13 
Bathysonde, This work was necessary for the inter- 
pretation of the measurements during the permanent 
stations. 
2. Results 
In the area of consideration the hydrography is 
distinguished by three characteristic water masses: 
i) The cold (<1°C) homogeneous water on the 
Icelandic shelf; 
The warm (>8°C) North Atlantic water off- 
shore; 
The cool (0° to 4°C) Overflow-water in the 
depth over the Iceland-Faeroe,-Ridge, 
ii) 
iii) 
The warm North Atlantic water is almost completely 
mixed. This applies particularly to the areas over 
great water depths, where the thickness of the near- 
ly homogeneous upper layer is 400 - 600 m (Figs 9-10). 
Over the Ridge, however, a relatively large vertical 
temperature gradient is existing, owing to the super- 
position of the warm North Atlantic water in the up- 
per layer and the cool Overflow-water in the lower 
layer, The depth of this gradient decreases north- 
ward, 
The boundaries of the three water masses form frontal 
zones belonging to the polar front system, The ob- 
served variability during the two permanent stations 
is essentially determined by the periodic displace- 
ments of these boundaries, Especially at the shelf 
station the irregular fluctuations of temperature 
and salinity indicate relatively strong turbulence at 
the front (Figs 14, 15, 18, 19). - For figs 15 and 19 
the Bathysonde registrations had been interpolated 
to the same levels of depth, and the mean values and 
the standard deviations have been calculated from up 
to 12 consecutive measurements,