When Antarctica Melts, U.S. Cities Will Be Swamped

Antarctica holds 90% of the world's ice and 70% of its freshwater. Its average temperature has increased nearly 5 degrees (F) in the last half century. Floating ice shelves account for about 11% of the area of the continent, and while the loss of these ice shelves does not increase sea level, they effectively act as corks to hold back glaciers. Significant melting of Antarctica's glaciers -- which have been moving more rapidly toward the sea -- could increase sea levels as much as 20 feet worldwide.

The Antarctic Peninsula, which juts toward South America and is one of only two masses of land on the continent outside the Antarctic Circle, has been warming markedly. Vast portions of its Wilkins Ice Shelf disintegrated in 2008 and 2009 after 1,500 years of stability.

Photo: Sebastian Copeland, “Antarctica: A Call to Action”

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While the sea-level rise from a total collapse of the West Antarctic ice sheet would not be as dramatic as previously estimated, it would still be enough to swamp U.S. coastal cities, according to a new study.

Because the collapse of the ice sheet would alter the gravitational pull on water unevenly across the globe, North America would see the largest sea-level rise of any region -- about 11 feet -- though impoverished, low-lying nations like Bangladesh may well be more drastically affected.

In April, an ice bridge holding the Connecticut-sized Wilkins Ice Shelf in place broke up, leaving the stability of that Antarctic ice shelf in jeopardy. That report came on the heels of a U.S. government report stating that Antarctica is melting much faster than had been previously reported.

The U.S. Geologic Survey report, prepared in collaboration with the British Antarctic Survey, should dispel the lingering myth that Antarctica is unaffected by global warming, or that a lack of melting there somehow means global warming isn't real. While some parts of Antarctica have experienced snow and ice build-up in recent years, a growing body of research shows that the ozone hole is a primary reason, and that much of Antarctica is in fact responding to global warming just as expected: by melting.

Not only are Antarctica's glaciers melting more rapidly than previously known, but one ice shelf, the Wordie Ice Shelf, has disappeared completely. Another, the Larsen Ice Shelf, has lost its entire northern portion, a chunk three times the size of Rhode Island, in the space of 23 years.

As in the Arctic, as darker sea water replaces floating ice, the result is an increased cycle of warming, as the water absorbs energy from the sun that the ice had reflected.

"This study provides the first insight into the extent of Antarctica's coastal and glacier change," Interior Secretary Ken Salazar noted about the USGS study. "The rapid retreat of glaciers there demonstrates once again the profound effects our planet is already experiencing -- more rapidly than previously known -- as a consequence of climate change."

Even the melting of the West Antarctic ice sheet would take decades or a century to fully affect U.S. coastal cities. Still, the data about Antarctica is a reminder of one very important thing: The cost of doing nothing to address global warming is likely to be much larger than the cost of doing something. Doing nothing means we'll have to invest heavily in water infrastructure along our coasts, as well as humanitarian aid to low-lying nations (as just two expensive examples of expenses to come). If we act now, it may or may not take some steam out of the economy, but it will produce clean energy jobs and a more sustainable economy in the long run.

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