Robert Moucha, an assistant professor of Earth sciences at Syracuse University, is a co-author of a recent study that found that a portion of the East Antarctic ice sheet was at a significantly lower elevation 3 million years ago — during the mid-Pliocene Warm Period — than it is today.

The decrease in elevation resulted in the grounding line — the point at which glaciers begin to float, rather than resting on bedrock — retreating, which raised the global sea level, the study also found.

“The stability of the ice sheet is affected by the position of the grounding line, a line that separates ice that floats from ice that rests on the bedrock,” Moucha said. “Simply, the more bedrock the ice sheet is supported by, the more stable it is.”

Moucha said sea level rise has enormous societal implications, and that it is important to understand how these ice sheets have responded to past periods of warming.

In the paper, which was published in the journal “Geology,” Moucha — along with other co-authors from Harvard University, Columbia University, Pennsylvania State University, the University of Massachusetts Amherst, Université du Québec à Montréal and the University of Chicago — looked at elevation changes over the last 3 million years of the bedrock on which the Antarctic ice sheets rest.

In past studies, researchers assumed that bedrock elevations have not changed, and that they were similar to the elevations seen today, Moucha said.

Scientists have known that convective mantle flow, or flowing rock on the interior of the earth, deforms the surface of the planet, and that these deformations leave hundreds of miles of gently rolling surface deflections of the bedrock, Moucha said.

The paper used models of these bedrock deformations to study how the Antarctic ice sheets responded to these geological changes and climate forcing over the last 3-4 million years, Moucha said.

During the mid-Pliocene warm period, mean global temperatures were between 2 and 3 degrees Celsius warmer than pre-industrial levels, according to the Intergovernmental Panel on Climate Change (IPCC). Additionally, sea level was at least 15-25 meters higher than it is today, according to IPCC.

This history can help scientists picture what future sea level rise will look like, Moucha said. The United States Environmental Protection Agency estimates sea level rise connected with global climate change to be between 1-4 feet by the year 2100.

The study may change the way scientists calculate estimates for potential sea level rise, Moucha said.

“In a sense, this past scenario can perhaps offer us a glimpse of what to expect, but we still need to refine the range and modeling of ice sheets under different climate scenarios,” Moucha said.

Published on February 14, 2016 at 10:43 pm