Antarctica's gaining ice in some spots.

Large portions of Antarctica's icy land-mass may be storing enough snowfall to slow the rise in sea level suspected to be caused by global warming. That's the suggestion of measurements taken by spacecraft over a dozen years.

Radar altimeters on two satellites gathered their data between 1992 and 2003, says Curt H. Davis, a hydrologist at the University of Missouri-Columbia. Because the craft didn't pass over areas near the South Pole, altitude measurements could be estimated for only about 70 percent of the Antarctic land-mass. Nevertheless, says Davis, that represents an 8.5-million-square-kilometer region.

At points in East Antarctica, the largest region of the continent, altitudes of surface ice either held steady or grew as much as 6 centimeters per year. In West Antarctica, variations in altitude were larger, ranging from a loss of 10 cm/yr to a gain of 19 cm/yr. Climate models for the region suggest that accumulated snowfall caused the gains, says Davis.

Overall, an average of 1.8 cm of precipitation would have piled up each year on the areas of the continent that were visible to the satellites, Davis and his colleagues say in the June 24 Science. That adds up to 45 billion tons of snowfall annually. The transfer of that much moisture from the oceans would cause world sea levels to drop about 0.12 millimeter each year.--S.P.