Sailing in a straight line through the open sea is easy. Sailing in a straight line in meters-thick ice is not so straight forwards.
The officer steering an icebreaker have to find the best way through the ice. The best way depend on many factors, such as ice thickness, concentration and floe sizes. The quickest path is not necessarily in a straight line, but rather i.e. going from open water spot to open water spot. Sometimes there is a lot of ice pressure, meaning that the wind is pushing the ice floes together. The ice floes can be several kilometres across. The forces from this ice pressure can squeeze the vessel and actually make it stuck.
To avoid the thickest ice, tools such as satellite images and ice charts are used to plan the route through the ice. The first photo below show an ice concentration chart, displayed on a screen on the bridge of Oden. Purple colour indicate 100 % ice concentration, and blue is open water. The chart is made from satellite images, and the latest chart available on the vessel can sometimes be one or more days old. The wind and currents can move the ice a lot in short time, so the charts are never 100 % reliable for operational use. However, they can give a good indication about which areas have more and less ice. You can tell that towards Canada and Greenland (bottom of the photo) there are almost 100 % ice cover, while towards Alaska (left), Russia (top/right) and Svalbard (right) ice conditions are less severe. This is typical, and happens because of the circulation of the Arctic Ocean.
However, on this trip, we were not free to always choose the best way through the ice. Due to seismic surveys, we were supposed to sail in straight lines in order to get the best results. The second figure below is a screenshot from an onboard mapping software. The red and purple lines are the planned track; the yellow lines are the actual lines we sailed. This gives an idea about how much zig zagging we have to do to while trying to do a straight line in ice. When it is not possible to go straight forwards, the officer will back up the ship and either gain more speed and try to “ram” the ice again, or choose another route with higher likelihood of softer or thinner ice and getting through.
The second figure also show tracks from seabed mapping. The red colour indicate shallower waters, and green indicate greater depth. The blue seabed in the background represent the current bathymetric map, which many places are actually just rough approximations and guesstimates (guessing and estimating based on some knowledge). Did you know that the surface of the moon is better mapped than the bottom of the worlds oceans? Furthermore, the Arctic Ocean is one of the less mapped oceans in the world. Therefore, mapping data of the seabed here is very valuable. The lines on this map are from previous expeditions, but we have been collecting mapping data with both ships during the whole expedition.
1: Ice concentration map (taken Monday 29 Aug). The vessel position and heading is indicated by the black square with a line in front, and our track is plotted in red.
2: Screenshot from one of the mapping software we use on Oden, showing planned track vs sailed track. The red triangle indicate the position of the vessel (actually here we were very close to the North Pole!)