Given the extreme costs and dangers of putting boots on the ice, much Antarctic research these days is done with satellites. But satellite monitoring is a young science, which presents limitations. When Bindschadler, the NASA Goddard glaciologist, wanted to study how the WAIS had changed over decades, the problem was that decades ago few satellites had orbited over the area. Bindschadler’s research led him to an archive of newly declassified spy satellite photos from the cold war. Among them he found two images taken by one of the CIA’s Corona satellites on October 29 and October 31, 1963. These satellites, launched to monitor Soviet military movements, captured photos on massive spools of film that were parachuted back to earth and snagged in midair by U.S. planes.
A comparison of these photos with images from 1992 revealed surprisingly rapid changes: the Whillans Ice Stream had widened by 2.5 miles and had eroded 10 miles off a wedge of slow-moving ice to the north called Engelhardt Ridge.
Even people using modern satellites to monitor ice suffer from a lack of options. Due to competing scientific priorities, few NASA satellites are optimally designed to monitor the earth’s polar ice, and those that are sometimes hit snags. The IceSat satellite, which Fricker uses to monitor subglacial lakes and which others use to monitor the sagging tops of melting glaciers, can function only 66 days per year due to a technical glitch.
Scientists also face shortfalls in other satellite functions that they need for monitoring the Antarctic ice: high-frequency radar for measuring the speed of glaciers and low-frequency radar for measuring ice thickness. “It’s a major impediment to developing realistic ice sheet models when you don’t even know how thick some of these outlet glaciers are,” says Eric Rignot, a remote-sensing glaciologist at the NASA Jet Propulsion Laboratory in Pasadena, California. Even NASA’s gravity-sensing GRACE satellites, which have provided stunning ice mass data since their launch in 2002, are nearing the end of their planned life. “This is probably the best method to look at mass changes of ice sheets if you want to get a number that you can trust,” Rignot says.
In February 2008 NASA announced its satellite missions for the next decade. They include a new IceSat satellite, but it won’t come online until years after the expected end date of the one it is replacing. NASA also has plans for new gravity-sensing satellites, but not for a decade or more—well after the current GRACE mission has ended. “We’re definitely going to have an instrument gap,” Fricker says. “We’re going to be blind for a while.”
That blind spot comes at a time when ice sheets in West Antarctica and Greenland are changing more quickly than anyone expected. Glaciologists would like to know what’s happening. The shortage of satellite coverage underscores the need for field projects like Tulaczyk’s and Joughin’s to succeed.
My nylon tent roars in the wind, nearly flattening to a trapezoid with each gust. Katabatic winds, caused by cold air accelerating as it slides off the polar plateau, have battered us for 36 hours. I have hardly slept.
I kick at the wall of the tent to break away a shell of ice and slip outside with Karen’s pee bottle in hand. As I stumble through blowing snow, the ghost of a bamboo flagpole looms into view. We planted these flags the previous day to mark the route to the cooking tent, for which I’m thankful. I turn my back to the wind, look up, and despite the whiteout I see a circle of blue sky directly above—the quintessential sign of an Antarctic storm. Very little new snow is actually falling; most of it is being redistributed, wind-blasted off the ice or blown off the Transantarctic Mountains 40 miles away.
The storm gives way to an afternoon of digging cargo sleds and food out of the snow. A flag marks the location of each object; 47 of them flap and clap nonstop. The morning after that day of digging, Tulaczyk, Pettersson, and I depart for what we expect to be our toughest day—following a serpentine route to place a GPS unit near heavily crevassed ice, 30 miles away. We anticipate a 10-hour ride, slow and roped together, but after only 30 minutes I begin to glimpse the telltale marks of covered crevasses. We slow down and Pettersson stands on his snowmobile to scan the snow ahead. A minute later he raises his hand for us to stop. He dismounts, plays out some rope, and slides an avalanche probe into the snow to check for crevasses. Jab after jab, the probe sinks easily to the hilt.
