What is El Niño?
An El Niño occurs when the trade winds over the Pacific Ocean weaken or even reverse causing the eastern equatorial Pacific to warm. El Niño is felt across the entire Pacific Ocean, including in California waters, with effects generally peaking near the end of the calendar year.
The term El Nino was coined centuries ago by South American fishermen who observed alarming effects of warm ocean water on their fish catch and sea birds. They named the phenomenon El Niño because of the timing near Christmas. El Niño impacted their food supply and livelyhoods and even today we are similarly impacted by El Niño events in the 21st century.
In normal conditions along the west coast of the Americas, there is strong upwelling that brings cool nutrient-rich water to the surface. This supply of nutrients feeds some of the most productive fisheries in the world. One of the effects of a strong El Niño is to shut down this upwelling with harmful effects on the ecosystems and fisheries.
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El Niño in Southern California
(versus at the Equator)
We noticed strong coupling between ocean temperature at the equator and our glider measurements of the California Current System, so we created the Southern California Temperature Index (SCTI) as a way to easily track the two.
The Oceanic Niño Index (ONI) is a measure of sea surface temperature at the equator that NOAA uses to determine El Niño conditions. Our SCTI is a similar measure of ocean temperature in the Southern California Bight. These indices tell the deviation of ocean temperature from normal for that time of year.Learn more about the SCTI
Southern California's Ocean Temperature Since 2007
The most recent two El Niños peaked in 2009/2010 and 2015/2016, when we saw strong positive anomalies at the equator and off California.
There was also a peak in the Southern California Temperature Index in 2014/2015, at a time when the Oceanic Niño Index was slowly increasing but not yet peaking.
This marine heatwave was called “The Blob” at the time, and was widely reported in the press.
Recent Conditions and Forecasts
At present, we are seeing ocean temperatures at the equator and in the California Current System both increasing rapidly.
Forecasts suggest a 95% chance that an El Niño will occur at the equator this winter. If this forecast proves accurate, we expect to see strong effects in our waters.
Weekly sea surface temperature anomalies (°C) for the past 12 weeks. Anomalies are computed with respect to the 1991-2020 base period weekly means from the adjusted optimal interpolation (OI) climatology (Reynolds and Smith 1995, J. Climate, 8, 1571-1583). Credit: NOAA Climate Prediction Center