Predicting climate change

Over the course of millions of years, the edges of the Antarctic ice sheet have advanced and retreated numerous times. While melting ice from the most recent retreat 19,000 to 9,000 years ago raised sea levels by more than 26 feet, much less is known about prior retreats.

Stefanie Brachfeld, earth and environmental studies professor and department chairperson, has received a three-year grant from the National Science Foundation’s Antarctic Earth Sciences Program to go back even further in time – 240,000 years – to understand how Antarctic ice retreats and which parts of the ice sheet are most likely to retreat. By pinpointing when and where the ice destabilized in the past, she and her team will be able to predict how Antarctic ice will behave in a warming climate.

Brachfeld’s project collaborators, Trevor Williams, the lead principal investigator at Columbia University’s Lamont Doherty Earth Observatory (LDEO), Sidney Hemming from LDEO and Kathy Licht at Indiana University-Purdue University Indianapolis, will travel to Antarctica’s Weddell Sea embayment in November to collect samples from glacial moraines, ridges of debris that form on the edges of glaciers as they move and erode the underlying bedrock.

Her collaborators at the Alfred Wegener Institute in Germany will give the researchers access to Weddell Sea sediment cores that contain ice rafted debris layers called IRD. The IRD layers consist of sediment grains eroded by ice sheets, trapped in floating icebergs and released to the ocean when the iceberg melted.

“These layers are indicators of past episodes of iceberg generation and ice sheet retreat,” Brachfeld explains.

The project provides funding for a graduate assistant and undergraduate student to use light and electron microscopy to conduct laboratory analyses of the IRD. 

“We’ll need the full three years to analyze everything,” Brachfeld says. “Our specialty at Montclair State is the use of iron oxide minerals as forensic tracers. If we know the local geology of Antarctica, which we will determine from the moraines, we can then trace the iron oxide mineral grains back to their source and identify which part of the ice sheet destabilized and generated the icebergs.”

Much of the ice covering western Antarctica may well have melted at 130,000 and 240,000 years ago, explains Brachfeld.

“Those time intervals can be used as an analogue of what we can expect over the next several centuries as temperatures continue to warm,” she says.