Natural Conditions and Navigation through the Northeast Passage

(by Karl Magnus Eger)

Introduction

The ice conditions along the NEP are dynamic, leading to large annual, seasonal and regional variations and it has traditionally been playing a great role both by volumes of cargo shipped and by its strategic significance (see chapters 1 and 2). Various parts of the NSR have been in regular use for coastal Russian cargo movements for many years between July and October. In winter the sailing routes are covered with ice, and even in the summer some parts are ice covered, especially in the Laptev Sea and the East Siberian seas. Difficult ice-conditions often exclude the use of the shortest route between two points, and lead to the need of ice breaker assistance.

Natural Conditions and Shipping along the Barents and Kara Seas

An important feature of ice conditions of the Barents Sea is that, unlike the Kara Sea and other Siberian Shelf seas, it is never completely ice covered. In the winter the ice area in the Barents Sea usually comprises 55-60% of the total sea area. The constant presence of non-freezing areas in the Barents Sea means that a zero heat budget zone is located in this region in the winter. Based on its geographical location and natural conditions, the Kara Sea is subdivided into two large areas, the north-eastern and south-western, in which ice conditions are poorly related. In the winter the entire Kara Sea is covered with close drifting ice with fast ice occupying large areas of the coastal areas. Its south-eastern part is covered by ice of local origin with a predominant thickness up to 1.5 metres for 8-10 months a year, whereas summer it is usually completely ice free. Freeze-up of the south-western Kara Sea usually occurs in October, in the absence of residual ice. The north-eastern part is not completely free of drifting ice during the summer. In the north western part, young ice forms among residual ice in September. After that and until the summer, the Kara Sea is covered with close drifting ice¹ .

Two ice massifs are locates in the western area of active shipping: Novozemelsky and Severozemelsky, which is less compared to the eastern part of the NSR with its five ice massifs. The size of the ice massifs comprises several hundred square kilometres at maximum development. Usually, by late June the Novozemelsky ice massifs occupies about 80% of the south-western Kara Sea (See fig. 4.6). By mid-August, the areas of Novozemelsky massif and close ice in all regions are usually less than 20% and in September less than 10%¹ . Severozemelsky ice massifs are identified in the north-eastern Kara Sea along the Taymyr coast and Severnaya Zemlya. In May, fast ice and close drifting ice are located over the entire area. On average, in September it is less than 10% and 30% in the western and eastern Severozemelsky regions¹ .

The Kara gate strait is the main shipping lane between the Barents and Kara seas, connecting the western part of NEP with the NSR. The 18 nautical miles strait has a minimum depth of 21 meters and shipping uses an established traffic separation scheme. Maximum fog and low visibility occur during July and August. In winter Kara Gate strait is covered with drift ice. The duration of the sailing season without icebreaker escort is 3 - 3.5 months² .

Yugorskiy Shar Strait is located along the south coast of Vaygach Island and is the southernmost entrance from the Barents to the Kara seas, also connecting the western part of NEP with the NSR. It is 21 nautical miles in length, 5.5 nautical miles wide at its narrowest and has depths ranging from 13-15 meter in the west to 16-30 meters in the east. Hazardous sand shoals are located in the middle and eastern regions. Ice is present in the strait from November to July. The duration of navigation without icebreaker assistance is between 3 and 3.5 months.

Natural Conditions and Shipping along the Laptev Sea

The Laptev Sea has the largest expanse of fast ice in the world from January till June (See fig. 4.5). The fast ice thickness typically reaches 200 centimetres due to mean midwinter air temperature of minus 30 degrees Celsius and can grow up to 250 centimetres during severe winters. The concentration of multiyear ice in the Laptev Sea is limited due to wind directions and ocean currents. The total area of summer melt is particularly extensive due to the reduced concentration of multiyear ice. In the western part the ice drift is southwards and large masses of ice are deposited along the coast of Severnaya Zemlya and the Taymyr Peninsula.

Along with the eastward ice deposition from the Kara Sea, the Vilkitskii Strait and the Taymyr coast present a serious challenge to navigation at all times of the year³ . The Vilkitskii Strait is the main connection (60 nautical miles) between the Kara and Laptev Seas and a key strait along the NSR. With its depth of 100-200 metres, ships of any size and draft can pass through. However, the eastern and western approaches to the Vilkitskii Strait can be clogged with ice fields, depending on wind direction; icebreaker escort can be complicated. Fast ice can be present in the strait until August.

Shokalskiy Strait is located in Severnaya Zemlya north of the Vilkitskii Strait, and is a second shipping route between the Kara and Laptev seas. The 80 nautical miles strait (10 nautical miles wide at its narrowest point) has a minimum depth of 37 meters and depth will not be a limiting factor for any ships. Still, ice conditions in the Vilkitskii Strait are generally more favourable² .

Natural Conditions and Shipping along East Siberian Sea

The East Siberian Sea is the shallowest of the Eurasian seas. The broad continental shelf allow fast ice, averaging from 170-200 centimetres thick, to extend as far as 500 kilometres outward from the coast (See fig. 4.5). In winter the prevailing wind direction is from the south producing weak ice conditions and potential navigation lanes at the outer edge of the fast ice like in the Kara and Laptev seas.

