47 

 C to Grand Banks=^TZ"=5.0% 



ymean 19.8% 



and 1949 to 1950 C to Grand Banks=Y2^=34.6% 



The over-all sm-vival rate would be their product or 2.1 percent (97.9 

 percent mortality) . On this basis it might be expected that the num- 

 ber of bergs appearing south of 48° N., would be 487 in 1951 and 713 

 in 1952. It is probable that these survival rates are not normal. 

 From a preceding table the volume of flow and heat transport of the 

 West Greenland Current past Cape Farewell was seen to have been 

 exceptionally small in 1948 and 1949, and exceptionally large in 1950. 

 Thus the censuses of 1948 and 1949 are not well adapted to the 

 determination of normal sm^vival rates although they might be ideal 

 in combination with other data in estimating the importance of the 

 effect of such factors as the heat transport of the West Greenland 

 Current on sm'vival rates. 



The survival rate for the part of the journey from area B to area C 

 is the largest of the thi^ee. However, it is suspected that this figm'e of 

 49.9 percent is too low. Areas B and C are located in the coldest part 

 of Baffin Bay and rouglily coincide with that region in which Smith ^ 

 has indicated that no melting takes place. 



The survival rates from A to B and that from C to the Grand Banks, 

 being small, indicate that the factors affecting the disintegration of 

 bergs in these two parts of the jom-ney are important. The large 

 difference in the sm-vival rate from C to the Grand Banks dm-ing the 

 year 1948-49 as compared with the year 1949-50 indicates that the 

 effective factors in this part of the jom-ney are not only important 

 but variable. The number of bergs calved in any year is of com-se a 

 basic starting point. As seen from the difference of about 10,000 

 between the adjusted count for 1948 and the photographic count for 

 1949, application of the survival rate of 2.1 percent would mean a 

 variation of some 210 bergs in the numbers reaching south of the 48th 

 parallel in two successive years if the conditions affecting the mortality 

 of these particular crops are the same. Thus an important factor in 

 any forecast of the number of bergs which will reach the Grand Banks 

 region is the departure from average of the number of bergs calved. 



The mortality during the part of the jom*ney from area A to area B 

 is seen to be large but since we have but one value for this sm-vival 

 rate nothing is known as to its variability and the importance, there- 

 fore, of departures from average conditions. Possibly this may be 

 affected by the changes in the rate at which water-borne heat is sup- 

 plied to Baffin Bay and may be deduced from the heat transport of 

 the West Greenland Current passing Cape Farewell the summer the 

 bergs are calved. 



' Smith, Edward H. "The Marion expedition to Davis Strait and Baffin Bay, Arctic Ice," U. S. Coast 

 Guard Bull. No. 19, pt. 3, fig. 121, p. 200 (1931), Washington. 



91 



