Green Sahara influence on South Atlantic dynamics: insights from NASA GISS simulations

The Mid-Holocene experiment is a well known paleoclimate simulation, typically represented by greenhouse gases (GHG) and orbital forcings. In this study we examine how including other Earth-system components in mid-Holocene simulations, such as the vegetated Green Sahara and expansive African mega-lakes, modulate the South Atlantic’s dynamics. Addressing a gap in understanding the relationship between terrestrial and oceanic systems, we investigate how these additional features influence sea surface temperatures, salinity, circulation patterns and atmospheric dynamics in the South Atlantic. Employing NASA GISS E21-G global climate model experiments, the study compares these effects to a standard mid-Holocene scenario using only GHG and orbital forcing. Key findings include a decrease in sea surface temperatures and salinity due to increased freshwater input originating from enhanced precipitation and African mega-lakes. This leads to a weakened South Atlantic Meridional Overturning Circulation. Winds are modified in response to changes in Green Sahara vegetation and the addition of mega-lakes, which alter the pressure distribution. These findings underscore the influential role of terrestrial changes on the South Atlantic’s climate, contributing to our understanding of global climate impacts and the potential implications of environmental changes on marine and atmospheric systems.