El Niño is a recurring climate pattern characterized by warmer than usual ocean temperatures in the equatorial Pacific. Two back-to-back 3-D visualizations track the changes in ocean temperatures and currents, respectively, throughout the life cycle of the 2015-2016 El Niño event, chronicling its inception in early 2015 to its dissipation by April 2016. Blue regions represent colder and red regions warmer temperatures when compared with normal conditions.
Under normal conditions, equatorial trade winds in the Pacific Ocean blow from east to west, causing warm water to pile up in the Western Pacific, while also causing an upwelling—the rise of deep, cool water to the surface—in the Eastern Pacific. During an El Niño, trade winds weaken or, as with this latest event, sometimes reverse course and blow from west to east. As a result, the warm surface water sloshes east along the equator from the Western Pacific and temporarily predominates in the Central and Eastern Pacific Ocean. At that same time, cooler water slowly migrates westward just off the equator in the Western Pacific.
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