Caught in a Melting World

Adélie penguins may be the canaries in the coal mines of global warming

  • Story and photographs by Tui De Roy
  • Nov 01, 2000
Four little heads pop up simultaneously in a jagged pool of blue-black water surrounded by ice as far as the eye can see. They are Adélie penguins, and the ice defines their existence.

Like little torpedoes, the birds - just over 2 feet long - leap about excitedly in tight circles, rocketing in and out of the water, perfectly at ease in this frigid sea that surrounds the shores of Antarctica. Not only at ease, but at home. The seasonal freezing and thawing, spreading and shrinking, of the ocean´s surface is the world they know. In recent years, as Earth´s climate has warmed, it has also become a world in rapid and disturbing change.

The Adélies´ home is a place made up of great plates of frozen water. Floes half a football field in size crunch and grind against one another as powerful ocean currents and opposing winds shove and shift the entire mass in enormous swirls and gyres. Under this constant motion, cracks and fissures open and close, and tidal eddies force open large pools. This is what the Adélies use to transit between the landscape above the ice, which they need for air to breathe, and the one below, which provides them with food.

Their food is tied, literally, to the frozen ocean. Within spongy layers of sea ice, microscopic algae bloom in profusion as sunlight floods in from above. When the sea ice melts with the onset of summer, the algae, aptly called ice algae, escape into the water, where they are grazed by dense swarms of krill - a type of shrimplike crustacean. The krill, in turn, are the Adélie penguins´ primary food. To eat them, Adélies spend their entire lives on, around or beneath the Antarctic pack ice.

It is now late spring in the Ross Sea, some 1,800 miles due south of New Zealand. Three more penguins erupt from the water as I watch, emerging through the 6-foot-thick layer that covers the rich waters where they have been feeding. By following cracks and leads, the penguins have been able to push farther and farther into the heart of the pack ice, for these penguins are on an urgent mission.

As the seven heads appear together at the surface, I hear their harsh contact calls clearly in spite of the cutting wind in my ears and the fact they are almost 300 feet away. Otherworldly caws, a sound they produce only when they are at sea, enable the sociable birds to maintain contact even in stormy conditions. For a moment they seem to hesitate, reluctant to leave the watery realm through which they dart as effortlessly as fish. Then all at once, they shoot up out of the water like squeezed cherry pits, landing feet first on the ice.

For just a few seconds they stand still, their black-and-white plumage still enveloped in a veneer of water, as shiny as if they were shrink-wrapped in cellophane. Then, as one, the little flock sets off southward across the ice, some waddling, others sliding or tobogganing, as this mode of penguin travel is termed heading for the faint outline of a snowy mountain range hanging uncertainly in the distant haze. At the base of those mountains some 30 miles away lies Cape Adare, where each year at this time some 280,000 Adélie pairs get together to raise their young in a frenzy of hyperactivity the largest such colony in all of Antarctica.

As I watch, the seven birds recede until they are but tiny black dots in the glaring white distance. After a feeding trip that may have covered as much as 180 miles of sea and ice and lasted from a week to as long as three weeks, they are headed back to their nests. Each will relieve a fasting mate with which it has been taking turns incubating two eggs for the last five or six weeks. Now these penguins´ inner clocks tell them that across the colony, fuzzy gray-black heads and hungry beaks are popping out of eggs in every nest.

At Cape Adare, after 12 hours of ramming and crunching through the pack ice on a 430-foot Russian icebreaker, I have landed among the penguins, and the hubbub of activity is almost bewildering. The entire breeding process is in full gear and must be completed in the short few weeks that represent summer in these high latitudes.

The first birds, all males, have arrived there about two months earlier, navigating unerringly across the ice in the deep chill of early spring. Within the first two weeks, each one relocates his nest of previous seasons. His first task: to scrape it clean and add a few pebbles to ensure good snowmelt drainage. Soon the females will come ashore, too, mates of previous years seeking each other out and reuniting in a celebration of screams and brays, head-waving and posturing.

