1159 / 2024-09-20 13:53:19

Leakage from the Deep Western Boundary Current around Greenland

DWBC, Eddy disturbance, Inertial separation

The Deep Western Boundary Current (DWBC) is the major component of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). Historically, the DWBC was considered as a stable and continuous current travelling southward along the topographic boundary of the Atlantic. However, recent observational and modeling studies have revealed leakiness of the DWBC in the Newfoundland Basin, with deep waters escaped from the boundary current and traveled southward via interior pathways, with potential impacts on the transport intensity, meridional continuity and temporal variability of the AMOC lower limb. In this study, we further identify DWBC leakage in the subpolar North Atlantic, where the deep water is newly formed and exported each year. Specifically, using 50 RAFOS floats (1800-2800 dbar) and 22 Argo floats (parking depths at 1500 and 2000 dbar), we find 19/72 floats escaped from the DWBC into the interior ocean around the southern tip of Greenland. In particular, 16 floats escaped upstream of the Eirik Ridge and some of their escape pathways closely follow contours of surface absolute dynamic topography. This suggests a potential role of mesoscale eddies in diverting the deep floats from the DWBC. In addition, 3 floats leaked from the boundary current at the Eirik Ridge corner, which is likely attributed to inertial separation. Further exploration on the strength and mechanism of the leakage will be conducted by simulating Lagrangian particles in a high-resolution ocean circulation model.