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Wednesday, July 9, 2008 01:58 am

The great meltdown

Disappearing ice sheets could raise world’s oceans by 170 feet, experts say

Untitled Document Recent NASA photos showed the opening of the Northwest Passage and revealed that a third of the Arctic’s sea ice has melted in recent years. Are sea levels already starting to rise accordingly — and, if so, what are the effects?
Researchers were astounded when, in the fall of 2007, they discovered that the year-round ice pack in the Arctic Ocean had lost some 20 percent of its mass in just two years, setting a new record low since documentation of the terrain with satellite imagery was begun in 1978. Without action to stave off climate change, some scientists believe, at that rate all of the year-round ice in the Arctic could be gone by as early as 2030. This massive reduction has allowed an ice-free shipping lane to open through the fabled Northwest Passage along northern Canada, Alaska, and Greenland. Although the shipping industry — which now has easy northern access between the Atlantic and Pacific oceans — may be cheering this “natural” development, scientists worry about the impact of the resulting rise in sea levels around the world. With about a third of the world’s population — and 25 percent of Americans — living within 300 feet of an ocean coastline, sea-level rise is a big deal. According to the Intergovernmental Panel on Climate Change, made up of leading climate scientists, sea levels have risen some 3.1 millimeters per year since 1993. The World Wildlife Fund reports that low-lying island nations, especially in equatorial regions, have been hardest hit by this phenomenon, and some are threatened with total disappearance. Rising seas have already swallowed up two uninhabited islands in the Central Pacific. On Samoa, thousands of residents have moved to higher ground as shorelines have retreated by as much as 160 feet, and islanders on Tuvalu are scrambling to find new homes as saltwater intrusion has made their groundwater undrinkable and increasingly strong hurricanes and ocean swells have devastated shoreline structures. WWF says that rising seas throughout tropical and subtropical regions of the world have inundated coastal ecosystems, decimating local plant and wildlife populations. In Bangladesh and Thailand, coastal mangrove forests — important buffers against storms and tidal waves — are giving way to ocean water. Unfortunately, even if we curb global-warming emissions today, these problems are likely to get worse before they get better. According to marine geophysicist Robin Bell of Columbia University’s Earth Institute, sea levels rise by about 1/16 inch for every 150 cubic miles of ice that melts off one of the poles. “That may not sound like a lot, but consider the volume of ice now locked up in the planet’s three greatest ice sheets,” she writes in a recent issue of Scientific American. “If the West Antarctic ice sheet were to disappear, sea level would rise almost 19 feet; the ice in the Greenland ice sheet could add 24 feet to that; and the East Antarctic ice sheet could add yet another 170 feet to the level of the world’s oceans: more than 213 feet in all.” Bell underscores the severity of the situation by pointing out that the 150-foot tall Statue of Liberty could be completely submerged within a matter of decades.
For more information: Intergovernmental Panel on Climate Change, www.ipcc.ch; WWF, www.panda.org; Earth Institute at Columbia University, www.earth.columbia.edu.
Send questions to Earth Talk, care of E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881 or e-mail earthtalk@emagazine.com.


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