The Age of El Nino

The phenomena have already been linked to everything from tornadoes in the midwestern United States to fires in Indonesia to hurricanes in Central America. But Earth scientists still have much to learn about how the phenomena affect weather systems around the world. Many questions regarding the root cause and physics behind the two events remain unanswered. Predicting exactly when and with what force El Niño or La Niña will strike continues to be elusive.

To improve our understanding of El Niño, Raghu Murtugudde and a team of researchers at NASA’s Goddard Space Flight Center have been observing algae in the Pacific Ocean. They believe that by watching the algae’s movements during El Niños and La Niñas they can gain insight into the processes that drive these events.

Their initial results show promise. Using the first year of data returned from NASA's new Sea-viewing Wide Field-of-View Sensor (SeaWiFS), the scientists have found a way to detect the end of El Niño and the beginning of La Niña a month earlier than anyone else. In the future, the researchers hope to detect other stages of the phenomenas' development and then create models to predict the events' occurrence and their destructive force years in advance.

El Niño’s Effect on Algae

"Observing [the algae] in the oceans is much like putting dye in a tank and stirring it up to see where things are moving," Murtugudde said. Algae (phytoplankton) are by far the most abundant form of plant life in the ocean. They are sensitive to light, temperature, currents and winds, and their green chlorophyll can be detected by satellite instruments. Because phytoplankton changes an ocean's color, they are ideal candidates for tracking currents, detecting pollution, and observing meteorological events.

For years scientists have known that El Niño and La Niña change the levels of phytoplankton across the entirePacific basin. During a normal year, winds gust at a steady rate from east to west across the Pacific and slowly blow the warm surface waters towards Australia and the Indonesian Archipelago. Over a period of time, these winds build up a "warm pool" of water in the western Pacific and leave the eastern Pacific relatively cool. This layer of warm water smothers any upwelling currents, which bring cool, nutrient-rich waters up from the depths of the sea (Njoku et al. 1993). Since phytoplankton can only survive in these nutrient-filled waters, the plants do not usually do well in the western Pacific and thrive in the eastern and central Pacific (Murtugudde et al. 1999).