or more — before it finally disappears for good.