How has the intensity of UVB radiation changed recently in the Arctic, and what significance might these changes have?
UV radiation: the unexplored threat to the Arctic
University of Colorado CIRES / NOAA
The Arctic has long been an area at high risk from UV radiation damage. Although the sun never rises far above the horizon, the highly reflective snow surface results in damaging levels of UV to unprotected eyes and vertical surfaces such as faces, trees and shrubs. Normally, ozone in the stratosphere shields the Earth from much of the harmful UV radiation. However, recent measurements in the Arctic show long-term decreases in the amount of ozone overhead, called total column ozone. In addition, scientists have observed more frequent episodes of extremely low ozone, particularly during the springtime. The Arctic contains fragile ecosystems and peoples facing increasing health challenges. In such an environment, increased UV radiation may cause more damage than elsewhere.
in Arctic ozone and UV
In the last few decades, and particularly in the 1990s, anthropogenic influences on the natural ozone layer have resulted in severe ozone depletion in polar regions. Ozone depletion has been considerably larger in the Arctic than at mid-latitudes: Antarctica and the surrounding areas are the only regions with more severe ozone depletion. During springtime in the Arctic, the combined effect of higher surface reflectivity, rising sun angles and enhanced stratospheric ozone depletion can result in higher UV levels than have occurred in the Arctic in recent history. Spring is often the time when biological systems are most susceptible to UV damage: natural protective measures, such as pigmentation and thickening of leaves, have not had time to develop and fish larvae are most exposed. The combination of biological sensitivity, already high UV levels and increased ozone depletion in the spring are likely to result in a more severe risk to the Arctic environment.
The high UV levels in the Arctic have been known to cause sunburn (erythema) and snow blindness (photokeratitis) under normal conditions. UV can affect immune suppression in humans and cause long-term health problems including cataracts, skin cancer and a number of related skin diseases. UV effects on ecosystems are widespread, affecting individual species-particularly at the base of the food chain-as well as the relative abundance of species. Certain phytoplankton, for instance, are especially sensitive to UV, and reductions in their populations impact not only the individual species, but also organisms that compete with or feed on these populations. Cod, herring, pollock, salmonids, and other fish species spawn in shallow waters where the larvae can be fully exposed to ambient solar and UV radiation. Higher UV levels can be particularly damaging to these larvae, and a reduction in the number of larvae reaching maturity can mean dramatic impacts for the fishing industry.
UV and multiple
Multiple stressors in the Arctic, including pollutants, climate change and water accessibility may combine non-linearly with the stress from increased UV radiation. Many of these stressors are expected to remain significant or, as is the case for climate change, increase in the Arctic in the coming years. The few studies that have examined the multiple impacts indicate that the combined effects may be much more severe than the individual impacts. Recent research has explored the role of UV radiation in enhancing the toxicity of certain chemical compounds, particularly those associated with oil spills or petroleum contamination. Called photoenhanced toxicity, the combination of UV light and certain molecules can seriously injure, and even kill, sensitive species. Results show, for instance, that 100% of shellfish embryos that were exposed to three-day-old spill water under UV light were killed. By contrast, only 40% of the embryos exposed to the same water under fluorescent (low UV output) light suffered fatalities.
for the future
Elevated UV levels due to ozone depletion are expected to continue in the Arctic. Current estimates indicate that stratospheric ozone levels will continue to deplete for the next two decades. Because decreased ozone levels in the Arctic are determined not only by man-made chemicals, but also by climate change, it is unclear whether or not, under current international legislation, Arctic ozone levels will return to normal.
For more information:
Arctic Monitoring and Assessment Programme (AMAP), 1998, AMAP Assessment Report: Arctic Pollution Issues. AMAP, Oslo, Norway, xii=859 pp.
Ho et al. The chemistry and toxicity of sediment impacted by the North Cape Cod oil spill in Rhode Island sound. Mar Poll Bull 38:314-323, 1999.
UV Radiation Page, http://www.srrb.noaa.gov/UV/.
Shindell, et al. Increased polar stratospheric ozone losses and delayed eventual recovery owing to increased greenhouse gas concentrations. Nature 32:589-592, 1998.
UV Radiation in the Arctic, Past, Present and Future from the Norwegian Research Database