The Ragged Edge of the World (23 page)

Conway's experiment was as simple as the valleys. After digging a tunnel into the base of the glacier (not without risk, because the face is constantly shedding huge blocks of ice), the scientist drove a series of bolts into the side of the tunnel in a straight vertical line from bottom to top and left them for a year—until about the time of my visit.

Conway himself wasn't there the day I came to the valleys, but his colleague Charles Raymond from the University of Washington took me to the tunnel. Charlie, as he is called, is a grizzled veteran of many seasons in Antarctica. He has long gray hair and an affable disposition. It seems as though there is nothing he'd rather talk about than ice.

The walls on the side of the tunnel showed a relatively clear bottom layer, followed by a layer of amber-colored ice (discolored by dirt picked up from the bottom), and then clearer ice above that. As for the bolts, the bottommost series of bolts remained nearly vertical—confirming Conway's supposition that the cold (-17ºC) bottom ice was frozen to the underlying ground. The amber layer had moved out toward the edge a bit, while the upper layer was still closer to vertical. Conway interpreted this to mean that the amber ice was folding over the base ice, carrying forward the amber ice on top of it. Picture the way thick molasses would move if its bottom layer were stuck to a tilted pan. As for the clear ice on the bottom, Conway's explanation was that this was ice that had fallen off the edges of the glacier and then become squeezed solid as the ice mass moved over it.

So there it was, the image of how a glacier moves. In some respects, it is like moonwalking; in others, like molasses. Perhaps the most apt image, however, is that of a very large and very slow amoeba that extends a pseudo-podium of ice and then advances over the slick surface.

After we exited, Charlie filled me in on some of the properties of the thousand feet of ice that was massed above us when we were in the tunnel. Ice moves in response to a variety of forces, dominant among them gravity. As the ice in a glacier thickens, the weight and composition of the ice itself create stresses and strains. At about 400 meters thick, the ice is subject to 1 bar of stress, a bar being equivalent to one atmosphere or the pressure under 10 meters of water. Charlie explained that once the stress rises above 1 bar, the ice begins to deform, thinning and spreading out rapidly. Though the action is imperceptible to impatient humans, glaciers and ice sheets are alive with movement, belying the static implications of the word “frozen.” Big masses of ice don't just fold and spread; there are streams of ice that move through them, sloughing off excess accumulation when they reach the terminus.

Paul Langevin, who studied the Canada glacier that flows into the valleys, has also monitored the forces maintaining the stability of the area. Because the area surrounding the Dry Valleys is a desert, there is very little accumulation of ice each year, while the sun melts between 20 and 50 centimeters of ice annually (depending on the angle of the sun as it hits the face or top of the glacier) through sublimation, as ice evaporates here without ever becoming water. The glacier is also flowing forward a few meters a year, but it never advances because the sun hits its face and because the front is continuously calving ice. Because of these relatively rapid movements, Langevin believes that the ice in this glacier is only thousands, rather than hundreds of thousands, of years old. So, even though a million-year time-lapse film of the glacier would show extraordinary stability, the ice of which it is made is constantly changing.

The great glaciers of Antarctica convey solidity, permanence and awesome scale, but the geology of the Dry Valleys also reveals how much more vast the continent's ice sheets once were. Looking at the bare, flattened, 8,000-foot-tall mountaintops that surround the valleys, it's possible to envision the scale of the massive ice sheet that once extended over what is now the one ice-free spot on the continent. Seeing those flattened mountaintops is a reminder that change does come to the Dry Valleys, though on unimaginably long time scales. The last time these valleys were wet—about 13.8 million years ago according to recent studies—was several million years before ancestral forms of humans started trying to figure out how stone tools worked. Four and a half million years ago, there were two very large lakes in the valleys, of which the twenty or so much smaller present-day lakes are remnants.

Now, like some geologic-scale Rip Van Winkle, the lakes have begun to awaken and change again.

While the rest of the world began warming at an accelerating rate in the 1980s, for the most part Antarctica stayed on the sidelines. Perhaps the warming strengthened the Antarctic vortex, the air currents that encircle the continent, further insulating it. Or perhaps something else was at work since there is no more complex system than climate.

