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14 July 2017

Iceberg Finally Breaks Away from Larsen C Ice Shelf

Img: BBC News

It’s finally happened.

After reporting just three days ago that an iceberg ¼ the size of Wales was set to break off from the Larsen C Ice Shelf, the calving was witnessed yesterday by a US satellite passing overhead. An infrared sensor picked up a line of clear water where the rift had been, with the temperature of the water marginally warmer than the sub-zero temperature of the ice.

This event was over a decade in the making, with scientists having monitored the region for years as fears grew over how this would impact a world constantly under threat from a changing climate.
In its current state, the iceberg isn’t expected to travel particularly fast and will therefore take a while to cover much distance, however that doesn’t mean that it won’t still pose a threat in the future. No longer a part of the ice shelf, it’s now exposed to the effects of winds and currents that could push it towards shipping areas north of the Antarctic. Many bergs that have broken away from the Larsen shelves in the past have ended up in a gyre – a circulating ocean current – in the Weddell Sea or become trapped on the shallow continental shelf around South Georgia.

The Larsen iceberg is one of the ten biggest ever recorded, measuring over half of the size of the largest that’s been observed since satellite data became available. This was the B-15, an 11,000 sq km iceberg that parted from the Ross Ice Shelf back in 2000. Supposedly, a berg amassing an area of 32,000 sq km was once observed by a US Navy Icebreaker back in 1956; however without satellites to back this up, it’s uncertain whether this was actually the case.

While the parting of this iceberg from the Larsen C Ice Shelf isn’t necessarily anything of major significance – calving is a natural process that maintains an equilibrium as the shelf accumulates snow and glacial ice – it is yet another incident of climate change impacting the Antarctic. Larsen C is at its smallest extent since the last ice age ended and around 10 shelves nearby have all retreated or collapsed in recent years, with global warming acting as a contributing factor. It’s imperative for researchers to watch how the shelf acts now that the calving has happened, to see whether or not it can remain stable.

Scientists are hopeful, though.

Img: BBC News

Professor Helen Fricker from the Scripps Institution of Oceanography told BBC News that Larsen C is in a much better position than Larsen A and B were in when they disintegrated at the start of the century.
“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.”
As for the reason that the crack originated in the first place, Chris Borstad from the University Centre in Svalbard says they can’t confirm anything with any certainty.

“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.”

If there any developments in either the Larsen C Ice Shelf or the newly departed iceberg we will be sure to let you know.
James Darvill

James is a passionate scriptwriter and reluctant poet with a talent for the dystopian. When he’s not staying up late watching the Simpsons he’s beating the world at Mario Kart, always with a glass of wine in hand.