The frigid air over Antarctica took three weeks longer than usual to warm at the onset of the Antarctic spring this year, prompting concern that the "ozone hole" discovered over the icy continent less than three years ago may be affecting global climate.

According to satellite data from the National Aeronautics and Space Administration, the polar vortex -- a whirlpool-like mass of extremely cold air that forms over Antarctica in the dark winter months -- broke up in late November. The vortex normally breaks up in late October or early November, when spring brings sunlight back to the South Pole and warms the atmosphere.

"This is the latest that it has failed to break up," NASA atmospheric scientist Robert Watson said. "It may be what you would expect because there is so little ozone there. What one has to consider are the ramifications."

University of California scientist F. Sherwood Rowland, a leading expert in ozone depletion, said the event "could be the first indication of major climatic change. There is no way of judging the impact, but it's an ominous trend."

Other researchers said it is not certain whether stratospheric temperatures over Antarctica could affect weather patterns. "I don't think it makes a difference in the troposphere {the atmospheric level closest to the Earth}," NASA scientist Mark Schoeberl said. "It means that temperatures in the polar region are still anomalously cold relative to previous years."

Scientists think that the delayed warming is related to a phenomenon first reported by British researchers in 1985 and now known as the ozone hole: During each Antarctic winter, ozone levels drop drastically before rising to normal again in the spring.

The discovery caused alarm, because ozone protects Earth and its inhabitants from most of the sun's most damaging ultraviolet rays, which can cause cancer, cataracts and immune-system problems.

Although the phenomenon is not understood fully, recent research tends to buttress theories that the ozone is being destroyed by chlorine molecules from a class of chemicals called chlorofluorocarbons. The process is believed to be aided by Antarctica's unusual atmospheric conditions, including the polar vortex, which traps chlorine molecules and spawns icy stratospheric clouds that enhance chemical reactions.

When the polar vortex breaks up in the spring, ozone levels over Antarctica rise and the "hole" disappears. Some ozone comes from air moving into Antarctica from other parts of the globe, and some comes from natural reformation of ozone when sunlight strikes the stratosphere.

Scientists theorize that the vortex held on longer this spring because of the magnitude of ozone loss in winter. A research expedition this year found ozone levels down more than 60 percent.

Ozone absorbs radiation and helps heat the atmosphere. Some scientists say the lack of ozone over Antarctica may have slowed the heating necessary to break up the polar vortex.

"If ozone doesn't reform, you get no heating," said Irving Mintzer of the World Resources Institute. "So you get continuing cold that contributes to the formation of stratospheric clouds and may increase ozone depletion. It's yet another of those surprises that have characterized our emerging understanding of the hole."

Schoeberl said the polar vortex also was late in breaking up in 1985, when ozone levels dropped nearly as steeply as they did this year.

The delayed breakup meant that the ozone hole lasted longer than usual, exposing an area larger than the continental United States to abnormally high levels of ultraviolet radiation for several extra weeks.

"We have to ask what the impact will be of that low ozone on the aquatic life around Antarctica," Watson said.