Scientists say glaciers in the mountains of Chile and Argentina are melting at a rate which has doubled since 1975.
Scientists combined space observation and survey data to study the 63 largest Patagonian ice fields.
Comparing ice loss rates between 1968-1975 and 1975-2000, they found it had more than doubled.
The amount of ice lost between 1995 and 2000 was equivalent to to a sea level rise of about 0.105 millimetres per year.
The researchers, led by Eric Rignot from the Jet Propulsion Laboratory in Pasadena, California, said: "The glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation, and their contribution to sea level per unit area is larger than that of Alaska glaciers."
"We attribute this enhanced vulnerability of Patagonia glaciers to climate change to their higher turn over rates and low ELAs (equilibrium line altitudes), combined with the dominance of calving glaciers," said the scientists.
Equilibrium line altitude is the dividing line between the parts of glacier that are accumulating and losing ice.