Evolution of El Niño: December 1996 - August 1997

The diagrams below show the evolution of the El Niño event in 1997 as monitored from the oceans. El Niño traditionally refers to the area of warm water off the South American coastline which can warm by between 2°C and 8°C during an event. The first diagram shows a slice through the ocean at the equator - looking from the surface to the depths of the ocean, starting in December 1996, then showing March, June and August 1997. It shows the progression of eastward-travelling pulses of warming from the central to eastern Pacific. This resulted in a warming of the sea surface waters of up to 4°C by August 1997.

Evolution of the vertical equatorial cross-section

The next diagram looks at a horizontal slice across the top of the Pacific ocean, showing sea surface temperatures starting in December 1996, then showing March, June and August 1997. The spread of warm water at the surface evolves very quickly and by August 1997, waters are up to 4°C warmer than normal for a large expanse of the eastern Pacific Ocean.

Evolution of the sea surface temperature anomalies

For more information on El Niño, see also