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Antarctica Called Him

By Melissa Hendricks
Photos by Dave Tewksbury
 

The bottom of the Weddell Sea is one of the most inhospitable places on Earth -- dark, cold and gloomy. Temperatures here, 2,800 feet down, barely rise above freezing, and until recently, a massive, 600-foot-thick pall of ice covered much of the sea's surface and blocked out the sun. These dark, frigid waters would never support significant life.

Or so scientists believed.

But three years ago, that pall of ice, the Larsen B ice shelf, broke away from the coastline, disintegrated into innumerable icebergs and floated away. Then, this past winter, a research team led by Hamilton Professor of Geosciences Eugene Domack lowered a video camera to the ocean floor at the site and discovered an exotic ecosystem that seemed to be right out of a Jules Verne novel: sulfur-eating bacteria, giant clams and miniature volcanoes thriving in a habitat that does not require sunlight. No one had ever seen such an ecosystem in Antarctica. The finding led to headlines in major newspapers and astounded even many scientists.

It was also entirely serendipitous, says Domack. He and his research colleagues weren't looking for signs of life on the mud at the bottom of the Weddell. What interested them was the mud.

Domack has spent the past 25 years studying the paleohistory of Antarctica, investigating how glaciers move sediment off the land and drag it into the ocean, exploring how ice shelves evolve and searching for clues to these problems in the sediment of Antarctica's seafloor. The currency of this trade is mud -- collecting it, processing it, examining it.

This endeavor might seem unfathomable to the non-geologist. Why venture to such a cold, forbidding place to dig in the dirt? To many of us, it is a place as harsh as Samuel Taylor Coleridge imagined when he wrote about the South Pole in Rime of the Ancient Mariner:

The ice was here, the ice was there,
The ice was all around:
It cracked and growled, and roared and howled,
Like noises in a swound!

Domack admits he's had some sweaty-palm moments on his expeditions. But he was smitten the first time he encountered Antarctica. In 1978, as a young graduate student on his first trip outside of the United States, Domack boarded a U.S. Coast Guard cutter in Wellington, New Zealand, that took him on a 12-day passage to a research site in Antarctica. It was not the Love Boat. Temperatures sometimes dipped to minus 50 degrees. Domack worked hard, 12-hour shifts, and when it was time to sleep, he and eight other guys crammed into a tiny, windowless cabin. But he loved every minute of it.

Where others imagine a stark, lonely land, Domack finds majestic beauty. Since his first voyage, he has returned to Antarctica so many times he's lost count.

"You're out on the deck just as the sun is rising. The orange turns into purple and blue over the mountains. The icebergs drift by. Those scenes are just unbelievable," he says. "The vistas are so vast. It's like the curtain opening on a brand-new world, and you know it's untouched."


Professor of Geosciences Eugene Domack explains the significance of sediments collected in the first kastern core of the cruise.

The same year that Domack first visited Antarctica, a geologist named John Mercer issued a warning in the journal Nature about the continent's ice shelves. These enormous palettes of ice fringe portions of Antarctica's coast. Fed by glaciers, the ice sheets can extend for hundreds of miles, some reaching state-size proportions. Before its collapse, the Larsen B was larger than Rhode Island. Mercer hypothesized that regional warming would start to melt the ice shelves, beginning in the north and proceeding southward. But the hypothesis was not widely accepted.

Domack was aware of Mercer's hypothesis when it was published, but, at the time, was not able to act on the findings. Instead of focusing on Antarctica's future, he was busy thinking about its past. After joining the Hamilton faculty in 1985, he launched a series of studies, with funding from the National Science Foundation, aimed at understanding how Antarctica's climate had varied over the past hundreds and thousands of years, and how those changes had shaped the continent, particularly its ice shelves. Those answers, Domack knew, were buried in the mud.

Everything that floats on or falls into the water -- algae, rocks, sediment -- ends up, layer by layer, on the bottom. These layers read like chapters in a storybook with a plot that can go on for thousands of years. However, it took a long time to figure out how to reach the language of this story. "I was starting from scratch," says Domack. "It was as if you wanted to read a book on the shelf in a foreign language. First, we had to learn to decipher that text."

The indispensable tools for this task have been the Kasten core, a three-meter-long aluminum tube, and a longer 25-meter jumbo piston core pioneered by Domack's team. Researchers use these devices to scoop cylinders of earth from the ocean floor. Using a winch and steel cable, team members lower the core sampler to the seafloor, which its cutter nose penetrates at a rate of 10 meters per minute. If all goes well, they then reel up a cylinder of mud. This task requires a lot of muscle, timing and luck. Workers can take six hours to retrieve a single core.

Inside the ship's laboratory, the researchers cut the core into thin slices (one centimeter thick or less), photograph each one and place each in a labeled container. Domack and his colleagues determine the age of each of these samples using radiocarbon dating. Various experts then examine the sample's contents.

