Arctic Yearbook 2012
Shipping and Resources in the Arctic Ocean
250
sea ice. Ice conditions are in general more difficult along the eastern extremity of the route than in
the west. In the Laptev, East Siberian and South-western Chukchi seas five
ice massifs –
large areas of
close and very close ice – are identified. These massifs often block the entrances to important
navigational straits along the route.
Figure 3: The Northeast Passage and Northern Sea Route
Source: Løvås & Brude, INSROP GIS, 1999.
Although some of these ice massifs are relatively stable, they on rare occasions disappear at the end
of the melt season, but reoccur again in winter (Johannessen et al., 2007: 283-285). The eastern
sector is also the part of the route with the most shallow shelf areas. The East Siberian Sea has an
average depth of 58 meters and the Chukchi Sea of 88 meters. The shallowness of the shelf is the
most pronounced in the straits, with minimum depths of 8 meters. This affects the size, volume and
draft of ships. The ocean areas west of the Yamal Peninsula are fortunate in having a slightly deeper
shelf and lighter ice conditions in average than the eastern sector. This is partly due to the
circumstance that the Kara Sea is surrounded to the north by several archipelagos which usually
prevent heavy multi-year ice from the Central Arctic Ocean from penetrating into these waters.
Multi-year ice, which is extremely hard and consequently a very serious obstacle to navigation, has
survived the summer melt season and is typically up to 5 meters thick. The eastern sector lacks this
kind of land protection and is more open to the influx of multi-year ice from the Central Arctic
Basin. However, even in the East ice conditions are changing due to global warming. Here, new
extreme minima of summer ice extent have been established repeatedly ever since 1979 (Weller 2000:
43). In seven of the last ten years, the Chukchi Sea was ice free with periods extending from one
week to as much as two and a half months. In contrast, there was always ice over the Chukchi Sea
shelf in all of the previous 20 years.