How we’re keeping our footprint in the Arctic to a minimum
By Marcel Nicolaus
Our standards concerning the precision of our measurements and the overall scale of observations of the atmosphere, ice and ocean are naturally quite different from those 125 years ago, when Nansen first set out to study and explore the Arctic Ocean by drifting with the ice. Whereas, by today’s standards, Nansen ‘only’ made very general observations, we now rely on highly specialised instruments and platforms, which can only be effectively used with a fully equipped research icebreaker as their base, together with an extensive camp on the surface of the ice. The goal is to record time series that are as comprehensive and consistent as possible – on board Polarstern, on and in the sea ice, and in the ocean. In this regard, all measurements and projects also have to fulfil stringent criteria regarding the quality and completeness of the data. Making this a reality during MOSAiC requires careful planning and detailed coordination, as well as the occasional compromise.
When it comes to ‘classic’ Polarstern expeditions, individual research groups’ requirements can be taken into account fairly easily: the ship can be optimally positioned for current wind conditions, the ice is still pristine upon arrival, and the ocean currents at the time of measurement are known in advance. In contrast, during MOSAiC we will (for the most part, and hopefully) be firmly lodged in the ice, and our stations on the floe will operate for a year; accordingly, we have to plan for a number of additional aspects, and in some cases, have to employ wholly new concepts. The goal now is to adapt the camp’s layout to the local conditions. In the end, we will hopefully have the best-possible time series of the entire year, with very little influence from parallel measurements and activities, or from Polarstern herself. Though some individual data points will surely be affected by our own measurements, subsequent filtering and adjustment processes will help ensure that our findings reflect the conditions in the untouched Arctic as accurately as possible.
As is always the case for measurements taken from the ship, we also keep a close eye on the effects of Polarstern’s emissions on our readings. This happens e.g. when the wind blows emissions into our instruments’ intake ports. Consequently, we deploy them at locations that are very rarely affected by these emissions. Depending on the instrument, if the wind shifts to an undesired direction, the intake of air is either automatically interrupted to avoid the data’s being distorted; or the measurement cycle continues, and the data in question is subsequently marked and removed from the adjusted time series.
When it comes to the outlet for our filtered wastewater (technically clean water), a pump system was installed on Polarstern that reintroduces the salt previously removed from it, before discharging the water at a depth of ca. 150 m. The times at which these ‘dumps’ are made are documented, allowing any potential influences on them to be identified after the fact.
One unique aspect of the MOSAiC camp, compared to normal station-based work, is definitely the power network on the ice. It allows us to centrally and continually supply our devices and stations with electrical power, doing away with the need to use several smaller generators, which would produce additional emissions at various locations. This approach also makes it easier to filter data with regard to the wind direction.
The position of Met City, where the majority of meteorological measurements on the sea ice are made, is at the edge of the ice camp, so that the sector of air / wind that is unaffected by Polarstern and structures in the camp is as large as possible. In the initial design, the measurements were undisturbed in a sector of more than 270 degrees, since all the main installations were situated in the same direction. Yet the latest shift in the ice conditions has reduced that area somewhat; and thanks to ice dynamics, it will constantly change. Nevertheless, for the purposes of data processing, we have a clearly defined sector to work with.
Our ‘dark site’ is a station ca. 1.5 km north of the main camp, which lies beyond the large pack-ice hummocks and is largely unaffected by any artificial light. Here we exclusively work using infrared, so as to minimise our light pollution and influence on the development of the ecosystem within and below the ice as little as possible. The majority of ice cores are collected at the dark site, while a handful of autonomous devices record additional environmental data. It’s also where we take snow samples, as far from Polarstern as possible.
In terms of traveling on the ice, we have established a ‘walking culture’. Needless to say, we can’t entirely avoid using snowmobiles, especially when it comes to setting up large and heavy structures on the ice. Nevertheless, now most trips are made on foot or using skis. Especially skis have become quite popular, and lend our work a very rustic character when we ‘hike’ across the (in some places, heavily deformed) ice, towing a Nansen sledge behind us.
Last but not least, there is the logistics and recreation zone right beside the ship. Since we don’t have to worry about potentially influencing measurements here, the zone can also be used to gather readings for comparison. This data can then be used to put other findings in perspective. But here, too, we try to keep our footprint to a minimum. In addition, this zone is essential to maintaining a productive and harmonious environment on board, as it offers everyone a place to rest and relax, or to gaze at the starry sky or Northern Lights.