general call (CQ) was not broadcast by the reporting ship. These 

 broadcasts are supplemented by special messages to individual 

 ships, answering requests for specific information, or warning them 

 if they are known to be standing into danger. 



The ice hazard in the western North Atlantic is seasonal and 

 the degree of activity of the International Ice Patrol varies through 

 the season. The usual sequence of changes in this activity is begun 

 early in February with the opening of the ice patrol office at 

 Argentia and the commencement of aerial ice reconnaissance. Both 

 of these activities then continue until the end of the ice season. 



When ice is present in sufficient quantity, or during an unusual 

 year in the absence of ice when the advancing season would lead 

 mariners to expect ice and make radio inquiries regarding ice con- 

 ditions, the series of twice-daily NIDK ice bulletin broadcasts is 

 initiated. Once this series of broadcasts is started, usually in March, 

 it continues until the end of the season. When the ice situation war- 

 rants, usually as determined by aerial reconnaissance, a contin- 

 uous surface-vessel patrol is inaugurated and its inauguration is 

 formally announced. As every mariner familiar with the western 

 North Atlantic knows, visibility deteriorates with the advancing 

 season, and during a light ice year or one when the ice is late in 

 arriving and under conditions when continued poor visibility pre- 

 vents the ice patrol office from following the ice situation with 

 sufficient continuity by means of aerial reconnaissance, surface 

 craft are employed for ice observation. A distinction is made be- 

 tween ice observation and ice patrol, the latter being a continuous 

 surface-vessel patrol, whereas the surface vessel ice observation 

 cruises may be intermittant or continuous as required to supple- 

 ment aerial reconnaissance in determining when a continuous 

 patrol may become necessary. Qualified ice observers from the ice 

 patrol office participate in the aerial reconnaissance flights and 

 accompany the cutters on ice-observation cruises and ice patrol. 

 When the first cutter arrives in the area, a request is made for all 

 ships crossing the area to report to NIDK every 4 hours when 

 between latitudes 39° N., and 49° N., and between 43° W., and 54° 

 W., their position, course, speed, water and air temperatures, visi- 

 bility, wind and sea conditions, and any ice sighted. These four- 

 hourly reports are collected by the cutters until the end of the season. 

 They form the basis of ship plots and surface isothermal plots and 

 materially assist in ascertaining the movement and disintegration 

 of ice. 



The chronology of the 1947 ice season, conditioned by the meteor- 

 ological factors (discussed in greater detail in another section of 

 this report) which resulted in a nearly total absence of ice during 

 the first part of the season and a subnormal number of bergs for 

 the whole season, was as follows : Aerial reconnaissance was begun 



