The tropical ocean off the west coast of South America is notable for several reasons. First, it is unusually cool for an ocean that is so close to the equator with sea surface temperatures at 5 S off Peru as cool as 16 C when most other tropical locations are in excess of 25 C. Upwelling of cool waters brings phytoplankton nutrients to the surface, dramatically increasing biological productivity in this low-latitude region of few storms. S