SECT. 4] GEOGRAPHIC VARIATIONS IN PRODUCTIVITY 365 



Faeroes and south of Iceland. One of the factors contributing to the low 

 production of the Polar Current is presumed to be the low salinity of the surface 

 waters, which, combined with weak thermal stability, effectively prevents inter- 

 mixing of the euphotic layer with nutrient-rich deep water (Steemann Nielsen, 

 1958). In the Irminger Sea, south of Greenland, and in the Labrador Sea to the 

 west, winter cooling may produce vertical convection currents extending from 

 the surface to the bottom (Sverdrup et al., 1946). Such intensive mixing must 

 enrich the surface waters with high concentrations of nutrients. Similar loca- 

 tions exist north of Iceland and southwest of Spitzbergen. The productivity of 

 these areas has not been investigated but high spring and summer rates could 

 be expected. 



Investigations in the northern Norwegian Sea in June (Berge, 1958) disclosed 

 an area of high productivity in the central part of the sea south of Spitzbergen 

 extending in a north-south direction for some 500 miles. This zone of high 

 production is clearly identifiable with the tongue of warm, highly saline North 

 Atlantic water which intrudes into the Norwegian Sea. The rate of production 

 within the North Atlantic water was as high as 2.4 g carbon/m 2 /day as com- 

 pared with values of 0.40-0.60 in the fresher Arctic waters to the west and east. 

 The associated hydrographic features of the area were not discussed. 



D. The Arctic 



Quantitative phytoplankton investigations at Scorsby Sound, East Green- 

 land (Digby, 1953), and at Allen Bay, Cornwallis Island, North West Territories, 

 in 1956 by S. Apollonio (unpublished manuscript) suggest that primary 

 production at these latitudes (70°-75°N) may attain relatively high levels 

 during the brief period of open water. Although no productivity measurements 

 were made, chlorophyll concentrations averaged more than 1.0 (xg/1. and were 

 found in excess of 5.0 (j.g/1. at Allen Bay, values comparable to those observed 

 during the spring flowering of temperate coastal waters. 



In the Polar Basin itself, however, phytoplankton production appears to be 

 extremely low. Biological studies of this region were initiated with the Nor- 

 wegian North Polar Expedition, 1883-1896 (Gran, 1904), and were continued 

 by Soviet scientists beginning in 1937 at the drifting ice-floe station, "North 

 Pole I" (Shirshov, 1944). All indications pointed to low or negligible plant 

 production under the permanent ice pack. This was substantiated by sub- 

 sequent investigations, including a few 14 C productivity measurements, during 

 the International Geophysical Year 1957-1958, at the U.S. drifting stations 

 "Alpha" (T. S. English, unpublished manuscript) and "Bravo" (Apollonio, 

 1959). 



According to these authors, the floes of the permanent ice pack average 2-4 m 

 thick and are covered with wind-packed snow for ten months of the year. 

 During July and August the snow gradually melts and ponds of melt-water 

 appear over 25-35% of the area. Open leads also develop at this time, but 

 probably never represent more than about 1% of the ice field. Plant growth 