In recent years, however, the effects of warming have been creeping into Antarctica, most notably at its edges. The Antarctic Peninsula, which once reached like an umbilicus toward South America and now juts out beyond the protective cordon sanitaire established by the Antarctic vortex, has warmed dramatically in recent years. As temperatures have shot up on the peninsula, ice shelves, some of which had been in place for thousands of years, have collapsed. In the case of the Larsen B Ice Shelf, the collapse took just a few weeks and was captured by satellite imagery. Similarly, on April 6, 2009, the 40-kilometer-long ice bridge that tethered the Wilkins Ice Shelf to the Antarctic Peninsula disintegrated, making the Wilkins the tenth major ice shelf to collapse in recent times.

While the warming of the peninsula is understandable, even if it is not reassuring, changes within the vortex are more disturbing. It's been snowing a bit more at the South Pole, for instance, a place conventionally thought to be beyond the reach of changes in the weather. Just before my visit, it rained at McMurdo Station, something never before documented in a place that previously encountered precipitation only in the form of snow. And then, a few years after my visit to the Dry Valleys, the area experienced what was described as a “flash flood.”

This occurred during the summer season of 2001-2002. Only in the Dry Valleys could the several-inches-deep flow of water that resulted from the warm temperatures that year be called a flood, but in a place where the weather never changes, change is highly noticeable. Accounts from that season report that the Onyx got so deep, scientists were forced to wear hip boots to wade across. Cracks appeared in the ordinarily smooth surface of the tops of the glaciers, providing more surfaces exposed to direct sunlight (the sun is always low in the sky at that latitude) and furthering melting. Temperatures rose as high as 10 degrees Celsius, and some veteran scientists ignored NSF guidelines and roamed the area in shirtsleeves.

While the flood provided them with a fabulous opportunity to study how a simple ecosystem responds when change comes (the lakes became less saline, algal mats were washed away, nematode populations exploded), it also raised questions. Was the warming part of some natural cycle, or was it evidence that human-caused changes in the atmosphere were beginning to penetrate Antarctica's formidable defenses against the rest of the world?

While the Dry Valleys provide a sensitive indicator of what might be happening in Antarctica, a large cohort of scientists is monitoring Antarctica's vast ice sheets, where any change would have global implications. The East Antarctic Ice Sheet dominates the continent, but the smaller West Antarctic Ice Sheet (WAIS) has been getting the most attention. “Smaller” is a relative term. To put it in perspective, consider that the melting of all the world's mountain glaciers would raise sea level by less than a foot and a half. If the WAIS disintegrated and slipped into the sea, it would raise sea level by 16 feet. (For the East Antarctic Ice Sheet, the number would be 170 feet.)

As is the case with a glacier, the outward stolidity of an ice sheet conceals a great deal of turmoil beneath the surface. Streams of ice move through the sheet, pushed and pulled by various forces within it, including gravity. When I was there, a number of scientists were trying to determine whether these streams have sped up. At that point, there was interest but little real anxiety that this vast mass of ice might collapse on a time scale meaningful to anyone living today. Now, thirteen years later, there is genuine concern that this might happen.

An analysis of temperature data taken from various points in Antarctica and published in
Nature
in 2009 provides “robust” evidence that the West Antarctic region has been warming significantly—not as fast as the peninsula that juts outside the Antarctic vortex, but still more rapidly than eastern Antarctica. Moreover, some of the ice streams that dump ice into the water near Pine Island are moving ever more briskly. This is alarming because the ice shelves surrounding Pine Island serve as a kind of doorstop, preventing the more rapid flow of ice into the sea. As we have seen in recent years, the breakup of ice shelves can be quite rapid.

