Scientific understanding is continually shifting as time moves on. For decades now, scientists have assumed that ancient high tide lines referred to higher sea levels. These assumptions have led scientists to believe that if the Antarctic and Greenland ice sheets were to completely melt, they would cause such a high sea level again.
New research, however, has challenged these assumptions, by showing that the Earth’s hot mantle pushed up segments of ancient shorelines over millions of years, skewing what we thought we understood.
“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.”
In other words, the sea level is not just influenced by the amount of water going into it, but the level of activity going on underneath it as well.
“This study was the culmination of years of work and deep collaboration by researchers in CIFAR’s program in Earth System Evolution,” explains Rowley. “For this study, each of us brought our individual expertise to the table: Rob and Alex worked on simulations of Earth’s mantle dynamics, Jerry provided calculations on how glaciers warp Earth’s surface, and I shaped our understanding of the geology of the landscape we were looking at. This study would not have been possible without CIFAR.”
The research team, including CIFAR Senior Fellows Alessandro Forte (Université du Québec à Montréal) and Jerry Mitrovica (Harvard), and a former CIFAR-supported post-doctoral fellow Rob Moucha (Syracuse), studied the coast from Virginia to Florida which has a high-tide line much higher than current day levels. Previous research assumed that the presumed high sea level was caused by a collapse of the Greenland, West Antarctic, and a portion of the East Antarctic ice sheets, subsequently raising the sea level by 35 metres.
The new research, however, suggests that the ice sheets in question — specifically the East Antarctic Ice Sheet, the world’s largest ice sheet — were, and are, more stable than previously assumed.