The study by the British Antarctic Survey found that record low sea ice levels in 2023 contributed to the second worst year for emperor penguin chick mortality since observations began in 2018.

It follows a “catastrophic breeding failure” in 2022, signalling long-term implications for the population, the study’s author Peter Fretwell told AFP.

Emperor penguins breed on sea ice platforms, with chicks hatching in the winter between late July and mid-August.

The chicks are reared until they develop waterproof feathers, typically in December ahead of the summer melt.

But if the ice melts too early, the chicks risk drowning and freezing.

Fourteen of 66 penguin colonies, which can each produce several hundred to several thousand chicks in a year, were affected by early sea-ice loss in 2023, said the study published in the Journal of Antarctic Science.

The result is “high if not total levels of mortality”, Fretwell said.

Yet 2023 “wasn’t as bad as we feared”, he said. A record 19 colonies were affected the year before.

The study also found that several colonies, particularly those ravaged the previous year, had moved in search of better conditions onto icebergs, ice shelves or more stable sea ice.