The DWBC has traditionally been considered the sole conduit for the lower limb of the AMOC.
Essentially, the compilation of studies over the past decade yields a description of LSW production whereby the properties and transport variability within the DWBC are not a sole function of deep-water formation.
In addition to this signature of deep convection, the survey also shows the familiar features of the warm and saline Irminger Current on the eastern and western boundaries of the basin, as well as the cold, dense, and oxygen-rich DSOW carried along the East Greenland slope by the DWBC. A new feature, however, is the signature of stirring between the interior waters (high in oxygen) and boundary current water (low in oxygen) that appears over the western flank of the Mid-Atlantic Ridge.
"The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC
, contrary to previous thinking," their report concluded.
Since the upper portion of the DWBC extends to shallower depths than the separating Gulf Stream, one question concerns how this upper DWBC can survive its crossing and progress past the Gulf Stream.
The CFC map and water parcel trajectories near the 3,000-meter level show that the DWBC passes beneath the Gulf Stream with minimal difficulty and, as the bottom figure overleaf shows, there is also a significant inflow of water from offshore.
In particular, a change in the Gulf Stream's angle of separation causes a change in the trajectory of the DWBC, while an increase in Gulf Stream transport leads to a weakening of the DWBC.