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article imageDecades of rising seas predicted as huge Antarctic glacier melts

By Robert Myles     Feb 27, 2014 in Science
Cambridge - Pine Island Glacier, part of the West Antarctic Ice Sheet and the biggest single contributor to rises in global sea levels, continues to melt at record rates. The melt could continue for decades, according to new research.
Not only is the Pine Island Glacier retreating, it’s doing so at an accelerating rate. That's one of the findings of a team of geologists from the UK, USA and Germany writing this week in the journal Science.
They found that this isn’t the first time the Pine Island Glacier has experienced such rapid contraction. Recent decades have seen the glacier not only retreat in extent but thin as it does so, a process similar to what happened 8,000 years ago.
What took place eight millennia ago demonstrates the potential, say the researchers, for the current ice loss the glacier is experiencing to continue for several decades as well as providing an important comparison model for predicting future behavior of the Pine Island Glacier.
“This paper is part of a wide range of international scientific efforts to understand the behavior of this important glacier,” Professor Mike Bentley, a co-leader of the project based at Durham University said, in the study.
“The results we’re publishing are the product of long days spent sampling rocks from mountains in Antarctica, coupled to some exceptionally precise and time-consuming laboratory analyses. The results are clear in showing a remarkably abrupt thinning of the glacier 8,000 years ago.”
The glacier currently is undergoing an accelerating retreat, thinning as it does so. The scientists believe ocean-driven melting is causing this to happen with an increase in warm ocean water finding its way under the ice shelf.
The Pine Island Glacier is one of the largest ice flows in Antarctica. Along with the Thwaites Ice Stream, it disgorges into the Amundsen Sea off west Antarctica. Together, Thwaites and the Pine Island Glacier drain about five percent of the Antarctic Ice Sheet, the world’s biggest.
The recession and thinning of the glacier observed in recent decades is of particular concern since a large adjacent floating ice shelf “regulates” the flow of ice off the Pine Island Glacier into the sea, as illustrated in the accompanying video.
If the buttress of the floating ice shelf, which itself is thinning, is removed, the flow rate of ice from the glacier into the sea could quickly increase with consequences for sea-levels worldwide.
These consequences remain uncertain, say the researchers. They cannot say with accuracy how much more ice will be lost to the ocean in the future. Questions remain concerning the rate, timing and persistence of future sea level rise. But what their research, so far, has demonstrated is that once such rapid retreat of the glacier takes hold, it won’t be a seven-day wonder.
With the Pine Island Glacier undergoing rapid retreat, the researchers have been able to examine rocks now exposed and which provide evidence of past ice sheet change. Using highly sensitive dating techniques pioneered by one of their team, the geologists have been able to track the thinning of the glacier over the millennia. That research points to past thinning having continued for decades.
Lead author Joanne Johnson from the British Antarctic Survey (BAS) commented, “Our geological data show us the history of Pine Island Glacier in greater detail than ever before. The fact that it thinned so rapidly in the past demonstrates how sensitive it is to environmental change; small changes can produce dramatic and long-lasting results. Based on what we know, we can expect the rapid ice loss to continue for a long time yet, especially if ocean-driven melting of the ice shelf in front of Pine Island Glacier continues at current rates.”
The full science paper, entitled, “Rapid thinning of Pine Island Glacier in the early Holocene,” was published Feb. 20 in Science journal.
More about Antarctica ice sheet, Pine Island Glacier, Melting glaciers, Glaciers melting, Global warming
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