MELISSA BLOCK, host:

The permanent cap of sea ice in the Arctic shrank to a record low this summer. The sea ice measured 1.59 million square miles at its lowest point. If you compare that with the previous record low in 2005, the loss of ice is an area roughly the size of Texas and California combined.

These measurements come from the National Snow and Ice Data Center at the University of Colorado, where Mark Serreze is a senior research scientist. And Mr. Serreze, you're using satellite images of the polar ice cap.

Dr. MARK SERREZE (Senior Research Scientist, University of Colorado National Snow and Ice Data Center): That's right. We use satellite imagery that we've have records of now extending back to about 1979. And what's happened this year has got us a little bit worried.

BLOCK: Is it worse than the most dire projections that you would have made?

Dr. SERREZE: Well, it seems that way. If we can look at our climate model projections, these computer projections, they're all telling us that we should be losing sea ice, that the effects of global warming are starting to emerge. But what we find is that the rate of loss is faster than any of these projections. So we're on this fast track of change. And some people have termed it that we're on a death spiral at this point.

BLOCK: And is there any question for you why this ice cap is melting at the rate that you're seeing?

Dr. SERREZE: Yeah. What we've seen is that we've had a rather pronounced loss of sea ice over the past 30 years. And it's inescapable at this point that we're seeing the effects of global warming, of greenhouse gas emissions. Now, we always know in any particular year, we can sight aspects of natural variability in the system. But 2007 really sets an exclamation point on this. And I think it's reasonable to think that we could lose that summer sea ice cover as early as the year 2030.

BLOCK: You mean, lose it completely?

Dr. SERREZE: Lose it completely. Now, we'd always have some sea ice in the winter because, of course, even in a greenhouse-warmed world, there's going to be winter in the Arctic, but it will be fairly thin ice. So it may even be within our lifetimes, certainly within our children's lifetimes that we lose either most or all of that cover in summer.

BLOCK: You know, I was up in Northern Alaska this summer, reporting on climate change, and every one there would talk about the loss of ice, ice coming later, ice being thinner. And what are the effects that you would project from this dramatic shrinkage that we're seeing?

Dr. SERREZE: Well, certainly, we're going to see a lot of impacts on the Arctic. I think everyone's well aware of the plight of the polar bears because they depend on that sea ice for their livelihood. But one of the other things you're going to see is a lot more activity in the Arctic.

As you're probably aware, there's been this mad rush of different countries, the Russians, the United States, the Canadians, the Danes to try and claim their piece of the Arctic pie because it's now becoming much more accessible. There's oils, there's minerals at the bottom of the Arctic Ocean, and those countries that want to get at that.

One of the things we saw this year, of course, was the opening of the fabled Northwest Passage. So you could take a ship loaded with Toyotas right from Tokyo, across the Arctic Ocean into New York, if you wanted to. Now, those are impacts on the Arctic itself. But the thing that we're just trying to get a handle on now is how that loss of sea ice can affect weather patterns elsewhere, such as in the United States.

We think of the Arctic as this refrigerator of the Northern Hemisphere climate system. But what we're doing, by losing that ice, is radically changing the nature of that refrigerator. But everything is coupled together, so what happens up there can eventually influence what happens down here.

BLOCK: Hmm. There's the cyclical effect of all of this, right? The less sea ice there is to reflect sunlight back into space, the more warming there will be, the more melting there will be.

Dr. SERREZE: Yes. Yes. That's exactly true. It's what we call an albedo feedback. Albedo is just a fancy word for the reflectivity of the surface. And of course, sea ice is white, that as we start to lose that sea ice, we start to lose that whiteness. And so it seems that that feedback is really starting to kick in now. And it probably has a lot to do with explaining why we've had these very large ice losses in recent years.

BLOCK: So you would expect next year, you would see another dramatic shrinkage?

Dr. SERREZE: We're certainly set up that way. We've got so much open water in the Arctic right now that the ocean has absorbed a great deal of heat in summer. So now, the ice that grows back this autumn and winter is going to be thinner than it used to be, will have less ice by the beginning of next spring. And so we'll have already set ourselves up for a big loss next year. Just how much of a loss we're going to get, we're not quite sure. But this is part of a long-term change that we're seeing. And it's not clear how we're going to stop it.

BLOCK: Okay. Mark Serreze is a senior research scientist with the National Snow and Ice Data Center at the University of Colorado in Boulder. Thanks very much.

Dr. SERREZE: Sure.

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