Antarctic Glacier Collapse Means Sea-Level Rise Now ‘Unstoppable’ - maitengok!

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Friday, May 16, 2014

Antarctic Glacier Collapse Means Sea-Level Rise Now ‘Unstoppable’


Climate change is a large, multi-faceted issue so it is hard to name any one aspect as being most important. However, one aspect that is hard to ignore is the fact that a rising sea level has massive socioeconomic implications. Unfortunately, a new paper from lead author Eric Rignot at NASA’s Jet Propulsion Laboratory published in Geophysical Research Letters claims that some glaciers in West Antarctica “have passed the point of no return” and are sliding into the ocean where they will melt and contribute to increased sea-level. 
A section of glaciers along West Antarctica’s coastline on the Amundsen Sea was previously predicted to be solid enough to last thousands of years. A new report, however, finds that the ice will slip into the water and melt much faster than expected. These massive glaciers are releasing tremendous amounts of water each year; nearly the equivalent of the entire Greenland Ice Sheet. When they are gone, they will have increased sea-level by about 1.2 meters (4 feet). 
"This sector will be a major contributor to sea level rise in the decades and centuries to come," Rignot said in a press release. "A conservative estimate is it could take several centuries for all of the ice to flow into the sea."
Rignot and his team came to this conclusion after analyzing three critical factors of glacier stability: slope of the terrain, flow rate, and the amount of the glacier floating in the water. Flow rate was the topic of a paper Rignot’s team published previously in Geophysical Research Letters where they determined flow rate has increased over the last few decades.
The current paper discusses the slope and how much of the glacier is actually floating on seawater. "The grounding line is buried under a thousand or more meters of ice, so it is incredibly challenging for a human observer on the ice sheet surface to figure out exactly where the transition is," Rignot explained. "This analysis is best done using satellite techniques."
In order to float in the water, the glacier will melt on the bottom to make itself lighter. Satellite data obtained from 1992-2011 was able to show the researchers where the edge of the land is under the glacier. They have revealed that portions of the glacier which were securely on land are now floating, meaning there is more room under the glacier for water flow to accelerate. The two factors, flow and grounding line, are intrinsically connected. 
The team searched for areas under the glaciers that would be able to slow the flow of water. These “pinning points” would include hills, large rocks, and other bumps in the terrain. Unfortunately, five out of the 6 glaciers studied do not have any pinning points, and the sixth glacier is melting so quickly and will soon lose it. 
"The collapse of this sector of West Antarctica appears to be unstoppable," Rignot said. "The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable."

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