Lanes of Lightning

Lightning strikes about 125 million times per year, mostly over land. But geophysicist Joel Thornton found a surprising number of strikes at sea over shipping lanes. Shipping lanes are the ocean highways that cargo ships use to transport goods. Working with his team at the University of Washington, Thornton found that more lightning strikes hit two major shipping lanes than the surrounding ocean. But the ships weren’t attracting the lightning—they were causing it!

Lightning is the discharge of electrical energy in clouds. When ice crystals collide, it creates electricity. For tiny water droplets in the clouds to become ice instead of rain, they need to latch on to particles like dust or leftovers of burned fuel. The ships’ exhaust adds more solid particles into the clouds. More ice crystals means more lightning.