Among global warming’s most frightening threats is the prediction that the polar ice caps will melt, raising sea level so much, that coastal cities from New York, to Los Angeles, to Shanghai will be flooded.
Scientists agree that they key player in this scenario is the West Antarctic ice sheet.
A Brazil size mass frozen water that as much as 7,000 feet thick, unlike floating ice shelves which have little impact on sea level when they break up, the ice sheet is anchored to bedrock will blow the sea surface.
Surrounded by an open ocean, it is also vulnerable.
But Antarctic experts disagree strongly on just how unstable it is.
Now new evidence reveals that all are most of the West Antarctic ice sheet collapsed at least once during the past 1.3 million yearsa period when global temperatures probably will not significantly higher than they are today.
And the ice sheet was assumed to have been stable.
In geologic time, a million years is recent history.
The proof which was published last week in Science comes from a team of scientists from Uppsala University in Sweden and Californian Institute of Technology who drill deep holes near the edge of the ice sheet.
Within samples collected from the solid substance lying beneath the ice, they found fossils of microscope marine plants which suggests the region was once an open ocean, not solid ice.
As Herman Ankleherd, a co-author from Californian Institute of Technology says,
“The West Antarctic ice sheet disappeared once and can disappear again.”