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 growing organisms on earth. In favorable conditions—cold, clear, nutrient-rich waters—it is able to grow up to two feet per day! Unfortunately for kelp, an El Niño event brings strong winter storms and warm, nutrient-poor waters to our coastline. Large waves rip out established plants and unfavorable conditions slow the re-establishment of new canopy. The lack of kelp available during these circumstances cause sea urchins to become aggressive grazers, forcing them to emerge from their safe refuge, creating “urchin fronts” that can quickly wipe out the remaining kelp. These urchins dominate the reef for long periods of time. Reefs where these urchins have taken over are called urchin barrens and our Kelp Restoration Project focuses on removing these to allow new kelp plants to establish and grow.
El Niño’s generally mean a warmer late autumn, but with the prediction of a milder event, the impact it will have on our winter season will be minimal. As of now, the kelp at our restoration sites is flourishing and even survived the sizable swell we received from Hurricane Marie. Water temperatures are slowly dropping and we expect to see an increase in productivity as conditions become more favorable. More precipitation is also expected this winter, which spells good news for California, but it is important to note that it won’t be enough to rid us of the extreme drought we are facing. In light of this, let us remember to be extra water conscious in these coming months. A great way you can help save water and generate awareness is by signing our Dirty Car Pledge!
-Ian Jacobson, Kelp Project Coordinator