still more striking are observations made by thePerseus on 5 September 1934 in Trauren- 

 berg Bay at 79° 58' north, 16° 48' east. See table 92. 



TABLE 92. WATER TEMPERATURES AT 79° 58' NORTH, 16° 48' EAST, 

 5 SEPTEMBER 1934 



This bay is isolated by underwater rapids from the waters of the Spitzbergen current which 

 flows into the region to the north of Spitzbergen. The high temperature of its water is created 

 locally as a result of absorption of solar radiation and heat from the air. 



1i we consider that the water temperature in this bay falls to the freezing point in winter, it 

 then appears that during the summer season 40 kg-cal were absorbed here by each square cm of 

 water surface. If we take into account the local conditions which make for little cloudiness and 

 great transparence of the atmosphere in the summer season, this seems entirely possible. 



On 19 August 1932 the Rusanov observed a surface temperature of 3.7° in the Shokalski 

 Straits, and 5.3° in the Vilkitski Straits. 



These examples show how considerable may be the warming of surface water in the ice 

 regions of high latitudes under conditions of absence of ice. They force us to refer with particular 

 care to the calculations concerning penetration of warm currents into the polar regions calculations 

 based only on observation of surface temperatures. The high temperatures of the surface water in 

 the majority of cases serves only to indicate an earlier clearing of ice from the sea. 



Just as we can distinguish in every region of the sea certain areas in which ice formation 

 begins earliest, we may also distinguish areas where the ice breaks up earliest and the sea is 

 cleared of ice. From these areas as centers, other conditions being equal, opening and melting 

 spreads out in a definite direction. The position of these centers of breakup and melting is deter- 

 mined by many physicogeographic factors. 



Other conditions being equal, breakup begins earliest in the more southerly regions, near 

 the shores, in regions of strong tidal currents, and particularly near the mouths of rivers. Melt- 

 ing of ice occurs quickest wherever, for one reason or another, there are large areas of clear 

 water at the start of melting. 



In the seas of the Soviet Arctic, on the average, the breakup of shore and fast ice occurs 

 earliest in the southern Novozemelski Straits (in the latter third of June), and latest in the 

 Vilkitski Straits (at the beginning of August). It is clear that after the breakup of the fast ice, the 

 centers of breakup become also the centers of melting. 



In the open parts of the arctic seas the conception of breaking up of sea ice is not applicable, 

 since even in winter these areas are covered with broken-up floating ice floes. 



From table 89 we have seen that with ice thickness equal to 100 cm and with absorption by 

 water of 300 g-cal per square cm per day in 16 days nine-tenths ice will become eight-tenths ice, 

 and five-tenths ice completely melts away. 



321 



