354 Alf Trolle. 



region of the coastal water (Sect. II, PI. XVII) and in the Store Belt 

 at a depth of 250— .300 m. 



Towards the east, out over the Greenland Sea basin, the 0° iso- 

 therm and 34.80 p. m. isohaline rise very abruptly on account of the 

 cold and salt water, found in the central part of that Sea, where the 

 hydrographical conditions are known from Roald Amundsen's in- 

 vestigations in 1901 and where, according to Fr. Nansen, the cold 

 bottom-water of the Norwegian Sea is formed (see Fr. Nansen: Nor- 

 thern Waters. Christiania 1906). 



Immediately to the east of the edge there is a layer of warmed- 

 up surface water with a depth of ca. 25 m. and temperature of over 

 + 1°. This relatively considerable amount of heat is due to the warmth 

 of the atmosphere and the fact, that the summer heat has been able 

 to penetrate so far down shows, that the waters here must have been 

 comparatively free of ice in the period dealt with. 



As soon as we came further west, inside the edge of the Conti- 

 nental Shelf, this warm surface layer disappeared and we only found 

 quite local, heated patches of a depth down to some few meters. We 

 may conclude from this, that in over the Continental Shelf, we 

 may expect to meet with continuous masses of drift-ice, which 

 cover the greater part of the surface and thus prevent the summer 

 heat from penetrating downwards, whilst further east out over the 

 basin of the Greenland Sea the drift-ice will generally be found to be 

 much more scattered. 



The — 1^ isotherm forms a closed curve, the point extending 

 out over the edge of the Continental Shelf and the uppermost arm 

 approaching the surface in the western part of the section, whilst 

 its lower arm here lies deeper down. Thus, the water seems to be 

 most cooled in the western part of the Polar Current, and this seems 

 to be a constant feature in the hydrography of this Sea. It is men- 

 tioned by F. Åkerblom: Recherches océanographiques, p. 15, and 

 it can be seen to have been the case in 1905 on PI. LXXI of the cited 

 work of Helland-Hansen in Due d'Orléans: Croisière Océanographique. 



It may be explained from the fact, that the south-going Polar 

 Current along the Greenland coast forms the main outlet for the sur- 

 face water of the North Polar Ocean. The western part of this 

 Current will consequently bring down water which comes from the 

 northern side of the Current in the North Polar Ocean and it is nat- 

 ural, that the cooling due to the atmosphere is here the greatest (cf. 

 also Fr. Nansen: The Oceanography of the North Polar Basin, p. 838). 



Remarks on the temperature, salinity and density diagrams for the stations 



in Section I. 

 Station III, 30/7 1906. Situation 74°45' N., 3°23' W. The dia- 

 grams for this station show the presence of a summer wave of heat 



