Larson C ice-shelf break-away is not human-caused but Guardian tries hard to imply otherwise

A couple of days ago the BBC had an article Giant iceberg splits from Antarctic.

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.

After looking at various evidence the BBC concludes

“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.

That is the theory about a link with accelerating global warming is no longer held due to lack of evidence. But the Guardian sees things differently.

Unlike thin layers of sea ice, ice shelves are floating masses of ice, hundreds of metres thick, which are attached to huge, grounded ice sheets. These ice shelves act like buttresses, holding back and slowing down the movement into the sea of the glaciers that feed them.

“There is enough ice in Antarctica that if it all melted, or even just flowed into the ocean, sea levels [would] rise by 60 metres,” said Martin Siegert, professor of geosciences at Imperial College London and co-director of the Grantham Institute for Climate Change & Environment. 

Despite the lack of evidence for the hypothesis about accelerating ice loss due to glaciers slipping into the sea the Guardian still quotes the unsupported hypothesis. Then the article has a quote from someone who seems to extend the hypothesis to the entire continent. Inspection of their useful map of the location of Larson C might have been helpful.

Larsen C is located mid-way up the Antarctic Peninsula, which comprises around 2% of the area of Antarctica. The Peninsula has seen some rapid warming, quite unlike East Antarctica where very little warming has been detected. That is the Antarctic Peninsula is climatically different from the vast majority of the continent, where nearly all of the ice mass is located.

The article the goes on to contradict the implication with climate change, so the quote is out of context.

Andrew Shepherd, professor of Earth Observation at the University of Leeds, agreed. “Everyone loves a good iceberg, and this one is a corker,” he said. “But despite keeping us waiting for so long, I’m pretty sure that Antarctica won’t be shedding a tear when it’s gone because the continent loses plenty of its ice this way each year, and so it’s really just business as usual!”

However, the Guardian then slips in another out of context quote at the end of the article.

The news of the giant iceberg comes after US president Donald Trump announced that the US will be withdrawing from the 2015 Paris climate accord – an agreement signed by more than 190 countries to tackle global warming. 

Another quote from the BBC article helps give more perspective.

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.

Bigger events have happened in the past. It is only due to recent technologies that we are able to measure the break-up of ice shelves, or even to observe icebergs the size of small countries.

Note that the Guardian graphic is sourced from Swansea University. Bloomberg has a quote that puts the record straight.

Although this is a natural event, and we’re not aware of any link to human-induced climate change,” said Martin O’Leary, a glaciologist at Swansea University, in a statement.

Kevin Marshall