While cautioning that melting ice sheets are an unknown factor, many research groups have forecast that global warming will cause sea levels to rise in this century, with mixed impacts on coastlines. For instance, the Intergovernmental Panel on Climate Change projected a rise of 7 to 23 inches. Now a team of scientists funded by the U.S. Department of Energy and the National Science Foundation has focused on the effect Greenland’s melting ice sheet may have on ocean levels. Their conclusion: New York, Boston, and other cities in the northeastern United States and in Canada could be hard hit.

Using computer modeling, the scientists from the National Center for Atmospheric Research (NCAR), the University of Colorado at Boulder, and Florida University considered three scenarios for Greenland’s melting: a melt rate continuing to increase by 7 percent per year and melt rates slowing down to increase by 1 or 3 percent per year.

Runoff from the melting ice sheet could alter ocean circulation in a way that would push water toward the northeast coast of North America, according to this computer model. With moderate to high melt rates, sea levels would rise 12 to 20 inches more than in other coastal areas. NCAR researcher Aixue Hu says, “Major northeastern cities are directly in the path of the greatest rise.”

“The oceans will not rise uniformly as the world warms,” says Gerald Meehl, a co-author of the team’s paper in Geophysical Research Letters. “Ocean dynamics will push water in certain directions, so some locations will experience sea level rise that is larger than the global average.

Recapping this and other recent studies, David Fahrenthold, Washington Post staff writer, describes the change in sea levels along the northeast coast as pushing “water toward a shoreline inlaid with cities, resort boardwalks and gem-rare habitats.” He reports that governors of the U.S. coastal states have pledged to identify places most vulnerable to high water.

The upcoming August issue of Beyond Penguins and Polar Bears features an article about Leigh Stearns, a researcher with the Center for the Remote Sensing of Ice Sheets. She is “taking the pulse” of a fast-moving outlet glacier in Greenland with GPS units and other modern-technology.