Atmosphere: the Polar Regions

The key atmospheric issues in the Arctic and Antarctic are the depletion of the stratospheric ozone layer, the long-range transport of air pollutants and warming associated with global climate change. These problems are mainly due to anthropogenic activities in other parts of the world.

Seasonal stratospheric ozone depletion over Antarctica, and more recently over the Arctic, has been one of the major regional environmental concerns since it was noticed in 1985 (Farman and others 1985). The depth, area and duration of the Antarctic ozone hole has steadily increased, reaching an all-time high of around 29 million km² in September 2000 (WMO 2000, NASA 2001).

In the Arctic, average yearly stratospheric ozone levels in the 1990s had declined by 10 per cent from the late 1970s, increasing the risk of snow blindness and sunburn.

Monthly mean ozone levels at Halley Bay, Antarctica (Dobson units)

Monthly mean ozone levels at the Halley Bay site during the onset of the Antarctic spring Source: BAS 2000

The recovery of the stratospheric ozone layer in the polar regions depends primarily on the implementation of the Montreal Protocol on the Substances that Deplete the Ozone Layer. Therefore the efforts of nations to phase out the use of ODS, even though they are located far from the poles, are of the utmost importance (UNEP 2000).

Natural ecosystems in polar regions have low adaptive capacity and are highly vulnerable to climate change. Climate change is expected to be more extreme in the polar regions than anywhere else (a warming trend of as much as 5ºC over extensive land areas has been noted in the Arctic, although there are some areas in eastern Canada where temperatures have declined) and will probably have major physical, ecological, social and economic impacts in both the Arctic and the Antarctic (IPCC 2001a and b). Whether due to a natural oscillation or global climate change, the atmospheric temperature of Antarctica is undergoing changes. A marked warming trend is evident in the Antarctic peninsula with spectacular loss of ice shelves and an increase in the cover of higher terrestrial vegetation although, as in the Arctic, there are also areas of marked cooling - at the South Pole for example (Neff 1999).

Climate change is almost certainly responsible for the decrease in extent and thickness of Arctic sea ice, permafrost thawing, coastal erosion, changes in ice sheets and ice shelves, and the altered distribution and abundance of species in polar regions (IPCC 2001a). Other impacts of the warming trend include a recorded 15 per cent increase in Arctic precipitation, increased storm episodes, earlier springs and a later onset of freezing conditions, and decreased marine salinity (AMAP 1997). Permafrost thawing can itself add to climate change problems - for example, emissions of methane from tundra may increase while reductions in the extent of highly reflective snow and ice cover will magnify warming. These effects may continue for centuries, long after greenhouse gas concentrations are stabilized, and may cause irreversible impacts on ice sheets, global ocean circulation and sea-level rise (IPCC 2001a).

'The permafrost zone covers 58 per cent of the territory of the Russian Federation. Many human settlements, industrial plants and infrastructure are located in this zone. Given the current warming trend, the border of the permafrost zone could move 300-400 km northward by 2100.' - Interagency Commission 1998

Since most industrial countries are in the Northern Hemisphere, the Arctic is more exposed to anthropogenic air pollution than the Antarctic. Prevailing winds carry polluting substances - including heavy metals, POPs and sometimes radionuclides - into the Arctic where they can stay airborne for weeks or months and be transported over long distances (Crane and Galasso 1999). Over much of the Arctic, levels of certain types of pollutants are so high that they cannot be attributed to sources within the region; they come from much further south.

Major sources of anthropogenic radionuclides in the Arctic include fall-out from nuclear tests, releases from nuclear fuel reprocessing plants, and fall-out from the 1986 Chernobyl nuclear power plant accident. A significant increase of radioactivity in Arctic indigenous people was registered after the Chernobyl accident, particularly amongst those who consumed significant quantities of foods that concentrate radiocaesium, such as reindeer meat, freshwater fish, mushrooms and berries. The phenomenon was mainly observed in 1986-89 in Norwegian and Swedish Saami and up to 1991 in the indigenous population of the Kola Peninsula, in the Russian Federation. Since then the levels have been gradually falling back towards the pre-accident levels (AMAP 1997).

Radioactive contamination after Chernobyl

Levels of caesium 137 (1 000 becquerels/m2) in Scandinavia, Finland and the Leningrad region of Russia following the Chernobyl explosion in 1986 Source: AMAP 1997

Within the Arctic, the Russian Federation's industrial complexes have been a major source of atmospheric pollution. Emissions of sulphur compounds and heavy metals from smelters have caused major forest degradation on the Kola Peninsula and have decreased the number of species in the region. The areas severely affected by air pollution around the Nickel-Pechenga and Varanger smelters increased from around 400 km² in 1973 to 5 000 km² in 1988 (AMAP 1997). Since 1990, emissions from Russian smelters have decreased or stabilized mainly because of the economic slowdown.

The level of air pollution in the Arctic is so high that 'Arctic haze' has become a major problem. The term was coined in the 1950s to describe an unusual reduction in visibility that the crews of North American weather reconnaissance planes observed during flights in the high latitudes in the Arctic. The haze is seasonal, with a peak in the spring, and originates from anthropogenic sources of emission outside the Arctic. The haze aerosols are mainly sulphurous (up to 90 per cent) originating from coal burning in the northern mid-latitudes, particularly in Europe and Asia. The particles are about the same size as the wavelength of visible light, which explains why the haze is so apparent to the naked eye.

Improvement in the state of the polar environment depends primarily on policies and measures implemented by people inside and outside of the polar areas. The Arctic countries have taken a number of steps to improve air quality. These include signing the Convention on Long-Range Transboundary Air Pollution (CLRTAP) and the relevant protocols to it, and supporting the development of the Stockholm Convention on Persistent Organic Pollutants. In addition, domestic regulatory measures taken in the United States and Canada have reduced emissions of some POPs, heavy metals and sulphur compounds. Actions to address stratospheric ozone depletion rely on the successful implementation of the Montreal Protocol by all nations (UNEP 2000).

Given the predicted increase in the global mean temperature, climate change will impose significant pressures on the polar regions in the 21st century. These impacts are likely to be exacerbated by the high vulnerability and low adaptive capacity of polar ecosystems and of some traditional indigenous communities. Despite increasing activity in both the domestic and international arenas, only preliminary steps have been taken to address the problem of global climate change. The main regional challenge is therefore enhancing the potential for adaptation to change that should help mitigate adverse impacts. The Arctic countries have initiated an Arctic Climate Impact Assessment to be completed in 2003. It will be integrated into the regional studies of the IPCC (ACIA 2001).