Most lightning strikes happen over land. These bolts of electricity are much rarer over the ocean. Recently, scientists studied data from more than 75,000 thunderstorms and discovered an explanation for the ocean’s lack of lightning: sea salt.
Lightning forms when water droplets latch onto super-tiny particles inside clouds and freeze, forming ice crystals. The crystals collide and build up electric charges. Over the ocean, the air contains large particles of sea salt. They attract more water than the smaller particles found over land. As a result, heavier droplets form. These droplets fall as rain before they can freeze into ice crystals and build charge in the cloud. This reduces lightning formation by as much as 90 percent.
“I didn’t expect the effect to be so strong,” says Daniel Rosenfeld, an atmospheric scientist at the Hebrew University of Jerusalem in Israel. “This was really striking to me.”