Field Notes: The Polar Field Services Newsletter

Studying Complex Glacial Hydrology

Dr. Ginny Catania and colleagues are studying glacial hydrology at remote sites near Swiss Camp in Greenland. After setting up GPS units to measure ice movement last summer, the team plans several 2011 field work expeditions to gather data. All photos: Matt Hoffman

Scientists have predicted that if Greenland’s glaciers melted, sea level could rise up to six meters, devastating coastal cities and having enormous impacts. Consequently, understanding the complex dynamics of the country’s glaciers—both coastal and inland—has become increasingly important.

Given the widely accepted evidence that Greenland loses more ice mass than it gains every year, some glaciologists have begun pursuing the question of what factors influence and expedite glacial melting.

Studying water and ice

Enter Dr. Ginny Catania, a glaciologist and polar adventurer with the Institute for Geophysics at The University of Texas at Austin (UT). Dr. Catania is the principal investigator on an NSF-supported project called “ROGUE: Real time observations of Greenland’s under-ice environment.

The project is collaborative across two US-based institutions—UT and Dartmouth College, NASA researchers and colleagues at ETH in Switzerland.

“Greenland is losing ice, and the fast moving glaciers are accelerating,” says Dr. Catania. “We are interested in what happens to land-terminating glaciers when surface melt water travels to the glacial bed. There is evidence that the melt lubricates the bed, and the glacier can speed up.”

Post-doctoral fellows install GPS units to measure glacial activity.

When that happens, the glacier moves from higher to lower elevations where warmer temperatures expedite melting.

Looking at the entire glacier, from surface to bed

Specifically, Dr. Catania and her team aim to examine the nature and cause of short-term ice velocity changes near Swiss Camp, Greenland. They will be studying the interactions between the ice sheet, the atmosphere, and the bed through an integrated observational approach that involves borehole geophysics, surface-based measurements, satellite data and modeling.

Following the flow

Want to find a moulin? Just follow the stream.

Their work will focus on the hydraulic system underneath the glacier. Taking precise measurements, the team aims to investigate how surface water travels to the bed of the glacier, causes it to slide and how this system evolves through the melt season.

As a result, the top of the ice may move at a different speed than the bottom of the ice, which at times is sliding on a water layer at the base of the ice sheet.

“We want to measure the amount of sliding at the base,” says Dr. Catania.

Planning and operations

After selecting 3 sites last summer, a small team will travel to Swiss Camp in May to set out GPS measuring devices on the glacier surface. Then, from June through August, researchers will drill a total of 18 boreholes at three different sites with differing ice thicknesses of 650 meters, 750 meters and 850 meters.

The team will place instruments near the base of the ice sheet to measure water pressure—or the amount of overlying water in the borehole column.  This water level will fluctuate over daily/seasonal/yearly time scales, says Dr. Catania.

“Monitoring the water levels over time allows us to understand how the water is moving under the ice sheet,” she says.

Understanding ice dynamics

In addition, the boreholes will allow scientists to measure how the ice deforms to determine how much of the surface speed (measured by GPS) is due to ice deformation.

By directly observing the basal processes, the team will develop a more precise understanding of the evolution of what happens when water from a glacier’s surface travels to its bed.

Moulins

Moulins like this one provide routes for surface water to travel to a glacier's bed.

Scientists already know the water descends through features known as moulins, which are naturally occurring and prevalent on glaciers. Dr. Catania’s team will drill near existing moulins this summer.

Not your average drill

The drilling itself is no easy feat. The drill is a high-pressure, hot-water drill that can quickly reach the base of the ice sheet in a day.

“There are lots of GPS on the ice sheet surface, but we don’t yet know how much of the glacier’s movement is due to sliding on the bed or how much is ice deforming,” says Dr. Catania. “We will be able to measure deformation, and we’ll measure sliding.”

A glacier’s surface speed can be different than the speed the ice moves at the base, where the glacier meets the ground.

The team will also measure water quality, testing for salinity to understand where the water in the boreholes comes from. Water that is closest to the glacial bed will be saltier. They also plan to send down cameras, which, if successful, will allow them a rare glimpse of the glacial bed.

Improved modeling

The data collected will be correlated to melt and surface water volume proxies based on remote sensing data, meteorological data available from surface-based weather stations and measured lake volume.

This research will be part of a growing movement to better understand how glaciers work, says Catania. By developing a better understanding of how water gets to a glacier bed and what impact that has on ice speed, the scientists will produce data that can help modelers better predict the causes and impacts of glacier melt.  —Rachel Walker

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