Nansen and Cram, having cultivated the sea collections of the Fram noted in addition to the 

 diatoms the presence of infusoria and ciliates which feed on plant forms. Bacteria were also found. 



Palibin, describing his observations on the Ermah in 1901, shows that the ice forms of dia- 

 toms found in the lower strata on the sea ice, completely support the opinion that the diatoms rise 

 from the sea water and freeze into the lower surface of the ice. According to Palibin and Nansen, 

 live diatoms are found only at a certain depth from the ice surface. However, Nansen considered 

 that the diatoms were suspended on the border between the fresh and salt water. Palibin supposes 

 that the most favorable medium for development of diatom forms is sea water of low salinity. 



The yellowish-brown accumulations of diatoms, which represent small clumps of a slimy 

 mass, absorb the solar heat and melt away a hollow underneath themselves the width of which is 

 usually two or three times greater than the width of the diatoms. There is no doubt that along with 

 the direct absorption of solar heat, the heating of the ice is caused also to a definite (although small) 

 degree by the carrying on of life processes in the accumulations of organisms, these processes 

 always being connected with output of a certain quantity of heat. 



Gradually sinking lower and lower during the course of the summer, through the holes which 

 they themselves are melting away, the diatoms are finally mixed with the sea water. 



It should be noted that after formation of the first water puddles on the large ice fields and 

 after the appearance of the first deposits of diatom slime, development continues during the entire 

 polar summer. 



The accumulation of diatoms on the ice sometimes reaches such proportions that the ice 

 appears dirty over a large expanse of area and appears perforated in all directions. 



During the ejqjedition of the Sadko in 1935 the greatest accumulations of diatoms in the north- 

 western part of Barents Sea were observed in the region beyond 80° north between Franz Joseph 

 Land and Spitzbergen. Estimating by eye, at least 20 per cent of the entire ice area was covered 

 with a reddish-brown deposit. Certain ice floes were so dirtied that one got the impression that 

 they were formed right by the shore. Between Franz Joseph Land and Sevemaya Zemlya the ice 

 was much whiter and cleaner. This was explained by the fact that in the first region clear weather 

 prevailed during our voyage, and in the second, cloudy weather. Clear weather, as we shall see 

 later in Section 115, creates the appearance of cleanness of the ice; cloudy weather gives the appear- 

 ance of dirtiness. In any case, in both regions the entire lower part of the ice, revealed when the 

 icebreaker turned the floes over, was brown in color and the podsovy (shoved-under floes) and rams 

 (under-ice projections) of certain of the ice chunks were dotted with accumulations of diatoms. 

 There is thus no doubt, as Palibin has expressed it, that the micro-organisms play a large role in 

 the summer destruction of polar ice. 



It is obvious that quantitative calculation of the influence of micro-organisms and inorganic 

 inclusions (dirtiness of the ice) on the hastening of melting is extremely difficult. Therefore the 

 observations of Shestipyorov, made in the spring of 1937 on Cape Schmidt in the Chuckchee Sea, are 

 of great interest. On 20 May areas of 1 square m of ice and 1 square m of snow were strewn with 

 cinders and coloring matter in a thin layer. This decreased the albedo (light reflecting factor) to 

 less than half and as a result the soiled ice by 8 July had melted 173 cm, the clean ice only 120 cm. 

 The soiled snow had melted 48 cm by 6 June while the clean snow melted only 19 cm. 



The hastening of melting of ice by dirtying its upper surface is employed in practice, in 

 particular for freeing of vessels which have passed the winter in the ice. For this purpose a path 



307 



