Navigating through ice is a challenge not easely undertaken. It requires years of training and experience. However it continues to be proven so that it is in fact possible to make your way successfully thrue ice filled waters. There are a couple of basic principles to always keep in mind: adjust speed but always keep moving, know how your ship reacts to each command and try to move with the ice.
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Icing of Superstructure
The accumulation of ice on the superstructure is a very dangerous phenomenon that happens when several criteria are met. Slight icing will occur at winds of 5 Bft; moderate icing at 7 Bft: severe icing at 8 Bft. All when the temperature is below -2,2 °C. When sailing in fresh water, icing will occur much faster, namely from 0 °C and below.
The more common causes of ice formation on the superstructure are from spray by wave crests and ship-generated spray. Other possibilities are snow fall, sea fog, a drastic fall in ambient temperature and also freezing raindrops in contact with the cold steel. The heading of the vessel relative to the wind and seas will determine where the icing will grab hold. If the vessel takes these conditions head on, then a lot of the accumulation will occur at the forecastle and on all the mooring equipment which is stationed there. This causes a problem for the gispy wheel and the hawse pipe. The anchor will get stuck by the ice. Therefore, it is recommended that the anchors are slightly lowered in the hawse pipe in order to free them from ice accretion when needed. Another good practise is to maintain securing claws in place in case of slippery brakes. When the vessel takes the conditions from abeam, the ice will accumulate faster on the windward side which will result in an extremely dangerous list.
Ice Detection By Radar
When trying to detect ice, a Radar (Radio Detection and Ranging) is a very useful tool if correctly interpreted. The returning signal which bounces of ice (even icebergs) is very faint, much lower than from ship targets. Conventional marine radars are designed for target detection and avoidance. Enhanced marine radars provide a higher definition image of the ice that the vessel is transmitting and will result in a much clearer image. This image can be used to identify the quantity and sort of ice that has to be dealt with. In Standard radar, sea clutter affects the ability to see in the near vicinity of the vessel. Therefore, it is recommended to use a X-band radar and set to a short pulse. Also adjust the sea clutter knob to achieve the optimal setting for a clear image. The most hazardous form of ice are the growlers. They have a very low freeboard and are nearly undetectable (by radar and look-out). Therefore, it is advisable to keep a close eye on the tuning of the radar for optimale efficiency. In slightly rough conditions, the best way to detect growlers is visually. The surface of the sea will be rough but right above the growlers it will be flat.