Emperor penguins usually lay their eggs in May or June, but the chicks must remain on the ice until they fledge in the southern hemisphere summer, in December or January. Before this point, the young birds lack the waterproof feathers they need to survive in the water.

Any melting or breakup of sea ice before this is catastrophic, as the chicks “will go into the water and either drown or freeze to death even if they do get back out,” Peter Fretwell, the study’s lead author and geographic information officer at the British Antarctic Survey, said in a telephone interview Friday. “Now, we saw this happened all over Antarctica, at many sites.”

Of the emperor penguin’s 62 known breeding sites across Antarctica, 19 suffered some breeding failure, with complete failure in six, according to Fretwell.

Climate change threatens emperor penguins with extinction, officials say

And the impact on the penguins’ breeding patterns is expected to continue into this year, as sea ice formation only began in late June — months later than normal. By then, “the emperors should have been sitting on their eggs already,” Fretwell said.

“So it’s inevitable that in the Bellingshausen Sea there will be virtually no breeding, we don’t think, this year. For the rest of the continent, we’re waiting for the sun to come up to see what the consequences of this extremely low sea ice year are going to be.”

The penguins normally arrive at their breeding sites in late March to April, where they lay and hatch their eggs.

Emperors are the world’s tallest and heaviest species of penguin, but only lay a single egg each year. As they rely on stable sea ice that is firmly attached to the shore to reproduce, they are particularly vulnerable to the effects of climate change. Last year, the U.S. Fish and Wildlife Service granted the species federal protections under the Endangered Species Act.

The team used satellite imagery to monitor the presence of distinctive brown stains on the ice from the birds’ excrement, known as guano, which indicates the presence of emperor penguin populations.

Floating ice around Antarctica just hit a record low

In 2022, some parts of the Bellingshausen Sea recorded a 100 percent loss of sea ice extent in November.

“Last year was the lowest we’d ever seen,” according to Fretwell.

The penguins usually seek new breeding sites if they experienced the loss of sea ice the previous year, but this could prove more and more difficult if larger areas are affected, the study said.

Antarctica and Greenland have lost more than 6.4 trillion tons of ice since the 1990s, according to scientists — accounting for more than a third of the rise in global sea levels.

A 2021 study found that nearly all emperor penguin colonies could face extinction by the end of the century.

But those estimates are “not a foregone conclusion,” Fretwell notes. “Although there are several decades of warming in the system, so it’s likely to get worse before it gets better ... we can still turn this around.”

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Climate change is the only major factor influencing the emperor penguin’s long-term population change, the British Antarctic Survey said, meaning such studies offer a particularly clear indication of the impact of the climate crisis.

“For emperor penguins, it’s direct and we can see it happening and there are no other drivers. But for many other species, it’s more cryptic and we can’t really tell what’s happening to them,” Fretwell said.

“So the emperor penguin is a bellwether, and it’s probably at the forefront of this. But there are many species, many ecosystems, both in the poles and around the world which will suffer if we don’t turn the climate crisis around.”