DAILY VARIATION— SEPTEMBER TO MARCH. 65 



of the snow accumulations on the sea ice during the voyage, but in Meinardus's account of 

 the Gauss observations there are a few important remaiics. We will therefore consider the 

 latter and then see how far similar considerations can be applied to the Fram conditions. 



. The Gauss was frozen in on February 22. As soon as the sea was completely frozen 

 over snow commenced to accumulate on the surface, and the depth of the snow increased 

 throughout the winter and first months of spring. 



The exact depth of the snow is not given, but we are told that the snow surface rose 

 about 60 cm. from .June to October (page 1.57 *). With the increasing intensity of solar 

 energy the surface however quickly underwent an important change, to quote Meinardus 

 (page 154). 



' The advent of warm weather and strengthened solar radiation produced a gradual 

 lowering of the snow surface on account of the molting together of the snow- 

 crystals, a process, however, which was often retarded through fresh snow accumula- 

 tions. Still the consequence of the progressive concentration of the snow was that 

 the old snow gauges which had been snowed up in the middle of October appeared 

 one after the other.' 



We see from these remarks an important change in the character of the snow-covering 

 to the sea ice. At the end of the winter and until the end of October there was an appre- 

 ciable depth of snow which on account of low temperatures and the absence of melting would 

 be in a comparatively loose condition, the surface only being compacted by the wind. Such 

 a snow layer would have a low conductivity which together with its depth would make it 

 an effective protection against a supply of heat from the underl3ang sea ice. The surface 

 during September and October would therefore approach the condition of the Barrier, with a 

 consequent large daily amplitude of temperature. 



After October the snow, as we are informed, became more compact and its thickness 

 decreased. This process probably continued at first rapidly and then more slowly until mid- 

 summer, when what little snow was left would oppose only a small impediment to the transfer 

 of heat from the sea ice to the air. Thus we should expect at the Gauss station the daily 

 amplitude of temperature to decrease, relatively to the amplitude of solar radiation, from 

 October to midsummer. An examination of figure 23 will show that this occurred : in spite of 

 increasing amplitude of radiation from October to December the temperature amplitude greatly 

 decreased and in December the point for the Gauss station is exactly in the middle between 

 the two dotted lines. After December the points for the Gauss station do not depart largely 

 from the linear relationship between temperature amplitude and solar radiation amplitude. 



Returning now to a consideration of the Fram observations, there is no reason to suppose 

 that the sea ice in the north would not also be covered by a blanket of dry loose snow 

 at the end of the winter. Also as the snowfall is known to be heavier in the north than 

 the south the depth of snow was probably greater around the Fram than around the Gauss. 

 It is interesting to notice that the two points for March and April for the Fram lie on the 

 line joining the point for the Barrier with the origin. This is what would be expected if the 

 surface were similar in the two legions and the temperature amplitude depended only on the 

 radiation amplitude. 



By midsummer in the north as in the south the snow-covering would have become a 

 very poor insulator and we find a rapid decrease in the temperature amplitude. The Fram 

 point for June is in the middle between the two dotted lines, showing therefore a normal 

 relationship between the temperature and insolation amplitudes. The only difficulty is the low 



* Meinardua. Deut. Sudjjolar-Exped. Meteorologie, Band I. 



