On the ice

I came to Tromsø because I wanted to experience the polar night and the midnight sun. I wanted to feel what a year in the Arctic is like. I came to Norway because I wanted to be inspired by the Norwegian’s attitude towards and connection to nature. I wanted to climb mountains and sleep out in the snow. But first and foremost I wanted to come to UiT The Arctic University of Norway to steer my studies towards polar climate research and learn about ice and snow. Yesterday, I finally had a chance to do the latter in a sea ice sampling field day and I am excited to take you along on this impressing experience.

My day started at 6 o’clock in the morning with getting ready for a whole day out on the ice. I prepared some warm tea in my thermos, dressed in multiple layers of my warmest clothing and checked my hiking backpack full of equipment one last time. The weather was not forecasted to be very cold, but even at a few degrees below zero anyone gets cold by standing on the ice for seven hours. When I came to Tromsø I quickly learned that wool is the only material that reliably keeps you warm even if you get a bit wet. Thus, I was wearing two woolen base layers, a thick woolen sweater and a wind- and waterproof outer layer. I was happy to be able to borrow some of the warmest clothes from friends: enormous warm boots from my Norwegian roommate and an incredibly warm hat and down jacket from my former host family. My backpack was filled to the top with all that could keep me warm: a complete spare set of clothes in case I got wet, chemical hand and toe warmers and my little gas cooker – just in case. Additionally, I had a snow shovel, camera and notebook with me for documenting our work on the ice.

Heavily packed I made my way to university where I would meet the other twelve participants and six instructors of the course. The field day took place in Ramfjorden, at the tip of the tail of the sea troll that lives in the fjords around Tromsø (you can spot it on the map if you use some imagination). On the thirty minute taxi ride I admired the black and white landscape and frozen waterfalls we passed and my excitement grew the closer we got. Ever since I read the book “Eingefroren am Nordpol” in which Markus Rex portrays his experiences on the MOSAiC expedition, I dreamed about experiencing and doing research on the Arctic sea ice. Our little field day on fjord ice would certainly not be the same as being on sea ice next to the frozen fast Polarstern in the center of the Arctic, but it was certainly the closest I got to it so far and I had to start somewhere.

Finally, we unloaded our personal and the sampling equipment, stripped the latter onto the pulks (orange sledges to be dragged over the snow) and made our way towards the ice. We went through the safety rules and procedure of the day once more and set out to erect our little base camp away from the shore and on the deeper water. The first steps on the ice felt weird but after I was sure that the ice was thick enough to hold all of us, I felt only excitement about being on the sea ice. We set up a red tent in case we needed wind cover and the instructors demonstrated the two tasks of the day: drilling ice cores and making a snow pit.

The weather conditions could not have been more favorable. We measured air temperatures of around -2°C, there was lots of fresh snow from last night and it was mostly clear with occasional snow fall. As my group was preparing for making a snow pit, the sun actually came out, a very rare occasion lately. This also meant that we had to set up our snow wall facing away from the sun, so that the warmth of the sun would not alter our temperature measurements or melt the snow we were studying. A snow pit is used for studying all kinds of characteristics of the snow on top of the ice. We dug a clear wall in the snow with our shovels and started by measuring the depth and layer structure of the snow. In our snow pit the snow was 21 cm thick, which later turned out to not be very representative of the snow thickness on the study site, which was around 13 cm for the most part. For educational purposes however, our snow pit was very good. We identified three layers in the snow. The thickest top layer was very loose and made up of the fresh snow fallen the night before. Beneath there was a thin icy crust which likely resulted from the snow crystals breaking apart in the strong winds we had two days before. The bottom layer was made up of much denser snow which must have been on the ice for some time longer. We characterized the different layers by their thickness, hardness and snow appearance. For the latter we inspected the snow grains on a 2 mm grid under a magnifying glass and tried to decide whether they were solid faceted crystals or rounded faceted crystals. One of us documented all our findings on a standard snow pit sheet from the Norwegian Polar Institute. We had to document the exact GPS position and time of our sampling, weather conditions and temperatures of air, water and the snow at regular intervals. Next, we took density measurements of the two thicker snow layers by stabbing a container of known volume into the ice and weighing it on a small scale. As suspected, the upper layer was much less dense than the lower layer. Last, I took a photo of the snow surface profile as the roughness of the snow is among the most important factors influencing remote sensing images of snow on sea ice. Work in the snow pit was not very exciting, but I found it fascinating to examine the snow from close up and asked many questions about how different conditions affect the snow properties and the radar satellite images.

In the lunch break I warmed up with hot tea and talked to some of the other participants. Our group was about half physicists and half biologists which gave quite a variety of different perspectives to the sea ice sampling. I learned about the ongoing debate between sea ice biologists and physicists about on which end of the ice core to start measuring its length. The sea ice biologists who are most interested in the algae at the bottom of the sea ice like to set the zero mark to the bottom, whereas the sea ice physicists who are more interested in how deep the radar penetrates the ice like to set the zero to the top. Wherever you set the zero, most important is to remember where the top of the ice core is, once you got it out of the barrel.

Now it was my group’s turn to learn how to drill ice cores, the part I was most excited about. The core barrel has sharp teeth on the bottom used to cut into the ice and is rotated by a common drill attached to the top. A plate slightly bigger in diameter than the core barrel attached below the drill prevents the barrel from falling through the ice. We were warned to not loose any of the small parts in the snow and certainly not let them fall in the ice hole once the ice core is taken out. I volunteered to try ice coring first, so I assembled the drill, picked a spot on the ice and started drilling straight down. After the drill head caught on the ice, the trickiest part was to keep it from rotating yourself to the right. After a short time the drill head broke through the ice bottom and a mechanism clicked into place, preventing the ice from falling out of the core barrel. After dissembling the drill from the barrel again, I let the ice core slide out through the top of the core barrel. It was 40 cm long and had a break at 25 cm (I put zero at the top as a physicist), apparently not uncommon to occur in ice coring. The most interesting properties of the sea ice from a physics perspective are its temperature and salinity. We probed the temperature at 5 cm intervals by drilling a small hole halfway into the ice and observed how the temperature gradually increased from the bottom of the ice (which is at freezing temperature) to the top of the ice (which is close to air temperature). In our case the water was very fresh (can be easily tested by tasting the ice) due to a nearby river outlet and the strong melt of the last week’s warm temperatures, so that the freezing point was close to 0°C (for salty sea water the freezing temperature is at around -2°C). The air temperature was only slightly lower, so the temperature gradient was not that strong. For analyzing salinity, the ice core is cut into 10 cm long pieces with a saw and later melted and measured in the laboratory, which we did not do.

Too soon it was time to pack up and get back to the shore. I took one of the ice cores with me though and it is now lying in my freezer as a trophy. I have enjoyed the sea ice sampling field day a lot and learned a great deal about snow and sea ice properties, how to measure them and why they are of interest. Yesterday’s experience has strengthened my wish to do research in the field of sea ice physics in the future. Having the balance between doing theoretical or modeling work from home and being out in the field, drilling ice cores and looking at snow, sounds like a dream working environment to me. The Arctic sea ice is changing fast and its fate will have consequences for our entire planet. I want to contribute to understanding how the sea ice is changing and communicate why we are dependent on this strange and beautiful environment in the Arctic.


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