Items in a sample might include fossils of diatoms, single-celled algae that have silica shells. Or they might include foraminifera, simple organisms that have a calcium-carbonate shell. These organisms live by floating on the surface of the sea; so their presence in a slice of core could correspond to a period when temperatures warmed enough to melt an ice shelf over that portion of seabed. An absence of diatoms or foraminifera, of course, suggests the opposite. By analyzing the sand and gravel in a sample, the scientists look to uncover other clues that could indicate a period of cooler temperatures, when glaciers advanced; when glaciers grow, they drag along chunks of rock and earth, fallout that eventually sinks to the seafloor.

In early 2002, Domack took a research cruise to the Antarctic Peninsula, the arm of land that stretches from Antarctica's main land mass toward the southern tip of Chile. Near the tip of the peninsula, where the Larsen B ice shelf sat, Domack noticed something strange. "Huge waterfalls were coming off of the ice shelf," he says. Thinking fast, Domack and his teammates collected six sediment cores from an area that had, until a few years ago, been covered by the ice shelf. (In 1995, portions of the Larsen B calved, leaving this area exposed.)


A segment of the former Larsen B ice shelf near Cape Fairweather (background) rises roughly 50 feet above the surface with more than 500 feet extending into the waters below. The blue bands show seasonal layering caused by snow accumulation and melting each year.

Apprentices on Ice

Heather Schrum '05 (left) and Ashley Hatfeld '05 (right) collect samples.

Twenty years ago, a research team traveling to Antarctica might have included Ph.D. scientists, technicians and perhaps a graduate student or two. Eugene Domack saw no reason why undergraduate students could not be part of that team.

So since 1987, he has made arrangements for more than 100 undergraduates from Hamilton and other colleges and universities to participate in his research expeditions. The funding for these ventures comes largely from the National Science Foundation, through grants that include education as one objective.

The students who participate in Hamilton’s Antarctica program say that Domack is a driven, motivated and inspiring mentor whose passion for research is obvious, and these students (usually geosciences majors) seem to share this same passion. They are drawn to a science that involves studying the stuff of the Earth. A love of the outdoors -- a geologist’s first laboratory -- lures some, as it did Matt Kirby ’93. Choosing an earth science major, he says, “was a no-brainer, the fact that you could study rocks and get a degree.” For others, the seduction begins with the glimmer of a piece of quartz. “Ever since I was a kid, whenever we went on vacation I’d be so excited about a rock,” says Gemma Kirkwood ’05. She remembers having to request extra baggage stickers so she could lug home her growing collection.

During this Antarctic apprenticeship, a student might be responsible for monitoring equipment, such as checking on the winch used to pull up sediment from the seafloor; then spend a few hours recording sea depth and GPS readings. Students also often work in the lab, processing the sediment cores that come in, smelling of sulfur and the sea.

Back at Hamilton, a student might use such a core to do the research for a senior thesis. Many of Domack’s students have found their names included either alongside his or even as first authors on journal articles. Some have presented their findings at a national scientific meeting. Kirkwood and her classmates Ashley Hatfield ’05 and Heather Schrum ’05 each featured posters on their Antarctica projects at the annual meeting of the American Geophysical Union. Sometimes the Antarctica research experience even blossoms into a career, as it did for Kirby, who is now an assistant professor of geology at California State University-Fullerton.

Of course, the expeditions are not all work. Students return with indelible memories — of clambering up a rocky Antarctic island to find a seal peacefully snoring at the top; of colors so intense and pure they seem to pop out of the landscape; and of an immense night sky. “At night, it was like someone had taken a paintbrush and spattered the sky with it,” says Kirby.

Even students who do not pursue careers in geology, says Domack, come away from the experience with a finer appreciation of how science is done. He aspires, he says, to show students that science is not just some guy in a white coat who every once in a while has an epiphany about how something works. “It’s a lot of elbow grease. When they leave Hamilton -- whether they become lawyers, dentists or mailmen -- I hope they understand and appreciate, as productive citizens, the serious contemplation and careful thought that goes into learning how the natural world operates. That’s a valuable perspective to have.”

The researchers did not know it at the time, but the Larsen B's collapse was imminent. Within months, most of the ice shelf had slid off the continent, dispersing 720 billion tons of ice.

Now, scientists' thoughts turned to Mercer. The Antarctic Peninsula has warmed by about 4 degrees Fahrenheit in the past 50 years, a change that many scientists attribute to greenhouse gases resulting from power plant emissions, car exhaust and other products of human activity. Could the Larsen B's demise demonstrate the consequences Mercer had foretold?
There were two alternatives to ponder: Was the break-up of the Larsen B ice shelf an unprecedented event, brought about by an unusual period of warming, à la Mercer? Or was the ice shelf's collapse simply one chapter in a recurring cycle of growth and decay over thousands of years? Or were both factors involved?

With the six muddy cores he had harvested a few months before, Domack thought he had the goods to answer this question. So he and his colleagues analyzed the cores, whose layers had been deposited over the course of a 10,000-year period called the Holocene that dates back to the end of the last Ice Age. The results were clear. In the top layer of the cores, the researchers found diatoms and foraminifera; deeper down, they saw hardly any sign of these organisms.

