Normal conditions in December, 2013 (left) compared to the El Niño in December, 2015 (right). The MODIS instrument on the Aqua satellite has been monitoring the color of the ocean, the chlorophyll concentration, derived from reflected light since 2002 to determine where plant life is photosynthesizing. These images were created using SeaDAS with data derived by the Ocean Biology Processing Group at NASA GSFC.
Notice the area near the equator where there is more blue meaning less chlorophyll during El Niño compared to a normal year. In addition to less phytoplankton blooming and the disruption to the marine food web and reduced fish catch in the east equatorial Pacific, El Niño is linked to unusual weather around the world: more typhoons in the Pacific, fewer hurricanes in the Atlantic, more rain in California, less rain in Southeast Asia and Australia, and warmer weather in South America. The monstrous 1997/98 El Niño led to extreme events with catastrophic consequences. There were floods and landslides in some places and extreme drought in others. The 1997/98 El Niño was followed by the opposite phase, La Niña, that greatly increased productity in the region, as seen here:
NASA Earth Observatory: El Niño disrupts the marine food web
NOAA monthly blog on El Niño
NASA Earth Observatory: El Niño strengthening
NOAA ENSO Diagnostic Discussion
El Niño modelled in a tank
NASA Wavelength: Weather Wrecker - Teaching El Niño