Record-Breaking Increases in Arctic Solar Ultraviolet Radiation Caused by Exceptionally Large Ozone Depletion in 2020

Abstract

Measurements of solar ultraviolet radiation (UVR) performed between January and June 2020 at 10 Arctic and subarctic locations are compared with historical observations. Differences between 2020 and prior years are also assessed with total ozone column and UVR data from satellites. Erythemal (sunburning) UVR is quantified with the UV Index (UVI) derived from these measurements. UVI data show unprecedently large anomalies, occurring mostly between early March and mid-April 2020. For several days, UVIs observed in 2020 exceeded measurements of previous years by up to 140%. Historical means were surpassed by more than six standard deviations at several locations in the Arctic. In northern Canada, the average UVI for March was about 75% larger than usual. UVIs in April 2020 were elevated on average by about 25% at all sites. However, absolute anomalies remained below 3.0 UVI units because the enhancements occurred during times when the solar elevation was still low. Plain Language SummaryThe ultraviolet radiation (UVR) from the Sun depends on the amount of ozone in the atmosphere. During March and April 2020, ozone concentrations in the Arctic atmosphere were exceptionally low and this led to large increases in UV radiation at the surface. These increases were quantified by analyzing data from ground-based instruments at 10 Arctic and subarctic locations, as well as satellite data. UV levels were quantified with the UV Index (UVI), which measures the amount of "sunburning" UVR. The greatest UVI increases were observed between early March and mid-April 2020. For several days, UVIs observed in 2020 exceeded measurements of previous years by up to 140%. In northern Canada, the average UVI for March was about 75% larger than usual. UVIs in April 2020 were elevated on average by about 25%. However, these large relative anomalies occurred early in the year when the Sun is still low in the sky. UVI increases remained therefore small in absolute terms and did not exceed typical summertime UVI values under clear skies.

Environmental effects of ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2017

“…However, absolute increases remained below 1 UVI unit because the event occurred early in the year when UV radiation is low. 15 Analysis of ozone observations in 1979-2012 revealed a statistically significant association between low values of Arctic stratospheric ozone in March and changes in climate between 30 and 70°N in March and April. 16 The changes in climate include a poleward shift of the North Atlantic jet stream, lower than normal surface temperatures over eastern North America, Southeastern Europe, and Southern Asia, and higher than normal temperatures over Northern and Central Asia.…”

Record‐Low Arctic Stratospheric Ozone in 2020: MLS Observations of Chemical Processes and Comparisons With Previous Extreme Winters

“…Further, minimum vortex-averaged O 3 occurred near 440-460 K in 2020 but 480-500 K in 2011; thus, even when values dipped as low in 2011, they were at smaller pressures and consequently affected the total column less. Record-low column ozone and associated record-high surface ultraviolet will be discussed in other papers in this special collection (e.g., Bernhard et al, 2020;Grooß & Müller, 2020;Wohltmann et al, 2020).…”

Simulation of Record Arctic Stratospheric Ozone Depletion in 2020

“…Here we report on simulations using the model Chemical Lagrangian Model of the Stratosphere (CLaMS) which show unprecedented Arctic ozone depletion in the year 2020 (Dameris et al., 2021; Feng et al., 2021; Manney et al., 2020; Wohltmann et al., 2020) accompanied by a significant increase in surface UV radiation (Bernhard et al., 2020). The reported simulations indicate that the major causes of the severe ozone depletion reported in the Arctic in 2020 are the low stratospheric temperatures and the exceptionally stable polar vortex extending into spring (Lawrence et al., 2020).…”