More unsettling news from the bottom of the world.

Scientists have uncovered evidence of “vigorous melting” at Antarctica’s Thwaites Glacier, according to a new study published Monday. And for the first time, there is visible evidence that shows warm seawater pumping underneath the glacier.

The Thwaites Glacier, part of the vast West Antarctic Ice Sheet, is one of the world’s fastest-changing and most unstable glaciers. It’s called the Doomsday Glacier because of its potential to dramatically raise sea levels in places such as Florida, and it has been studied for years as an indicator of human-caused climate change.

Study results also suggest the Antarctic Ice Sheet is more vulnerable to a warming ocean than previously thought, and, worryingly, may “require a reassessment of sea-level rise projections.”

A ‘most unstable place’

“Thwaites is the most unstable place in the Antarctic and contains the equivalent of 60 centimeters (two feet) of sea-level rise,” said study co-author Christine Dow of the University of Waterloo in Ontario. “The worry is that we are underestimating the speed that the glacier is changing, which would be devastating for coastal communities around the world.”

To conduct the study, scientists used high-resolution satellite radar data to find evidence of the intrusion of warm, high-pressure seawater many miles beneath the grounded ice of Thwaites glacier.

Study lead author Eric Rignot of the University of California−Irvine told USA TODAY that there’s much more seawater flowing into the glacier than had been previously thought. These “intrusions make the glacier more sensitive to ocean warming, and more likely to fall apart as the ocean gets warmer.”

Future projections of global sea-level rise will have to include this new data, Rignot said. “The projections will go up,” he said.

Rising seas, swamped cities

As it melts, Thwaites could cause ocean levels to rise as much as 2 feet, researchers say. But the glacier is also a natural dam to other ice in West Antarctica. If that ice is released into the oceans, levels could rise 10 feet, researchers estimate.

Such a rise would put many of the world’s coastal cities underwater. According to the new study, it “will gravely impact populations in many low-lying areas like Vancouver, Florida, Bangladesh and low-lying Pacific islands, such as Tuvalu and the Marshall Islands.”

How many years (or centuries) will it take for the Thwaites Glacier to melt entirely?

“It will take many decades, not centuries,” Rignot told USA TODAY. “Part of the answer also depends on whether our climate keeps getting warmer or not, which depends completely on us and how we manage the planet.”

The study was published in the peer-reviewed journal Proceedings of the National Academy of Sciences.

This article originally appeared on USA TODAY: Doomsday Glacier melting is ‘vigorous,’ offering stark warning