The vast Thwaites glacier in western Antarctica has been melting rapidly for almost a century, new research shows.

The 80-mile-wide glacier has been rapidly melting since at least the early 1940s. It is now losing an estimated 50 billion tons of ice more than the snow that falls on it each year.

An international research team led by researchers at the University of Houston used Amundsen Sea sea-sediment collected near the glacier along with radioactive dating and the El Nino climate data to determine when the glacier’s melting began. They believe a strong El Nino event from 1939 to 1942 warmed the west Antarctic Ocean, sparking the rapid melting of the glacier.

This melting, accelerating due to climate change warming, is contributing to 4 percent of the global sea-level rise. In the last decade, sea levels have risen by about a tenth of an inch per year. If the Thwaites glacier was to collapse and melt completely, it would raise the global sea level by more than 2 feet.

Additionally, the glacier is holding back the West Antarctica ice sheet. If this glacier was to fail, a broader ice sheet could shift and begin to melt into the Antarctic Ocean, increasing sea levels even further.

The study of this glacier is critical to understand possible effects of climate change and how it will affect sea-level rise.