by Adelheid Fischer

It is January 2004, the height of the Antarctic summer. A snapshot by National Geographic photographer Peter Essick captures Tad Day wearing a look of pure concentration as he presses close to the ground of Anvers Island. Bareheaded and ungloved with pencil and notepad in hand, the botanist gently pries apart the stalks of tiny tundra plants that grow in the rubble of this island off the coast of the Antarctic peninsula.

Although the cloudless morning seems downright balmy, it is not without a sense of urgency. As he peers into the jumbled carpet of hair grass, pearlwort, lichens and mosses, Day’s head is slightly cocked. It’s as if he were listening for icebergs calving from a nearby glacier.

Five miles of open water separate the island from a hot shower and dry bed at Palmer Station, the base camp for scientists visiting the western coast of Antarctica. A small shift in the wind could quickly corral the sea’s far-ranging floes and push them to shore, creating an impassable field of grinding ice.

“You get engrossed in work and don’t pay attention,” says Day, a professor in the School of Life Sciences at Arizona State University. “The next thing you know, you’re asking, Where did the ocean go? You look out and there’s nothing but miles of white.”

But shifting ice isn’t the only thing that lends urgency to Day’s work. It was 1994 when he made his first research foray to the frozen continent. He recalls reading an obscure scientific paper warning that Antarctic temperatures were on the rise.

“I thought, maybe somebody would be golfing down there in a thousand years or so,” he says. Of far greater concern to Day and his fellow scientists at the time was the thinning in the Earth’s protective ozone layer every spring and early summer over Antarctica. Back then, Day examined the ways in which Antarctic plants coped with the excess dose of damaging ultraviolet radiation that streamed through the ozone hole.

But subsequent research has shown that the temperatures of Antarctica are climbing far more steeply than initially noted—up to 10 times the global average, according to some estimates. The unprecedented opportunity to document plant communities in one of the most rapidly warming regions on Earth prompted Day to enlarge the focus of his research. Today, he and his team of graduate students are studying the dance of tundra and ice as they move across the landscape in response to the accelerating beat of warming temperatures.

The changes have caught even veteran scientists such as Day off guard. One of the most surprising developments is the sheer amount of new real estate that has been newly vacated by the glaciers. Travel to some of his research sites, Day points out, once entailed navigating the team’s Zodiac boat along a wall of ice some five stories high.

Today, the glacier has largely given way to rocky beach. The transformations are so pronounced that Day has been forced to revamp the maps of his study sites that were drawn from aerial reconnaissance in the 1990s. Jutting fingers of land have become islands seemingly overnight as connecting bridges of solid ice have melted away.

“One of the things that’s shocking to me is how quickly it’s warmed down there,” he says. “I never thought I’d see such big changes in my lifetime.”

Terrain that hasn’t seen sunlight for thousands of years now is being claimed by tundra plants with a speed that astonishes Day and his team.

Take Point 8, for example, a recently deglaciated spit of land on Anvers Island. On a survey of the point in 1995, the researchers could find no trace of Antarctic hairgrass and Antarctic pearlwort, the only two flowering plants that are native to the continent. But by 2004, nearly 300 pearlwort plants had taken root; the hairgrass population soared to more than 5,000 plants. So lush was this growth that, from a distance, some stretches of rock rubble looked as if they were covered with a layer of turf, Day says.

What accounts for the exponential increase? For one thing, Antarctic plants benefit from a ready supply of nutrients, such as nitrogen and phosphorus that are far more limited in polar regions of the north. The difference, Day speculates, is due to the fertilizing guano that is supplied by large numbers of marine birds such as gulls, penguins and skuas, as well as mammals such as seals.

On the Antarctic Peninsula, Day says, “You’re never far from a penguin or a seal or a gull. There are so many of them around.”

Day’s experiments have demonstrated that warmer temperatures sharply increase the odds that seeds will be able to take advantage of these nutrient stores. In a series of plots constructed behind Palmer Station, Day’s team has recreated what he calls a “microcosm of the tundra.”

The experiment includes 240 cores of mature tundra that were excavated from a separate field site some eight miles away. Using infrared heaters, the team is able to carefully control temperatures as well as calibrate inputs such as rainfall. Funnels capture leachate from the tundra plugs so that the researchers can measure the amount of carbon and nitrogen that leaves the system. In this way, they can test the response of tundra plants to a variety of global warming scenarios.

Results show that even a warming of just one degree Fahrenheit can dramatically boost the number of viable seeds that tundra plants produce.

For example, a single pearlwort plant can sprout hundreds of tiny flowers. But only a fraction--eight seeds per square centimeter—will mature and be viable before summer’s end and the return of snow in March. A small increase in temperature boosts the number of viable seeds that plants produce to more than 150. The reason, Day says, is that warmer temperatures allow more flowers and their seeds to mature before the end of the growing season.

With the combined advantages of soil nutrients and warmer temperatures, tundra plants have invaded large stretches of newly deglaciated Antarctic terrain. But Day cautions that the continent is not likely to become a golfing destination any time soon.

Warmer temperatures cause greater evaporation. More moisture in the air leads to heavier precipitation. As a result, the region’s winter snow pack appears to be increasing along with its temperatures. Plants that have colonized areas prone to snow accumulation can be wiped out in a few years of above average snowfall.

“You can have an area the size of half a city block covered with plants and then two years later not a single plant is alive,” he explains. “That’s the flip side of warming for the plants down there.”

The ebb and flow of these tiny plants in a remote Antarctic outpost could help researchers shed light on the larger problem of global climate change. Day notes that climate scientists have a fairly accurate tally of the amount of carbon dioxide that is emitted into the atmosphere from the burning of fossil fuels by automobiles, say, or coal-fired power plants. (CO₂ is a major greenhouse gas that causes global warming.)

Whether the Earth’s large natural ecosystems, such as rainforests, boreal forests, tundra or grasslands, will contribute to the buildup of atmospheric CO₂, or serve as critical storage, remains a wild card.

In the Arctic, for example, scientists have found that warming temperatures are causing deep layers of frozen peat, known as permafrost, to thaw. The stepped-up microbial activity in this peat is releasing significant amounts of CO₂, thereby hastening further global warming.

According to Day, the melting of the Antarctic tundra is not likely to send vast concentrations of CO₂ into the atmosphere since the thickest permafrost measures no more than one foot deep. In addition, higher temperatures appear to stimulate plant growth, causing them to take in more atmospheric CO₂.

Still, he cautions, little is known about the Antarctic tundra ecosystem despite the fact that it hosts only a sparse sampling of plants and an equally bare-bones suite of animals including microbes, several species of springtails and mites, as well as a wingless midge that Day jokingly refers to as “the largest land animal native to Antarctica. It’s at the top of the food chain.”

Day’s research has made one thing clear, however: the plants have a definite thermal threshold. When temperatures get too warm, they simply shut down operations. If he has learned anything from his many trips to Antarctica, it’s that major ecosystem change can be triggered with the proverbial flip of a switch.

Already, he says, some organisms such as Adele penguins appear to be dropping out of the mix along the Antarctic peninsula. Their numbers have plummeted from several thousand in the 1990s to some 500 animals today. The decline is largely due to the increased incidence of early season storms that bury their shore-edge nests in great drifts of snow.

“There’s a lot of skepticism and public misunderstanding about global change issues and greenhouse warming. There’s so much misinformation out there,” Day says. “This is a great story for what can happen and there are some valuable lessons.”

ASU research projects in Antarctica are supported by the National Science Foundation. For more information, contact Thomas A. Day, Ph.D., School of Life Sciences, 480.965.8165, or email tadday@asu.edu