23 
relatively warm and richly saline watermass from a 
very cold core of Polar water (Station 637). Similar 
to the hydrographic situation North of the sill, 
the thermohaline conditions South of the sill repre- 
sent a very narrow frontal zone which is situated 
above the East Greenland continental slope (Fig, 1 12). 
Figures 113a and b, show. the vertical distribution 
of temperature and salinity in the northern Irminger 
Sea. The gap between Stations No, 657 and 661 is due 
to the temporal difference which occurred during the 
observation. Whereas, the major part of the section 
is dominated by the Atlantic watermass, the influ- 
ance of Polar water is restricted to the westernmost 
stations of the section (Stations 650 to 653). 
The PCM profiles; 
The influence of the ship's drift upon the current 
profiles measured with the profiler were estimated 
from the LORAN-A navigator readings. Figures 114 to 
116 show the profiles of current velocity (0), 
current direction (X) and temperature (O0); they be- 
gin 200 m above the sea bottom, The PCM stations are 
situated upon the hydrographic sections which cross 
the Denmark Strait North and South of the sill (Sta- 
tions 634, 635, 6h1,resp.). North of the sill, large 
gradients in the current profile and the temperature 
profile were observed: in particular, they indicate 
the transition zones between Atlantic water and Polar 
water. In contrast to the observations made North of 
the sill, the measurements at Station 641 yield no 
larger profile gradients, neither in temperature nor 
in current.