May 17, 2014
West Antarctic Ice Sheet Is Collapsing
The Thwaites Glacier on the West Antarctic Ice Sheet has begun to thin and will most likely disappear within a few centuries, according to topographic maps used by researchers from the University of Washington. The researchers theorize that this could raise the levels of the seas by two feet.
No firm timeline prediction has been established, but because this glacier plays a key role in the rest of the Antarctic Ice Sheet, when it does occur there will be enough melt to cause the global seas to rise another 10 to 13 feet. The Study is published in the May 16 Science.
“There’s been a lot of speculation about the stability of marine ice sheets, and many scientists suspected that this kind of behavior is under way. This study provides a more quantitative idea of the rates at which the collapse could take place,” said Ian Joughin, a glaciologist at the UW’s Applied Physics Laboratory.
Although this change in the glacier may be immanent, the quickest it will occur is in 200 years, but could be more than 1,000 years away.
“Previously, when we saw thinning we didn’t necessarily know whether the glacier could slow down later, spontaneously or through some feedback. In our model simulations it looks like all the feedbacks tend to point toward it actually accelerating over time; there’s no real stabilizing mechanism we can see,” Joughin said.
The earlier predictions of this catastrophe were based on simplified models. However, the topography around Antarctica is so complex, a different method was used. Airborne radar developed at the University of Kansas was used to penetrate the thick ice, which displayed images of the underlying bedrock. The bedrock controls the ice sheet’s long-term stability.
NASA’s Operation IceBridge contributed the mapping, along with other instruments that measured the height of the ice sheet. In certain areas of the Thwaites Glacier there has been several feet of ice melt per year.
Using the data collected and UW’s own satellite, they was able measure the ice loss over the last 18 years and produced a model forward with different ice melt scenarios. Currently, the ice depth where the glacier meets the land is around 2,000 feet. The results show that when the edge of the ice retracts from the land, it will become steeper and, like a pile of sand, will collapse toward the sea. Using different ice melting speeds, the team was able to determine the quickest scenario of complete collapse would be in about 200 years and the slowest melt would collapse in about 1,000 years. However, the most likely time line would be between 200 to 500 years from now.
“Once it really gets past this shallow part, it’s going to start to lose ice very rapidly,” Joughin said. “All of our simulations show it will retreat at less than a millimeter of sea level rise per year for a couple of hundred years, and then, boom, it just starts to really go,” Joughin added.
Joughin relates this process to climate change, but other factors make it hard to predict the exact timeline.
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