Pacific Shifts: El Niño and La Niña Explained Quiz

Under neutral conditions, Trade Winds blow East to West, pushing warm water toward Asia. During El Niño, these winds weaken, allowing that warm water to "slosh" back toward South America, disrupting global weather.

During La Niña, the Trade Winds become unusually strong. This pushes even more warm water West and causes an intense rise of cold water (upwelling) along the coast of South America.

Upwelling is vital for marine life and fishing industries. During El Niño, the layer of warm water becomes so thick that it suppresses upwelling, leading to a collapse in fish populations off the coast of Peru.

El Niño shifts the "rain machine" of the Pacific. While the eastern Pacific gets flooded, the western Pacific (Asia/Australia) suffers from dry conditions. Interestingly, El Niño usually creates wind shear that reduces Atlantic hurricanes but increases them in the Pacific.

The depth of the thermocline changes during ENSO cycles. In El Niño, the thermocline flattens out and gets deeper in the East; in La Niña, it tilts steeply, rising closer to the surface in the East.

These events are irregular but usually occur every 2 to 7 years. They are not perfectly predictable, which is why scientists monitor sea surface temperatures and wind speeds constantly.

ENSO stands for El Niño-Southern Oscillation. It reminds us that this isn't just an ocean problem; it is a "coupled" system where the ocean and the atmosphere constantly push and pull on each other.

Sea level rises where the water is warm (thermal expansion). Scientists use satellites to see these "hills" of warm water and buoy arrays (like the TAO array) to measure temperatures below the surface.

In neutral years, air rises over the warm western Pacific (rain) and sinks over the cool eastern Pacific (dry). El Niño breaks this loop by moving the rising air (and the storms) to the center or east of the ocean.

La Niña reduces vertical wind shear in the Atlantic. Without strong winds "chopping off" the tops of developing storms, hurricanes can grow larger and more frequent.

Because the warming of the ocean often reached its peak around late December, fishermen named it "The Boy Child" (referring to Christmas).

La Niña pushes the jet stream North. This brings cold, moist air to the Northern US and Canada while leaving the Southern states stuck in a dry, warm pattern.

A teleconnection is like a "domino effect." A change in the Pacific Ocean creates a ripple effect in the atmosphere that can change the weather in Africa, North America, and beyond.

Corals are very sensitive to heat. When the "warm pool" of water stays over a reef for too long during an El Niño, the corals become stressed and eject the algae living in their tissues, turning white and often dying.

Neutral conditions are the "baseline." Scientists look for deviations from this baseline (usually a change of 0.5 degrees Celsius or more) to officially declare an El Niño or La Niña event.