A new study published Monday warns that "unstoppable" melting in West Antarctica could make a three-meter increase in sea level "unavoidable."

According to researchers at Germany's Potsdam Institute for Climate Impact Research, the vulnerable Amundsen Sea sector of West Antarctica "has most likely been destabilized." They point to recent studies indicating that this area of the ice continent is "the first element in the climate system about to tip."

"If the Amundsen Sea sector is destabilized, then the entire marine part of West Antarctica will be discharged into the ocean."
—Johannes Feldmann & Anders Levermann, Potsdam Institute for Climate Impact Research

If that is true, computer modeling suggests the consequences could be catastrophic, initiating a process "which is then unstoppable and goes on for thousands of years," said Johannes Feldmann, lead author of the study.

"The result of this study is an if–then statement," reads the paper, which appears in the journal Proceedings of the National Academy of Sciences. "[I]f the Amundsen Sea sector is destabilized, then the entire marine part of West Antarctica will be discharged into the ocean."

It continues: "The currently observed retreat in West Antarctica hence might mark the beginning of a millennial period of self-sustained ice discharge from West Antarctica and require long-term global adaptation of coastal protection, such as the building or rebuilding or raising of dykes, the construction of seawalls, or the realization of land fills in the hinterland."

In a statement, Feldmann put it starkly: "What we call the eternal ice of Antarctica unfortunately turns out not to be eternal at all. Once the ice masses get perturbed, which is what is happening today, they respond in a non-linear way: there is a relatively sudden breakdown of stability after a long period during which little change can be found."

Responding to the findings, Jonathan Bamber, a glaciologist at the University of Bristol in the UK who was not involved in the research, acknowledged that "how quickly we reach this point of no return, and how rapidly it proceeds," are questions still to be answered.

"But what is clear," he told the Washington Post, "is that the next few decades will determine whether the [West Antarctic ice sheet] is just endangered or on its path to extinction."

Study co-author and Intergovernmental Panel on Climate Change sea-level expert Anders Levermann noted that if swift carbon reductions are not implemented, "further greenhouse-gas emission will heighten the risk of an ice collapse in West Antarctica and more unstoppable sea-level rise." Otherwise, he warned, rising oceans could "destroy our future heritage by consuming the cities we live in."