Could Leftover Heat From the Last El Niño Spark A New One?
Some climate models are suggesting that El Niño may return later this year, but for now, the Pacific Ocean lingers in a neutral “La Nada” state, according to climatologist Bill Patzert of NASA’s Jet Propulsion Laboratory, Pasadena, California. The latest map of sea level height data from the U.S./European Jason-3 satellite mission shows most of the ocean at neutral heights (green), except for a bulge of high sea level (red) centered along 20 degrees north latitude in the central and eastern Northern Hemisphere tropics, around Hawaii. This high sea level is caused by warm water.
Whether or not El Niño returns will be determined by a number of factors, one of which is the larger stage on which El Niño and La Niña play, the Pacific Decadal Oscillation (PDO). The PDO is a large-scale, long-term pattern of ocean temperature and other changes in the Pacific Ocean. It alternates between two phases, warm (called positive) and cool (negative), at irregular intervals of 5 to 20 years.
The phases of the PDO are known to affect the size and frequency of the shorter-term El Niño and La Niña events. In its positive phase, the PDO encourages and intensifies El Niños. In its negative phase, it does the same for La Niñas. The last PDO phase shift was in 2014, when it turned strongly positive and has remained that way for 37 months.
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