A new study by researchers from the University of Massachusetts Amherst and Pennsylvania State University suggests that sea levels might be rising faster than we expected, with the results revealing that recent estimates of future sea level rise over the next 100 years might be almost two times lower than the real number.
"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."
The team took previously known climate mechanisms that were never incorporated into ice-sheet models and integrated them into their research in order to consider the effects of surface melt water on the break-up of ice shelves and collapse of vertical ice cliffs.
The results found that Antarctica could provide more than one meter of sea level rise by the year 2100 and more than 15 meters by 2500 if we don't get atmospheric emissions under control.
Using new processes in the three-dimensional ice sheet model, the team revised the sea-level rise estimate and tested it against past times of high sea levels and ice retreat.
"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, adding that when enough ice is lost, long thermal memory of the ocean will prevent the recovery of the ice sheet for thousands of years after greenhouse-gas emissions are decreased.
Previous models of Antarctic ice sheet vulnerability focused on the role of the ocean melting floating ice shelves from below, overlooking the fact that major ice shelves in the Ross and Weddell Seas, as well as smaller shelves and ice tongues, are also at risk of succumbing to atmospheric warming.
"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 issue of Nature.
