Two penguins
Two penguins dreaming sitting on a rock, mountains in the background

For baby Adélie penguins on Ross Island in Antarctica, this summer looks bleak. For the second time in four years, sea ice has hemmed in their parents’ route to the sea, making for a very lean few months for the baby penguins and a likely death for many.

“If the sea ice conditions stay as they are, there will be little or no breeding success at (Cape) Royds and limited breeding success at (Cape) Bird, but round the corner at (Cape) Crozier it should be okay,” says John Cockrem, a Massey University scientist who studies penguins and who has just returned from the Antarctic.

Stopping the ice from dissipating up is a breakwater in the shape of a huge iceberg, B15A, a remnant of an even bigger iceberg that split away from the Ross ice shelf in 2000. When that first iceberg, B15, formed, it was the biggest ever recorded. Even its subset, B15A, is more than 3,000-square kilometers.

The sea ice that remains in McMurdo Sound means that adult penguins have to walk up to 100 kilometers over sea ice to reach the sea and food. Many of the parents will either abandon their eggs in order to feed themselves or won’t come back with enough food to keep their chicks alive.

But Cockrem says that while the sea ice is a “big problem” for some of the Ross Island Adélie penguins, it is not a problem for the overall Adélie species, the most populous of all penguins.

He says that just over two per cent of the breeding population, or 50,000 or so breeding pairs, will be affected by the sea ice. In total there are 5 million breeding Adélie adults and an equal number of juvenile birds. The rookery at Cape Royds, next to where explorer Ernest Shackleton made his Ross Island home, has a mere 3,000 to 4,000 breeding pairs. “So, if the Royds rookery disappears, then it would be a nuisance for visitors but it’s not a problem for the population as a whole,” says Cockrem.

Around the corner at Cape Crozier, home to the largest of all penguins, the Emperor penguins, the news is better. This year the Emperor penguins have raised about 420 chicks this year.

“This is the first season since 2001 that they have been successful. The fact that B15A has moved a bit to the north, thus, freeing up some foraging habitat close by should help as well,” says David Ainley, a US penguin specialist currently in Antarctica. Adélie penguins at Cape Crozier were also “doing better than they have in the past few years,” Ainley says.

In fact, the B15A iceberg is more of a potential nuisance to humans as it may possibly prevent the annual resupply of the two Ross Island stations, New Zealand’s Scott Base and the US’s McMurdo Base. The sea ice in front of McMurdo Station and Scott Base has not melted away since 1999 and is now more than twice its usual thickness. Icebreakers usually break a 50-kilometre channel into McMurdo; this year they are faced with about 190 kilometers of thick sea ice to break.

The B15A iceberg is now heading north towards Drygalski ice tongue, a part of a glacier that floats out over the Ross Sea. According to McMurdo Station’s newspaper, the Antarctic Sun, if B15A moves between a gap one of the islands and nearby shoals it could keep moving north right up to the ice tongue and effectively block off the opening to McMurdo Sound.

Or it could possibly hit the ice tongue — the iceberg is about 17 kilometers away and moving at a speed of one to two kilometers a day. “If it does actually hit the Drygalski ice tongue,” says Cockrem, “it might break off the ice tongue which will be very spectacular.”

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