* Sannikov Strait
Sannikov Strait is a second passageway through the New Siberian Islands (Novosirskiye Is.) linking the Laptev and East Siberian Seas. The strait is approximately 160NM long, with a fairway width of 16-18NM, whose minimum depths are more than 13m. The low surrounding islands make visual and radar navigation difficult. Stable fast ice covers the strait from the end of autumn to the beginning of summer. In some unfavorable years, the strait remains icebound year round.
* Long Strait
Long Strait separates Wrangel Island from the mainland, linking the East Siberian and Chukchi Seas. This strait consists of two passages through the wide channel, a 120NM southern passage with 20m minimum depths and a 160NM northern passage with 33m minimum depths, both of which are navigable. In winter the fast ice extends from the mainland to Wrangel Island, but it always recedes by the summer. However, the passages tend to remain clogged with ice massifs or multi-year ice.
Of these straits, an icebreaker escort is required for the navigation of Vilkitskiy Strait, Dmitry Laptev Strait, Shokalskiy Strait and Sannikov Strait.
(2) Ice conditions
Undoubtedly the presence of sea ice constitutes the critical factor in NSR navigation. NSR operations require the use of icebreakers and other ice-worthy ships, and in practice the routes taken through the NSR depend crucially on the condition of the ice. Ice conditions vary greatly from region to region and from season to season in the NSR. In the following section, we look at ice conditions in summer and winter. Rather than follow the traditional divisions of the four seasons, we will distinguish only between winter, defined as the period from October to May when the sea ice grows, and summer, defined as the period from June to September when the sea ice thaws. To view the differences in ice conditions from region to region, in Figure 4.2-2 we divide the NSR into seven regions from the Kara Sea to the Bering Strait (WP-121).
* Southwestern Kara Sea
* Northeastern Kara Sea
