Topographic Effects on Seasonal Variations of the North Atlantic Deep Water Transport

Ocean circulation responds to seasonal and longer timescale changes in atmospheric forcing through the propagation of Rossby and boundary waves, which transmit pressure anomalies and influence geostrophic velocities along their pathways. Rossby waves are guided by potential vorticity isolines shaped by bathymetry. This study hypothesizes that seasonal velocity variability in the North Atlantic Ocean's deep water layer is primarily driven by wind stress and that its pattern and magnitude are strongly influenced by bathymetry. Analysis of satellite gravimetric observations, ocean state estimates, and wind-driven model simulations reveals that Ocean Bottom Pressure (OBP) and velocity in the deep water layer are significantly modulated by bathymetry, with pronounced variability near topographic features. These findings suggest that measurements of the Deep Western Boundary Current alone may be insufficiently to fully capture the net variability of the Atlantic Meridional Overturning Circulation (AMOC).