Investigating the Role of the Tibetan Plateau in the Formation of Atlantic Meridional Overturning Circulation

Abstract

AbstractThe Tibetan Plateau (TP) over the Eurasian continent has significant effects on both regional and global climate. It can even affect the remote Atlantic meridional overturning circulation (AMOC), as shown in this study. Through coupled modeling experiments, we demonstrate that removing the TP immediately weakens the meridional wind over East Asia, resulting in stronger westerlies in the midlatitudes. The stronger westerlies enhance the southward Ekman flow and surface latent and sensible heat losses in the subpolar North Atlantic, cooling the surface ocean and leading to stronger North Atlantic deep-water formation and stronger AMOC during the first few decades after the TP removal. At the same time, accompanying the weakened trade winds in the tropical Pacific, more moisture is transported from the tropical Pacific to the North Atlantic, freshening the surface ocean and triggering a weakening of the AMOC. The AMOC weakening in turn results in southward expansion and melting of sea ice, providing more freshwater to the North Atlantic, which furthers the weakening of the AMOC. The positive feedback between the AMOC and sea ice eventually leads to AMOC shutdown. We illustrate that there would be no AMOC without the TP. These results call for a revisiting of how ocean circulation and global climate may have responded to the TP uplift and other tectonic changes on the geological time scale.