The Role of Calbuco Volcanic Aerosols on 2015 South Polar Ozone Depletion

The Southern Hemisphere Antarctic stratosphere experienced two noteworthy events in 2015: a record-large Antarctic ozone hole in October and November, and a significant injection of sulfur from the Calbuco volcanic eruption in Chile in April. Here, Calbuco's influence on stratospheric ozone depletion in austral spring 2015 is estimated using a broad range of observations and a stratospheric chemistry-climate model. Ozonesondes at four Antarctic stations, as well as data from the Microwave Limb Sounder (MLS) are analyzed. Simulations that account for volcanic effects from the Whole Atmosphere Community Climate Model (WACCM) in a specified dynamics setup are also employed. The transport of Calbuco stratospheric aerosols to high southern latitudes is captured using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data, where high 532 nm backscatter values are seen as far as 70ºS during October and November due to liquid binary sulfate particles (in broad agreement with WACCM). Comparison to ozone data suggests that aerosols played a major role in expanding the ozone hole, especially at higher pressure levels between 150 and 100 hPa. Ozonesonde vertical ozone profiles from the sites of Syowa, South Pole, and Neumayer, with Davis on par, display the lowest individual October or November measurements at 150 hPa since the Pinatubo years of 1992–1993. The analysis suggests that under the cold and therefore ideal conditions for ozone depletion, excess aerosols in the stratosphere during 2015 greatly enhanced austral ozone depletion, particularly at lower latitudes (55–70°S) where liquid binary sulfate aerosols have a large influence.