Glossary

The Walker circulation (or Walker cell) is an atmospheric system over the equatorial Pacific. It is caused by differences in sea surface temperature between the warmer West Pacific and the equatorial current in the East Pacific, which is fed by the cold Humboldt Current and by cold upwelled equatorial water. While temperatures remain nearly constant in the west, in the east they vary in step with changes in the intensity of the wind systems that produce the cold water. Accordingly, the intensity of the Walker circulation is subject to quasi-periodic oscillations that are directly coupled with the “Southern Oscillation”.