Arctic sea ice is shrinking due to climate change but the extent of Antarctic sea ice has grown slightly and U.S. researchers say they may have figured out why.

Scientists at the Georgia Institute of Technology have presented a possible solution to the conundrum at the Proceedings of the National Academy of Science, ScienceDaily.com reported Tuesday.

As the atmosphere warms, the researchers say, the water cycle of moisture from land and ocean into the atmosphere accelerates, causing more precipitation in the Southern Ocean surrounding Antarctica.

The increased precipitation, mostly in the form of snow, stabilizes the upper ocean and insulates it from the ocean heat below, Jiping Liu, a research scientist in Georgia Tech's School of Earth and Atmospheric Sciences, says.

The insulating effect reduces the amount of melting occurring below the sea ice, he says, and the snow has a tendency to reflect atmospheric heat away from the sea ice, which reduces melting from above.

Climate models predict greenhouse gases will continue to increase in the 21st century, reaching a tipping point that will result in sea ice melting at a faster rate from both above and below, another researcher says.

The finding "raises some interesting possibilities about what we might see in the future," Judith A. Curry, chair of the School of Earth and Atmospheric Sciences says.

"We may see, on a time scale of decades, a switch in the Antarctic, where the sea ice extent begins to decrease."