ABSTRACT 



The authority for, mission, forces assigned and method of op- 

 eration of the International Ice Patrol during the 1958 ice season 

 are described. 



Aerial ice observation and communications statistics are 

 presented. 



All ice reports made to the International Ice Patrol in 1958 are 

 tabulated. A general month-by-month description of ice conditions 

 and sea surface temperatures in the Grand Banks of Newfound- 

 land area are given. A summary of ice conditions in the Gulf of 

 St. Lawrence and Strait of Belle Isle is included, as is a summary 

 of the post-war opening dates of these seaways. 



The most outstanding feature of the 1958 ice season was that 

 only one iceberg drifted south of the 48th parallel, thus con- 

 stituting one of the lightest ice years in the history of the 

 International Ice Patrol. This berg was reported on 18 July 1958 

 in 46°48'N, 47°46'W. The duration and maximum extension of 

 the pack ice in the Labrador and Newfoundland areas were 

 extremely subnormal. 



The three dynamic topographic charts resulting from the sea- 

 son's current surveys and the dynamic topography found at the 

 Bonavista triangle during the postseason cruise are discussed with 

 respect to surface circulation. 



The abnormal amount of onshore winds along the Labrador 

 coast during the first 3 months of 1958 resulted in an alteration 

 of the usual thermo-haline structure of the Labrador Current; 

 the minimum observed temperature was about a degree warmer 

 than usual, but extended to abnormal depth; the warm water 

 found was not as warm as usual, but was of abnormal geographic 

 extent ; and the salinities at intermediate depths were fresher than 

 usual. 



Temperature-salinity relationships of the Labrador Current 

 water, Atlantic Current water and mixed water found in the 

 Grand Banks region during 1958, are compared with mean T-S 

 curves for the 11-year period 1948-58. Lighter than average 

 water was found in 1958 at each level of each water mass. 



Labrador Current departures from average temperature and 

 salinity are noted, as well as their approximate contributions to 

 the departures from average density. 



