Ocean controls on the variability of the Hadley Cell over the last 2000 years

Abstract

In the Tropics, the Hadley circulation 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). The position of the ITCZ over the ocean is locked to the sea surface temperature patterns and the net northward heat transport in the Atlantic ocean, by the meridional overturning circulation (AMOC), and atmospheric redistribution of this heat leads the average ITCZ position to be displaced north of the equator. Therefore, changes in surface temperature patterns in the tropical region may impact precipitation in the surrounding continents, via their influence on the Hadley Circulation and the monsoon system. In addition to SST variability, other factors such as greenhouse gases (GHG) concentration, stratospheric ozone depletion and pollution have been identified as drivers of a poleward expansion of the Hadley Cell in the last decades. Considering the impacts of ocean-atmosphere coupling on atmospheric circulation and precipitation in the Tropical Atlantic region, as well as the sensitivity to both natural and anthropogenic external forcings, this project aims to study the variability of the Hadley Cell in connection with the Tropical Atlantic modes of sea surface temperature variability and the tropical hydroclimate during the historical period (1850-2014) of CMIP6 simulations. We will investigate the mechanisms driving this variability considering both the natural and anthropogenic forcing (greenhouse gases, stratospheric ozone and tropospheric aerosols). We will rely on CMIP6 endorsed simulations, on ensemble simulations of the IPSL-CM6A-VLR model and reanalyses and observations when possible. This project will be led under the supervision of Dr. Myriam Khodri of the LOCEAN-IPSL Laboratory at Sorbonne University. (AU)