Decrease of summer tropospheric ozone concentrations in Antarctica

AS an oxidant and a precursor for other highly reactive oxidants, ozone plays an important role in tropospheric photochemistry. In the upper troposphere, ozone absorbs infrared radiation and is thus an effective greenhouse gas¹. Here we show that surface ozone concentrations at the South Pole in the austral summer decreased by 17% over the period 1976-90. Over the same period, solar irradiance at the South Pole in January and February decreased by 7% as a result of a 25% increase in cloudiness. We suggest that the trend in the summer ozone concentrations is caused by enhanced photochemical destruction of ozone in the lower troposphere caused by the increased penetration of ultraviolet radiation associated with stratospheric ozone depletion, coupled with enhanced transport of ozone-poor marine air from lower latitudes to the South Pole.