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Ice sheet in Antarctica has melted past ‘point of no return,’ NASA says

May 12, 2014 at 6:38 PM EDT
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JUDY WOODRUFF: Scientists have long been warning of the risks posed by melting ice sheets. But a study released today offers the most definitive word yet from NASA and other researchers that parts of the ice sheet in the West Antarctica are melting, a pattern they say is now irreversible.

Eventually, scientists say, it will lead to rising sea levels. The study finds that a series of glaciers in the Amundsen Sea have — quote — “passed the point of no return” and are draining into the water, with faster-melting levels shown in red. One is shown here in time-lapse footage. And some of these glaciers have been retreating more than a mile a year between 1996 and 2011.

The collapse of the ice sheet will take more than a century to play out, but the new estimates captured international attention today.

NASA’s Tom Wagner is one of the lead members of the team. And he joins us right now.

Tom Wagner, welcome to the program.

THOMAS WAGNER, NASA: Thank you.

JUDY WOODRUFF: So, remind us, why do you pay attention? Why should one pay attention to what’s going on in Antarctica, this ice sheet?

THOMAS WAGNER: Because it’s one of the most important places on Earth for understanding sea level rise.

And right now around the world, sea level is rising by three millimeters a year.

JUDY WOODRUFF: But it’s been expected that there was going to be melting, there was going to be sea level rise. What’s different about what you have reported today?

THOMAS WAGNER: What is different is this.

We kind of almost think of the ice as going into the ocean in a steady-state way. But now what we have is evidence of kind of a jump. And what is happening literally is that we’re seeing the ice retreat off the points that it was grounded on into a deeper interior that can allow it to really speed up.

JUDY WOODRUFF: And do you know why this is happening?

THOMAS WAGNER: We know why, in that we know that it’s warm water that is coming from deep parts of Antarctica and getting blown up on to the continental shelf and under this ice and causing it to melt.

JUDY WOODRUFF: And what’s causing that water to be warm and causing it to move in the direction it is?

THOMAS WAGNER: So, around Antarctica, the circum-Antarctic deep water is actually warmer than the surface water, which is very cold.

And the general idea is that probably winds that have changed their patterns because of global warming, coupled also with the ozone hole over Antarctica, have led stronger wind patterns around Antarctica.

JUDY WOODRUFF: And how confident are scientists that that’s the cause, that that’s behind it?

THOMAS WAGNER: Pretty confident, in that — and one thing you have to understand is this release today — and there were actually two studies that came out — this idea has been talked about since the 1970s.

And the whole scientific community has been working on this for a long time, not just these studies with satellites, but ships that have gone to the area and actually measured the water temperatures have actually even gone out and made a hole along with the National Science Foundation in one of the ice shelves.

JUDY WOODRUFF: So, you said you found out that certain things have happened and they are happening at a faster rate. Give us sort of a tangible example about it. Help us understand what exactly is going on there.

THOMAS WAGNER: Sure.

If you went to Antarctica and pulled the ice off, in the region of West Antarctica that we just looked at, you actually wouldn’t see land under there. What you would see is ocean and a few islands popped up. And that’s what makes this ice so at risk for rapid loss.

But the ice so thick that it displaces all the water and kind of sits down on the bedrock. But what’s happened is that it’s retreated away from its coastal area. And as it retreats and thins, it is supposed to float on that water, and that allows it to speed up and flow more rapidly into the ocean.

JUDY WOODRUFF: So, looking at consequences, what do you project? What do you see?

THOMAS WAGNER: So the modeling study that came out today in “Science” actually says that we could, within the next century, jump up from, say, a quarter of a millimeter a year out of this one glacier to over a millimeter a year. That’s one of five glaciers that are just in this area, and this is just one small area of Antarctica.

JUDY WOODRUFF: So, that sounds like not very much, from a quarter of a millimeter to a millimeter.

THOMAS WAGNER: Right.

But when you run out some of the models, right, say, like in 100 years from now, in the New York alone in the last 100 years, we have seen over a foot of sea level rise, OK? And that sea level rise is already damaging things all up and down the East Coast.

JUDY WOODRUFF: Right.

THOMAS WAGNER: The next century, we’re looking at maybe three-feet-plus. When we include these kinds of factors, we might have to revise that estimate upwards, maybe four, maybe five, maybe more, and that’s kind of the cutting edge of the research right now.

JUDY WOODRUFF: So, what — can you say what populations, what cities, what parts of the world we’re talking about? Who is affected by this?

THOMAS WAGNER: In Bangladesh, a foot-and-a-half of sea level rise displaces 11 million people. OK? It’s that serious.

All around the world, most of our cities are built on ports. The ports are right at sea level. And the thing is, you don’t just think about it like, oh, my beach — my house is four feet above sea level.

Well, the problem is during a storm surge or something else, you get additional problems. So small amounts are really impactful.

JUDY WOODRUFF: And when the report says this is irreversible, what does that mean?

THOMAS WAGNER: OK.

This was the fascinating part of this research. Because that part of Antarctica — typically, we think of a continent, you think of like the United States. The ocean is here and the continent goes up like this. In Antarctica, the continent is down below sea level, and the ice is really thick on it.

What happens is that, as the ice retreats in, it begins to float, because there’s no continent for it to pull up on. OK? And that’s what makes this so risky and why it can flow into the ocean and collapse so rapidly.

JUDY WOODRUFF: But does that literally mean there’s nothing that humans can do to slow this down at this point?

THOMAS WAGNER: Tough call.

And, again, that does kind of get to the cutting edge. What we know is this. Based on the basic physics and the geometry, the shape of the bed in that area, this should continue to retreat, unless there is some wildly different thing, such as there is no warm water entering this part of Antarctica.

JUDY WOODRUFF: Why do you say that’s a wild thing?

THOMAS WAGNER: Well, you would have to really fundamentally change ocean circulation and atmospheric circulation.

JUDY WOODRUFF: And that’s not something that you’re saying most any — that humans are capable of doing right now?

THOMAS WAGNER: No.

And, listen, I’m not saying you should run screaming from the beach right this moment because of the wave of water is coming. What I’m saying is, we’re actually doing pretty well at kind of closing the sea level budget, and getting to a point where we can really project into the future about how things are going to change.

And I feel like, sometimes, when people hear about climate change and sea level rise, they think it’s all based on these computer models that probably have these big uncertainties. One of the key studies that came out today, this is based on observations, right, actually looking at how these glaciers are changing and speeding up.

JUDY WOODRUFF: So, it’s not some projection, some mathematical model?

THOMAS WAGNER: No, with a lot of uncertainty.

This is, like, aircraft have gone and flown over and put radar signals down that measured the rock under the ice and where it is.

JUDY WOODRUFF: Well, Tom Wagner, you have left us all unsettled.

(LAUGHTER)

JUDY WOODRUFF: Thank you very much.

THOMAS WAGNER: Thank you for having me.