Figure 146b. State of ice in Vilkitski Strait on 24 July 1943. 



However, prevailing winds create a steady drift of ice in approximately the same direction. 

 For example, the large polynyas created by the combined influence of the prevailing winds and the 

 steady drift of ice were often observed by the Ushakov Expedition of 1930 to 1932 off the northwest 

 coast of Sevemaya Zemlya, permanent polynyas and leads are also a common phenomenon north- 

 west of Franz Joseph Land, as noted as far back as the Weyprecht - Payer Expedition. 



One of the main reasons for the formation of this so-called great Siberian lead is the prev- 

 alence of easterly leads which create a steady northwest drift of pack ice, i.e. , from the shore 

 toward the shore ice. This has been traced northwest, north and northeast of the New Siberian 

 Islands, and is called the New Siberian Lead, and in the region to the north of the Kolyma region, 

 this is called the Kolyma Lead. 



In winter, both these stretch discontinuously along the northern edge of the developed shore 

 ice and sometimes are situated farther north or south depending on the conditions of the shore ice. 

 Under the influence of northerly winds these leads sometimes become covered with ice arriving 

 from the north and then intense hummocking occurs along the line of contact. However, in general, 

 both are constant phenomena. 



The New Siberian Lead was first described by Hedenstrom, who traveled along the ice in 

 March and April 1810 from Cape Kamennyi on New Siberian Island 40 miles to the northeast and was 



395 



