At nearly 10 times saltier than the ocean, the Dead Sea is one of the saltiest places on Earth, and since 1979, scientists have observed it growing even saltier as snow-like salt precipitates to the bottom of the lake. Numerical simulations have now confirmed that this salt-fall is the result of double-diffusive salt fingers.
Here’s how the mechanism works: the upper layer of the lake is made up of warmer, saltier water covering deeper, colder waters. As the sun evaporates water near the surface, what’s left behind becomes saltier and heavier. Tiny pockets of this warm, salty water sink into colder regions and rapidly cool. The heat can move a lot more quickly than the salt, though, and since cold water cannot hold as much salt as warmer water, some of the salt precipitates out. That forms the falling crystals scientists observe sinking to the bottom of the lake. (Image and research credit: R. Ouillon et al., source; via Physics World; submitted by Kam-Yung Soh)