Fast teleconnections to the tropical Atlantic sector from Atlantic thermohaline adjustment

Abstract

We examine the first decade of adjustment of the North Atlantic climate following an abrupt freshening of the high North Atlantic and resulting slowdown of the Atlantic meridional overturning circulation (AMOC) in a coupled model, with reference to previously proposed teleconnection mechanisms. After an initial ocean‐driven cooling at the subtropical‐subpolar gyre boundary, subsequent equatorward progression is dominated by an atmosphere‐surface ocean mechanism driving evaporative cooling in the tropical North Atlantic, and resulting in an anomalous southward ITCZ displacement by year 2. The tropical cooling is countered by fast ocean baroclinic adjustment to the reduced overturning that increases the volume of tropical surface waters, as well as ocean circulation changes to the increased northeasterly trades. However, it is the atmosphere‐surface ocean teleconnection that explains the hemispheric asymmetric nature of the tropical Atlantic surface climate impact to AMOC slowdown, underlining its crucial importance in high‐to‐low latitude teleconnections.