Mixing estimates from a large-scale hydrographic survey in the North Atlantic

A large-scale hydrographic survey from 2003 ( RV Meteor cruise M59/2) is used to map turbulent mixing by means of eddy diffusivities from finescale shear and strain in the subpolar North Atlantic, covering various hydrographic and bathymetric conditions. Results from the analysis indicate small (O(10(-5)) m(2) s(-1)) diffusivities below the Labrador Sea Water layer at mid-depth in the open ocean. Higher values exceeding 10(-4) m(2) s(-1) are found in the abyss close to rough topography and over the flanks of the Mid-Atlantic Ridge. The strongest mixing with diffusivities of 10(-3) m(2) s(-1) occurs in the Deep Western Boundary Current off Flemish Cap. The results of this study convey the need to map mixing globally from existing sets of CTD/LADCP data as well as its feasibility: the similarities and differences in mixing patterns as compared to other studies indicate that large scale patterns of small scale processes are still not well known and understood.