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

Rising temperatures two years ago led to widespread melting of snow cover in west Antarctica, according to scientists examining the impact of global warming on the icy continent.

The melting of snow cover in regions in January 2005 was the most significant Antarctic melting seen since satellites began observing the continent three decades ago, NASA said Tuesday.

It was also the first major melting detected using NASA's QuikScat satellite, which can measure both accumulated snowfall and temperatures in various regions.

The team of scientists found evidence of melting in regions not normally affected: up to 900 kilometres inland from the open ocean, farther than 85 degrees south (within 500 kilometres of the South Pole) and higher than 2,000 metres above sea level.

QuikScat found maximum air temperatures at the time of melting were unusually high, reaching more than 5 C in one of the areas. These maximum temperatures remained above themelting point for approximately a week.

The researchers were led by Son Nghiem of NASA's Jet Propulsion Laboratory and Konrad Steffen, the director of the Co-operative Institute for Research in Environmental Sciences at the University of Colorado. Theypublished their results in a book, Dynamic Planet.

"Antarctica has shown little to no warming in the recent past, with the exception of the Antarctic Peninsula, but now large regions are showing the first signs of the impacts of warming as interpreted by this satellite analysis," said Steffen in a statement.

"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."

The 2005 melt was extensive enough to create a layer of ice when the water refroze, but was not long enough for the water to flow to the sea. Steffen said if enough water from melted snow is created, it could slip through the cracks of the continent's ice sheets and potentially affect their movement.

The Antarctic ice mass is the Earth's largest freshwater reserve, and changes in its condition can have an impact on sea levels, ocean salinity and water currents.

"We need to know what's coming in and going out of the ice sheets," said Ngheim.

"QuikScat data, combined with data from NASA's IceSat and Gravity Recovery and Climate Experiment satellites, along with aircraft and ground measurements, all contribute to more accurate estimates of how the polar ice sheets are changing."