From: NASA/Goddard Space Flight Center
Published April 4, 2016 07:46 PM

NASA examines El Nino's impact on ocean's food source

El Niño years can have a big impact on the littlest plants in the ocean, and NASA scientists are studying the relationship between the two.

In El Niño years, huge masses of warm water – equivalent to about half of the volume of the Mediterranean Sea – slosh east across the Pacific Ocean towards South America. While this warm water changes storm systems in the atmosphere, it also has an impact below the ocean’s surface. These impacts, which researchers can visualize with satellite data, can ripple up the food chain to fisheries and the livelihoods of fishermen.

El Niño’s mass of warm water puts a lid on the normal currents of cold, deep water that typically rise to the surface along the equator and off the coast of Chile and Peru, said Stephanie Uz, ocean scientist at Goddard Space Flight Center in Greenbelt, Maryland. In a process called upwelling, those cold waters normally bring up the nutrients that feed the tiny organisms, which form the base of the food chain.

"An El Niño basically stops the normal upwelling," Uz said. "There’s a lot of starvation that happens to the marine food web." These tiny plants, called phytoplankton, are fish food – without them, fish populations drop, and the fishing industries that many coastal regions depend on can collapse.

With NASA satellite data, and ocean color software called SeaDAS, developed at the Ocean Biology Processing Group at Goddard, Uz has been mapping where these important phytoplankton appear. Orbiting instruments like the Moderate Resolution Imaging Spectrometer on the Aqua satellite, and the Visible Infrared Imaging Radiometer Suite on the Suomi NPP satellite collect data on the color of the ocean. From shades of blue and green, scientists can calculate the amount of green chlorophyll – and therefore the amount of phytoplankton present.

The ocean color maps, based on a month’s worth of satellite data, can show that El Niño impact on phytoplankton. In December 2015, at the peak of the current El Niño event, there was more blue – and less green chlorophyll – in the Pacific Ocean off of Peru and Chile, compared to the previous year. Uz and her colleagues are also watching as the El Niño weakens this spring, to see when and where the phytoplankton reappear as the upwelling cold water brings nutrients back to the region.

Continue reading at NASA.

El Nino image via Shutterstock.

 

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