“The Greenland Ice Sheet could contribute up to seven meters of global sea-level rise if it were to melt,” says OSU marine geologist Joseph Stoner. “We don’t know if it’s going to melt, but that’s how much water is in the ice sheet. Therefore, we need to better understand the processes at work.”
In search of that understanding, Stoner and researchers at the University of Wisconsin-Madison are studying sediments flowing seaward in streams and rivers on the island’s southern tip. Those sediments—remnants of bedrock pulverized over eons by grinding glaciers and rushing rivers—hold clues to the ice sheet’s history across geologic time. Scientists know that the 680,000-cubic mile chunk of snow, compressed from white to crystalline blue over many millennia, is receding. Satellite images from the past several decades show significant shrinkage. What isn’t known is the speed of melting or the extent that melting might take in coming years. By studying Greenland’s past with support from the National Science Foundation, Stoner and his colleagues hope to bring its future into clearer focus.
“The key to understanding the Greenland Ice Sheet is to use the natural record of past variability as a sort of a manual as to what it could do in the future,” says Stoner. “We’re trying to use the natural geological archive to test how the ice sheet works.”
To recreate the ice sheet’s prehistoric behavior, he and his graduatestudents collected sediment samples. Tracing the origins of these silts and sands should tell the researchers where the island was exposed during “interglacial” periods—warm stretches between ice ages—and where it lay buried beneath tons of frozen snow during colder periods.
The markers that will reveal these ancient patterns are both chemical and magnetic.
To read magnetic profiles of sediments, Stoner’s lab recently acquired a new-generation instrument: a superconducting magnetometer for measuring the magnetic properties and composition of rocks. Instead of using liquid helium as a coolant like old-style cryogenic magnetometers do, this one compresses helium gas till it reaches 3.5 degrees Kelvin, “Just a little above absolute zero,” Stoner says. “It works through superconductivity, which only happens at extremely cold temperatures.”
Stoner’s findings could cause scientists to rethink Greenland’s role in climate-change scenarios.
Article courtesy of the College of Earth, Ocean, and Atmospheric Sciences 2010 Research Highlights
Photo courtesy of Terra Magazine