Antarctica: Thwaites Glacier Ice Shelf Has Thinned by up to 23 Percent Since 1970s

Researchers say that an ice shelf on the vast Thwaites Glacier in West Antarctica has been reduced in size by warming oceans more than previously thought.

According to a study published in the journal Proceedings of the National Academy of Sciences, the glacier's eastern ice shelf thinned between 10 and 33 percent between the years 1978 and 2009.

For the study, the scientists—led by Stanford geophysicist Dustin Schroeder—compared modern ice-penetrating radar records of Thwaites with data collected on around 250,000 flight miles-worth of 35-millimeter (mm) optical film between 1971 and 1979, which they painstakingly digitized by hand.

This is significant because most of this type of data was collected in the last two decades, limiting our ability to understand long-term processes in the behavior of ice sheets and make predictions for how their melting could impact global sea levels.

"This provides a baseline of observed subsurface change to compare with ice sheet and ocean models," Schroeder told Newsweek. "If we have confidence that these models can reproduce the observations for the last 40 years, then we have more confidence in their projections of the next 100 years."

Schroeder said that having this combined record of modern and older data enabled the team to see where the ice shelf is thinning the most.

"You can really see the geometry over this long period of time, how these ocean currents have melted the ice shelf—not just in general, but exactly where and how," Schroeder said in a statement. "When we model ice sheet behavior and sea-level projections into the future, we need to understand the processes at the base of the ice sheet that made the changes we're seeing."

"It was surprising how good the old data is," he said. "They were very careful and thoughtful engineers and it's much richer, more modern looking, than you would think."

The 1970s data—which was collected as part of a collaboration between Stanford and Cambridge University in the U.K.—shows several features that had previously only been observed in modern data, including ash layers from past volcanic eruptions and channels created by water that lies underneath the ice shelf.

The researchers say the latest findings have significant implications for predicting sea level rise by proving the scientific potential of digitizing older data.

Furthermore, studying Thwaites Glacier—which is about the same size as Florida—is important because it contains enough ice on its own to raise global sea levels by about two feet if it all melts, according to Public Radio International.

One team of researchers argued in a 2014 paper that Thwaites will likely suffer an irreversible collapse in the next 200 to 1,000 years. This could have wider knock-on effects because the glacier lies in the middle of the massive West Antarctica Ice Sheet, which is about the size of Mexico.

Scientists, think that the collapse of Thwaites could destabilize neighboring glaciers, potentially leading to sea level rise of up to 11 feet—enough to flood coastal cities around the world. At present, thawing from Thwaites—which has lost around 600 gigatons of ice in the past 40 years—contributes around 4 percent of global sea level rise, according to NASA.

"Thwaites is one of the fastest-changing, most-potentially unstable glaciers in Antarctica and, as such, understanding it is key for understanding the evolution and potential sea-level contribution of the whole ice sheet," Schroeder told Newsweek.

The article was updated to include additional comments from Dustin Schroeder.

Antarctica iceberg
View of an iceberg in Antarctica on March 5, 2014. VANDERLEI ALMEIDA/AFP/Getty Images