Glaciologist Slawek Tulaczyk digs out equipment at a field camp on the Whillans Ice Stream. Flags mark items so they can be found beneath snowfall.
“Even before climate change came onto the scene, we were worried about the potential contribution to sea level of West Antarctica,” says Robert Bindschadler, a glaciologist at NASA Goddard Space Flight Center in Greenbelt, Maryland. Unlike other ice sheets, the WAIS rests on ground that sits below sea level (without ice, West Antarctica would be an archipelago). This leaves it uniquely sensitive to warming oceans. It is the only marine ice sheet to have survived beyond the last ice age, and just as scientists predicted 30 years ago, the parts of it that are shrinking are those that are raked by sea currents.
The very shape of the WAIS makes it vulnerable, says geophysicist Donald Blankenship of the University of Texas at Austin. Moving inland from the edge of the WAIS, the glacier bed plummets farther below sea level and the ice gets thicker. As the glaciers retreat inland, more and more of their ice will come in contact with warmer water, while the area on which new snow can gather will decrease—a double hit that many people think will cause the WAIS glaciers to melt more and more quickly. “Once they get short enough they’re not stable,” Blankenship says.
Another wild card lies beneath the WAIS. The sea basin that it straddles is a rift valley, a geologically active zone with volcanoes and geothermal heat accelerating the melting of ice off the sheet’s underside. That water gushes in rivers beneath the ice and collects in lakes, which periodically flood. No one knows how much that water influences slippage of the ice above it, but finding out is critical to predicting how the WAIS will respond to warming temperatures.
Tulaczyk has come to Antarctica to find out. He and Joughin (back in Seattle) will monitor changes in the Whillans Ice Stream as closely as doctors monitor an ICU patient’s vital signs. The goal is to understand how the flow of water controls ice movement.
“That’s the total holy grail right now, to see if we can pin down the response of the ice stream to lakes’ filling and draining,” says Helen Fricker of the Scripps Institution of Oceanography in San Diego. Fricker uses a laser altimetry satellite, called IceSat, to monitor these lakes as they fill and drain by measuring the rise and fall of the ice above them. But Tulaczyk and Joughin hope to gather information that no satellite could by installing GPS sensors on the ice, simultaneously measuring its vertical and lateral movements to determine the effect of water running underneath.
It is 10 p.m. on the WAIS, and sun filters through the fog like fluorescent light. In this nondescript spot 25 miles from camp, Tulaczyk connects boards on the first GPS unit. The instrument must survive conditions notorious for sapping electronics—four months of sunless winter, with temperatures down to –75 degrees Fahrenheit. A solar panel will recharge its four 70-pound batteries during summer, a wind-powered generator during winter. Every 10 seconds for the next two years, this unit will triangulate radio signals with GPS satellites overhead to measure movement of the ice to the nearest half inch.
By now we have developed a field routine: 9-hour workdays alternating with 14-hour workdays. We return to camp as late as 1 a.m., which hardly matters in the 24-hour summer light.
Back at camp we anchor our equipment in the snow with bamboo poles so it doesn’t blow away. We pee at a patch of yellow snow. At night we sleep in one-person tents and use bottles when the need arises (my bottle, issued to me in McMurdo, bears the words Karen’s pee written in black marker). We store our food in snow trenches, and in the morning we use a hacksaw on slabs of frozen egg to fry up. The temperature ranges from 5 to 15 degrees F. “It is the banana belt of Antarctica,” Tulaczyk had assured me months before our trip, but I still sleep with my laptop computer to keep its electronics from going haywire in the cold, and I must warm the icy object on my bare belly so it will start up.
We install a total of 10 GPS units, some of them atop Lakes Whillans, Mercer, and Seven, subglacial lakes that Fricker, the scientist at Scripps, discovered by satellite a few months before. Pettersson’s ice radar identifies water channels under the ice, above which we place other GPS units. The lakes and channels are undetectable by human senses, since they lie beneath half a mile of ice. Only our GPS coordinates tell us when we’ve arrived on top of them.
We ride our snowmobiles as much as 10 hours a day as we install the GPS units. Those long rides present the periods of greatest discomfort as hands, feet, and thighs gradually numb with cold—but also the best moments. The Antarctic ice, sculpted by wind into the layered texture of Monument Valley sandstone, flies past, and the snowmobile’s shocks judder and clack over ice ridges called sastrugi. The glare of sunlight turns the ice silver-gray, and at times we seem to be zooming through a desert.
By the time we make our second trip to Lake Mercer, the icescape feels as familiar to me as the hills of Northern California. We’re retracing our tracks from two days earlier. When we stop for a moment, I hop off my snowmobile and walk a few steps along the tracks.
It’s only after my right foot has sunk six inches that I begin to feel that something is wrong. Horribly wrong. My right foot sinks deeper in the snow and I shift my weight to the left. By the time I stop my leg from sinking further, it’s halfway to the knee. I pull it out and look into the hole that I’ve created. It has no bottom.
Crevasse marks cut through our tracks from two days ago, meaning the cracks have widened in just the last 48 hours.
I’m peering into a hidden world inches beneath our feet. Two crisp walls of ice drop vertically. Cold blue light seeps in. The crack, a foot or more wide, plunges 20 feet, 30 feet, and disappears into bottomless black. It’s concealed beneath a crust of snow 12 inches thick. On the surface only the faintest impression—as thin as a shoelace—trickles across our snowmobile tracks.
I share a couple of quiet seconds with this thing, staring into its maw, mostly—believe it or not—in wonder. Then I step back gingerly from its lip. “Hey, guys,” I yell. “Crevasse.” Pettersson motions us onto our snowmobiles; they’re safer, since they create a bigger footprint for distributing weight. Drive forward half a kilometer, he says. In 30 seconds we cross the mark of another crevasse, then another and another—four or five total. The marks cut through our tracks from two days ago, meaning that the cracks have widened in just the last 48 hours. Our crevasse-detecting radar missed them.
I spend the rest of that afternoon in solitude, bouncing for hours on the radar-bearing cargo sled as Pettersson drags it across the ice plain. We are measuring the contours of the landscape below. All the while, the crevasse I stepped into plays on an endless loop in my mind, often with a horrible ending: wedged in a crack without any help. That image will quicken my pulse at unexpected moments for weeks to come. But ironically, the memory of what really did happen—looking into this cold blue portal and walking away unharmed—will remain one of my most cherished from the trip.
