The rapid thinning of Pine Island Glacier, located on the West Antarctic ice sheet, may be irreversible, an international team of scientists warn.

Spanning more than 160,000 square kilometers, the PIG, as the ice mass is known, is the largest single contributor to sea-level rise in Antarctica, contributing 25 percent of the total ice loss from West Antarctica, according to the new study published in the journal Nature Climate Change.

The report states that melting has become so excessive, the glacier has most likely "reached a point of no return," the British Antarctic Survey (BAS) wrote in a statement, noting that the amount of melting sea ice is likely to increase during the next two decades.

"Currently we see around three millimeters of sea level rise a year, and the Pine Island Glacier retreat could contribute an additional 3.5 - 10 millimeters in the next twenty years, so it would lead to a considerable increase from this area alone," said Hilmar Gudmundsson of the BAS. "But the potential is much larger."

Using field observations and data from three ice-flow models, Gudmundsson explains that not only have he and his colleagues observed more ice flowing into the ocean, but a quickening in pace as it moves across the line dividing grounded and floating ice.

"We can also see this boundary is migrating further inland," he said. 

All three models - which incorporated information regarding bedrock topography beneath the glacier, atmospheric conditions, ocean melting and ice surface features - reported that the glacier is unstable and will continue to melt for tens of kilometers.

"The models show a strong agreement and the result is a striking vision of the near future," said Gael Durand, a researcher from the University of Grenoble and lead author of the paper. "All the models suggest that this recession will not stop, cannot be reversed and that more ice will be transferred into the ocean."