58 MARIOX EXPEDITIOX TO DAVIS STRAIT AXD BAFFIN" BAY 



changes in the intensity of the North Athmtic atmospheric circula- 

 tion, coming to the conchision that a weak circulation of air from 

 August to February is followed by a relatively small amount of 

 pack ice off Newfoundland during the succeeding spring. After a 

 strong circulation during the fall and early winter months more 

 pack than usual spreads over the Grand Bank. His studies are 

 especially important because they are based on a series of years, 

 running back to 1860. The scale is +2 for a year of much ice, and 

 -2 for little ice, a closer comparison i)robably being impossible <lue 

 to the nature of the material for the early years. 



Mecking (1906 and 1907) has published two important papers as 

 a result of a careful study of pack-ice conditions in the northwestern 

 North Atlantic, and an investigation into the possible causes of the 

 annual variations for the period of 1880 to 1900. His data are 

 obtained from the following sources: United States Army Signal 

 Service, United States Hydrographic Office, United States Weather 

 Bureau, and Deutsche Seewarte. 



The records of these offices consist of the reports of ice sighted by 

 trans-Atlantic ships on their regular voj'ages through the ice regions 

 off Newfoundland. The adoption of prescribed lane routes across 

 the Atlantic in 1875, their modification in 1898, and the present 

 method of seasonally shifting the tracks whenever ice conditions are 

 a serious menace, are all modifying factors wdiich must be given due 

 consideration in arriving at an accurate ice record over a period of 

 many years. The fact that many reports often refer to the same 

 field or floe may result in duplication and so caution is needed for a 

 correct compilation. Mecking has conclusively shown that the factor 

 chiefly controlling the variations in the limits of the spring pack ice 

 in the northwestern North Atlantic is the barometric gradient dur- 

 ing the previous winter across the ice stream in the vicinity of the 

 Labrador coastal shelf. The assumption is that favorable winds 

 and currents diu'ing the colder months of the year over Labrador 

 will drive more pack ice than normal past Newfoundland in the 

 following spring. Tlie agreement between the values of the ice 

 curves and the pressure gradients on his graphs is close. The spring 

 of 1887 was, however, an exception when a great quantity of pack 

 appeared off Newfoundland, although the pressure gradient had aver- 

 aged weak during the preceding winter. This inconsistency, Mecking 

 thinks, was due to the scarcity of icebergs which normally tend to 

 break up the pack ice, allowing it to drift freely. Also the year of 

 1889 was pecidiar in that practically no pack ice drifted south of 

 Newfoundland during the spring despite a favorable pressure gradi- 

 ent. Mecking attributes the inconsistency to the extremely warm 

 summer of 1888 which melted so much ice as to produce a deficiency 

 in the following spring. And in this respect this is the only case 

 recorded when the temperatiu'e in one summer was noticed in the 

 crop of pack ice the succeeding spring. 



Schott (1904, p. 305). with the aid of ship reports contained in 

 the files of the Deutsche Seewarte, reviewed the period 1880-1891, 

 comparing each year of the series with regard to quantity of pack 

 ice off Newfoundland. He agrees with Mecking that 1889 was an 

 unusual year, but he points out that the pack appeared in Septem- 

 ber, to remain for the balance of the vear. 



