The Three-dimensional Temperature Distribution and its Variation in Time 131 



Below about 300 m down to the greatest depths it is filled with a water mass at a 

 temperature between 21-5°C and 21-6°C. The deep water has its origin at the surface 

 in the northern half of this sea, where in March and April the v/ater temperature is 

 21-5°C combined with salinity values of 40-5-40-7%o increased by evaporation. The 

 currents present definitely exclude any influence from conditions outside the open 

 straits in the south. 



With this group can be included the temperature distribution in the deeper layers 

 in the Norwegian Sea (from 1000 to 3500 m approximately homo-thermal, —0-8 to 

 — 1-3°C and 34-9%o). Presumably this water mass must be formed at the surface to 

 the north of Jan Mayen. 



The second group of adjacent seas belongs exclusively to the warmer zones, where 

 the surface temperature during the whole year is so high that the temperature at the 

 sill depth is the determining factor for the thermal structure of the sea below the sill 

 depths. Only oceanic water has access in this case to the deeper layers below sill 

 depth. The sinking of oceanic water into the enclosed space produces a potential 

 temperature extending to the bottom, that is determined by the potential temperature 

 of the open ocean at the level of the sill. This phenomenon is in many cases so marked 

 that inversely the sill depth can often be deduced from the vertical temperature distri- 

 bution in the adjacent sea, 



A characteristic example of this second group is the quasi-homo-thermal structure 

 of the water masses in the Australian-Asiatic deep-sea basins beneath the depths of 

 the sills over which they are connected with the Pacific Ocean or with the neighbouring 

 basins. An accurate and detailed investigation of these conditions based on the ob- 

 servations made by the "Willebrod SneUius" Expedition has been made by Riel 

 (1934), Table 58. 



Table 58. Vertical distribution of temperature and salinity in the 

 Australian-Asiatic Basins {""Will. Snellius" Exp.) 



