CoAuthors

Magnim Gnamah (LOCEAN-IPSL, Sorbonne Université, France); Siny Ndoye (LPAOSF-ESP-UCAD, Senegal)

Vertical velocities in the ocean are generally too weak to be measured, especially at monthly to longer time-scales. In particular, that is the case of the vertical movements associated to the large-scale relatively slow dynamics. This prevents any accurate assessment of the thermohaline circulation and ventilation (mass, heat, oxygen and other tracer fluxes). In this work, we compute the three-dimensional time-mean vertical velocities w of an Atlantic basin simulation, using the density field and the linear vorticity balance (LVB), and compare it to the model w. The validity of the LVB and the errors of the estimated velocities are quantified using the simulation as the reference.
We show that large regions of the basin are dominated by LVB dynamics, within the tropical, subtropical, and subpolar gyres, at various depth range, depending on spatial scale considered. The w estimated field is accordingly accurate in many regions to first order, especially away from boundaries. The method offers a way to interpret vertical movements at various depths in function of the well-constrained horizontal geostrophic flow.