As this has focused the mind, one unresolved issue has gained the status of an interesting question: When was the last time the ice sheet disappeared? When I spoke with glaciologist Ian Whillans (he died in 2001, and an important part of the West Antarctic Ice Sheet now bears his name), he noted that the positive feedbacks that turn a slow decay into a rapid disintegration are very difficult to model and that “this gets you nervous about predictability.” Another ice sheet specialist, Reed Sherer, told me that the most surprising thing about the WAIS would be if it was much older or much younger than everybody thinks. If it turned out to be younger than 100,000 years old, it would make everybody extremely nervous. If, on the other hand, the WAIS was older than 10 million years, we might breathe easier, because that would imply that it survived through the last protracted warm period, 400,000 years ago. (To put in perspective how warm that period was, the polar front retreated to 58 degrees south, versus its present variance between 48 and 52 degrees.)

Sherer then went on to answer his own question by finding diatoms in an ice stream dubbed Upstream B that strongly indicated that there was open water under that region 400,000 years ago. He could date when the diatoms were laid down by comparing their chemical composition with that of other diatoms, a process called biostratigraphy, which is analogous to matching tree rings to calibrate dates. The discovery that a great ice sheet like the WAIS might collapse during an interglacial warm period is not reassuring, particularly since we are now busily engineering our own warm period.

Our hope is that the longer wavelength phenomena of the overlapping time scales at play in the workings of the ice sheet will prove to dominate in the struggle of forces that determine when the ice sheet might collapse. If it can take 10,000 years for a pulse of warming entombed in the ice to make its way from the bottom of the sheet to the top, then maybe a collapse will take place in slow motion as well. Unfortunately, that remains only a hope, not a confident prediction, and that hope is challenged by the increasing drumbeat of disintegrating ice shelves as well as an alarming shrinkage in the Greenland ice sheet in the north.

Change in Antarctica is already taking its toll on creatures that evolved to withstand the harshest imaginable conditions. The maturation of emperor penguins, for instance, has evolved in precise coordination with the breakup of sea ice during the Antarctic summer. When I visited Antarctica, Gerald Kloyman, a biologist who has devoted his career to studying the birds, told me that the ice that year broke up two weeks early, forcing the young to dive into the Southern Ocean before they were ready to cope with its many dangers, dooming most of the fledglings.

Outside of the vortex on the Antarctic Peninsula, changes have been equally dramatic. The area covered by sea ice has shrunk dramatically, and along with it the krill population (which depends on algae trapped in the sea ice). The peninsula penguin populations have begun to swing wildly, with Adélie numbers plummeting, while open-water-favoring penguins such as chinstraps and gentoos do better.

While a few might still question whether the climate changes in Antarctica are part of a natural cycle or the result of human activities, virtually no one disputes that the ozone hole that appears annually over the continent is a curse resulting from generations past when humanity used chlorofluorocarbons in refrigeration and spray cans. Initially CFCs were hailed as miracle compounds because they were supposedly harmless. (Their inventor, Charles Midgely, used to drink Freon to demonstrate its safety.) Though they might be benign here on earth, they wreaked havoc once they floated to the upper atmosphere, where it was discovered that tiny amounts of CFCs could act in concert with sunlight to destroy the ozone layer that protects life on earth from lethal cosmic radiation. Though CFCs are now banned, those already produced have a lifetime in the atmosphere measured in several decades. As a result, the ozone hole continues to reappear each year.

Because of the vast number of interrelated moving parts involved, it is practically impossible to predict how our alterations of the atmosphere will play out, particularly since damage to the ozone layer is taking place at the same time that humans are otherwise changing the chemical balance of the atmosphere through the release of greenhouse gases. We are going to have to wait and see the results of this real-time, inadvertent experiment with the fundamental recipe for life on earth.

In the meantime, the fractured, disintegrating, and disappearing ice is telling us that we are unfreezing time. Who knows what monsters will now awaken, and what they will bring with them as they lurch to life?

I
love the Far North. For many years I made it a point to try to get somewhere in or near the Arctic during the summer. Often these trips were put together at the last minute, and never was the call more last minute or more welcome than in July 1999, when I was driving back from Cape Cod to New York with my wife, Mary, and our then very young children. It was about 100 degrees, the kids were fighting and squalling in the back, and we'd just heard from friends staying at our house in Nyack that the one working air conditioner had broken and the house was an oven. Then my cell phone rang. It was my editor at
Time,
Charles Alexander. I'll re-create the key part of the conversation from Mary's point of view as she was sitting next to me in the car.