The BeWise project’s highly successful second season
Having returned from his second trip to Antarctica to conduct research for the BeWise project funded by the InBev Baillet-Latour Fellowship, Dr. Reinhard Drews from the Glaciology Laboratory at the Université Libre de Bruxelles (ULB) in Belgium reports on the accomplishments during his time in Antarctica.
What are the objectives of your research?
The overarching goal of the BeWise project has been to get some field data to help us understand the buttressing effect of ice shelves in Antarctica. Ice shelves are extensions of ice that flow off the ice sheet covering Antarctica out over water, where they can stretch for long distances.
The Roi Baudoin Ice Shelf is a good example to look at because it has two interesting features: The first is what we refer to as a pinning point on the western side of the ice shelf. A pinning point is where an ice shelf – which floats over water – becomes grounded again on a topographical feature (a rocky protrusion, etc.) underneath the ice shelf. The pinning point provides a lot more friction against the outward flow of the ice shelf all of a sudden, so the flow of the ice shelf slows down a lot around a pinning point. The second is the Derwael Ice Rise. An ice rise is a grounded feature within an ice shelf. The grounded area is large enough that the ice flow on the ice rise is entirely local, and not majorly influenced by the surrounding ice shelf.
So we're interested in studying how much this point controls the overall flow dynamics of the ice shelf, and ultimately if this controls the flow of ice coming off the ice sheet behind it.
This is the second season in a row that you've gone to Antarctica under the InBev Baillet-Latour Fellowship. Last year you were taking GPS and radar measurements on the Roi Baudoin Ice Shelf. What kind of measurements did you take this year?
Last year we took radar measurements at both the Derwael Ice Rise and the pinning point on the Roi Baudoin Ice Shelf. We were able to collect hundreds of kilometres of radar data and obtained good thickness profiles of the ice shelf. We also placed metal markers on the surface of the ice shelf and measured their exact location via GPS. Our objective was to measure the velocity of both the grounded and the floating ice, and to determine how this velocity changes spatially.
When we got back to the ice shelf this year, we were able to find back about 60% of the markers we planted the year before. Some may have been blown away by strong winds, or completely covered in snow, but we had more than enough to collect the data we needed. We took their new position via GPS to see how far the ice had had moved over the course of a year.
How far did the ice in the ice shelf flow in a year?
The ice flowed between 100 and 200 metres – which is about what we expected, and we knew this before form satellite measurements. But measuring the ice velocity with stakes provides more precise information about the ice shelf, how the ice deformation works, and how this compares to what we see in satellite images. It helps to have ground measurements to calibrate satellite measurements. It will be a while yet before we can say anything more precise about the movement of the ice, since the post-processing will take some time.
Did you do more radar profiling this year?
Last year we did a lot of direct radar profiling of the ice shelf. This year we did a kind of wide-angle survey of the ice shelf by pulling the antennae on the apparatus apart as we took an image of the same point. Doing this allows you to get a vertical velocity profile of the electromagnetic wave within the ice.
How exactly does taking an ice velocity profile work?
The electromagnetic waves have a certain recognizable speed as they travel through the ice shelf as a function of the density of the ice. The denser the ice, the slower the wave speed. We can measure how the density of the ice differs spatially using the wide-angle radar methods, and from this, we can infer the density distribution around the ice shelf.
You can use the density profile for multiple things. We'd like to know how much marine ice is on the bottom of the ice shelf.
What is marine ice?
Sometimes a certain kind of ocean circulation called an “ice pump” starts below the ice shelf. It can lead to melting of the ice shelf at the grounding line (the point where the ice flows off the continent and starts flowing out over the water). The melting water leads to a flux of fresh water leaving the ice-shelf cavity, which mixes with the more saline sea water and then re-freezes onto the bottom of the ice shelf.
So we call this marine ice, as opposed to meteoric ice, which comes from snow accumulation that over time transforms into the ice that comprises the ice sheet.
We can't see the marine ice beneath the ice shelf with normal radar imaging, because of the salt content in the ice. The radar signal we send out form the surface of the ice shelf gets attenuated when it reaches the marine ice.
How do you use the density profile?
If we have the density profile of the ice shelf, and if we apply the flotation criterion (Archimedes' principle of buoyancy), we can get an idea of whether there's marine ice on the underside of the ice shelf. Once we have this information, we understand better how the ice shelf deforms. Marine ice doesn't necessarily deform in the same way that meteoric ice does.
