FRANCE: Returning to their labs, the researchers simulated the glacier scene in a cylindrical tank that mimicked the fjords that constitute thin streams of seawater extending into land (where the water joins the Helheim Glacier wall).
“We were really surprised to see the glacier flowing backward in our GPS data”.
The researchers have been capable of include this conclusions by monitoring the Helheim Glacier, a serious outlet of the Greenland Ice Sheet, from July to September 2013 which reached to about 55 days.
The relentless flow of a glacier may seem unstoppable, but a team of researchers from the United Kingdom and the USA has shown that during some calving eventswhen an iceberg breaks off into the oceanthe glacier moves rapidly backward and downward, causing the characteristic glacial earthquakes which until now have been poorly understood.
“Imagine that you could go and just push on the front of the glacier with your thumb, really hard, so hard that you could reverse the direction that the front of the glacier is moving”, says Nettles, “and then you let it go”.
As a recently calved iceberg begins to topple over into the ocean, it displaces a lot of water, Nettles said. When the ice plunged into water, the pressure of water behind the ice would plummet resulting in the main glacier going down by 10 centimeters and consequently pulling up the earth. Therefore, upward force on the Earth and the force of the falling iceberg produce a measurable seismic wave.
This insight will enable scientists to measure glacier calving remotely and will improve the reliability of models to predict future sea-level rises in a warming climate. “Calving is such an important component of the mass loss in both Greenland and Antarctica – it’s really important to try and understand how calving actually works”, Nettles said. They saw how the icebergs fell away from the glacier and temporarily reversed its course, causing glacial earthquakes that measure about magnitude five on the Richter Scale, according to a release. This fast pace “is very human in its timescale”, she said, linking it to anthropogenic climate change. “That’s sort of the size of an ice cube you would have if you filled up Central Park in New York City to the top of the Empire State Building”.
“We’re talking about something that is a gigaton of ice”, Nettles says.
