Hadley Cell Variability during the Last Millenium and response to volcanism in the PMIP4/CMIP6 models

In the Tropics, the Hadley Cell plays a key role in controlling precipitation patterns, since it is related to the position of the ITCZ, which is also a main component of the South America Monsoon System (SAMS). Several studies have documented a poleward expansion of the Hadley Cell over the historical period and a shift in the position of its subsiding branches and the expansion of the subtropical dry zones. This widening has largely been attributed to anthropogenic forcing, such as greenhouse gases (GHG) and stratospheric ozone depletion. However, prior to the industrial period, the extent of the Hadley Cell is dominated by internal variability and the radiative effects of volcanic eruptions. Understanding this natural variability is key to better predict the possible combined effects with anthropogenic external forcing. Thus, in this study we to investigate the variability of the Hadley Cell during the Last Millennium and its response to volcanic eruptions. We rely on the simulations of the Last Millennium provided by the Paleoclimate Modeling Intercomparison Project (PMIP4) contribution to the Climate Model Intercomparison Project phase 6 (CMIP6).