On the Variability of the DWBC Transport Between 26.5°N and 16°N in an Eddy‐Rich Ocean Model

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Schulzki, Tobias, Getzlaff, Klaus, Biastoch, Arne
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: North Atlantic Deep Water; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/52715/; https://oceanrep.geomar.de/id/eprint/52715/1/2021JC017372.pdf; https://doi.org/10.1029/2021JC017372

The southward flow of North Atlantic Deep Water makes up the major component of the deepwater limb of the Atlantic Meridional Overturning Circulation (AMOC). In the subtropical North Atlantic, it's flow is concentrated along the continental slope, forming a coherent Deep Western Boundary Current (DWBC). Both, observations and models show a high variability of the flow in this region. Here we use an eddy-rich ocean model to show that this variability is mainly caused by eddies and meanders. Their formation process involves an important contribution from energy transfer by barotropic instability. They occur along the entire DWBC pathway and introduce several recirculation gyres that result in a decorrelation of the DWBC transport at 26.5°N and 16°N, despite the fact that a considerable mean transport of 20 Sv connects the two latitudes. Water in the DWBC at 26.5°N is partly returned northward. Because the amount of water returned depends on the DWBC transport itself, a stronger DWBC does not necessarily lead to an increased amount of water that reaches 16°N. Along the pathway to 16°N, the transport signal is altered by a broad and temporally variable transit time distribution. Thus, advection in the DWBC cannot account for coherent AMOC changes on interannual timescales seen in the model.