Antarctic Sea Ice Loss Affects Emperor Penguin Breeding

Emperor penguin colonies in Antarctica with total sea ice loss failed to breed in 2022. This reinforces projections that over 90% of emperor penguin colonies will be quasi-extinct by the end of the century due to global warming.

British Antarctic Survey researchers reported today in Communications Earth & Environment that four of the five known emperor penguin colonies in the central and eastern Bellingshausen Sea were likely to have lost their chicks. The scientists investigated satellite photographs of sea ice melting at nesting areas before chicks developed waterproof feathers.

Emperor penguins depend on 'land-fast' sea ice from April to January. Penguins lay eggs in Antarctic winter from May to June at their breeding habitat. After 65 days, eggs hatch, but chicks don't fledge until summer, December–January.

Beginning in December 2022, the Antarctic sea ice extent matched the 2021 record low. The central and eastern Bellingshausen Sea region west of the Antarctic Peninsula lost 100% sea ice in November 2022.

Lead author of the study, Dr Peter Fretwell, said:
"We have never seen emperor penguins fail to breed, at this scale, in a single season. The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.

We know that emperor penguins are highly vulnerable in a warming climate -- and current scientific evidence suggests that extreme sea ice loss events like this will become more frequent and widespread."

Since 2016, Antarctica has had the four lowest sea ice extents in the 45-year satellite record, with 2021/22 and 2022/23 being the lowest. Sea ice loss harmed 30% of Antarctica's 62 emperor penguin populations between 2018 and 2022. Current climate models predict a longer-term loss in sea ice extent, although severe seasons are hard to link to climate change.

Understanding emperor penguin colonies

Emperor penguins moved to more stable areas the next year after sea ice loss. This technique won't work if sea ice habitat across an area is damaged, say scientists.

Modern emperor penguin populations have never been hunted, lost habitat, overfished, or otherwise harmed. Unlike vertebrates, climate change is the single main element affecting long-term population change. Recent estimates of sea ice loss have shown that over 90% of emperor penguin colonies would be quasi-extinct by the end of the century if current warming rates continue.

Satellite images discovered Rothschild Island, Verdi Inlet, Smyley Island, Bryan Peninsula, and Pfrogner Point penguin populations in the last 14 years. With only one breeding failure at Bryan Peninsula in 2010, all five colonies returned to the same spot each year to breed.

Since the brown streaks of emperor penguin guano stand out against the white ice and snow, scientists now use satellite photography to find and monitor colonies. The team used photos from the European Commission's Copernicus Sentinel-2 satellite project, which has studied Antarctica since 2018.

The Antarctic sea ice loss impact

Sea ice around Antarctica has dropped dramatically during the previous seven years. In December 2022, sea ice extent was the lowest in 45 years of satellite data. Sea ice didn't form in the Bellingshausen Sea, where this study's penguin colonies are, until late April 2023.

As of 20 August 2023, the sea ice extent was 2.2 million km2 lower than the 1981-2022 median (17.9 million km2), topping the record winter low of 17.1 million km2 on 20 August 2022. This missing area is larger than Greenland or 10 times the UK.