A team of scientists from NASA's Jet Propulsion Laboratory in Pasadena, California, and the University of Colorado said new satellite imagery had revealed a vast expanse of snow melted in 2005, though it had previously been considered unlikely.
A NASA statement on Tuesday described the findings as "the most significant melt observed using satellites during the past three decades."
Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, said it was the first time melting on such a scale had been detected.
"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," said Steffen.
"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 melting occurred in multiple areas, including far inland, at high latitudes and high elevations, where melt had once been considered unlikely.
The melting was discovered using satellite scatterometry, a sophisticated imaging system which is able to distinguish between recently frozen ice or snow from snow that has been frozen for years.