no ANNAL8 NEW YORK ACADEMY OP SCIENCES 



Speaking of ice conditions we must make a distinction between ice- 

 bergs and sea ice, the conditions under which these two kinds of ice are 

 produced and drift being absolutely different. 



Icebergs are anchored deep in the water and are much less influenced 

 by the direction of the winds than by the ocean currents. They originate 

 at the glaciers. The quantity of icebergs carried down through Davis 

 Strait, for example, and along the Newfo'undland Banks, will depend 

 mostly on the factors which acted upon the flow of the glaciers. Sup- 

 posing normal conditions of the glaciers (for example, a regular advance)^ 

 a succession of cold years followed by a warm year and, in particular, an 

 abnormally warm summer, will favor considerably the production of 

 icebergs. 



In 1909, for example, much ice was noticed in tlie Atlantic. ^^ 



The consecutive temperature curves of Upernivik and Jacobshavn give 

 an explanation to this fact. During 1906 and 1907 we notice a remark- 

 able depression in the curves (Fig. 57), followed by a steep ascent, culmi- 

 nating, in 1908 and 1909, farther south, in Ivigtut. 



Tlie drift of polar sea ice, on the other hand, is a most complicated 

 phenomenon. In the Antarctic, the conditions are very much simpler 

 than in the Arctic, and, even there, the drift is far from being a simple 

 function of the velocity and direction of the wind. 



For the north polar basin, the distribution of the surrounding lands 

 and islands, and the existence of well-pronounced ocean currents, compli- 

 cate the ice-drift to such an extent that the possibilities of a successful 

 study of the correlations between the anomalies of the meteorological con- 

 ditions and the abnormal changes of tlie ice conditions is evidently most 

 problematical. 



The observations collected by the Danish ]\Ieteorological Institute and 

 printed every year concern the ice conditions during the navigable season 

 only and are naturally restricted to the peripheral areas of the frozen sea. 

 In some waters, we have to deal with winter ice, which must melt away 

 during the summer; in otlier waters it is old drifting polar ice which 

 hinders navigation. To correlate these variable ice conditions, of the 

 navigable season of some arctic seas, with atmospheric temperature data 

 of distant stations is a- task wliicli can lead onlv to verv uncertain results. 



*i In the special reprint of the Nautical-meteorological Annual of the Danish Meteoro- 

 logical Institute, "Isforholdcne i de arktiske Have, 1000," it is said : 



"Off New Fovindland and on the transatlantic steamer routes uncommonly much lee 

 was observed, floes as well as icebergs. As early as February there was much ice, antf 

 from March to July the conditions were more unfavorable, than they have been for 

 many years. The icebergs held out uncommonly late, the navigation being much ham- 

 pered at Cape Race as late as August. It was not till September that the ice com- 

 menced to decrease, but still many icebergs were to be met in Belle-Isle Strait and far 

 off-shore off the Strait." 



