A huge network of lakes has been discovered beneath the ice of East Antarctica’s largest glacier.

Researchers from the Australian Antarctic Division (AAD) used seismic testing on the Totten glacier to discover what was underneath, revealing massive subglacial lakes that they say radically alter estimates of sea level rise in the Antarctic.

The Totten glacier is the largest in East Antarctica, stretching 30 kilometers (19 miles) wide and up to 2 kilometers (just over 1 mile) thick. It’s the biggest ice catchment and draining point for the East Antarctic ice sheet, and holds enough ice that if it were all to melt, it could raise global sea levels by up to 7 meters (23 feet). It’s also thinning faster than any other glacier in the area.

The speed at which a glacier moves is determined by what it is traveling over, so finding out what is underneath – bedrock, lakes, or even a subglacial ocean – is paramount.

If it’s bedrock, the glacier will catch as it moves so will travel more slowly, but if it’s water the glacier moves much faster. The amount of water, and the flow in and out of subglacial lakes controls the rate at which ice flows into the ocean, ultimately affecting sea levels.

“This study has shown us for the first time that there are substantial amounts of water contained in subglacial lakes, not far from the ocean, that we know very little about.” AAD glaciologist Dr Ben Galton-Fenzi said in a statement.

“So this research is critical in helping us predict how the melting of Antarctic glaciers will change the world’s oceans into the future.”

To find this out, the team carried out seismic testing by drilling into the ice sheet and setting off a series of explosions about 2 meters (6.5 feet) under the ice. They placed geophones along the surface of the glacier and listened to the reflected sound, the soundwaves echo differently off layers of ice, rock etc, to get an understanding of what was down there.

The fact that they found “a substantial amount of water” in the form of a large network of lakes does not bode well.

The landmark IPCC report that came out towards the end of last year predicts a worst-case scenario that could see global sea levels rise by up to 1 meter (3.3 feet) by the end of the century. Dr Galton-Fenzi told ABC News, however, that those estimates did not factor in the increased discharge of ice from Antarctic glaciers due to climate change, and more research like theirs was needed to better predict the rate at which this occurs.

"We actually know for a fact that the Totten Glacier is one of the regions that's actually changing,” he said.

"We know there's warm water present under the glacier, so we expect this is one of the regions in East Antarctica that's going to change first."