Pettersson announces the verdict: A buried crevasse, 10 feet wide, blocks our path. It is covered by just two feet of fragile snow. The gentle slope of the ice predicts bigger cracks ahead. Despite months of planning, our day is over. We turn around.
Over the next several days, we install the last GPS units, one of them near the crevasse that I stepped into and another near the 10-footer that stopped us. The crevasses are interesting, Tulaczyk says, because they mark spots where, half a mile below, the ice grinds over a high spot in the underlying rock—sort of a thorn in its belly. The ice stretches over these sticking points twice per day as the tide lifts up and sets down the Ross Ice Shelf, a 1,100-foot-thick slab of ice the size of Spain that hangs over the ocean several hundred miles away. “You could actually get daily cycles of opening of these cracks,” Tulaczyk says.
Our time in the field ends with a day spent chipping our sleeping tents out of the ice that clings tenaciously to their edges, and digging the cooking tent out of drifts as deep as six feet.
As planes ferry us back to McMurdo on the first leg of our trip home, Tulaczyk and Pettersson open their laptops at every opportunity to peek at the data they’ve collected so far. The GPS stations have tracked the movement of the Whillans Ice Stream and confirmed a curious fact: The Whillans sits still most of the time. Twice per day it lurches into motion, slipping 18 inches forward across its entire 5,000-square-mile expanse. That slip corresponds to ocean tides lifting up and setting down the Ross Ice Shelf. (The Ross acts as a brake that holds the ice sheet back; its tension is released at these twice-daily moments.)
The seismometers that we planted show the curvy peaks of ice quakes occurring each time the glacier lurches. Several months after we return home, another team will report in the journal Nature that these twice-daily ice quakes measure a staggering magnitude 7—strong enough to topple cities and kill thousands if they were to happen in a populated area. Only because the quakes occur in slow motion were we not tumbled out of bed every morning during our stay on the ice sheet. Tulaczyk’s own calculations put them at a more modest magnitude 4, still large enough to jostle jars of honey off kitchen shelves in Los Angeles or San Francisco.
The bigger questions that brought Tulaczyk to Antarctica will take longer to answer, but the ice sheet already seems to be cooperating. Shortly after we return to California, the GPS unit on Lake Mercer will start to report—via satellite link—that the ice is rising, a sign that the lake is filling with water. At some point the lake will bloat past its holding capacity and issue forth a subglacial flood [pdf]. Tulaczyk’s and Joughin’s sensors will report whether the ice sheet suddenly speeds up when that happens.
Tulaczyk and Joughin should start to see within two years how water controls movement of the ice. That information will feed into models that tell us how the WAIS will fare in the next 100 years and whether its glaciers are capable of a massive speedup, as some people fear.
“We have the technology” to predict the ice sheet’s fate, Tulaczyk says as we chat in a quiet corner of McMurdo’s dining hall a few hours before leaving Antarctica. “The commitment to invest the money is the limiting factor.”
As we sit there, exhausted, my mind wanders. In a few minutes I’ll head to my dormitory and take my first shower in a month. Then I’ll catch an hour of sleep before boarding a 2 a.m. flight on a military cargo jet back to New Zealand—December 21, last flight before Christmas. Twelve hours from now I’ll walk the streets of Christchurch and revel in things that I haven’t experienced in six weeks: sunset, stars, living things, the color green—and hot Indian curry.
For eons our species and its ancestors have lived according to the faraway rhythms of the WAIS as it expanded and collapsed time and again, helping to drive sea levels up and down around the world. Only now is humanity exploring this remote area that affects its fate.
“Many of the places we went have probably never been crossed by people,” Tulaczyk says. His beard is full and his skin darkened by the ultraviolet rays that glaciologists come to expect from working on a reflective ice sheet in 24-hour sunlight. “Almost every time you make measurements on the ice, something really new pops up,” he says. “That’s part of why people put up with this type of work.”
A quarter-inch crack indicates the location of a crevasse. An avalanche probe showed that the underlying crevasse, hidden beneath 2 feet of snow, is ?10 feet wide.