Reduced sea-ice extent and thickness would increase the seasonal duration of polar navigation on rivers and in coastal areas that are presently affected by seasonal ice cover (IPCC 1996, WG II, Section 7.5). Improved opportunities for water transport, tourism, and trade at high latitudes are expected as a result. These activities will have important implications for the people, economies, and navies of nations along the Arctic rim (IPCC 1996, WG II, Chapter 7 Executive Summary). Reduced sea ice will provide safer approaches for tourist ships and new opportunities for sightseeing around Antarctica and the Arctic (IPCC 1996, WG II, Section 7.5.5). Increased calving of icebergs from the Antarctic Peninsula may, however, affect navigation and shipping lanes north of the Antarctic Convergence. Decreased sea-ice extent around Antarctica could make it easier for tourist vessels with less preparedness for sea-ice travel to visit the continent and surrounding islands. Some may be ill-prepared to navigate and respond to the extreme and highly variable environmental conditions in the Southern Ocean. There is no clear consensus, however, about whether the frequency of icebergs, and their danger to shipping, will change with global warming (IPCC 1996, WG II, Section 7.4). Increased precipitation may reduce the enthusiasm for tourism in some areas.
Projected reductions in the extent and thickness of the sea-ice cover in the Arctic Ocean and its peripheral seas could substantially benefit shipping, perhaps opening the Arctic Ocean as a major trade route (IPCC 1996, WG II, Technical Summary, Section 3.2.4). This projection would include the opening of both the NorthWest Passage and the Russian Northern Sea Route for up to 100 days a year. One French experiment indicated that the use of the Northeast Passage in ice-free seasons shortened by about 3 weeks the shipping duration between Europe and Far East Asia compared with the present route (i.e., via the Suez Canal). Although a reduction of sea ice may be a boon to international shipping and consumers in East Asia, North America, and Western Europe, policies designed to limit the total burden of pollutants entering the Arctic environment from ports, ship operations, and accidents may have to be developed (IPCC 1996, WG II, Chapter 8 Executive Summary).
Less river ice and a shorter ice season in northward flowing rivers of Canada and Russia should enhance north-south river transport. Combined with less sea ice in the Arctic, this development would provide new opportunities for reorganization of transport networks and trade links. Ultimately, those changes could affect Northern Hemisphere trading patterns (IPCC 1996, WG II, Section 7.5.1).
A survey of the potential impacts on Canadian shipping suggested net benefits to Arctic and ocean shipping due to deeper drafts in ports and longer navigational seasons, with mixed results for lake and river shipping due to the opposing effects of a longer shipping season but lower drafts. Demands to maintain Arctic shipping may increase. In Siberia and Canada, many rivers are used as solid roads during winter. Warmer winters would require a shift to water transport or the construction of more all-weather roads. Other impacts on means of transport could arise from changes in snowfall or melting of the permafrost (IPCC 1996, WG II, Section 18.104.22.168).
Currently, ice-breaking efforts are an expensive aspect of navigation in the Arctic. Interannual variability prevents the elimination of these programs unless extreme changes in sea ice should occur. Some ice-breaking programs in some areas may be cut back with moderate warming of the Arctic. In other areas, costs may rise to keep newly available routes open longer. A disappearance of sea ice south of Labrador would eliminate Canadian Coast Guard ice-breaking requirements. This would mean an annual saving of CDN$15-20 million. Even larger savings also can be expected in the former Soviet Union if ice retreats from the shores of the Kara, Laptev, and Chukchi Seas. Similar savings would accrue along the Gulf of Bothnia with the absence of ice. The effect of annual warming on ice calving (simulated using a simple degree-day model) shows that for every 1�C of warming there would be a 1� latitude retreat of iceberg occurrence in the Atlantic Ocean. In the Southern Ocean, any effects of reduced sea ice will be economically less pronounced (IPCC 1996, WG II, Section 7.5.3).
Offshore oil and gas exploration and production conducted at high latitudes may be assisted by a longer ice-free season. A possible beneficial effect would be shorter winters to disrupt construction, exploration, and drilling programs. A decrease in thickness and extent of sea ice in the Arctic will extend the drilling seasons for floating vessels considerably. A reduction in sea ice and icebergs also will reduce "downtime" on offshore oil and gas drilling explorations. Currently such interruptions cost Canadian explorations more than CDN$40 million annually. The most critical factor could be ice movement during winter. If there were increased numbers and severity of storm surges and wave activity, design requirements for offshore structures and associated coastal facilities would increase, and oil spill clean-up could become more difficult (IPCC 1996, WG II, Section 7.5.4).
The sub-Antarctic islands are small land areas surrounded by vast areas of the Southern Ocean. Some of these islands are sufficiently high to possess glaciers and small ice caps. Their climate is characterized by strong and persistent winds, little sunshine, many rain days, and cool temperatures. They are generally uninhabited, though they contain highly specialized flora and important marine mammal and bird populations.
Many of these islands have shown a tendency for warming over the last half of this century. Their future climate will be controlled by changes in the surface temperature of the Southern Ocean and the strength of Southern Hemisphere westerlies. The sub-Antarctic islands are expected to continue to warm. The impacts of climate change are unlikely to be important for most animal and bird species, but there could be changes in the species composition of plant communities. Glaciers will probably shrink.
Other reports in this collection