Antarctic Ice Sheets Are Collapsing -- But When Will Sea Levels Rise?

Yesterday, newly-published scientific evidence revealed that the west Antarctic ice sheet is "collapsing." In fact, this ice melt is pretty much inevitable, and will mean up to 4 inches of sea level rise. What most news stories left out, though, was the timeline for this change to our shorelines.

Writing at DotEarth, environmental journalist Andrew Revkin cautions that we need to remember that the situation is dire, but the timescales are long:

Sometime between 200 and 900 years from now the rate of ice loss from this glacier could reach a volume sufficient to raise sea levels about 4 inches (100 millimeters) a century. At that point, according to the paper, ice loss could pick up steam. But in a phone conversation, [paper author] Joughin said the modeling was not reliable enough to say how much, how soon.

"Collapse is a good scientific word," he told me, "but maybe it's kind of a bad word" in the context of news. There's more on this work in a well-written news release from Joughin's university.

NASA has posted a heap of helpful context and description of the Geophysical Research Letters paper, written by Eric Rignot at the University of California, Irvine, and collaborators.

Rignot also acknowledged the problem with the word "collapse" in a conversation with Revkin:

Collapse in the imagination of most people sounds like a catastrophic event that is going to happen in the next few years. We are talking about a retreat that is unstoppable because we think we have enough evidence to say that these glaciers will keep retreating for decades and even centuries to come…. We're talking about a slow degradation of ice in this part of Antarctica.

They key takeaway here is that this degradation is unstoppable. There's nothing we can do to prevent hundreds of years of melt. We won't see it in our lifetimes, but we've irrevocably altered the Earth's coastal ecosystems.

To understand the full complexity of the situation, Revkin recommends "The 'Unstable' West Antarctic Ice Sheet: A Primer."