El Niño
An LA Waterkeeper Blog
Predicting the next El Niño is tricky business. Recently, the likelihood of an El
Nino event occurring this winter has been reduced down to 58%. Forecasts still
expect a mild event to occur, but what does that mean for Southern California and
our local Kelp Forests?
An El Niño Southern Oscillation (ENSO) event occurs when a
shift in the surface air pressure between the eastern and western
halves of the Pacific causes the easterly trade winds to weaken.
This allows warmer waters to move west, replacing the normally
cold surface waters along the equator and the Pacific coast of South
America. In the Northern Hemisphere, the California Current—
which transports cold water from the north—slows down and our
coastal waters warm. This warm water affects the productivity of
our coastal ecosystems by reducing the frequency of upwelling
events and preventing the transport of colder nutrient rich water to
the surface. In a strong event, California sees unusually high rainfall and larger winter swells, but this year isn’t shaping up to what
early predictors foretold.
Experts believe this is to be due to a much broader band of the
Pacific Ocean that is warmer than normal. This weakens the pressure gradient in the Pacific that triggers the shift in the trade winds.
Every ENSO event is different and the likelihood for one to occur
changes on a 10-year or longer scale called the Pacific Decadal
Oscillation. During these oscillations, we can see a pattern of weak El Niño events
followed by weak La Niña events but during the next decade have a series of strong
irregular events. Even with today’s technology, the patterns of these oscillations
cannot be accurately predicted.
In Southern California, we are still seeing unusually warm water along our coastline for this time of year. Local water temperatures have stayed in the low 70’s
through late October but have recently cooled down to 68° in Santa Monica. On
our last Kelp Project dive, we experienced 64° water at our restoration site in Palos
Verdes. Kelp forests share a special relationship to El Niño’s and are particularly at
risk during strong events. The giant kelp, Macrocystis pyrifera, is one of the fastest