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Place 03 · The Galápagos · Chapter 4 of 7
When the Water Goes Warm
Every few years the wind across the Pacific gives up, the cold water around the Galápagos vanishes, and the penguins start to starve.
About 15 minutes · 1 video · 1 live map · 2 quick activities
Start here
Christmas, but warm
Fishermen in Peru have known it for generations: some years, around Christmas, the cold sea turns warm and the fish disappear. They called it El Niño, the Christ child. We now know it is the whole Pacific changing gear, and after the two biggest El Niños of the last century, 1982–83 and 1997–98, the Galápagos lost most of its penguins.
Watch this
See it move
NOAA SciJinks — What is El Niño? Two and a half minutes of NOAA explaining how one tired wind warms half an ocean.
While you watch, look for
- Which way the trade winds normally push the warm surface water
- Where the warm water goes when those winds weaken
- Something you did not expect. Hold onto it.
The short version
Three things going on here
The normal year
The wind piles up warmth
Normally the trade winds blow west along the equator and pile warm surface water up near Indonesia, where the sea stands about half a meter higher and about 8 °C warmer than off South America. That heap is the warm pool. In the east the thermocline sits close to the surface, so cold water wells up easily.
The switch
The wind lets go
In an El Niño year the trade winds weaken, and sometimes even reverse. The warm pool sloshes back east, the thermocline in the east sinks deeper, and the rain follows the warm water, flooding Peru while Indonesia and Australia dry out. The air joins in with a seesaw of air pressure across the Pacific called the Southern Oscillation.
The cost
Warm water, empty sea
What upwelling is left at the Galápagos now lifts warm, nutrient-poor water from above the sunken thermocline, and the algae and fish fade away. After 1982–83 the Galápagos penguins fell by 77%, and after 1997–98 by 65%. In 1997–98 up to 90% of the marine iguanas died on some islands, starved of the seaweed they graze.
Photos: Landiva Weber, Josh Sorenson, Diego F. Parra / Pexels
Play with it
Is the Pacific running warm right now?
This live map colors the sea by how much warmer (red) or colder (blue) it is than normal today. Click the water around the Galápagos, then follow the equator west toward the middle of the Pacific; in mid-2026 an El Niño was building there.
Live map: earth.nullschool.net by Cameron Beccario, using NOAA and other public data.
Two questions to answer while you are in there
- Is the sea around the Galápagos warmer or colder than normal today, and by how much?
- Along the equator west of South America, do you see a long tongue of red or of blue? Is the Pacific leaning toward El Niño or La Niña right now?
Try it yourself
Check yourself
Try it
The El Niño Story
Pick the one true statement in each set, and the story of an El Niño year builds itself in order.
Try it · interactive
The El Niño Switch
Slide the Pacific trade winds from strong to collapsed and watch the warm water slosh east, the thermocline flatten, upwelling at the Galápagos stall, and the food meter for penguins and marine iguanas drop.
Open the El Niño Switch in its own window (opens in a new tab).
Words you will hear
Four terms, that is all
El Niño
Warm phase: the eastern tropical Pacific heats up
Trade winds
Steady easterly winds blowing across the tropics
Warm pool
Heap of warm water in the western Pacific
Southern Oscillation
Air-pressure seesaw across the tropical Pacific
Check your understanding
Practice the whole chapter
Everything in this chapter, in eight quick questions. Retry as often as you like. Read the feedback on every answer, right or wrong, because that is where the learning is.
Practice
Practice: When the Water Goes Warm
Eight questions covering the video, the three cards, the four terms and the interactive above.
If you want more
Go deeper
- Webb 9.6 — El Niño and La Niña — LibreTexts · 10 minutes
- Oceanography 101 (MiraCosta) 9.11 — El Niño/Southern Oscillation (ENSO) — LibreTexts · 8 minutes
- NOAA PMEL — What is El Niño? — NOAA · diagrams of normal and El Niño years · 5 minutes
Photo credits (Pexels): Lloyd Douglas, Joshuan Barboza, Landiva Weber, Josh Sorenson, Diego F. Parra.