Southern Annular Mode response to volcanic eruptions: implications for ice core proxies

• Main Authors: Toohey, Matthew, Krüger, Kirstin, Zander, Stefanie, Niemeier, U., Timmreck, C.
• Format: Conference Object
• Language: English
• Published: 2011
• Subjects: Antarctic; The Antarctic; Antarc*; ice core; Ice Sheet; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/12532/; https://oceanrep.geomar.de/id/eprint/12532/1/FB1_me_mtoohey_inqua2010.pdf

Large tropical volcanic eruptions have been observed to have a significant influence on the large-scale circulation patterns of the Northern Hemisphere, through mechanisms related to the radiative effects of the sulfate aerosols resulting from the volcanic injection of sulfur dioxide into the stratosphere. While no such volcanically induced anomalies in Southern Hemisphere circulation have yet been observed, we find that in general circulation model simulations, eruptions with sulfur dioxide injections larger than that of the 1991 Mt. Pinatubo eruption do result in significant circulation changes in the SH, specifically an enhanced positive phase of the Southern Annular Mode (SAM). We explore the mechanisms for such a SAM response, as well as the corresponding changes in SH temperature, sea ice and precipitation. We also explore how the anomalously strong zonal winds characteristic of the positive SAM regime affect the rate of sulfate deposition to the Antarctic ice-sheet. We suggest that the use of ice-core sulfate records as a proxy for past volcanic activity may benefit from including knowledge of, or better assumptions regarding the changes in large scale atmospheric circulation after large tropical eruptions.