:VA) Dll MUKUAY ON THE DKEP AND SHALLOW-WATEE MARINE FAUNA 



A wedo-o of cold water thus stretches northwards from the Antarctic Circle for more 

 than twelve degrees of latitude, being overlaid and underlaid hy strata of a higher 

 temperature (see diagram). In the Antarctic Ocean the temperature of the water is 

 probably 28° or 29" F. (-2°-22 or-l°-67 C.) from the surface to the bottom, for the 

 temperature of the lower stratum decreases as colder latitudes are reached. One 

 remarkable fact brought out by these observations is that in latitude 50° S. the bottom 

 water has a temperature of 33°"5 F. (0°"83 C), which is very little different from the 

 temperature found all over the bottom in the Indian and other Oceans. The tendency 

 in a polar ocean, isolated from general oceanic circulation, is to produce a uniform 

 temperature of about 28° or 29° F., and this is the temperature actually observed in the 

 Norwegian Sea, north of the Wyville-Thomson Ridge, on which the depth iii 250 

 fathoms (457 ni.). There is no evidence at the present time of a similar condition of 

 thino-s in the Antarctic or Great Soutliern Ocean. 



Salinity and Density of the Sea. — Mr Buchanan's observations on tiie density of 

 sea-water, and his experiments on the formation of sea-water ice, throw much light on the 

 causes of the remarkable distribution of temperature noted al)ove. All the observations 

 made on water from the bottom or intermediate depths in the Southern Ocean, with the 

 density of the surface-water at each Station, are brought together in the following table.' 



Dejith I'lora which 

 Water was taken. 



Surface, . 



50 fathoms, 



100 ,, 



200 „ 



300 ,, 



400 ,, 



Hottoiii, . 



Depth of 

 (fathoms), 



bottom 



Salinity of Water expressed as Density at S^^t.^ j (g V"'c~^) 



SgS 



™ ^ to 



1-02512 



1-02561 



1260 



•^ ^s to 



1-02413 



1 •0-25Q7 



1675 



) ^ en 





U^ 



^ ^ 



"^ In CO 



rt ^ to 



S ^ tc 



1-02458 

 534 



(UOfatlis.) 

 1-02547 



55S 

 562 

 5-29 



1800 



1-02508 1-02509 



507 



561 ' 537 



565 ' ... 



665 



555 

 515 



1975 



I 



561 





■2-S "" 



1 -02522 

 522 

 544 



548 



(3]5faths.) 

 1 -02546 



554 



1950 I 



1800 





1 -0256 



1 



1-02564 



2150 





~ -" to 

 Jo 



1-02570 

 576 

 565 

 573 

 560 

 557 

 570 



2600 



it will be oljserved that the salinities in the tirst (column in lat. o6 48' S. are hio-her 

 tliaii in any other column ; the water from surface to bottom bears evidence of having 

 Ijcen warmed and concentrated in tropical or sub-tropical regions, the position being 

 where the warm water of the Indian Ocean is carried southwards of the Cape of Good 

 Hope. The salinities of all the other columns are from stations witliin the zone of 



' See ChalleiiLrer l^eport, Suiniuary of Results, First Part, jxi.wtw. 



