Into the Ice

Scientists Discover Hidden Glacial Crevasses

It’s not the Boy Scouts, but in his line of work Joel Harper adheres strictly to the old scouting motto

of “be prepared.”

Harper, a UM associate professor of geosciences and renowned glaciologist, has spent nearly three years of his life camped out on snow in remote areas of places such as Greenland and Alaska, studying changes in glaciers and ice sheets and their effect on sea level.

“When you conduct the type of research we do, preparation is extremely important,” Harper says. “You have to have everything you need with you. You can’t just run to the hardware store to buy a part or a tool.”

Being prepared, paying attention to detail and a lot of hard work helped Harper and his colleagues uncover some very interesting findings while conducting research in Alaska’s Chugach Mountains. The results of the four-year study recently were published in Nature, a prestigious science journal.

The paper – which he wrote with Boise State University radar specialist John Bradford, University of Wyoming glaciologist Neil Humphrey and UM graduate student Toby Meierbachtol – unveiled promising research that could have a significant impact on the study of climate change.

The Alaskan study involved drilling holes 200 meters deep into the glacier with a drill that produces a jet of hot water.

 “We drilled the holes with the intention of measuring what was happening to the water pressure underneath the glacier,” Harper says. “We soon realized that we were intersecting something within the glacier that was sucking all of the water away from our boreholes.”

What Harper’s team discovered was evidence that there are huge crevasses filled with water at the bottom of glaciers. The crevasses fracture upward into the ice from below and do not reach the surface of the glacier.

 “Prior to this, people thought that the water flow at the bottom of glaciers was confined to just a small interface between the ice and the bedrock,” Harper says. “That’s not always the case. In some cases, the water extends way into the ice through huge crevasses. The reason this matters is that before we can understand how fast glaciers move when they have water under them, we need to learn more about the configuration and pressure of water flowing under the ice.”

One major barrier to modeling the motion of glaciers and ice sheets has long been uncertainties related to the physics that govern ice sliding over bedrock in the presence of water. One can imagine that water would lubricate a glacier’s bed and cause the ice to slide faster over its base. Indeed, Harper’s Alaskan-study glacier experiences a fivefold increase in velocity when spring meltwater first reaches the glacier’s bed. But, mysteriously, continuing to add more water does not necessarily lead to faster motion. The study glacier slows down later in the summer despite hot days with heavy melting of snow and ice. The basal crevasses may offer one explanation.

 “The crevasses potentially act like a sponge, absorbing excess meltwater and modulating the pressure of the water under the glacier,” Harper says.

To learn more about how the crevasses might do this, the researchers measured the water pressure under the glacier using sensors installed at the bottom of their boreholes. They also conducted radar and seismic imaging experiments designed to determine the volume of water in the crevasses.

On to Greenland

With the success of the Alaskan study, Harper and his colleagues now have set their sights on Greenland, a place where he has conducted other glaciology research for the past five summers.

 “After we finished in Alaska, we decided we needed to drill into a bigger ice sheet where this stuff really matters,” Harper says.

The Greenland project is a three-year study funded by $3.2 million in research grants from the National Science Foundation and a Scandinavian research consortium. Last summer Harper’s team drilled 13 holes in the ice sheet in west central Greenland.

 “It’s really in the middle of nowhere,” Harper says. “We had to fly our drill to Greenland on an Air National Guard C-130 transport plane and then move it to the research site with a helicopter.”

Complicated logistics must be in place to move people and equipment around remote areas of the Arctic. “This year we had a major crisis after the helicopter we chartered was in a minor crash and was grounded,” Harper says. “I was on the satellite phone desperately trying to arrange another helicopter from elsewhere in the Arctic to come move our drill. It looked like the field season was over, and we had just gotten started. We eventually found a machine, but we had to pay a fortune for it to make a long commute to us.”

The drill used by the research team was specially built in a machine shop at the University of Wyoming. It is equipped with four high-powered water heaters, two high-pressure pumps, several generators and three kilometers of hose that hot water is pumped through.

During the initial phase of drilling, the team went down about 2,100 feet. Next summer, Harper says, they hope to drill holes that are almost a mile deep.

 “That’s a deep hole considering we are just a couple of professors and a few students using a homemade system,” he says. The ice is about minus 20 degrees Celsius, and the water-filled hole slowly freezes closed while the drill is moving forward.

 “We have to move quickly and drill the hole in one straight shot before the hole freezes completely closed and we lose our drill,” Harper says.

The deepest holes are expected to take about 22 hours to complete, and then the researchers will have less than two hours to complete their experiments before the hole completely freezes shut.

“Lots of Red Bull and coffee are key,” Harper says. 

During the summer months in Greenland, it never gets dark. But it can be very cold, with temperatures sometimes dipping down to nearly minus 30 degrees Fahrenheit.

 “You’ve got to be careful to pick the right people for working long days for up to six weeks straight in conditions that can be difficult,” Harper says. “All of the research team must undergo a major medical exam before going on the expedition.”

The big picture

When Harper is asked to explain why his research is important, he’s quick with an answer.

“We know that sea level is currently coming up,” he says. “But we need to make sure we can make accurate projections about future change, especially how fast sea level rise can occur. Overpredicting future sea level rise is just as detrimental to society as underpredicting. There are about 145 million people living within one meter of sea level. And most of those people are in developing countries where there are few resources to combat the rising sea.

“As the climate warms, you get a certain amount of ice turned into water due to melting,” Harper says. “But sea level doesn’t come up that quickly just from melting.”

The rapid sea level rise comes from ice being dumped into the ocean, which is known as calving. Glacier speed influences sea level through calving of icebergs into the ocean, where faster-moving glaciers produce more icebergs. “We can make good estimates of how much ice will melt,” Harper says, “but we know very little about how calving rates might change.”

By the year 2100, current projections call for sea level to rise between 18 and 59 centimeters. But Harper says this projection comes with a big caveat: It is based on no change in iceberg calving rates.

 “This assumption was necessary because we have little idea how to estimate what will happen,” he says. But with 60 meters of potential sea level rise locked up in glaciers and ice sheets worldwide, and with six meters in Greenland alone, there is certainly potential for greater amounts of sea level rise. The big question is how much and how fast is reasonable. The answer to that question boils down to how fast glaciers can move and dump ice into the ocean.

This issue was the focus of a 2008 paper Harper published with colleagues in the journal Science, in which they argued that two meters of sea level rise by 2100 was plausible, but more than that requires glaciers to move unrealistically fast.

“That was a ballpark estimate on the ceiling for sea level rise,” says Harper. “Now one of the things I’m working on is the interaction between water and glacier motion, so that we can eventually produce more refined estimates.”

Getting a good grasp on the implications of calving is why Harper and other researchers are willing to spend their summers camped out on frigid ice sheets.

“When I began studying glacier mechanics as a graduate student, this was a pretty esoteric area of research,” Harper says. “Now this field is in the spotlight, and we find our science playing an important role serving society.”

For more information, email joel@mso.umt.edu.