What was your journey like out to the Roi Baudoin Ice Shelf from the Princess Elisabeth station?
We were three scientists and two field guides. For the scientists, we had Lionel Favier, also a scientist from the Glaciology Laboratory at the ULB on his first trip to Antarctica, and Nicholas Bergeot from the Royal Observatory of Belgium, who is a real GPS specialist. Nicholas is working on the ICECON project, which is focusing more on the Derwael Ice Rise, but he helped us out a lot with the work we had to do. And of course we had two excellent field guides who helped us a lot, Alain Hubert and Kristof Soete.
We left the station with two snow tractors, each of which pulled a number of containers that we used as living quarters during the nearly two weeks were were in the field. It took between 17 and 18 hours to get from the station to the ice shelf. Once we arrived, we built a small camp and used skidoos to drive around locally to get to places on the ice shelf where we needed to do our GPS and radar measurements. We spent half our time on the ice shelf, and half our time on the Derwael Ice Rise.
I understand you were making fresh bread while you were in the field?
It was Alain and Kristof who were doing that. They have a bread machine now. It was really nice to have fresh bread every morning.
Over the two seasons that you went to Antarctica to collect data for Be:Wise, were you able to get all the data you need for your research project funded by the InBev Baillet-Latour Fellowship?
In any research project where you have to do field work, in the beginning, you make a plan, and the plan almost always changes as you have to adapt to the challenges and limitations you face on the ground once you arrive.
Looking back, we accomplished a lot more field work than we thought I would. We were able to get more radar and GPS data than we'd initially planned to get. So that was a pleasant surprise. It's sometimes the other way round for field work in Antarctica. You often end up accomplishing less than you set out to do.
Why were you able to accomplish more than you expected in your opinion?
First of all, we had very good weather. During the two seasons I went to Antarctica, we never had a bad weather day when we were doing field research on the Roi Baudoin Ice Shelf.
Secondly, we had very good support from the Princess Elisabeth station team. Alain and Kristof, our versatile field guides, not only checked for crevasses and mapped out where we could and couldn't go for safety reasons, but they also took part in the field work by collecting data with us. We showed them how to use the instruments and they collected data really well. If you have two more people in the field team who are collecting data for you, it really makes a huge difference in how much data you can get while you're in the field.
Were you able to learn anything interesting from the data you were able to gather?
Having a preliminary look at the data, it turns out that the dynamics of ice shelf are a lot more complex than I was initially expecting. But that's the way science goes!
If you look at the thickness of the ice at a particular spot on the Roi Baudoin Ice Shelf, you can see what we call “sub ice shelf channels”. There's a certain topography in the surface of the ice shelf. There are areas with surface depressions only a few kilometres wide. Given that ice shelves are typically very flat over many tens of kilometers, this is quite dramatic. It turns out that the surface depressions corresponds to sub ice shelf channels that take up half of the thickness of the ice shelf.
How sub ice shelf channels form and how they affect the stability of the ice shelf is a hot topic at the moment in glaciology. There are quite a few of these channels in the Roi Baudoin Ice Shelf. It's very exciting. It's hypothesized that the formation of sub-surface ice channels are somehow linked to the ocean circulation beneath the ice shelf, subglacial melting and freezing. But these processes are tricky, and it will be some time before we understand them better.
Once you publish your findings from the data you gathered in Antarctica, will you be finished with the BeWise project
I have six months to hand in the final report. I'm certain that by the end of those six months, we'll have the first publishable results. But at the same time, can you ever really finish looking at data? You can always find something new in the data if you take even more time to squeeze everything you can out of it.
Any other comments on your time in Antarctica?
I'd like to say a word about the InBev Baillet-Latour Fellowship. I have to say it's a very unique opportunity for young researchers. You get two years of research in Antarctica funded. You just have to think of a research project that makes sense to conduct in the vicinity of the Princess Elisabeth station, and you can carry out the research with a lot of freedom.
I feel really lucky that I had this opportunity, and I think they should keep the fellowship going so other young researchers can have the same opportunity. There aren't many opportunities out there for young researchers to get that kind of money. I encourage researchers to apply for the fellowship.
Picture: Reinhard Drews and Lionel Favier from the BeWise project take a profile of the ice shelf using ground penetrating radar - © International Polar Foundation