Breaking the Ice

Research icebreaker RV Polarstern amidst snow-covered pack ice
Research icebreaker RV Polarstern amidst snow-covered pack ice (Picture: Command Polarstern)

Aspects of Practical Planning and Management of an Ice Passage

Captain Uwe Pahl
Uwe Pahl (Picture: Command Polarstern)

About the Author: Captain Uwe Pahl was the master of the German research icebreaker RV Polarstern from 1996 until 2014. Since 2014, he has been the team leader of the construction supervision team of Reederei F. Laeisz for the new Polarstern II. In this first article for Polar Prediction Matters, Uwe Pahl shares his personal view on how challenging it is to navigate such a large vessel through the polar seas.


The German icebreaking research and replenishment vessel RV Polarstern has been in service now for nearly 35 years in both the Arctic and Antarctic seas. During more than one-hundred cruises to the poles, scientists from many different countries have been participating in scientific expeditions, which all were carefully planned in preparation. In addition, the replenishment of the German Antarctic station Neumayer has been a regular main task for RV Polarstern during every austral summer season. Over the course of more than 18 years in command of RV Polarstern, I have experienced how challenging it is to navigate such a large vessel through the polar seas.

Each of the expedition voyage is carefully prepared in advance. In order to get an overview of the general seasonal ice situation, we – the ship’s command– consult current ice charts based on satellites such as the Cryosat 2/ESA-satellite (Fig. 2 and 3). As early as two to three months in advance of a cruise, such ice charts already indicate how the sea-ice situation might develop during the coming voyage. Ice-chart information is thus continuously collected for the strategic expedition planning.

An example of an ice chart used for planning in advance
An example of an ice chart used for planning in advance (Picture: Hochschule Wismar)

Once Polarstern has left the harbor, the ship’s command and the chief scientist are further planning the voyage track in three levels:

  • For the strategic planning of the voyage track all available sources are constantly used in order to find the most convenient passage through the ice with respect to the scientific programme of the expedition. Valuable sources include written reports on ice conditions as well as ice charts based on satellites such as ESA’s Cryosat 2 and JAXA’s Shizuku (AMSR2) processed and submitted to the vessel by the University of Bremen, and charts from the US National Oceanic and Atmospheric Administration (NOAA).
  • Regarding the long-range tactical ice and weather assessment, medium-scale radar ice charts are consulted. Weather permitting, helicopter flights up to one-hundred nautical miles from the ship are carried out to explore the current ice situation. The flights provide a good basis to the ships command to decide which track is to be followed.
  • Among the short-range tactical observations are high-resolution ice-radar charts obtained with instruments aboard the ship. These are complemented with helicopter reconnaissance flights around the vessel and direct observations from the ship’s crow’s nest. These information are used to guide immediate navigational decisions.
Ice chart
An ice chart as an example for various kinds of ice images which are used for planning a track through the ice. The clouds in the upper right corner, masking the ice situation underneath, exemplify the limits of such pictures. (Picture: NOAA/Command Polarstern)

Obviously, ice radar charts are of crucial importance for the planning and performance of voyages in ice-covered waters. A high-resolution picture transmission (HRPT) receiver installed aboard RV Polarstern allows to receive pictures with high spatial resolution of 1.1 km from different weather satellites such as the NOAA-, FENGYUN- and METOP-series up to twelve times a day. Also the ship’s radar and special ice radars are very effective tools for navigation, but require a constant training of the bridge personnel to ensure correct interpretation of the radar pictures.

Against the backdrop of the increasing shipping activities in the Antarctic as well as in the Arctic, in my experience the easy access to real-time ice images is, and will continuously be, of crucial importance for a safe navigation.

A new polar research vessel – RV Polarstern II – is presently under construction. Having operated a research icebreaker in perilous polar seas for many years, I am now contributing to the construction of this new ship, helping to ensure that all challenges of the years ahead are met.


Readers comments (6)

  1. Helge Goessling

    The article describes nicely how real-time information on the current state of the sea ice are playing a key role to plan the voyage through the ice – not just a few days but up to three months in advance! Is the conclusion valid that explicit sea-ice forecast products, for example obtained with a numerical model, have not been playing any role for the voyage planning and navigation of Polarstern? If so, are you aware of recent developments in this direction, or is this something you foresee for the future?

  2. Uwe Pahl

    Indeed, explicit forecast products have not been playing a major role in the past. However, I have recently been invited to the annual meeting of the International Ice Charting Working Group (IICWG) where I learned about exciting current activities aiming at improved ice forecasts. I am convinced that in the near future sea-ice forecast methods based on numerical models will play an important role for the navigation in ice-covered waters.
    [This comment has been posted by the YOPP Coordination Office on behalf of Uwe Pahl]

  3. Fabricio Tavares

    Congratulations on your job, Mr. Pahl. You wrote that Polarstern II is already under construction – is that exact? If so, which shipyard was chosen, and when will the new ship be ready? Thank you very much.

    1. Uwe Pahl

      After successfully operating our Polarstern since more than 35 years, the German Ministry of Education and Research planned to have a new vessel – Polarstern II – to be built. The Ministry is following the public procurement EU principles. So all interested shipyards had been invited to take part in the public tender. This process led to negotiations with a number of suitable shipyards. In the meantime the official German institutions using the expertise of our shipping company had developed a detailed construction description. At present we are awaiting the offers of the selected shipyards. After a careful examination of the offers, a contract will soon be signed with the successful candidate. So it is to be expected that the new vessel will be commissioned during the next years. In the meantime our good old Polarstern is fulfilling all scientific and logistical expedition tasks.
      [This comment has been posted by the YOPP Coordination Office on behalf of Uwe Pahl]

      1. Monique Caldwell

        Recent articles on the winning bidder’s design for the United States Coast Guard Polar security cutter indicate that it was based on the mature design for the Polarstern II but as of yet there do no seem to be any updates available elsewhere about the German program or if a builder has been selected. Is there any update that can be provided on the status of the selection process for the builder for the Polarstern II? Thank you for any information you can provide.

        1. Kirstin Werner

          Unfortunately, there are no updates available for Polarstern II. The tender procedure for a new German research icebreaker POLARSTERN II is still in process. The federal government cannot provide details of the ongoing proceedings due to public procurement law. Questions about construction time, commissioning and total costs depend on the award decision and therefore cannot be answered at this time.

Add comment

Related posts