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Old Ice in the High North

Measurements under the ice Ocean Arctic

Where the Ice Floes Still Form Massive Hummocks. We’d come here because it was home to something that has become rare in the Arctic – old sea ice.

It was an unforgettable welcome: when we came in from the Arctic cold (-25°C) and first set foot in the entrance area of Canada’s CFS Alert station, the entire staff, decked out in their best uniforms, greeted us with an honour guard and warm round of applause. We had a long journey behind us: in the six days since departing from Bremen, our trip to Ellesmere Island had included roughly 25 hours in the air, six airports and an unexpected two-day layover in Resolute Bay due to a technical problem with the DC 3 we’d chartered. But after the outstanding reception we received at this remote outpost of civilisation – the northernmost station on the planet – we quickly forgot the long trek.

We’d come here because it was home to something that has become rare in the Arctic – old sea ice. The shoreline is characterised by metre-high, thick floes that are several years old, and have been around the block a time or two. The sea ice here differs from what we’re used to seeing on our expeditions in the Central Arctic. There are virtual “mountains” measuring more than ten metres tall; having partly melted during the previous summer, they now form an impressive landscape of round hills. Here, the major currents in the Arctic Ocean press large amounts of old ice against the northern Canadian island landscape. The result: a shear maze of ice floes that no icebreaker on the planet would have a chance of penetrating. It’s precisely this ice that we want to investigate, before it disappears one of these days. During the winters here it’s so cold that the pack ice freezes together firmly, allowing us to safely venture onto the surface from the shoreline.

Yet the old ice also has its fair share of drawbacks. Prior to our arrival, our Canadian partners had mapped a route on the ice. Though the optimal site for our fieldwork was only six kilometres from the coast, to get there we had to first endure a 45-minute snowmobile ride over bumpy terrain (see Image 5).  For the first few days of the expedition, we spent most of our time getting set up, e.g. transporting roughly one and a half tonnes of equipment onto the ice with the help of the snowmobile. Using a hot-water drilling system, a one and a half metre-diameter hole was melted in the ice for the purposes of our work; then a large heated tent – to keep the sensitive electronic equipment in our remotely operated underwater vehicle (ROV) warm (see Image 6) – was erected over the hole.

On this expedition, the ROV is our most important tool. From the vantage point of our hole in the ice, it allows us to explore the world below the thick multiyear ice floes, and below the first-year ice, which only formed this winter. Measuring one and a half metres thick and topped by twenty centimetres of accumulated snow, even this ice is fairly thick for its age; yet the nearby multiyear ice floes often reach thicknesses of three to six metres, and some of the pack ice hummocks right beside our tents (which are comparatively small by this region’s standards) are over fifteen metres thick (see Image 7). Using the ROV, we investigate how much light penetrates the ice under different conditions. One important factor in this regard is the snow cover. In order to better understand this relation, we also take regular measurements of the snow cover, accurate down to the nearest millimetre, with the aid of a laser scanner. The first impression isn’t misleading: here it’s extremely dark below the ice.  In fact, less than one percent of the sunlight at the surface penetrates to the underside of the ice. Even though, according to some textbooks, that’s far too little light for algal growth, our Canadian colleagues have observed substantial amounts of algae on the underside, which can even be recognised with the naked eye as a brown shimmer in the ice core samples.  In addition, our ROV is once again towing a five-metre-long zooplankton net behind it, which captures a wealth of fauna: small ice amphipods, copepods, jellyfish and even fish larvae. Interestingly, some species can only be found below the multiyear ice; moreover, there’s an amazing amount of life on the seafloor, 220 metres beneath the surface (see Image 8). 

During its sweeps, the ROV encounters sponges, cold-water corals, fish, mussels and two squid. Though the ROV is technically designed for operations directly below the ice, with just a few modifications we can also engage in forays deeper down; after all, we’re most likely the first human beings to observe the seafloor off the northern coast of Ellesmere Island, which is icebound all year round. When we’re not using the ROV, we work on more precisely characterising the snow on the sea ice. By measuring the temperature, thickness, strength, crystalline form and water content, we arrive at a more detailed portrait of the snow cover. What especially caught our eye this year: large and beautiful crystals measuring up to a centimetre in diameter. Radar readings allow us to analyse our findings, together with data gathered using a NASA research aircraft (Operation Ice Bridge), and to incorporate the outcomes in the development of algorithms for the broad-scale measurement of snow thickness on the basis of aircraft or satellite data. For nearly four weeks, we take all of these readings at regular intervals. In addition, there are several autonomous sensor buoys in our tent camp, which will continue transmitting data on the multiyear ice’s transparency, temperature and snow cover to us via satellite, long after we’ve departed (see Image 9). So far, the weather gods have been very kind, and we’ve been able to drive out on the ice every day. Thanks to the outstanding support of the station staff, and to our highly experienced logistics crew, we have the ideal working conditions and can even enjoy a hot lunch out on the ice. The wonderful cooking staff even treated us to fresh salad. Even though it was a true luxury, most of our team opted for the chocolate cookies instead, so as to replenish their energy reserves after working out in the cold. And, though the station commander had described the place as being extremely harsh during his welcoming speech, our impression was that human beings are the only species that needs an enormous amount of technological support to survive here. In any case, the fauna under the ice, and even the snow hares and wolves that we occasionally see on our daily rides out to the worksite, don’t seem to mind the cold.





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Stacked multiyear ice near CFS Alert, Canada.