The loss of ice covering Greenland and Antarctica has accelerated over the past 20 years, contributing substantially to sea level rise, said a study conducted by 26 laboratories around the world.

The study, supported by NASA and the European Space Administration and published by the journal Science, estimates that about 20 percent of sea-level rise can be attributed to the 344 billion tons of glacial ice lost annually in Greenland and Antarctica. (The other major factors are expansion of the oceans as they warm and melting of mountain glaciers.) The study resolves a 20-year dispute among climate scientists, said professor Andrew Shepherd of the University of Leeds in England, who coordinated the study with research scientist Erik Ivins of NASA's Jet Propulsion Laboratory in La Canada Flintridge, Calif.

It found that two-thirds of the annual ice loss came from Greenland, shown at left, and about a third from Antarctica. Though the study found that some ice had been gained in the East Antarctic sheet, the overall losses were far greater. Sea level has risen an average of 3 millimeters a year since 1992, but the effect is cumulative and accelerating, said John Abraham, associate professor of thermal sciences at the University of St. Thomas in St. Paul. He said. "Every inch we get makes a storm surge worse."

"This study confirms that ice loss is occurring and raising sea levels," he said. "For those people who thought that ice sheets were not contributing to sea level rise, they are dead wrong."