Researchers have known that the Thwaites Glacier is in trouble due to encroaching warm waters, but they’d never actually analyzed data from beneath the glacier’s float ice shelf—until now.

For 13 hours, the underwater vehicle traveled around two deep troughs beneath the glacier that funnel warm water toward it.

As it did, the vehicle captured data showing that warm water—warm for a glacier, at up to 33.89 degrees Fahrenheit (1.05 degrees Celsius)—is swirling around the glacier’s crucial “pinning points,” or the points of contact where the ice shelf meets the bedrock that holds it in place.

That warm water is also likely mixing in and around the grounding line, deep into the cavity, and that means the glacier is also being attacked at its feet where it is resting on solid rock.”.

The discovery of warm water confirms previous concerns from a separate project, wherein another group of 100 scientists drilled a hole 2,000 feet into the glacier.

It’s not just Pine Island Bay’s encroaching warm waters we have to worry about, either.

Using the submarine’s readings, the authors also mapped out the channels along which warm water is getting transported toward Thwaites Glacier.

Thwaites Glacier’s collapse would raise sea levels by 1.5 to 3 feet (0.5 to 0.9 meters), and could also trigger an even worse chain of events because it could initiate the collapse of another nearby imperiled ice shelf, the Pine Island Glacier.