The rate of cooling is generally greater, the greater the temperature difference between 

 water and air. As we have seen, this difference is very small in the open sea and reaches its 

 greatest values near shore and ice massifs, when the winds are offshore or off the ice. Hence, the 

 highest rate of cooling should be expected near shore during offshore winds (the land cools faster 

 than the sea in the pre- winter period) and near the edge of the ice with a wind off the ice. 



By comparison, we find that, other conditions being equal, ice formation at sea begins 

 earliest in the high latitudes (large difference in the air and water temperatures) near the edge of 

 the ice, especially during an off-ice wind and amidst ice which had melted during the summer (high 

 salinity gradient and low water temperature), near shore (shallow water), and near river estuaries 

 (shallow water, high salinity gradient and a higher freezing point as compared with sea water). 



As observations have shown, the freezing dates in different regions of the Soviet Arctic vary 

 from year to year within extremely broad limits. As a rule, freezing begins first in the region 

 near the Lena in the New Siberian Straits (about the middle of October), in Vilkitskii Strait (in the 

 second ten days of October), and, after this, the wave of freezing spreads from these regions in 

 both directions to the east and west along the coasts . 



This picture of freezing is particularly characteristic during years with little ice. In years 

 with much ice, freezing which spreads from the ice aggregates that still remain at the end of 

 summer predominates, and at first, the freezing is centered in these aggregates. The floating 

 floes are fused very quickly by young ice, and turn into solid ice massifs which are almost impass- 

 able, even for vessels especially adapted for navigation through ice. This last factor has created 

 a rule among arctic men; vessels which have not departed from the ice prior to the start of freezing 

 risk remaining in the ice for the winter. 



The freezing of the Soviet Arctic seas was clarified in 1943 by very late reconnaissance 

 flights and proved to be quite unique. For example, on 26 October, the Laptev Sea was still com- 

 pletely free of ice between 75° 30' north and 120° east, and 77° north and 110° east. It should be 

 remembered that this same region was the first to be clear of ice in the spring of 1943. On 30 

 October, during reconnaissance along the 130th meridian up to 81° 30' north, no old ice was ob- 

 served and the entire sea was covered by solid Ice without any polynyas or hummocks, in spite of 

 quite strong winds. A strip of clear water, discovered by a reconnaissance flight on 25 October, 

 was covered with gray nilas. According to the aerial reconnaissance of 31 October, the entire 

 Kara Sea north of 72 ° north was covered by level young ice also without pol5myas or hummocks . 



LITERATURE: 62, 77, 73. 



Section 83. Ice Thickness as a Function of Air Temperature 



After the surface of the sea is covered by a continuous ice cover, further ice accretion from 

 below, during calm conditions, takes place exclusively due to heat conductivity through the ice and 

 the snow cover and can be computed to some extent. 



Weyprecht conducted the first systematic observations of sea-ice growth due to heat conduc- 

 tivity during a winter in Franz Joseph Land (1873-1874). From these observations, Weyprecht 

 gave the relationship between the number of freezing degree-days, i.e. , the sum of the mean daily 

 negative air temperatures, and the thickness in centimeters of the ice which had formed. 



204 



