Using data from several satellite altimeters, a finer picture of the ever-changing height of the oceans is revealed. Swirling currents called eddies pepper the global ocean. Like small pock-marks in sea surface height, these eddies are found in every major ocean basin. Near the Equator, the eddies give way to fast moving features called Kelvin Waves. When they build up in the Pacific, these waves can usher in a phenomenon known as El Nino, which happens when warm water and high sea levels move into the Eastern Pacific along the Equator. Occurring every 3 to 4 years, El Nino can have a big impact on weather across the globe, brining extra rainfall to the American Southwest and even affecting hurricanes in the Atlantic Oceans.