Two forthcoming reports on the western Antarctic ice sheet confirm previous fears that the ice's melt will increase ocean levels by as much as 13 feet within the next few centuries. They also suggest that the process has already begun — and is likely not reversible. 

The New York Times reports that both papers — one by NASA scientists, to be published in Geophysical Research Letters, and one by University of Washington scientists to appear in Science  — find that the West Antarctic ice sheet is melting because of naturally-occurring warm water welling up from deep in the ocean.

NASA shows their findings in a video.

None of this is surprising to those paying attention to the state of the West Antarctic, per the Times, which reports that the late Dr. John H. Mercer predicted the unstoppable melt back in 1978: 

The basic problem is that much of the West Antarctic ice sheet sits below sea level in a kind of bowl-shaped depression [in] the earth. As Dr. Mercer outlined in 1978, once the part of the ice sheet sitting on the rim of the bowl melts and the ice retreats into deeper water, it becomes unstable and highly vulnerable to further melting.

Now, scientists are saying that the situation in the Antarctic has passed a crucial threshold. "There's no stabilizing mechanism," said Dr. Ian Joughin, lead author of the paper slated to appear in Science. Even if if the melt rate was too slow, it would be "too little, too late to stabilize the ice sheet," he adds. And NASA's Thomas P. Wagner said "this is really happening. There's nothing to stop it now."

According to Wagner, at this point our only saving grace is time, and the laws of physics: "you are limited by the physics of how fast the ice can flow." Another NASA scientist, Eric Rignot, emailed a statement on the subject to Bloomberg, saying

The collapse of this sector of West Antarctica appears to be unstoppable... This sector will be a major contributor to sea level rise in the decades and centuries to come.

The scientists add that just because the melt appears irreversible, it doesn't mean that ocean levels will rise to a crisis level in the near future. The ice sheets melt rate is expected to remain more or less stable for the next century, and is unlikely to hit dangerous speeds until about 1,000 years from now. Science writer Andy Revkin, who runs the Dot Earth blog for the New York Times, comments that the word "collapse," used by many media outlets in relation to the Western Antarctic, is not the right way to describe the phenomenon. 

Scientists say that climate change is causing more forceful winds, which in turn are bringing deep, warm water closer to ice sheets. But climate change isn't the only thing causing the melt. According to researchers, the ozone hole above Antarctica (we're responsible for that one, too) is also contributing to the speedy deterioration. It's also possible that some naturally occurring changes in climate are contributing to the situation. But mostly, it's our fault and it's not turning back. What do you think, Jared Leto?