Durban - There is now no doubt that Antarctica’s ice sheet is melting – and the melting is accelerating.
Researchers said this could become a “runaway problem”, ultimately raising global sea levels by 6m or more.
While Antarctica’s ice sheet has accumulated ice in the east, research that “weighed” Antarctica’s ice sheet has shown that the western section was melting twice as fast as was thought and that the melting of the ice cap was speeding up.
Researchers at Princeton University, in the US, found that the ice lost between 2003 and last year amounted to 92 billion tons a year. They said, if this were stacked up on the 60km2 island of Manhattan, it would be more than 1.6km high.
Christopher Harig, one of the researchers, said most scientists would be hard-pressed to find reasons other than human-made climate change as the reason for the rapidly accelerating rate of melting ice. In Antarctica it is the warming oceans that causes the ice to melt, rather than warmer air temperatures. As floating ice shelves melt, they can no longer hold back the land ice.
Harig said the accelerating melting of the western part of Antarctica was “a big deal” because of the implications for global sea-level rise.
“It really has the potential to be a runaway problem. It has come to the point that, if we continue losing mass in those areas, the loss can generate a self-reinforcing feedback whereby we will be losing more and more ice, ultimately raising sea levels by tens of feet,” Harig said.
Antarctica’s overall ice loss amounted to 6 billion tons each year during the 11-year study period. But in the western part, the ice loss grew by 18 billion tons a year, every year.
The Princeton University study, published in Earth and Planetary Science Letters, differed from others in that it measured the mass of ice rather than the volume.
Co-researcher Frederick Simons said while the ice-sheet’s volume – how much space it takes up – was important, this could change without affecting the amount of ice that was present.
Ice compacts under its own weight, and when lasers were bounced off the ice surface to determine its volume, there appeared to be a reduction in the amount of ice. But mass, or weight, changed only when the ice was actually lost.
Simons said the difference between measuring ice volume and ice mass was like a person “weighing” himself by looking in the mirror only, and not by standing on a scale.
He warned that there would not be much more of this kind of research because the Grace (gravity recovery and climate experiment) satellites that collected this data were “on their last legs”.
The Mercury