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Warmer summer surface temperatures are melting more ice on Antarctica ice shelves. Standing water ponds leak into cracks and increase the odds of collapse, according to a new study published by American scientists, including Ted Scambos of the National Snow and Ice Data Center. The team focused on the Larsen Ice Sheet, which has experienced major retreats in 1995 and 1998.
The team used satellite images of meltwater on the ice surface and a sophisticated computer simulation of the motions and forces within ice shelves. The results indicated that added pressure from surface water filling up the cracks and crevasses can completely crack ice shelves, causing portions to float away and eventually melt.
"The result implies that other ice shelves are closer to the breaking point than we previously thought," said Scambos. "The shelf retreats that have occurred so far have had few consequences for sea-level rise, but breakups in some other areas like the Ross Ice Shelf could lead to increases in ice flow off the Antarctic and cause sea level to rise."
Floating ice shelves, which account for about 2 percent of Antarctic ice, typically undergo cycles of advance and retreat over many decades. While scientists have known that meltwater fills crevasses and enlarges the cracks, this is the first study to explain the physics linking ice-shelf viability and meltwater ponds.
"The findings provide a solid link between climate warming and the recent extensive disintegration of some Antarctic ice shelves," said Scambos. "The process can be expected to be more widespread if Antarctic summer temperatures continue to increase." Regarding the Ross Ice Shelf, Scambos says, "If we begin to get significant water ponding there, and the shelf is eventually destroyed, we would likely have ice pouring off the Antarctic at a much faster rate, from the land ice held back by the ice shelves. That would increase sea level significantly."
