Published March 29, 2021
On the surface of Greenland’s mighty Helheim Glacier, huge, narrow cracks called crevasses act as a conduit to the subglacial world.
Meltwater flows into these fissures from a massive aquifer enclosed in the ice, and the weight of this liquid causes the fractures to grow ever deeper, until the cracks reach all the way down to the glacier bed. There, beneath a kilometer of ice, the falling water feeds a complex network of moving water channels that helps determine the speed at which Helheim Glacier sheds ice into the sea.
How does all of this happen? How fast do the crevasses grow? And what does the water system look like at the glacier bed?
This movement of water through and under Helheim Glacier — called hydrology — is the topic of a $2.2 million project that brings together researchers from UB, Georgia Institute of Technology and Dartmouth University. Funded by the Heising-Simons Foundation, the research has implications for predicting global sea level rise.
“When we talk about glaciers in Greenland, sometimes we refer to the ‘Big Three.’ Helheim Glacier is one of the three largest contributors of ice from Greenland to the ocean,” says Kristin Poinar, assistant professor of geology, College of Arts and Sciences, and a researcher in the UB RENEW Institute. “The subglacial hydrology of this glacier is not very well known, and we are trying to learn about it so we can understand how it might change in the future, and how the glacier will contribute to future sea level rise.”
Poinar is leading the effort with Winnie Chu, assistant professor of earth and atmospheric sciences at Georgia Tech, and Colin Meyer, assistant professor of engineering at Dartmouth.
Poinar’s portion of the grant — $770,000 — will be devoted to understanding how fast the crevasses reach the glacier bed after they form, and how this changes the patterns of water flow and ice flow.
This work will help scientists understand whether water flows in a fairly consistent manner to the glacier bed from the aquifer, which lies about 15-20 meters below Helheim’s surface at the study site, about 35 kilometers upstream of where the glacier starts shedding ice into the ocean.
As Poinar explains, outlet glaciers like Helheim aren’t just stagnant towers of ice and snow. Instead, they are akin to rivers, their frozen contents flowing toward the sea. The crevasses that form in the glacier travel with the ice, slowly edging downstream.
But the aquifer largely stays put.
“The whole glacier is moving, and the aquifer is basically staying in the same place,” Poinar explains. “So if you have a crevasse that reaches all the way down to the glacier bed, this crevasse is going to leave the aquifer behind one day, and the glacier bed below it will be cut off from this water source.”
Additionally, when new cracks that form upstream get deep enough to reach the aquifer, they will begin to draw from the water, and can block the water from reaching the deeper crevasses that feed the glacier bed.
“What we want to know is how fast new crevasses that form on the surface take to reach the glacier bed,” Poinar says. “It’s important to know the time-scale of this process of hydrofracture. If the glacier bed is without a water source for a few days, that’s one thing. But if it’s without a water source for a couple of months, that has a good chance of changing the ice flow rates above it and downstream below it.”
Poinar will lead field expeditions to Greenland over three summers, starting in 2022. The teams will include UB scientists, including students, as well as mountaineers who will help to navigate the difficult terrain.
The researchers will install GPS units on either side of various crevasses to monitor their movement downstream and also measure how fast the cracks grow — as the fractures get deeper, they also tend to widen at the surface.
Poinar, along with teams led by Chu and Meyer, plans to install other instruments at Helheim Glacier to measure weather conditions, including air temperature, wind speed, humidity, atmospheric pressure and snow accumulation. The team will also use various radars, geophysical techniques and models to learn more about what the aquifer and the water networks at the glacier bed look like.
This knowledge will enable scientists to better understand many aspects of the hydrology of Helheim Glacier, impacting the flow of ice to the sea.