Wind-steered Eastern Pathway of the Atlantic Meridional Overturning Circulation

The spreading pathway of the North Atlantic Deep Water, which is the lower limb of the Atlantic Meridional Overturning Circulation (AMOC), determines how climate change signals are transported throughout the global ocean. The North Atlantic Deep Water is suggested to be transported from the subpolar Atlantic to the subtropics in the western basin by the Deep Western Boundary Current and the eddy-driven interior pathway west of the Mid-Atlantic Ridge. However, much less attention has been paid to AMOC cross-gyre transport in the eastern basin. Here, combining hydrographic observations and reanalysis, we identify a robust mid-depth Eastern Pathway located east of the Mid-Atlantic Ridge, which is further corroborated by model simulations with various resolutions, including eddy-resolving simulations. The Eastern Pathway accounts for half of the North Atlantic Deep Water transport across the intergyre boundary. Sensitivity experiments suggest that the mid-depth Eastern Pathway is formed by basin-scale ocean circulation dynamics due to wind steering on the intergyre communicating window instead of bottom topography. Our results provide a model for the AMOC pathway and call for further investigations on the climate response and variabilities associated with different AMOC pathways. About half of the lower limb of the Atlantic Meridional Overturning Circulation flows east of the Mid-Atlantic Ridge, a pathway steered by wind and not bottom topography, according to hydrographic data, reanalysis and model simulations.