View article

A scale for the thickness of layers in regular “diffusive”‐type thermohaline staircases, derived from dimensional analysis, is found to collapse oceanic data. Combining this scale with laboratory‐derived double‐diffusive flux laws, we formulate effective diffusivities for salt, heat, and density. The diffusivities depend on the Turner number R_ρ, but are independent of the Brunt‐Vaisala frequency. For R_ρ near 1 the diffusivities for salt and heat are approximately equal (≃10⁻⁴ m² s⁻¹). They decrease roughly as R_ρ⁻⁴ and R_ρ⁻², respectively, over the oceanic range 1≤R_ρ≤10.