And now, having each put in their time trading off feeding and incubating, the sitting ones trust in the timely return of their mates. New moms and dads everywhere respond to shrill baby peeps with excited nods and bows, carefully clearing away eggshell shards from around fragile hatchlings tucked between their feet.

All along the shore, where slabs of storm-tossed ice are still piled high, wave upon wave of returnees run up the gravelly beach and fan out across the crowded colony as each bird follows a precise route among tens of thousands of neighbors to make a beeline for its nest. The incessant motion of the penguin mass blankets the land. A constant flow of commuters hurries to and fro. Fights and chases erupt when personal penguin space is invaded or when young marauders snitch a few prized pebbles to start building nests of their own. Reunited pairs display ecstatically, and parents greet new babies. Victims of egg-plundering skuas, which resemble large rapacious gulls, squawk indignantly. The cacophony of calls conspire with the ceaseless motion to create an inebriating atmosphere that plunges me deep into the Adélie penguins´ world, where timing is all.

Within hours of hatching, the tiny chicks are raising their wobbly heads, begging for food, for they, too, know innately that growing up is urgent in a land where summer will only last a few weeks. Their besieging squeaks are answered by their parents with ready beak fuls of krill puree, dutifully carried back by the bellyful from the sea still far away across the fast ice - that ice still firmly attached to the shore.

And now begins a true race against time, a race dominated and ruled not so much by the season as such, but by the patterns and movements of the sea ice offshore. With young mouths to feed, the Adélie parents must now divide their time for the first couple of weeks or so of their chicks´ lives. On the one hand, they must secure a plentiful supply of food from the ocean. On the other, they must shelter their vulnerable babies from the harsh weather and predation by skuas, which swoop low overhead in search of food for their own young.

Penguin parents again take turns feeding and nest guarding. For them, it is crucial that the summer breakup of the sea ice advances apace with the feeding needs of their chicks. Should the ice linger too long, requiring trips in excess of 60 miles or so, the chicks will either starve to death or grow too slowly to survive. If the ice breaks out and melts too early, the ice-driven food chain which culminates in dense krill swarms will be weakened, and chicks will be left unattended, too young to fend for themselves while both parents desperately seek food scattered too thinly or too far to sustain their families.

On an earlier journey to the opposite side of the Antarctic, among the islands of the South Orkney chain, I had witnessed an entire colony struck by such severe food shortages. Although these chicks were less than two weeks old in late December, the vast majority of parents were nowhere to be seen, gone far out to sea in a desperate search for food. To compound their problems, the temperature was so balmy - in the upper 40s Fahrenheit - that the moisture-laden sea breeze formed a persistent drizzle, turning the entire penguin colony into a quagmire of snowmelt and krill-stained guano. Here and there, miserable clusters of small, bedraggled chicks, all soaked to the skin by the rain, huddled together pathetically for warmth, their downy coats mud-splattered and their normally rotund stomachs hollow and sagging. Satiated skuas pecked languidly among them at dozens of trampled carcasses.

Frighteningly, such scenes have become ever more frequent in the last few decades, especially around the Antarctic Peninsula, which is the northernmost and warmest part of the Adélie´s range. As the rest of the planet slides gradually into warmer climate trends - a change thought to be caused by human burning of fossil fuels - scientists working at the United States´ Palmer Station in this part of the Antarctic report that average temperatures here have increased by as much as 3 to 5 degrees Fahrenheit in summer over the past 50 years, and an incredible 7 to 9 degrees in winter. That increase is at least ten times faster than for the rest of the world. At the same time, good winter pack ice cover, which fluctuates naturally from year to year, now occurs in only one or two out of every five seasons. Back in the 1950s, it was four out of every five.

The higher temperatures also tend to increase snowfall on the Adélie´s nesting grounds in winter. This delays and hampers breeding efforts as the summer melt inundates nest sites, chilling unprotected chicks with rain and mud, just as I had observed in the South Orkney Islands. So much warmer is the temperature that even ticks are now surviving the winter and plaguing nesting birds in spring.

