Scambos and Skvarca tracked UK211 for eight months, communicating with AMIGOS by satellite phone. The berg, originally 10 by 12 kilometers, slowly shrank by half. Then, on November 23, 2006, AMIGOS phoned home for the final time. A few days later UK211 was gone, sending AMIGOS to the bottom of the sea.
UK211 underwent many changes, but the one that immediately preceded its sudden demise was the melting of snow that transformed the berg's surface into waterlogged slush. The meltwater may have percolated into the berg's interior and destabilized it, Scambos says. But the experiment did not show him the moment of disintegration—only what led up to it. And because UK211 was a free-drifting berg, not an ice shelf, Scambos could not quantify how glaciers feeding into the berg would respond.
Trapped Glaciologists Find a Way
Those questions led Scambos to join a difficult but critical expedition in 2010 to a remnant of Larsen B called the Scar Inlet ice shelf. A laser altimeter onboard the ICESat satellite had documented the thinning of glaciers feeding into Larsen B and Scar Inlet—as indicated by lowering of the ice surface—but the altimeter had fizzled out earlier that year. Interferometric synthetic-aperture radar measurements from other satellites had provided long-term averages of how quickly glaciers behind ice shelves like Scar Inlet were flowing into the sea, but the technique would not capture sudden events like glacier surges. Since 2003 the GRACE satellites had measured ice loss through variations in the earth's gravitation but only at the fuzzy resolution of hundreds of kilometers.
Scambos expected the Scar Inlet ice shelf to collapse within a few years, and he wanted to plant an array of sensors on the ground there to capture the cataclysm. “We want to watch this process from the very beginning and in greater detail than what we've seen from satellites,” he told me in 2010, as we sat indoors on the Nathaniel B. Palmer, a 6,000-metric-ton icebreaker that serves the U.S. Antarctic Program. “We want to see the big show at the end.”
For 57 days in January and February 2010, the Palmer plowed along the peninsula toward Scar Inlet, ramming through seasonal sea ice up to two meters thick. Scambos and two dozen scientists onboard had hoped to get close enough to fill in critical blind spots in their knowledge. They ran into trouble only days into the expedition, however. Severe sea ice, pushed up against the peninsula by ocean currents and winds, prevented the Palmer from getting within easy helicopter range of Scar Inlet. So, on January 26, Scambos was dropped off at a British research station with four other glaciologists, including Martin Truffer and Erin Pettit of the University of Alaska Fairbanks. From there a Twin Otter plane delivered them to their first field site. The team spent three weeks hopping by plane between the Scar Inlet ice shelf and the glaciers feeding into it.
On days when snowstorms subsided, the researchers installed AMIGOS on Scar Inlet and on the lower reaches of Flask Glacier (and they plan to install another AMIGOS on the lower Leppard Glacier in 2013). Higher up on Flask and Leppard, they installed simpler meteorological and GPS stations. On a coastal bluff overlooking Scar Inlet, they mounted a steerable camera.
Scambos's team members encountered unexpected conditions on the Scar Inlet ice shelf. When they dug in and around camp, their shovels plunged into empty voids—crevasses in the ice veiled under thin crusts of snow. One day the plane's pilot sunk up to his waist in another hidden crevasse. Those cracks may have previously been buried under thicker snow, but hot summers had melted it away, bringing the cracks to the surface—just as Brückner and his Argentine soldiers had seen in the last days of Larsen A.