El Niño, linked to warmer-than-average ocean temperatures in the equatorial Pacific, can lead to more rain and snowfall than normal in the southwestern U.S., as well as drought in Indonesia. The team found that salinity is at least 30 times more variable in these dynamic zones near coasts than in the open ocean. The link between rain, rivers, and salt is especially pronounced at the mouths of large river systems such as the Mississippi and Amazon, where freshwater plumes can be mapped from space as they gush into the ocean.