The ever-increasing ozone-hole problem, a fluorocarbon-induced thinning of the protective ozone layer in the upper atmosphere, adds yet another unknown factor to a tricky equation. The hole is now reaching well over 10 million square miles in extent. Unscreened by ozone gas, solar ultraviolet radiation strikes the surface of the Earth here and substantially reduces the productivity of the ice algae, scientists believe, and thus the krill on which the Adélies depend.

The combined effect of all these threats is already translating into drastic population declines in several Adélie penguin rookeries where long-term studies have been carried out. In five colonies near Palmer Station, numbers of breeding pairs have dropped from 15,200 to 9,200 in 25 years, while some smaller colonies have disappeared altogether. And the problem seems to be accelerating fast, with a 10 percent Adélie population decline in the last two years alone. At another site farther north, a loss of about 35 percent has been measured in just ten years. These findings have caused at least one scientist, ecologist William Fraser of Montana State University, to warn that Adélies could be regarded as the "canaries in the coal mines" of global warming.

As I gaze upon the Adélie´s frozen world, it strikes me as a cruel irony that this little penguin’s superb adaptations to an extreme environment and its very dependence on sea ice could be its undoing. Fortunately, however, there are numerous Adélie rookeries around the Antarctic continent, especially in the far south, where there is no hint of such drastic trends, at least not for the time being.

Back at Cape Adare, there is no sign of any calamity either. One month after watching the chicks hatch there, I am back again. Everywhere plump youngsters almost as large as the adults waddle about, well fed to the point of obesity. No longer nest-bound, they gather in huge, tightly packed crèches while their parents are out fishing. Low snow banks that had served as commuter routes have now turned to stagnating pools where hordes of returning parents, their bellies distended with food for their insatiable young, splash along hurriedly under the golden evening sun. Each adult calls out his or her own chicks from the seething mass, with each side recognizing the other by voice. There is a happy, contented atmosphere about, fat chicks getting fatter in preparation for the big departure, the biological clock of the Adélie ticking right on time.

NWF Takes Action

Tracking Wildlife And Climate Change

Worries about global warming have centered on rising sea levels, spread of tropical diseases, increases in violent storms, disruption of farming and other impacts on people. But increasingly scientists have also begun to look at impacts on wildlife, from Adélie penguins to polar bears. "Global climate change has the potential to wipe out more species, faster, than any other single factor," says Patty Glick, coordinator of the Climate Change and Wildlife Program at NWF. For more information on the effects of climate change on wildlife or for reports on what the Federation is doing on behalf of species at risk, check the NWF Web site at

I make my final visit here another three weeks later, and what a contrast awaits. The first snows of winter have already dusted the land, while the nesting plain that had been so covered in birds now holds endless strings of waddling penguins heading for the sea in one great exodus. Only a few runts, chicks whose parents had perhaps fallen prey to a toothy leopard seal, are left behind to feed the skuas. Adults and chicks, the youngsters still sporting comical tufts of down on their heads, all launch themselves into the thundering surf, no longer in families but all bound for the sea ice already reforming offshore.

There they will spend the next seven months, out of sight of land, sleeping and molting on the ice, and diving more than 500 feet beneath it to feed. They will travel as far away as 750 miles through the sunless winter, not to return until the new spring. With a life expectancy of 10 to 20 years for successful juveniles, these wanderings may last as long as five years before the young birds, too, come back and begin to raise their own families.

I watch them disappear by the tens of thousands into their icy world in the gathering autumn dusk. All around Antarctica at this same moment, a scene similar to this one is being replayed, as an estimated five million Adélies, plus their young, leave the land behind to live at the whim of the ice - their true home.

Roving Editor Tui De Roy has traveled to Antarctica 22 times since 1987, observing and photographing Adélies on every trip.

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