San Francisco—Scientists who study the melting of Greenland’s glaciers are discovering that water flowing beneath the ice plays a much more complex role than they previously imagined.
Researchers previously thought that meltwater simply lubricated ice against the bedrock, speeding the flow of glaciers out to sea.
Now, new studies have revealed that the effect of meltwater on acceleration and ice loss -- through fast-moving outlet glaciers that connect the inland ice sheet to the ocean -- is much more complex. This is because a kind of plumbing system evolves over time at the base of the ice, expanding and shrinking with the volume of meltwater.
Researchers are now developing new low-cost technologies to track the flow of glaciers and get a glimpse of what lies beneath the ice.
As ice melts, water trickles down into the glacier through crevices large and small, and eventually forms vast rivers and lakes under the ice, explained Ian Howat, assistant professor of earth sciences at Ohio State University. Researchers once thought that this sub-glacial water was to blame for sudden speed-ups of outlet glaciers along the Greenland coasts.
“We’ve come to realize that sub-glacial meltwater is not responsible for the big accelerations that we’ve seen for the last ten years,” Howat said. “Changes in the glacial fronts, where the ice meets the ocean, are the real key.”
“That doesn’t mean that meltwater is not important,” he continued. “It plays a role along these glacial fronts -- it’s just a very complex role, one that makes it hard for us to predict the future.”
In a press conference at the American Geophysical Union (AGU) meeting in San Francisco on Wednesday, December 16, 2009, Howat will join colleagues from the University of Colorado-Boulder/NOAA Cooperative Institute for Research in Environmental Sciences (CIRES) and NASA’s Jet Propulsion Laboratory (JPL) to discuss three related projects -- all of which aim to uncover how this meltwater interacts with ice and the ocean.
Their work has implications for ice loss elsewhere in the world -- including Antarctica -- and could ultimately lead to better estimates of future sea level rise due to climate change.
Howat leads a team of researchers who are planting inexpensive global positioning system (GPS) devices on the ice in Greenland and Alaska to track glacial flow. Designed to transmit their data off the ice, these systems have to be inexpensive, because there’s a high likelihood that they will never be recovered from the highly crevassed glaciers.
Howat will describe the team’s early results at the AGU meeting, and give an overview of what researchers have learned about meltwater so far.
John Adler, a doctoral student at CIRES, works to calculate the volume of water in lakes on the top of the ice sheet. These lakes periodically drain, and the entire water volume disappears into the ice. He uses small unmanned aerial vehicles to measure the ice’s surface roughness -- an indication of where cracks may form to enable this drainage to happen. Other members of his team are releasing GPS-tagged autonomous probes into the meltwater itself, to follow the water all the way down to the base of the ice sheet and out to sea.
“My tenet is pushing the miniaturization of technology, so that small autonomous platforms -- in the sea, on the surface, or in the air -- can reliably gather scientific information in remote regions,” Adler said.
All these efforts require cutting-edge technology, and that’s where Alberto Behar of JPL comes in. An Investigation Scientist on the upcoming Mars rover project, Behar designs the GPS units that will give researchers the data they need.