Tsunami in the global meltdown

NASA scientists detected a pulse of melting ice and water travelling through a major glacier in Greenland that was so big that it warped the solid Earth – a surge equivalent in mass to 18 000 Empire State Buildings.

The wave – which occurred during the 2012 record melt year – travelled nearly 24km through the Rink Glacier in western Greenland over four months before reaching the sea, the researchers said.

“It’s a gigantic mass,” said Eric Larour, one of the study’s authors and a researcher at Nasa’s Jet Propulsion Laboratory. “It is able to bend the bedrock around it.”

Such a “wave” has never before been detected in a Greenland or Antarctic glacier. The total amount of mass carried in the wave – in the form of either water, ice, or some combination of both – was 1.67 billion tons per month, or 6.68 billion tons overall over four months, the study, published in Geophysical Research Letters, found.

The study was led by the lab’s Surendra Adhikari and co-authored by Erik Ivins.

However, the scientists don’t know what the wave actually looked like or precisely what caused it – much of it was occurring below the surface of the glacier. They also don’t know precisely what it was made of. “We are losing a combination of water and ice, we don’t know what fraction,” said Adhikari.

The researchers were only able to detect the wave because a GPS sensor moved 15mm as the wave went by causing a deep indentation in the Earth’s crust.

Glaciologist Richard Alley said: “Put a little piece of tape on the sheet (of a bed). Put your fist right next to the tape and push down. The tape will move down as you push down, and also will move horizontally toward your fist just a little… that’s sort of what this team did. They saw a ‘fist’ of mass sliding down the glacier past their GPS station, caused by extra meltwater.” – Washington Post