Rapid Antarctic Ice Sheet Melting May Double Sea Level Rise In A Hundred Years

Researchers from the University of Massachusetts Amherst and Pennsylvania State University have shown in a new study that sea levels might be shooting up much faster than expected. The rise in the sea levels in the next century might be double the estimates arrived at so far.

"This could spell disaster for many low-lying cities," said Robert DeConto, co-author of the study. "For example, Boston could see more than 1.5 meters [about five feet] of sea level rise in the next 100 years. But the good news is that an aggressive reduction in emissions will limit the risk of major Antarctic ice sheet retreat."

Studying previously known climate mechanisms that had not been integrated into ice-sheet models, scientists looked at the effects of surface melt water on the breaking of ice shelves and ice cliffs.

The fear is that Antarctica might offer more than one meter of sea level rise by 2100 and more than 15 meters by 2500 if atmospheric emissions are not controlled.

Using novel processes in the three-dimensional ice sheet model, the team examined the sea-level rise estimates and posted them against earlier levels of the sea as well as the retreat of the ice.

"Ocean-driven melt is an important driver of Antarctic ice shelf retreat where warm water is in contact with shelves, but in high greenhouse-gas emissions scenarios, atmospheric warming soon overtakes the ocean as the dominant driver of Antarctic ice loss," the team wrote.

After the loss of ice, the long thermal memory of the ocean could prevent the recovery of the ice sheet for many millennia once the greenhouse-gas emissions are reduced.

"Today, summer temperatures approach or just exceed zero degrees Celsius on many shelves, and due to their flat surfaces near sea level, little atmospheric warming would be needed to dramatically increase the areal extent of surface melting and summer rainfall," the researchers said.

"If protective ice shelves were suddenly lost in the vast areas around the Antarctic margin where reverse-sloping bedrock (where the bed on which the ice sheet sits deepens toward the continental interior, rather than toward the ocean) is more than 1,000 meters deep, exposed grounding line ice cliffs would quickly succumb to structural failure as is happening in the few places where such conditions exist today," they warned.

The findings were published in the March 30, 2016, issue of Nature.