Field Work on the Greenland Ice Sheet, Part 2

Part 2: An Attempt at Science

Megan here-

If you haven’t read Part 1 of my Greenland field work experience, check it out here! If you have read it, you’re probably wondering what research we actually worked on for those three chilly weeks. What were our research goals? What type of data did we collect? And how did we collect that data? To answer those questions, I give you Part 2: An Attempt at Science.

The University of Wyoming and University of Montana’s glaciology group has become highly involved in Greenland Ice Sheet (GrIS) research over the past decade. Because the ice sheet has become of critical importance in our warming climate, many scientists are trying to better understand the dynamics of the GrIS. Our collaborative group asks questions such as, how does meltwater move through the ice sheet? What mechanisms are involved in ice sheet movement? Or, what conditions lay beneath the ice? Answers to these questions help us to better understand GrIS dynamics in a changing climate.

Figure 1. Glaciers are divided into different regions based on the processes and conditions of those areas. The ELA is the equilibrium line altitude where there is no net accumulation or melting. The ablation zone is at lower altitudes and defines the margins of the ice sheet where melting occurs. In contrast, the accumulation zone defines the area where there is net accumulation of snow. Within this zone is the percolation zone, where there is some melting and we see extensive layers of firn.

For this field season, we were mostly concerned with the first of those questions. More specifically, we ask: what is the fate of meltwater in the percolation zone? To better understand what the percolation zone is, let’s take a look at the different regions or zones of a glacier (Figure 1). Any glacier (or ice sheet) is divided into two main parts: the ablation zone and the accumulation zone. The ablation zone defines the lower elevations where there is net melting. In other words, over a year-long period this region has lost mass. The opposite is the accumulation zone. Here, there is net gain in mass due to snowfall. These two zones are divided by the equilibrium line altitude (ELA) where the amounts of accumulation and melting are equal. This may seem straightforward at first glance, but a rather unusual region exists within the accumulation zone. Just higher in elevation than the ELA, there is a section of the glacier where snow melts and percolates into the firn. Firn is just altered and compacted snow. We’re curious about the fate of meltwater in the percolation zone’s firn. When snow melts to water, does it flow into the firn and refreeze? Does it percolate all the way down to the glacial ice layers? Or does it runoff toward the terminus (“the snout”) of the glacier and reach the ocean?

Figure 2. We used a hot water drill to penetrate the upper 100 meters of the firn at our study site. The drillstem is attached to a long hose, which carries hundreds of gallons of hot water from a tub to the borehole. As the hot water is blasted at the cold firn, it melts the firn and creates a borehole.

To answer these questions, we used a variety of research techniques that look at the structure and temperature of the firn throughout the full depth of the percolation zone, which is thought to be less than 100 meters thick in this area. The five principle tools we used were coring, hot water drilling, videography, temperature sensors, and radar. Coring involves extracting long cylinders of snow, firn, and ice from the ground below us, and then logging the densities and structures of the core. To reach greater depths than with coring, we used a hot water drill to inject hot water into the ground and create a borehole (Figure 2). Once we had a completed 100-meter borehole, we extended a video camera down the hole to visual identify interesting structures (e.g. ice layers) in the firn. In both the hot water-drilled boreholes and the boreholes remaining from coring, we installed long strings of temperature sensors that measure and record the firn temperatures at increasing depths. These temperature data will be recorded for the next year or two, so we will return next summer to collect the data. The final technique we use, ground-penetrating radar, provides insight into the firn layers below our feet. By transmitting radio waves into the ground and then receiving the waves, we can observe variations in firn density and estimate water content. Together, these five techniques provide a means to better understand the behavior of meltwater in the percolation zone.

Before arriving in Greenland, I was highly intimidated by all of the research techniques we had planned to use. I had never been involved in a full field season, never cored or drilled firn, and never even stepped on a glacier for that matter. However, I found that the best way to learn something is to actually just try doing it. With the guidance of a patient and knowledgeable advisor, I learned more than I thought was possible in three short weeks. Being in the field provides such an excellent opportunity to take an immersive approach to science: living, working, and learning in the presence of what you study.

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