Cooperative Institute for Research in Environmental Sciences

Twenty-five years of ozonesonde measurements at South Pole: An assessment of changing loss rates

Birgit Hassler (1,2), John S. Daniel (2), Bryan J. Johnson (3), Susan Solomon (4), Samuel J. Oltmans (1)

(1) CIRES (2) NOAA ESRL CSD (3) NOAA ESRL GMD (4) MIT

In 2010, 25 years of continuous, year-round ozone soundings at South Pole station, Antarctica, were completed. These measurements provide unique information about ozone depletion in the polar stratosphere at high vertical resolution. We analyzed these ozone soundings to learn more about the onset time of the seasonal ozone depletion, the observed loss rates, and their changes since the measurement series began. During the last 25 years the seasonal onset of ozone loss at South Pole has moved forward significantly. The fastest highest loss rates occur between the end of August and end of September near 50 hPa to 30 hPa. Loss rates at these pressure levels increased from the late 1980s to the late 1990s and have remained roughly stable since then. To estimate a time frame when a reduction in ozone loss rates will be observable outside the range of annual variability at the South Pole, we scale the estimated loss rates to the future projected concentrations of equivalent effective stratospheric chlorine (EESC). We project that ozone loss rates will first be significantly reduced between 2017 and 2021.