Oceanographers use the term “differential diffusion” to express a greater value of bulk turbulent diffusivity of temperature within the ocean than the value of bulk diffusivity of salinity, the ratio quantified by Lewis number. Investigation of horizontal thermohaline convection at Prandtl number 1 and infinity over the range $1<Le\le 10$ reveals a variety of new flow patterns. The chamber has a linearly changing temperature T and salinity S along the top extending from the cold, fresh “polar” end to the hot, salty “tropics” end. It has an aspect ratio of 8 and sides and bottom are insulated and impermeable. Five transition flow patterns occur with little hysteresis for a fixed salinity Rayleigh number Ras of order 10⁵ as Rayleigh number Ra changes from 3.2 × 10⁶ down to 1. They are: 1. A steady T-cell with sinking at the cold end flowing into a bottom flow that feeds up into a top thermal boundary layer. 2. Salty blobs in the boundary layer that amplify and move from the hot to cold end. Each cold end arrival triggers a sudden increase in overturning velocity. 3. A “stripes” pattern where top to bottom cells (alternating T and S cells) move toward the cold end. 4. An S-cell that is a mirror image of the T-cell near the top along with small T-cells lying at the bottom that move toward the cold end 5. A steady S-cell. Each pattern has a distinct volumetric signature in a T-S diagram. Ranges of Ra with various patterns are sizeable at Ras=7.5 × 10⁵ if Le >4/3 but insensitive to Pr. Balanced convection at Ra = Ras >10⁶ adopts a large unsteady supercell containing smaller T and S cells. Exact ranges of the supercell are unknown. Since differential diffusion produces a large collection of flows compared to thermal convection alone, it might produce unexpected new results if added into numerical models of the ocean.

海洋学家使用术语“差分扩散”来表示海洋内温度的体积湍流扩散率值大于盐度的体积扩散率值，该比率由路易斯数量化。普朗特 1 号和无穷远处的水平温盐对流研究$1<\mathrm{大号}e\le 10$揭示了多种新的流动模式。腔室的温度T和盐度S沿顶部从寒冷、新鲜的“极地”端延伸到炎热、咸味的“热带”端呈线性变化。它的纵横比为 8，侧面和底部是绝缘且不透水的。对于10 ⁵阶的固定盐度瑞利数Ras ，当瑞利数Ra从 3.2 × 10 ^{6变化时，出现五种过渡流动模式，几乎没有滞后}下降到 1。它们是： 1. 一个稳定的 T 细胞，在冷端下沉，流入底部流，向上流入顶部热边界层。2. 边界层中的咸水团从热端向冷端放大并移动。每次冷端到达都会触发倾覆速度的突然增加。3. “条纹”模式，其中从上到下的细胞（交替的T和S细胞）向冷端移动。4. 一个 S 细胞，它是靠近顶部的 T 细胞的镜像，以及位于底部的小T细胞，它们向冷端移动 5. 一个稳定的 S 细胞。每个模式在TS图中都有不同的体积特征。具有各种模式的Ra范围在Ras处相当大=7.5 × 10 ⁵如果Le >4/3 但对Pr不敏感。Ra  =  Ras >10 ⁶处的平衡对流采用包含较小T和S单元的大型非定常超级单元。超级单体的确切范围是未知的。由于与单独的热对流相比，差分扩散会产生大量流动，因此如果将其添加到海洋数值模型中，它可能会产生意想不到的新结果。