Polarstern drift

Across the Arctic: What course will Polarstern follow?

Analysing potential drift routes on the basis of satellite and model data for logistics and research

In October 2019 the research icebreaker RV Polarstern will drop anchor at an ice floe in the northern Laptev Sea, which will mark the beginning of the MOSAiC experiment. The course that the ship will then follow can be estimated using satellite and model data. Information on the route that the RV Polarstern will follow throughout the next year is important for logistical planning, but also for coordinating research efforts. In the following, we present drift scenarios for various potential starting points.

Background

The potential starting point for the experiment with RV Polarstern lies in the northern Laptev Sea: somewhere near 85°N / 130°E the ship will begin looking for a suitable ice floe, one that is thick enough to serve as home for the year to come (see Figure 1). The Laptev Sea is a shelf sea, and is broadly considered the nursery of Arctic sea ice. The sea ice in the starting region at the beginning of the MOSAiC experiment was most likely formed nearby, or in the adjacent East Siberian Sea. In the course of the next twelve months, the Transpolar Drift, one of the two major currents in the Arctic Ocean, will carry Polarstern from the Siberian sector of the Arctic Ocean across the Central Arctic and into the Fram Strait.

Description of Methods

The ship’s potential drift route can be roughly estimated in advance by reconstructing the course that the ice followed from the starting point in past years. This involves the use of satellite data, which depicts the ice drift in the Arctic on a daily basis. The analytical tool used for the ice drift is called IceTrack and was developed at the AWI. In addition to various types of satellite data (ice drift, ice concentration, ice thickness), reanalysis data – which provides insights into temperature, wind speed and atmospheric pressure in the Arctic – is taken into account. In this way, not only the ice drift in the past years can be reconstructed for individual potential starting points, but all key atmospheric factors influencing the ice can also be included. A comprehensive description of these methods was recently released in connection with a study that investigated changes in the Transpolar Drift as a result of global warming (source: Nature).

The data portal displays drift scenarios for various potential starting points. Each figure shows the drift trajectories for the years 2005 – 2017 for the respective starting point (e.g. 85°N / 130°E). For the purposes of the drift analysis, the starting date is always 1 October of the respective year. The ice’s progress in the course of a year is reconstructed using the IceTrack algorithm, and the calculation is only stopped when the ice cover at the respective position drops below a certain threshold (50 %), at which point we have to assume that the MOSAiC ice floe would have melted. The colours used for the trajectories symbolise the month for the respective position.

Application to Logistical Planning and Research Coordination

In preparation for MOSAiC, the results of the drift analysis were used for strategic planning. The analysis can be used to estimate

• the location of RV Polarstern at time X,
• and what distances icebreakers, aeroplanes or helicopters would have to cover in order to reach the ship, e.g. for exchanging personnel and equipment, or for medical emergencies.

Criteria that are considered when selecting potential starting points for the expedition include:

• the likelihood that there is sufficient pack ice at the respective starting position at the beginning of the experiment (see Figure 3)
• the likelihood that the pack ice drifts into open water or the marginal ice zone and melts in the course of the experiment (see Figure 4)
• the likelihood that the ship drifts beyond the range of resupply icebreakers and aircraft,
• the likelihood that the ship drifts into the 200-nautical-mile zone of neighbouring coastal countries,
• the number of days that the ship will spend north of 88°N, an area where the availability of satellite data for the coordination of research and logistical activities is extremely limited (see Figure 5)

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Responsible for drift analysis and contact person at AWI: Dr Thomas Krumpen