El Nino Watch
Satellite estimate of chlorophyll in the sea surface, a sign of plankton. El Nino cuts the cold, nutrient-rich upwelling off Peru, so chlorophyll drops there.
Map layers
Phytoplankton are microscopic plants that colour the water green. More chlorophyll = more plankton = more food for fish.
Off Peru, cold deep water normally rises to the surface and fertilises the sea. During El Nino the Thermocline deepens, that upwelling weakens, and the plankton (and the fishery) collapses.
Blue/purple = low chlorophyll (clear, poor water); green/yellow/red = high chlorophyll. Clouds leave gaps.