Environment

Giant iceberg could wipe out Adélie penguin colony at Cape Denison, Antarctica

Up to 150,000 Adélie penguins seem to have disappeared from a single colony in Antarctica after the grounding of a giant iceberg.

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New research by UNSW's Climate Change Research Centre reveals the staggering decline of Adelie penguin numbers at Cape Denison in Antarctica, following the grounding of a 97km iceberg in Commonwealth Bay.

The penguins used to thrive at Cape Denison in Commonwealth Bay, where strong winds blowing off the ice sheet kept a large area of water open near the shore.  

But in December 2010 an iceberg bigger than the ACT grounded in the bay, trapping floating sea ice near the coast. The penguins now have to make a round trip of more than 120km to feed in the sea and since 2011 the population has plummeted from 160,000 to just 10,000. 

According to new research co-authored by the University of NSW's Climate Change Research Centre and published in the journal Antarctic Science, the colony could be wiped out within 20 years unless the sea ice breaks up or the iceberg, with an area of about 2900 square kilometres, moves. 

The penguins were counted as part of the Australasian Antarctic Expedition 2013-14, led by Professor of Climate Change and Earth Sciences at UNSW, Chris Turney. 

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Professor Turney said penguin numbers had been recorded for 100 years at Cape Denison, where explorer Sir Douglas Mawson's research station was based in 1911-14. Members of that expedition complained of the noise generated by 100,000 inquisitive Adélie penguins.

"It's eerily silent now," Professor Turney said. "The ones that we saw at Cape Denison were incredibly docile, lethargic, almost unaware of your existence. The ones that are surviving are clearly struggling. They can barely survive themselves, let alone hatch the next generation. We saw lots of dead birds on the ground ... it's just heartbreaking to see."

Lead author Dr Kerry-Jayne Wilson, of the West Coast Penguin Trust, said regional changes triggered by the iceberg had led to a "catastrophic breeding failure". She said it was "heart wrenching" to see the impact on the penguins, with researchers walking "amongst thousands of freeze-dried chicks from the previous season and hundreds of abandoned eggs".

In contrast, an Adélie colony in a different part of Commonwealth Bay, just eight kilometres from the edge of the sea ice, was thriving.

Known as B09B, the 97-kilometre long iceberg had moved around the Antarctic coast for 20 years before crashing into a glacier then grounding in Commonwealth Bay. 

"Iceberg doesn't really do it justice," Professor Turney said. "It's like a small country, it's enormous.

"As the planet warms you're going to get more ice melting. The reality is, more icebergs will be released from Antarctica and just embed themselves along the coastline, and make the travelling distances for some of these colonies even further than they have been." 

Adélie penguins usually return to the colony where they hatched and try to return to the same mate and nest. Professor Turney said the Cape Denison penguins could face a grim future. "They don't migrate," he said. "They're stuck there. They're dying."

Co-author Chris Fogwill, of the UNSW Climate Change Research Centre, said there was some good news for the colony. "Over the last year the fast ice associated with B09B has begun to break up in Commonwealth Bay," he said. 

The effects of the recent changes on the ecosystems in and around Commonwealth Bay "will help us better understand the impacts of such large-scale events on the fragile Antarctic ecosystem", he said.

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