Changing Life: Sea Ice

Each winter, an area of the Southern Ocean roughly the size of the United States freezes around the Antarctic coastline. 

This sea ice provides a protective layer over the ocean: a cover that insulates it against the strong winds and cold temperatures above, and creates a sheltered habitat for life to flourish.

While the underside of the sea ice is an important habitat for Antarctic algae, krill and other small plants and animals, the sea ice surface is an important habitat for the largest penguins on the planet: emperor penguins. 

Emperor penguins breed, incubate their eggs and raise their young on the sea ice. They need a solid, stable platform of sea ice for around 9 months each year, to allow their chicks to mature and become independent before the sea ice breaks apart.

Emperor penguins are highly sensitive to changes in sea ice. 

If sea ice forms too late, or there is too little, emperor penguins do not have enough space to breed, raise chicks, hide from predators and rest while molting (replacing their damaged feathers). 

If there is too much sea ice, the distance between their colony and their open water feeding grounds becomes too large. This longer journey can lead to exhaustion and starvation for emperor penguins and their chicks. 

Even when the amount of sea ice is just right, if it breaks up before the chicks are fledged and independent, entire generations can be lost.

Since then, sea ice cover has continued to decline.

In the summer of 2022 sea ice in Antarctica’s Bellingshausen Sea plunged to historic lows. Some areas were completely ice-free for the first time in the satellite record.  

In the spring, emperor penguin colonies in the surrounding area suffered widespread breeding failure when the sea ice broke up before the chicks had fledged.