Biological Impacts of Seasonal Ozone Depletion

Abstract

Since the mid-1970s there has been a marked reduction in the concentration of Antarctic stratospheric ozone during springtime (Fig. 1). These observations were made originally by ground-based instruments but more recently satellite observations have been used to gain a broader picture of the so-called Antarctic ozone hole which develops in September and dissipates in November (Stolarski et al. 1986). The processes involved in the formation and breakup of the ozone hole are discussed by Rycroft (this Vol.). Following the breakdown of the polar vortex, ozone depleted stratospheric air is transported to midlatitudes (Atkinson et al. 1989). A consequence of a reduction in stratospheric ozone concentration is an increase in the amount of ultraviolet (UV) radiation reaching the surface of the Earth. The springtime UV irradiance at Antarctic coastal sites has been found to be as high or higher than at the summer solstice (Frederick and Snell 1988; Fig. 2). As well as an overall increase in the total amount of incident UV, reduced stratospheric ozone concentration leads to an increase in the amount of short wavelength UV (Fig. 3). The biological impact of UV irradiation is extremely wavelength dependent (Caldwell 1981; Smith and Baker 1989).