After helping stoke record heat in 2023 and drenching major swaths of the United States this winter, the current El Ni?o is losing steam this spring. Scientists have observed another way that the climate phenomenon can leave its mark on the planet: altering the chemistry of coastal waters. A team at NASA’s Jet Propulsion Laboratory in Southern California used satellite observations to track the dissolved salt content, or salinity , of the global ocean surface for a decade, from 2011...