SCIENTIFIC EESULTS 



47 



The rate of wastage of pack ice in the Arctic during the summer is 

 well shown by the records of the Godthaab and the Marion expedi- 

 tions for the summer of 1928. On Jul}^ 3, the west ice of Baffin Bay 

 extended halfway across to the Greenland coast; on August 15 it 

 occupied only one-fourth of the strait; and on September 15 it had 

 withdrawn from the Baffin Land coast as far as Cape Broughton, a 

 promontory 90 miles north of Cape Dier. Again the average rate of 

 retreat of the southern bounds of the west ice in Baffin Bay during 

 the sunnner of 1928 w^as approximately 1 mile per day. Iii gcueral 

 the shrinkage of pack ice in the far north is a phenomenon which 

 accelerates to a certain period during the summer, after which it is 

 •.q-adually retarded, until freezing begins. 



The circulation of the waters of Baffin Bay and the movement of 

 the pack is known only in a general way. The first systematic ocean- 

 ographic survey of the bay w^as made by the Godthnah expedition 

 which took a large number of observations there in the suuuner o^ 

 1928.^^ These data were published in the Hydrographic Bulletin 

 (Annually, 1929), and I have used them to construct a map of the 

 l)revailing circulation as shown by Figures 91 and 92. pages 139-14U. 

 In addition to this dynamic topographic map of Baffin Bay, some 

 of the best available information is contained in the drifts of ships 

 caught by the ice in various parts of the bay. These follow : 



Ship 



North Star (Saunders) 



Advance (DeHaven) 



Enterprise and Investigator 



Kesolute (Kellett) 



Rescue (Griffin) 



Fox (McChntoclv) 



Polaris Party (Tyson) 



Greely's Boat (Greely) 



Distance 



Miles 



150 



900 



290 



1,020 



900 



1,194 



1,700 



65 



Drift from 



Latitude Longitude 



60 50 



93 00 



92 30 

 99 30 



93 00 

 62 16 

 72 00 

 72 00 



Drift to 



Latitude Longitude 



64 30 



67 00 



63 47 



55 00 



78 45 



71 05 



60 30 



73 00 

 ()2 30 

 60 30 

 56 36 

 52 00 



74 00 



Icebergs have been observed to drift northward along the east side 

 of Baffin Bay. On the other hand the Marion expedition mapped a 

 southerly current along its southwest side with a rate of 7 miles ])er 

 day, (See fig. 96, p. 148.) Thus it seems well established that a gen- 

 eral cyclonic circulation prevails, so that the w^estern (iciest) zone 

 evacuates through Davis Strait, while a compensating indraft follows 

 northward along the Greenland side.^^ 



What proportions of the pack that moves out through Davis 

 Strait into the North Atlantic originate in Baffin Bay itself is an 

 interesting question. Consideration of the above table and other 

 available data throws some light on this problem. The first of the 

 pack that emerges through Davis Strait, on the resumption of 



=^ Riis-Caitpnsen (1929) gives a preliminary account of the expedition, the published 

 reports of which have not yet appearecL , . , . 



^Mecking (190G, supplementary map) has drawn a southbound current and ice band par- 

 allel to the eastern shore of Baffin Bav, its axis closely coinciding with the 600-meter iso- 

 liath. Such a representation is based largely on the drift of the Fox in I808, and to a less 

 i ixtent on the behavior of the middle ice. this feature of the circulation is. however, n<;t 

 \ confirmed by the recent oceanographic observations of the Oodthaah expedition nor is 

 Mecking's southerly current supported by the general laws for dynamic gradient currents 

 iu the Xorthern Hemisphere. 



