antarctic oceanography 281 



Ice, Especially Shelf Ice 



Antarctic glaciation need not be discussed in detail in this oceano- 

 graphical paper. It is known that the masses of ice drifting in the sea 

 consist of icebergs and ice floes, the former representing land ice, the 

 latter sea ice. Of importance oceanographically is the fact that the 

 floes through freezing attain a thickness of only 2 or 3 meters and that 

 their further growth is dependent on the fall of snow and its turning 

 into ice. Therefore the floes for the most part have an origin Hke 

 that of the land ice and are thus free from salt; they differ from the 

 land ice, however, in their lack of all those structural forms which the 

 flowing movement brings about in the land ice.^° In the sea the 

 movement of the floes as well as of the icebergs is of course passive; 

 the floes are moved by the purely surface drifts, and icebergs, which 

 project much farther downwards, by the permanent currents, i. e. 

 essentially by the current of polar water. The outer margin of the drift 

 ice is described by most observers as being compact and as being frayed 

 out only by the winds blowing at a given time. I have already men- 

 tioned that the unbroken front of this edge and the rapid compacting 

 of the drift ice behind the margin is caused by the dominant east 

 winds and the currents resulting therefrom which encircle the conti- 

 nent in a westerly direction, inasmuch as these currents are deflected 

 to the left by the earth's rotation, i. e. toward the coast. It thus fol- 

 lows that the belt of drift ice substantially follows the coast and that 

 from its position one may draw inferences as to the position of the coast 

 line behind it. 



Of great importance is the shelf ice, as that ice formation is called 

 which surrounds the coast in the shallow shelf seas and which has been 

 found by all expeditions wherever their advances lay. It is an inter- 

 mediate form between the inland ice and the drift ice, as, like the latter, 

 it floats but, like the former, stays in place or moves only very slowly 

 within its limits. The best-known occurrence of this type is in Ross 

 Sea, where it ends in that wall or barrier first described by James 

 Clark Ross, which gave to the ice behind it the designation "barrier 

 ice."^i It is comprehensible on historical grounds if in England all 

 similar formations in the Antarctic are being termed barrier ice;^^ 

 objectively, however, the term "shelf ice" is better because the shallow 

 shelf sea with its banks and shoals is the necessary foundation for 

 the origin and character of this ice formation. Both its origin and 



30 Erich von Drygalski: Das Eis der Antarktis und der subantarktischen Meere (Deutsche Sud- 

 polar-Expedition 1901-1903, herausg. von Erich von Drygalski, Vol. i, Part IV), Berlin and Leipzig, 

 1921, pp. 517 ff., 626 ff. 



31 Griffith Taylor: Physiography and Glacial Geology of East Antarctica, Geogr. Journ., Vol. 

 44, 1914. PP- 365-382, 452-467, 553-571; reference on p. 378. 



32 In their fundamental report "Glaciology" (British (Terra Nova) Antarctic Expedition, 1910- 

 1913), London, 1922, which is now the leading discussion in English of the topics with which it deals, 

 C. S. Wright and R. E. Priestley adopt the term "shelf ice" for the formation in question (see pp. 161- 

 169 and 205-222; on terminology, pp. 162-163). — Edit. Note. 



