A parameterization for the spatial pattern of the eddy induced thickness advection parameter estimated<br />from a dynamically consistent data assimilation procedure is presented. Values of the thickness advection<br />parameter are predominantly negative (positive) over seamounts, and positive (negative) over the<br />deep ocean in the southern (northern) hemisphere along strong currents; its magnitude is large at high<br />latitudes but low in the tropical regions. Those characteristics motivate a parameterization based on the<br />Coriolis parameter, the bottom depth and an eddy length scale. As a parameterization for an eddy streamfunction,<br />the associated bolus velocities advect density anti-cyclonically (cyclonically) around seamounts<br />(troughs). Although the parameterization has the same form as Holloway’s streamfunction for the Neptune<br />effect, and is also related to eddy–topography interactions, Holloway’s streamfunction is in contrast<br />applied to the momentum equation. The parameterization is independently confirmed by the flux-mean<br />gradient relation from the output of a high resolution model. The effect of the proposed scheme is investigated<br />using a channel model with idealized bottom topographies and a global ocean circulation model<br />with realistic bottom topography. In agreement with the high resolution model, our scheme generates<br />cold (warm) domes and cyclonic circulations over seamounts (troughs), which is consistent with the<br />eddy movement in presence of the topographic b effect. This provides a different mechanism for<br />eddy–topography interaction than the Neptune effect, which generates circulations of opposing sign.

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