In other words, says Domack, "The latest ice shelf decay doesn't have a precedent in recent history. This event is unusual. The Larsen B ice shelf has been over the site for the entire 11,000 years of the Holocene." As to what caused its demise, while long-term thinning did occur, the recent surge in Antarctic temperature accelerated the ice shelf's collapse, says Domack, who reported these results in the August 2005 issue of Nature.

The Larsen B is not the only ice shelf that has disintegrated in recent years. The Antarctic Peninsula has lost 5,000 square miles of ice shelf in the past 30 years. Scientists are gravely concerned about what these events forebode. That's because ice shelves appear to restrain the massive glaciers that comprise the Antarctica ice sheets. When an ice shelf disappears, ice sheets flow and melt more rapidly.

"What we're worried about is that the large ice sheets of the Earth will melt," says Jonathan Overpeck '79, a professor of geosciences at the University of Arizona and a coordinating lead author for the Intergovernmental Panel on Climate Change. "If they do, a lot of people are concerned that it would raise sea levels substantially." Scientists have projected a five-meter rise in sea level if the West Antarctica ice sheet were to melt. If the Greenland ice sheet melted, sea levels would rise seven meters, according to this estimate.

The consequences would be devastating, says Overpeck. The violence of Hurricane Katrina, for example, would have been dramatically worse. "With the potential demise of these ice sheets, there's no way New Orleans would survive."
 
Domack's crew returned to the site of the collapsed Larsen B ice shelf this past February on a National Science Foundation research vessel. Among other projects, the researchers were mapping the region's seafloor, and part of this task involved using an underwater video camera to film the sea bottom beneath the former ice shelf.

The scientists did not get around to watching the videotape until their ship was heading back to port, but they weren't expecting to see much in the recording. After all, sunlight had not penetrated these waters. But when the video started rolling, "none of us could believe our eyes," says Gemma Kirkwood '05, a geosciences and mathematics major who went on the trip.

The first strange sight was a white, pustular mat that covered a large portion of the ground. Then came the mud volcanoes and the giant clams. "Could the white mat be some sort of fungus?" Domack wondered. But being a "mud person," says Domack, he wasn't certain. So he sent an e-mail describing the video to Hamilton geomicrobiologist Mike McCormick.

McCormick responded that the white mat sounded like a classic description of Beggiatoa, a bacterium that gets its energy by oxidizing hydrogen sulfide. These bacteria, which tend to co-exist with several other species in a layered microbial mat, are chemotrophic; they get their energy from chemicals such as methane and hydrogen sulfide, rather than from sunlight. The giant clams are part of this act, too. They rely on special sulfur-oxidizing bacteria that live in their gills. Domack now suspects that methane is the fuel that drives the system, seeping up from bedrock deep beneath the seafloor and flowing out through the mud volcanoes.

Researchers have observed similar "cold-seep" communities elsewhere, including in the Gulf of Mexico and Monterey Bay, Calif. But the Antarctic cold seep, a documented first, probably contains unique species, says Jim Berry, an associate scientist at the Monterey Bay Aquarium Research Institute. Antarctica is surrounded by the circumpolar current, which may act as a moat that blocks species from entering or leaving the Antarctic zone, and give rise to new species, in a manner similar to the evolution of Darwin's finches.

Domack reported his findings in the July 19 issue of the journal Eos, and the report has captured the imagination of scientists and non-scientists alike. But the findings also include some sobering news. The video shows that sediment and boulders have already fallen on and buried portions of the bacterial mat. It also reveals patches of green "fluff" -- probably the detritus from floating algae or plankton.

These events might start to shift the balance of nature in this ecosystem, says McCormick. To start, the detritus might invite shrimp, crabs or other predators. "Small changes can have a big impact," he notes.
In his journal articles, Domack has been cautious about linking these changes and the ice shelf's collapse to climate change. But in conversation, he speaks more boldly about why the ice shelf collapsed and what the event signifies.

"I view these changes as a monitor, a way that society can see how far our reach can go," he says. "We've had a very far reach. Our reach has gone, not just to Antarctica, but to this deep trough in the most restricted, remote place, to a deep cavity at the bottom of the ocean. If human activity has reached that far, then we are having a big impact; we need to think about this and maybe we need to change."

Whether change involves buying a hybrid car, as Domack has done, or some other effort, facing the consequences of climate change is now our own albatross. Domack says his mission is to study those changes and, like the old Mariner, to continue to report what he's witnessed.

On his next expeditions to Antarctica, Domack plans to expand the research he has done on the Antarctica Peninsula to include the entire continent. He is also writing a proposal for a National Science Foundation expedition scheduled for 2007-08. If he receives funding, he will use remotely operated vehicles to explore more of the seafloor beneath the site of the former Larsen B and to rove beneath other ice shelves.

Altogether, Antarctica's ice shelves cover more than a half-million square miles of seafloor, most of it unexplored. "We'll look at all aspects -- climate, oceanography, geography," and, of course, other signs of life, says Domack. "I'm sure there are more organisms awaiting discovery."
 

 

Melissa Hendricks is a freelance writer and former senior science writer for Johns Hopkins Magazine.

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