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 CHAPTER XII 



NAVIGATING IN POLAR REGIONS 



The art of piloting and navigating in the polar regions has gen- 

 erally been considered to present numerous difficult problems. Ac- 

 tually, apart from the special hazards offered by growlers and bergs 

 during periods of low visibility and fog, the basic problems remain 

 essentially the same as those encountered when operating over ex- 

 tended periods in lower latitudes, 



SIGNS OF PROXIMITY OF ICE 



When passing through open water where no ice is visible, it is 

 sometimes possible to detect the presence of ice in the neighborhood 

 by certain signs, as follows : 



1. The receipt of a return signal (pip or echo) by a vessel employ- 

 ing radar or sonar will usually give positive indication of the prox- 

 imity of large icebergs. 



2. Iceblink, the reflection of ice on the lower clouds, is the indi- 

 cation that has been most used by experienced pilots. As mentioned 

 previously, the albedo of sea ice or a snow surface is much higher 

 than that of a water surface. Much more sunlight is therefore re- 

 flected upwards from snow or ice and diffused by haze, dust, or water 

 particles in the lower atmosphere. Iceblink thus appears as a diffuse 

 white patch, more or less bright, on visible clouds, or as brilliant 

 scintillating strips on the horizon. There is no iceblink on a sunny 

 day with a clear blue sky. Slight snow flurries cause a more definite 

 iceblink. 



3. The appearance of isolated fragments of ice often points to the 

 proximity of larger quantities of ice, 



4. In late spring and summer, fog often indicates the edge of the 

 ice. 



5. In fog, white patches indicate the presence of ice at a short 



distance. 



6. Icebergs cracking, or pieces falling into the sea. make a noise 

 like breakers or distant gunfire. However, the sound is faint and 

 one must usually be quite close to the berg to hear it. 



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