The Giant Bathtub in the Pacific (How El Niño Works)

Let’s think of the Pacific Ocean as a giant bathtub. Normally, strong winds called trade winds blow across this tub from east to west, pushing warm water toward Asia like Indonesia and the Philippines. This is just like blowing across the top of a full bathtub to move the warm water from one side to the other. In this case, from the side of the Americas to Asia.

Because the warm water gets pushed away, cold water must rise from the deep ocean to take its place along the coast of South America. Scientists call this rising water upwelling. This deep water is cold and full of healthy nutrients. It keeps the global climate balanced and helps local fishermen catch plenty of fish.

Every few years, this normal cycle changes. Centuries ago, fishermen in South America noticed the ocean water would suddenly get very warm in their region. This usually happened around Christmas time. Because of the holidays, they named the warm current “El Niño”. In Spanish, this name means “the boy” or “Christ Child”.

During El Niño, those steady trade winds weaken. Sometimes, they even blow backward in the opposite direction. With no wind to hold it back, the giant pile of warm water pushes back eastward toward the Americas. Now, the giant bathtub is tipped the other way. Instead of the hot climate normally headed towards Asia, it is in the Americas.

This water movement might seem like a small thing, but the Pacific Ocean is huge. It actually covers a third of our entire planet. Shifting that much heat to a new spot changes the air above the water. This movement bends the great rivers of wind in the sky, which scientists call jet streams. When these jet streams move, they carry rain clouds away from Asia. This flips global weather upside down, bringing floods to dry places and droughts to wet places.

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This article is the first of a series.