High levels of ultraviolet radiation observed by ground-based instruments below the 2011 Arctic ozone hole

Abstract

Abstract. Greatly increased levels of ultraviolet (UV) radiation were observed at thirteen Arctic and sub-Arctic ground stations in the spring of 2011, when the ozone abundance in the Arctic stratosphere dropped to the lowest amounts on record. Measurements of the noontime UV Index (UVI) during the low-ozone episode exceeded the climatological mean by up to 77% at locations in the western Arctic (Alaska, Canada, Greenland) and by up to 161% in Scandinavia. The UVI measured at the end of March at the Scandinavian sites was comparable to that typically observed 15–60 days later in the year when solar elevations are much higher. The cumulative UV dose measured during the period of the ozone anomaly exceeded the climatological mean by more than two standard deviations at 11 sites. Enhancements beyond three standard deviations were observed at seven sites and increases beyond four standard deviations at two sites. At the western sites, the episode occurred in March, when the Sun was still low in the sky, limiting absolute UVI anomalies to less than 0.5 UVI units. At the Scandinavian sites, absolute UVI anomalies ranged between 1.0 and 2.2 UVI units. For example, at Finse, Norway, the noontime UVI on 30 March was 4.7, while the climatological UVI is 2.5. Although a UVI of 4.7 is still considered moderate, UV levels of this amount can lead to sunburn and photokeratitis during outdoor activity when radiation is reflected upward by snow towards the face of a person or animal. At the western sites, UV anomalies can be well explained with ozone anomalies of up to 41% below the climatological mean. At the Scandinavian sites, low ozone can only explain a UVI increase of 50–60%. The remaining enhancement was mainly caused by the absence of clouds during the low-ozone period.

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

“…latitude, date and time of day), and the composition of the atmosphere (e.g. ozone, and the amount and type of clouds and aerosols) (Vavrus et al, 2010;Bernhard et al, 2013). In surface waters across the Alaskan Arctic (from Toolik Lake to Barrow, AK), the sun is above the horizon from approximately midMay through mid-July, but ∼ 90 % of the daily UV flux involved in DOM degradation reaches surface waters during the day due to the low solar zenith angle overnight (Alaska, Cory et al, 2014).…”

“…In surface waters across the Alaskan Arctic (from Toolik Lake to Barrow, AK), the sun is above the horizon from approximately midMay through mid-July, but ∼ 90 % of the daily UV flux involved in DOM degradation reaches surface waters during the day due to the low solar zenith angle overnight (Alaska, Cory et al, 2014). Clouds generally decrease surface UV, but the effect of clouds can be offset by ozone levels, making it difficult to predict surface UV based only on latitude and date across the Arctic (Vavrus et al, 2010;Bernhard et al, 2013). Although less UV generally reaches surface waters in the Arctic compared to lower latitudes due to lower solar zenith angles, thermokarst lakes and ponds can often have high concentrations of light-absorbing DOM that is susceptible to photo-degradation, thus potentially counter-balancing the lower UV (Alaska, Cory et al, 2014; sub-Arctic Sweden, Koehler et al, 2014).…”

Operational surface UV radiation product from GOME-2 and AVHRR/3 data

“…Solar noon UV index derived from Metop-A and NOAA-19 data on 30 March 2011 during the Arctic ozone hole episode when exceptionally large values of UV index for the point in time were observed in the Arctic. In Sodankylä, northern Finland, a solar noon UV index of 2.14 was measured at ground level exceeding the climatological value by 100 % (Bernhard et al, 2013). A slightly smaller value of 1.9 is obtained from the OUV product due to averaging of cloud cover over a larger area than is seen by the ground-based instrument.…”

Trends in erythemal doses at the Polish Polar Station, Hornsund, Svalbard based on the homogenized measurements (1996–2016) and reconstructed data (1983–1995)

“…Since 1980, especially large ozone depletion was observed every year in the late winter and spring (the so-called ozone hole) over Antarctica (e.g., WMO, 2014). However, severe ozone losses appeared occasionally over the Arctic, e.g., in 2011 (Garcia, 2011;Bernhard et al, 2013) and in 2016 (http://www.ametsoc.net/sotc2016/Ch05_ Arctic.pdf). The ozone downward trend and the increase in the surface UV in the Arctic was observed in 1990s (Fioletov et al, 1997;Newmann et al, 1997;Gurney, 1998).…”