See also:

Summer temperatures

Arctic Borderlands Ecological Knowledge Co-op

What is happening?

• Our northern latitude causes dramatic changes in day length and light intensity over the course of the year. This graph shows that the amount of UV-B (ultraviolet radiation) rises in the spring, reaches a peak in mid-summer and declines to low levels again as fall approaches.
• The UV Index is a relative measure of ultraviolet light intensity and varies on a scale from 0 to 10. The values we find in Ivvavik are at the very low end of the scale; moderate index levels between 4 and 6 are commonly recorded in southern Canada during summer.

Why is it happening?

• Naturally occurring ozone in the upper atmosphere acts as a protective filter to reduce the intensity of UV-B rays arriving at the earth's surface. Many human activities have added chemicals to the atmosphere which break down the upper level ozone and this has led to concerns over increasing UV-B levels.
• At our high latitude light travels through the atmosphere at a shallow angle. As a result more of the light energy (including UV-B) is absorbed by the atmosphere before it reaches the ground than in southern latitudes.

Why is it important?

• Exposure to higher levels levels of UV-B rays can affect human health (e.g. increased risk of skin cancers, cataracts) as well as other parts of the ecosystem. Photosynthesis in green plants involves chlorophyl and increased amounts of UV-B can damage this critical plant pigment leading to poorer growth.

Technical Notes

• UV-B is ultraviolet radiation with a wavelength between 315-280 nanometers.
• The data presented here are collected by a sensor installed in an automatic weather station located in Ivvavik National Park.