103 



into this jiri>a would also havo been warmed to a coiTcsiiondiuLdy 

 hiaher degree tlirouah mixture witli it. As we remarked in dis- 

 cussing the observations of 1923,''' it is necessary to ai)])]v diller- 

 ent standards of temperature criteria in the autumn than in the 

 s])rini:\ for the former }ieriod inherits the heat absorbed from 

 an entire sunnner's sun. Avhile the latter is just emeririnir fi'om 

 a winter's chillino-, and. just as true, it is necessary to api)ly modi- 

 fied temperature criteria in a spring' follouing a winter char- 

 acterized by relatively hi<rh temperatiires and a mai'ked absence of 

 ice. 



Another method of identification of arctic water around the lail 

 of the Grand Bank at this period is to compare the temperature of 

 I he water mass which is questionable with tlie normal winter mini- 

 mum temperatures of the surface layers lyino- over the central parr 

 of the (xrand Bank, a region which most nearly approaches that of 

 a tidal reservoir and is most free, of all localities, from exteinal 

 intrusions. The aA'erage normal winter minimum for the central 

 Bank region is 0° to —0.5°;^" but at the end of the 1923-24 winter 

 it was 2.8°. Thei'efore, wherever we encountered water around tlie 

 Tail of the Bank during 1921- whose temperature was below- 2.35*^ we 

 inferred that sucli water was not cooled locally, but necessarily 

 must have been transported to that place from r. northern source 



The fact that the -water at the Tail, identified as Arctic in origin. 

 was less pronounced in temperatui'e character and of less voiume 

 than the liody of northei-n water bathing the slope to the northwest- 

 ward, it being restricted to a relatively shallow surface layer only 

 100 meters (55 fathoms) in thickness at the Tail, led to the conclu-i<»n 

 that the rate of flow of the icy current around the Tail had shrunk 

 from its size attained some time prior to March 23, the date of tlie 

 investigation. This conclusion is based upon the assumption that 

 the trunk of the cold current flows clockwise around the Atlantic 

 faces of the Orand Bank and not across it.-° -' The tendency of 

 arctic water to pool along the southwest slope, or become pinched ott 

 from the main supply, has often been noted.-- 



SUMMARY 



A })ool of u.nmistakal)le Aivtic water lay on the -outhwesr sloju' of 

 the Grand Banlc 40 miles west of the Tail on March 22-23. It cx- 



'* Smitb, Edward H. : Intcruntional loo Observjition ami Ice Patrol Servico. \'. S. 

 C. O. Bull. No. 11. p. IfiO. 



^" Sniitb. Edward H. : Ini'-niatiniial !<•<■ ( »l)scr\ aliou and Ic<< I'atrol Servio<'. C S. 

 ('. (i. Bull. Xo. 11, 192S, p. 14S. 



-" Sm'th, Edward H. : Internal innal Ic Oliscrvaiion ami Ic ■ I'alro) Service, r. S. 

 C. G. Bull. No. 10. 1922. p. Ss. 



=^ Smith. Edward H. : Internatinnal l-'i' Ohseivatiim .iml I<-e I'atrol Service. 1'. S. 

 C. C4. Bun. No. 11, 192.3, p. 114. 



-= Smith. Edward IT.: Interii.itioiial liv Ohs-rval ion and lee Patrol Service. }'. •<. 

 C. C. Bull. Xo. 11. 102.S. u. 1-i.-.. 



