Warming to speed icesheet collapse by 100,000 years: study

Terra Daily, via Agence France-Presse: Manmade climate change is set to hasten the disintegration of a massive ice sheet in Antarctica by 100,000 years, boosting sea levels some five metres (16 feet), according to a pair of studies published Thursday. The research, which matches new ice core data with a simulation of past and future changes in the West Antarctica Ice Sheet (WAIS), reveals for the first time regular cycles of "catastrophic collapse" and reformation reaching back five million years.

Cycles lasted 40,000 years during the first three-fifths of this period, but have since more than doubled in length, explained David Pollard, a scientist at Pennsylvania State University and lead author of one of the studies. "But with global warming we are cutting short a natural cycle," he told AFP by phone. "The two studies combined show it is really likely that the WAIS will collapse in the next few thousand years. In the absence of human influence, it would probably happen only 100,000 years from now," he said.

…The findings showed a geological metronome of massive change across five million years, and provided the first direct evidence of total collapse. "Before there were hints of it collapsing like that, but we really didn't know until now," said Pollard, a co-author of the study, published in Nature. The new data also confirmed that the cycles of ice destruction and formation are closely linked to shifts in the tilt of Earth's axis as it rotates around the Sun, a process called obliquity.

…In the second study, Pollard and Robert DeConto of the University of Massachusetts in Amherst simulate Antarctic ice sheet variations in a mathematical model over the past five million years in order to track the "grounding line", the shifting border between land and sea ice. "We found that the dominant mechanism attacking the West Antarctic ice has been variations in ocean melting under its large floating ice shelves," rather than changes in temperature or surface melt, Pollard said….

The Bay of Whales, Antarctica, shot by P Bond (Pbkiwi), who has generously released the image into the public domain