Big area of Antarctica melted in 2005

NASA's QuikScat satellite detected extensive areas of snowmelt, shown in yellow and red, in west Antarctica in January 2005.

WASHINGTON (Reuters) -- Vast areas of snow in Antarctica melted in 2005 when temperatures warmed up for a week in the summer in a process that may accelerate invisible melting deep beneath the surface, NASA said on Tuesday.

A new analysis of satellite data showed that an area the size of California melted and then re-froze -- the most significant thawing in 30 years, the U.S. space agency said.

Unlike the Arctic, Antarctica has shown little to no warming in the recent past with the exception of the Antarctic Peninsula, where ice sheets have been breaking apart.

Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, California, and Konrad Steffen of the University of Colorado in Boulder measured snowfall accumulation and melt in Antarctica from July 1999 through July 2005.

They found evidence of melting in several areas, including high elevations and far inland in January of 2005, when temperatures got as high as 41 degrees Fahrenheit (5 degrees Celsius).

"Increases in snowmelt, such as this in 2005, definitely could have an impact on larger scale melting of Antarctica's ice sheets if they were severe or sustained over time," Steffen said in a statement.

"Water from melted snow can penetrate into ice sheets through cracks and narrow, tubular glacial shafts called moulins," Steffen added.

"If sufficient melt water is available, it may reach the bottom of the ice sheet. This water can lubricate the underside of the ice sheet at the bedrock, causing the ice mass to move toward the ocean faster, increasing sea level.