The Impact of North-South Shifts in the Sahel on North Atlantic Climate

Cool periods in the North Atlantic have been linked to hydrological changes over the Sahel region. It has been postulated that the Sahara-Sahel border shifted southwards during the last Heinrich event, which resulted in the semi-arid Sahel becoming more arid. This would drive changes in dust emission rates over North Africa. In fact proxy data indicates North Africa was dustier during the last Heinrich event than during the LGM. Recent analysis of CMIP5 models suggests the Western Sahel may become drier later this century. This may be analogous to past changes that have occurred in this region. Here we examine the implications of a southward shift in the Sahara-Sahel border in the Community Earth System Model version 1 (CESM1). Imposed changes in soil erodibility over the Sahel region results in greater dust emission rates and transport across the tropical Atlantic. Greater dust loading cools local sea surface temperatures and may have implications on the Atlantic Meridional Overturning Circulation. Our idealized runs can be used to understand how changes in dust forced climate change during the past as well as how potential future hydrological changes over the western Sahel can impact Atlantic climate.