Henry Stommel's 1961 article "Thermohaline Convection with Two Stable Regimes of Flow" explores the dynamics of free convection between two interconnected reservoirs, driven by density differences due to heat and salt transfer. The density of seawater is influenced by surface heating and cooling, which alter temperature, and precipitation and evaporation, which affect salinity. These processes often work in opposition, leading to complex density patterns in oceanic regions. Stommel models this phenomenon using a simple system: a vessel of water with uniform temperature and salinity, separated by porous walls that allow heat and salt transfer. The equations describing the system are simplified and non-dimensionalized, showing that the density anomaly approaches its asymptotic value more quickly for temperature than for salinity. He then extends the model to a more complex scenario involving two vessels connected by a capillary tube, where the flow rate depends on the density difference. The analysis reveals that under certain conditions, the system can exhibit two stable regimes of flow: one dominated by temperature differences and another by salinity differences. This suggests that similar phenomena might occur in natural systems, such as oceanic circulation, and raises questions about the potential for abrupt changes in climate due to perturbations in these systems. The article concludes with a discussion on the stability of equilibrium points and the conditions under which different regimes can coexist.Henry Stommel's 1961 article "Thermohaline Convection with Two Stable Regimes of Flow" explores the dynamics of free convection between two interconnected reservoirs, driven by density differences due to heat and salt transfer. The density of seawater is influenced by surface heating and cooling, which alter temperature, and precipitation and evaporation, which affect salinity. These processes often work in opposition, leading to complex density patterns in oceanic regions. Stommel models this phenomenon using a simple system: a vessel of water with uniform temperature and salinity, separated by porous walls that allow heat and salt transfer. The equations describing the system are simplified and non-dimensionalized, showing that the density anomaly approaches its asymptotic value more quickly for temperature than for salinity. He then extends the model to a more complex scenario involving two vessels connected by a capillary tube, where the flow rate depends on the density difference. The analysis reveals that under certain conditions, the system can exhibit two stable regimes of flow: one dominated by temperature differences and another by salinity differences. This suggests that similar phenomena might occur in natural systems, such as oceanic circulation, and raises questions about the potential for abrupt changes in climate due to perturbations in these systems. The article concludes with a discussion on the stability of equilibrium points and the conditions under which different regimes can coexist.