PNNL

Abstract

Observational evidence and climate model experiments suggest a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) since the mid-1990s. In addition to increased greenhouse gases, the declined anthropogenic aerosols (AAs) over North America and Europe are believed to contribute to the AMOC slowdown. Asian AAs continue to increase but the associated impact is unclear. Using ensembles of climate simulations, here we show that the radiative cooling resulting from increased Asian AAs paradoxically drives an AMOC reduction. The increased AAs over Asia generate circumglobal stationary Rossby waves, which shift the jet stream southward and weaken the subpolar North Atlantic westerlies. Consequently, reduced transport of cold air from North America hinders water mass transformation in the Labrador Sea and thus contributes to the AMOC slowdown. Thus, reducing emissions of Asian AAs will not only lower local air pollution, but also help stabilize the AMOC.