| Summary: | It has been noted that while major volcanic eruptions in the tropics lead to a global distribution of stratospheric aerosol, the distribution is not necessarily symmetric between the Northern and Southern Hemispheres. Furthermore, ice-core records of volcanic events from the Greenland and Antarctic ice sheets are often in poor agreement, with the best known example being that of the Toba eruption of ~74 ka B.P., which has a strong signal in the Greenland ice cores, but no identified signal in Antarctic ice core records. Using simulations with the MAECHAM5-HAM general circulation model including detailed aerosol microphysics, we examine how the hemispheric asymmetry of volcanic aerosol loading, and of the deposition of sulfate to the surface, depends on the season and magnitude of eruption. A number of paleo-eruptions in the Central American Volcanic Arc (CAVA) are simulated, with different SO2 emission strengths (ranging from 17 to 700 Mt SO2) estimated from field measurements. We show that heating of volcanic aerosols leads to atmospheric circulation changes, affecting the global aerosol transport. Our results indicate that for extremely large volcanic eruptions, such anomalous atmospheric circulation patterns can lead to very large asymmetries in stratospheric aerosol loading and sulfate deposition to the polar ice sheets. This work could be useful in better interpreting volcanic signals in paleo-ice core data and improving the accuracy of estimated aerosol optical depth data sets used in the model simulation of past climate.
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