Influence of Interhemispheric Asymmetry in Volcanic Forcing on ITCZ Location and Oxygen Isotope Distribution

Abstract:

Volcanic eruptions are a dominant source of natural forced variability during the Common Era. Although transient, eruptions strongly cool the planet through the liberation of sulfur gases that enter the stratosphere (converting to sulfate aerosol) and scatter sunlight. In particular, such events source the largest amplitude radiative forcings that perturb the terrestrial climate during the Last Millennium. Previous studies have highlighted the global climate impact of large volcanic events, including the role of latitude and time-of-year of a given eruption. Here, we focus on the influence of hemispheric asymmetry in Aerosol Optical Depth (AOD) and its projection onto the tropical hydrologic cycle. This is assessed using a suite of simulations from a fully coupled isotope-enabled General Circulation Model (NASA GISS ModelE2-R) run from 850-2005 CE. This study builds upon prior work that demonstrate the role of inter-hemispheric forcing gradients on Intertropical Convergence Zone (ITCZ) location. In addition to unveiling the physical mechanisms that alter tropical hydroclimate, we highlight the anticipated tropical oxygen isotope distribution following large eruptions. Thus, through the vehicle of an isotope-enabled model, we formulate a potentially falsifiable prediction for how volcanic forcing may manifest itself in high-resolution proxies across the tropics.