Persistent extreme ultraviolet irradiance in Antarctica despite the ozone recovery onset

Abstract

Attributable to the Montreal Protocol, the most successful environmental treaty ever, human-made ozone-depleting substances are declining and the stratospheric Antarctic ozone layer is recovering. However, the Antarctic ozone hole continues to occur every year, with the severity of ozone loss strongly modulated by meteorological conditions. In late November and early December 2020, we measured at the northern tip of the Antarctic Peninsula the highest ultraviolet (UV) irradiances recorded in the Antarctic continent in more than two decades. On Dec. 2nd, the noon-time UV index on King George Island peaked at 14.3, very close to the largest UV index ever recorded in the continent. On Dec. 3rd, the erythemal daily dose at the same site was among the highest on Earth, only comparable to those recorded at high altitude sites in the Atacama Desert, near the Tropic of Capricorn. Here we show that, despite the Antarctic ozone recovery observed in early spring, the conditions that favor these extreme surface UV events persist in late spring, when the biologically effective UV radiation is more consequential. These conditions include long-lasting ozone holes (attributable to the polar vortex dynamics) that often bring ozone-depleted air over the Antarctic Peninsula in late spring. The fact that these conditions have been occurring at about the same frequency during the last two decades explains the persistence of extreme surface UV events in Antarctica.

Genome-Wide Analysis of Long Non-Coding RNAs Related to UV-B Radiation in the Antarctic Moss Pohlia nutans

“…The terrestrial ecosystem in Antarctica is experiencing harsh environments, such as enhanced UV radiation, shortage of available water resources and low temperature [ 28 ]. In the past two decades, due to the destruction of the ozone layer hole, the surface of Antarctica has been continuously exposed to UV-B radiation [ 36 ]. From November to December in 2020, the highest UV irradiance of the Antarctic continent was recorded in the last 20 years at the northern part of the Antarctic Peninsula.…”

Stratospheric ozone, UV radiation, and climate interactions

“…Using observations from satellites between 1978 and 2020, a recent study [ 34 ] compared annual averages of the depth and area of the Antarctic ozone hole for early spring (1 September–15 October) and late spring (16 October–30 November). This analysis is of high relevance for assessing trends in UV radiation over Antarctica because UV radiation is generally much greater later in spring when the Sun is higher in the sky even though TCO is typically much lower earlier in spring.…”

Stratospheric ozone depletion in the Antarctic region triggers intense changes in sea salt aerosol geochemistry

“…Since the onset of stratospheric ozone depletion, the maximum has shifted to the spring season. Despite this change in time and intensity, previous work showed that actual UV-B levels in the summer season increased by approximately 15% when compared with the same period before the ozone depletion 7,8 . Since the Antarctic troposphere is now exposed to dramatically higher quantities of UV-B radiation, it is no longer in a "natural" state 8,9 .…”

“…Despite this change in time and intensity, previous work showed that actual UV-B levels in the summer season increased by approximately 15% when compared with the same period before the ozone depletion 7,8 . Since the Antarctic troposphere is now exposed to dramatically higher quantities of UV-B radiation, it is no longer in a "natural" state 8,9 . Among the impacts on the atmospheric chemistry by ozone hole and UV-B incidence, the investigation of sea salt aerosols plays a critical role, as it takes part in radiative processes at the maritime boundary layer 10,11 .…”