The East Siberian Sea has the highest fraction of old ice and the Ayon massif has more than 60% of old ice and the average thickness may be 250 centimetres in the winter months. The eastern East Siberian Sea is less ice-free than the other region. In the summer the winds shifts to northerly and the ocean current favour the influx ice form the north resulting in the permanence of the Ayon massif. Ice melting in the East Siberian Sea begins only under the influence of the solar radiation heat and advection of atmospheric heat and about 50% of the East Siberian Sea is ice free before the onset of ice formation¹ . Winter freeze-up begins in the north in September and is usually complete by mid-October.

Dmitri Laptev Strait is the southernmost passage between the New Siberian Island and the mainland, linking the Laptev and East Siberian seas. It is 63 nautical miles long, and 30 nautical miles wide and oriented east-west. The strait has a depth of 12-15 meters; however, the eastern approach has depths of 10 meters or less, restricting traffic to ships with less than 6.7 meter draft.

Sannikov Strait is a second passage through the New Siberian Islands linking the Laptev and East Siberian seas. It is 160 nautical miles long and a minimum depth of 13 meters. From a navigation point of view, the low surrounding New Siberian Islands make visual and radar observations difficult to obtain, particularly during long periods of reduced visibility⁴ .

Natural Conditions and Shipping along the Chukchi Sea

On the eastern part of the NSR, the southern Chukchi Sea becomes ice free earlier than the other regions. The seasonal variations in the ice conditions are large resulting in losing about 80% of its maximum winter extent in the summer season. Important factors influencing the variability are the bathymetry, wind, currents, air temperature and the presence of Wrangle Island. Due to advection of comparatively warm Bering water, up to 10% of ice in south-western sea area melts as early as in late May, on average. The Chukchi Sea is almost ice covered from early December to mid-May. However, ocean currents and wind tend to transport old ice form the Arctic to the Longa Strait under great pressure, which sometimes presents the greatest obstacle on the route³ .

Long Strait separates Wrangle Island from the mainland linking the East Siberian and Chukchi seas. Two general routes through this wide (75 nautical miles) passage are described: a 120 nautical miles southern route with 20 meters minimum depths, and a 160 nautical miles northern route with 33 meters minimum depths. Draft will not be a problem as long as ships keep well offshore from the mainland. During winter, fast ice extends. Hazardous ice conditions for navigation can occur when old ice and ice massifs are displaced into the strait region⁵ .

Discussion

Although there is some projected winter retreat of the sea ice edge, particularly in the Bering and Barents Seas where ship access is likely to improve throughout the 21st century, most of the Arctic Ocean is projected to remain ice covered in the winter. Sailing during the winter season (November-May), is generally much more difficult than in the summer season, due to the thicker ice cover. An important, special feature of winter navigation is the fast ice – stable, immovable ice which is “clinging” to the coastline. Depending on the location of islands and sea depths, the fast ice may be extending up to 500 km from the Russian mainland. Fast ice is very difficult to pass through, and normally it is preferable to avoid it by using northerly routes. If off-shore winds prevail, one will often during winter find open leads at the edge of the polynyas, which are very suitable for navigation.

Typical location of fast ice and polynyas is illustrated in figure 4.4. In that respect, the Kara Sea offers the easiest conditions for navigation. Here, the extension of the fast ice is normally small, but the existence of polynyas is also relatively normal. The only areas where polynyas are not often found are the eastern East Siberian Sea and the Chukchi Sea. This is again mainly due to currents pushing ice from the central Arctic Basin towards the coast, thus creating extremely difficult ice conditions.

Fig. 4.4: Regions of Winter Fast Ice and Polynyas on the NSR

Polynyas: 1 – Cheshskaya, 2 – Pechora, 3- West Novaya Zemlya, 4 – Victoria Sea, 5 – Amderma, 6 – Yamal, 7 – Ob-Yenisey, 8 – West  Severnaya Zemlya, 9 – East Severnaya Zemlya, 10 – Taymyr, 11 – Lena, 12 – New Siberian, 13 – Wrangel, 14 – Alaska, 15 – Anadyr  Source: Ragner (2000)

Fig. 4.5: General Locations of Summer Ice Massifs on the NSR

Noted are three types of summer ice massifs: Multiyear ice from the Arctic Ocean (North Kara, Taymyr and Ayonskiy); local drift ice (Novaya Zemlya and Wrangel); and, fast ice remnants (Severnaya Zemlya, Yanskiy and New Siberian). Source: Ragner (2000)

The fact that both Severnaya Zemlya and the New Siberian Islands normally become enveloped by the fast ice, will often force ships to choose a route north of these archipelagos, routes which may expose the ships to extremely harsh ice conditions, in addition to being a detour. The summer season has traditionally been defined as June-October, but technological improvements have gradually allowed an extended summer season, with navigation until December in years of favourable ice conditions. Today, it is only shipping on the Dudinka-Murmansk line that operates on a year-round basis. All other transport is carried out only during summer.