For decades, scientists have used ancient shorelines to predict the stability of today's largest ice sheets in Greenland and Antarctica. Markings of a high shoreline from three million years ago, for example, when Earth was going through a warm period, were thought to be evidence of a high sea level due to ice sheet collapse at that time. This assumption has led many scientists to think that if the world's largest ice sheets collapsed in the past, then they may do just the same in our modern, progressively warming world. However, a recent groundbreaking study now challenges this thinking.
Using the east coast of the United States as their laboratory, a research team led by David Rowley, CIFAR Senior Fellow and professor at the University of Chicago, has found that Earth's hot mantle pushed up segments of ancient shorelines over millions of years, making them appear higher now than they originally were millions of years ago.
"Our findings suggest that the previous connections scientists made between ancient shoreline height and ice volumes are erroneous and that perhaps our ice sheets were more stable in the past than we originally thought," says Rowley. "Our study is telling scientists that they can no longer ignore the effect of Earth's interior dynamics when predicting historic sea levels and ice volumes."
The team studied the coast from Virginia to Florida, which has an ancient scarp tens of meters above present-day sea level. …