UV in Ny-Ålesund

Last updated 26 February 2024

Excessive doses of ultraviolet (UV) radiation can damage the development and growth of plants and microorganisms, and cause, for example, sunburn and skin cancer in humans. Monitoring of UV radiation in Ny-Ålesund started in 1996.

Status and trend

The ozone layer protects plants, animals and humans from harmful UV radiation from the sun.

In the 1980s and 1990s, gradual thinning of the ozone layer was observed in most parts of the world. The main reason was high emissions of ozone-depleting substances. In 1987 the Montreal Protocol, requiring the industrialised nations to reduce the emissions, was signed. The major focus on the ozone situation in the 1990s led to the initiation of several programmes to monitor ozone and UV radiation in many countries around the world.

Since the signing of the Montreal Protocol, emissions have been reduced by more than 95%. This seems to be having positive effects on the ozone layer. It is nevertheless vital to monitor the trend in UV radiation in the coming decades.

UV measurements in Ny-Ålesund began in 1995, in a period when the ozone layer was at its thinnest. It should therefore be expected that UV radiation showed a tendency to decline in the years after 1997, in pace with the thickening of the ozone layer. However, it is difficult to draw such a conclusion from our measurements. This is chiefly because the cloud cover varies greatly from year to year and will affect the UV radiation just as much as a possible increase in ozone.

Causal factors

Ozone holes are caused by emissions of industrial chemicals, especially chlorofluorocarbons (CFCs).

The CFC gases, which are very stable on the Earth’s surface, react effectively with the ozone in the stratosphere. Under the special geophysical conditions in the polar stratosphere, the gases trigger chemical processes which lead to the rapid breakdown of ozone.

In the early-1980s, a substantial reduction in the ozone layer over Antarctica was observed from September to November and the situation gradually deteriorated until the mid-1990s.

Normally, the highest ozone concentrations are found in the stratosphere at 10-25 kilometres up (in polar regions), but measurements from Antarctica showed that ozone concentrations at 12 to 20 kilometres were virtually zero in the Antarctic spring. The geographical extent of ozone depletion could also be measured far beyond the Antarctic continent.

This situation still arises from September to November each year and is termed the “Antarctic Ozone Hole”. As a consequence of the Antarctic Ozone Hole, UV radiation has increased to levels normally measured in middle latitudes.

This has raised questions surrounding the development of the UV level in the northern polar regions, but annual huge ozone holes are unlikely to arise in northern areas. This is mainly because the stratosphere in the north is warmer than in the south and the polar wind systems differ. The topography and meteorology in the Arctic are quite different from conditions in the Antarctic.

However, climate change is expected to lead to warming of the troposphere and cooling of the stratosphere. A colder stratosphere will give more frequent occurrences of polar stratospheric clouds (PSCs), which can give strong ozone depletion, called “mini-holes”, also in Arctic regions. Such ozone hole was observed in spring 2011 and 2020, for example.

Consequences

UV radiation is most important for health and the environment. As there is a close relationship between the thickness of the ozone layer and the UV radiation at ground level, a thinner ozone layer may have major environmental consequences.

Modelling implies that human-induced climate changes will reduce the temperature in the stratosphere and increase the formation of Polar Stratospheric (ice) Clouds (PSC, or nacreous clouds) in Arctic regions. This can lead to ozone depletion and a corresponding increase in UV radiation.

The thawing of polar ice may also put marine organisms at greater risk of exposure to UV. However, as there is a very complex link between stratospheric ozone and long-lived climate gases, the net effect on the ozone layer is uncertain.

About the monitoring

Continuous measurements of stratospheric ozone and several halogenated greenhouse gases are conducted by NILU, as part of the Norwegian Environment Agency’s program for Greenhouse gases, ozone layers, UV radiation and atmospheric pollution.

When interpreting the monitoring results, it is important to be aware that the strength of UV radiation at the surface depends on several factors.

The most important reason for variations in UV radiation is the cloud cover, but the ozone layer can also have a significant impact, both from day to day and year to year.

A 1% thinner ozone layer gives just over a 1% rise in the UV level. Influence from other important factors:

• Cloud cover
  A thick cloud cover will reduce UV radiation by up to 90%.
• Reflection from the ground
  Newly fallen snow can reflect over 90% of the UV rays and substantially raise UV doses near the ground.
• Height of the sun
  The low height of the sun, even in summer, is the main reason why levels of UV radiation at high latitudes, like in Ny-Ålesund, are in general relatively low.
• Aerosols
  Even low concentrations of aerosols in the atmosphere can contribute to a reduction in the UV level.