W Antarctica’s crumbling ice sheet to redraw global coastline

MONACO: The fate of the world’s coastal regions and the hundreds of millions of people who inhabit them depend on a block of ice atop West Antarctica on track to lift global oceans by at least three metres. It is not, according to available science, a matter of “if” but “when”.

Anders Levermann, a professor at the Potsdam Institute of Climate Impact Research in Germany and a top expert on Antarctica, spoke to AFP — days before the release in Monaco of a major UN report on oceans and Earth’s frozen zones — about how climate change is impacting the world’s coldest region.

Q. Does global warming affect Greenland and Antarctica the same way? No. In Antarctica, 99 percent of all ice loss occurs when ice slides into the ocean. There is practically no ice melt on the surface — it is simply too cold. In Greenland, half of the ice loss is due to melt water that runs into the ocean. When ice in Antarctica or Greenland slides into the ocean and becomes an ice shelf, it comes into contact with surface water. Even a tenth of a degree increase in the temperature of the water can lead to a significant ice sheet imbalance. Greenland’s ice sheet is much smaller than Antarctica’s — seven metres of sea level equivalent vs. 55 — but sheds even more mass. That is because Antarctica, even if its topography has fewer barriers, is so much colder.

Q. What do we know about Antarctica that we didn’t know a decade ago? Ten years ago the modelling of Antarctica showed no significant ice loss within this century. Indeed, there was some debate as to whether the continent might add ice mass.