At nearly four feet tall, the Emperor penguin is Antarctica's largest sea bird -- and thanks to films like "March of the Penguins" and "Happy Feet," it's also one of the continent's most iconic. If global temperatures continue to rise, however, the Emperor penguins inTerre Adélie, in East Antarctica may eventually disappear, according to a new study by led by researchers from the Woods Hole Oceanographic Institution (WHOI). The study was published in the June 20th edition of the journal Global Change Biology.

"Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula," says Stephanie Jenouvrier, WHOI biologist and lead author of the new study. "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 Adélie, 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.

Unlike other sea birds, 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, says Jenouvrier. "As it is, there's a huge mortality rate just at the breeding stages, because only 50 percent of chicks survive to the end of the breeding season, and then only half of those fledglings（刚会飞的幼鸟） survive until the next year," she says.

Disappearing sea ice 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（浮游动物） and phytoplankton（浮游植物） , tiny organisms that grow on the underside of the ice. If the ice goes, Jenouvrier says, so too will the plankton, causing a ripple effect（连锁反应） through the food web that may starve the various species that penguins rely on as prey.

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 Adélie, a coastal region of Antarctica where French scientists have conducted penguin observations for more than 50 years.

Combining this type of long-term population data with information on climate was key to the study, says Hal Caswell, a WHOI senior mathematical biologist and collaborator on the paper.

"If you want to study the effects of climate on a particular species, there are three pieces that you have to put together," he says. "The first is a description of the entire life cycle of the organism, and how individuals move through that life cycle. The second piece is how the cycle is affected by climate variables. And the crucial third piece is a prediction of what those variables may look like in the future, which involves collaboration with climate scientists."