Data from ocean-observing satellites and other ocean sensors indicate that El Nino conditions appear to be developing in the equatorial Pacific Ocean. Conditions in May 2014 bear some similarities to those of May 1997, a year that brought one of the most potent El Nino events of the 20th century.
During an El Nino, easterly trade winds in the Pacific falter and allow giant waves of warm water – known as Kelvin waves – to drift across from the western Pacific toward South America. Surface waters in the central and eastern Pacific become significantly warmer than normal, altering weather patterns and affecting fisheries along the west coasts of the Americas. El Nino also can have a significant influence on weather and climate far from the tropics.
The height of the sea surface is a good indicator of the amount of heat stored in the water. As the ocean warms, the surface rises; as it cools, its falls. This is due to thermal expansion and contraction; the molecules in warmer water are farther apart than in cooler water. Above-normal sea surface heights in the equatorial Pacific indicate El Nino conditions, while below-normal heights indicate La Nina. (You can see an example of La Nina here and El Nino here.)
“What we are now seeing in the tropical Pacific Ocean looks similar to conditions in early 1997,” said Eric Lindstrom, oceanography program manager at NASA headquarters. “If this continues, we could be looking at a major El Nino this fall. But there are no guarantees.” Observations from a network of sensors within the Pacific Ocean support the satellite view, showing a deep pool of warm water that has been sliding eastward since January.
The years 1997-98 brought El Nino out of the scientific literature and onto the front pages and evening newscasts. It was one of the strongest El Nino events observed, with extreme weather impacts on several continents. North America had one of its warmest and wettest winters on record, particularly in California and Florida. Peru, Mexico, and the rest of Central and South America endured devastating rainstorms and flooding. Indonesia and parts of Asia saw disastrous droughts.
Scientists at the Climate Prediction Center of the National Weather Service (NWS) announced on May 8 that they foresee a 65 percent chance of a transition to El Nino in the summer of 2014. “There remains uncertainty as to exactly when El Nino will develop and an even greater uncertainty as to how strong it may become,” NWS reported.
“If El Nino returns, the American West and Southwest could see major relief next winter from the long-lasting, punishing drought,” said climatologist Bill Patzert, who has been studying El Nino via satellite for two decades from NASA’s Jet Propulsion Laboratory. “Further, the very frigid winter in the upper tier of the U.S this past winter could do a flip to mild next winter.”
References and Related Reading:
- Jet Propulsion Laboratory (2014) Historical El Nino/La Nina Watch. Accessed May 13, 2014.
- NASA Earth Observatory World of Change: El Nino, La Nina, and Rainfall.
- National Weather Service: Climate Prediction Center (2014, May 8) El Nino/Southern Oscillation Diagnostic Discussion. Accessed May 13, 2014.
- NOAA Climate Watch (2014, April 25) Slow slosh of warm water across Pacific hints El Nino is brewing.