Antarctica's ice sheet is melting underwater and at a rate five times faster than previously thought.

Antarctica's Ground Lines Are Retreating

In a new study published in the journal Nature Geoscience, researchers showed that between 2010 and 2016, the Southern Ocean melted 565 square miles of underwater ice.

Antarctica's glaciers have been retreating at a rate of 82 feet per year. However, the grounding lines of eight of the ice sheet's 65 largest glaciers have been retreating five times faster at about 410 feet per year.

"Our study provides clear evidence that retreat is happening across the ice sheet due to ocean melting at its base, and not just at the few spots that have been mapped before now," said study researcher Hannes Konrad, from the University of Leeds.

Contribution To Rising Sea Level

Researchers said that the phenomenon could contribute to rising sea level.

"Releasing [inland glaciers] from the sea bed removes friction, causing them to speed up and contribute to global sea level rise," Konrad said.

Antarctica is the largest reservoir of freshwater on Earth, which means it can significantly raise global sea water levels. Konrad said that if Antarctica's Thwaites Glacier collapses, the result would be more than 6 feet in sea level rise.

Effect On Coastal Cities And Island Nations

The melting poses threat, particularly to coastal cities and island nations. Konrad said that even if scientists manage to cool the oceans, it is no longer possible to stabilize the glacier, which means some islands will cease to exist. Konrad also said that major cities are also at risk.

"West Antarctica can add an additional 4.5 meters in sea levels into the world's oceans, so just imagine what will happen to a city like London that lies at this altitude above sea level," Konrad said.

Coastal mega-cities, which include New Orleans, Jakarta, Dhaka, Bangkok and Ho Chi Minh City, are also at risk of getting submerged in the water as a result of sea level rise.

Earlier studies already warned of the potential consequences of rising sea levels. Researchers of a 2016 study showed that a 6-foot increase in sea level, which they said could happen by the year 2100, would expose 13 million Americans to flooding. Up to six million people may be affected in Florida and one million people each in Louisiana and California.

Other Impacts Of Rising Sea Level

A 2017 study also concluded that thousands of historical sites could submerge because of rising sea levels. These include burial grounds, space mission launchpads, and early settlements.

Rising sea levels could also destroy plant and animal habitats.