Unlike other sea birds, the four-feet tall Emperor penguins breed and raise their young almost exclusively on sea ice.
If that ice breaks up and disappears early in the breeding season, massive breeding failure may occur, said the researchers from Woods Hole Oceanographic Institution (WHOI).
"Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula," said Stephanie Jenouvrier, the lead author of the study published in the journal Global Change Biology.
"In 1948 and the 1970s, scientists recorded more than 150 breeding pairs there. By 1999, the population was down to just 20 pairs, and in 2009, it had vanished entirely."
Like in Terre Adelie, a coastal region of Antarctica where French scientists have observed penguins for more than 50 years, Jenouvrier thinks the decline of those penguins might be connected to a simultaneous decline in Antarctic sea ice due to warming temperatures in the region.
Disappearing sea ice, the researchers said, may also affect the penguins' food source.
The birds feed primarily on fish, squid, and krill, a shrimplike animal, which in turn feeds on zooplankton and phytoplankton, tiny organisms that grow on the underside of the ice.
If the ice goes, so too will the plankton, causing a ripple effect through the food web that may starve the various species that penguins rely on as prey, Jenouvrier said.
To project how penguin populations may fare in the future, Jenouvrier's team used data from several different sources, including climate models, sea ice forecasts, and a demographic model that Jenouvrier created of the Emperor penguin population at Terre Ad
