Previous instalments in this occasional series:

Iceberg	Calved	Notes
A68	August 2017	Reached South Georgia December 2020; broke up in February 2021; BAS (November 2020) says it might be stuck at South Georgia for 10 years; penguins in peril, according to the alarmist media
A38	October 1998	Reached South Georgia December 2003; broke up October 2004
A23 [See comments below A38 story.]	1986	Grounded in the shallows near South Georgia in March 2025; “Blocks off key penguin feeding ground.”

There was another giant iceberg, which is said to have killed penguins, and to have hung about for a decade. And that might make the reader think that the 10 year hype about A68 might have had some foundation. It didn’t.

The iceberg in question was given the terrifying name B9 when it split from the Ross Ice Shelf [160W, 79S] in October 1987. According to Keys et al (1990), its size was as follows: 154*35 km = 4540 km², maximum draught 250 m, freeboard 50 m, >1000 km³.

Two years later (August 1989), B9 broke into three pieces by Cape Adare. B9B was 100*35 km, and was the penguins’ nemesis.

B9B drifted anticlockwise along the Antarctic coast, and reached the Merz Glacier [145E, 67S] in February 2010. Still 90 km long, it knocked off a 70 km-long chunk of the Merz Glacier tongue.

It then drifted on a little further, breaking up, the pieces becoming lodged outside Commonwealth Bay [143E].

What about the poor penguins?

B9B did not cause the trouble directly, by parking in the way of the penguins. Rather, it blocked the anticlockwise flow of pack ice, which piled up and froze solid. Another factor may have been that the position of B9B meant that the usual very strong winds blowing seaward from Commonwealth Bay were no longer able to blow the ice away from shore. At any rate, the usually reliably open water was jammed up, and the Adelie penguins of Commonwealth Bay were imperilled. That’s because their usual brief slip-slide-skip-jump to open water from the nesting grounds suddenly became a marathon, even after B9B broke up into 3 large chunks.

In the southern summer of 2013-14, intrepid explorers arrived to assess the sitch. Readers of a climate-sceptical bent might recognise the term “Ship of Fools” – and indeed it was members of the ill-fated holiday, er, scientific expedition, who managed to get a day ashore to count penguins, just before their ship froze into the ice. [See Steve McIntyre’s timeline of the debacle.] The Commonwealth Bay penguins were observed on 20 December, and the Hodgeman Islands penguins [ice-free, and population unaffected] on the 23^rd, the very day the Ship of Fools got stuck.

The results of the surveys were reported in Wilson et al, which includes a thank you for the Guardian’s Alok Jha, who presumably carried a spotting scope ashore or something. They are not controversial, I think: naturally, the more onerous is your trip to reach open water to catch fish, the lower your fledging success is going to be.

By 2016, some iceberg fragments were still present (including the largest), but the bay was fairly open.

The larger of the three pieces of B9B is still close by in 2025, but it has been pushed offshore somewhat, and in this image, Commonwealth Bay is open, and the penguins are (presumably) happy again.

The impact of B9B on the Adelie penguins of Commonwealth Bay probably lasted half a decade. But there is a huge difference between a giant berg stuck in Commonwealth Bay, and stuck in the shallows by South Georgia. The former is much further south, and stuck in fast ice for large chunks of the year. The latter is open to wind and wave all the time. Yes, the water by South Georgia is cold – but not as cold as the water off Commonwealth Bay. In sum, there is the prospect that a drifting iceberg may get lodged in a position to offend penguins for a decade on the coast of the Antarctic continent itself – but no prospect of a similar occurrence off South Georgia. Note also that the problem with B9B was the way it backed up drifting ice and changed the usual system of polynyas. No such problem can possibly occur at South Georgia.

I might also note that such problems will have occurred since time immemorial, out of the eye of humans looking for something to alarm one another with.

What about A23, the berg now stuck in the shallows by South Georgia?

I took this snip of a satellite (Terra / Aqua again) pic on the very day Sky’s Science and Technology Editor made this pronouncement, so that readers can see just how much of the penguins’ feeding grounds are “blocked off” by “so-called A23a.” The polygon shown roughs out the shallow waters around South Georgia. ‘Nuff said?