Long Term Trends 

 in the Iceberg Threat 

 in the Northwest Atlantic 



Abstract 



Analysis of records on icebergs drifting past Newfoundland since 

 1880 reveals that the seasonal count of icebergs has fallen by 55% 

 in the last three decades. An analysis of available environmental 

 data for the same period shows that the decrease is associated with 

 a decrease in the strength of winter northwesterly winds off southern 

 Labrador and with an increase in winter air temperatures at Torbay, 

 Newfoundland. 



Introduction 



Each year in the spring icebergs drift south in the Labrador Current 

 along the Labrador coast. Many pass Newfoundland and are carried along 

 the eastern slopes of the Grand Banks where they become serious hazards 

 to ships (Figure 1). Smith (1931), drawing on his own observations and 

 the earlier work of Schott (1904), Mecking (1907), and others, gives an 

 excellent account of the origin, drift, distribution, and eventual disin- 

 tegration of icebergs. 



The number of icebergs which drift south of Newfoundland each year 

 is highly variable, ranging from one or two to over a thousand. Mecking 

 (1907) compiled a record of iceberg counts for the period 1880-1899. 

 Smith (1931) extended this compilation to 1929. Since 1929 the annual 

 Report of the International Ice Patrol Service in the North Atlantic has 

 contained iceberg statistics. This record stretching back in time for 

 90 years is of interest because it reflects meteorological, oceanographic, 

 and glaciological conditions since the 1880' s. However, its validity 

 should be tested by comparison with the record of another environmental 

 parameter which is related to the iceberg count to see if the iceberg 

 record appears consistent. 



Internal Consistency of the Iceberg Record 



Traditionally the intensity of the iceberg season is measured by 

 the number of icebergs drifting south of 48°N. This is because 48''N 

 represents the approximate northern boundary of trans-Atlantic shipping 

 routes passing south of Newfoundland. Although icebergs can be found 

 south of 48°N in all months of the year, an average of 93% are found 

 during March- July, and these months are considered the iceberg season. 



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