Air Date: Week of June 19, 1998

Some climate researchers now say global warming will alter weather patterns and ocean currents in the years to come. And with severe consequences. One focal point of their concerns is in Antarctica, where they say part of the continent's ice cap will melt and raise sea levels. A recent article in the British journal "Nature" concludes the threat is real. Living on Earth's Daniel Grossman has our story.

Transcript

KNOY: Some climate researchers now say global warming will alter weather patterns and ocean currents in years to come, and with severe consequences. One focal point of their concerns is in Antarctica, where they say part of the continent's ice cap will melt, dramatically raising sea levels. A recent article in the British journal Nature concludes the threat is real. Living on Earth's Daniel Grossman has our story.

GROSSMAN: The article is the first attempt in more than a decade to bring together scientific research from climatology, oceanography, and glaciology, to predict the impact of global warming on the west Antarctic Ice Sheet, the western side of the South Pole's glacial cover. If the ice sheet melted, it would release enough water to raise sea level by 14 to 20 feet, flooding low-lying areas like Bangladesh, southern Florida, and many of the world's largest cities.

OPPENHEIMER: It would basically mean the end of coastal civilization as we know it.

GROSSMAN: That's the article's author Michael Oppenheimer, an atmospheric scientist at the Environmental Defense Fund. He says global warming could bring on this catastrophe, but not in the way you might imagine. The threat comes not from warmer air, but from ocean currents. To understand why, it's necessary to learn a little glaciology. The west Antarctic Ice Sheet is a hunk of ice larger than Alaska anchored to a bedrock base. It doesn't float, but around much of its perimeter are floating tongues of ice sticking out into the sea, called ice shelves. Now imagine this land-based ice sheet is the sauce on top of a hot fudge sundae. Ice streams flow toward the ocean, depleting the ice sheet, the same way fudge dribbles down a sundae into a puddle in the bowl. Michael Oppenheimer says the ice shelves significantly control how fast the ice streams move.

OPPENHEIMER: The ice shelves are jammed up against the coast of Antarctica, and that's buttressing the land-based ice. And should the ice shelves disintegrate, that could cause the land-based ice to slide into the ocean.

GROSSMAN: And recent research shows the ice shelves are at risk of disintegrating. Changing patterns of precipitation expected with global warming could alter the ocean's network of deep currents, bringing more warm water to the South Pole. Michael Oppenheimer.

OPPENHEIMER: Warming over the next century could lead to the disintegration of the ice shelves, which would then over the succeeding 5 to 7 centuries lead to a loss of most or all of the land-based ice.

GROSSMAN: But Dr. Robert Bindschadler, a leading glaciologist at NASA, says Michael Oppenheimer might be overstating his case, since it's not only the ice shelves that keep the ice sheet in check.

BINDSCHADLER: Because he has focused on the buttressing force and tended to ignore the frictional forces at the base of the ice sheet, the numbers may not in fact be correct.

GROSSMAN: Michael Oppenheimer agrees other forces are at work and could hold the ice sheet back. But he says as an environmental advocate, he'd rather be safe than sorry.

OPPENHEIMER: It may turn out in the end that the ice shelves weren't important at all. But I don't think, from today's perspective, that we'd be very safe in saying that.

GROSSMAN: And given science's sometimes glacial pace, Dr. Oppenheimer says the ice sheet may be irreversibly headed for destruction by the time scientists understand how it works. For Living on Earth, I'm Daniel Grossman.